Hello and welcome to my blog. For my first post, I thought I would share a little annoyance that I have been experiencing ever since I picked up my ’07 Nissan 350z. I know that Nissan’s are not the only ones experiencing this problem and I have read that the Hyundai Genesis also face a similar situation. Anyway, I hope you enjoy what I have to say and if you would like to know more about me, please take a look at the about section.
This is something that I noticed when I first got my car and I thought I would just get use to, but, it has continued to bother me ever since. What I’m talking about is how some of these new Drive-By-Wire throttles have terrible response, lag, slowness or whatever else you want to call it. In the simplest form, the throttle sees two situations: Being on the throttle and off throttle. The ‘being on’ part is not what I’m concerned about and I think this is one of the main benefits of having a drive-by-wire system (DbW), since the throttle plate can be optimized for any given RPM increasing power and fuel economy. But since the throttle butterfly is now driven through a servo rather than an old fashioned cable, this gives the ability to tune someplace that was never really looked at to heavily before. That is, when the driver gets off the throttle.
My first impression when I drove my 350z was that it took seemingly forever for the RPM to come down after I shifted. I didn’t quite understand why it took so long, it felt like the car had a hundred pound flywheel, but I knew better since I read that Nissan did a lot of work to keep the driveline mass down. I then thought it was supposed to make the car feel more luxurious by slowly transitioning from on-throttle to off-throttle, thus hiding any lash in the driveline. But after doing some very frustrating research and finding that most people (I’m sure, not performance oriented people) couldn’t even tell that this existed, I finally came to the conclusion that its for emissions reasons.
All cars, that is until now, have nice little pops of un-burnt gas exploding in the exhaust when the driver quickly transitions from on-throttle to off-throttle, particularly at high RPM. Often, this condition is mistakenly referred to as a backfire, but the real name is Afterfire. Anyway, with my car, it was tuned in such a way to prevent this from happening. I’m sure this was because these afterfires are very inefficient burns that produce a lot of by-products that make the EPA frown.
Now, the down side of all this. Because the throttle is gradually decreased when getting off throttle (we are talking about two seconds here), the time required to execute a shift is dramatically increased because the driver now has to wait a ridiculous amount of time until the RPM’s match the next gear. Under normal driving conditions, I sometimes engage the clutch half-way to slow the engine down, but that’s really putting a lot of wear tear on the clutch. Under racing conditions, the amount of time lost in shifting is just absurd. Its so bad, that if I let someone unaccustomed to this drive my car, I run the risk of having them grind the gears because the syncros in the trans cannot match such a wide RPM difference when they try to shift quickly. At the very least, they release the clutch too early making very jerky shifts.
I have a feeling that we are going to see more and more cars like this as emission requirements continue to tighten. It also makes me wonder about how much fuel we waste in trying to keep emissions clean; I may have to write about this later. Unfortunately, there’s no easy solution to this “problem”. Short of going to a full standalone ECU, at least for my car there is some piggyback systems which allow the user to tune this out, but that means dyno time to get everything sorted. There is a company by the name of Technosquare out of torrance California that offers a ECU tuning/flashing services, but I’m a little skeptical of their one-size-fits-all/pre-tuned approach and they don’t mention anything about this off-throttle issue. The price of this flash service also seems a very high for results that I found are debated in various forums…
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