I have a 2008 G35 with the VQ35HR engine. My wife has a 2003 G35 with the VQ35DE engine. Mine has more HP and torque yet hers has more "jump" to it from a stop. Her gas pedal feels much more sensitive. Mine requires more pressure to accelerate from a stand still. Could this be a tune-up issue or dirty throttle body issue on mine? Or are these engines just different in how they perform?

 

The ECU in A/T vehicles will learn their drivers behaviors and adjust accordingly, so it's possible that the first gen has gotten used to your wife's driving style. Either way, it'd probably be worth cleaning the TB and/or doing a throttle re-lean procedure (which you can find with a quick search) and see if it changes.

 

Nothing will change the pedal feel since it's all throttle by wire. That is determined by the return spring on the pedal itself.

If you're comparing an AWD vs a RWD you need to remember that the AWD has a lot more components to turn and that extra rotating weight takes energy to turn so it will feel more sluggish. 1st gear ratio for both vehicles is the same, stall torque ratio is the same, final drive is the same. The HR has more power and more of it is available at a lower rpm so it SHOULD pull a little harder off the line as long as vehicle weight, traction, are the same.

 

I've heard the DE actually has more torque down low in the 2500-3500rpm area so that's why it probably has more jump off the line, although it is strange you need to push your pedal to get it to go.

I have an '07 G35x (basically same car) and these are notorious for being very aggressive/jumpy off the line.

 

EPA efforts were more stringent in 08 than they were in 03. Basically meaning that the gas pedal is much less linear in 08. Car companies do this to "comply" with epa requirements (most likely greasing palms at the same time)

What I'm getting at is that different cars (depending on many factors) have different throttle position values. 50% throttle may not be the same on the 08 as the 03. You may not get 50% fuel delivery until a 75% throttle position on the 08, whereas an 03 may get 50% fuel delivery at about 62% throttle. That's one way they skew mpg ratings.

Also why we can get ok mpg as long as we don't floor it *too* often. All the power is at the end of the throttle.

 

Both are RWD. I checked the specs and I have more HP and slightly more torque at 4800 RPM which is why I'm a little confused as to the difference in feel from a stand still.

 

4800 rpm ? Compare the torque curves from idle up to 4000 rpm. Even 4000 rpm is pretty high unless you're really aggressive with the throttle from a stop.

Compare real-world feel with yours in DS mode vs hers in standard drive mode. If yours feels better then, it's simply a (factory) tuning difference. As others have mentioned, many of these things are mandated by governments, usually in relation to fuel economy. It's why US-based cars spec 5w-20 oil but in other countries they spec a different oil (engines can get miniscule improvements in MPG with different oil weights and every bit counts).

 

Torque at 4800 is what the specs say. That is why I was surprised at how different the cars feel. I just feel a noticeable difference in pedal feel and response when I drive the 2003. The 2003 just feels significantly quicker.

 

You both obviously need to go to the nearest drag strip and settle this!!! and report back,, also loser has to.....? lol

 

I'm in the exact opposite boat as you guys, I always thought the HR equipped vehicles felt significantly quicker than the DE, especially the 0-60 range. The DE feels a lot noisier for sure though, the motor is a lot harsher overall and that might be adding to some kind of percieved power.

 

 

I honestly don't see how or why that would be a thing either. The ECU takes orders and commands the rest of the car. Not even sure what the heck "learns how you drive" means. So, what, it keeps a record of how you drive so it can later operate the car by itself in your best interest? Haha

Also, OP, have you ever tried to go full throttle from a stop on both cars? That's really the only way you can compare power. Also, what is the differential gearing in the HR? And what is the tire size difference between the two cars?

 

The 2003 even sounds better. It has more of a growl to it than the 2008.

 

I'm still not convinced the ECU-TCM learned behavior has anything to do with driver input. We all know the ECU makes trim calculations based on sensor data to build LTFT and the TCM does the same sort of learning using the pressure sensors to control line output pressure to have short locking times while minimizing lock-up shock but I have never actually seen any verifiable data saying that it changes based on DRIVER BEHAVIOR. Even the new DCT's learning procedure is basically just clutch motor engagement timing, shift timing, etc and it learns how to shift itself with a balance of speed and acceptable harshness.

I think what happened was when the learning-style of ECU controlled fuel injection came about the masses didn't understand how it worked so the salesmen came up with this fancy bullshit about how it "learns your driving behavior" which also worked as a blanket excuse for why the shifting felt "different" or "wierd" to customers who complained about it during test drives, and thus the legend was born.

Not to be confused with electronically adjustable shift logic (wet/snow/offroad button on selectable control equipped vehicles.

 

Is this whole "learns your driving behavior" a real thing or is it something perpetuated by internet forums where it's been repeated enough times by enough people that it's now considered fact ? I've read the same thing about the transmissions in newer cars. I've "reset" it to what is supposed to be the factory default, meaning it should be a pre-defined logic and it feels exactly the same as what is supposedly to be "learned" behavior.