rev cut per gear

Any feature requests for the Syvecs Engine Control Systems
T04GTR
Posts: 51
Joined: Mon Jan 14, 2013 7:37 am

rev cut per gear

Post by T04GTR » Fri Jan 26, 2018 6:56 am

Hello, had to remove the "rev limit" (well put it 200rpm above the rev cut) because the engine hated life with it. knock control going crazy, popping and banging out the exhaust etc etc.
tried ignition type, fuel type, instant and average speed measure and a variety of fuel and ignition cut severity vs rpm error. it just doesnt like it. ignition type is the worst. fuel only seems the least violent, but still sounds like its going to explode..

the "rev cut" on the other hand is 1000 times better. (with no instant cuts and omitting the ignition cut) can sit on it all day and no issues, abit bouncy like an old corolla, but no popping, banging, knock control seems happy and doesn't jerk the engine, (the main issue regarding knock control)
so having a rev cut per gear would be nice, as i cant use the rev limit.
cant race with the rev limit because the knock control picks up cylinder pre ignition and shuts down cylinders if it hit it hard. cant use it for doing a burn out either. look like a tard at the line.. because it smashes off it (all while not arresting the rpm), sound like the exhaust will explode and then runs on 3 cylinders because of the pre-ignition cylinder shut down

or is there some secret rev limit setting im un aware of. i have tried almost everything. i need to have a lower rev cut during a burn out (can do via cal switches)

engine is a vq35hr tt ~900hp@wheels s8 ecu.

Dave.

stevieturbo
Posts: 838
Joined: Sun Dec 07, 2008 2:04 pm

Re: rev cut per gear

Post by stevieturbo » Fri Jan 26, 2018 11:30 am

I've ran my car for many many years...and can honestly barely remember the last time I've hit the rev limiter.

Rev limits are largely a safety feature, not something you bounce off every time you use the vehicle.

Maybe adjust your driving style ?

You can have different rpm limits etc via cal switch per gear so that aspect is covered ?

Have you tried the instant fuel/ignition cut options ? Maybe a wider or narrower hysteresis band ? Altering fuel/ign cut severity ?

Lots of options...but it would be easier and kinder to the engine to not be sitting on the limiter at all

T04GTR
Posts: 51
Joined: Mon Jan 14, 2013 7:37 am

Re: rev cut per gear

Post by T04GTR » Fri Jan 26, 2018 1:09 pm

yes, i understand that. its not like im trying to hit it. but doing a burnout in a car with paddle shift can be a little tricky, especially one thats making alot of power and having a very "revy" nature.
also quite hard to modulate the throttle with big sticky drag radials on a prepped surface. its either spinning or trying to do a back flip.. once its going and im out of the water box i can modulate it. but just the initial start of the burnout is where the dramas are. the engine is not making enough power if it falls out of boost even for a second. once in boost it has to much. very hard to catch.

abit hard to explain. and because its a sequential and has a tall 1st gear and there is only a 1200rpm drop in each gear you need to go up about 4 gears to do a good one. so foot buried, and pluck a few gears and then modulate it. if it gets that far.

but hard to do a burn out on 3 cylinders..

i have tried the instant cuts. doesn't like it. under power, for example on the dyno. lots of knock(probs just engine noise, but the knock control picks it up as a severe event) as the ignition is re-instated.

like i said, why cant the "rev limit" be like the rev cut. ? i would of thought it would behave the other way around.

also, cant have different rev-cut per gear. as the "limit" just doesn't work on my engine combo. i could do a video of what i mean.

stevieturbo
Posts: 838
Joined: Sun Dec 07, 2008 2:04 pm

Re: rev cut per gear

Post by stevieturbo » Fri Jan 26, 2018 4:10 pm

T04GTR wrote:yes, i understand that. its not like im trying to hit it. but doing a burnout in a car with paddle shift can be a little tricky, especially one thats making alot of power and having a very "revy" nature.
also quite hard to modulate the throttle with big sticky drag radials on a prepped surface. its either spinning or trying to do a back flip.. once its going and im out of the water box i can modulate it. but just the initial start of the burnout is where the dramas are. the engine is not making enough power if it falls out of boost even for a second. once in boost it has to much. very hard to catch.

abit hard to explain. and because its a sequential and has a tall 1st gear and there is only a 1200rpm drop in each gear you need to go up about 4 gears to do a good one. so foot buried, and pluck a few gears and then modulate it. if it gets that far.

but hard to do a burn out on 3 cylinders..

i have tried the instant cuts. doesn't like it. under power, for example on the dyno. lots of knock(probs just engine noise, but the knock control picks it up as a severe event) as the ignition is re-instated.

like i said, why cant the "rev limit" be like the rev cut. ? i would of thought it would behave the other way around.

also, cant have different rev-cut per gear. as the "limit" just doesn't work on my engine combo. i could do a video of what i mean.
Because the rev cut....is the be all end all, shut everything down. Rev limiter is up to you to get what settings offer a smooth cut for your engine/setup.

And you need 4th gear burnouts ? Gearing must be very short overall.

But if the only problem here is that knock control shuts you down because of hitting the limiter during a burnout.....Have one Cal specifically for burnouts with knock control disabled. Then switch to whatever cal is your normal.

IMO I find doing that necessary simply so that I dont hit my launch control whilst trying to do a burnout, as that would restrict to a lower rpm than a burnout. ( again this will vary depending where/when/surface etc etc )
So in my case Cal 1 has all safeties, launch, knock etc turned off...so I can use that for all sorts or a fallback if I thought something was wrong. Plus of course use it for burnouts.

Then flick up to whatever Cal is needed for racing. Maybe there is a better way to do it....but that works for me. But in my case the only reason I do it like that is because of the launch/rpm clash for a burnout

And there is bound to be some variation around the rev-limit that will work...it will just take testing to find it.

MReilly
Posts: 22
Joined: Fri Jan 19, 2018 7:05 pm

Re: rev cut per gear

Post by MReilly » Fri Jan 26, 2018 5:03 pm

Re the fuel cuts triggering "false knock"; are you certain it's false?

Just with you saying it's on sequential injection, if the outputs are at all mixed up there's the chance you are giving certain cylinders half a dose (or whatever the split is) of juice is all.

Hopefully it's not that, but perhaps worth a check if it was a late night wiring escapade.

stevieturbo
Posts: 838
Joined: Sun Dec 07, 2008 2:04 pm

Re: rev cut per gear

Post by stevieturbo » Fri Jan 26, 2018 5:20 pm

rev limiters etc are just "noisy" in that respect.

T04GTR
Posts: 51
Joined: Mon Jan 14, 2013 7:37 am

Re: rev cut per gear

Post by T04GTR » Sat Jan 27, 2018 5:46 am

yes, i have a cal for burnouts with no launch. and can turn knock off. but it is just the noisy backfiring violence of the "rpm limit" vs the cut that i have issue with.

eg. car in neutral, rev limit set to say 6500. mash the pedal and all sorts of flames and backfiring out the exhaust.. would wake the dead. all while sending the knock control into limp mode.
same scenario, but rev cut set to 6500. limit to 7k so it does not come on. floor it, and its like a nice oem limiter. not overly loud, and no backfiring. abit bouncy, but nice.

even then, set to 7750 with 0 rpm hysteresis, still touches 8k. and thats just by revving it. not with 30psi of boost up it..

pretty sure its not "pre igniting" Ryan told me its the engine getting "shocked" by the ignition coming back on. very evident during launch control, and heavy tc during traction control. maily just coming out of launch to tc.
but i just want it smooth. there are plenty of other "less advanced" ecu's out there that have much nicer rev limiters. there is no way that this would work on a drift car for example.
im very confident that the injection wiring is as per cylinder. but no harm in checking.. il kill myself if it isn't lol.
i will do a video, the only way to explain it. and perhaps my knock control is to sensitive. but running 98 ron fuel at 30psi there needs to be some safety there.
i will spend some more time playing with it. but i cant see it working nicely.
do you have a strategy for a turbo engine rev limit? ie: what level of fuel cut vs rpm error. and/or ignition cuts?

i invite you to try it for yourself.

Dave.

T04GTR
Posts: 51
Joined: Mon Jan 14, 2013 7:37 am

Re: rev cut per gear

Post by T04GTR » Sat Jan 27, 2018 7:43 am

could the 36-2-2-2 crank trigger be playing a part? theres got to be 1000's of r35's out there. what am i doing wrong. :oops:

stevieturbo
Posts: 838
Joined: Sun Dec 07, 2008 2:04 pm

Re: rev cut per gear

Post by stevieturbo » Sat Jan 27, 2018 8:11 pm

No sense in trying myself...as I've no intentions if sitting on the limiter lol.

But every engine will be different, head, cams, tuning, turbo, whatever...so some engines may just take more work than others.

30psi on 98 should be no problem at all if built and tuned right.

And as for drifting...I've no idea what way Link cuts theirs, but whatever a local guy who builds/tunes a lot of drift cars does...his cars would literally wake the dead when bouncing off the limiter and they do it all the time as they think it's cool making all that noise. It is truly horrific, almost as bad as some Hondas.
I can only guess he is cutting ignition only, which allows masses of unburnt fuel to get ignited all at the wrong times when ignition is restored.

Upload your cal to see if there is anything strange.

Also....is your exhaust particularly loud to start with ? That's bound to play a role in how it sounds to you when on a limiter ?

stevieturbo
Posts: 838
Joined: Sun Dec 07, 2008 2:04 pm

Re: rev cut per gear

Post by stevieturbo » Sat Jan 27, 2018 8:13 pm

T04GTR wrote:could the 36-2-2-2 crank trigger be playing a part? theres got to be 1000's of r35's out there. what am i doing wrong. :oops:
I doubt the crank trigger is a problem...and I'm sure most R35 owners dont sit bouncing off the limiter either ?

But certainly some when on launch control can be loud...some not so loud.

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