Thread: Think I went with too big of a turbo...

I think I've finally hit the "too big of a turbo to drive daily" stage, even with a VE. I started out with 5-6psi, just put in a 12 PSI spring and it's only boosting 10 psi. But even at 10 psi the car doesn't feel or seem any faster. My external wastegate line is running directly from the turbo, so I must have a leak/serious pressure drop and hence it looses the 2 psi.

The car has fairly nice torque out of boost, the low cams really rock for daily driving, but when boost kicks in the power is very NA like, then VVL kicks in and it still feels the same.

I start building boost at around 2k with full boost at around 3,500-4,000 RPM. Going 70mph in 5th gear which is 3,100rpm on the P11, if I WOT it it takes about 3-4 seconds to hit 10psi. VVL kicks in at 4,700rpm, but I've been adjusting it and seeing what the best switch point is.

My buddy has an 09 Legacy 3.0R, I couldn't even keep up with him, and he has an automatic. I personally feel like there is something wrong, but maybe the turbo is just too big and is not hitting it's potential at 10-12 psi.

I am running a log manifold, 3" exhaust, and front mount intercooler. Log manifolds tend to let the turbo spool faster and I thought they were torquer then tubular. I don't even feel like bothering with a tubular manifold, and simply go back to a T2 turbo.

The turbo is Precision 5431 CEA (Billet wheel) 0.63 A/R T3 Turbo





Update: The problems turns out to be the SR20VE cams and a restrictive exhaust manifold (log). SR20VE cams have 48* of overlap, which causes major reversion with restrictive exhausts, which leads to major loss of power and detonation.

Two solutions to this problem, run VET cams, which have 13* of overlap, or use a tubular free flowing manifold.

I wish I could help you, bud. Someone will for sure.

If I did it over I'd go 2860RS w/custom intake manifold and S4 cams. I'd be making same power I am now at same boost level w/quicker spool for better street-ability.

What does boost leak test say? Also, just curious, do you notice any overheating issues with the downpipe and exhaust side of the turbo so close to the radiator?

I've got 10 bucks on "you'll love it if you ditch that log manifold."

How much timing do you have in it?

At 10-12psi on that turbo you should be absolutely roasting the tires 1st 2nd and maybe beginning of 3rd. Engage the vvl sooner. Like 3500 rpm, the low lobes are just too small to spool the turbo up faster. Also i know you said you were very very conservative on the timing. Im thinking that is your problem. Can you send me a snapshot of your timing map? If you have the ability to monitor knock do some pulls and log it. Add back timing until you start seeing a slight bit of knock then back it off to the last number without knock. You will be very very surprised at what even 1 deg of timing will do as far as power goes. To lose that that Suby is bad. I know the car is heavy but it should be running alot harder. Even 200whp in a p11 should beat that suby. Either bad boost leak or timing issue.

No worried bud, With constant cooling issues with AC I'm so tempted just go NA. That way I know it should and will be slow, right now with the amount of parts I have in here it should be much faster.



I wouldn't mind even a journal-ed T28, I liked my GTiR on the DET, but I would me maxing it out on the VE/300whp.

I'm going to borrow my dad's compressor tomorrow, I just got back from a 4 hour drive and was just annoyed by the weakness. The car feels fine on the highway, but that's due to the low cam not due to boost.

I am having heafty overheating issues with AC. I just installed a Koyo and it was fine and dandy until one of my slim fans wires melted off so overheating issues started again.

After I do a leak test I plan on heat wrapping the downpipe and a turbo blanket, lastly I'm wanting to wrap the piping to reduce heat soak.



I just don't see how a log manifold t3, external gated, with higher psi, 3" exhaust would perform worse then a Avenir mani with T28 and internal gate, and 2.5" exhaust.



As much as I can run at 10 psi. With Tunercode you can see the knock counts on a nice map. Timing is fairly low, simply because I'm running 10.3:1 CR.

In no way shape or form is the turbo too big for the ve. It wont spool like a t28 but should still have a fat powerband if running correctly. I think you need to add in timing monitoring knock closely have a passenger or something with you looking at the laptop watching knock. Add in timing. You will be surprised what just a bit of timing will do.

I've tried kicking VVL at 4k, that is kind of high still. When I would engage it at 5k, it would flow the smoothest, guess I'll try 3,500 tomorrow .

I'm getting knock even at timing at 0* at 10 psi, mainly around 4000-4400 rpm. I took a fairly base VE-T timing map and have been building on it. I could run quite some timing in low load, but had to pull back a ton of timing in 15Hg+ columns. So it does seem like it's fairly picky on timing, could very well be because of the ported head and intake manifold.

When that turbo spools, it shouldn't feel NA like AT ALL.

def go with a boost leak test. Also recheck the spring on the waste gate. could be opening prematurely.

Also, if you have the fuel to do it, that turbo isnt going to show its ass untill 15+ PSI

Oh BTW, is that your boost gauge line running into the air intake below the wipers??

-Seth