Flatshift rev limiter and rev matching on down change
 

Hi, in the process of installing / tuning the flatshift function with my MS2V3 ECU, using the top clutch switch to activate, to use when up shifting.

I am going to install a switch inline with the clutch switch to be able to turn this function on and off as I want. A toggle switch in the tombstone or similar.

My intention is to set the flatshift limiter to somewhere in the 5000-5500rpm range (need to do some maths to get the final figure)

What I was concerned about though is when rev matching on track on down changes, activating flatshift when not required and limiting the ability to rev match over the 5500rpm flatshift limiter.

I.e. Accelerating on straight ---> brake for corner, revs drop to 5500rpm ----> clutch in to down shift, ECU sees clutch switch in activates flatshift rev limiter ----> throttle blip to increase revs for next gear, target 6500rpm to match to next gear, but because flatshift is engaged rev limiter is at 5500rpm revs cannot rise above that to match the next gear.

Thanks to Covid19 I can't just go out and test the theory, and it was mentioned in passing on the Carpassion Channel by Greg.

I would really rather not have to manually switch launch / flatshift on and off dependant on if I am speeding up or slowing down. Particularly on track that would be a PITA. i could most likely make an additional automatic switch in the MS to do something using TPS % to do something to differentiate between a flat shift and a downchange throttle blip, but seems like overkill.

Is the above actually an issue or am I overthinking? Has anyone encountered an issue this before?

I would really like to use the flatshift. I have a supercharger with a dual throttle setup with the mini bypass valve. At high rpm up shifts I can just hear the belt chirping as the supercharger stalls, even with the bypass. I actually broke the crank pulley off the crank on a trackday last year on an upshift. Much fun was had. Being able to keep the throttles open will mean the SC won't be stalling every upshift and it will be kinder on everything involved.

Tom

It's been a while since I played with flat shift settings but I remember having issued running into the launch control rev limit when down shifting. I don't remember really having the flat shift rev limit being an issue. Can you set a flat shift arming rpm at 6500 or something so that flat shift won't be active below that?

Actually thinking about it the launch control rev limiter could be even worse for this. I would set it to about 3500rpm and I cross this rpm all the time down changing during normal street driving.

There is a function on the launch control settings in tunerstudio 'enable launch when tps above %'. I guess I could log what %tps I typically use for a lower rpm rev match and set it above that. I would be surprised if I used more than 20% in the 3500rpm range, but would need to check. That should overcome any issue with the launch control limiter.

I don't know if the tps% control above also applies to flatshift - if it does maybe it could be used to differentiate between a true flatshift and a downchange throttle blip.

I think that setting the f/s arming rpm to 6500 could cause an issue if the hard limiter was below it? The revs would drop out the f/s zone on the way to the target and so disengage itself above the target rpm, and so just bounce around at the arming rpm instead of the target - just hypothesising - but that would be annoying.

I was thinking a workaround would be changing the inline switch from a dash mounted toggle to a steering wheel mounted push button. That would be relatively easy to manage while driving on track, but still one step more than I would like in an ideal world.

Tom

I have enable launch at 90%. Never have an issue with rev matching. Don't use flat shifting though, so that might be an issue. Worst case, use a launch enable toggle switch

I think that is where I am at the moment. Looking at steering wheel mountable momentary push buttons to engage launch / flat only when I want it.

You can disable launch above X speed. My speed is set at 4kph so launch is disabled above that speed. This is to allow flat shift without launch interfering.

I’m on MS3. Pretty sure flat shift is only implemented when clutch is disengaged while TPS is near 100%, not in reverse order.

Flat shift is for drag strip, not road track.

i have launch, flat shift both on all the time. I rev match on downshift. The MS3 does not confuse them.

I can upload my settings later.

if MS3 and MS2’are different, then I cannot make MS2 recommendations.


https://cimg0.ibsrv.net/gimg/www.mia...4451e66652.png

Settings look pretty similar tbh, if you ignore the rh side of your menu above with the transbrake settings etc.

Only additional setting you have relating to flatshift is the disabling of this function when below a certain speed.

If it is the case that there is already the requirement for the tps to be at or nearly at 100% for it to activate that would be great. It's just it does not seem to have an editable parameter in tunerstudio. Maybe it is in the firmware somewhere - no idea personally - be good if someone could confirm.

If it does then that would distinguish a full throttle upshift from a small throttle input to match revs on a downshift and there would be no need for an extra button on the steering wheel which I would be happy about.

I would get the car out and give it all a go, not sure the police would call testing this an essential journey!

On the drag racing / road track comment - my understanding of this is that it is usually used to keep a turbo spun up during a gear change, and so for full boost to return quicker when the change is completed. I can see that being of benefit to both forms of use.

I am trying to use it for a different reason - to avoid my supercharger spinning at max rpm suddenly coming up against a wall of air when the throttle downstream of it snaps shut on a change. When I rebuilt the engine after the crank pulley got torn off on track last year during a gear change I tried going to a single throttle setup (ahead of the blower). It would not idle properly, had horrible idle droop and massively delayed throttle response when the throttle was closed. This is with an over the rad air to air intercooler. So I went back to dual throttles but looking at ways to avoid the above happening again.

95% TPS is stated here.

Lots of opinions on how hard on XSMN flat shifting is. That is why I suggested limiting to drag racing.

DNM

No reason to think the Adaptronic would be much different in that respect, fingers crossed. Thanks for digging that out.

XSMN = exhaust manifold? I plan on keeping it civil and cutting fuel and spark so hopefully keeping the explosions inside the engine will help that. I must be getting old.

XMSN = transmission

It does sound like you are overthinking it.

When accelerating, you have it so flat shift activates at say, 5000 RPM, then you hit 5000, flatshift is now enabled, go to redline, press clutch, engine revlimits to next gear, and flatshift as expected

If you are decelerating, and you are at 4000, and need to blip to rev match, you are not above 5000 when you press the clutch, so the criteria for flat shift will not be activated. Flat shift should not activate as you cross the 6000 rpm threshold as long as you are holding in the clutch.

Same thing with the TPS % criteria, do some data logs, and see what maximum TPS % you reach when rev matching, and set it higher then that for flatshift activation.

oops, DNM misspelled the abbreviation.

Sooo....

Managed to get the launch and flatshift all wired up and after a minor hiccup not realising the gearbox neutral switch was also wired to the clutch switch got it working.

However the launch / flatshift limiter did interfere with down shifting atleast with the MS2/Extra release 3.3.3 20141112 firmware. I've asked the question whether anything was updated at all on later firmware on the MS forum.

I found that the activation TPS % affected both launch and flatshift modes, rather than just launch. I checked in Tunerstudio that when I was making a flatshift the MS recognised it as a flatshift, rather than a launch.

When I set the activation TPS% low at say 10% downshifting rev matching was impossible, the MS cut the spark and ign as soon as I pressed the throttle to increase the revs above the flatshift limiter.

With a higher TPS% of say 80% it got rid of most of the downchange issues (I still hit it a couple of times with a couple of throttle blips at higher rpms). But having the TPS% that high for launch is way to brutal for my liking, particularly if I was trying to use it in the wet.

So long story short I put a momentary switch on the steering wheel, inline with the clutch switch. It works well and means I can run a low TPS% activation.

I the button on the wheel might look a bit out of place but I think it looks alright.

Also, flatshift is brilliant. It actually feels smoother than a normal 'spirited' up shift. I also haven't heard any squeeks from the charger belt that I used to hear, suggesting that I am no longer stalling the charger on upshifts which can only be a good thing. Looking forward to trying it on track when the madness is over.

Tunerstudio settings below. Arming RPM a few hundred above idle as recommended. Quite a low flatshift limiter RPM of 3500. Seems to work well from the very limited testing I have done. The revs seem to drop the 1000 - 1500 rpm or so required in about the same time I can make the shift anyway. It means that shifts anywhere from 4500rpm up to 7000rpm redline can be made with flatshift pretty smoothly, rather than setting the limiter higher at say 5500rpm and it only really working well for 6500-7000rpm shifting.

https://cimg3.ibsrv.net/gimg/www.mia...ec6033616a.jpg


Some pics of the button on the steering wheel in case anyone is vaguely interested.

https://cimg7.ibsrv.net/gimg/www.mia...c93a4c570b.jpg
https://cimg0.ibsrv.net/gimg/www.mia...acb150d24c.jpg

I only have experience with MS3 and not MS2 but on my MS3 I have the launch disabled at any speed above 5mph. Above 5mph the logic only looks to allow flat shiting.

I would move the flat shift arming RPM up a fair amount. Unless you're trying to flat shift at 1700 rpm there's no need to arm it so early. Beyond that, I would increase tps% for launch pretty significantly. Really if you're not going at or near 100% throttle then there's no reason to have launch active. I think mine is near 50%. If you have it at 10% then any throttle blip with the clutch pressed is likely to activate the 3500 rpm limiter for launch control.

Basically you're setting up a series of if/then statements. Here's an example configuration:

Launch Hard Limit: 3500
Enable Launch TPS%: 50%
Flat Shift Arming: 4500
Flat Shift Hard Limit: 5000

So it determines what to do based on these settings and the current condition.
-If you press the clutch in and you're below 3500 rpm it's looking for launch control. If you then give over 50% throttle it would activate the launch control mode. If you don't hit 50% throttle then it should rev freely.
-If you press the clutch in and you're above 3500 rpm but below 4500 then nothing should happen unless you exceed 50% throttle. Above 50% throttle and below 4500 rpm is going to bring the limiter down to 3500 rpm.
-If you press the clutch in and you're above 4500 rpm then it's looking to apply the flat shift rev-limiter. It's going to set a 5000 rpm limiter with the timing retard you specified.

Another thing to note- The timing value in the table is absolute. It's not how many degrees of timing it's pulling. Your settings look to me like you're thinking it's an adder (or subtractor).

Yeah, I don't see an option to do it on wheel speed in my tunerstudio - and I don't have wheel speed sensors - so I think RPM for me. Seems to work fine anyway.

@nickalltogether - I know what you are saying.

On TPS% for launch it is just the minimum throttle required, so it is quite nice to be able to slowly roll onto the throttle to bring the revs up to the launch limiter, set your throttle position for the launch and then go. Just a personal preference I guess. I think if I set it higher, say 50%, you would have to very quickly get the throttle to above 50% to avoid not meeting launch and just revving the engine. I also know when I did a wet sprint day once I was pulling away with less than 50% throttle to avoid just sitting there with wheels spinning. I don't really want to have to adjust it all the time dependant on conditions.

On flatshift arming rpm - I wouldn't be flatshifting at 1600rpm, but equally not sure it is doing any harm there either, if you just shift normally coming off the throttle lower in the rpm band it doesn't meet the flatshift req anyway.

The issue I thought I would / did run into was the downshift. I tried a run with a higher flatshift limit (5500rpm) and higher TPS (80%). It worked better for the majority of downshifts. It was fine down changing at about 4000rpm, rpm only went back up to approx 5500rpm and throttle used was less than 80% on the blip, but I still bumped into issues above that. It's really off putting if you do accidentally trigger it expectantly and I noticed that some of my throttle blips were actually far larger than I originally thought they would be.

On the timing - yes it is absolute. What timing do you run? I'd read that 5-10deg BTDC was the sweet spot to not go bending bits. Its not got the pops and bangs of running ATDC timing but it seems to do the job

I follow you, your wet condition criteria makes you a bit of an unusual case I guess. Your button solution may be your best bet- excellent looking interior by the way.

I think I'm at 0 degrees on launch and 5 degrees (maybe 10) on flat shift. Fairly noisy for launch, but I like it and the short nose 1.6 doesn't have much value to me to justify babying it. The flat shifts are very smooth though, feels like less abuse than shifting quickly in the "normal" way to me.

My ms3 derives vehicle speed based on the hall effect sensor in my gauge cluster that is there to power the cruise control. There is a write up on what value you need to give it to get accurate information. My vehicle speed is pretty accurate until about 75 mph and the sensor loses resolution. But I think that might be a function of this current gauge cluster. My old cluster didn't lose / get mixed up info at that speed.

It's not ideal but it atleast it only allows activation when I want it. Thanks BTW. I was wondering about doing something with and inline switch in the MS, probably something to do with TPSdot to try to differentiate between quick blip of the throttle on a downshift and not activate, but still activate on a stable 100 TPS% on a flatshift and a slower TPS change for gently adding throttle for a launch but I will leave it for now and test it more first.

I was really surprised how smooth the flatshift is also. I also didn't expect the car to feel any quicker but it does. My car is supercharged rather than turbod, so lag has never been a consideration, but there is a small delay while the bypass valve opens and closes. With the throttle pinned open there is no delay at all and you can feel the difference for sure.

​​​​​​​Ah cool that is good to know