MoTeC Global Forum

Hello

I have just set-up a DBW throttle on a subaru to try and facilitate power reduction for sequential gear box shift so as not to have to use ignition retard or cut.
Ignition retard/cut causes an issue with my set-up where i am not running an intercooler and spraying Methanol in the pipe work right after turbo, this fuel air mixture was being ignited by the backfire which blows exhaust vales open while inlets are open and blows apart pipework etc !(apart from other destructive issues at this boost/power level)

Previously i have been using close loop gear shift with a 75 degree retard, with the DBW setup i plan on using some retard(mybe 50degree's !??) and throttle reduction, but it seems the throttle reduction is based purely on timings, not closed loop(next stable gear).... is there a way to make the throttle movement closed loop rather that purely timings?

Any other suggestions to make this set-up work well, i have not had a chance to test DBW shift set-up in anger yet...and will likely get limited testing before event....its very hard to find a venue to test launch and shift with close to 800hp atw. I need to know everything possible so as to shorten the learning curve on getting this working right.

Cheers

Hello,
The system was not designed to rely primarily on throttle position so you only really have the system based on time. The M1 is the only ECU that has the closed loop throttle.

What about drawing some sort of table in the Gear position comp ?....based on gear or gear shift force and ?? or Gear change cut time ?(what is that derived from exactly ?)

oversteer wrote:Hello

I have just set-up a DBW throttle on a subaru to try and facilitate power reduction for sequential gear box shift so as not to have to use ignition retard or cut.
Ignition retard/cut causes an issue with my set-up where i am not running an intercooler and spraying Methanol in the pipe work right after turbo, this fuel air mixture was being ignited by the backfire which blows exhaust vales open while inlets are open and blows apart pipework etc !(apart from other destructive issues at this boost/power level)

Previously i have been using close loop gear shift with a 75 degree retard, with the DBW setup i plan on using some retard(mybe 50degree's !??) and throttle reduction, but it seems the throttle reduction is based purely on timings, not closed loop(next stable gear).... is there a way to make the throttle movement closed loop rather that purely timings?

Any other suggestions to make this set-up work well, i have not had a chance to test DBW shift set-up in anger yet...and will likely get limited testing before event....its very hard to find a venue to test launch and shift with close to 800hp atw. I need to know everything possible so as to shorten the learning curve on getting this working right.

Cheers

Are you sure that's the cause of your problems ?

I've tried flat shifting with my dog box, 3-4 open loop, h-pattern and I cut fuel/spark and retard timing and also inject a lot of methanol and have never had any issues.
Not a Subaru though ( or Motec ). Although I gave up on the flat shifts....as all too often I would miss a gear and that would cause more problems than a good shift ever did lol

If spark/retard is causing you the problems, can you not just cut fuel ?

Trying to use DBW would really seem the slowest control method of all for a power reduction to enable a shift ?

The Gear Up Shift time is reset each time the next gear is achieved. It is probably ok to use this as an axis on your position table.

The channel is started whenever the ECU is powered up and sits at a maximum of 30seconds. When making a change it stays at 30 seconds until a gear change is successful. When the new gear is achieved this timer resets to 0 and ocunts up. It is intended for fuel enrichement based on time after the next gear is achieved. If you made the up shift position based on this you could make sure the position is 0 if the Gear Up Shift Time is 0 up to 2 seconds or so.

stevieturbo wrote:

oversteer wrote:Hello

I have just set-up a DBW throttle on a subaru to try and facilitate power reduction for sequential gear box shift so as not to have to use ignition retard or cut.
Ignition retard/cut causes an issue with my set-up where i am not running an intercooler and spraying Methanol in the pipe work right after turbo, this fuel air mixture was being ignited by the backfire which blows exhaust vales open while inlets are open and blows apart pipework etc !(apart from other destructive issues at this boost/power level)

Previously i have been using close loop gear shift with a 75 degree retard, with the DBW setup i plan on using some retard(mybe 50degree's !??) and throttle reduction, but it seems the throttle reduction is based purely on timings, not closed loop(next stable gear).... is there a way to make the throttle movement closed loop rather that purely timings?

Any other suggestions to make this set-up work well, i have not had a chance to test DBW shift set-up in anger yet...and will likely get limited testing before event....its very hard to find a venue to test launch and shift with close to 800hp atw. I need to know everything possible so as to shorten the learning curve on getting this working right.

Cheers

Are you sure that's the cause of your problems ?

I've tried flat shifting with my dog box, 3-4 open loop, h-pattern and I cut fuel/spark and retard timing and also inject a lot of methanol and have never had any issues.
Not a Subaru though ( or Motec ). Although I gave up on the flat shifts....as all too often I would miss a gear and that would cause more problems than a good shift ever did lol

If spark/retard is causing you the problems, can you not just cut fuel ?

Trying to use DBW would really seem the slowest control method of all for a power reduction to enable a shift ?

Yes i am 99.99% sure that is the cause of my issues ...and issues for many others as well !

There has been a string of flat shift based issues related to sequential shifting not only in motec ecu's !
Issues include spitting out shim under buckets and having the exhaust valves get blown open and collide with inlets, in subaru's and Nissan's i have personally seen. Ignition retard is(or has been !!) the only sure way to get power reduction on a high power/boost application....and it causes a pop...which gets very violent under high power. Just cutting ignition would ensure a massive explosion in manifold etc, just cutting fuel would also...and maybe det and melt stuff !

MarkMc wrote:The Gear Up Shift time is reset each time the next gear is achieved. It is probably ok to use this as an axis on your position table.

The channel is started whenever the ECU is powered up and sits at a maximum of 30seconds. When making a change it stays at 30 seconds until a gear change is successful. When the new gear is achieved this timer resets to 0 and ocunts up. It is intended for fuel enrichement based on time after the next gear is achieved. If you made the up shift position based on this you could make sure the position is 0 if the Gear Up Shift Time is 0 up to 2 seconds or so.

Ok, i think i under stand how to use that...

What about if i used Ign Gear Cut Retard as an axis, would that effectively tie in the DBW movement to the Ing Cut closed loop system ? So effectively once that retard is gone the DBW position is too(based on the table in position translation comp) ??

Ok just had some time to try this out, I have setup a table in DBW position trans comp with GearUST (X)1-2sec and I(GCut) ign Gear Cut Retard (Y) -20 - 0 degree's, zero's in 0 GearUST column, zero's in 0 I(GCut) Row and -100% every where else.

Seems to move throttle when Retard is applied by Gear Change Ign Cut function ....i'm hoping it will therefore work in a close loop fashion along with the retard..?
Can you see any issues with this set-up ?
Are there any limitations on throttle movement in the position comp ?(like 20% max or something)

Any advice on level of retard to use along with throttle movement to effect change ? , from previous set-up just using retard the full 75 degree's was required to get reliable shifts and i think some retard will still be required to get this setup working....just want to stay away from backfire !

I've been cutting fuel/spark and retarding timing in a friends Subaru with Samsonas now for 3+ years and never had any problems ? It's even fairly quiet in doing so ( Syvecs )

Not using any methanol injection on it though.

How much power is this Subaru making ? What sort of retard level and or cut are you using ? RPM on shift ? Boost ?

The flat shift under low power is seemless, even with high power the shifting in the upper gears isn't so rough, its the launch hard wheel spin to 2nd and then to third that's violent no matter how hard you short shift.

I'm not just using Methanol injection, the engine runs on Methanol, has 2 x 2200cc injectors per cylinder and 2 x 2200cc injectors immediately post turbo for charge cooling.

I should have just set the car up with an intercooler....but this combo is just a temp measure until new engine/build is ready that should make 1500hp fly.

It does however work very well using Methanol for charge cooling, i know guys that are making very decent gains/times by turfing the IC and spraying meth.