NOLA Speed and Style

Author Topic: Modified ALH : acceleration backfires ??  (Read 150 times)

July 01, 2019, 01:04:08 pm

Faztco

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Modified ALH : acceleration backfires ??
« on: July 01, 2019, 01:04:08 pm »
Hello All : I need feedback from smarter people than me for an issue I am trying to figure out. Heres what I am working with : 2002 ALH , rebored,fully studded, new head heavily ported, Colt stage 3 Cam, 1752 Hybrid Turbo, SS 3" exhaust , Bosio 520 nozzles ,PD intake EGR delete , FMIC , 3 bar sensor ,new MAF , Malone stage 4 tune ,rover Blow by separator . Timing set to slightly center high with VCDS , IQ set to 5 , 11MM IP & DRW 6 speed conversion. The issue I am experiencing is usually in 3rd gear ( spirited ) pulling from 2500 - 3K I get a backfire, and it seems to go into the intake because I then get no power & alot of smoke until the "exhaust" works its way through the cylinders and the engine recovers again...and it again runs like normal. Below and above this RPM range everything is fine. I have no mileage issues and have had the car over 200KM/Hr ( testing)with no fuel issues. I looked at the LP relief valve in the IP and yes, it was out half way, pressed it back and replaced. The only Mod I have not done yet is the PD tank pump addition... which is coming up. I`m relatively certain Cam timing is deal on . I would really like to here from someone else who experienced this that info would be greatly appreciated, Thank you.



Reply #1July 01, 2019, 03:12:10 pm

Faztco

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Re: Modified ALH : acceleration backfires ??
« Reply #1 on: July 01, 2019, 03:12:10 pm »
 Additionally : engine has only 5K on complete rebuild , Boost gauge can go to 30 PSI+  ( If I tromp hard enough ) . It sort of feels like the pulling power is linear up until a very slight lag in power before the backfire happens... then like I said - you look in the mirror and there is lots of smoke and no power till it "Clears" through forward motion and the power comes back. Anyone else delt with this issue?

Reply #2July 04, 2019, 01:43:23 pm

Faztco

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Re: Modified ALH : acceleration backfires ??
« Reply #2 on: July 04, 2019, 01:43:23 pm »
OK...made an adjustment ; lengthened the rod one turn on the Turbo , Just took a 1000 KM trip from the Okanagan to the Coast and back, now - no more backfires, power seems good - with a slight and I mean very slight   " falling on its face" like a carb would do running out of fuel on hard acceleration - at higher RPMs , and I attribute this to not having my PD intank pump installed yet. only thing to do some research on with this new adjustment is that I notice the EXHAUST Temperatures throughout the RPM range are Higher. Normal driving it reads EGT at 300 Degrees F at almost no boost, and spiking the throttle I can reach 1200 Degrees F  at  32 PSI Boost ( Briefly). Car feels good pulling but does expel a noticeable amount of smoke on hard Acceleration. When I get my VCDS back ( seems like its always borrowed out ) I will play with IQ amount ( currently at 5.0 ) and see what difference that makes. I know Heat makes power so the Turbo temperatures dont bother me. Stay tuned ...Mike

Reply #3July 04, 2019, 10:40:40 pm

ORCoaster

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Re: Modified ALH : acceleration backfires ??
« Reply #3 on: July 04, 2019, 10:40:40 pm »
EGTs sound normal to me.  I cruise in the 400 range most city driving and 600 if doing 50 on the hwy.  Put the foot down hard to make a long hill in fourth and I will see 1200 at the top of the hill.  All within range I say.

Get the VCDS back and adjust the fuel and I think you will be fine.
Turbo and Exhaust finally on, Time for tuning!

 

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