hey guys, we went to dyno my friend's 88 FC today. it has a stock s5 turbo, 2.5" exhaust, stock TMIC. i tuned it the other night on the street on 6.5psi and all was well, no problems, high 10's/low11's AFR, no hesitations. well, we went to the dyno today to try to run 12psi and tune the AFR's to the low 11's and i was getting a nasty "plink" sound as soon as we'd get to about 4500rpms at ~11psi. i rezero'd the timing to double check that i didnt have it too advanced and the timing zero'd out lined up, locked at -5 it was right on the yellow -5 mark on the pulley. i docked the timing back 6* across the board just to verify that i didnt have the ignition too advanced and the problem actually got worse... i am guessing this was bad (and audible) pre-ignition, so at that point we decided to cut the dyno time short and make sure we didnt blow anything up

SO, i was wondering if someone could check out my ignition settings and tell me what they think. the advance is relatively conservative and the trail split is very conservative, so i am really confused and dont know what could be causing this problem. i will post the whole map later when we can get it off of the laptop.

here is the Ingition Setup menu
trigger angle (deg btdc) 58
tooth offset 11
spark output constant charge
spark edge falling
constant period 3.5

here is the Trigger Setup menu:
trigger angle (deg btdc) 58
trigger type multitooth
teeth no 24 tooth offset 11
trigger input internal reluctor reluctor gain 1 motronic filter 0
trigger edge falling
home input internal reluctor reluctor gain 1
home edge falling

at 12psi i have the advance at about 14*
at 12psi i have the trail split at 14*

 

This is on an X right? Sounds like the exact same issue we had with Danny's car after the ECU came back from Oz.

 

It only happened when we turned the boost up to 11psi... when we kept it at 7psi it never did it.

 

ive got an e6k car running like that, its happy as a clam. around the tq peak its 12btdc, climbing to 14btdc, splits like 15.

how are your plug wires?

 

The plug wires are good.

 

yeah its an e6x.i have never had this problem with an e6k before. i'm starting to think its an e6x problem...


what i'm wondering is, how do the ignition settings look?
i know the advance and split is plenty conservative, but whats confusing me is when i RETARDED the advance by 6* across the board, the problem got WORSE. this has me vexed

 

doesn't the e6x have a known ignition problem?

 

yeah but apparently it was fixed long ago, as far as i know

 

High 10s? I had these issues when my engine was in the 10s AFR wise, then I brought it to the 11s and it went away.

 

after talking with BDC for a while today about our problem he seems to think that its a mismatched pulley and boss problem. i wasnt aware that this mismatch could be AS big of a deal as it can, but Brian said that he has seen crank marks be 15* plus or minus what they should be. even though the pulley can only bolt on one way, it could have been assembled on a different motor that had the same holes drilled 15* over (either advanced or retarded) i have heard of this before, but i wasnt aware that the marks could be that far off...

he recommended added +15 to the trigger angle, which would retard the base timing 15* from where it is currently. since i was thinking that it seemed we were running wayyyy too much timing somehow, this seems like it could definitely be the culprit. brian's idea could confirm that the pully/hub mismatch is the problem, in which cause we would have to get a racingbeat aftermarket main pulley with the timing marks on it.
if that's not the case, we would have to look into the trigger signal and setup (and maybe a haltech problem?) and see if the rpms jump at all when this problem happens, but i didnt notice this when we were at the dyno, so i dont think thats the problem.

 

i have had hesitations on the dyno with my cars before with the AFR"s in the 10's, hesitations that go away when you get the AFR up a little leaner, but this is a loud TINK about 1 or 2 seconds into the pull with a huge jerk in the power. its very bad.

 

Sound like the keebler elf hitting your motor with a ball peen hammer?

 

...without leaving any cookies!!! :/

B

 

I've been looking into this pulley/boss issue and I've found that racingbeat does have a pulley (http://www.racingbeat.com/resultset....rtNumber=11469) they sell that is aftermarket. If I were to get this would this solve my mismatch issue? Also, racingbeat doesn't recommend this for street cars which my car is definately a daily driver. Am I going to see any negative effects by using this aftermarket pulley?

 

Interestingly enough, that's the same one I sometimes use to make known-good timing marks on an otherwise questionable front pulley/hub pair.

B

 

it would be fine if they left cookies! especially the ones with the chocolate stripes, those are good....

seriously though on my t2, plugs and wires fixed my 6200ish hesitation, the real fix was leaning it out a bit, too rich is too rich

 

I was low 11's high 10's at high rpms. I'm gonna wait for a bit and do some more testing to reassure that the pulley is the issue before I make any moves. Guess I'll be running vacuum for a bit.

 

Also, I have new plugs and wires already. Ludwig posted a way of finding TDC by looking through the trailing plug holes for the apex seal and once you see them then you mark that on the pulley for TDC. Has anyone else tried this method?? Here's a link to the website with the instructions. http://www.teamfc3s.org/info/article...fying.html#TDC

 

Generally speaking, this can be helpful, but in terms of the exactness that's required under higher loads, don't even think about it.

B

 

AKA get the racingbeat pulley.

 

yeah pretty much.

i'm sure that RB pulley is keyed with a very very small tolerance.