IAT spark adder table

[NigelTufnel]

Quick question regarding the IAT spark adder table. Current setup is a 2k LS1 (C5), TT, alky kit and running the 2bar custom OS. Getting ready to work on the timing tables and my plan is to leave the main tables in a safe range, add timing via the IAT spark adder table when the temperature drops due to the meth injection and remove spark via the table when the temp gets high. Here’s the question - since my IAT table only goes to 100 kPa (even though it’s a 2bar OS), for boosted regions will the adder be the value in the 100 kPa row?

[rockoosi1]

I was doing some tuning myself and was thinking along the same lines. I did a pull on the street and noticed that the PCM pulled about 3 degrees of timing. I believe it was my IAT table as well. Now I'm on the fence and not sure if I should just add 3 to the main spark or zero out the IAT. I haven't hooked my meth up yet but I will this week.

I'm curious to see what others have done.

[NigelTufnel]

So no one knows?? I guess I'll be doing some testing this weekend.

[Sam88gta1]

So no one knows?? I guess I'll be doing some testing this weekend.

Yes it will.
Are you trying to protect against a possible Meth pump failure? What are you going to do about the potential lean issue?

[NigelTufnel]

Thanks, I'm going to give it a try.

I'm still on a stock bottom end, so the plan is to tune for 11.5-11.8 AFR without meth, and to use the meth as a safety factor (yeah, it will be rich with meth). That way if the pump fails the AFR will not go lean. If the pump is fine and meth is flowing, the IAT will be below some threshold level where I can safely add a few degrees advance. If the pump doesn't run, no additional timing will be added and since the AFR was tuned without meth a lean condition will not exist. Only real concern would be a pump failure during boost, in which case it won't go lean but will have a few extra degrees advance (assuming a slow IAT response).

[TXZ0603]

Here is mine on a 3bar os. Not sure why yours reads in Kpa.

[NigelTufnel]

Here is mine on a 3bar os. Not sure why yours reads in Kpa.

Yeah I noticed that too. Other than mine, I''ve only seen g/cyl for the adder table. Initially thought it was due to different PCMs, but here we have two C5's with different tables. Anyone know why there would be a difference?

[Ben Charles]

Mine looks similiar to the one above.

Question for you guys though. When tuning AFR without meth say 11.7 when you activate the meth what does the AFR change too on your setup? I am running twin 14 nozzles from AIS, just wondering by about how much it would richen the AFR?

[The Alchemist]

I have the same issue in my 2-bar setup on a 2000 F-body.
My IAT spark advance is in kpa, I wonder if it's something in the later model years.

EDIT: I just looked a later model year F-body, 2-bar setup, and the IAT spark adder table is in g/cyl airmass as opposed to pressure. So it's probably the difference between pre and post 2001 model years.

[5_Liter_Eater]

Yes the older model years have the IAT spark adder in MAP and the newer model years are in airmass (g/cyl). Either way, using it for adding spark when the meth hits or removing spark if it fails works well although I have to change my table in the winter and summer. I guess the bummer with the MAP based table is you could only use the 100 or 105 kpa row to add timing and if your meth is not set to come on until 3-4# then you're adding timing when its not spraying...With the airmass based table I can find where I am at 3#, which for me is at .8 g/cyl.

I see a good ~25 degree drop in IAT when my dual nozzle (M10 & M15) meth kit engages and IAT's barely creep up a few degrees as I get to redline. Before I started meth dependent tuning I saw ~1 full point (sometimes more) drop in AFR. So if I had it tuned to 11.5:1 without the meth I would see ~10.5:1 when it hit and with how I have my gain knob set it would end up flatlining at 10:1 by redline. Now I tune it to 11.5:1 on the meth and I picked up another ~30 RWHP. But there is no PE VS IAT table to dump fuel if the meth fails so it's now a meth dependent tune. My only saving grace is the aeroforce interceptor which alerts me if I am over 3# and leaner than 12:1.

[Ben Charles]

Thanks for the info, I currently have twin 14 gph nozzles from AIS 100% pure meth and I have heard that can change up to 2 full points. I am thinking about just using 1 nozzle now. I want to be around 11.5 too on the meth.

I would think sitting up the IAT table to pull timing could save the engine even if it hit 12.5 on boost if there was a meth failure???

EDIT:
Talked to Rodney at AIS using 100% meth with the largest 14 gph nozzle (single) AFR will drop 1 point.