hmm, i still get backfire or popping when on boost and WoT at around the 5,500 rpm mark..

anyone know why? i just find it odd..

cheer,
simon.

MY99 uk, Tek2.5, K&N Induction Kit, Forge VTA (Blue Spring), Full De-Cat.

[Edited by snowcrash - 1/20/2003 11:17:50 PM]

 

Is it a misfire as in the car is not pulling smoothly through that area or is it just a pop from the exhaust?

How long/how many miles have the spark plugs done? What gap are they at?

Could your VTA be leaking? It would not be the first Forge VTA with a blue spring I have heard of leaking and causing a problem They just don't mix with a car running a MAF sensor IMHO, never mind the problem of oil quality degradation that Mr Felstead pointed out. I'd rather have my bearings lubricated with oil than oil/fuel mixture

Suggestions (in this order)...

Refit the OEM DV
Regap and check condition of spark plugs suggest NGK PFR 7B gapped at 0.7mm
Check MAF sensor
Check for vacuum leaks
Try a standard ECU

 

Something is making it run rich, the popping etc is due to unburnt fuel getting into the exhaust, plugs are favourite .. as John mentioned PFR7B's gapped at 0.7mm. Have a close look at the ones you take out, the colour and condition of each will tell you which cylinder was suffering.

Bob

 

If it sounds good leave it alone!

 

That's an irresponsible statement, LegacyTurbs....

I've seen similar - a very low reading MAF was the first issue (which I suspect 'did' for the plugs - car was worth 240ps....standard!). He then had similar to the above a few hundred k's after remap, followed quickly by stuttering while spooling.

I now recommend PFR7B's at next service if MAF OK, and before remap if MAF already under-reading......

Richard

 

What can i say, I'm just a backfire junkie POP!

 

i've noticed it over a week or so, and i've swapped springs in the VTA (it's currently on yellow, but was on red also..) ..

john you don't reckon the DV is any good...

also something else that happened today, was (i put the yellow spring in) and the turbo went to almost or on 1.3bar on WoT in 4th i immediatly let off accelerator.. but i aint seen that before, i'm assuming its due to the yellow spring..

i also had the car dyno'ed a few weeks ago at powerstation, i'll upload the graph, but the car had a dip in power at the top (5,500rpm area from memory - i'll upload the image tonight/tomorrow..)

cheers,

simon.

 

Dips in power on dynos are not uncommon because of heatsoak and unreaalistic boost behaviour.

I think if this is a recent problem which has developed then you are looking at something like plugs, leaks etc rather than an ECU issue.

 

i think the plugs were changed around 35,000 miles (from memory) and the car is now just over 45,000...

john will deltadash logs of the car aid in working out the backfiring on WoT?

 

DD log would be helpful. After 10000 miles at modified boost levels my plug gap had widened, and I change plugs at approximately half the official service interval and feel the benefit. Maybe on a standard car that would be complete overkill. Considering that you are running higher boost, I think plugs as detailed before may help.

Basically you need to running the correct fuelling and a good spark. If the fuelling is too rich there is probably a sensor problem or a leak, since the fuel values in the map are similar to the leanest of the standard ECUs (AE800 or AE801, leaner than AE802 or AE801 PPP or Tek 2), and whilst safe and arguably excessively rich, these alone should not cause a misfire if everything is working properly. An AE802 with a fuel pump does not misfire because of rich mixtures... if anything would that would.

 

i'll have to try and get hold of phil.. or progress my plans of home made deltadash equivilent

 

The car can run rich for several reasons ... the main thing to consider here is what is the most likely given its at WOT and at 5500 or so, the ecu will actually add fuel itself ... when it dets so if the ecu thinks the car is detting it will pull timing and add fuel, quite alot possibly, which would make the car shudder/stutter etc. A dip in the timing curve up there when the car is on boost and has been for maybe 1500 rpm at least with no problem would seem to hint at that possibility.

Definately a case for a Deltadash log !!

 

bob / john - out of interest dawes afr is always displaying blue at that point (around 5,500rpm - all they way up the boost range... even the time it was around 1.3bar )

currently wondering if phil is around... hmm

[Edited by snowcrash - 1/22/2003 12:07:19 AM]

 

Can you answer my original question, sorry if I missed the answer:

Is it a misfire as in the car is not pulling smoothly through that area or is it just a pop from the exhaust?

Blue means rich, don't know how rich. You need a log.

 

pop i would say..


also noticed again it hit 1.3 bar in 2nd,3rd and 4th and not on WoT but on 1/2foot down acceleration (i rarely use WoT)..

 

If it is hitting 1.3 bar on part throttle in second it will probably be fuel cutting in 4th.

You need the car logged to see what is going on we are only guessing otherwise.

 

thats next on my list of stuff to get john... gotta catch phil ..

 

john, i've noticed it goes upto 1.3 when changing gear on boost and (obviously) keeping foot down to accelerate up through gears...

i think the boost issue is due to the DV spring.. i've got spacers and other springs to try so will put them in... i aint got hold of phil (babber) yet to do a DD - i dunno where he is, i suspect he is testing sideways's focusRS...

anyway i'll keep ya posted.

 

Slightly alarmed at the approach to sorting out the DV springs My thinking would be to use the dump valve to relieve the compressor wheel of shock loading on lift off and to help with part throttle smoothness and assist in not surging the turbo to bits. I know some do try to "tune" their dumpvalves for noise and/or flames. Strong caution advised!

 

well the overboost has only started since i put in the yellow spring (to see what it's like - too much like escort cossie bollox, and makes the car difficult to control/jumpey and i've noticed it overboosts ). I'll put the blue one in in the morning and try and replecate the overboost... and see what happens on the way to work..

[Edited by snowcrash - 1/23/2003 12:02:01 AM]

 

ok, i put the red spring back in.. the car is less jumpy and more stable ... (the car has been on the red spring for the last 9 months or so)

boost hitting 1.2bar most of the time (at one point - changing from 2nd -> 3rd i thought it went over 1.3bar - the rate the needle jumped shocked me!). I dunno if it's done that b4, and i've not noticed...

 

What does your orignal DV do?

Usual plan for sorting overboost - clean restrictor/solenoid, check wastegate movement.

If it still overboosts enlarge the restrictor or use a restrictor valve in its place.

If the car started overboosting and before was OK go back to the last known good.

Some are fine until a silicon pipe, induction kit, decat exhaust etc and then overboost.

 

it is a forge VTA dump valve...

forge will give you different springs (to make different sounds etc.) for the DV :

RED = chatter (hard spring)
BLUE= phsssst (normal spring)
YELLOW= phssssssssssst (weak spring)

they also sent me some spacer to compress the springs (for the blue/yellow one - to make the car judder less).

they also told me the yellow one is prone to causing idle problems.. (only thing i noticed was that the car idle'd about 100rpm higher than usual)

i'm pop around to phil's house tonight to see if he is in and can Deltadash the car..

the car is currently setup to last known good.

[Edited by snowcrash - 1/23/2003 4:10:43 PM]

 

I was making a subtle suggestion to try the original

 

Lol!

 

hmm, lol will have to hunt in ze dump (aka garage... )

john - i thought have VTA dv's weren't that much of an issue on scoobs... i thought induction kits were the problem causers...??

 

I think they are evil on a MAF based car

 

lol @ john...

currently waiting for servers to reboot then i can go home and hunt around garage...

 

going to meet up with phil tomorrow afternoon (hopefully [work permitting]) and do a Deltadash...

still overboosting on the way home - hitting 1.3bar again