I can’t think of what else to check or do to solve thisproblem. The problem is I can’t get the car to make commanded boost. It makes about 1.1bar now with commanded boost being 1.3bar on a set of K24/20G billets. I’m going to list the history as simple as Ican with only relevant info to try one last time to see if anyone has anyfurther ideas before I give up.

Last year with the stock turbos and 1bar tune I pinched the hoses going to the wastegate actuators and the car still made only 1bar of boost when in theory it should have overboosted like crazy.

This year I installed a set of K24/20G turbos and was only making 1 bar of boost. So this is what Ihave done…

1- Boost leak

Boost leak test at the intake of the turbo and blocked off intake of other turbo. (Car held 25psi)

2- Divereter valves

a)Made sure they were not leaking. (they were finebut replaced anyway)

b)Thought the N249 valve might be bad so Ibypassed it and took boost/vacuum right from intake manifold. (No change)

3- Wastegate Actuators and N75

a)Thought the N75 was bad so I bypassed it which should make me over boost like crazy since the actuators are getting no signal(Made no difference)

b)Thought exhaust backpressure was opening up the internal wastegate flap so I set out to find new wastegate actuators. 32Krazy! Saw my post and sent me a set of 1bar actuators for free!!!! He wouldn’t eventell me the shipping costs for me to pay that!! To say the least I was very thankful. I put those on yesterday. (madeno difference L)

c)Wired the wastegate actuators shut so theyphysically cannot open. Made a small difference. I now see 1.1bar and sometimes 1.2bar. I do not think this has anything to do with my issue though. I think I just see more boost because the turbos are working like crazy to meet commanded boost so with the wastegate flaps not able to open at all it helped build a bit more boost. That’s my theory anyway.


4- Clogged cats

Removed exhaust and cats are OK. Tested exhaust pressure before the cats andit was well under 1psi so it is within spec.


So the only things I can think of left to do is:

1- Remove the turbo intake pipes and replace them with ashort hard tube with a screen on it to prevent crap from going into the turbosduring test drive. This would eliminatethe possibility that the intake tubes are collapsing in on themselves. I don’t think this is happening but at thispoint I have to check it.

2- Bypass the diverter valve system completely to test if for some reason they are bleeding off the boost (even though I confirmed theyare physically good and the issue has nothing to do with the N249 that controls them.

3- Set the car on fire

Thanks for any help!

 

Lack of full boost is often due to a boost leak. You have to be sure you have eliminated that.

Next the stock car's DME only allows enough boost to satisfy the torque demanded by the driver. If 0.5 bar of boost has the engine making the torque the driver wants that's all the boost the engine will make.

I'm not sure your car with a "tune" has this same, uh, rule in place.

My point is the engine may be only making 1.1 or 1.2 bar boost because the DME doesn't believe it needs to make any more boost.

At higher boost gasoline becomes even more critical. Are you running the right octane? I'd think with that much boost you should be running race gasoline, as the stock engine with just 0.7 bar (nominal) boost requires 93 octane. 'course, even in CA with just 91 octane my Turbo makes 0.7 bar when I give it the big whip.

And there are of course the MAF, plugs and coils and O2 sensors. Lots of boost requires these components work at optimum performance.

With a tuned engine these components work much harder and as a result suffer accelerated degradation.

I'm not saying these all need to be replaced but you may be facing that.

Last but not least if you are going to set fire to the car remove those waste gate actuator flaps and pass them on.