: How can I force the revs to hang?
08-03-2011, 12:20 AM
Besides holding the peddle down a tad with my foot, because the exactness and repeatability isn't there for me.
Is it something I can do with low load timing? (which I should be able to do for a narrow RPM range, right?)
With the new LW FW and the FRIM the RPM's drop like a stone during shifts. I'm not used to it and I'm shifting a little slow because of it, zero grinding though, which is nice.
If I could get the revs to drop slower in the 5,000RPM range would be perfect.
08-03-2011, 12:36 AM
I know your asking how to do it through the tune but I want to ask this for my own thoughts.
Wouldn't a light weight flywheel keep your RPM's up during a shift? Less rotating mass means it doesn't slow down as fast right?
08-03-2011, 12:50 AM
Slows down faster actually, less kinetic energy.
08-03-2011, 01:17 AM
create a vacuum leak [;)]
08-03-2011, 01:30 AM
Slows down faster actually, less kinetic energy.
Oh that make perfect sense. Makes it easier to rev up faster but at the same time will slow down faster. Again asking for myself.
08-03-2011, 08:30 AM
Drill a small hole in the throttle plate.
08-03-2011, 10:19 AM
Are you running the idle air comtrole valve ? if yes then change things in the tune and they will slow or hang like crazy depending on what and where you change them
08-03-2011, 01:59 PM
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.
08-03-2011, 07:46 PM
Timing isnt going to stop the idle from droping or how fast it drops
08-03-2011, 07:53 PM
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, 08:17 PM
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, 08:58 PM
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.
09-01-2011, 01:47 PM
Something I posted a while back at the other place, hope it helps
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:
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.
09-01-2011, 08:04 PM
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
09-02-2011, 12:03 AM
^^^^ I on the other hand usually adjust the decay rate to get the RPM drop where I want it.
09-02-2011, 12:10 AM
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 [:D]
09-02-2011, 01:46 AM
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.