mark kibort

what are you calculating here? fuel pressure drop when vacuum applied?
thats usually about 3 psi as you will see.

BC

AO

Well ****... The new filter helped, but that wasn't the smoking gun. With Ken's LH chip, I am solidly in the 14's with an occasional 15 at WOT. Idle and cruise seem okay (makes sense because of the O2 loop), but WOT is still lean.

I put the stock LH back on at I hit low 12's mostly and saw an occasion 11. Timing belt light came back on so I had to be nice driving it home. More on that below.

I traced every inch of the line from the tank to the engine and everything looks fine. No kinks whatsoever. I was kind of hoping I would find something by the firewall, but that was all good. So at this point, I don't know what else it could be. Front damper is the only thing left between the pump and the fuel rails that could be restricting things.

What is the behavior if you disconnect the vacuum from the damper? Is there any way to test it?

I could order a new damper, but I won't get it until Monday at this point, and I'll be out of town all next week. So, for now, I'll continue to use the stock LH chip and Ken's EZF chip.

My rebuilt Accusump will be here today, and I'm going to permanently install a WBO2 in the car, so that'll keep me busy tonight and probably tomorrow.

Timing Belt:
After my last run, and having the TB light come on, I pulled the timing belt cover off and checked things out. Belt was fine, but found the tensioned was dry (not leaked, just never filled by the PO's mech. ) and something is wonkly with the tensioner alarm. The alarm is right on the edge of the tension window. I could get it to turn off by slightly over-tightening the belt. Obviously I don't want that, so for now, I set the tension properly and grounded the tensioner alarm. I plan to put Ken's tensioner on there this winter.

So although I had checked tension and fixed that it was off a tooth before driving it this season, I had assumed the tensioner was good. It wasn't. What a dummyl Oh well. Live and learn.

Imo000

Don't ground it. Since now you know what conditions it comes on, you can react if the light is triggered other than the "usual" time.

mark kibort

thats a great shot of you! you are contributing to the road, as you do on this thread!

mark kibort

Youre not listening to me.... its not the fuel lines, filter , pump, dampers or regulator... its the ECU... why do you think the mixtures went back to the normal range, when you went stock agaiin with the ECU?
the new filter didnt do anything... what you saw was normal pressure variance from maybe daytime to night time. (temp)
if the line pressure is at 40psi and it stays there as you go WOT, there is no clogged or pinched lines . again, look at my garden hose analogy. a leak, will not drop system pressure of 100psi. it takes a LOT of fuel to drop the line pressure . if you did have a clogged filter, you would see its effects at high rpm, not at idle or part throttle.

your tests at WOT at 15psi can blow a motor. fortunately , your engine is not pingging at ths fuel ratio . if you had more power , this test and that chip might have cost you an engine. holes in pistons, broken rings, ring lands, and maybe burned valves. leave the stock stuff in there until you get a chip that is able to keep mixtures correct at a minimum.

you test the vacuum line effect, which is ONLY for a few PSI (like 3) by disconnecting it while idling... if it changes from 40psi to 44psi when its removed, its working. its only job is remove a little sytem pressure , by pulling back on the fuel regulator diaphragm to then allow some additional fuel to return to the tank. its effect is NOT the difference of the intake pressure , which is neg 17psi vs the positive pressure of the system of 45-55psi . its the force the engine intake vacuum has on the back of the diaphragm in moving it away from the return path and how much more fuel returning to the tank will determine the reduction in overall fuel rail pressure.

why do you want to use the chip that makes the system run lean?? stock is working and works well... why not use it..... i dont understand. you found the smoking gun.. .... its the chip!!! Its not a damper... those things only regulate fuel pulses to smooth out the fuel flow. unlikely those things could have any effect on what ever you think your problem is now.. call me crazy, but the aftermarket chip is the problem... where is my error in logic here?

thats how you test it.. remove the line, see the fuel pressure drop by about 3-4 psi.

do you have the AFR meter on the dash? ive found that is great for early warning system .. if a WOT switch is not working or if you truly did have a clogged fuel line or bad injector.

mark kibort

TIMING BELT: what did you do? you were off a tooth at the beginning of the season, and the tensioner was bad? bad because you just found that the tensioner arm was "funky"? meaning , loose? is the bolt ready to shear? wrong bushing on that tension-er roller?
mine was acting up too (the light and sensor) so i grounded them too. if you keep an eye on tension, its not going to get loose on you. and if you have a major problem on the track, it will probable be too late anyway, and you wont pull off track if you see the light because you will think its a false alarm anyway.

Lizard928

If the belt is a contitech belt, it can cause the light to come on.

Replace the belt with a Gates.

Switch the chips between the two brains, see if there is any difference there.

PorKen

All your numbers are wrong, for a start?

The fuel pressure does not match the S4-up level (55 psi) that the S300s chip requires at WOT. Using the stock chip at stock pressure (36 psi) would likely also result in lean WOT. The stock chip is currently working only because fuel pressure is higher than stock (using a S4-up FPR), which is fine for now, but the underlying flow problem has not yet been found.

We should encourage AO to find the source of the problem so that others may benefit from this conundrum.
We should not encourage him (or others) to custom tune to suit problem(s) which may not be stable.

mark kibort

that is a urban legend.. ive used contitech for 20 years without any issues. i dont see the stretching problem everyone (well actually only greg) has seen. if i saw something that made me think the belt was a problem, i would have changed it.. . heck, is only a 45 buck item. my tension measured by the kepf tool and the porsche tool are in line and have no problems through out the season. ive had the same belt since the stroker went in 8 years ago and over 60 race days!

that makes sense. thats why i asked. 55psi seems high, even for the S4, but if thats the spec, thats the spec.
so, we are wondering why the S4 fuel reg cant get the pressure up to 55psi rather than 45-50psi that he is seing now? i dont think that you (he) will see much diffeence in thje mixture, even with the lower fuel pressure. my bet, is that if he put the 85 fuel regulator on and got his 35psi or so, i bet his mixtures would be near stock, which is near 13 to 13.5:1. that 10psi difference he is seeing now, is giving him 12 and even 11:1 fuel ratios... this is just as i would expect it to see. we have been going to the dyno for 20 years now and thats about the delta witih 10psi of fluel pressure change. remmber the holbert engine at 335rwhp... i bumped the pressure to 75psi to get 12.5:1. at 55psi, stock, it was near 13 to 13.5:1.
my 84 .... same thing... the most we could get out of the regulators was 52psi. (full max setting on the regulators) that mixtgure was a perfect 12.6:1 from end to end. i dont know what stock was, but i think i remembrer it being 13.5 :1. at WOT.

you are forgetting ONE BIG thing!!!!! you expect the S4 regulator to suddenly make the same pressure as the S4?????? really??? are all the same factors present??
1. same fuel pump
2. same fuel lines?
uhhhhhhhhhhhhh
3 same injectors .............OH WAIT, the injectors are DIFFERENT than the S4. 24lbs vs 19lbs......
thats probably the difference of why with the S4 fuel regulator, you dont get the same 55psi fuel pressure.

so, if AO puts back in the stock regulator, im sure his mixtures would be fine.
thats my take on it. think about it ken..... he sees 12s and "occasional 11s"..............this is a definite indication that he bumped the stock fuel pressure to 50PSI + vs stock and thats very normal to see those mixtures with this increase of fuel pressure of only about 10psi. (ive lost track of what he actually sees, but im thinking he is near 50psi right now.)

so, ill ask the question again, what is wrong with this logic above.

Cosmo Kramer

Mark, the regulator should be able to maintain 55 psi, with the stock pump at 0 vacuum. The regulator regulates the pressure upstream from the injectors, the 24 lb just flow more volume. I had an FMU on a stock S3 pump and it was able to generate 100 psi with 24 lb injectors so the pump is up to the task. AO isn't getting the flow or pressure required to run the s300 chips with the S4 regulator when the engine is running and he should be able to.

PorKen

There's also the tipover valve in the right side rear fender. It's just a big ball bearing in a plastic housing, but you never know. Then there's the internal state of the rubber fuel lines?

The idle fuel pressure should be more stable than what was in the video. That's mainly what the dampers are for, damping fuel pump (front damper) and injector (rear damper and FPR) pulsations at part throttle for better emission control (and less noise).

AO

Let's just forget about stock.

Ken has developed an LH chip designed to maximize power on the S3's by upping the fuel pressure and modulating the pulse width on the stock injectors.

I have swapped the FPR to the prescribed 87 FPR that should provide the proper fuel pressure to achieve the proper results. Because it was running lean, there is clearly a fuel delivery issue; it may be pressure - it may be flow.

Mark, You might be right - sort of. It might be the injectors. This was my first suspicion. I posted a pic back on #60 of this thread. regarding the injectors.

What if: the PO had replaced the injectors with S4 injectors and the AFPR? They could have tuned the FPR to get to the right mixture. But at some point, either someone didn't know this or forgot and set the FP back to 85/85 stock settings.

Now add in Ken's Chips which think you will have 24# injectors and an 87 FPR. You've increased the pressure but reduced the pulse width on the injectors. If the injectors are indeed 19#, the net result appears to be a step backwards. (i.e. overall duty cycle is less with Ken's chip than stock).

If I were to put a stock regulator in (which I don't have BTW), and stock chips, I would guess that I would still be lean (assuming the injectors are 19#).

Is there anyway to tell from the outside of the injector if it is a 19# or 24#?

This was the pic I had posted in #60.

Lizard928

I've seen it more than a dozen times, both on my own car, as well as customer cars that get brought in to me.
Roger's SE car had the belt light come on randomly, timing belt was a contitech, and I don't believe any other problems were found.
They hold their tension OK when cold, but when you are sitting in stop and go traffic with lots and lots of heatsoak is when the problem occurs.

AO

Forget about the belt.. It will be dealt with soon enough. It's fine.

I just looked up the injector part number. Those are 24#.