I enabled launch control on the car the other day (v1.7)... it's set at 5,800rpm & ignition cut. I haven't actually launched the car yet but I have tried just revving it with the clutch in and it works fine, building 10psi. The STRANGE thing is, in 2nd gear, at WOT, the car will stop accelerating @ 5,800rpm and create a giant fireball and insanely loud back-fire noise (identical to a gunshot from a 9mm, no joke). I tried just giving it half throttle in 2nd gear and it went past 5,800rpm with no problem... however, whenever I let off the gas, same result of a huge fireball. I have not tried to goto 5,800rpm in any gear past 2nd yet... and first seems to work just fine... but I may not have tested it enough. Anyone know if this may be associated with the launch control and why this might be happening? Appreciate any input!

 

If your not running Nitrous, use FUEL CUT not IGNITION CUT for the launch control / rev limiter feature..

Ignition cut will result in cutting ignition but unfortunately you'll get raw fuel into the exhaust washing everything down and BLAMMO, big fireball when the ignition and hot gasses kick in again...

 

BTW 5800rpm may feel weird when shifting at high RPM since it'll kick in the cut Immediately when you hit the clutch (at high RPM) BUT its what flatshifting is all about....

 

I understand how flat foot shifting works. The problem I'm having though is that the car stop accelerating (kinda like how fuel cut feels) when I'm @ WOT WHILE in gear, with no clutch in... when at half throttle WHILE in gear, it went past the 5,800rpm but still back-fired insanely loud.

I realize this should be happening with the clutch in, in between shifts... but it shouldn't be happening with the clutch completely out while in gear, right? Any idea why this might be happening?

Also, with injector cut... doesn't that make your car run extremely lean while activating the launch control? I was also told that igniting the raw fuel is what helps spool the turbo and create boost off the line, as long as you're careful with it... I've been told that the risk of screwing things up running crazy lean using injector cut is much higher than blowing anything with raw fuel using ignition cut.

 

Before I get too into troubleshooting, do you have open loop fueling features enabled or disabled?

 

Update:

So after some twerking with it, I realized that the launch control is extremely sensitive and enables when the clutch has *any* weight on it at all... this also includes resting my left foot on it while driving in gear, like I usually do. That's why it was engaging for me.

However, here's my new question... now with the launch control enabled, my car likes to randomly backfire *extremely* loud now and shoot out giant fireballs... it has never backfired this loud before nor shot fire... I'm wondering if this is because of small amounts of raw fuel left in the exhaust from enabling launch control from before and never burning it off? The backfire, I swear, sounds as loud as a gunshot... not as soft as a normal backfire. Also, keep in mind, I'm running my exhaust cutout. Think a backfire this loud can potentially damage anything? I'd hope not =x

 

I recently had the same problem with my launch control set @5500rpm. Launch was fine but it would start cutting out going down the track. The previous week, I had the launch control set @ 5000rpms with no problems. I did some data logs and "LCM", which I am assuming means launch control mode, kept popping up intermitently in the boost column.

 

Launch control is very very sensitive. I kicked it on last night at the track to see how it did but it actually slowed my times down a bit. The reason was it built so much damn boost on the starting line I spun the tires for ever and blew my 60' times. Funny as hell though.

As far as blowing out fireballs this usually just means you are running really rich in those areas where it occurs. I dont know why there would be a corrolation between the Launch Control and getting backfires unless you are using IGN cut instead of INJ. MJ already stated the answer on this one. I blow big back fires all the time when I am driving the car really hard. But I am running pretty rich at above 6800rpms just to be safe. It shouldnt be a big deal but it is awful hard on your CAT, assuming you have one.

If you are getting cut out while going down the track then you are touching the clutch pedal. And believe me when I say just touching it engages rev matching which feels like a massive loss of power.

 

Definately not touching the clutch pedal. Plus the fact that it only cuts out above 5500rpm.

 

I actually started posting some thoughts earlier, but apparently it didn't save them.. I did have to make a small adjustment to my clutch switch because of freeplay on the clutch pedal, I would periodically see LCM and I wasn't touching the clutch, turned out I was hitting bumps and it was enough to open the clutch switch.. so check the switch adjustment if you can.

Can't really ponder much else.. I went back and checked out the UTEC manual, and tried to get some verification to the default setting (Injector/Ignition) cut, I recall in an earlier version of the document they stated its recommended to use injector cut EXCEPT if your using Nitrous.. Simply for the reasons you stated, excess fuel causes giant backfires (At the least) at the worst, its really hard on your Catalytic converter. We all know launch control and flat shifting are really bad on your drivetrain anyway.

To be honest, I don't use launch control, since I prefer to shift at a different RPM than I launch, and we don't have that feature (Different launch RPM than flatshift RPM) But its really rough... And I also have very bad wheelspin problems (wheelspin is good since its less shock on the driveline, but TERRIBLE for your 60' times)

 

i was thinking of tinkering with the LC tomorrow, good thing i came across this thread. does anyone know which type of LC that the stock '05 evo's use? (ign cut/fuel cut) i build about 6-7 psi when i'm on it at a standstill. UTEC overrides it so i'm trying to emulate the same kind with the UTEC software.

btw, jack, when you said you like to shift at a different RPM than when you launch, do you mean you flatshift or does the UTEC rev limiter make your revs drop automatically when the clutch is pressed?

i'd rather just have the launch control for when i'm at a standstill and i'm in first gear with my clutch pressed... i'm not too interested in the flatshifting and such.

 

The rev limiter, and launch control are two different features.. Launch control and flat shift feature are whats controlled by the LC options..

When I launch my car, I prefer to launch at 5500rpm approx, but when I shift, I shift at 6800rpm so flat shifting causes a significant RPM Drop when you clutch in.. I would want the RPM limiter for flat shifting to be closer to 6200 rpm but the launch RPM to be quite a bit lower..

But yeah, the RPM's drop if the rev limit was set lower than the rpm you shift.. If you shift real fast your ok.. If your doing any sort of performance driving besides drag racing, it'll feel "Weird" to say the least..

 

the problem is the launch RPM is the same rpm as the flatshift.. so if you set it low for launching, every time you clutch, it'll hit that limit also.. And "Feels weird" as I said..