RSMike

iTrader: (1)

After i run ignition cut (full fuelling, flames out back etc) launch control or i try flat throttle shifting, my car runs like it's slightly missing afterwards.

It seems that the backfires in the exhaust manifold is holding the exhaust valve open slightly, and the hydraulic lifter gets pumped up. This then holds the exhaust valve open slightly, and causes me to lose power.

Does anyone else have this problem?

Is it a faulty Hydraulic lifter?

I've got the same lifters from my evo6 head, and it used to do the same thing.
I have GSC S1 Cams, GSC beehive valve springs, evo9 retainers, 3mm hydralic lifters (cant remember what brand)

Any ideas?

RSMike

iTrader: (1)

Bump for answer/ideas.

has anyone else had this problem with backfiring?

RSMike

iTrader: (1)

anyone?

tscompusa2

iTrader: (22)

are you retarding timing alot to create a form of antilag 2 step? i used to experience bog after doing that with my 2g DSM.

RSMike

iTrader: (1)

timing retard for flat throttle shifting works with as little as -10deg. I've tried it up to -30deg. -10deg ignition still caused backfires in the exhaust system though, i'm not brave enough to try -5deg

There is no bog inbetween shifts, it makes the power super smooth. But there is a slight miss *sometimes* when i flatshift, but only when it backfires. So i'm assuming i've got a possible faulty lifter, or the exhaust valve is being held open with the backfire.

With 2 step launch and ignition cut set on (rather than fuel cut), the problem is a lot worse. It will run with a miss for approx 30-40seconds before it returns to normal operation. This is why we are assuming it's the lifters pumping up and holding open the exhaust valve.

I'd be more than happy to make a video and show you what i mean if you like.
I've checked logs etc, and everything is normal when the car is "missing".

Cheers, Mike

94AWDcoupe

iTrader: (125)

there is no mechanical reason why lifters would pump up. that is simply a function of engine rpm/oil pressure. I would try different plugs. sounds like misfires from fuel fouling the plugs.

RSMike

iTrader: (1)

would you recommend going hotter or colder?
being an evo9 head, i have limited options. i have 7's, 8's and 9's.

with that being said, the only thing thats the same about the heads are the lifters.
And the mechanical reason why this would happen is if the exhaust valve is held open by the backfire, it would cause the lifter to pump up to take the slack.

but i can try launch control in the driveway, shut it down while it's running poorly and check the plugs, that should control it either way.

Cheers, Mike

barneyb

Knock sensor

RSMike

iTrader: (1)

Non Standard Ecu.

Running Link G4 Xtreme (same as Vipec). Knock sensor not currently connected.

barneyb

Well, okay, but driving without a knock sensor doesn't seem like a good idea to me.

RSMike

iTrader: (1)

I have talked to another workshop here in NZ, and they have confirmed they have had this problem on another 4g63 engine.
It is from the seat pressure not being high enough, and the lifter pumps up because the valve cannot sit on the seat with the backfires in the ports etc.

Ways to solve it is higher seat pressure valves and/or solid lifters.

I'm using GSC Beehive springs with S1 cams. Stock seats and retainers.
I see on their website they are 68lbs installed.

http://www.power-division.com/produc...cat=283&page=1

Maybe kiggly springs will fix the problem?

CammedEvo

iTrader: (5)

AWDCoupe's right... But please leakdown test you're car before you go around slamming gsc for no reason.

Does a hotter plug solve it?
Seems as if getting to aggressive with the anti-lag and covering the plugs and then the car soon after clears them off.

Wonder how your EGT's are during this madness.. Question tho why the heck would you need to run so aggressive between shifts esp on a stock turbo car!

Also those rapid changes in timing during shifts.. man my car wouldn't like me for that.

RSMike

iTrader: (1)

Ok i'll play along.

If it is my plugs getting fouled, how do they "unfoul"?
Hotter plugs (evo9 heat range 9) plugs did not solve this.

The flat throttle shifting is much smoother than normal shifting. I think it would pickup time on the quarter mile for sure. As i said in the other posts, i tried only -10deg timing and it shifted nicely, but it would start to miss.

Rapid changes in timing during shifts? i fail to see the reasoning for that comment?

Sorry Jerry, but i'm going to disagree with you on this one.
If my seat pressure is too low, and the valve is held open, the lifter will pump up to take the slack in the valvetrain. Thats what it's designed to do.

I wasn't Bagging GSC as a whole, i was just stating that the seat pressure when the valve springs are installed is not very high.

I also forgot to add that if you make it missfire (via launch control) then turn off the car right away, wait for 1min then restart it, it runs normally.
This is because the lifters pressure is bleeding off back to the normal position.
If it was a fouled plug, wouldn't it continue to miss because the plugs would still be fouled?

RSMike

iTrader: (1)

Ok i just got an email back from GSC, they said the 5041 kit (springs, seats and retainers) is what they suggest for my application. This has a higher seat pressure. (95lbs)
The 5039 (springs only) wasn't designed for flat throttle shifting and antilag. (68lbs)
Thanks for your response.