There IS such thing as too much meth - or so it looks like..

[dzenno@PTF]

Yesterday I decided to have some fun again with the car, weather is strangely nice again up here. After my last track day I was puzzled by why my timing was taking a dump during the entire run. First thing was that there's a leak at the input/output of the solenoid. This comes/goes all the time and I'm very fed up with cmgs fittings its not even funny, always leak. I managed to fix it again by cutting the hose but I'm sure it'll start up again. Anyhow, once this was dealt with I did some runs with a dual CM10 on my car. Timing didn't look good at all in 10 runs that I did. Then I switched out one of the CM10s to a CM7 (so a CM10+CM7 setup), left boost+AFR the same, and timing started to improve but still wasn't great. Then I took out the CM7 nozzle altogether and just ran on a single CM10 and what do you know, my timing is looking great. This is with 94 pump gas and 100% meth.

Not sure yet what to conclude on this but given I don't need meth to have "richer" AFRs (as Cobb already hits 12AFR without issues even without meth) I think just using a single CM10 nozzle should be plenty. Flow out of this single nozzle is on par with 2 Aquamist's 1mm nozzles.

The next thing to try is to run a 75/25 mix for a bit and see what logs/vbox times look like and then back down to the 50/50 mix. During the testing above initially the dual CM10 nozzle setup impacted the 60-90 vbox times quite considerably. Each time I reduced nozzle size, timing improved, and the car got faster so there's definitely something to consider there before just deliberately upping nozzle(s) sizes...

Maybe, just maybe, too much meth or over-mething is responsible for that timing flatlining with the automatics? For those that have that issue maybe try a smaller nozzle and log and see if you see any improvement, while trying to preserve IAT cooling benefits..

[enrita]

what outside temps do you have there? I cant run meth at all now with 5C and below and started to get bad at around 10C. No clue if this is due to the Procede aggressive maps (thats why i would like to test a COBB meth map and log fuel trims) but seems with colder temps meth creates issues.
Could it be possible that the DME switches tables below a certain temp like it goes on winter mode?
IMHO the colder it is the smaller the nozzle should be used.

[dzenno@PTF]

Temp was around 15-16C yesterday, 13C today

[Sticky]

I hope this helps somehow:

[LostMarine]

cant be. im on a TRUE dual meth and i didnt have issues. now the meth in colder temps is a theory as i didnt have issues in 60*+ weather, but i did start to get the high rpm misfires in colder weather with so much meth.

i replaced oil and plugs yesterday and haveny tested yet. but ill see how she does

[dzenno@PTF]

Lol awesome and sad at the same time

[themyst]

cant be. im on a TRUE dual meth and i didnt have issues. now the meth in colder temps is a theory as i didnt have issues in 60*+ weather, but i did start to get the high rpm misfires in colder weather with so much meth.

i replaced oil and plugs yesterday and haveny tested yet. but ill see how she does

You also have old DME software. Dzenno and I do not.

Dzenno, for the sake of not introducing any variables, did you reset the ecu after each change?

By reducing your meth flow without resetting the ecu the car will naturally run positive STFT which may be the cause, not the actual reduction in meth quantity.

[LostMarine]

You also have old DME software. Dzenno and I do not.

Dzenno, for the sake of not introducing any variables, did you reset the ecu after each change?

By reducing your meth flow without resetting the ecu the car will naturally run positive STFT which may be the cause, not the actual reduction in meth quantity.

good point

[themyst]

what outside temps do you have there? I cant run meth at all now with 5C and below and started to get bad at around 10C. No clue if this is due to the Procede aggressive maps (thats why i would like to test a COBB meth map and log fuel trims) but seems with colder temps meth creates issues.
Could it be possible that the DME switches tables below a certain temp like it goes on winter mode?
IMHO the colder it is the smaller the nozzle should be used.

I used to run a CM10 nozzle in 23 degree ambient temps which is like -4 degrees C on the old dme software and my timing looked fine. Car pulled like a freight train too. Loved it!

[dzenno@PTF]

You also have old DME software. Dzenno and I do not.

Dzenno, for the sake of not introducing any variables, did you reset the ecu after each change?

By reducing your meth flow without resetting the ecu the car will naturally run positive STFT which may be the cause, not the actual reduction in meth quantity.

No reset...just a bunch of back to back runs...STFTs adjust immediately that's why they're "short" term...each run they'll adjust...LTFTs adjust over a longer period...

[dzenno@PTF]

Oh and with a reduction in meth flow STFTs will instantly go higher due to a higher requirement on fuel when there's less meth flow

[Tzu]

This is only my second winter season with a meth setup. After first year, I definately noticed that meth was not nearly as effective in the winter as in the summer. Work has kept me seriously busy, so I only have theories:

Meth is an alcohol, which vaporizes in high velocity charge air, more easily and uniformly at higher temps. Winter charge air doesnt have the same energy to give up into the meth as summer air.

If I get time, I can break out the old latent heat of vaporization tables for alcohol and crunch some numbers. My simple solution is to not run meth in the winter. Seems to work lol.

[themyst]

Oh and with a reduction in meth flow STFTs will instantly go higher due to a higher requirement on fuel when there's less meth flow

What you're not getting is the STFTs are correcting based on the learned LTFT values. And the correction percentage is 34% max based on the LTFT.

Resetting the ecu will eliminate this from being a variable as it takes many runs to fully adapt the LTFT where the STFT starts at 0% at WOT onset or close to it.

No matter how adapted my ecu is, short term trims trend downward drastically and gets worse the longer the pull. I'd rather see consistent positive trims post shift which running less meth should accomplish, or at least reduce the rate at which the ecu pulls fuel.

You're definitely on the right track and makes perfect sense, but the best testing to eliminate variables is to reset the ecu after each change.

[themyst]

And when I get home, I'll graph out 6 back to back runs with STFT and timing so you can see what I'm talking about.

[Terry@BMS]

You're saying you logged your meth trims with the CM10+CM7 nozzle and they were negative, and you've associated these negative fuel trims with poor timing? I haven't been able to find any repeatable correlation to fuel trims and advance all else being equal. Do a few charts and let's see what you have.

[themyst]

Just to add more speculation to the mix, I just flatlined on stage 2 pump gas Goddamn fuel mode 6!

[Brey335i]

Just to add more speculation to the mix, I just flatlined on stage 2 pump gas Goddamn fuel mode 6!

OTS Beta maps and no meth?

[themyst]

OTS Beta maps and no meth?

yep. Stage2+FMIC aggressive 93 octane no meth.

[themyst]

And as promised, here are logs all done in succession. As you can see, the LTFTs clearly impact the STFTs the more it adapts. And some of these aren't single gear pulls, they go deep into 4th and 5th.

[themyst]

FYI, here's stage 2+FMIC aggressive flatlining on PUMP GAS.... LOL!

[JoshBoody]

Those are some wild logs and seems timing is definitely fuel related. I would almost guess that you could have a hardware issue... rail pressure sensor, fuel injectors coded incorrectly or worn. But AFR ratio is fine... i would expect to see some variance when the trims go very negative at least. I'm curious now.

Dz for meth... vaporization shouldn't be an issue, but poor atomization could effect cylinder distribution. If you are getting even distribution, then maybe air density is just too high... how's timing?

[JoshBoody]

hey Myst, you plotted VANOS I see... awesome! But I can't seem to make it out in the logs... can you post the cvd files?

[enrita]

pretty clear AFR is not affected at all by the fuel trims.... great info.

Is there any impact in how the engine runs when fuel trims are negative?

[Big Tom]

I'm running dual nozzles (CM10 + CM7) and my timing is perfect, even during cold ambient temps (35 fahrenheit).
The annoying thing is that I'm suffering from high RPM misfires right now, but that is probably caused by the colder ambient temps combined with old/worn spark plugs.
I'll change them in a couple of days, and hopefully the misfires will disappear...

I really hope that I'm not infected by the PROcede-misfire-disease.
The newer maps (including the aggressive maps) is impossible to use without getting misfires......

[themyst]

Those are some wild logs and seems timing is definitely fuel related. I would almost guess that you could have a hardware issue... rail pressure sensor, fuel injectors coded incorrectly or worn. But AFR ratio is fine... i would expect to see some variance when the trims go very negative at least. I'm curious now.

Dz for meth... vaporization shouldn't be an issue, but poor atomization could effect cylinder distribution. If you are getting even distribution, then maybe air density is just too high... how's timing?

fuel injectors coded incorrectly? How is that possible when I never had them replaced? There are no hardware issues. The car runs strong, feel nothing out of the ordinary and trims look perfect when I reset the ECU. If you want the logs I graphed out so you can see VANOs, just let me know. I'll email them to you. There really isn't much to see.