Rear Mount STS kit with boost issues
06-02-2017, 02:27 PM
#1
Racer
Thread Starter
Rear Mount STS kit with boost issues
Ive been dealing with fixing little things with my car for sometime now and its finally in its last stages. I have an STS kit on the car but decided to go my own route on the turbo setup and am running oil-less 6267 comp turbos.
The car runs great now that the tunes sorted out but I still (had a post in the past) cant figure out my boost issues. Prior to this I had my boost reference tied into my PCV system and I was pressurizing my gas tank. Now thats all sorted out and I'm having issues with the car building boost still. I have 8psi springs in my gates and the car will see 1 or 2 psi in 1-3 gear and my tuner saw almost 6psi at one point on the freeway during a 4th gear pull.
I was wondering if there were any STS guys out there that could chime in and tell me how their vacuum system is routed and their pcv system is as well. Right now I had the turbo compressor housings tapped and am running those to my gates and my boost controller all int he back. I also have an ECS external fuel pump on a 5psi hobbs switch tied into the line. I have the BOV running off a vacuum block that is tied into the brake booster. I put the stock pcv system back into place and am running a catch can with a filter coming off the front of the breather on the passenger valve cover. Thats pretty much the jist of my system. Anyone with any feedback on this can give me some info, id really appreciate it.
The car runs great now that the tunes sorted out but I still (had a post in the past) cant figure out my boost issues. Prior to this I had my boost reference tied into my PCV system and I was pressurizing my gas tank. Now thats all sorted out and I'm having issues with the car building boost still. I have 8psi springs in my gates and the car will see 1 or 2 psi in 1-3 gear and my tuner saw almost 6psi at one point on the freeway during a 4th gear pull.
I was wondering if there were any STS guys out there that could chime in and tell me how their vacuum system is routed and their pcv system is as well. Right now I had the turbo compressor housings tapped and am running those to my gates and my boost controller all int he back. I also have an ECS external fuel pump on a 5psi hobbs switch tied into the line. I have the BOV running off a vacuum block that is tied into the brake booster. I put the stock pcv system back into place and am running a catch can with a filter coming off the front of the breather on the passenger valve cover. Thats pretty much the jist of my system. Anyone with any feedback on this can give me some info, id really appreciate it.
06-02-2017, 02:55 PM
#2
Racer
Thread Starter
Just to try to stray away from having questions asked that might pertain to this Ill add a bit more info.
The car is running the stock 2.5" exhaust and its heat wrapped from the headers to the over axle area of the exhaust. Turbos are comp oilless 6267s in a T3 setup (CT3 triple ball bearing oiless with billet wheels). The only modification to the exhaust was vbanding the slip portion of the turbo kit to the mid pipe for ease of install/removal.
I just replaced the exhaust gaskets and had the catalytic converters punched out to tune the car (stock cats just removed insides) and I'm 99.99% sure there are no exhaust leaks. Boost leaks could be a possibility with all the piping but i had the front portion of the piping welded together to eliminate some couplers and make things nicer. It could be a boost leak but the fact that I'm seeing 1-2 psi in lower gears and more up top is confusing. I know there could be some pressure drop from the rear mount to the front where boost is being read (through HP Tuners via a 3 bar map) but I couldnt imagine with an 8psi spring id only see 1-2 psi.
Doing a quick google search it seems this is a common problem among rear mount systems so I believe I might be missing something.
The car is running the stock 2.5" exhaust and its heat wrapped from the headers to the over axle area of the exhaust. Turbos are comp oilless 6267s in a T3 setup (CT3 triple ball bearing oiless with billet wheels). The only modification to the exhaust was vbanding the slip portion of the turbo kit to the mid pipe for ease of install/removal.
I just replaced the exhaust gaskets and had the catalytic converters punched out to tune the car (stock cats just removed insides) and I'm 99.99% sure there are no exhaust leaks. Boost leaks could be a possibility with all the piping but i had the front portion of the piping welded together to eliminate some couplers and make things nicer. It could be a boost leak but the fact that I'm seeing 1-2 psi in lower gears and more up top is confusing. I know there could be some pressure drop from the rear mount to the front where boost is being read (through HP Tuners via a 3 bar map) but I couldnt imagine with an 8psi spring id only see 1-2 psi.
Doing a quick google search it seems this is a common problem among rear mount systems so I believe I might be missing something.
06-03-2017, 01:25 AM
#3
Melting Slicks
I chased this same issue as well. Run your lines like this picture.
Run your external hobb switch to your brake booster manifold vacuum.
Run your blow off valve to intake right behind throttle body.
Run your external hobb switch to your brake booster manifold vacuum.
Run your blow off valve to intake right behind throttle body.
06-04-2017, 10:58 AM
#4
Le Mans Master
These STS systems are still around? Excuse me as I've been out of the F/I scene for 7 years.
06-06-2017, 11:41 AM
#5
Racer
Thread Starter
Hmm, so youre taking your source from one turbo? Do you see any benefit to taking the wastegate source from the charge pipe going from intercooler to throttle body? Ive got a suspicion that taking source from compressor housing while using an 8psi spring, im seeing a ton of pressure drop by the time it gets to the intake manifold which is why im getting a 4psi peak boost reading in only higher gears. with 10+ feet of pipe and an intercooler, im sure there is bound to be a bit of pressure drop just naturally.
Car runs really strong other than not building boost. BOV seems to be functioning and I dont hear/feel any vacuum leaks. car is holding vacuum well.
06-06-2017, 11:44 AM
#6
Racer
Thread Starter
This is basically a replication of the STS kit with some improvements I had a fabricator do for me. Aside from working out these boost issues the car sounds absolutely amazing and under just 4psi this thing hauls major @$$.
One of the biggest advantages I see to this is the heat. I drove the car yesterday when it was about 100F out, had the a/c on and i didnt see any temps over 212...completely stock cooling system and oil-less turbos that require me to plumb water to the back so im actually putting more strain on the stock system. I'd say that speaks volumes about how well these kits keep heat away from the car.
06-08-2017, 11:48 AM
#7
Melting Slicks
Mine is not a stock sts either. Just using the sts charge piping as everything else has to be upgraded.
Again I had the same issues as you.
Just reference one turbo
Yes wastegate goes to right after throttle body. Also check and
Make sure what spring size you actually have. Might not be 8lbs.
Some are 5.7 stock. Either turn up your boost controller or put in
some heavier springs. After fixing vacuum routing I get 12.2 on a 11lb
Spring and messing with controller it's hitting over 15.5 by 5000 and
6lbs at 2800.
Again I had the same issues as you.
Just reference one turbo
Yes wastegate goes to right after throttle body. Also check and
Make sure what spring size you actually have. Might not be 8lbs.
Some are 5.7 stock. Either turn up your boost controller or put in
some heavier springs. After fixing vacuum routing I get 12.2 on a 11lb
Spring and messing with controller it's hitting over 15.5 by 5000 and
6lbs at 2800.
The following users liked this post:
GaragedLS2 (06-09-2017)
06-09-2017, 05:08 PM
#8
Racer
Thread Starter
Mine is not a stock sts either. Just using the sts charge piping as everything else has to be upgraded.
Again I had the same issues as you.
Just reference one turbo
Yes wastegate goes to right after throttle body. Also check and
Make sure what spring size you actually have. Might not be 8lbs.
Some are 5.7 stock. Either turn up your boost controller or put in
some heavier springs. After fixing vacuum routing I get 12.2 on a 11lb
Spring and messing with controller it's hitting over 15.5 by 5000 and
6lbs at 2800.
Again I had the same issues as you.
Just reference one turbo
Yes wastegate goes to right after throttle body. Also check and
Make sure what spring size you actually have. Might not be 8lbs.
Some are 5.7 stock. Either turn up your boost controller or put in
some heavier springs. After fixing vacuum routing I get 12.2 on a 11lb
Spring and messing with controller it's hitting over 15.5 by 5000 and
6lbs at 2800.
I'm going to boost leak check it one more time and change where my wastegates are getting boost from as right now its coming off compressor as stated before. I'll move this to the intake pipe by throttle body and see if it solves my issues. I appreciate your help tremendously.
06-10-2017, 02:45 PM
#9
Melting Slicks
In my opinion those are very large but bad *** turbos.I have a set of 58/58 precision dual ball bearing turbos with only a .63 a/r. And I feel these are a little to large as well.
What helped it hit boost was to increase the spring size to give them a chance to work. Set your overboost shutdown to whatever you and your tuber decides. Do you have a turbo cam and a stall convertor?
I also took off my z06 exhaust and went back to the stock ls2 manifolds and wrapped it all up.You can sell those turbos and get smaller or save them for when you build a larger engine, You can also swap out the housings for a smaller a/r to bring it on boost earlier.Be careful because once you do get it all right the boost comes on very fast and can spike up pretty fast before gates can release.
What helped it hit boost was to increase the spring size to give them a chance to work. Set your overboost shutdown to whatever you and your tuber decides. Do you have a turbo cam and a stall convertor?
I also took off my z06 exhaust and went back to the stock ls2 manifolds and wrapped it all up.You can sell those turbos and get smaller or save them for when you build a larger engine, You can also swap out the housings for a smaller a/r to bring it on boost earlier.Be careful because once you do get it all right the boost comes on very fast and can spike up pretty fast before gates can release.
The following users liked this post:
GaragedLS2 (06-12-2017)
06-12-2017, 12:09 PM
#10
Racer
Thread Starter
In my opinion those are very large but bad *** turbos.I have a set of 58/58 precision dual ball bearing turbos with only a .63 a/r. And I feel these are a little to large as well.
What helped it hit boost was to increase the spring size to give them a chance to work. Set your overboost shutdown to whatever you and your tuber decides. Do you have a turbo cam and a stall convertor?
I also took off my z06 exhaust and went back to the stock ls2 manifolds and wrapped it all up.You can sell those turbos and get smaller or save them for when you build a larger engine, You can also swap out the housings for a smaller a/r to bring it on boost earlier.Be careful because once you do get it all right the boost comes on very fast and can spike up pretty fast before gates can release.
What helped it hit boost was to increase the spring size to give them a chance to work. Set your overboost shutdown to whatever you and your tuber decides. Do you have a turbo cam and a stall convertor?
I also took off my z06 exhaust and went back to the stock ls2 manifolds and wrapped it all up.You can sell those turbos and get smaller or save them for when you build a larger engine, You can also swap out the housings for a smaller a/r to bring it on boost earlier.Be careful because once you do get it all right the boost comes on very fast and can spike up pretty fast before gates can release.
03-15-2022, 09:28 AM
#12
Safety Car
