There has been a lot if discussion on throttle lag and I am trying to understand it.

• Is this only an issue on the 7AT?
• Do you think it is a throttle issue, or is it the 7AT not being responsive?

Thanks!

 

Not an expert, but usually what people deem to be throttle lag is really just the car driving the way it was programmed to drive for emissions and gas reasons. If you leave your transmission in regular drive mode, it takes time to move between gears (always stays as low in the revs as possible) and will always prioritize gas savings over performance, which is why as soon as you need a bit of power, you have to wait a second for the transmission to shift down 1-2 gears and then put the power down.

If you throw it in sport mode, it gets a little better because now it is finding a middle ground where, it will tend to stay calm if you drive calm, but once you start driving aggressively, the computer automatically keeps the transmission 1-2 gears lower than would be optimal for gas/emissions. If you slam on the gas pedal and rev it to 5K, the transmission will stay in that gear for 3-4 seconds waiting for you to just slam the gas pedal down again and push you forward.

Then, if you want total control, the sequential mode of the car gives you that. You can choose what revs you want to be at in what gear in whatever speed you want. That is why people deem manual transmissions to be more responsive, simply because you can choose to keep it at a gear/rev range that is more responsive than 1.5K at whatever speed you are going. I'd say that if you go on the highway, throw the car into manual mode and your still seeing serious throttle lag, you can probably take a few steps to alleviate that: i.e. making sure you have fresh filters, airflow sensor fully operational, cleaning throttle bodies, etc, etc... However, in the end of the day, there is a limitation to the responsiveness of drive-by-wire vehicles. For the time being, drive-by-wire will almost always have at least a tiny bit more throttle delay when compared to drive-by-cable (not that the G37 6MT has that).

EDIT: forgot to note, there is a more aggressive option that people say helps alleviate throttle lag if performance is 100% all you want from your car, certain tunes will help with the lag, not exactly sure by what mechanism they do that, but I do know they exist, and I know some people stand by them.

 

One consideration is programming, in that we have an electronically controlled throttle. There are products (Sprint Booster) which front-load the pedal signal, making you think the throttle is more responsive because the pedal travel is reduced. It's fun, but all in your head. Literally, all in your head.

What's more about physics than perception is when the drive train is more rigid to the car via added bracing, and bushings with less damping behavior. These things translate into an actual improvement in throttle response because the energy expended isn't being damped or wasted on engine lift. (Says the not-an-engineer.) A good analogy would be the difference between jumping off of sand or jumping off of pavement. The first is less abrupt and softer on the landing, whereas the second happens quickly and is probably bad for your knees. Either way, you jump just as high.

 

Have you experienced throttle lag in your 6 MT?
If so, under what conditions?

 

In reading your post, would you say it is more of a transmission issue than throttle / drive by wire?

 

Nope. Car responds to a throttle blip instantly.

Granted, poly bushings everywhere, and other stuff... like short rear gears.

 

That is a really interesting point, I have never thought about it that way. Though, in this example, it would seem that the parts that are doing the "jumping" would take a little more ware over time, correct? I mean, if less vibrational and rotational energy from the engine/trans is lost in the springiness of bushings and other dampening parts in the engine bay/on the drive train, then that energy has to go somewhere, so I'd think you would end up with slightly more ware over time. I don't know if its enough energy to make any meaningful/vehicle-life changing differences. Or maybe it just ends up in your seat?

I guess what I am trying to say is that it really isn't an "issue", per se. If you feel that your throttle lag is bad to the extent that you enjoy driving less on a daily basis, then your vehicle probably has an issue. My signature has my vehicle, and of course I have a lot of throttle lag (or I guess "transmission gear change lag") when driving normally in regular drive mode--this is to save me gas, better emissions, and less vehicle ware (lower RPMs). But when I want to do a pull and throw it in sequential manual, as soon as I step on my pedal (perhaps a sub 150ms lag, because I don't notice it) I get power. You just have to be in the right gear. Driving higher in the gears just takes longer to get up in the revs when you're on the lower end (going from 1.5K RPM in 7th gear trying to get to 6K RPM takes way longer than being in 1st gear at 1.5K RPM and hitting red-line almost immediately; this gives a facade of throttle response).

To answer your question more directly, I would say yes: generally speaking, this behavior is due to the way that the computer always tries to save you gas and keeps you in as high of a gear as efficiently possible (when in regular drive mode), and I guess by extension, the way higher transmission gears are designed to basically be the gas saving/efficient gears. They aren't really made for hard acceleration, they are made to handle very high speeds (like on the highway). Additionally, yes the drive by wire does inherently have lag, so a small portion of this behavior is also likely a result of the drive-by-wire. But compared to the time it takes for a transmission to drop a gear to be able to accelerate the way you want it to, its an almost negligible amount of time.

Just want to reiterate one more time, I am by no means an expert, this is just my 2 cents on the situation, and I could be totally wrong, perhaps there really is a higher amount of throttle lag on these vehicles than I am suggesting, I am just saying that I personally do not notice much of it, and it seems like throttle lag is often times mixed up with the time it takes to drop a gear when the transmission is one gear too high to actually give you any reasonable amount of acceleration.

EDIT: Also let me make a note regarding my first post, when I said that people deem MTs to be more responsive due to the fact that you can choose the RPM/gear you want to stay in at all times, I think there is a little more that goes into that, i.e. much like drive-by-wire vs. drive-by-cable, the speed of shifting in a manual car is almost entirely a mechanically dependent thing--based on how quickly you can shift the car. I think that definitely plays a role in both how we perceive "responsiveness" as well as how enjoyable rowing through gears can be.

 

I suspect NVH is as harsh on the car as the driver. But a general rule of thumb is the more NVH you introduce to your car, the more performance you can wring out of it.

 

Yeah that makes sense. And then the more performance you do wring out, the more inevitable ware you end up with. But yeah, I guess it wouldn't necessarily be inherently worse for your vehicle, unless you are pushing it to that level of performance anyway.

 

I can add my $.02, as I own an untuned 7AT, have driven a 6MT and a tuned 7AT. The untuned 7AT definitely gives the illusion of throttle lag, even in manual shift mode on occasion, although it is much better in manual. In D, the car is almost undriveable in my opinion because of how disconnected the pedal feels compared to what the car actually does. I rarely drive the car not in DS or manual mode unless my wife is with me (she hates the rev matching on downshifts). I am assuming this is done for fuel economy purposes, but it makes the car feel sluggish, almost like a car that requires a significant amount of steering input to move slightly left or right - the car feels mushy. The tuned 7AT I have driven reduced this feeling significantly, almost to the point where the car felt more responsive like a 6MT. I would say the "lag" felt was reduced 90% or so. The 6MT I've driven is perfect with response, so I am inclined to believe this is more a transmission issue than actual throttle response.

I will say that I notice the "lag" a good amount more if you are making any type of turn with the car, so I wonder if the car pulls based on the yaw sensor even if you aren't breaking traction. It'd be interesting to see how disabling that affects the perceived lag on an untuned 7AT. Either way, a tune seems to fix this issue.

 

You are definitely more qualified to answer this question than I am lol. I actually don't mind the regular drive mode because the vast majority of my miles are highway miles, so I am going the same speed for like 20 miles there and back. But yes, at city speeds, the normal mode seems to have no idea what to do with itself. Not sure if this is an issue with my trans, but I find that at the lower speeds the computer just can't decide between 2nd and 3rd (or perhaps its 3rd and 4th) gear and will occasionally flip between them if I coast for more than a few seconds or if I break a tad. Also, in what ways did you get your trans tuned? Do you mean like a ECU flash type of tune or like physical hardware changes? Interested to hear about this one. And how much did it cost you, if you don't mind me asking?

And regarding that last part, I believe that is also a "feature" of the automatic transmission (drove an AT 2012 Camry before this car, same exact deal with both the "throttle lag" as well as reducing input in turns). I'm am pretty sure the computer limits throttle input heavily in turns in regular driving mode and in sport mode (I think), and this is a preventative measure to reduce the risk of breaking traction, i.e. curbing the problem before it becomes one. Obviously, as with the gas saving transmission programming, this is not that hot with people who are really only interested in performance and full control over their vehicle. Like I said though, pretty sure if you throw it in manual the car wont fight you on this one either.

I am actually interested in finding out just how much actual "throttle lag" there is in each driving mode and park/neutral (for my AT). Might try to come up with a kinda accurate test to actually check this that wont require me to buy cameras and 3D print mounts and stuff. If I do, I'll be sure to either post it here or make a new post for it.

 

The tuned 7AT I was referring to was a friends G37 sedan that has been tuned by AdminTuning (full ARK catback, Motordyne ART pipes, 3" admin intakes, ported upper and lower intake, and I forget what size but upgraded injectors. I believe it put down about 335ish to the wheels). I think he spent around $1000 on the tune and dyno session, including the ecutek dongle, but don't quote me on that. Either way, the car felt way more responsive to throttle, but that also could be all of the other mods it has contributing to that. This was also under light to mid-throttle, not full out WOT, because I really wanted to see what the difference was in how it behaved for average city driving. WOT that thing was quite a bit quicker than my car (for now lol).

 

I don't know about the G37 stock tuning but on other makes it's been found where the OEM had to build in throttle lag to pass emissions. Gas right off idle apparently is where you can have heavy emissions, so it may be detuned to meet them. Maybe the 6 speed didn't suffer from this, EPA testing is different, or just the lack of a torque converter makes the difference.
The ecu aftermarket tune, which doesn't particularily have to meet emissions standards, can take this out.

It could also be that they wanted the G's to be more 'luxury' than the 370Zs? Feel not as sporty or unrefined? Anyone driven an auto Z to compare?
I find the lag not how I would like it. I've thought of just getting a tune to get rid of it.

 

Damn 335 at the wheels is around 385 on the crank for these cars if I am not mistaken. Thats some really good gains... With some weight loss here and there, lighter rotors and wheels, that car could probably do 0-60 in the mid 4s. This should be my goal for next Summer. Hopefully by the end of the year I'll be running some sways, lighter set of coilovers, and a nicer exhaust, but we'll see lol.

The first theory is definitely interesting, and I believe this is true for most cars on the market today. Tried doing further research to see if others have talked about this issue on the Gs but haven't seen anything specific. Would you happen to have anywhere you read this from that you could link? In terms of the 370Z vs G37, I tried finding exact model numbers and couldn't, but I believe the consensus is that the trans used in both cars are the same. So if there is a difference, it would be a function of either the weight difference between the G37 and 370Z (7AT Sedan is 600lbs heavier than the 370Z... thats some serious weight difference) or perhaps some more aggressive tuning on the 370Z transmissions. If the latter is true, then it would be possible to simply flash the TCM to a more aggressive setting. But I would also like to hear from someone who has driven both cars as well.

Lastly, I believe I have figured out why everyone here seems to have entirely separate frames of reference on different vehicles, and it has to do with your model year. I thought I was going crazy thinking that I didn't have that bad of throttle lag since everyone here seemed to feel differently. However, I did some digging and found this thread:

https://www.myg37.com/forums/engine-drivetrain-and-forced-induction/215807-g37-7speed-transmission-reprogram-1.html

It is an insanely long (2500+ posts deep) discussion about the 7AT's various software upgrades over the years. If you have a 2011 or prior model year, there are 3 separate updates you can get for your transmission, as per some of the TSBs listed in the linked thread. From what I've read in the thread, the first update was huge, I think that one is TSB ITB12-027d, and apparently this one made night and day changes to the throttle response and auto transmission shifting. The second update I've heard was less night-and-day, but also refined the performance. The last update is for all G37s (including the last model year, 2013), but I've heard mixed reviews about this one. It apparently refines the transmissions usual operation, but DS mode becomes less aggressive (I've also read this is just because the ECM/TCM need time to relearn your driving style). In any case, this seems to be why I didn't register this throttle lag as a serious issue, mostly because its very minimal in my vehicle because I purchased it with the updates. If you have a 2011 or prior model, I highly recommend you take it to a dealership and get this update flashed. From what I've read all it should cost you is $125 and it fixes a lot of the issues with the transmission.

 

Yeed, that is some good information. Funny, I was just thinking this morning "I wonder if the tranny ecu updates had an effect on the throttle lag?". Looks like you found some.

They do have the same 7 speed tranny in the Z cars I've read, basically the same everything just a few HP down (from exhaust I believe), but for our purposes here the same. Yes, weight, bushings as rochester mentioned (stiffness) and rear end ratios can play a part.

My experience was back in my autox days- we are in town with a big Honda plant, north east part of town you can't throw a dead cat without hitting someone with Honda. A lot of their engineers used to come out to autox and we'd of course always talk, go for a beer after and talk cars even more. The drivetrain guys were talking about the throttle issue and how hard they worked to get around it and make it work with emissions (Hondas, at least at that time, had great throttle response off idle). The easy way was just to program in some lag as they said some makers do. Of course that was many years ago, so things have moved on, but it would be about the period where the G's where being designed.

*I'm not sure my tranny has the updates, 2009, so I'm going to the Nissan dealer to check. The local Infiniti dealers can't seem to be bothered to call me back...
I'll report back.

I've also been working on some simpler things on the throttle lag. A good baseline tuneup; all oils, new plugs, injector cleaner, throttle body cleaning and putting smooth silicone intake tubes along with AFE dry air filters did a good job in improvements. I did them all at once, so I don't know who did the main work, I'd suspect the throttle body cleaning, but all together it's solid. The car feels much 'brighter' if that makes sense- probably up 5-10 hp too and a touch of nice intake noise. I'm happy so far.