patsmx5

iTrader: (16)

I setup flat **** to do a fuel cut. It doesn't hurt the engine at all. Also I have it setup to roll the timing back in when shifting to 2nd, this helps with traction and wheel hop. Actually improving reliability.

stefanst

iTrader: (1)

Here's a log of the best spoolI'm getting. Starting around 5krpm nad rolling on the throttle very carefully:


Took 325ms to spool. That's running the WG with no EBC. It's still rather noticeable.
I understand that my AE goes pig-rich for a little while there and that this influences spool. I'm having a devil of a time getting it dialed in properly.

stefanst

iTrader: (1)

Flat shift does sound interesting and I guess I'll set it up. Scared what it'll do to my turbo though...

patsmx5

iTrader: (16)

A fuel cut won't hurt the turbo. A spark cut will be pure hell on the turbo. Use a fuel cut, it works great, no reason not to.

This is my car with flat shift with a fuel cut only. Listen to the engine during the shifts. It just goes off and the RPMs fall fast, and right back on when the clutch is out. No popping or hesitation, just works.

stefanst

iTrader: (1)

I'll definitely try the flatshift then. Sounds fun!

DNMakinson

iTrader: (3)

<p>Pat, do you use timing retard with that, or simply fuel cut?</p>

patsmx5

iTrader: (16)

I use a timing retard in 1st to prevent wheel spin (why it's lazy in 1st in vid) and a bit more in 2nd to get it to hook better in 2nd. The timing retard is for traction though, not for limiting power during a flat shift, only after the shift or after launching.

18psi

iTrader: (76)

I'm not so sure your cars will like flat-shift repeatedly for a significant amount of time.
I only use rarely and at the drag strip.

patsmx5

iTrader: (16)

I think it's better than no flat shift for my setup regarding the drivetrain happiness.

With MS3 PRO, you can have it ramp the timing back in to reduce torque during shift.

Also it prevents me from wheel hopping in 2nd.

Video without flat shift. Spins in 1st, wheel hops in 2nd, chirps 3rd. Pretty sure flat shift was nicer to the drivetrain than this.

DNMakinson

iTrader: (3)

<p></p><p>I hear you. I</p><p>However, it is an interesting temptation. Admittedly I am generally a gentle driver regarding engine, clutch, and transmission; flooring it only between shifts, not slamming things. One of my goals is to not break things.</p><p>Seems to me one can set it up and, if shifting normally (let off gas while dis-engaging clutch) then it does nothing. But, hold the accelerator down and it comes into play.</p><p>So, drive normally most all the time, use flat shift when you want that extra 1/2 second gone in a 0-80 mph. I likely would not need the retard with the low power, and decent tires I have.</p><p>Or is this another addicting / life-shortening thing?</p>

patsmx5

iTrader: (16)

Flat shift only works when you're shifting at redline. You have to tell it what RPM to drop to. I rev to 8-8.5K, so I tell it to drop RPMs to 6K. If I tried to shift at 5K using flatshift, it would jump up to 6K when I push the clutch in.

If you can shift, and engage the clutch completely before giving it power, great, that's good mechanical empathy letting it get in gear before feeding it any power is for sure the easiest on the drivetrain. Good practice to make everything stay together. Oh yeah, guess what flat shift does? Same thing! Except it never messes up, it does the same thing every time.

This is essentially setting the engine torque to zero during the shift. Torque management. OEM's do this all the time to make the drivetrain last longer. They typically reduce torque during the shift, and then roll it back in after the gear change is done. My Outback and C63 both have this.

Wheel hop and grabbing gears is much harder on the drivetrain than flat shift. So if you do either of those, flat shift will be better for the drivetrain.

18psi

iTrader: (76)

You tell it when to arm/engage, and when to cut. This can be as low as 3k or whatever, not just redline.



I disagree on the easier part, at least on turbo cars: you're holding boost where you normally wouldn't, and effectively shock-loading the trans with much more torque than it otherwise would have.
We talked about it a bit in my drag strip thread: https://www.miataturbo.net/suspensio...g-strip-83764/
There is no way it is putting less stress on the drivetrain, it's just doing it in a more effective way (that part I agree with you on completely). On the MSM the difference between regular fast shift vs FFS was a couple chirps into 2nd vs completely getting loose/blowing off the tires. That's what torque does, and there's clearly more of it going into the drivetrain with FFS. The timing retard is a nifty feature, but it's timed, so you can only pretty much use it when launching, not a road track and higher gears.

I use it at the track on all my cars, and when I really want to punish someone on the street (lol), but I just can't see someone doing this repeatedly at the track on a turbo car for a session without hurting something. What we do on the street are super short bursts, it doesn't even compare to the track.

On my WRX after doing about 4 drag strip runs back to back with this enabled the transmission heated up like crazy and was notchy. Let it cool off a few hours and it was fine. I'd think the miata would be same, but someone try it and report back

The difference in acceleration with effectively implemented FFS is pretty awesome though.

patsmx5

iTrader: (16)

If not using flat shift ever results in wheel hop, or chirping the tires during a gear change, or spinning the wheels after a gear change, then flat shift can help with this. If you never wheel hop, or spin the tires after a gear change then it won't help you regarding mechanical empathy.

If you drive with extreme mechanical empathy, then you're doing what flat shift would do (no torque during gear change) yourself, except that you do it slower than flat shift would.

Anyone that doubts this is true should set it up and try it out for yourself. Or watch the two videos I posted here. Both vids are same boost, same concrete surface, both 100*F Houston days. About 2 days apart I think.

18psi

iTrader: (76)

I've tried it multiple times in my cars.
It's a "lesser of two evils" type of deal.
With one you get shock loading from the shift, with the other you get torque loading from the boost you just held through the shift.

I can plot out in VD the torque spike that I'm talking about.

stefanst

iTrader: (1)

Thinking about this some more, it appears that fuel cut, while it would work very well on a supercharged car, will have limited use on a turbo car. SC cars need rpm to build boost, so all you need is the right rev-range. Turbos need hot exhaust gases to build boost. Those won't be present during fuel-cut. Granted, not lifting the throttle will cause some more air to go through the exhaust manifold and into the turbo, so it may not slow down quite as much as with lifting, but I can't see it building boost much faster. Will try at my next drag-strip visit though and report back.

Leafy

iTrader: (1)

It's still a lot of gas moving and you won't be blowing off the air in the intake or losing much turbine shaft speed. There's still plenty of energy in the air with fuel cut, I know my car builds 2 to 5 psi on the fuel cut launch control depending on what rpm I have it set to.

patsmx5

iTrader: (16)

You said you were scared of what it would do to your turbo. A fuel cut won't hurt the turbo, and it will make your car faster vs not using flat shift. It for sure has a use in making your car faster as discussed. You 100% should try it out, you got that part right! It's fun.

DNMakinson

iTrader: (3)

Set it up this morning:
1. Hard to discipline myself not to lift throttle.
2. Stock flywheel will not let engine get down to 5k before shift completes.
3. At clutch engagement, RPM goes from about 5300 to 4300 on a 1-2 shift from 7k.
4. Does not seem harsh.
5. MAP held to 120kPa
6. As fuel cut only, spark retard does nothing.
7. EAE squirts extra fuel on engagement just like it should.
8. I think I'll leave it and use it occasionally.

patsmx5

iTrader: (16)

Set it to pull a bunch of timing too during the fuel cut. It's not needed in theory, but when it shuts the fuel off, the timing retard it prevents the motor from ever hitting on a cylinder that still had a little fuel in it (which would be lean and bad) and does make the revs drop faster on my setup.

I too have a stock flywheel, but on mine the revs drop much quicker since the SC pulls about 100 HP from the crank when at redline.

Glad it doesn't seem harsh! Told ya! What RPM do you have it set to drop to?

DNMakinson

iTrader: (3)

Set to limit at 5000 rpm.
And
9. Don't get that great BOV woosh
10. Seems to save about 1/4 second