laggy/hesitant throttle response when upshifting?
 

Brand new owner here; I've only put ~150 miles on it since I took the keys. I'm noticing, at times, that the car is slow to respond when I get back on the throttle after upshifting. If and when this happens, the car will jerk into the power when it kicks in a split-second later.

Is this normal? It doesn't seem to happen as often when I am not shifting and getting on the gas in rapid succession (if I delay throttle input a split second), but that's kind of how I'm used to driving.

I'm coming from a second generation Miata with a throttle cable, but I've also spent a lot of time in a third gen Miata with throttle-by-wire, and the shifts are fairly smooth.

Thoughts?

This is built-in. The drive-by-wire throttle has built-in dead space at the very top of the throttle. This results in a perception of a laggy throttle. It's intentional to account for bad habits by drivers who should know better.

This is a correctable defect.

So what's the solution, if any? Do I just give up on getting on the gas quick and hard, post upshift?

No. It's in the ECU. That means it can be fixed to give you immediate throttle response. The solution means tuning.

The factory tune can use work anyways on stock exhaust and intake to simply run better. I'm in the process of having that done to my BRZ right now and it's resulting in noticable (if subtle) improvements in driveability, shift smoothness, top end torque and other niceties, in addition to a noticeable (and not so subtle) improvement in fuel economy.

Also, if you get better tires, that could help too, as you will simply have better grip to grab the road better when you apply power to the wheels.

Could also possibly be the Clutch Delay Valve?

http://www.ft86club.com/forums/showthread.php?t=8611

I read through the thread. It sounds like the CDV affects mostly the 1-2 shift, but I notice the hesitation/jump in higher gears/shifts.

Bummer. I'll look into tuning someday, but not any time soon. Thanks for the info.

http://www.ft86club.com/forums/showp...69&postcount=3

This has worked for me. Good luck.

I understand. This might "help":

http://www.ft86club.com/forums/showp...5&postcount=39


I agree about the NC Miata; we traded in our 2006 for the BRZ. The Miata was "normal," just another normal-shifting car like any other. But the BRZ? It'll leave you wondering, "Is there something wrong with this car, or is it ME?!" :eyebulge:

I have frequently thought that all these youngsters first learning to drive a manual transmission on the Twins ... well they're set for life, and will never have trouble again on any new car after learning on the BRZ/FR-S! ;)

It's just the clutch release height, honestly. I came from a WRX and STI, and my first time test driving a BRZ I had zero trouble shifting. It was just a high releasing clutch. That's totally fixable, though, so no worries.

This is actually a much easier car to shift than any other manual I've owned or driven.

As far as a hesitant throttle, I tried the pedal trick and it worked!

What exactly is that pedal trick supposed to do though? Is it like the other "pedal dance" that puts the car into some sort of diagnostic mode?

The WRX and STi also use drive-by-wire right?
There might not be much difference there - but if you go from an older car (say, early 2000s) to a recent car, it might be more noticeable.

Would a lightened crank pulley help a bit? It is supposed to have quicker response, right?

I agree with this. The first 5% of throttle pedal travel is not very responsive, likely due to how the DBW is programmed. It's noticeable if you're coming from a traditional cable setup where the pedal feels linear. You eventually get used to it though.

Basically, it changes the clutch ERGONOMICS (but not mechanical function) by altering the point in the clutch pedal stroke where the clutch disk contacts the flywheel, the point I call the "take-up point," and others variously call the "grab point," and "bite point," and so on. Some owners have found that the take-up point on their cars, where the clutch begins to engage, is comparatively high in the pedal stroke.

What does this mean?

First get a feel for the length of the clutch pedal stroke as you depress the pedal fully to the floor and then release it allowing it to come up fully to the top of the stroke. Get a sense of low LONG that stroke is. Now, depress the clutch pedal to the floor (engine running and car in 1st gear); then, slowly raise the clutch pedal to the point where the clutch just begins to engage; note WHERE in the pedal stroke that engagement point seems to be. I like it adjusted to a point around 1/3 to 1/2 way up in the pedal stroke. This is what affects your muscle memory; how much do you raise your left foot (most of us use our left foot on the clutch ;)) before encountering the point in the stroke where the clutch begins to engage. I try to see to it that our cars all have the engagement point occur around the same point, with the same amount of foot travel; this makes it easier to transition from one car to another.

Adjusting this clutch pedal travel will also move the pedal "ride height," or where the pedal sits stationary in relation to the brake pedal. A lot of drivers like their clutch pedal to be level with their brake pedal.

If you adjust this, it is CRITICALLY IMPORTANT to make certain of the following two points: (1) Ensure that there is approximately ½" of free play at the top of the clutch pedal stroke. It's hard to feel in my BRZ. Get an idea of how it feels BEFORE messing with the adjustment. This free play is essential to ensuring that the clutch disk is FULLY ENGAGED at the top of the stroke after you've taken your foot off the pedal. (2) Make certain that the clutch is FULLY DISENGAGED at the bottom of the pedal stroke. If the clutch is still dragging on the flywheel and putting some drive through to the gearbox via the input shaft … this will wreak havoc with the synchromesh in your gearbox.

So, if you go too far with this pedal adjustment, your clutch life may suffer, or your gearbox life may suffer. Either way, you'll be unhappy paying for the repairs down the road.

When adjusted properly (see above), this pedal height adjustment does NOTHING to change the mechanical operation of the clutch itself. It does not change the throwout bearing, the pressure plate function, the clutch disk, or the flywheel function. The clutch disk seems to bite fairly quickly on this car, mine anyway, and perhaps this contributes to the awkwardness in executing smooth shifts. But, changing the clutch pedal ride height (and engagement point within the stroke) has NO EFFECT on the mechanical operation of the components when keeping it in spec. How could it?

One might think that production variances would be small and that there would be no need to adjust this on a new car. I have not found this to be true on the new cars we have purchased over the decades. It's not unusual to find that I need to adjust our new car's clutch pedal ride height to get what I prefer. Just remember, if you do this, to keep it within spec: ½" free play at the top and fully disengaged at the bottom. There's usually some room to play with within those limits, and I can find an engagement point that falls where I prefer it and which closely matches my other cars while keeping it in spec.

Ergonomics are important. I dislike a clutch that engages high in the pedal stroke; I find it awkward to drive. Your mileage may vary, of course.





No, the "pedal dance" is entirely unrelated to what we're concerned with above. The pedal dance simply defeats some of the electronic nannies for stability control, etc. It does not alter the nature of the function of the components, it just TURNS THEM OFF. It turns off EBD, which still leaves me scratching my head about the advisability of doing it. There does not appear to be a clear consensus of opinion about doing the pedal dance; some say it solves their problems, while others say it creates worse problems. This is largely competition oriented and would not apply to most street driving for most drivers. But, do read about it just so you're better informed and know what is possible, as the day may come when it may offer a possible solution to some difficulty you're experiencing.

I hope this has made sense to you and others, and has been helpful. :)

Very informative post Porsche, but I was actually asking about this when I said "pedal trick."

Anyone know what that is all about?

I'm assuming by Pedal trick you meant to make the throttle more responsive and not the clutch adjustment, here's my best guess:

The throttle is supposed to naturally become more responsive as the ECU learns the full range of motion of the throttle pedal, but by default includes a dead zone to be safe after an ECU reset. The pedal trick fast tracks that by leaving the car on but not running(and therefore safer to repeatedly push the throttle) but giving it plenty of examples of the range of motion to adjust the actuation point/dead zone to the full range.

Again, this is purely a guess.

I do not understand that post you referenced. Does it, too, put "the car into some sort of diagnostic mode" as you wrote?

And whether it does or not, do you recall what problem they were addressing there?

This is interesting. I'd like to learn more about this so-called "learning." I've read about this, but everything has been so vague that I don't know what to think.

Is this learning an on-going thing, constantly adapting to changing conditions? Or, is it a one-time thing following an ECU reset? Is it set in stone until the next ECU reset, which for most of us might never occur?

I'd be grateful to anyone who could explain this to us, preferably with reliable URLs and references. I'd like to learn more.

Thanks.

The new drive by wire throttle pedals have a dead spot at initial depressing when the ecu had been disconnected with limited mileage on it. The computer learns the range of motion as you drive the car. As others have stated. In order to eliminate this dead zone to speed up the process of the computer learning the pedal range you can try the trick I posted earlier. It seemed to work for as I was experiencing the same thing as op is now. Nothing special about it, just that ecu needs to relearn after being disconnected or brand new with limited mileage. If your talking about the clutch engagement than that's something different and there are things you can do for that as well. But I wouldn't recommend it as it's not changing the leverage motion of the clutch and simply shortening the amount of travel, that if done incorrectly could lead to improper clutch actuation and premature clutch replacement. Anyways I hope this helps.

Just try the throttle pedal trick & profit ;-). You're not hurting anything.

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LOL! Fair enough, I'm game. But, can you EXPLAIN it to me please, Sir? Note the questions above. ;)

Well, of course not; it never occurred to me that it might. :)

Now, tell us EXACTLY what will it do? What will it CHANGE? Why do you imagine that it will change anything on my BRZ? How and why will it do it?

If you were to go outside right this minute and perform this magic on YOUR CAR, will your car run better than it did the last time you drove it?

How?

Why?

Help us! Inquiring minds wish to know! ;)

When the ecu has been reset or is new, it doesn't know the full input range of the throttle position sensor, but has a general idea. This means it needs to learn the full range as the throttle is used. That is, over time, it learns what that particular sensor's range is.

Basic control loop.

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Not applicable to my "old" 2013 BRZ, or to your car either, in other words.

VERY basic.

So, alas, my wonderful BRZ will not be even better still.

Okay then...

But you owe me, now, for getting my hopes up. ;)

Just try it. And it is applicable to my brz, b/c I was getting road tuned on Monday.

Reset your ecu & try the pedal trick.

You're giving up too quickly.

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What is will do is help make sure the ECU knows the full range of the Throttle pedal. This is because it's a drive by wire(electronic) pedal, and there's clearly some variance in the signals they send.

If you have a dead zone at the start of your throttle pedal, where pressing doesn't produce any throttle, I'd try it. If your pedal has adjusted to the point where it responds to all input within the inch of travel, then it's likely already adjusted itself on its own.

Do you get the feeling we're talking in circles? LOL! :)

Why should I reset my ECU? What will I gain? How? And why?

My car works perfectly. I never said it didn't.

Giving up on what? My car works perfectly.

Resetting my ECU would mean limping around for some undetermined time before my car re-learned (what it already knows) and returns back to exactly where it is right now.

Get back. Get back, I say!

Don't touch my car, I tell you! :eyebulge:

LOL!

Lots of great information here.

I adjusted the clutch pedal a few days ago, and while it has helped tremendously with shifts, it's not the culprit.

I really don't feel it's a throttle dead zone either; the car just get bogged down if I am hard/fast with the throttle. Seems like it's running on three cylinders for a split second and then it jerks to life. And the sluggishness doesn't seem to match the torque curve/dip either.

If I take it easy on the throttle, and work up to full throttle just a tad slower, the sluggishness doesn't seem to show up quite as often. I'm not sure why that is.

I will probably try that pedal trick anyway, as I am all about speeding up the "learning process" of my new car.

The throttle plate in the airstream (intake manifold) is an analog device. It has physical open and closed stop positions.
It's attached to a rheostat (another analog device - Throttle Position Sensor - TPS) that transmits an analog voltage value depending on where the throttle plate is at any given time.
You can think of it as the Volume Knob (mine goes to 11). They're the same type of device.
The TPS voltage is subject to manufacturing quality variability. Each individual TPS will produce slightly different values.

The ECU is a strictly digital device that needs to combine readings from the TPS along with a bunch of other analog signals to tell how the whole system is performing.
Typically, from a cold boot (no electrons) the ECU is programmed to expect a safe range of values from the various other sensors.
If it sees something outside those values it throws codes and the binky out of the pram.

In the case of the TPS when in range, the ECU has to narrow down the actual analog voltages produced when open and closed.
Usually initial ECU values allow for higher and lower values that cannot actually be produced - the dead spots - that it learns to ignore if those values are never recieved.


Thus endeth the Digital/Analog for this evening.

Now that I have about 200 miles on the odometer, I think I've narrowed it down to poor performance at low revs. It just crawls when I try to move below ~2500 rpms, and then it jumps when I finally get there. I don't notice this in 1st, but it shows up in just about every other gear. Acceleration just sounds different and there's no pull.

Is that just the nature of the beast? Is that what everyone else gets when they try to get on the gas below ~2500? Is it a break-in thing?

People on here talk about shifting between 2-3000 rpm for "normal driving", and I don't know how they get by. I feel like I need to keep it above 3000 at all times lest I get super frustrated with the sluggish response.