EvilZ06,
I have analyzed the test runs that we did at my garage this weekend and promised I would give you some results to use to help show the problem and to help resolve it.

Two test runs were done with outside temperature of 85 degrees.
Each run consisted of 12 miles of 15 miles of distance, using all RPM, gears, and throttle ranges. This included stop/go city and highway driving while I monitored and collected PCM functions status while you drove the car in the manner you do.

Both test runs used the exact same roads and distance to limit any changes and 2nd run was done within 10 minutes of completing first test run.

The following is what I determined via PCM data collected via a Ease enhanced powertain scanner connected to the PCM.

Mark's Z06 Test Results

NOTE: the trace consisted of over 3,600 PCM read cycles, but to make this viewable using less screen space, the above was sorted to show knock and lean AFR issues. Also content important has yellow background.

Your surging issue is due to your long term fuel trim being 22 percent too lean. The removal of the MAF screen itself did not drive the leanness to that high of a level, but the other mods combined took your Z06 from being a performer, to high heat generating engine.
Even with the MAF screen installed, the existing mods drove the AFR out of a performance window.

You can see within this results sheet :

LTFT far to lean
Lean condition drove engine knock high, for both WOT and normal driving conditions). Cell 22 is WOT when TPS ( throttle) is greater then 99.5% on. Cells 1-19 are when you are pushing on the gas pedal, but not to the floor.
As seen knock is ocurrung in all cells and TPS position.
causing lessor performance at WOT due to timing on;y being an averge of 25 degrees ( about 3 degree loss, that also lowers maximum torque).
As seen by the injector pulse width, the PCM was attempting to go richer but could not achieve better then the 22 % lean average.
Intake Air Temp (IAT) was 5 degrees hotter then outside temps, thus air intake needs to be improved for IAT should equal outside temps when moving fster then 20 MPH.
The engine water temps spiking 220 degrees further hinders a lean condition, and the lean AFR itself helps drive the engine temps up due to hotter internal temps due to too lean buring AFR forcing pistions, sparkplugs, etc to run much hotter.
You'll notice engine knock was present no matter if the RPMs or speed were low or high.

The surging issue was clearly due to the leanness and to test this and to also reduce the knock issue. I hardwired in a MAF translator and simply set the AFR to reduce from a 22% lean down 5% to 16%.

Apon doing that and then repeating test run, knock went from being triggered 43 times to only 14 and all surging was gone ( but not totally when A/C is on).
By further adjusting AFR with the MAFT, both ill conditions can overcome the mods causing the conditions but I do not agree in total to this type pf fix.

The reason is to fight off a lean condition this far off of being perfect ( a LTFT of zero) you have to drive the PCM to go richer which them means it also drives WOT timing down that will also reduce performance.

You can either resolve the mods causing this over lean condition by vendor correcting or removing such mods.

Use the MAFT to drive LTFT as close to zero, but lean enough to maintain about 28 degrees of WOT timing, but not at the expense of increasing knock, which wold retard that timing

Or as I and others have done go with a larger injector such as SVO 30s, and tune out richness, that means going leaner, drives WOT timing up.

I suggest for next testcase, you adjust base of MAFT another 5% richer and re-scan PCM to determine if that is a short term correction.
Feel free to contact me for more idepth information of test results.

 

EvilZ06,
here is my finding as to the PCM scans I analyzed with the Ease powertrain scanner.
For ease below I show the findings of the two test runs we did that were the same distances of the tests we did last week.

SVO 30 Injector tests

When we first did PCM scan testing, as you can see (top result report) the long term fuel trim was 21% too lean
WOT timing about 23 degrees.
Overall timing about 27 degrees.
4.2 mS injector pulse width,
non WOT, 16.2 mS WOT pulse width.
43 engine knocks, costing an average of over 4 degrees timing retard.

Due to the mods installed causing a hugh lean condition, engine knock, lower WOT timing and Ca crapgas, I knew this Z06 would respond best with the SVO 30 injectors and a MAF translator, rather then the general hype of "if it does not work, S-can it and go back to stock".

As I had mentioned in the past, going with the larger injectors gave a better outcome of not only tuning in the PCM via a MAFT, but also obtain better overall performance, rid surging, and reduce injector duty cycle.

You notice then in bottom test results how well the PCM and engine accepted the larger injectors and MAFT settings.
(NOTE: Weather was 85 degrees)

Overall timng went up to 32 degrees.
WOT timing gained 4 degrees which is also a gain for torque.
Injector plusewidth showed reduced duty cycle for both WOT and non WOT condition.
LTFT was reduced by 50% ( we can and will dial even more of that put and not effect inducing engine knock)
Knock - NONE, not even a .01, and that is with the crapgas and we allowed water and air temps to be higher then the "before" test

This once again showed that many of these high dollar mods can have an ill effect to overall performance but rather then just threw them in the junk can, by doing the proper PCM tuning and understanding the functions used bv the PCM.

As we began our first test run after installing the injectors and tuning the MAFT, I watched EvilZ06's face and he was caught off gaurd as pulling away from a stoplight, that now having good engine timing also woke up the torque and he hit the rev limiter far quicker then he could have before. :)


[QUOTE]Originally posted by EvilZ06
After talking to John I decided to upgrade from stock to the SVO 30# injectors. This meant that instead of setting the MAFT to 10% rich, we were able to go 10% lean.

Once the injectors were installed we performed an idle relearn (with AC on and off) and then took another test drive with the Ease powertrain scanner.

The results- absolutely ZERO KR at any speed or rpm and we also gained around 2 degrees of timing at WOT! :D The car feels very strong and pulls hard.

I will be dynoing the car on December 1st at the next bay area dyno day. It will be interesting to see if the SOTP holds up!

Hopefully John will provide a more detailed explanation, and possibly put up the scans.

Thanks! :cheers: [/QUOTE

 

"if it does not work, S-can it and go back to stock". :lol: :lol:

Thats funny John... Where have I heard that before??

Mark I am glad your car is running right... mine is not so lucky. :( I am working on getting mine fixed soon. :nopity

vetterdstr :hat

 

Steve, I bet when you look closely at the heads you'll solve your problem real quick and finally move forward with your main goal.

As i was working on EvilZ06's vette today, i also got working on the Rebel's brakes.
As we discussed when you were over my place yesterday, the brakes were worse off then I thought.
Those race pads have less then a 1/16 of an inch left on the fronts ! :smash:

Dang those Mallett pads must be made of some stuff, to still be able to stop with zero pad left.. Front rotors look like they were grooved out by a grinder.
Rear pads still have about half the depth left. Both outer edges of Rotor had at least an 1/8th of an inch higher lip and was hell getting the calipers off the rotors.

You'd think the rotors would have warped but they are still true.

As soon as the new rotors and pads arrive I'll get the Rebel done and if your brake parts get here this week and you need help, stop by and I'll help you do the install.

 

Hey Steve!

Yup! My car is enjoying the extra gas! Ole Evil was running a bit lean before, but we got that sorted out now! ;)

John told me about your woes, hope you get it fixed soon! :yesnod:

I do have a couple of minor issues myself. One of my injectors was leaking fuel tonight. I'll have to check in the light of day tomorrow to see if it needs reseating or if it is defective. Ahhh the dark side of mods! ;)

:seeya

 

Steve whats up with your car, you can email me if you don't want to blast it all over the forum.

As for fuel injectors I think the duty cycle is very important. Alot of people modding the later C5's 99-02 (97-8 & Z06 I believe have 30 lbs per hour but the rest have 28 lbs per hour) should make this part of their mods......there goes another $800.00.

Whatz up John? I was talking to Jim Mars a couple of weeks ago and he said to say Hey.


[Modified by Shinobi's97, 12:37 AM 10/20/2001]

 

Last Friday I went to run my car. It went something like this... 1st run, I stage up the light goes green I drop the clutch and nail it after hooking up and the engine bogs and then hesitates all the way through the run. The car felt like it was running on its knees. High RPM sucked!!! I made 7 passes that night with all of them no where near what I should be running. :( Since then TeamZr1 has helped me make some changes to the car and I took it out last night and it ran pretty good, but not perfect. I hooked up a fuel pressure gauge and ran it down the freeway standing on it hoping I had a bad fuel pump or something that I can fix. The fuel pressure is good though. :) Now the car went back to just the single hesitation at high rpm's as it did after the lastest round of Mods.

I talked to the dealership (hoping they could help) on Tuesday and I have not heard back from them yet. :bs Hopefully I can get it fixed.

vetterdstr :smash:

 

The Z06 injectors are rated at 3.55 grams/second. That's equivalent to 28#/hour injectors.

The SVO injectors John and I installed on my car are rated at 30#/hour, but for our application they are pumping more like 34-6#/hour. No problem with a lean condition now! ;)

The pulse width for the injectors dropped about 17% indicating the much lighter load for the new injectors.

One last thing, the cost is very reasonable. Around $220! :D

Good mod! :yesnod:

 

The SVO 30 injector's used by Ford racing for the SVO use far less fuel rail pressure so in a C5 which runs around 60 PSI, these injectors are more like 36 lbs which is about 30% higher then the stock ones.
Thus in using them these injectors do not have to run anywhere near the 80% plus duty cycle which is a positive.
I have been using them for most of this year and they worked out well in solving the 8-10 % plus lean condition, plus tuning out richness has a positive for in going leaner raises timing where trying to tune out lean condition, by going richer lowers timing and at WOT you want all the timing to maintain maximum torque.
BTW, Steve just bought his SVO 30s for about $220 which is what I and others I have helped paid so that $800 pricetag is way out of line, big profit for sure.
Has Jim got the new engine installed yet and tell him I also said Hello !

John

 

Nice Work Team-zr1 :cool:

 

Thanks Shawn,
The hardest part is getting people to understand they need to monitor/scan their PCMs and learn to understand what the PCM is telling them.
Once people understand that it has been neat this year for me to see Corvette owners take control and tune in not only to have better overall performance but also in a sense have a perfect fuel trims/AFR, thus staying within the smog limits but still have a better performing Corvette.

I am now getting about 5 PCM traces a day people want me to analyze and even those people never getting techie have shown a good learning curve once I show them how to record PCM parameters, how to read those traces and what to do to overcome ill performance due to AFRs out of the performance window.

On a different front I began to notice those owning A4 C5s have ills related to torque management and as they have someone re-cal their PCM, the TCC, slippage is worse without the owners knowing it.
In only by monitoring A4 functions did this float to the top of how the car performed, mostly on the ill side for good performance.

When you start seeing the Delivered torque parameter reporting 1,200 plus ft/lbs of torque all over the RPM range, its a clue to start looking at tuning the A4 to meet the increased performance done to engine via mods and to assure the 3rd party torque convertor also works well with the tuning of the A4.

As for the SVO 30 injectors, for the $200, its a good mod for long term goals.