meanteg

Engine: B18c1
Wastegate: Tial 40mm
AEM EMS

Here's my problem :

I run with no boost controller with a 1 BAR spring in my wastegate. Boost has always been steady at 15-16 PSI.

But now, without changing anything the engine started to do some weird things. First I noticed that sometimes the boost goes higher than 15 psi. I do one acceleration : 15 PSI. another acceleration , it spikes to 19 PSI and lacks a lot of power at the same time. goes back to 15. Another acceleration, 15 PSI . wtf ?


vacuum leak maybe ?

Oh yeah, the engine also seems to -misfire maybe ?- ( lacks power ) at high rpm, but only about 1 time out of 5 . I don't know if it's related to the first problem.

Any help would be greatly appreciated.




Modified by meanteg at 3:13 AM 9/4/2003

meanteg

ttt

83Rabbit

check and make sure your wastegate is not sticking and is functioning properly. for prob 1.

Also check for detonation, that may account for the missfire type problem. Whats your timing at, and the retard for boost? are you running 93 octane? injectors and fuel filter clean?

83Rabbit

i mean its a long shot but your wastegate could be sticking and the higher boost pressure causing your car to start pinging, that would account for the lack of power when it spikes and the raise in boost pressure sporadically

yellowturbo

Hi Fred, I had the same problem ...but it seems to be related ( the boost spike ) to the ambient outside temperature...like last night it was really cold and the boost did 18 psi instead of 15psi ??? Sometime when it occur my car do a backfire du to the bad timing at this level of boost I think... So I have no awnser for you but it could help me too if someone have one !!!

83Rabbit

backfire...theres an idea...

yellowturbo

oh yeah excuse me ...misfire im not use to speak english eheh !!! : )

83Rabbit

oh no, i was wondering how a backfire would affect boost pressure....

meanteg

The problem is not temperature related that's for sure. I can do for example, 5 accelerations in a row with no problem, then the 6th time it does that problem. Then rirght after I can do another 5 accelerations before de problem comes back ..

I did a few WOT accecerations today while waiting for the problem to happen. When it happened, i cut the ignition and checked the plugs. Brown chocolate with no sign of detonation at all.

And I noticed that then the problen occured, the engine was lacking power AND the boost gauge was at 18-19 PSI.

1- How can the engine boost more and have less power at the same time ?

2-83Rabbit, How do I check if the wastegate is sticking ?

meanteg

Didn't find the problem yet, but I'm getting closer to fixing it.

The problem is deninitely with the fire. The boost is set @ 15 PSI. When I accelerate at wot, the power falls down at about 7000 rpm and at the same time the boost spikes.

The plugs still look perfect tho.

I think that when the ignition doesn't fire, the unburnt fuel explodes in the turbine, causing the boost spike. Does that makes any sense ?

Anyone would know frome where this misfire problem is coming.

Any advice will be appreciated. thanks

meanteg

Could it be a defective msd 6al or blaster coil ?

dubracr18t

what are your plugs gapped to? Maybe with the extra boost, they're gapped too wide and the spark is going out?

meanteg

It's not the plugs. They're brand new ngk BKR7e , and I tried to gap them at .030, .028, and .025, no success.

scatuli

is there any chance thatyou are leaning out?

meanteg

No chance in one million. The car was dyno tuned with a wideband, 12.5:1 all the way. Plus the plugs have a perfect chocolate brown color.

Is it possible that the timing is retarded too much on boost ?

meanteg

Problem solved !! Defective knock sensor, was sending false alarms to the EMS. The EMS was set to keep 25% of the fuel and retard the ignition 25 degrees !