A question to you turbo guys up north... cold weather boosting...

[Guest 73Turbo240z]

Alright, last night i had my car out, weather was around 29-34 degrees with 14% humidity, we had the car running around 12.5:1 AFR's according to the LM-1, but in third and fourth gear pulls, we were getting knock or pre-ignition, the marbles in a can effect.

 

so today i enriched my entire MSnS fuel map by 10% and it seemed to help.

 

but i was curious what you turbo guys do up north for AFR's, texas isn't usually cold, so i need an idea of what AFR's to tune for on these freakishly cold nights... were use to tuning for 70 degree nights and 80% humidity.

[Guest bastaad525]

yeah 12.5 is a little too lean... I know when I was running as lean as 12.7 the first few times I dynoed everyone said that was way to lean and get it down to 12 flat or even a little richer than that.

[EZ-E]

I would think that you would want your AFR in at least the 12.1 to 11.9 range from all that I have read here.

 

Are you injectors though up to it though? Though I think that 12.5 AFR is a bit lean, concidering the temperature, I wouldnt think that it would be so bad as to start knocking.

 

Are you still running stock injectors?

[Thumper]

He is running 440cc injectors. And his block is made to handle alot of boost. But since he has a new clutch he has been running stock boost 8psi. I have tuned it to run 12.5:1 at 8psi and then at anything about 12psi the a/f ratios are around 12:1 then 11.5:1 at 18+psi. We never had a big problem intill it was 30 degrees out. I would think the IAT would adjust for the colder air going into the combustion chamber. But guess not.

[proxlamus©]

this on the Holset turbo??

[Guest 73Turbo240z]

yes'm

[mobythevan]

I was running 11.0:1 AFRs in boost, but I didn't care if I lost some power to be a little safer. Seemed to run real good to me.

[Clifton]

If you have knock at 12.5:1, adding more fuel and bringing it down to say 12:1 may or may not stop the knock. Gas has a poor latent heat of evaporation, it doesn't cool very good. Even if it richiening it up does stop audible knock (doubtful) as you said seemed to help, you would still be on the edge of knock and may still have it but can't hear it. I would pull a few degrees of timing or drop the boost depending on what your timing is at full boost now.

[Thumper]

Boost was at 8psi maybe creeped to 12psi nothing near what this engine can handle. I am going to pull a few more degrees out of timing just to be on the safe side though.

[Clifton]

What's you total timing at under boost?

[Thumper]

I'm not sure what timing is at 8psi but at 19psi it is 16 degres. And total timing is 39 degrees. I will have to look tom. I have another questions about total amount of timing I should pull. http://forums.hybridz.org/showthread.php?t=108246

[ngrimm]

Have you considered water/alky injection? I believe you could use MS to trigger it. That's quite an impressive set up you have, I really enjoyed your "track" videos too. Norm

[Guest 73Turbo240z]

Have you considered water/alky injection? I believe you could use MS to trigger it. That's quite an impressive set up you have, I really enjoyed your "track" videos too. Norm

 

my friend and i were discussing alky tonight actually, were incorperating it into the grand national were building already, so were toying with the idea of a set PSI hobbs engaged system for mine...

 

although i was under the impression those were more of a band-aid fix?

[ngrimm]

I have been using hobbs switches with good results. I built something of a progressive system that utizes a Shureflo pump and an adjustable fuel pressure regulator to raise the water/alky pressure as the boost rises. I have been able to run 20-30 percent more boost which as they say is a good thing.

[Clifton]

If you are using a distributor, have you locked you mechanical advance? Unplugged the vac advance?

[Thumper]

We are running the 280zx turbo distributor so no mechanical advance. We are running megasquirt with msd 6al boxes.

[Silent]

put it to ya like this

in a talon tsi i had a couple years back. i had water injection on it. 180k miles on original motor, 24 psi on stock ported 14b, a ported manifold, hard pipe kit, k&n filter, modded mas air, 3 inch turbo back exhaust pulled a nice 108 mph. for less then 500 bucks in mods. now the 24 psi was on 110 octane. im a HUGE FAN of water injection. it gave me a chance to run silly amounts of timing {close to 30 degrees under full boost} at this boost level. i can go into more detail if need be. but this should give you a good idea on what water injection can do. if it can do that on a high mileage turbo motor, imagine what you could do on a fresh L series!

 

as far as your problem. stock efi systems compensate for cooler air, standalones do not. {at least the ones im used to messin with} so. with the Ms system, im not sure if you can do multiple maps, like for warm temps, medium temps, race gas, pump piss, cold, or something of that sort

[Guest j-mcguigan.com]

Can an air temp sensor be incorperated with Ms?

Just a thought...

[Guest 73Turbo240z]

MSnS uses a GM IAT sensor... but the timing is to a degree locked to what you set on the maps in MSnS... i don't know how much MSnS compensates for the IAT's it sees.

[Thumper]

Megasquirt only changes the fuel settings depending on IAT not timing.