My car has been acting weird lately. Anything above 6k and the power goes to ****. SO i've been shifting below and it works fine. So, I hit the rollers today to try to tune it out and this is what I found.

When at good boost like 18+ It hold until about 5k where i get 275whp after that boost drops slightly and it holds the power until 6k. @ 6k it immidiatly drops off hard. You can hear and feel it. It sounds almost like a revlimiter. When it happens the afr stays correct and it knocks about a degree. If you look at the log you can barely notice anything but when you look at the dyno graph and listed to the car there is clearly something wrong.

So, i took it back to 10psi. I got about 230whp and it kept pulling to redline. No sign of any problem. I checked the plugs. They are all gapped at .28 (bkr7E coppers)

There doesn't seem to any boost leaks the charge piping is real short. I am just stumped. Anyone have any ideas?

My wastegate is a synapse engineering synchronic wastegate, maybe the source of the problem? I am also still using a draw through MAF setup IDK just ideas.

Help me out guys...

 

Isn't .028 kind of small for the plug gap?

 

It idles fine with it. we tried them bigger and the problem remained if not got worse.

 

.028 if fine for that setup.
Sounds like either your waste gate spring is too low (need at least a 1 bar so it doesnt' drop off like that), fuel pressure problem, or your turbo is just running out of steam. whats the a/r of your hotside

 

Your turbo is running out of steam. Turn the boost back up. I bet when you hit 7k at high boost your making 10 psi just like you do on low boost.

 

The turbo is plenty capable. I know because I've overboosted a few times, It's a hell of a ride until the charge pipes blow off. I know that has more in it.

It's only a .48 hotside but it should be cutting out at over 320 not at 280hp.

The IDC is only in the 60's so IDK it could be a feul pressure problem. Now that you mention it, I have never changed my fuel filter. I know it's passed due. Maybe that could be holding back some fuel flow at high boost and screwing me up?!?

The wastegate has been giving my trouble from the start. I'm going to look into other options.

Keep the idea coming ... thanks guys!!!

 

Do you have pictures of your dyno graphs?

 

No pics. But it goes from gradually dropping off at 5k to spiking downward at 6k.

 

well there is your problem man... the .48 hotside... waaay too small. need a .57 or a .63 to keep any top end pull in that thing

 

That might be an issue holding me back, but it's not this problem right here. The car just hits a wall. It's almost like an ignition revlimiter. It just dumps power pops and shoots flames. It's very violent.

Also I get more boost on the street than on the dyno. Something is seriously wrong.

 

Did you plot out the compressor map???? Sounds like your turbo is crossing a surge line or something.

 

Yeah I am no where near the surge line. Way closer to the stall line. But, at my boost and rpms it should be right in the sweet spot.

 

yeah my friend car does that (more boost on street) dunno why, my car always stayed where I set it.
sound like a fueling issue... happen @5800 rpm?

 

The boost starts to drop at 5k (think that an unrelated wastegate issue) but the power dives right at 6k on the dot.