single rear mount turbo c5 with boost issues (lengthy post)
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single rear mount turbo c5 with boost issues (lengthy post)
Good morning tech,
I have been getting the bugs out of the my Single rear mount turbo setup on my c5 corvette. I looking for some advice to possibly an idea where to check on resolving my boost issues. First a little info about the car.
2001 C5 corvette:
Stock 4l60e with 3600 stall.
Stock bottom end.
Comp lsr cam 231/239 113
stock 243 heads
melling oil pump
ls7 lifters
Head studs
BTR springs with supporting mods.
Now with my cam only setup mentioned above the car did 400 + hp on the dyno and i was running in the 7's in the 1/8.
After my rear mount setup I am currently only able to make 5lbs on a 10 lb waste gate spring.
Turbo setup:
stock manifolds
3 inch exhaust feeding a t4 flange with a on3 turbo 78/75 with a .96 ar exhaust housing.
55 mm or 60mm waste gate (sorry i cant remember at the moment)
2.5 aluminum cold side
A&a early gen intercooler
4inch tube that feeds from intercooler to throttle body
2 bar map SD tune.
Manual boost controller runing directly off the wastegate.
down pipe is 3inch pipe with vband that is approximately 15" long.
oil feed is 4an and drain is 10an both with one way check valves pre turbo and post turbo, along with remote oil pump.
Yes i have checked for exhaust leaks and cold side leaks and there are none currently present.
After testing the car at the track last night it wouldnt make more than 5lbs on a 10 lb spring. I have not ran the car without the boost controller that will be my next step, but i am also looking for other things to cross of my list in hunting this boost issue. Sorry for the lengthy post, but I didnt want to leave anything out. Any help would be greatly appreciated.
Thanks,
Chuck
I have been getting the bugs out of the my Single rear mount turbo setup on my c5 corvette. I looking for some advice to possibly an idea where to check on resolving my boost issues. First a little info about the car.
2001 C5 corvette:
Stock 4l60e with 3600 stall.
Stock bottom end.
Comp lsr cam 231/239 113
stock 243 heads
melling oil pump
ls7 lifters
Head studs
BTR springs with supporting mods.
Now with my cam only setup mentioned above the car did 400 + hp on the dyno and i was running in the 7's in the 1/8.
After my rear mount setup I am currently only able to make 5lbs on a 10 lb waste gate spring.
Turbo setup:
stock manifolds
3 inch exhaust feeding a t4 flange with a on3 turbo 78/75 with a .96 ar exhaust housing.
55 mm or 60mm waste gate (sorry i cant remember at the moment)
2.5 aluminum cold side
A&a early gen intercooler
4inch tube that feeds from intercooler to throttle body
2 bar map SD tune.
Manual boost controller runing directly off the wastegate.
down pipe is 3inch pipe with vband that is approximately 15" long.
oil feed is 4an and drain is 10an both with one way check valves pre turbo and post turbo, along with remote oil pump.
Yes i have checked for exhaust leaks and cold side leaks and there are none currently present.
After testing the car at the track last night it wouldnt make more than 5lbs on a 10 lb spring. I have not ran the car without the boost controller that will be my next step, but i am also looking for other things to cross of my list in hunting this boost issue. Sorry for the lengthy post, but I didnt want to leave anything out. Any help would be greatly appreciated.
Thanks,
Chuck
#2
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What exhaust manifold gaskets and collector gaskets are you using? How did you check for leaks? Plumb that boost reference line coming out of the turbo to the side of the wastegate without a controller hooked up.
Edit. I would by a new elbow and tap the compressor cover instead of having that fitting in the rubber hose. I would also check your boost pressure at the rear of the car.
Edit. I would by a new elbow and tap the compressor cover instead of having that fitting in the rubber hose. I would also check your boost pressure at the rear of the car.
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What exhaust manifold gaskets and collector gaskets are you using? How did you check for leaks? Plumb that boost reference line coming out of the turbo to the side of the wastegate without a controller hooked up.
Edit. I would by a new elbow and tap the compressor cover instead of having that fitting in the rubber hose. I would also check your boost pressure at the rear of the car.
Edit. I would by a new elbow and tap the compressor cover instead of having that fitting in the rubber hose. I would also check your boost pressure at the rear of the car.
Here is a picture of the cold side when i checked for leaks. i checked the hotside while it was off the car.
thank you for the advice as i am open for any suggestions at the moment.
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Where are you getting your boost reference from? I'm not sure what you mean by "directly off the wastegate" as that's the only way to hook up a manual boost controller. Boost reference should be on the intake manifold (since manifold pressure is what you want to control). From there to the wastegate with the boost controller in between.
It should be worth noting that running 3" downpipes into a 3" single pipe into the turbo is about the worse possible way to do it. You're losing a massive amount of kinetic energy an pressure between the engine and the turbo. If your setup is fully sealed it's possible that recompressing the air to get into the turbo is jacking exhaust pressure so far up that the engine and turbo can't breath. Smaller pipes retain velocity and KE that spool the turbo as well as allowing exhaust to flow freely out the system instead of requiring mechanical work from the engine to push air through the bottle neck that is the turbine.
It should be worth noting that running 3" downpipes into a 3" single pipe into the turbo is about the worse possible way to do it. You're losing a massive amount of kinetic energy an pressure between the engine and the turbo. If your setup is fully sealed it's possible that recompressing the air to get into the turbo is jacking exhaust pressure so far up that the engine and turbo can't breath. Smaller pipes retain velocity and KE that spool the turbo as well as allowing exhaust to flow freely out the system instead of requiring mechanical work from the engine to push air through the bottle neck that is the turbine.
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Where are you getting your boost reference from? I'm not sure what you mean by "directly off the wastegate" as that's the only way to hook up a manual boost controller. Boost reference should be on the intake manifold (since manifold pressure is what you want to control). From there to the wastegate with the boost controller in between.
It should be worth noting that running 3" downpipes into a 3" single pipe into the turbo is about the worse possible way to do it. You're losing a massive amount of kinetic energy an pressure between the engine and the turbo. If your setup is fully sealed it's possible that recompressing the air to get into the turbo is jacking exhaust pressure so far up that the engine and turbo can't breath. Smaller pipes retain velocity and KE that spool the turbo as well as allowing exhaust to flow freely out the system instead of requiring mechanical work from the engine to push air through the bottle neck that is the turbine.
It should be worth noting that running 3" downpipes into a 3" single pipe into the turbo is about the worse possible way to do it. You're losing a massive amount of kinetic energy an pressure between the engine and the turbo. If your setup is fully sealed it's possible that recompressing the air to get into the turbo is jacking exhaust pressure so far up that the engine and turbo can't breath. Smaller pipes retain velocity and KE that spool the turbo as well as allowing exhaust to flow freely out the system instead of requiring mechanical work from the engine to push air through the bottle neck that is the turbine.
Also i have added a video to my youtube channel of me bench testing the wastegate. The hellfire ring was installed when it was on the car...
Link to video:
Last edited by igtabg1; 07-15-2016 at 02:28 PM.
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#10
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Rear mounts won't work like front mounts. Running your boost control from the cover results in low and erratic manifold boost pressure. You must run your boost reference from the intake manifold. Even then, running that much rubber line causes problems. My old solution was to plumb steel brake line tubing from the intake to the boost controller to the wastegate. My new solution is to ditch the bullshit rearmount like I should have done in the first place. Rearmounts are a simple starter solution for someone who wants to learn about turbocharging, but the ease of install is absolutely their only positive attribute.
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Thank you guys for the advice. Since I rarely get to drive the car on the weekends. I had planned on running the vacuum source from the vacuum block at the front of the car instead of that add a port coupler. And also bypassing the boost controller and running it off the 10lb spring before I change the spring in the wastegate. One of the ideas I have been throwing around is, and again Ifor im way off just let me know, my my wastegate (with the 10best spring) is fully open by 6 lbs would that be a reason the car isn't making over 5 or 6 lbs ? And by switching to a 15 lb or 12 lb spring would that help me make 10lbs ? I know the rear mount is a lot more complicated than a front mount but with my limited fabricating skills and race car funds, it would have to be awhile before I did a custom front mount turbo. Thanks again for the advice. As soon as I test some things out I'm going to report back with my findings.
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Yeah low boost has nothing to do with any boost source, vacuum hoses or boost controllers. You probably want a smaller pipe running to the rear, say 2.5" at a guess, and just as important to heat wrap it the whole way. May also need a smaller rear housing.
There was a reasonably detailed thread on here that was almost identical to this, and he went through and resolved it with heat wrapping and getting rid of long tube headers for standard manifolds. Can't remember enough detail to find it, but someone else on here might.
There was a reasonably detailed thread on here that was almost identical to this, and he went through and resolved it with heat wrapping and getting rid of long tube headers for standard manifolds. Can't remember enough detail to find it, but someone else on here might.
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Yeah low boost has nothing to do with any boost source, vacuum hoses or boost controllers. You probably want a smaller pipe running to the rear, say 2.5" at a guess, and just as important to heat wrap it the whole way. May also need a smaller rear housing.
There was a reasonably detailed thread on here that was almost identical to this, and he went through and resolved it with heat wrapping and getting rid of long tube headers for standard manifolds. Can't remember enough detail to find it, but someone else on here might.
There was a reasonably detailed thread on here that was almost identical to this, and he went through and resolved it with heat wrapping and getting rid of long tube headers for standard manifolds. Can't remember enough detail to find it, but someone else on here might.
#15
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Step one-send pressure to the top-this should be all of it. See if it spikes past 10psi.
Since you have already boost leak tested it, there is literally no point to doing anything else. Until you determine if your system can actually make the boost.
IMO-you will have to kick down to a 2.5 hot side to get some exhaust velocity back.
Since you have already boost leak tested it, there is literally no point to doing anything else. Until you determine if your system can actually make the boost.
IMO-you will have to kick down to a 2.5 hot side to get some exhaust velocity back.
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So does the spool look the same with the larger piping or does that make it slower?
I would imagine that a single 2.5 should be plenty to feed the turbo. What makes you say it had too much backpressure? Just the boost dropping off? Or were you actually measuring it? If anything I'd use the smaller piping to help maintain heat and velocity and put a bigger housing on the turbo to reduce backpressure.
I would imagine that a single 2.5 should be plenty to feed the turbo. What makes you say it had too much backpressure? Just the boost dropping off? Or were you actually measuring it? If anything I'd use the smaller piping to help maintain heat and velocity and put a bigger housing on the turbo to reduce backpressure.
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So does the spool look the same with the larger piping or does that make it slower?
I would imagine that a single 2.5 should be plenty to feed the turbo. What makes you say it had too much backpressure? Just the boost dropping off? Or were you actually measuring it? If anything I'd use the smaller piping to help maintain heat and velocity and put a bigger housing on the turbo to reduce backpressure.
I would imagine that a single 2.5 should be plenty to feed the turbo. What makes you say it had too much backpressure? Just the boost dropping off? Or were you actually measuring it? If anything I'd use the smaller piping to help maintain heat and velocity and put a bigger housing on the turbo to reduce backpressure.
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60psi of backpressure is huge for that boost. That, to me, is a clear indication of what needs to be fixed, not the boost issue. Where were you measuring it from? I'm not overly familiar with that turbo but it's a reasonable size, should not be causing such a restriction.
Have you got any of those flexible bellows in the exhaust before the turbo? And what is your current back pressure? It sounds like you have some sort of restriction in your exhaust. Reading your first post again, it sounds as though it made 400whp NA, and 465whp at 9psi with your old turbo setup in the graph above? You should have picked a damn site more than that.
Have you got any of those flexible bellows in the exhaust before the turbo? And what is your current back pressure? It sounds like you have some sort of restriction in your exhaust. Reading your first post again, it sounds as though it made 400whp NA, and 465whp at 9psi with your old turbo setup in the graph above? You should have picked a damn site more than that.
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60psi of backpressure is huge for that boost. That, to me, is a clear indication of what needs to be fixed, not the boost issue. Where were you measuring it from? I'm not overly familiar with that turbo but it's a reasonable size, should not be causing such a restriction.
Have you got any of those flexible bellows in the exhaust before the turbo? And what is your current back pressure? It sounds like you have some sort of restriction in your exhaust. Reading your first post again, it sounds as though it made 400whp NA, and 465whp at 9psi with your old turbo setup in the graph above? You should have picked a damn site more than that.
Have you got any of those flexible bellows in the exhaust before the turbo? And what is your current back pressure? It sounds like you have some sort of restriction in your exhaust. Reading your first post again, it sounds as though it made 400whp NA, and 465whp at 9psi with your old turbo setup in the graph above? You should have picked a damn site more than that.
I did test the car a little bit in mexico. Both these test bypassed the boost controller. First i ran the car with the supplied vacuum hose from the front of the car to the wastegate, ditched the add a port silicone coupler and it made no difference. Then i took the vacuum off the wastegate and ran "spring only" and although it felt a bit stronger it only resulted in 5 lbs on the top end. My next test will to be trying a high psi spring and see where that gets me.