Massive Bog When Launching

[phil123]

Brought the car out to the track last night for the first time since last year. Only change is a new stock clutch with about 1,000 miles on it installed by Ford dealer. Engine and car stock except some BMR suspension parts and Ford racing springs. MPSS tires stock sizes. I launched same as always traction control in sport mode, hold brake on and hit TC button twice, and launch control set at 3100. Immediate cut in of clutch protection when engaging clutch 3.167 60 foot and 15.2 ET. Nothing wrong with engine once protection came off as I had a 107.5 mph with that terrible ET. I did a total of four runs and gradually reduced the RPM on launch control which helped a little. Final and best run was all the way down to 2500 but even that was a pathetic 13.8 115.72 mph. In the past biggest problem was controlling wheel spin not this. Was going to try a run with no launch control but this being the always crowded Sonoma Raceeway I only got four runs between 3:15 and 6:30 and had enough.

Would appreciate any thoughts.

Thanks

 

[paluka21]

Well, in all honesty it sounds like two things are happening:

1) the clutch protection is kicking in obviously causing your car to be limited on it's launch, and making it nose dive. This is common and unfortunately how these cars behave in stock tune form. Anytime the PCM detects clutch slippage, the clutch protection kicks in limiting throttle.
2) you most likely need practice with your technique. There is no way the best you should run is a 13.8@115mph. I'm not knocking you at all, just saying you need some practice with your technique.

So, with that said, are you dumping the clutch off the line, or riding/slipping the clutch?
What RPM are you shifting at through the gears?
Are you flooring the car even when you're spinning?

 

[phil123]

I take no offense but this hasn't happened to this extent in the past and my technique hasn't changed. I don't dump the clutch and flooring it while spinning is not at issue because the power is cut as soon as the clutch starts to engage. Once again shift points are not the issue. It won't leave the line with any power. Once the power cuts back in things are fine but I have lost several seconds. Power is cut and it basically limps off the line.

 

[rwboring]

i'm not sure what was happening when my car was 100% stock to the tires i used LC in sport mode and could get 2.2's consistent... i'm not saying it wouldn't bog at all over a 3 second 60ft is crazy

 

[phil123]

I agree and I don't understand why it has changed all of a sudden unless the new clutch could have something to do with it.

 

[paluka21]

I agree and I don't understand why it has changed all of a sudden unless the new clutch could have something to do with it.

Its possible the PCM is detecting clutch slippage and keeping the car held back with clutch protection well into your run. a 3+ second 60' is absolutely crazy.
Question for you: Can you replicate this on the street? If so, I'd almost consider taking it to your dealer and showing them how the car is behaving.
Clutch protection does really suck. I tried 0-60 in my car and best I could do currently is 4.5 second -because- of clutch protection. On stock tires the car did a best of 4.0.

 

[GOTSVT?]

TC off, launch out of the hole from idle, after quarter throttle I mat it.
Get some drag radials on as well.

 

[phil123]

so no launch control?

 

[GOTSVT?]

No launch control
You will bog. The electronic nannies and features
Are only good for so much.

 

[Lethalchem]

No launch control
You will bog. The electronic nannies and features
Are only good for so much.

Yes, but even with the nannies engaged he should not be running 3+ sec short times. That's what is confusing. I can leave my car in sport, set LC at 2500, floor it, dump the clutch and it still get a 2.3 60'. His time is odd.

 

[phil123]

It is very odd and not a problem I had before. That is why I am wondering if the new clutch could have anything to do with it even though it doesn't seem to make sense. The 60 is bad because it was cutting out almost immediately on launch and just limping until power came back. Previously with street tires my biggest problem was to much spin if I wasn't careful now all of a sudden this change to the opposite.

 

[COOL COBRA]

I'm no drag racer but like to leave the line when I want without bog. I did the obvious, more RPM. Step it up, maybe as much as 4500+. Slip the clutch a little if you have tire, then nail that bitch.

 

[heatsoaked12]

Op these guys aren't getting it. I have had exactly what you're talking about after my rxt install. Slightest chirp after a clutch release and flat out loss of power. Then so very slowly power comes back on. while I don't have an answer for you it has gotten better after another thousand kms of driving. I think the computer needs to relearn the drivetrain all together. Of course I also added an aluminum flywheel. Il be watching closely to see your results. Perhaps a crank relearn is needed in our casses.

 

[phil123]

Op these guys aren't getting it. I have had exactly what you're talking about after my rxt install. Slightest chirp after a clutch release and flat out loss of power. Then so very slowly power comes back on. while I don't have an answer for you it has gotten better after another thousand kms of driving. I think the computer needs to relearn the drivetrain all together. Of course I also added an aluminum flywheel. Il be watching closely to see your results. Perhaps a crank relearn is needed in our casses.

Yes this sounds pretty close to my experience although I have about thousand miles on already but did no hard launches during that time. And yes my flywheel was replaced with another stock flywheel. The damn thing just dies coming off the line.

 

[Smokin04]

Sounds like you need a tune to turn all that crap off.

 

[paluka21]

The damn thing just dies coming off the line.

Yep, thats the clutch protection killing your momentum. It is successful at protecting the clutch from getting smoked, ;-) but does not allow the car to accelerate anywhere near its capabilities. I went out today to experiment and found that with all nannies turned off, the car would launch hard, transfer weight then nose dive and power would drop off significantly until I got to the upper rpms of 1st. It really didn't matter what rpm I launched from, the car would behave the same, accompanied with a strong smell of the brakes. (or clutch perhaps) If I dropped the hammer at 15mph in 1st gear, the car would take off as it is supposed to, but it just can't be launched without the clutch protection ruining the run, without a tune to remove the feature. Stock tires, you often will not get this behavior because of wheel spin.

 

[heatsoaked12]

Yes this sounds pretty close to my experience although I have about thousand miles on already but did no hard launches during that time. And yes my flywheel was replaced with another stock flywheel. The damn thing just dies coming off the line.

Im talking about another thousand miles. mine took about two thousand kilometers before behaving like it did before the swap.

 

[HighTorque]

Any resolution to this i am experiencing the same issue on mine.

 

[phil123]

Yeah a tune cured it.

 

[HighTorque]

yeah a tune cured it.

nice have you taken it to the track since then? What kind of times are you seeing?