Rate of revs falling when lift off accelerator

1. dturbo Infrequent Poster Joined: Jul 2018 Posts: 163

   #1 13th November 2018, 10:00

   Hi all,
   
   Just checking something. I have a VTS and my son has a 1.1 desire. On his car, when you blip the throttle, or also when you change gear, the revs drop pretty quickly . Makes it a bit tricky to rev match actually. On my VTS the revs drop much more slowly - to the point that it's quite easy to end up with a little rise in revs between gears if you don't remember to lift off the throttle first.
   
   Do others find this with their cars? Is it a deliberate thing or maybe a difference in intakes?
   
   I find that on most modern cars, the revs are slowly lowered, I've always thought it is to help 'lazy' drivers that don't have any interest in trying to change gear smoothly, but that wouldn't explain it in terms of my VTS which is 18 years old
2. aldred309uk Frequent Poster Joined: Feb 2014 Blackburn, Lancashire Posts: 596 2002 Citroen Saxo desire 2001 Volvo V40 1.9D

   #2 14th November 2018, 19:02

   My 1.1 drops the revs pretty quickly. Less rotational mass I would assume so loses speed quicker?
3. MartinObviously Saxperience Forum Bum Joined: Dec 2012 Perth Posts: 3665 Peugeot 106 1.1 Turbo Peugeot 106 1.5D Turbo Peuge

   #3 14th November 2018, 19:43

   Quote:

   Originally Posted by dturbo Hi all, Just checking something. I have a VTS and my son has a 1.1 desire. On his car, when you blip the throttle, or also when you change gear, the revs drop pretty quickly . Makes it a bit tricky to rev match actually. On my VTS the revs drop much more slowly - to the point that it's quite easy to end up with a little rise in revs between gears if you don't remember to lift off the throttle first. Do others find this with their cars? Is it a deliberate thing or maybe a difference in intakes? I find that on most modern cars, the revs are slowly lowered, I've always thought it is to help 'lazy' drivers that don't have any interest in trying to change gear smoothly, but that wouldn't explain it in terms of my VTS which is 18 years old

   Revs drop slow in modern cars to help with emissions. it's electronically programmed to do that.
   
   a VTS is not, it sounds like you might have a slight air leak somewhere or a sticking ICV.
4. Chipwizards Frequent Poster Joined: Nov 2009 Posts: 576

   #4 17th November 2018, 22:14

   They all shut the injectors off on overrun, even very early injection cars from the 1980s.
   If your VTS doesn't cut on overrun it's likely that the throttle pot is either not connected correctly or faulty.
5. dturbo Infrequent Poster Joined: Jul 2018 Posts: 163

   #5 18th November 2018, 09:01

   Recently changed out the TPS as the one on the car was reading spiky resistance values over it's travel and the car was hunting / misfiring on light load. Idle's and drives fine now. I know about cutting injector drive on overrun, but does that include when the car is stationery and being revved in neutral? I would have thought in that situation the ECU would not completely cut injector drive?
   
   Tbh I have listened to quite a few VTS being revved (usually demonstrating a new exhaust) on youtube and it seems about right. I have a lexia setup coming next week so I can get some info from that.
6. dturbo Infrequent Poster Joined: Jul 2018 Posts: 163

   #6 19th November 2018, 13:21

   I've taken a wee video of me revving the car, just out of curiosity. Pretty sure it's fine, certainly seemed to be going well when I matched a friend in a >200hp BMW up to... well a fair speed shall we say!
   
   http://imgur.com/gallery/NjBqp2D