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josey

Help to setup rev limiter

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Hi guys

i need help with setting up rev limiter on 2.0L drag race car with big turbo.

 

Rev limiter is set to 9000rpm

On LC car spin up wheels and car speed is different than wheel speed, and on shift from 1st to 2nd rpm drops to much and than we are in (black) turbo hole

so idea was to keep engine in rev limit for just a second so car achieve wheels speed, and on shift to 2nf gear rpm would drop to reasonable rpm and boost

 

thing is when i shift on shift light before rpm limiter rpm drops to much - turbo hole

if i let engine to hit rev limiter, it feels like i hit the brakes, so its even worse.

 

I played little bit with advanced rev limiter

and i get better results, i even get 0.25sec better time on 1/8 mile, but car still feels like hitting brakes, just not that hard.

 

settings where

RPM limit mode: IGN CUT

advanced moide : ON

hard limit IGN 100% CUT

cut effect: CONSTANT

limit ctrl range: 200 RPM

hard limit activation: 0 RPM

end cut: 100%

start cut TP 100%: 80%

start cut TP LOW: 0%

tp low: 0%

exit decay rate 5% /20ms

limit ign trim 3

 

and i change it to

RPM limit mode: IGN CUT (but its cutting fuel :( afr going up the sky i have to check why is that happening, yes im 100% sure settings are IGN CUT not fuel cut)

advanced moide : ON

hard limit IGN 100% CUT

cut effect: CONSTANT

limit ctrl range: 100 RPM

hard limit activation: 0 RPM

end cut: 80%

start cut TP 100%: 60%

start cut TP LOW: 0%

tp low: 0%

exit decay rate 5% /20ms

limit ign trim 3 (on ign cut, by manual this should not work?  but its trimming)

 

 

basically i need sharper rev limiter so i can hold car in 1st gear and that engine pulls like it didnt hit rev limitier, i guess you know what i mean, this is often seen on FWD drag cars.

 

so what to try?

to lower limit ctrl range to 50 rpm?

end cut to 70%

start cut to also 70% ?

 

i didnt had much time to play with this, but on next race i will have, and it will be nice to have good directions to start with.

 

 

thanks

 

 

 

Edited by josey

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RPM limit mode: IGN CUT (but its cutting fuel :( afr going up the sky i have to check why is that happening, yes im 100% sure settings are IGN CUT not fuel cut)

AFR will always show lean on any type of limiter.  You are measuring AFR using an oxygen sensor.  If you cut ignition there is no combustion so you have excess oxygen in the exhaust, hence lambda shows lean.

 

It sounds to me like you need a much smooth limiter, it is usually the harsh "hard limiter" effect that makes it feel like you have hit a wall. 

Try something like this:

advanced mode : ON

hard limit OFF

cut effect: Adaptive

limit ctrl range: 500 RPM

hard limit activation: 0 RPM

end cut: 100%

start cut TP 100%: 40%

start cut TP LOW: 20%

tp low: 20%

exit decay rate 20% /20ms

limit ign trim -5

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ok thanks,

its completely opposite settings that i expected to be, but your suggestion seems logic.

 

only thing i dont need is TP low limiter because that car is always 0% throttle or 100% :D

so throttle is like off on 

 

 

regarding lean AFR,

it starts to be lean at 7000 and its lean up to 9000 that was strange for me, and cutting is set at 80% and rpm range is 100rpm

1st and 2nd gear are much much leaner than 3rd and 4th gear for example.

i will investigate more what is happening i will log fuel pressure.

 

thanks for reply.

 

 

 

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Yeah the TP Low limiter doesnt really mater but it is always good to have realistic settings for unexpected circumstances such as throttle stuck partially open etc...

 

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just to to give feedback, and to say thank you to Adamw

 

I started with settings Adamw suggested, and I ended up with this settings and its working good for now, i think i will play more with it in future

advanced mode : ON

hard limit OFF

cut effect: Adaptive

limit ctrl range: 500 RPM

hard limit activation: 0 RPM

end cut: 70%

start cut TP 100%: 20%

start cut TP LOW: 20%

tp low: 20%

exit decay rate 20% /20ms

limit ign trim -5

 

rew limiter is on 9300rpm,

and engine is nicely limited from 8700-8900

 

Adamw, do you have any more suggestions? :)

 

 

 

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bumping old topic,

we didnt drive much, only past month 3 races, i played little bit with rev limiter, and it seems no matter i change it sounds same and on log looks same.

Is it possible to get it smooth as LC? lc seems smooth and soft and it is in 200rpm range

max rpm is 8500 and drops to 7000,  and limit ctrl range is set to 200rpm :(

im 100% sure im doing something wrong since range is 1500rpm :(

i tried with exit decay rate from 5 to 50% ,

ign trim 5 to 10 deg

end cut 70-90%

 

pls help

check attach

 

 

rev limiter 01.JPG

rev limiter 02.JPG

LC 01.JPG

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thanks Adamw

 

and to get it where i want i should end cut leave at 100% and play with start cut, until rpm limiter stays in range of 200rpm?

ign retard leave at 10deg and exit decay rate leave at 20 - 50% ?

 

 

 

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20 hours ago, josey said:

and to get it where i want i should end cut leave at 100% and play with start cut, until rpm limiter stays in range of 200rpm?

I usually leave the end cut at 100%, set the start cut to the lowest setting possible that doesnt cause RPM overshoot.  

Retard and decay are user preference but those are about where I expect.

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