Need help tuning my supercharged 94 Z28!

eehack can test idle parameters in real-time. simply use eehack's 'control' section.

check idle 'override' and spark 'enable', then play with the idle speed and timing until it feels right. it will default to your existing target and timing.

you may want to do this in neutral too. and while warming up. experiment a bit at different temperatures.

you can get test a hotter idle by overriding both fans to 'off' while monitoring coolant temperature, so you don't have to wait until you are in traffic in the baking sun to figure out that your idle only works in your driveway.

if you check the 'steps' button, you can control the IAC motor directly (so the ecm isnt trying to hit an idle target), you can use this to experiment and see how it behaves in other cases.

there's a small clipboard button next to the idle and timing controls, if you click them, it'll copy those parameters to the 'notes' screen in eehack so you don't have to write them down. then use those settings as hints for new values to use in your bin.

edit: one more thing, the LT1 really likes its throttle plates nearly closed so it can use the idle passages. the passages are fed both by a bypass hole and the IAC valve. the passages run through the manifold and feed the rear and front of the plenum more uniformly than the throttle plates. every lt1 i've tuned tends to idle best if nearly all of the idle air comes through those passages. if you have to open your throttle plates to get good IAC counts, in my opinion it might be time to consider drilling out your throttle body's idle air bypass hole a bit.

i had a few more thoughts on your log, do you think you might have a boost/vacuum leak? the last supercharger car i helped tune made way more vacuum than yours at idle. perhaps the map sensor seal is leaky or something.

another thing i'd consider is lowering your idle speed timing corrections. it's modulating pretty heavily in neutral. with a cam that size you might want to go 2,2,2,2,2 all across the board, it could really stabilize things (or make them worse, but it's worth trying...)

I second what Steve posted. Close the throttle plates and don't drill holes in the butterflies. Close the butterflies and try to get the BLM counts to even out bank to bank. I'd only really worry about the actual hot IAC counts if you reach a point where the IAC can't open enough to cold start the engine.

The TPS should not require any adjustments. You should never have to drill out the screw holes so you can move it around.

Also make sure the timing table (I'd check VE table too) are relatively flat in the area where the engine idles. Irregularities tend to upset the idle.

Oddly enough, I've found the BLM counts on my engine tend to go a little unbalanced during a cold start if the engine is left idling, like a 15-20 split. But, after a short drive they are balanced within a few counts the next time it idles. I don't even recall my IAC counts at idle. I just closed the butterflies until the BLM at idle balanced better instead of trying to find a "good" idle IAC count.

Ok thanks for all the replys. I will close my butterflies and test some parameters in real time. Then make adjustments in my tables.

Ok, so I got my throttle blades closed to where they were, drilled out my bypass hole to 1/4 inch and my iac counts went to 38 at operating temp. I also made changes to my idle speed timing corrections table using 2's across the board. Also made changes to my idle speed target rpm table to help my idle while in gear. So now when I put car back into park, rpms shoot up to 1500 and then slowly come back down. I also have to push gas pedal in to get car to start. Ive included todays datalog and my current bin, if someone wants to look at it.

Maybe the others have better suggestions but I think you need to modify some IAC parameters that aren't defined in the EE xdf's that I've looked at. Unfortunately the disassemblies that I have looked at are not great so it's going to be a significant amount of work to add those parameters to the xdf.

In the $E6 xdf there are a ton of IAC settings. Specifically I think that "Added IAC Flow for P to D Shift", "Added IAC Flow for D to P Shift" (I'm guessing this one is actually mislabeled and it subtracts not adds), along with "Idle Proportional Term vs. RPM Error" (actually a bunch of tables depending on open/closed loop, drive/park, etc).

Steveo, do you have access to a better disassembly? I looked at the EEXTRA xdf which has a few more IAC parameters so I'm guessing more work has been done on the disassembly for that...

EDIT:

I see now that the IAC stuff is on the t-side and already somewhat commented, so maybe not as hard to figure out as I thought...

This is a XDF with more stuff added. I believe it contains everything that had any kind of call-out in the disassembly. I have no idea if it can help.

http://www.gearhead-efi.com/Fuel-Inj...E-xdf-(EEXTRA)