The tuning chapter...
 

Figured I would just go ahead and move the latest work done on my car into a separate thread, since most of it has to do with tuning lately. I may go back and fill in stuff that was done earlier so I have a record of what I have fiddled with in case I need to refer back to it.

Anyway, the latest, first....

Did another data logging run yesterday. I've noticed that the short term fuel trims were fluctuating quite a bit, so I wanted to disable closed loop mode to see what was going on.



Car ran really well in open loop, but seems to be running a bit rich in most areas of the VE map. I disabled the fuel modifiers last night and will do another run today or tomorrow to see if that helps lean it up a bit before modifying the VE (volumetric efficiency - B0101) table.

Sounds like it's running just fine to me!

Yeah, it does sound pretty good!

What probably isn't evident from the video is that when the car is accelerating, I'm actually holding the gas pedal relatively steady, trying to get enough data points in each RPM cell. It's actually the turbos spooling up that are making the car go faster. The MAX I had the throttle was 42.7 percent, but rpm climbed pretty quickly to 5252. Something tells me that I'll be hitting redline REAL FAST when I actually try 100 percent throttle one of these days.

Did you retain the factory traction control? Or have a rev limiter programmed?

Yeah, they both are still in the programming as best I can determine.

The rev limiter is set for 6900 rpm.

One puzzle I'm still trying to get an answer for is that EFILive shows a max value for engine torque of 640 ft.lbs. I'm sure my engine is producing significantly more than that at the crank, so I'm not sure what, if anything, the PCM does at that point when that value is exceeded. The PCM uses two methods to try to reduce power when it wants to. One is via reducing the timing advance, and the other via fuel cut off. If you've ever had a situation where you get REDUCED ENGINE POWER, you will likely have noticed that your gas pedal is effectively useless.

And I did not disengage traction control while driving the car doing these runs, but I didn't notice the engine losing power if traction control kicked in. Actually a couple of times it did feel like the rear tires broke loose under boost, though....

Yes, the traction control has a very generous limit on my CTS V also. I don't know what the perameters are but it will let the wheels spin quite freely. Only when I get really sideways does the gas pedal go away. Mine has the traction control and the stabil-trak, so if you get crossed up on a curve it will "brake" you out of it. Pretty amazing actually(not that I've used it alot:rolleyes:) but these roundabouts up here can be a lot of fun! My car has a "competition mode" that shuts down both traction control and the stabil-trak systems. Part of that system encompasses the tire pressure sensors, and if one or more tires is low, or if the tps batteries are dead it won't let it go into competition mode. My rear tps sensors are dead so I can't get it into competiton mode. Probably a good thing.....:yesnod:

Yes, the C5 has pretty much the same thing. There are four states available when I click the button on the console that controls traction control and active handling.

1. Both traction control and active handling ON
2. Traction control ON, active handling OFF
3. Traction control OFF, active handling ON
4. Both traction control and active handling OFF

I can't remember which button press sequence does what right at the moment. Honestly, I haven't used that feature since before I took my car into Chris Harwood's shop. But the one I used most often was option 3. I don't mind the rear tires spinning, but not so keen on going sideways at the same time. I think this car would be easy to get away from me without some sort of nanny guards in place. :hehehe:

Anyway, I took the car out for another run today and did some more data logging. Results are inconclusive, I think. Some cells in my map display are showing leaner than before, but others are showing richer. So I'm not exactly sure those supposed fuel modifiers were really doing anything to the AFR.

I need to bone up on that volumetric efficiency table anyway, as it really doesn't seem intuitive to me at all just trying to figure it out on my own. It's supposed to be a representation of the relative efficiency of the engine's ability to fill the cylinders with air. It is used to predict the volume of air entering each cylinder under varying conditions. That's pretty much a direct quote from EFILive. But how it actually WORKS isn't very clear to me.

Some of the problem is that there are three ways of looking at the air fuel ratio in EFILive.

1. AFR (air/fuel ratio, ei: 14.7:1 means 14.7 parts of air to 1 part of fuel)
2. lambda (1.00 is stoichiometric. 0.98 would be richer, 1.02 would be leaner)
3. EQ ratio (1.00 is stoichiometric. 0.98 would be leaner, 1.02 would be richer)

From what I understand, the GM PCM uses EQ ratio natively for it's internal calculations.

I think you can see where confusing lambda with EQ ratio will have the opposite effect you are striving for. So the problem I have is figuring out whether the map function I am viewing is using a lambda or EQ ratio equivalency when applied to the VE table. Since the VE table is NOT in any sort of AFR units, just some sort of relative value concerning "efficiency", I'm just not sure if making the values smaller in the VE table makes the FINAL AFR leaner or richer. What does it mean if the cylinder is made to appear LESS efficient by lowering the number? It's little details like this that are not self evident but can have a BIG difference in reaching your goals with this tuning stuff.

AFR seems so much more intuitive to me, but to really get into this tuning stuff, you have to abandon that way of looking at the air/fuel mixture. And of course, there is no real consensus on whether working with lambda is better or worse than working with EQ ratio, so some tutorials and help pages will use one, and others use the other. Then you combine this with some tutorials using metric values, and others use SAE, and you REALLY have to keep your eyes on the ball to make sure you are putting apples in the apple bin, and oranges in the orange bin. :notallthere:

Well, I think I've got a better handle on this VE table now. First off, here's what a VE table (B0101) might look like in EFILive..

http://www.corvetteflorida.com/pics/ve_table_02.jpg

The values in each cell are a representation of how much air is PREDICTED to be able to fill the engine cylinders at the intersection of the manifold vacuum/pressure and the rpm of the engine, as shown in that table matrix. The PCM uses that value to determine how much fuel to inject into the cylinders when the engine is actually at the rpm level that corresponds with the intake manifold vacuum/pressure. This is pretty much the basis of what's known as a SPEED DENSITY tune.

What a MAP file is, therefore, is just a representation of the VE Table set up in the scan tool, set up to capture the DIFFERENCE between the commanded AFR and the actual AFR as determined by the wide band controller in the exhaust. This is done via a calculated PID that generates these values on the fly while the scan tool is capturing data. What this map file then represents is a correction factor for each cell of the VE table that sufficient data has been captured during a data logging run. That MAP file will look something like this:

http://www.corvetteflorida.com/pics/ve_table_01.jpg

The values shown in the above are AVERAGE values of each cell with data in them. Cells that have had hits between zero and ten(10) are excluded from the MAP display so that the average value is more realistic of the actual differential.

So, now with that information captured in the MAP, what EFILive allows you to do is to cut those values in the MAP display from the scan tool, and then paste those values into the VE Table in the tune tool and at the same time also MULTIPLY those map cell values to the cell values in the VE table. This CORRECTS the values in the corresponding cells of the VE Table based on the difference determined in the MAP data. The values less than one (1) will therefore reduce the cell values in the VE Table cells, which will make that cell command a leaner value. Cells in the MAP that are greater than one (1) will increase the value of the VE Table cells, which will command the AFR to be richer. So a smaller value tells the PCM to expect LESS air and therefore inject LESS fuel into the cylinders. A larger cell value does the opposite, telling the PCM to expect MORE air in the cylinders, and therefore inject MORE fuel to compensate accordingly.

So increasing the numbers in the VE Table indicate a richer AFR, and decreasing those numbers indicate a leaner AFR. So this cut and paste of the MAP display values is a very quick and easy way to do what used to be manually capturing data from such cells, figuring out the percentage of difference needed, richer or leaner, and then manually multiplying EACH CELL in the VE Table by that percentage of difference. Yeah, I'll bet THAT was tedious!

Of course, the issue is trying to get enough "hits" in each cell of that MAP display to cover the entire VE Table. Which is why this sort of thing is certainly much easier to do on a dyno where you can control the RPM of the engine and the loading (on a load bearing dyno) of the engine in order to capture ALL the cells needed for a complete VE Table correction. Unfortunately, I have to do this the hard way on the street, which means I most likely will not be able to capture all the cells at the higher RPM range, under all vacuum/boost conditions.

Whew! That had me scratching my head for a while, but I think I understand it now....

SEE! I told you..............another career is just around the corner! :D
You're getting it all worked out, and will be able to put out the "Tuning
by Rich" sign soon!:yesnod:
Andy :wavey:

Nope, not going to happen. :nonod:

I'll quite likely learn how to tune MY car, but that doesn't mean I will be able to tune anyone else's. Mine is so far from stock that likely everything I am learning won't apply to any other cars anyway. Besides, in the area I am located, someone specializing in tuning Corvettes would quickly starve to death. If I wanted to do this as a business, I would be learning how to tune pickup trucks.

:lmao::lmao::lmao::lmao::lmao:
Andy :wavey:

Been doing a lot of reading about tuning, particularly idle tuning and the issues related to getting a *good* stable idle. Every now and again someone brings up the idea of drilling a hole in the throttle body blade to try to resolve some idle issues.

Found an interesting quote that I wish I had known about a long while back in reference to cars with electronic throttle control (like mine). Not that I knew about the hole in the throttle body blade myself until I actually pulled off the throttle body, though.... :banghead:

Source: http://www.hptuners.com/forum/showth...e-tuning/page3

:yesnod:

It should read, "You will need to drill a small hole in the center of the throttle plate to compensate for my lack of skills as a tuner.....".

Hah! Not to mention that the brass colored throttle plate throttle body isn't compatible with my engine management system anyway, and a supposed Corvette "expert" wasn't aware of that fact.

Mike Carnahan sent me a new tune to do some data collection off of, and asked me to put it into boost a couple of times so he could look at the data. I went into boost in third gear the first time, and then from fourth gear. I also let the car engine brake so I could get some data in those cells with higher RPMs but with vacuum in the manifold.

I think I hear the waste gates in the first run, but not sure. The MAP value is showing that I'm only at 144 kPa which should be only 6.2 psi of boost. There are supposed to be 10 lb springs in those waste gates.... :thinkin:

This was the first time I've taken the car to 100 percent throttle.

Seat of the pants impression was that the car seems to pull a LOT stronger in fourth gear than third gear. Maybe just my imagination.

BOY........does THAT sound NICE!
I can only imagine (and be envious of) what that must feel like when you plant your foot!
Lotta time, money, and head (heart) aches have gone into that car thus far,
and it seems like you're almost there! I applaud your perseverance! :thumbsup:
Should be one ballsy beast when it's finished.
Andy :wavey:

Thanks!

Yeah, it's coming along pretty well. I noticed that Mike Carnahan didn't just discard my own tuning fumblings in the tunes he is sending me, so apparently I wasn't too far off the beam with what I was trying to do. I've still got that minor cold start instability to get rid of, and the engine is tough to restart if it stalls while still cold. But these are really minor things. If I wasn't such a pain in the ass perfectionist about this, I would just pull the wideband out and just have fun driving the car.

I got a new tune from Mike this morning, but haven't looked at it yet. Finally getting some rain here, so probably won't be driving the car today anyway. Even if it stops raining here, I would have to look at the weather radar and plot a course to try to avoid wet roads from the popcorn style storms popping up all around me. One thing I definitely don't want to do is to kick the gas pedal on a wet road! :ack2:

That might prove to be ONE INTERESTING RIDE! :eek:
I would be content to just see the video of that one.....:D
I would also like to see a video of how well it does in the snow...:lmao:
Andy :wavey:

Unless there are some severe changes in the Florida weather patterns, you will NEVER see me stepping foot or setting tire treads in snow. :hehehe: I fully intend to die with never having had another snow flake land on me or my cars.

You've been VERY consistent about that, and I'm beginning to catch up to you.
Wasn't bad 40 years ago when there were less cars on the road, and
the people that were here then KNEW HOW TO DRIVE THEM! Lately, all of the
people that come here from other countries where there is no snow, are driving
me insane with their inability to navigate on the roads for 6 months out of the
year. I think that I will enjoy being in Florida in the winter, even with having
to put up with the "snow-ld birds". :rofl1:
Andy :wavey:

Well, I've pretty much got the VE table dialed in and the air/fuel ratio is spot on. If I wanted to run the car in purely speed density/open loop mode, I think it would run just fine. But while I am tinkering with this stuff, I want to look at the other options to see if maybe other modes would be better.

For instance, right now I have the MAF completely disabled as well as the fuel trims. My next step will be to re-enable the MAF and do some logging to calibrate the air flow through it. This is done by comparing the commanded fuel with the actual AFR detected by the wideband O2 sensor, and then apply the differences to the MAF table (B5001). This is basically just a single column curve table that provides a lookup of the frequency emitted by the MAF sensor and provides a value of the air movement past it that the PCM uses to determine how much air is going to be filling the cylinders so it can command a correct fuel charge via the fuel injector pulses. So this table has to be correct for the fuel charge to be correct, and consequently will show up in the AFR value detected by the wideband.

I'm thinking that if it runs well on the MAF, I could set it so that the MAF fails at the frequency where the table no longer provides any lookup data. Which is 12000Hz. I know I've seen values higher than that when logging data while in boost, so I'm thinking that if I fail the MAF at 12000Hz, then the fuel tables of the VE table will then take over exclusively, giving me (hopefully) the best combo of MAF tuning and speed density tuning. This is all theory, of course, so it will really depend on how the car FEELS when I drive it. That will ultimately make the decision for me, no matter what the data logging shows.

Then there is the matter of the fuel trims. While tuning the VE table, I had all fuel trims disabled, which is what you want when trying to determine the AFR of each cell in the VE table (B0101). This is a two dimensional table that provides cell intersections based on engine rpm and vacuum/boost as detected by the MAP sensor. But this is pretty much a static snapshot of HERE and NOW when tuning a car in speed density/open loop. And changes in atmospheric conditions will have an effect on this tuning, but how much is subject to debate. I doubt I will ever take that car out to the mountains, and if a huge low pressure cell moves in, I assume hurricane force winds and rain will also possibly be accompanying that cell, so not likely I would take the car our for a spin. But the positive side is that if I have to use ethanol laced gasoline instead of the stuff I'm able to get at the local Sunoco station, then the optimum AFR will change with the different fuel. Fuel trims will compensate for that to keep the engine from running too rich or too lean.

So once the decision is made whether to use the MAF or not, I will then re-enable first the short term fuel trims so see how it runs, then re-enable the long term fuel trims as well.

Of course, I'm now just twiddling my thumbs while thunderstorms whirl all around this area. Not really getting a lot of rain right HERE at the house, but all the roads around me appear to be getting rain if the weather radar is accurate.

So I'm close to wrapping up the major portions of the tuning. There are other things I'm sure I'll be pecking away at for a while longer, though. Things like the decelerator fuel cut off settings, sharpening up throttle response, and certainly trying to get rid of that initial startup stumble when I blip the accelerator. But I'm confident that everything can be fixed that I see on my plate IF I know which tables to adjust and figure out exactly HOW they need to be adjusted.

Yeah, I've learned a LOT about this tuning stuff. Still a lot more to go, but it doesn't feel as mind bending as it did when I first started looking into it. Of course, it pays to keep in mind that the tuning programs we use are not perfect neither. Bear in mind that those guys (EFILive, HPTuners, etc) are simply trying to reverse engineer the PCM in our cars by looking at the raw code and data trying to figure out what the heck it is doing. Some of the program code is really nothing more than guesswork. This is more voodoo than it is science.

So in effect, don't make your expectations unrealistic. As Mike Carnahan told me, my car is about the worst possible case I could have chosen to learn to tune with. Nothing can be taken for granted since everything has been changed mechanically. So nearly all of the tables in the PCM for a stock car no longer apply to MY engine and will have to possibly be tweaked. But as for being a perfect fast track course to learn a LOT about tuning, there probably couldn't have been a better test bed for me to play with. I HAVE to look at everything and try to understand what it all really means to me. Which, quite honestly, was extremely frustrating and overwhelming when I jumped into this.

Well, this sure sounded good in theory. :rolleyes:

Been spending time calibrating the MAF and getting the car feeling REALLY good using it. So I'm thinking this is going to be a piece of cake, have the car running mostly from the MAF for air/fuel calibrations, and then when in boost and the MAF runs out of road at 12,000hz, have it flip over to using the VE tables during boost. Basically trying to get the best of both worlds.

Well one small problem with that. Once you fail the MAF, it STAYS failed till you shut the engine management system down. It doesn't get re-enabled again when you drop back out of boost and into the zone that the MAF is comfortable in.

So that pretty much makes it pretty cut and dried for me. I have to go with a Speed Density tune for my car since the MAF cannot handle the airflow that boost from the turbos provides. So all of the tunes and logs I did with the MAF enabled have been just a waste of time. Well, except I did learn some things along the way, of course.

But I could have been a LOT closer to wrapping up this tuning stuff if I hadn't chased this idea down that dead end alley.

Ah well, been getting some rain lately anyway. And looks like more the next few days. So that will give me time to figure out which tune was the last one I did running solely off of the VE tables and I can roll back to that one and figure out where to go with it after another logging run to see where I am at. I don't think I did much with the upper RPM range figuring I would concentrate only on the areas that overlapped with the MAF range and then deal with the boost areas of the VE tables when I had the low and midrange running well.

Heck, I'm going to wear out this new engine just working on the tuning. :ack2:

Some of the guys over on the EFILive forum are giving me pointers on what appears to be the best way to set up a completely Speed Density tune on my car, since my plan of using the MAF got shot down. One of the guys seems quite familiar with working with boosted engines and said that my fueling was a bit too rich right before going into boost, so it would likely bog down under the right conditions. The only time I experienced anything like that was in high gear at low rpms but I just wrote that off as being the nature of the beast. But it might very well explain the soft throttle response I've noticed at low rpms as well.

Apparently I was also looking at the Power Enrichment tables incorrectly as well. Back in the old days, there used to be a device on carburetors called the accelerator pump. This was used to provide a squirt of raw gasoline into the carburetor upon pressure of the gas pedal being applied. This helped to keep the opening carburetor plate from causing a lean spike which could cause a flat response in acceleration. I assumed that the Power Enrichment tables were the electronic equivalent of this manual accelerator pump of old. Apparently this is not the case. It is simply a method of applying a richer AFR mixture when commanded depending on throttle position. Kind of sounds like the same thing to me, but apparently it is different enough to have thrown me off with what I was trying to do.

What was suggested to me was to simply use the Commanded Fuel vs RPM (Normal) table {B3647} for naturally aspirated fueling, commanding stoich from 20 to 80 kPa, and then from 85 to 100 kPa gradually make the fueling slightly richer (.96 to .86 Lambda). When boost begins to kick in at 105 kPa set up Power Enrichment to enable at 110 kPa using the PE MAP threshold switch {B3613}, and then control PE fueling via the table for PE Modifier Based on RPM {B3618}.

So that's what I have in the new tune that I'm waiting to try out when weather permits.

He also said that the way my timing is being implemented is not optimal neither. It is marginally OK, but using strictly the high octane table doesn't fully compensate for the needs when boost kicks in. Apparently there is also a separate timing table that is best utilized on a boosted engine instead of trying to do this solely with the standard timing tables. So when we get the fueling ironed out, he will help me get the timing optimized.

But, of course, the weather is getting in the way. The drought seems to be over with now, and we've been getting rain every day, but in patches. I'm watching the radar constantly, and even if I'm not getting raid directly overhead, there will be rain all around me. Which, of course, means I can't take the car out. I need to run the rpms up to do adequate data logging all across the rpm spectrum, but I certainly don't want to be putting a lot of power to the rear wheels on wet roads. Heck, I just now walked out to the garage to put the latest tune in, and the sun was shining and the sky looked pretty clear, even though the radar showed rain to the south. I loaded in the tune, and then came out of the garage to feel it starting to rain.

Oh well.... It's that time of year, I guess.

Well, went ahead and put the battery trickle charger on, since it doesn't look like I'm going to be able to take the car out anytime soon with all the rain we are getting. One drive down out road and I'd be scraping mud from the underside of the car for days afterwards.

Actually saw the sun for a short bit yesterday (Friday), so I loaded up the latest tune and took the car out for a short run to try to get some data logging done. Changed the fueling tables for NA and boost, so I tried to get some boost cells filled with data. Unfortunately I used the wrong PID file, so it was sampling at a slower rate than I wanted. But at least it did capture some data.



Yeah, I chickened out holding it at 100 percent throttle going around that bend. :blush:

And that stop sign was coming up a LOT quicker than it seems in the video.

I decided I probably should recalibrate the wideband sensor, since I hadn't done that since I originally installed it back in December. Figured that since I'm trying to finish up the calibration of the VE tables, I should make sure the fueling feedback is accurate. All it takes is pressing the calibrate button on the wideband harness for three seconds to recalibrate the sensor. I never did find a satisfactory answer as to whether the sensor can be recalibrated while still in the exhaust pipe if the car sets for a couple of days, so I pulled it out and let it hang in free air when I did the recalibration. No real big deal, but kind of a pain in the butt just to get to the point where I can press that recalibrate button for three seconds.

So, I took the car out again today (Sunday) to get some more logging done. The rains bypassed us today, so the roads were dry and it didn't look like I would get caught in an unexpected downpour. I needed to get some more cells populated in the boost VE table, so the opportunity presented itself when I "needed" to pass a slow moving truck pulling a trailer. The road was wide open in front of him, so I just let it wind out a bit to get the data I was needing anyway.

So I'm looking over the log display, to see how things look, and the spot where I kicked it into boost is kind of interesting, if I'm interpreting things correctly.

http://www.corvetteflorida.com/pics/log_07072013a.jpg

First off, "boost" is the condition whereby pressure detected by the MAP sensor in the intake manifold is greater than ambient barometric (atmospheric) pressure. Barometric pressure at sea level is normally 101.3 kPa, 1013 millibars, 29.913 hg, or 14.692 psi, depending on what sort or yardstick you like to use. I did the screen capture above with the indicator on 103 kPa, which is pretty much the beginning of boost kicking in. I was surprised to see that the engine speed was less than 2600 rpm.

BTW, while I am thinking of it, if you ever have a need to swap out your 1 bar MAP sensor with a 2 bar (or higher) sensor, you need to calibrate your new sensor to ambient barometric pressure. Mine is off slightly, because I didn't know to do that when I swapped out mine. But it's showing 101.0 kPa with the engine off, so I don't think it will make much difference being off such a small amount. EFILive has a MAP sensor scaler table {C6301} that you use to dial in the calibration of the replacement sensor.

Also of note is that the boost seems to peak at 156 kPa (around 8 psi), and then drop very slightly, even though engine speed is increasing. There are 10 lb springs in the wastegates, so perhaps 2 lbs are just being lost because of plumbing overhead. It's hard to tell from that pic, but boost goes from 103 kPa to 156 kPa in just under 3 seconds.

The MAF is indicating constantly increasing airflow (MAFFREQ Hz) even past where the boost plateaus, so this is indicating to me that the engine isn't being starved for air with the turbos just not able to keep up. There was some concern that this might happen with the larger cubed 427. I guess I'm going to have to get one of those GoPro cameras one of these days so I can actually watch the wastegates opening up.

But I'm thinking that I could probably go with stiffer springs in those wastegates to raise that boost level a little bit. Those 10 lb springs do seem to top out pretty darn quickly.

Vehicle speed seems to be keeping a 1:1 ratio compared to engine speed, so I'm taking this as a good sign that the clutch isn't slipping, and the engine is pulling hard up till the moment I take my foot off the gas pedal at 5400 rpm. But I definitely can FEEL where the boost hits that plateau at 8 psi and holds there.

AFR is looking pretty good, and there were no knock retards indicated during the entire run, so the timing is apparently OK.

I figure I don't need very many more runs for data logging before I have the fueling where it needs to be via the two VE tables. Once that is straightened away, I'm going to re-enable the fuel trims and just see whether the car drives better with or without them. There is still some slight surging a low rpms when I take my foot off the gas pedal at slower cruising speeds in higher gears.

Been looking at the Hero3 Go Pro cameras myself, Rich! They look like a nice little unit
that seems to have ALL SORTS of applications! :thumbsup: I was thinking about
using one to document my "later mid life crisis" crazy moments, but I'm not quite sure
I want to show how crazy I am to others! :rofl1: I would be VERY interested to
hear what you think of them should you get one. It also sounds like you're
creeping up on the tune that you want for the C5Z, and I hope you get there
sooner than later. You seem to be picking up on a lot of information, as well as
being able to digest it and know what to do with it! The WHOLE saga of the
C5Z has been an interesting read, and at times I was really able to feel your
frustration. Hopefully, those days are behind you, and the end of the story is in
sight. Cummon and give us the REAL truth.........! You REALLY don't like to do
those "data logging" runs, do you? :lmao::lmao:
Andy :wavey:

Honestly, it was fun at the beginning, giving me a good excuse to take the car out and get "frisky" with it, but it's beginning to get old now. I don't normally drive that way. And I know the more times I do it the more I am pressing my luck of whizzing by a random cop encounter and getting in all sorts of trouble. I pick remote areas, where there is very little traffic, but still, there's no predicting just plain old bad luck. I seriously doubt my excuse of doing data logging will convince a cop that it is OK. Having a radar detector would be of no use to me, because with the noise the car makes and just seeing a blue streak going by would leave no doubt that I was exceeding the speed limit. So yeah, the sooner I can wrap this up the better. After all that I went through, I really don't want to have this end with my car getting impounded.

I tried winding the engine out in first and second gears to keep my overall speed down, but that just doesn't seem to kick the turbos into boost as well as the higher gears.

Honestly, I'm ready to be at the point where I can pull the wideband and wiring out of the car and just DRIVE it to enjoy it. Not to mention that pressing down on that gas pedal in third and fourth gear gets me pretty white knuckled. I'm not exactly saying it's real scary, but it certainly commands your undivided attention to the road in front of you and being sensitive to the feel of the car to make sure you don't start going squirrelly. Plus I'm still staying attuned to any strange noises (which thankfully have been absent) in case there are still one or more problems still lurking that I haven't found yet. I don't think there are, but heck, you just never know.

Hit a slight snag the other day.

I had the car out on Wednesday doing some more logging and when I had it in some low level boost trying to get some map cells populated, I noticed a, well, engine "burp" is about the best way to describe it. Never had that before, so it did kind of unnerve me a bit. I thought, "NOW what?" But the car got me back home OK. I actually did another tune and took the car out again, but didn't go into boost, and the car drove OK, but seemed rather rough at idle. And the timing looks a bit squirrelly too. Backing up a little bit, when I loaded that tune (#0027) I was pulling off of the garage apron and noticed that the oil pressure gauge was reading ZERO. Yeah, THAT caught my attention! But then I noticed that all of the gauges were dead. So I pulled back onto the apron and found out that I couldn't get the EFILive box to talk to my PCM. Sheesh.... So I just shut everything down, disconnected the V2 cable and rebooted the PC, and luckily I could then talk to the PCM again. But odd thing is that the gauges wouldn't come back until I reloaded that same tune again. :shrug01:

But the car seemed to run OK after I took it out again, but I didn't run it up into boost at all, which is probably a good thing.

Later on in the evening, I was looking over the log for that run where I had the hiccup, and I noticed something odd right where the hiccup should have been in the log.

http://www.corvetteflorida.com/pics/...7172013_01.jpg

Looked like timing advance just gave up and dropped to zero. This appeared to correspond ALMOST with a bump in the engine rpm trace, but not exactly. It seems to lead it a bit. The drop in advance seemed to line up with a slight rise in RPM, and then it dropped down. Then I noticed that the boost reading from the MAP sensor dropped like a rock right after that dip in spark advance. The more I thought about it the more it seemed likely that I had a boost pressure leak suddenly show up. But it is kind of a puzzle why the timing advance drop seemed to precede the boost drop out.

So today (Thursday) I popped the hood and started poking around. First thing I noticed was that it appeared that the airbridge had been rubbing on the underside of the hood again. Then I noticed something was different about the airbridge plumbing.

Here's a pic of the airbridge plumbing right after I got it put together.
http://www.corvetteflorida.com/pics/...dge_new_03.jpg

And here we have what I noticed today.
http://www.corvetteflorida.com/pics/...7172013_02.jpg

That gap showing the aluminum tube between the two clamps was completely gone. And the bottom of the airbridge had come loose completely of the MAF sensor housing.

http://www.corvetteflorida.com/pics/...7172013_03.jpg

Sigh......

So I've got the airbridge and MAF sensor pulled out of there now. One thing I did find out is that the reducing coupler between the throttle body and the aluminum tube going to the air bridge is really not rated for boost. Summit's website didn't indicate that and I only found out by going to other sites trying to figure out what the thickness and number of plies are in that coupler. Apparently there are NO plies and it is just simply a single ply of rather flexible silicon. I thought it seemed rather soft when I installed it, and my guess is that it is way TOO soft and it was possibly ballooning out under pressure, pulling on the airbridge. But how that aluminum tube got sucked further into that coupler kind of has me baffled.

And this might even explain why I wasn't able to get over 8 lbs of boost out of those 10 lb wastegate springs.

In any event, I've got a new coupler on order that is supposed to be designed for boost conditions, so I guess the car is dead in the water for a bit waiting for that part to show up. In the meantime I'm going to cut away that part of the MAF housing that is supposed to fit into a notch on a coupler or airbridge so that the airbridge fits more snuggly on that end. I was actually looking for an aluminum MAF body, but couldn't find anything that looked like it would be an easy replacement. I'm not sure if that plastic MAF housing is getting too pliable when it gets hot, and therefore allowing the lower part of the airbridge to slip off of it. Anyway, all of the aftermarket stuff I looked at was either too long, or too wide, or both, which would mean too much fabrication to get it all back in place. So I'll just have to see if what I monkey around with when the new coupler comes in holds up well enough or not.

Yesterday I took the BBK aluminum airbridge out of the storage cabinet and tried again to get that to fit on the car. I was figuring I could eliminate the MAF sensor housing completely and just use a separate IAT sensor. That would give me more room to work with. But the angle of the airbridge is the snag. It pretty much will just go in one place and one place only to align with both the throttle body and the outlet pipe of the intercooler. And where that spot is is directly above the radiator. Which puts it pressing right up against the hood when I close it. I guess the height of this 427 is higher than the stock LS6 and the larger throttle body raised the center line of the throttle body opening too. So both of those changes conspired to make the airbridge just sit too high.

Ideally I should run four inch diameter aluminum or stainless steel tubing from the intercooler to the throttle body, but no way a four inch pipe is going to be able to run between the hood and the radiator support. I would need to either flatten a section of the tubing like an airbridge, or I would have to find a hood that would allow 4 inches of clearance where I need it.

I have read accounts of people cutting and rewelding their radiator cradle to make the piping fit, but that's going beyond my pay grade. Plus they apparently didn't have an intercooler like mine to deal with, so that would throw a whole nother set of wrinkles into it.

Supposedly DeWitts makes a shorter radiator but so far I haven't been able to find out much about it. What hints I have seen seemed to indicate that you still need to drop the radiator cradle a bit to use 4 inch pipe.

So unless I get hit with a miracle of an inspiration, I don't see any alternative to sticking with that plastic airbridge I now have. I guess I just have to check it frequently to make sure it's not working loose from the heat cycles making the plastic go soft and pliable. I will be extremely surprised if the airbridge doesn't just pop apart eventually. If I were smart I would figure out some sort of screen to put on the front of the throttle body to catch any plastic fragments when that happens. But I'm guessing that would be a whole nother level of "pain in the ass" to fabricate.

I got the new coupler I've been waiting on, but I've just been holding off working on the car while thinking about other options. Plus it's just been crappy weather around here anyway, so not like I'm going to take the car out anytime soon anyway. Incentive has been lacking, I suppose.

Oh yeah, I also found out that the Sunoco I was getting my non-ethanol gasoline from apparently dropped the 93 octane and offers 91 octane instead. So I guess I might as well just go with the ethanol contaminated crap and complete the AFR tuning using that. Probably needed to do that anyway. Tuning for non-ethanol gasoline and using ethanol gasoline will have the engine running too lean. So I guess it's better to tune for ethanol and have it run slightly richer with non ethanol gas than the reverse.

I'd heard from someone else that the Sunoco on Woodville Highway dropped the 93. I'm told he does have 112 race gas though.....:rolleyes:

use hairspray on the silicon connections with the T-bolt clamps and they won't pop off. Diesel guys use that trick as it lubes the silicon connectors to east installation and dries and acts as an adhesive. I've had my boost up to 52psi and blown the couplers off the intercooler multiple times until I used hairspray. once I get my compounds plumbed and all, each connection will be connected using hairspray and I expect to see 75-80psi with that setup

Yes, I remember you telling me that a while back. My concern is that the hairspray may set too quickly, though. I have to fiddle with the airbridge and couplers to get it lined up properly, and that sometimes takes a few minutes to get it right. So how much time do I have, or is that dependent on the brand of hairspray I steal from Connie? Some of the stuff she has is pretty potent stuff!

I don't think I need to be using the 112 octane stuff. Besides, I'm hoping I will be able to trust the car enough to take it on longer drives eventually. So in that case I will have to be using the ethanol contaminated gasoline. After giving it some thought, it's just going to be better off if I complete the tuning using the crap gasoline. If I do find some non-ethanol gasoline here and there, it won't be as bad a deal using it now and again.

Whatever happened with the rumor going around that Florida was going to block the federal requirement that gas stations MUST only offer the ethanol gasoline?

I understand that the Governor has removed the mandate, but it's up to the individual stations as to what they'll carry. Hopefully they'll figure out that the consumers want ethanol-free gas. But I'm concerned that they will keep buying the crap gas just because it cost them less.

Yeah, I hear that. Most times money is the only thing some people pay any attention to. I guess if more people were willing to pay the premium for quality we wouldn't be owned by China right now.

Anyway, Connie and I spent a couple of hours over in the garage putting the airbridge back on. I took off the notch on the MAF housing so the airbridge fits better on it, and used the firmer 4 to 3.5 inch coupler between the throttle body and the aluminum pipe I put into the north end of the airbridge. The ways I thought would be easier to put that all back in didn't work out like I had hoped. There is ONLY one way it will go back together that I can figure out, and even that was a bit of a struggle. But it's together. If the rains ever let up, I need to take it out for a short drive to get the airbridge nice and hot and then tighten down the T-bolt clamps again so it will form around MAF housing again. I decided to hold off on using the hairspray trick to see how it goes. I was afraid the hairspray would set before I had everything together and then I'd have a devil of a time getting it back apart again if I needed to.

Heck, I hope I remember to hook up the MAF/IAT cable before I take the car out. I just remembered that it's still disconnected. :banghead:

that is a good question, Normally it aides in helping the connectors slip over each other. I soaked mine when I did them and they stayed maneuverable for a couple minutes as I aligned all the piping. being that the hair spray is trapped between the coupler and the plastic or metal tube, it does not evaporate as fast as if it were sprayed on hair.

Yeah, that makes sense. I suppose if I have continual problems with the couplers, that will be my next step with the hairspray. I have to admit that I'm a bit concerned with REALLY cranking down on the clamp that attaches the south end of the airbridge to the front of the MAF sensor. That part of the MAF sensor housing is only plastic, so I don't know how flexible it may become when hot. I sure don't want to crush it out of shape. At least not until I can figure out a way to do without the MAF housing being there at all.

Finally was able to take the car out today, so I ran to a Chevron station and filled the gas tank up with 93 octane E10. I had just over a quarter tank of the non-ethanol gas remaining when I got there.

I was doing some data logging and noted that the AFR was showing rather lean, which I expected since you have to set the AFR ratio for E10 (10 percent ethanol gasoline) to approximately 14.13. E0 (zero percent ethanol) gasoline is usually set for 14.63. Anyway, it was showing it was running a bit lean, so I found a place to pull over and adjusted my tune accordingly. Since I still had about 25 percent non-ethanol gasoline in the tank when I filled it up, I set the AFR to 14.20 to compensate.

The data collected during the logging wasn't too far off from being what it needed to be, but then again I wasn't pushing the engine into boost, since I had also put on the new coupler a few days ago, and needed to re-tighten the clamps with the airbridge hot and more pliable. So I didn't want to run the risk of blowing the airbridge off by running up into boost quite yet. But I can see I'm going to have to make more runs to collect data to dial in the VE table somewhat.

Just in case anyone is interested, the philosophy behind tuning the fueling appears to be to set the AFR ratio for the blend of gasoline being used, and in the case with my car, set the values in table B3647 to tell the PCM what I want the AFR to be. The data logging uses the wideband O2 sensor to determine what the AFR actually IS and compares that against what the COMMANDED AFR (via table B3647) is and gives a difference in lambda. A value of 1.00 indicates that the wideband is detecting an AFR equal to what the commanded AFR is supposed to be. An AFR greater than 1.00 indicates that the mixture is lean, and the AFR lower than 1.00 is rich. Multiplying that lambda value to the comparable cells in the VE table (B0101) will then adjust that table accordingly. Multiplying a cell by a value greater than 1.00 tells the table that the cell should actually be larger, so more fuel is needed to bring the value DOWN to where it needs to be. Multiplying a cell by a value less than one tells the table that the cell needs to be smaller, so LESS fuel is needed. Have to kind of think about this using negative logic.

The place where I find this comparison data to determine the difference between commanded and actual AFR is a map file in the scanning software that is filled with data during data logging. Each cell is referenced via manifold vacuum/pressure on one axis and engine RPM on the other axis.

Leaner values in the map indicate that the corresponding VE table cell needs more fuel, so by making the cell value larger, that tells the PCM to give a longer squirt (more) of fuel.

Richer values in the map indicate that the corresponding VE table cell needs less fuel, so by making the cell value smaller, that tells the PCM to give a shorter squirt (less) of fuel.

You have learned a lot during this ordeal Rich.