turbo spools but no boost
x2 on the last comment, my friend was running an Mp 70 on his ls1 rear mount setup and made 540 hp on 9 psi here in the mile high city, so its deffinetly not the turbo size, I would look into getting a different spring for the wastegate if you dont have any major boost leaks after you check with the hardware store setup that was suggested to you.
The compressor could be/likely is too small, however I doubt that is all of the problem. You have to keep in mind that transient response of the engine's air demand will determine how the turbo climbs into the compressor map. If you slam the throttle open at high RPM and suddenly demand a massive amount of air from the turbo, the small compressor will be hard pressed to feed the air demands AND build boost. If you look at the compressor map, with that rapid transient air demand, the position moves quickly across the map very horizontally as opposed to climbing into the higher efficiency regions. Once you've demanded that much air, the compressor cannot actually turn fast enough to build boost without overspinning.
I had an experiment with a front mount S465 on a 6.0 a few years ago with a 220s duration cam. The turbo wouldn't make more than 7psi at full throttle, no matter the boost controller input. Wastegate pinned shut...7psi. Rolling into the throttle at lower RPM I could get quite a bit more boost though it did drop with RPM. But that WOT transient pulled the compressor so far out of the map that it couldn't build boost. The S465 compressor flows very close to what the T70 does. So the turbo being too small remains a very likely possibility. A small turbo that flows 80lb/min can do that on a smaller engine, but nowhere near that on a much larger engine. Unless its a diesel, but those are completely different lol.
I had an experiment with a front mount S465 on a 6.0 a few years ago with a 220s duration cam. The turbo wouldn't make more than 7psi at full throttle, no matter the boost controller input. Wastegate pinned shut...7psi. Rolling into the throttle at lower RPM I could get quite a bit more boost though it did drop with RPM. But that WOT transient pulled the compressor so far out of the map that it couldn't build boost. The S465 compressor flows very close to what the T70 does. So the turbo being too small remains a very likely possibility. A small turbo that flows 80lb/min can do that on a smaller engine, but nowhere near that on a much larger engine. Unless its a diesel, but those are completely different lol.
Thread Starter
Joined: Apr 2011
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From: Sacramento, Ca.
So what about break boosting at part throttle then rolling into it. No matter what I try it just doesn't make more them 6psi. Im going look for a leak maybe tomorrow afternoon
See that is what is peculiar. Not making boost at high load low RPM would make me look for problems elsewhere other than the compressor. How does your wastegate placement look? I've seen turbo kits that have the wastegate placed in a position that provides low resistance to flow relative to the turbo itself, so the exhaust gases bypass the turbo. Kits like that often have intermittent or trouble building boost.
In addition to the boost leak setup you can grab a extra air compressor fitting and a 3/8" hose and 2 clamps. Install the fitting on the hose remove the wastegate and bench test it by hooking the hose/fitting to the bottom of the gate then turn the regulator on the compressor all the way down. hook up the air hose and slowly turn the regulator up to see if the waste gate opens at 5 psi, if it opens earlier you have found the issue. This is how you can bench test it.
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Joined: Apr 2011
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From: Sacramento, Ca.
Here are a few pictures of the kit and Im working on getting a little video
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In addition to the boost leak setup you can grab a extra air compressor fitting and a 3/8" hose and 2 clamps. Install the fitting on the hose remove the wastegate and bench test it by hooking the hose/fitting to the bottom of the gate then turn the regulator on the compressor all the way down. hook up the air hose and slowly turn the regulator up to see if the waste gate opens at 5 psi, if it opens earlier you have found the issue. This is how you can bench test it.
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check your wastegate. I made a rookie mistake along time ago and pumbed the boost controller lines backwards. made the wastegate open way too early
wastegate can also be frozen up and it's hung open, or the valve isn't seating right and leaking
get a pump (hand held) and test it out on the bench so you can watch it work under
chances are the wastegate is bypassing most of the exh. turbo will still "sound" like it working, but no boost.
try pinning the wastegate shut, and see if it makes boost, just be careful to back off the gas when it does!
other issues are a bad exh leak in the pipes leading to the turbo keeping it from flowing the exh gas
a crack in the exh pipe will do this and not be loud enough to notice sometimes
leaky manifold gaskets, ect..... another thing is the turbo shaft could be "bound up" and not spinning freely
if you have a bad center bearing, the wheel resists spinning up.
spin it by hand and see if it's nice and free and doesn't have too much end play
hope this helps
wastegate can also be frozen up and it's hung open, or the valve isn't seating right and leaking
get a pump (hand held) and test it out on the bench so you can watch it work under
chances are the wastegate is bypassing most of the exh. turbo will still "sound" like it working, but no boost.
try pinning the wastegate shut, and see if it makes boost, just be careful to back off the gas when it does!
other issues are a bad exh leak in the pipes leading to the turbo keeping it from flowing the exh gas
a crack in the exh pipe will do this and not be loud enough to notice sometimes
leaky manifold gaskets, ect..... another thing is the turbo shaft could be "bound up" and not spinning freely
if you have a bad center bearing, the wheel resists spinning up.
spin it by hand and see if it's nice and free and doesn't have too much end play
hope this helps
Sure sounds like your pressure is escaping somewhere way before it gets into the engine. I agree with the guys, something is leaking big time. Put the car up on some ramps (or a rack if you're fortunate enough) and go over every connection. I've even done a check by uncoupling the up pipe at the MAF and set my leaf blower to push air into it, then rubbing soapy water on all the coupler connections. Found bubbles blowing and fixed it. I, like the other gent, had a mistake in my routing of the waste gate tubes when I switched to the new kit from my old one. Looking at JGS site, it had a 'high boost' config. I thought, "Well, I *do* want high boost (15 -18 actually)". So I configured it that way. The first time I got out and stomped it in 1st and 2nd, it blew the intermediate charge pipe (between the compressor and the intercooler) completely off the car and sent it spinning in the road behind me. Stunned, I pressed the 'history' button on the AEM True boost. Gulp! 24psi in 2nd gear. I gathered the pipe up, took it home and put the WG in the 'low boost' config and took her out. Well, that was pathetic, it was only 5psi no matter the gear/RPM no matter if I turned the boost controller to the max or not. I was running off the spring only. So, went back to the config for my former Turbosmart 38mm and all is well now. Best of luck to you! Keep us posted what you find.
Thread Starter
Joined: Apr 2011
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From: Sacramento, Ca.
I still need to check for leaks with it pressured. Should I plug the inlet on the turbo and the charge pipe just before the engine and connect pressure to it? That will let me hear the leak? I checked all the clamps and everything seems tight but that wasnt with them pressurized
I didnt know it was 3" all the way to the front. Im beginning to follow the turbos too small theory now. It simply doesnt put out the air to pressurize that much piping for that long.
Double check that 180deg rubber/silicone connector that runs under the panhard bar, We had a problem with one right by the throttle body that was getting sucked in when under boost, we replaced it with an aluminum one and no problems since, the material was too soft combined with heat it was getting sucked in.
I still need to check for leaks with it pressured. Should I plug the inlet on the turbo and the charge pipe just before the engine and connect pressure to it? That will let me hear the leak? I checked all the clamps and everything seems tight but that wasnt with them pressurized
Yes some pressure would bleed down there. But the regulator will be able to make up for it just fine and you wont be able to hear it leaking down so it wont distract you. I pressure tested mine up to 30 psi because I planned to crank up the boost to 25 or so, My cold side was hooked up like it would be normally when driving this will test the complete system including the intake gaskets, you can even check the vacuum lines to ensure they aren't leaking or going to blow off. I have built these and done the test on several occasions on more cars than my own. Any time you remove a coupler to work on the car you should press it up again especially since you have a remote mount nothing worse than blowing a charge pipe off down the road and having to pull over and fix it because its dragging. I had one blow off and get run over by another car which pancaked it, back when I had a remote mount. This will ensure the kit stays together, like I said before if your goal is 10 psi then press it up to 15psi. If it will hold for 20 minutes at a constant pressure over what you plan to run, it will hold for the short bursts at lower pressure.