[DBecker]

I just read about that device.

Does it really momentarily cut the ignition voltage to kill engine power while you shift?

If so, that's horrible. I'll bet the ECU sets every error that it has when that happens.

 

[TobyB]

Better question is why would you use a flat shift with an H pattern shifter. Sequential gearbox is a no-brainer

because you're required to by your class rules.

It was rather surprising to me how much I lost at Portland without the chicane
by NOT flat- shifting behind someone who was. When we later compared our
acceleration curves, our engines were matched- the steps in my curve
made all the difference, and I was 20 car lengths behind, and significantly out
of the draft.

t

 

[TobyB]

Btw the thotle signal has not been altered at all, the signal is need to know if I pushdown the pedal (uses as a reference).

Sent from my CLT-L09 using E46Fanatics mobile app

Huh, you're right- but I agree with DBecker, that's gotta be lighting
up the misfire detection in the ecu.

I couldn't find any info on how it does the launch control- if it's
sitting you on a spark limiter, it's gonna mess with mixture control
something fierce... with a carbed car, I have fun with the spark cut,
'cause you can make a bloody great flame out the tailpipe.
With a computer that's obsessive about mixture and misfire,
this seems like it's poking a hornet's nest with a very short stick.

t
not trying to be discouraging,
just... skeptopotamus.

 

[604Beamski]

Isn't there a way to "tune" a stock launch control option on MS43 cars? https://www.youtube.com/watch?v=BFwdIiqxtbk
I'm assuming OP's way is either easier or his car is not MS43?? I am not versed in engine tuning for these cars, just trying to help and learn

 

[Overboost]

because you're required to by your class rules.

It was rather surprising to me how much I lost at Portland without the chicane
by NOT flat- shifting behind someone who was. When we later compared our
acceleration curves, our engines were matched- the steps in my curve
made all the difference, and I was 20 car lengths behind, and significantly out
of the draft.

t

You realize a proper flat shift system simply kills spark to take the torque off the gears to allow the shift to occur? Our flat shift cuts ignition for no more than 80ms and we use a sequential box and this allows a perfect upshift. I am totally lost on what you are trying to do with flat shifting a h pattern box. Makes no sense.

 

[Siv1997]

I just read about that device.

Does it really momentarily cut the ignition voltage to kill engine power while you shift?

If so, that's horrible. I'll bet the ECU sets every error that it has when that happens.

Depends, if you flash your ecu then you can get past with the engine error code. I set my miss fire detection up to 2500 and does not detect miss fire past that set rpm.

Sent from my CLT-L09 using E46Fanatics mobile app

 

[Siv1997]

Isn't there a way to "tune" a stock launch control option on MS43 cars? https://www.youtube.com/watch?v=BFwdIiqxtbk
I'm assuming OP's way is either easier or his car is not MS43?? I am not versed in engine tuning for these cars, just trying to help and learn

My car is a ms42 so there is not really a setting for that.

Sent from my CLT-L09 using E46Fanatics mobile app

 

[Siv1997]

Huh, you're right- but I agree with DBecker, that's gotta be lighting
up the misfire detection in the ecu.

I couldn't find any info on how it does the launch control- if it's
sitting you on a spark limiter, it's gonna mess with mixture control
something fierce... with a carbed car, I have fun with the spark cut,
'cause you can make a bloody great flame out the tailpipe.
With a computer that's obsessive about mixture and misfire,
this seems like it's poking a hornet's nest with a very short stick.

t
not trying to be discouraging,
just... skeptopotamus.

My miss fire detection is set up to 2500 any thing past that it will not be reconized as miss fire.

Sent from my CLT-L09 using E46Fanatics mobile app

 

[TobyB]

You realize a proper flat shift system simply kills spark to take the torque off the gears to allow the shift to occur? Our flat shift cuts ignition for no more than 80ms and we use a sequential box and this allows a perfect upshift. I am totally lost on what you are trying to do with flat shifting a h pattern box. Makes no sense.

You realize that a flat shift itself is simply where you use the CLUTCH to decouple the gearbox? Foot 'flat' on the floor?

The engine then sits on the rev limiter, you slam it into the next gear, and dump the clutch.

The energy in the engine and flywheel then is added to your forward momentum.

It is not particularly mechanically sensitive.

It DOES reduce your lap times statistically, in a class (SpecE30, for example)
where the cars have to remain stock. And are very closely matched.

That's all...

t

 

[TobyB]

My miss fire detection is set up to 2500 any thing past that it will not be reconized as miss fire.

Sent from my CLT-L09 using E46Fanatics mobile app

Hmm, sorry, then I'm lost, too....

t

 

[Overboost]

You realize that a flat shift itself is simply where you use the CLUTCH to decouple the gearbox? Foot 'flat' on the floor?

The engine then sits on the rev limiter, you slam it into the next gear, and dump the clutch.

The energy in the engine and flywheel then is added to your forward momentum.

It is not particularly mechanically sensitive.

It DOES reduce your lap times statistically, in a class (SpecE30, for example)
where the cars have to remain stock. And are very closely matched.

That's all...

t

LOL, that's not a flat shift that's a speed shift. Flat shift is an ignition cut for a defined amount of time with WOT allowing the next gear to be engaged. We use a strain gauge on the shift lever and a gear voltage potentiometer to accept the gear position before allowing the ignition to be phased back in. We also provide throttle blip downshifts as well, it's all in the programming.

You might not want to try to explain racing to me, my job is professional motorsport electronics.

 

[jfoj]

You might not want to try to explain racing to me, my job is professional motorsport electronics.

I thinking Overboost is starting to figure out Motorsport Electronics finally.

But I think part of what is lost with the OP is there is no pneumatic or electrical shifting going on with the standard H pattern manual shifter.

SMG conversion time if the rules allow for it. :idea:

 

[Siv1997]

I thinking Overboost is starting to figure out Motorsport Electronics finally.

But I think part of what is lost with the OP is there is no pneumatic or electrical shifting going on with the standard H pattern manual shifter.

SMG conversion time if the rules allow for it. :idea:

The M2 has a H pattern with auto throttle blip for down shift I think.

Sent from my CLT-L09 using E46Fanatics mobile app

 

[TobyB]

LOL, that's not a flat shift that's a speed shift. Flat shift is an ignition cut for a defined amount of time with WOT allowing the next gear to be engaged. We use a strain gauge on the shift lever and a gear voltage potentiometer to accept the gear position before allowing the ignition to be phased back in. We also provide throttle blip downshifts as well, it's all in the programming.

You might not want to try to explain racing to me, my job is professional motorsport electronics.

LOL everyone's an expert, aren't they?

I won't try to explain anything to you if you chill out a bit.

I just run a small race team, nothing big...

t

 

[Overboost]

LOL everyone's an expert, aren't they?

I won't try to explain anything to you if you chill out a bit.

I just run a small race team, nothing big...

t

Sorry, don't mean to come across hostile but if you don't know the difference between speed shift and flat shift then...

What you are doing is a classic recipe for the "money shift". BTW, smooth is fast, just saying...

 

[TobyB]

Well, around here we call the thing you put on the back of your pickup to make it into a minivan a "canopy",
so it very well could be a regional thing, or an age thing... (because when I learned how to do this riding with
my hooligan older neighbor, there was no rev limiter, just valve float...) or just me getting my terms confused.
Oh, I suppose I could blame that on age, too...

Yeah, I'm not saying that it's GOOD, just that when we looked at speed traces of my car on the long PIR front straight,
against 2 other cars, all 3 PRO3 cars, equal engines, my car had noticeable drops at each gear change.
One car had slight dips, and the third, you couldn't really tell from the trace where he'd shifted.
His answer- "You don't lift to shift these cars." So I went out to duplicate his trace, and sure enough,
foot flat, I picked up about 4 mph, dropped .6 sec, and critically, could just stay in the draft of a
car with a 'slightly more stock' engine.

You won't be surprised to hear that transmissions in this class don't last all that long.

Personally, I only do it when it really matters- if I'm really after someone, or
really trying to stay ahead. And yeah, even a bit of a lift is a lot less hard on
the equipment for a minor loss in drive...

t
bekuz racekar

 

[Overboost]

Well, around here we call the thing you put on the back of your pickup to make it into a minivan a "canopy",
so it very well could be a regional thing, or an age thing... (because when I learned how to do this riding with
my hooligan older neighbor, there was no rev limiter, just valve float...) or just me getting my terms confused.
Oh, I suppose I could blame that on age, too...

Yeah, I'm not saying that it's GOOD, just that when we looked at speed traces of my car on the long PIR front straight,
against 2 other cars, all 3 PRO3 cars, equal engines, my car had noticeable drops at each gear change.
One car had slight dips, and the third, you couldn't really tell from the trace where he'd shifted.
His answer- "You don't lift to shift these cars." So I went out to duplicate his trace, and sure enough,
foot flat, I picked up about 4 mph, dropped .6 sec, and critically, could just stay in the draft of a
car with a 'slightly more stock' engine.

You won't be surprised to hear that transmissions in this class don't last all that long.

Personally, I only do it when it really matters- if I'm really after someone, or
really trying to stay ahead. And yeah, even a bit of a lift is a lot less hard on
the equipment for a minor loss in drive...

t
bekuz racekar

Well that makes sense but remember you still have to clutch the car to gain the next gear then that ends the flat shift, period. I have run PIR many times, my last run there was last year clinching the Trans-Am West Coast Championship and I know that chicane well. My professional drivers will make their gear shifts at 300ms using a H pattern box and that is fast. That 300ms is basically the clutch in and out time so remaining on the throttle during that time is pointless. The RPM of the next gear is going to be a constant gear drop RPM value, regardless of throttle position. Save your clutch and syncros in the gearbox and just be smooth and deliberate on your shifts. The last H pattern gearboxes I used were the Porsche 996 Cup cars back in 2005. We use X-Trac sequential boxes in our Trans-Am and IMSA LMP3 cars now and sequential dog type gearboxes with Megaline air shift systems in the Porsche Cup Cars and IMSA LMP3 cars and those upshifts take less than 80ms. You could try to use a SMG box on your BMW efforts that is essentially hydraulically actuated, fully automated H pattern box.

Here's a quick video of our Trans-Am team.

https://youtu.be/h93IbUYwWt0

 

[TobyB]

remaining on the throttle during that time is pointless.

It's not, quite. If you keep the engine on the limit (in our case, about 6800 for most of us)
the 'dump' into the next gear transfers most of that energy into forward momentum.
And in a class that requires a full mass crank and flywheel, there's some energy there.

I would have said 'aww, that's so minimal, it can't matter'
except that we also use data.
And when I compared traces shifting deliberately and mechanically sensitively
to ones that were increasingly more aggressive, it did in fact matter. Keeping the revs at redline
and dumping that energy into the driveline at the next shift made a small, but noticeable difference.
And those differences added up to a competitve advantage.

Especially WITHOUT that f^%$ing chicane...

I'll go dig up the data when I get home.

t

 

[jfoj]

I was at VIR the day the Burton video was shot. Lawrence Loshak had the pedal down and shredded the circuit that day! Lots of good competition and hard racing to include awesome Vintage Trans Am Racing (60's and 70's T/A car). Was even impressed with the Corvairs as well.

I guess with the E46 in a basically stock configuration, the car may benefit from keeping the revs up while shifting since there is not much extra power on tap at the upper RPM range.

But the thread is about a 2 Step box which is primarily for drag racing and not road racing from my experience.

 

[Overboost]

Hoping to see some valid data showing the time variance on these shift gains like my graph shows. The Spec E46 class is indeed a momentum class much like Spec Miata but in my world the "momentum" is carrying more speed through corners, not abusing the clutch and gearbox. Not to mention upsetting the chassis in these mid corner shifts he supposedly shows as gains. :dunno: