Just got Phearable stage 2 tuned - rev hang is still there... :-(

[ABPDE5]

I don't want to badmouth a brand unnecessarily. They just said there's nothing further we can do, and all tunes will behave the same.

@JesterTuned any insight on this? Can the throttle overshoot that occurs after lift-off at moderate to high RPMs be addressed or are we stuck with it?

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[JesterTuned]

@JesterTuned any insight on this? Can the throttle overshoot that occurs after lift-off at moderate to high RPMs be addressed or are we stuck with it?

Well don’t shoot the messenger, but it is a combination of factors. The weight of the flywheel keeps the engine going. Plus if you don’t perfectly execute the shift you will always get a little rev up. Completely normal and harmless.

The rev hang disable just minimizes the throttle up from the engine the rest is just physics and timing from what I have seen.

 

[Fred 930]

I am very disappointed to read through this thread. The Type S "Rev Hang" (actually over-rev) flaw is the biggest single problem I've noted with the car. I've been told it's due to Honda's approach to emissions, but it's awful and not something we should, "have to get used to".

I've driven manual transmission cars my entire live. For anyone used to driving a "normal" manual transmission vehicle (my present DD is a 2023 VW GTI), it's an intolerable situation that will certainly result in abnormal clutch and drivetrain wear for cars that are driven hard. While I'll probably continue to avoid Tunes while in Warranty, I was looking forward to eventually getting this nasty problem fixed.

Mentioned above - the Over-Rev might be minimized by shifting at red line - where perhaps the engine management system is smart enough to avoid self-reving above that point. Certainly not a practical fix, but at least something to try. Honda should be ashamed for not immediately addressing this design flaw.

 

[ashmostro]

Nice to hear someone has the same aversion to this "feature" as I do.

While I agree it sucks, Honda will never address it. With manual transmissions going away, and eventually ICE as well, there's no impetus for Honda to do anything about designing a better implementation like some other manufacturers have done (cough, BMW, cough).

I wish it weren't the case, as I despise the overrevving as much as you do.

 

[JesterTuned]

I am very disappointed to read through this thread. The Type S "Rev Hang" (actually over-rev) flaw is the biggest single problem I've noted with the car. I've been told it's due to Honda's approach to emissions, but it's awful and not something we should, "have to get used to".

I've driven manual transmission cars my entire live. For anyone used to driving a "normal" manual transmission vehicle (my present DD is a 2023 VW GTI), it's an intolerable situation that will certainly result in abnormal clutch and drivetrain wear for cars that are driven hard. While I'll probably continue to avoid Tunes while in Warranty, I was looking forward to eventually getting this nasty problem fixed.

Mentioned above - the Over-Rev might be minimized by shifting at red line - where perhaps the engine management system is smart enough to avoid self-reving above that point. Certainly not a practical fix, but at least something to try. Honda should be ashamed for not immediately addressing this design flaw.

It is not a design flaw, it was done on purpose. Cars that keep momentum going when shifting actually drive smoother.

Take for example the AP1 vs AP2 s2000. The lightweight flywheel of the AP1 made the car more jerky to drive if you did not get everything perfect. The AP2 by having a heavier flywheel had better street manners but sacrificed response and performance compared to the ap1 only to be made up by the extra .2 displacement.

If it is such a problem just get a super light flywheel and it will actually drop the rpms like a rock every time you shift.

 

[ashmostro]

I'd say it would do the opposite, jester (though I understand what you're saying).
The issue being discussed isn't slow rev reduction due to excess engine momentum, but overrev due to throttle plate non-closure for emissions reasons. I know you are very knowledgeable about both so this isn't me trying to brosplain you lol. Just clarifying the phenomenon being whined about

 

[Victorofhavoc]

I'd say it would do the opposite, jester (though I understand what you're saying).
The issue being discussed isn't slow rev reduction due to excess engine momentum, but overrev due to throttle plate non-closure for emissions reasons. I know you are very knowledgeable about both so this isn't me trying to brosplain you lol. Just clarifying the phenomenon being whined about

The flywheel keeps momentum and resists the friction which would otherwise cause the rpm to fall more quickly. Even though the flywheel would accelerate faster as you clutch in, it would still decelerate much more quickly and would be acted on more quickly by the engine friction. Unless of course you're hanging onto the throttle for much longer than your clutch in point.

To be clear, you're not complaining of "Rev hang", but of over revving during acceleration. On my z Rev hang could never be truly tuned out and no matter what, rev it in neutral and it would hang for a full second before coming down. Moving from a 28lb flywheel to a 9lb flywheel made gear change dramatically faster for the rev fall, but rev hang never changed.

There's a lot of benefit in a turbo car for the ecu managing state off throttle beyond just closed. Keeping the turbo spinning and air moving is part of honda's throttle response management. I've driven older turbo cars that didn't do this throttle management and the turbo lag was brutal at times.

If you're trying to force more shock during the shift, then the lightest flywheel and a grippier clutch will accomplish that. It would also make ffs hit you like a rock instead of smoothly. In combo with your cdv delete, it will be much more immediate on the grab.

 

[ashmostro]

A lighter flywheel will, by the very same physics, be less resistive to engine acceleration, which is exactly what overrev is. That's what I meant when I said it wouldn't help/might even make the issue worse.

If there were no overrev behavior from the ECU then, yes, a lighter flywheel would get the revs down faster. But since even with a heavy flywheel we are seeing overrev, it's clear which is the more dominant force between engine friction and acceleration, on this platform.

As for it helping turbo lag, sorry but other manufacturers have proven that there are much better strategies to combat lag without introducing driveline shock or slowing down the shift time. I stand firm that this overrev implementation on this platform is purely an emissions reduction strategy and nothing more.

 

[Victorofhavoc]

A lighter flywheel will, by the very same physics, be less resistive to engine acceleration, which is exactly what overrev is. That's what I meant when I said it wouldn't help/might even make the issue worse.

If there were no overrev behavior from the ECU then, yes, a lighter flywheel would get the revs down faster. But since even with a heavy flywheel we are seeing overrev, it's clear which is the more dominant force between engine friction and acceleration, on this platform.

Yes, you are correct, it will be less resistive... Meaning the mass won't keep the engine spinning as long at as high of rpm.

If you take your foot off the throttle at the same time, the lighter flywheel will slow faster. Yes it might still rev a little more with the throttle still open, but you're not adding fuel and creating combustion even if the throttle plate is open. You're not "creating additional positive acceleration" when your foot is off the throttle and therefore the friction of the engine and air pressure from the throttle mostly closing are what create the engine braking. You can prove this by letting off the throttle quickly while in gear. You don't shoot forward for a half second, you almost immediately start slowing down. Yes there's drivetrain friction in play as well there, but we're just talking about that first moment as you let off.

I still think it's much easier to just rewire the brain to foot connection. Driver mod should always be step 1.

 

[ashmostro]

We're absolutely not talking about the same thing.

Revs are not hanging. They are shooting up artificially because the throttle plate is being told to open under no load to force a lean condition to guarantee maximum unburned fuel combustion. It is 100% accelerative.

I'll try to record what my car is doing to show you, if I have time. I really don't have any need for anyone to believe me

Anyway, moving on. It is what it is.

 

[Fred 930]

I agree with ashmostro - the ECU is clearly adding throttle during high RPM shifts, which causes an increasing over-rev engine condition - even though throttle input has been reduced during the shift period. This is exactly the opposite response one would expect from a normal car (and I've driven manual transmissions my entire life).

Typically one would expect a 500-800 (or so) RPM decrease, depending on the next gear ratio, to provide the correct RPM to mesh with the next higher gear. But the Type S, rather than dropping 500 RPM to smoothly engage the next higher gear does the opposite - it increases 1000 - 1500 RPM. If the driver doesn't wait a considerable amount of time, clutch re-engagement results in a pretty brutal shock to the clutch, drivetrain, and passengers. I also can only assume it's being done for some emission reason - it most certainly would never be programmed behavior to enhance the car's driveability!!

While Honda probably did it on purpose, I consider it a serious design flaw which upsets the driving experience and will certainly result in long term drive train wear (not to mention having to apologize to your passengers). Honda should fix this problem! It's the only serious flaw I've found in an otherwise wonderful car.

 

[snapple37]

interesting thread. This happens on my non-S too and I thought it’s because I haven’t driven manuals in a while and I was accidentally keeping my foot on the gas pedal after pressing clutch. Glad to know, although it sucks. Just need to shift slower I guess?

 

[ashmostro]

interesting thread. This happens on my non-S too and I thought it’s because I haven’t driven manuals in a while and I was accidentally keeping my foot on the gas pedal after pressing clutch. Glad to know, although it sucks. Just need to shift slower I guess?

It's either shift slower, or accept the occasional driveline shock.

Note this behavior isn't happening at moderate throttle and RPM, only when you are pushing it (which ironically is exactly when you don't want this to happen lol).

BMW uses two catalysts in their exhaust systems as part of the strategy to avoid having to add throttle between shifts - they just let the catalyst sort out the unburned fuel. It works much better and feels more like an old-school manual transmission. But it costs more in hardware, of course. you pay what you get for.

 

[Fred 930]

interesting thread. This happens on my non-S too and I thought it’s because I haven’t driven manuals in a while and I was accidentally keeping my foot on the gas pedal after pressing clutch. Glad to know, although it sucks. Just need to shift slower I guess?

I drove an A-Spec while waiting for my Type S. I recall it had the same over-rev problem. I was told the Type S would be "better". It might be (uncertain), but it's a shame owners have to put up with this behavior. I assumed the aftermarket Tuners would eventually address it, but might be more complicated if it really done for emissions reasons. Again, my 2023 MK 8 VW GTI does not have this over-rev problem.

 

[Tw1stedlog1k]

This is definitely a Honda thing, they've been doing it since DBW throttle as early as 2003 (probably earlier than that). My 2004 Accord behaved similarly and I attribute my granny-style shifting to years of Honda conditioning.

Yes, it's all Honda's fault I am the way I am!

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