Cam Idle Tuning

[MrBearclaw]

Hey Everyone,

I just finished a cam swap on my first LS project, and I'm having trouble getting it to idle consistently. I've really only changed the base idle RPM tables, the BRAF, and I've taken 15% out of the main VE table at 1600 RPM and below. Other than that, I scaled up the injector flow rates to match the 76 lb/hr injectors in the car.

I can't get the car past just sputtering. I'm not sure what to try next to get it to run without potentially causing issues. Any ideas?

The cam is a Summit stage 1, nothing aggressive. The part number is SUM-8715R1 (link: https://www.summitracing.com/parts/sum-8715r1). 222/234 115+3, .600/.575 Lift.

[STAGEUP]

Scan your vehicle with the VCM scanner and post the log. This will easily tell us what is going on.

[MrBearclaw]

Okay, here's a couple logs. On the 1st run it actually fired which was surprising, but it ran very inconsistently so I turned it off pretty quickly. On the 2nd run it failed to get past a sputter when I tried to start it a couple of times like it has been doing. Not sure why it actually came to life the first time, I haven't changed anything since I posted the tune.

[HATEHPTUNERS]

IDLE OVER SPEED TABLE IS JACKED!!!! Fix that NOW.. Then, your IDLE SPARK "IN DRIVE" & "IN PARK" need to match in the 0-400-800-1200 columns, and then in the HIGH and LOW Octane tables they need to be the same as the IDLE spark tables.

[blindsquirrel]

Get the correct injector data before anything else. If there's no data for the injectors you bought (this smells like someone fell for the decapped-injector scam), sell them and find some that are meant for use with the stock PCM. Aftermarket injectors that don't come with data are meant for aftermarket EFI where you pick a flow rate from a drop-down list and send it. The stock PCM is nothing like those systems.

screenshot.29-08-2023 17.15.38.png

You've put in a single value across the whole flow rate table, and if you have the stock 2004 LM7 returnless fuel system, your injectors do NOT flow the same at key on engine off as they do when there's 20" of vacuum in the runners.

You still have stock data for Min Injector Pulse, Offset vs Volts vs VAC, & Short Pulse Adder.

[HATEHPTUNERS]

Maybe something like this;

[MrBearclaw]

blindsquirrel, I do have decapped injectors but I did the decapping and flowing myself. The car also has a return style fuel rail setup because I didn't want to go the Corvette fuel filter/regulator route. Since they are just stock decapped injectors, do the Min Injector Pulse, Offset vs Volts vs VAC and Short Pulse Adder just need to be scaled or changed entirely?

HATEHPTUNERS, I'll work on changing those tables, I wasn't aware that the stock values for the overspeed table could be a problem. I'll post an update after I give it a shot here soon.

[blindsquirrel]

That's what I meant when I called decaps a scam, you've changed everything about the injector characteristics, everything for those other tables are now unknowns.

Decaps with mystery specs will work fine if all you need it to do is WOT on the dyno for a Youtube video to generate clicks.

[blindsquirrel]

http://injectordynamics.com/wp-conte...ingDrilled.pdf

[MrBearclaw]

HATEHPTUNERS, I went ahead and copied that data into my tables and still no luck. Just a couple of sputters and she dies. I'll attach another log here, but it's not much. Any other suggestions?

blindsquirrel, thanks for sharing that article on decaps. I'll read through it for sure, I can always go grab a set of injectors from the local yard.

[blindsquirrel]

https://www.ebay.com/itm/274424906026

[HATEHPTUNERS]

Will the engine RUN if you give it some pedal? I don't understand why you are posting logs where the engine won't start, or dies instantly. We believe you... when you tell us it won't run. Those logs have very little useful information in them. Can the motor run if you pedal it? Have you tried holding the gas pedal down to get it to run and hold a higher RPM than idle?

Why is your MAP Sensor hanging at 39KPA? Key on, engine off, scanning, your MAP should be at, or close to 100 KPA.... Yours.... is not....
As was mentioned above-start with a KNOWN set of injectors, and then update the tune with the correct injector data for the new injectors, and also for your fuel system-either referenced, or non-referenced.
Then, figure out what the heck is going on with your MAP sensor. Then, give us a log with you holding the pedal so the engine will actually run long enough to give us some data in the log. When you get these first things sorted out, we can then provide you with a list of channels to log in your scan that will help us drill down on your problem further.