Originally Posted by DNMakinson
(Post 1268409)
<p></p><p>That is mad. <img alt="big grin" src="https://www.miataturbo.net/images/smilies/biggrin.gif" style="height:16px; width:16px" title="big grin" /> is right</p><p>Question: How hard on the engine is flat-shifting, and how hard is it to set up? I have no plans, but indeed the OP may be interested.</p>
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Here's a log of the best spoolI'm getting. Starting around 5krpm nad rolling on the throttle very carefully:
https://www.miataturbo.net/attachmen...ine=1442882348 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. |
Flat shift does sound interesting and I guess I'll set it up. Scared what it'll do to my turbo though...
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Originally Posted by stefanst
(Post 1268509)
Flat shift does sound interesting and I guess I'll set it up. Scared what it'll do to my turbo though...
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. |
I'll definitely try the flatshift then. Sounds fun!
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<p>Pat, do you use timing retard with that, or simply fuel cut?</p>
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Originally Posted by DNMakinson
(Post 1268710)
<p>Pat, do you use timing retard with that, or simply fuel cut?</p>
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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. |
Originally Posted by 18psi
(Post 1268761)
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. 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. |
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Originally Posted by 18psi
(Post 1268761)
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.
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Originally Posted by DNMakinson
(Post 1268861)
<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>
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. |
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You tell it when to arm/engage, and when to cut. This can be as low as 3k or whatever, not just redline.
https://www.miataturbo.net/attachmen...ine=1442977249 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. |
Originally Posted by 18psi
(Post 1268890)
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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. 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).... 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. |
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. |
Originally Posted by patsmx5
(Post 1268523)
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. Miata Supercharged Whipple Flat Shift - YouTube |
Originally Posted by stefanst
(Post 1268962)
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.
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Originally Posted by stefanst
(Post 1268962)
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.
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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. |
Originally Posted by DNMakinson
(Post 1269997)
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. 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? |
Set to limit at 5000 rpm.
And 9. Don't get that great BOV woosh 10. Seems to save about 1/4 second |
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