My car does this strange thing when it reaches wastegate pressure of 15psi. It starts sputtering as if the WG opens and closes very quick, but in the same time the car bogs and it doesnt accelerate. The CEL light comes on for knock and I let off the gas. If I stomp it sometime it would blow black smoke from the exhaust.

current setup:

2.4L 10.5:1 CR
HX35 on bolt on housing
DSM Link v.3
External MVS at 14.7psi
Tial 50mm BOV
rewired pump


The only thing that comes to my mind is that it runs out of fuel or something.


Any input would be appreciated.

Boost leak test? Do you have a wideband? What are the AFRs at 15psi? MBC?

No MBC. AFR are normal - mid to low 11s till about 40% throttle. Car hasnt been WOTed cuz It hits WG pressure at 40% and starts sputtering.


Havent done BLT in some time.

What fuel are you running? Have you tuned the car for 11-ish AFRs? I think it's time to post a log at this point.

Yea you posted nothing really. Are those all your mode? The way u listed the rewired pump would make me think you have no injectors or pump. If that's the case I think its pretty obvious what's happening. Are you speed density? You need to post a lot more info on your setup as well as a log.j

Lots of blow off valves will flutter open and closed at part throttle boost. Please post a log, and full mod list.

I'll get a log tomorrow. My axle spilled grease all over and didnt want to push it tonite.

Full mod list.

2.4L 4g64 10.5:1 CR.
220 psi across, pulls about 22 inch/hg
PVC removed
Balance shaft eliminated
Evo 3 intake manifold
1g NT rebuilt TB
TIAL 50mm BOV - 7psi spring.
TIAL MVS 15 psi spring - recirced to DP
8 blade HX35 in BEP bolt on housing
BEP/HAFE exhaust manifold
3'' Downpipe
High flow cat
2.5'' cat-back with 1 resonator and a muffler
DSM link V3 lite running on stock MAF
RC 680 injectors/Stock rail.
Evo 9 FPR
Fuelab filter
NGK spark plug gapped to .025''

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Do you remember how many lb/min u log? I doubt you are overshooting 680's at 15psi but I guess its possible. They should support 400 flywheel hp.

Well here it is the log. 63 sec in as it reaches 13 psi and the WG starts to open, it starts knocking and the WG flutters.

62.87 sec is right before it starts knocking. 43% throttle

According to your narrow band you go lean there. It's very hard tuning part throttle pulls. A full wot pull is best. Just watch for knock. I set my cel to come on at 5* and let off if it comes on.

yeap, I see it. The O2 voltage drops to 0.1 V and it starts knocking.

Th most I'v gone is 47% throttle and it starts jerking back and forth. I cant wot it right now.

I wished I had fuel pressure gauge in the cabin to see if it drops when this happens.

Do you think the fuel pump is getting overrun ?

It's much easier to dial in on a wot pull. Lots of weird things can happen at part throttle. The bov can leak, a lot more than at wot because of the pressure differential across the throttle plate at high load part throttle.

donniekak said:

It's much easier to dial in on a wot pull. Lots of weird things can happen at part throttle. The bov can leak, a lot more than at wot because of the pressure differential across the throttle plate at high load part throttle.

Click to expand...

Ok here is the WOT pull in 5th gear starting around 2.5k rpms

I replaced the fuel pump with supra Denso pump and loaded stock Evo 8 maps. It pulled 1.5 degree of knock, but the car stil jerked when it hit WG pressure.

So are you running E-85 with a 10.5:1 CR?

93 octane

Anyone?

Just wanted to follow up on this. I've solved the problem which turned out to be very simple.that I still cant believe I overlooked this, and to get on point I forgot to gap the spark plugs so i was getting spark blow out. I installed the plugs with the gap they come from the store and as soon as I pulled the first one I was like........ mf-er . She runs good now, thanks guys.

Thanks for posting a solution! TOO many people don't and leave future searchers with the same issue, hanging.