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Thread: Dashpot Tuning Questions

  1. #1
    Tuner in Training
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    Jun 2010
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    Dashpot Tuning Questions

    Hi guys. I was wondering if anyone has messed with the dashpot tables under idle to change how the car reacts when you lift off the throttle. I've already removed some airflow from Dashpot Preposition and Minimum and added some to Dashpot Decay. I'm wondering how aggressive I can go before the car stalls when i put in the clutch. I've considered maxing out Dashpot Decay and zeroing out Dashpot Preposition thinking that it will go to the minimum airflow as soon as possible. Along the same lines i'm not really sure how the Dashpot Min (4th gear) tables affect things. i've read that on the EEC stuff it was to prevent clutch stalls on manual cars but was curious if that was the case on the newer cars and if so how it worked. Thank you for any insight.

  2. #2
    HPT Employee Eric@HPTuners's Avatar
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    Oct 2007
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    The logic works the same as before. I have never tried or wanted to try maximizing the decay rate, but I suppose you could try. I think you will find that you need some decay to prevent the stalling. I normally make 10% adjustments to the decay rate each time until I get it to feel the way the customer wants.
    Eric Brooks
    HP Tuners, LLC

  3. #3
    Tuner in Training
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    I'll have to keep playing with it. It seems like i'm only getting a noticeable change by modifying Dashpot Minimum so I was thinking it was hitting the minimum number. Could you give me some more details on the Dashpot Minimum 4th gear tables? All the information I could find was that it had something to do with clutch stalls. Does it use this table when the clutch is in instead of Dashpot Minimum? If so are there conditions where 4th Gear no decel will be used? Both are the same in my tune. Thanks for the info!

  4. #4
    HPT Employee Eric@HPTuners's Avatar
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    When I have some time, I will try to write up some information on how they are all used.
    Eric Brooks
    HP Tuners, LLC

  5. #5
    Tuner in Training
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    Jun 2010
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    Just to follow up. I tried it today. Maxed out "Idle Dashpot Decay" to all 16.00s and zeroed out "Idle Dashpot Preposition" It actually only made a very small difference. I ended up also zeroing out "Idle Dashpot Minimum", "Idle Dashpot Min. 4th Gear", and "Idle Dashpot Min. 4th Gear (no decel). This made the RPMs dive more aggressively. Still didn't have any trouble with stalling on clutch in. I actually still wanted it more aggressive so my friend suggested also making DFCO come in as quickly as possible. This made the biggest difference as the car cuts fuel now as the RPMs are diving.