Anybody ever seen your idc and pulse width spike for no apparent reason?

[Tick]

Tuning a 2008 Z06 with a built engine and twin turbo setup. On the dyno everything works flawlessly. On the street, It has spiked the IDC just for a split second which does indeed over fuel the engine badly. The car almost coughs on the excessive fuel but before I even have time to let off the IDC goes back to normal and the car continues to pull.

This has happened twice. Commanded AFR doesn't change, and the VVE table doesn't have any weird value or spike where it happens. Could this be a bad computer or a grounding issue or something?

I'll post a log and the tune file in a bit.....just wanted to see if anyone else has seen this. This is the second car that I've seen have weird and random injector spikes during wot. The other car that is doing it is just an 0411 pcm in a swap application.

[Tick]

This vette is tuned Speed density using VVE. Nothing wierd happens with any of the sensors....map, ect, and iat are all normal when it happens. Tuning with the double stoich, half flow rate method with my config set up to log Lambda and Lambda err.

[Tick]

Logs, tune file, and the config.

[Tick]

A screenshot if you don't want to download the log files.

[ecotec88fiero]

A screenshot if you don't want to download the log files.

The injector pulse width is just following whatever g/cyl is being measured. Look at the spike in your g/cyl, where and why is it jumping up and then back down. Find where that spike is in your tune(VVE).

[Tick]

There is no spike in my ve table.

[ecotec88fiero]

Remember that the VE table that is generated from either HP or Bluecat isn't actually what the ECM is using. It is using the coefficients generated in its calculation, so smooth on a 3D surface may not matter.

The calculated Cylinder Air Mass just from 2.24 to 3.77 g/cyl. I don't see any sensors causing this, at least on the scanner.

There has to be something going on in the air mass calculation that is spiking your g/cyl. When I build the VE table using HPs stuff, it doesn't happen during a boundary transition in your VVE boundaries that I can see.

Maybe try adjusting that small area of 4800-5000 RPM and 200 kPA on the VVE and see if it does anything?

[Tick]

I could give it a shot, but I have dyno logs at the exact same rpm and the exact same map reading that this occurred and everything was fine. 4900 rpm and 200 kpa....

I've dynoed and tested this car a lot because at one point we had a fuel system issue which would cause the pressure to drop. That problem seems to have mysteriously went away only to develop this new issue which has only happened twice now.

Maybe I'll drop the boost down a bit and see if it will happen...

[Tick]

Since we're on this topic, here is a screen shot of the data log of the other car that had a weird IDC spike and it doesn't reflect a spike in the g/cyl of airflow.....and it only seemed to happen on one bank. Thoughts on that? 0411 pcm scaled tune.

This car has 160 lb/hr injectors running M1 methanol so there is a lot of fuel being injected. Igniting the fuel with LS1 coils was pretty difficult too. The car bent a connecting rod on this pass like it hydro locked. The rod was badly bent but no other rods were visibly bent anyway. This was a pass at the strip....the car made the full pass but developed a misfire about 100-200 ft before the finish line due to the plug melting the strap of which I assume was due to all of the oil getting into the chamber past the rings because of how tilted the piston was.

[ecotec88fiero]

How were both of these tunes scaled?

Does the car log any misfires when it spikes? The O2s don't show a misfire but just something to check.

Sometimes a putting a car back on the street makes any kind of timing or load issue rear its ugly head. I would hate to ignore the spike in the calculated engine load because its directly tied to how much fuel the ECM calculates to inject. I would adjust the VE down 5% and see what it does to the fueling on the street.

I only briefly looked and the tune and scan today while on lunch, if i get a chance late this weekend I will glance at it some more.

I would re scale the g/cyl on the second car just to get a better look or post the scan. Not sure about that one.

[10_SS]

I've seen it spike after messing with transients.. bascially created a situation where I was always in a transient... didnt take much change from stock to do that either. I see lots of posts about this.. and every time I think Yea.. I saw that right after messing with transients...

[Tick]

Well, the first cars tune wasn't 'scaled' really. Double stoich, half flow rate as mentioned earlier just to work around the injector flow rate limit in the tune. The second car using the 0411 pcm had the cylinder volume cut in half, and the injector flow rate cut in half so that I'd gain the necessary resolution needed in the timing table for increasing or decreasing boost levels without needing to rework the timing table constantly.

I have done both of these methods on literally dozens and dozens of vehicles. As for Transient fueling, I normally don't change anything there other than the 'Min Fuel Milligrams' on the earlier ecu's in order to control the over fueling issues associated with very large injectors during decel. Nothing that should have any affect I wouldn't think at WOT.

And on the second car, how or why would IDC spike on just one bank? Cylinder airmass doesn't change during the spike on this one. Would an injector that momentarily sticks open be reflected on the data log? The bent rod looked like it hydro locked......with 160 lb/hr injectors maxed out could it have stuck an injector and hydrolocked on fuel? Methanol is some nasty stuff when it comes to corrosion of the fuel system....maybe an injector stuck?

I haven't tried logging misfires, but neither car was misfiring that I could tell and I imagine that it would be difficult for the ecu to pick up on a misfire at 5000+ rpms too.

Both cars dyno'ed and run great. The first car made 895 rwhp on pure pump 93. It has twin turbos with a 427 cubic inch RHS block based bottom end. The second car is my personal car which is a SBE 5.3 that runs mid 5's in the 1/8 at nearly 130 mph. Misfiring isn't something that I think happened on either of these cars.

[10_SS]

I saw my IDC spike for no reason only once, and that was after playing with the transients... somehow managed to make the RPM or boost ramp say OK to dump allot of fuel in the middle of a WOT run...

[schpenxel]

Log VE airflow

What IAT are you using?

[Tick]

Log VE airflow

What IAT are you using?

I'll try to log that PID tomorrow. Never logged that....

The IAT sensor is an earlier GM screw in style. The scale and the parameters have been changed in the tune file for it so that it reports an accurate value.

[ecotec88fiero]

Log VE airflow

What IAT are you using?

This is a great idea. Should show you if the VE airflow calculation is the cause of your cylinder air mass spike for the first car.

[schpenxel]

Exactly... You should at least be able to get an idea where the spike is or isn't coming from.

I've also read that some of the g/cyl calculations do weird things if you're logging MAF airflow while running in SD mode.. so I usually only try to log whichever one I'm using (MAF g/sec when in MAF only, VE g/sec when in SD)

I would delete out the MAF g/sec PID and just add VE airflow during the next log.

[schpenxel]

You need to cut the IVT coefficients in half since you're using the double stoich/half IFR method.

They are under fuel-->general-->IVT terms. One table is already 0. The other is 7.92. Cut it in half.

Your intake valve temp readings are going sky high (they are estimated, not actually measured)