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Thread: How can I force the revs to hang? Reply to Thread
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Topic Review (Newest First)
09-02-2011 01:46 AM
aprophetofone this would be nice with a flip chip setup.

what parameters would need to change to smooth things out? sitting in first gear in traffic sucks.
09-02-2011 12:10 AM
illinipo The preposition is really fun to play around with and also very important in autocross and road racing. You can tune how hard it hits when the throttle closes for inducing oversteer on entry or transition. Too hard though, and it can be a little scary on the street
09-02-2011 12:03 AM
03OrangeSVT ^^^^ I on the other hand usually adjust the decay rate to get the RPM drop where I want it.
09-01-2011 08:04 PM
1turbofocus If it was me I would play with the ISC Daspot gain in scalars , this is what controles the flair when you push in the clutch , done slowly this would slightly lift the rpm when you went to shift or at least hold or slow down

I would start there vs the stuff listed above

Tom
09-01-2011 01:47 PM
illinipo Something I posted a while back at the other place, hope it helps

Quote:
Originally Posted by illinipo

This has to do with dashpot. It is a hard topic for a lot of people to understand (mostly because the way it is usually described). This topic alone could be its own thread.

There are 3 important dashpot parameters:

preposition
decay rate
clip

The dashpot will "fill" up to the preposition value in part throttle or WOT. This is how much air the IAC valve lets in when you let off the throttle. Changing this will control how hard the car bucks or how stiff or light the car engine brakes IMMEDIATELY after letting the throttle off.

Then the decay rate comes into play. The decay rate changes how quickly the dashpot ramps down to the clip value (it is a power law regression re-calculated 26 times a second). Changing this will control how hard the car engine brakes during coasting. It can also cause the problem you have of the car dying when you put the clutch in.

The clip value is the minimum amount of air to send through the ISC valve on decel IN ADDITION TO the ISC Netrual Idle Air table... So you basically want to set the dashpot clip 1 to all 0's unless you want hanging rev's. And who the hell wants hanging rev's???

One caveat to setting clips to 0. This caveat requires you to know that the ECU switches from dashpot mode to idle mode at 10mph. I had to set the clip at 0 rpm to a small value like 0.0200 to prevent the car from dropping under idle speed if I crossed over 10mph as I was putting in the clutch.


Dashpot is the thing I have spent the most time on in my tune. It is a serious aid for drivability tuning. The car engine breaks and idles down exactly how I like it, how quickly I want it to, so I'm not wasting clutch material bringing the revs down or needing to shift too quickly to avoid going down to idle between shifts.
08-03-2011 08:58 PM
iminhell So "Dashpot Adder With RPM" or "Dashpot Decay Rate" might be the ticket?

Haven't played with that yet because I really don't understand it. But if it's based on RPM I'd be happy.
08-03-2011 08:17 PM
Paladin I can see why. In traffic civility has gone away a bit in my svtf since I did the lightweight flywheel. It's just the nature of the beast. All I can suggest is to practice your throttle control till you and your car know what eachother wants. I had to completely re-learn my driving style after the flywheel.
08-03-2011 07:53 PM
sleepyboy I think this is funny. Something we strive to get rid of on our cars is something your trying to get back lol.
08-03-2011 07:46 PM
1turbofocus Timing isnt going to stop the idle from droping or how fast it drops

Tom
08-03-2011 01:59 PM
iminhell There is a hole in the throttle plate. It's a Mustang GT throttle body, 70mm.

Yes I'm running an IAC. I was hoping to not have to adjust it from where it is now, it works awesome as I have it now. And I'd like to get the revs to hang just during shifts near specific RPM's. The IAC can't do that. Which is why I'd hoped timing could.




There's what my low load timing is right now.
Stock is ~55 down to 3K, then drops down to ~45.
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