As a public service, and so I can find it easily in the future, here is information about reducing rev hang from the Deceleration thread. Otherwise, it's buried in 40 pages about how to enrage your neighbors with pops and bangs.
Rev hang seems to be exacerbated with FI, a large intercooler and long piping, my theory is the large volume of pressurized intake charge takes a second to be consumed by the engine after closing the throttle.
pazi88 wrote:
There has been lot of discussion about how to get rid of the rev hang which is present at least in ms41.0. I tried lot of things like using the ms41.2 deceleration maps but I wasn't happy with the result. It was better but still the revs didn't drop as fast I would want. I also played with the Fast decreasing TPS -detection maps, but with those I couldn't get the result I wanted, and in most cases it just made the car undriveable. Like there would have been kangaroo gas in tank
But eventually I found easy way to get totally rid of the rev hang without negative effects:
- First raise the ignition Retard - Decreasing TPS - step size so that the minimum values are 10.
- Lower the Ignition retard decreasing TPS (closed) maps by 10.
- Lower the Ignition retard decreasing TPS maps by 15.
Then flash the new SW and go for test drive. There shouldn't be any rev hang at all. Here is ms41 file you could use to copy the maps:
https://drive.google.com/open?id=0B2EFG ... 1JrTjFhQUk...
pazi88 wrote:
I also did some fine tuning.
I noticed that editing only the "ignition retard - decreasing TPS -step size" -table makes the engine very twitchy when engine is cold (close to 0 degrees Celsius). So I left that stock and edited the "ignition retard - decreasing TPS -step size (ECT compensation) -table so that at -10 and 30 degrees Celsius it's stock. But then ECT at 60 the step size is 5 degrees and then ECT at 82 the step size is at 10 degrees. Now the engine is calm as stock when it's cold but then when it's warmed up, all the rev hang is gone. Just like before.
I also tested the mrf582 suggestion and it works quite well. If I lift of the thortle little bit, the engine pops for some time while decelerating. But if I fully lift off the throttle, it immediately cuts of fuel. It's quite good but maybe little bit fine tuning is still needed.
pazi88 wrote:
I have made some progress. Easiest way of getting rid of the rev-hang in ms41.0 without negative effects just edit the "Ignition retard - Decreasing TPS - Step Size (ECT compensation) to look like this:
(image shows step sizes adjusted to 4.00 at 60 and 8.00 at 82)
No other modifications needed. If it's too aggressive raise the 60 an 82 degree values little bit.
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