Rev decay

Author
Discussion

lancelin

Original Poster:

238 posts

128 months

Tuesday 18th May 2021
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When decelerating from 1500rpm with just the engine she’s not super smooth and the engine breaking is a bit too much. I feel a slower rev decay will smooth the deceleration to junctions when lifting off and make the car easier to drive around town etc. I guess a bit more like a modern car. Has anyone else achieved this? I have the canems ecu so I can adjust many parameters. Deceleration from higher rpm is not a problem.

GreenV8S

30,481 posts

291 months

Tuesday 18th May 2021
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lancelin said:
I have the canems ecu so I can adjust many parameters
Are you planning to make this adjustment yourself, or have an expert do it for you?

lancelin

Original Poster:

238 posts

128 months

Tuesday 18th May 2021
quotequote all
Myself...

lancelin

Original Poster:

238 posts

128 months

Tuesday 18th May 2021
quotequote all
I’m thinking it might be possible with the PWM idle valve or some fuel table alteration.

Belle427

9,742 posts

240 months

Tuesday 18th May 2021
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It is best left to someone who knows the system inside out as you can quickly screw the map up by messing with things.

lancelin

Original Poster:

238 posts

128 months

Tuesday 18th May 2021
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I’m not interested in messing with things. Im interested in experienced folk sharing their thoughts.

Belle427

9,742 posts

240 months

Wednesday 19th May 2021
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Have a chat with these guys then.
https://www.lloydspecialistdevelopments.co.uk/

Classic Chim

12,424 posts

156 months

Wednesday 19th May 2021
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Interesting.
Pity COG isn’t here as he’d have something to say on the matter I’m sure but as mentioned above I think it’s only really LLoyds who can answer/ effect changes with in depth knowledge.
I say interesting as my car since MBE install is very responsive to throttle inputs.
That’s what I asked for as I like it from a sports perspective but does require me to use toe and heel a lot but then being a V8 it always did really.

They must be able to add a bit more run on but might need rolling road time for all I know.
My idle is set at 750 and I have no idle controller, it’s all done with fuel/ timing and works great.
If they can effect how many pops and bangs you get on de acceleration around the 2000 revs point they must be able to hold a few revs down to say 1200 or however it may be done.
I think removing AFM creates more air pressure at the butterfly which is part of the reason for after market systems feeling more responsive to throttle control.
It’s quite a restriction really. Add on a Decent new filter and ACT smooth bore air pipe it adds a fair bit more to it imho. My induction roar is louder than before no question and I had no induction mods added at all other than the air pipe.
Good luck as it’s an interesting topic



lancelin

Original Poster:

238 posts

128 months

Wednesday 19th May 2021
quotequote all
Thanks Gents, lloyds are way too far away for me. Shame there are not more canems tuners locally. Also a shame COG has gone. He mastered the canems ecu.
Sounds like Rev hang is undesirable for most modern cars and a way of reducing emissions. The modern car has an electronic throttle body so the ECU can delay how much the throttle closes when lifting off. I only want a small amount of delay at the lower Rev range.

spitfire4v8

4,017 posts

188 months

Wednesday 19th May 2021
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Watch the part of the map that is being traced through as the revs are coming back down to idle and add some advance into those cells .. it's overrun so you can't blow anything up by adding even quite significant amounts .. whatever is in the map at the moment through those cells add say 5degrees .. try it again .. if it's better but you want it even slower decay add another 5, and another 5 until you get what you require.

usual disclaimers apply ...

GreenV8S

30,481 posts

291 months

Wednesday 19th May 2021
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I don't know that ECU, but if it supports fuel cut on overrun make sure it isn't fuel cutting below your 1500 rpm threshold. On production cars, fuel cut would typically end some way above that.

lancelin

Original Poster:

238 posts

128 months

Wednesday 19th May 2021
quotequote all
spitfire4v8 said:
Watch the part of the map that is being traced through as the revs are coming back down to idle and add some advance into those cells .. it's overrun so you can't blow anything up by adding even quite significant amounts .. whatever is in the map at the moment through those cells add say 5degrees .. try it again .. if it's better but you want it even slower decay add another 5, and another 5 until you get what you require.

usual disclaimers apply ...
Thanks for the info. I’ll give it a go. I also suspect some of the uneven overrun is down to gearbox and diff slack.

spitfire4v8

4,017 posts

188 months

Thursday 20th May 2021
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GreenV8S said:
I don't know that ECU, but if it supports fuel cut on overrun make sure it isn't fuel cutting below your 1500 rpm threshold. On production cars, fuel cut would typically end some way above that.
Good point .. if you have fuel cut enabled then no playing with settings will stop the revs reducing at maximum rate ..