Lsj ve g/cyl

[armcclure]

Switched to a new turbo (s360) the other day. Since I didn't have my intake finished yet I stuck a simple 90* pipe on and worked up a full sd/ve tune to get it going, which actually runs surprisingly well.

This brought up something I had never noticed before though, and tht is that the calculated g/cyl (that we have available to scan) appears to only use maf for calculations, as it stays at (more or less) zero, kinda hovering around 0.003-0.04 regardless of load.

HOWEVER, the PCM is obviously calculating it some other way because the timing ramps like normal from cruise to wot along the g/cyl axis; scanning ign advance (default histo #1) everything stays in the top row.

On the other hand, I have a switch I just installed for rolling anti-lag using the iat2 signal (similar to what people commonly do for nitrous) that reads 305* when the momentary button is pushed. However, this is having no effect on timing. One would assume that like most other tables, with a value greater than the last column it just uses the last column value (248*). But when the button is pushed it has zero effect on timing. Iat modifier is set to -15 in the last column, and mult vs rpm is 1.0 from 3000 up.

So the conclusions I have come to are:
A) when using ve only, the PCM creates a g/cyl reading to use with the main spark table and nothing else

Or

B) the iat modifier ignores a temp input over 248*

Logic would say that A is the case, but it's still odd.



I'm the end this should all be a non-issue once the maf is reinstalled, just something that got y gears turning and thought I'd share.

Thoughts?

[armcclure]

I just replaced the current wiring with a NC switch that when pressed disconnects the IAT2 signal from the PCM, giving a -40* temp in the scanner. This still have no effect on the timing. Thinking this somehow must have something to do with the pcm not calculating a g/cyl value, which doesnt make much sense either...


I know this method works well on other platforms; very common on evo's.

[armcclure]

FYI for those interested;

Plugging the maf back in, even with it set to fail at 0hz, fixed the issue. Apparently the pcm needs to see a maf calculated g/cyl, even if its not using it, in order for those tables to function.

Everything is working great and knocks over 500rpm off of full spool.

[codename Bil Doe]