• Got the Contributing Memberships stuff finally worked out and made up a thread as a sort of "How-To" to help people figure out how to participate. So if you need help figuring it out, here's the thread you need to take a look at -> http://www.corvetteflorida.com/forums/showthread.php?t=3581 Thank you, everyone! Rich Z.

427 engine (part 2) - RHS block

Rich Z said:
I'm talking to Vernon Hills at STSturbo and he recommends that I put two wastegates on the car. Aaron agrees if I want to go to 10 lbs of boost instead of the stock 6 lbs
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Rich, I just can't express in words how badly I feel for you.

If 6# of boost will work with one waste gate I think that's the route I would go. On my '87 Buick I think the waste gate was mounted with the turbo so I don't know how one waste gate controls two turbos.

I would think with 6# you would have way more power than you'll ever be able to use but maybe you have some facts that show your power curve would drop dramatically and in that case I would go with two. Just my thoughts.

Hang in there cause it has to get better.
 
Rich Z said:
I just asked Bryan at LME about the max boost that block could take without getting close to the ragged edge of tuning and he said it could take 25 lbs. Figure on a max of 1200 rwhp.

If the turbos will only put out around 13 lbs when the wastegate fails, then I'm thinking that perhaps I don't need the wastgates at all. I'm guessing they won't be cheap, and if I want to go with 13 lbs, then why bother with them?

Anyone able to poke some holes in my logic here?
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I'm lost. I thought the waste gate got rid of excess boost. Don't you have to have one?
 
Bob K said:
I'm lost. I thought the waste gate got rid of excess boost. Don't you have to have one?
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On a stock engine without forged components, you have to watch the amount of boost carefully. Although I have seen some people push 10+ lbs through a stock LS6, it's not something that is recommended. When I specified what I wanted in the new engine, I stated that I wanted it to be able to handle SUBSTANTIALLY more boost than the 6.5 I was getting with that stock motor.

What a wastegate does is to allow you to set a point via a pressure spring that will bleed off any boost above a set value that the spring is rated for. This is to protect the motor from excessive boost.

The 427 not only puts out more air as exhaust, but it also DEMANDS more air into the intake. There was some question in my mind as to whether those turbos could keep up with the demand of the intake. From what I heard from Aaron, the boost reached 13 lbs indicating that the wastegate had failed. So I'm thinking that this might be the max boost that the system can deliver. Since the motor itself can handle a lot more, then do I really need the wastegates at all? Since I already had one, then I was going to keep it there and just put a different spring to provide 10 lbs. But heck, three more pounds won't be that big of a difference, and I could dodge the expense of the wastegates if they really aren't needed in my application.

This might be one of those things that looks good on paper, but not real good in practicality, however.... :shrug01:
 
Rich Z said:
On a stock engine without forged components, you have to watch the amount of boost carefully. Although I have seen some people push 10+ lbs through a stock LS6, it's not something that is recommended. When I specified what I wanted in the new engine, I stated that I wanted it to be able to handle SUBSTANTIALLY more boost than the 6.5 I was getting with that stock motor.

What a wastegate does is to allow you to set a point via a pressure spring that will bleed off any boost above a set value that the spring is rated for. This is to protect the motor from excessive boost.

The 427 not only puts out more air as exhaust, but it also DEMANDS more air into the intake. There was some question in my mind as to whether those turbos could keep up with the demand of the intake. From what I heard from Aaron, the boost reached 13 lbs indicating that the wastegate had failed. So I'm thinking that this might be the max boost that the system can deliver. Since the motor itself can handle a lot more, then do I really need the wastegates at all? Since I already had one, then I was going to keep it there and just put a different spring to provide 10 lbs. But heck, three more pounds won't be that big of a difference, and I could dodge the expense of the wastegates if they really aren't needed in my application.

This might be one of those things that looks good on paper, but not real good in practicality, however.... :shrug01:
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OK, now I get it. I guess you have to know how much boost they'll put out and maybe a gauge so you can keep an eye on it. I have not had one since '87 so I don't know anything about the ones you have. I'm thinking twin turbos put out way more than 13#.
 
Bob K said:
OK, now I get it. I guess you have to know how much boost they'll put out and maybe a gauge so you can keep an eye on it. I have not had one since '87 so I don't know anything about the ones you have. I'm thinking twin turbos put out way more than 13#.
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It depends on the engine they are hooked up to. "Boost" is the amount of forced air that the turbos can deliver over and above what the vacuum of the engine is trying to pull into it. The more air the engine needs, the bigger the turbos have to be, or the faster they have to spin, to keep up. I have the smaller turbos on the car because I prefer faster spooling over higher top end HP. I wanted the power band to be closer to where my "more spirited" driving would be rather than focused way up in the high RPM ranges. So I'm thinking those turbos just might be maxed out at 13 lbs. What would really need to be done is to run the car on the dyno and see if the boost started DROPPING at the highest RPM range. That would mean that the engine got to the point where it started needing more air than the boost condition could supply. Which as long as it didn't drop the boost down to zero, then that would probably be OK. I don't plan on spending very much time driving the car reving above 6,000 rpm anyway.
 
It is an extra saftey feature and not that much more $$ to do. Each turbo is fed by your exhaust on the side the turbo is mounted. Having one on each turbo with one controller "T"'d to it will bleed exhaust quickly form each turbo. Now I know that both feed into one intercooler so it can be equalized there before it reaches the intake, but at the turbos allows each to bleed off as needed right there.

If you look at the pics of the V6 kit I just did you can see (mid-mount turbos) where each is. I used 56mm turbos on this which is overkill, but the owner wanted slower spool-up to save on the tranny shock at launch (no aftermarket hard parts for the tranny out yet) and wants it to build from 3k or so RPM and up to 7K. No boost fall off with it.
 
OK, I do realize it's a safety feature, but the safety is to protect the motor from being over boosted. IF the turbos cannot produce more than half the amount of boost the motor can handle, then what other purpose do they serve? If the turbos cannot exceed what the motor can handle, why do I need them?

I know I'm bucking a lot of "conventional" wisdom about forced induction, but this wouldn't be the first time that the answer I got was nothing better than "that's just because it's the way we have always done it."

So please give me some solid reasons and logic here about this.

Hell, I had people on another forum swearing up and down that those STS turbos wouldn't even be able to go into a boost condition with that 427 engine.

Anyway, I got a price from STS and this would cost me another $850. Quite frankly, I just do not want to spend any unnecessary amount of money on this car any longer. So I need to know if this is REALLY necessary.
 
$850 is WAY to much. all you need is another matching wastegate (find out the brand & model and buy from a discount vendor) and a small amount of pipe & flanges. I cut and welded the entire system on the camaro you see in one week.

The STS turbos are not made by STS, they are sourced from the manufacturer. The size & configuration of the turbos dictate the size motor and boost they can support.

Remeber, we made 1200 hp at 21# od boost on a 408 CI with twin 62mm turbos, and 900 with FRC Toms 408 with the STS 58mm units.

The other saftey feature on going with dual wastegates is for turbo longevity.

What size are your turbo's? And it is only able to make 13#'s?
 
Rich Z said:
OK, I do realize it's a safety feature, but the safety is to protect the motor from being over boosted. IF the turbos cannot produce more than half the amount of boost the motor can handle, then what other purpose do they serve? If the turbos cannot exceed what the motor can handle, why do I need them?

I know I'm bucking a lot of "conventional" wisdom about forced induction, but this wouldn't be the first time that the answer I got was nothing better than "that's just because it's the way we have always done it."

So please give me some solid reasons and logic here about this.

Hell, I had people on another forum swearing up and down that those STS turbos wouldn't even be able to go into a boost condition with that 427 engine.

Anyway, I got a price from STS and this would cost me another $850. Quite frankly, I just do not want to spend any unnecessary amount of money on this car any longer. So I need to know if this is REALLY necessary.
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Aren't you assuming the max boost for your system? If you knew for sure or if someone else could give you hard numbers then you would have your answer. I think. :shrug01:
 
RevXtreme 1 said:
$850 is WAY to much. all you need is another matching wastegate (find out the brand & model and buy from a discount vendor) and a small amount of pipe & flanges. I cut and welded the entire system on the camaro you see in one week.

The STS turbos are not made by STS, they are sourced from the manufacturer. The size & configuration of the turbos dictate the size motor and boost they can support.

Remeber, we made 1200 hp at 21# od boost on a 408 CI with twin 62mm turbos, and 900 with FRC Toms 408 with the STS 58mm units.

The other saftey feature on going with dual wastegates is for turbo longevity.

What size are your turbo's? And it is only able to make 13#'s?
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I really don't need to make this over complicated, neither, to be perfectly honest about it. So I'm not keen on the idea of a custom exhaust piping job. Those pipes would also need to be ceramic coated to match the rest of the system. I think Aaron is about burned out with my car as well, so running a custom exhaust job at him would probably push him over the edge. He says he has NEVER seen a car with as many problems that sprout up everywhere at any time.

The only thing I know about what type of turbos are on my car is the info I got from Rashelle a while back. Precision 60-1, .48 hotside.

I had the original turbos replaced later after the install to get smaller ones that would spool up quicker. I'm guessing it's the hotside that is smaller.

Yeah, I need to talk to Aaron tomorrow about the specifics of what he said.

Obviously I am assuming things from the conversation I had with him. He said that he didn't notice that the wastegate had failed until he looked at the boost gauge and saw that it was hitting 13 pounds of boost instead of clipping at the 6 pounds the spring was set at. He then said that explained the high HP numbers he was getting.

So my assumption from the above is that 13 pounds is where the system is maxing out. But of course, it could be that the waste gate failed in such a way that it started dumping extra boost at 13 lbs and didn't just be completely non functional. Aaron if very experienced with turbo systems so I'll know more when I talk to him. I certainly am not going to make any decisions until I know more about what I need to decide on.

Oh as for turbo longevity, if in fact the turbos are maxing out at 13 lbs, how would the wastegates help in that capacity? Vernon Hills at STS says those turbos are capable of a lot more boost, so it wouldn't be like I was pushing them over their limits at 13 psi.
 
Its not the amount of boost made, it is the turbos spinning at higher and harder RPM's all the time instead of the wastegates bleeding past the exhaust gasses that drive them.

I think that is the confusion....it is the constant duty of the turbos working VS the wastegate allowing them to just idle along when not going hard acceleration.
 
RevXtreme 1 said:
Its not the amount of boost made, it is the turbos spinning at higher and harder RPM's all the time instead of the wastegates bleeding past the exhaust gasses that drive them.

I think that is the confusion....it is the constant duty of the turbos working VS the wastegate allowing them to just idle along when not going hard acceleration.
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Thanks Tracy. I didn't know that.
 
RevXtreme 1 said:
Its not the amount of boost made, it is the turbos spinning at higher and harder RPM's all the time instead of the wastegates bleeding past the exhaust gasses that drive them.

I think that is the confusion....it is the constant duty of the turbos working VS the wastegate allowing them to just idle along when not going hard acceleration.
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OK, I have to admit that I don't understand this then. My understanding of the operation of the wastegate is to simply bleed off excess boost when it exceeds the amount that the spring is set to allow to go to the engine. Until that point is reached, the wastegate does NOTHING at all as the spring allows all the exhaust flow to go to the turbos. So it appears to me that all of the exhaust gasses are going to the turbos all of the time UNTIL the spring activates the opening of the wastegate at the preset boost pressure level.

As evidence to support this, when I had my LS6 engine in my C5Z I would very often hear the turbos in action even in 6th gear when on a slightly inclined roadway. So RPMs were low, of course, and yet the turbos were obviously spooling up.

So if I am mistaken about how a wastegate works, please straighten me out, because I don't understand how this device CAN work in any way other than I am envisioning without some complicated activation circuitry involved that will turn it on and off in pre-programmed set points.
 
I've always thought the main reason for the wastegate is to relieve pressure when you come off the gas. So if you are full throttle, go into a turn and lift, without the wastegate the turbos will keep spooling and cause continued boost....then causing the engine to run very lean. I believe it'll cause other issues, but I've tapped out my boost knowledge.
 
shakedown067 said:
The main reason for the wastegate is to relieve pressure when you come off the gas. So if you are full throttle, go into a turn and lift, without the wastegate the turbos will keep spooling and cause continued boost....then causing the engine to run very lean. I believe it'll cause other issues, but I've tapped out my boost knowledge.
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I believe what you are referring to is actually the blowoff valve.
 
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