I finally got back to the track after about 2.5 years.

My best run was a 14.002 @ 100.35 with a 60' of 2.114. I bogged out of the hole because I had the Nittos pretty hot and didn't dump the clutch high enough.

But I know something is wrong with the car, and it seems to be ignition related.

My long term BLMs at idle are 128, so I can't seem to figure if it's ignition or not...

From my logs I can see:

1) MAP at WOT is below 100, anywhere from .95 to .99, mostly around .96-.98.

2) There is an RPM + airflow dip around 5100-5200 RPM. One example from the logs, the RPMs go like:

4900, 5025, 5000, 5175, 5100, 5275, 5125, 5200, 5100, 5250 and then finally keep climbing.

At the same time the airflow goes up and down, like

237, 236, 244, 240, 244, 258, 243, 258, 244, 243, 248, 268, 253, etc.

3) I am getting knock retard around this same area, from around 4900-5200. Timing is stock, and I even took a few degrees out of the 95MAP cell so that 95 & 100 were the same.

4) My MPH seems low for my mods: 4" CAI, 3" cutout, Accel 300+ ignition, Street Twin w/ aluminum FW, and custom tune (higher AFR).

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Oh, and the dumb car kept using cell 18 for the WOT portion, instead of 15. I even had it running several minutes before the race, so I don't know why...

Could this be a failing opti? It's still stock at 112K miles. Fuel filter is new, plugs are pretty new, wires are a few years old, but 2 worn ones were replaced with GM stockers.

Could it be loose rockers?

Give me some ideas, guys. I want to get a run in with the spray, but my fuel solenoid isn't opening and I don't want to race on spray with ignition probs.

TIA!

 

Your map readings are fine. It is going to full throttle according to the computer. Your mph may seema little low because of your location. I am not sure how high or low sea level you are. That can play a HUGE difference. You opti could have a miss starting to develop. That could be cause of the readings that you are getting as well. Or fuel problems. Put it on a dyno with a wideband. The knock could be because of ****ty gas, headers, roller rockers, or a combination of all.

 

After a million different attempts to fix my KR problems I am pretty sure my knock retard issues were with the stock timing - it is pretty agressive. Maybe scale it down a couple degrees.

Acutally..try race gas first to see if its false!
Ryan

 

Well, these problems didn't use to happen. I used to have .99-1.00 MAP at WOT, and I used to run 2-3* more advance than stock at WOT with no knock.

Now, things have changed, which makes me wonder if it's an ignition issue.

I guess I'll try race-gas and see how it goes...

What about the low MAP?

 

if its using cell 18 in wot that means that the pcm is seeing a lean condition and is adding fuel before you go into wot. and is compensating for the previous lean condition by adding some extra fuel from cell #18 while in.

so say your target a/f ratio is 13.0 to 1 well in cell 15 at wot thats waht it is trying to hit. now say your target is still 13.0 to 1 and the car sees a lean condition just before entering wot it uses cell 18 and trys to compinsate by adding so much fuel. so now its trying to correct the lean condition in wot to protect the engine. how much it adds i dont know. but i have seen 12.2 using cell 18 when my when its programed to hit 12.9 to 1.

just trying to lemd a hand.

 

It's the other way around. If the PCM was "adding" fuel in closed loop (BLM's above 128) it will use cell 15 and the Cell 15 BLM's. That insures it doesn't "go lean" at WOT. If the PCM was "cutting" fuel in closed loop, it defaults to Cell 18 and locks the BLM's at 128, again to insure it is not possible to "go lean".

You can't just compare MAP to "100". You need to compare it to "BAR". A few points loss below BAR as WOT makes sense. Go 10 points below BAR and you have some sort of pressure loss in the air intake path.

Looking at BLM's at idle means nothing. You need to be looking at the high load/high rpm cells. Just look at Cell 15.

Running the massive weight of a Street Twin on a relatively stock engine has got to hurt rwHP.

 

sorry my mistake. im debating wether its monday or not. becuase today has sucked.

again sorry.

 

Thanks for the input, Fred.

My BAR almost always reads 100, that's why I compare MAP to it.

I mentioned my BLMs at idle because I think that gives a general idea of whether combustion is complete overall. Since it's not running rich at idle (128 BLMs), and the injector constant is correct for my injectors (31.68 for 30# SVOs), then it would seem that it is combusting correctly, and that there isn't an ignition issue.

Unless, as you mention, it could related to WOT only. Normally my O2 readings seem great, mid-high 800s. But this last run when it was running in cell 18, they were mid-900s.

Lastly, I am pretty sure that the aluminum FW ST setup weighs either the same as or less than the stock clutch setup... so I don't think that could be affecting HP, do you?

What do you think of the airflow fluctuations?

Thanks again for the input, and I hope this added info helps you help me.

Oh, and to 97Z-M6, it would seem what you say is true since I was running richer in cell 18 than I usually do in cell 15. So, don't know who to believe there.

 

Oh, I forgot one mod, an ASP 24% underdrive pulley/damper.

I'm gonna try reducing timing even more and see if the knock goes away...

Still would like to hear thoughts on the fluctuating RPMs/airflow.

 

I missed the aluminum flywheel... good point.

Just check Cell 15 BLM's.

The air flow is tracking the rpm. The question is why is the rpm fluctuating? Might be the timing retard causing the swings.

 

My car wont use the right BLM cell at the track sometimes too. I change the coolant threshold to enable closed loop, set it so the conditon wont ever be met. Makes tuning and logging a little easier. That way it is gauranteed that the computer wont try to learn. Just a friendly tip i figured i would pass on.

 

if your carbon canister purge was 100% then that could also be why you were running in cell 18. i have noticed on my car when the CCP is 100% it will last for quite a few minutes. I also agree with Fred... your cause and effect are backwards on the MAF/RPM readings.

 

Thanks Jared, I might try lowering the threshold next time. The thing is, I know it was in closed loop, but it still used cell 18 for some reason. Are you talking about something else? Are you saying that setting the threshold super low causes cell 18 to not be used?

Fred, the BLMs in cell 18 were 128 the entire time, both long and short term.

Brad, thanks for that idea. I've been wondering if my carbon canister could be cracked, or have a bad hose, since I've been getting bad MPG. I guess I'll check that soon too.

Maybe the timing retard is causing the RPM fluctuations. Any chance worn out springs could cause this (valve float), since they are stock at 112K miles?

Thanks again everyone!

 

I go into the ECM constant table, and change min coolant temp for closed loop, and min coolant temp for closed loop w/ cold MAT. I slide both of these all the way up (150* C or so). This will prevent the car from trying to learn at WOT from a previous lean/rich condition (will be in open loop, never in closed). When you are making changes via programming, and the ECM is making changes based on Block learns, its almost impossible to get the tuning nailed down.

Once you get the tuned nailed down how YOU want it, not the ECM, you can put your thresholds back and allow the car into closed loop again.