GeneL

Is anyone except me frustrated by the slow throttle response of the LV8 (400 HP) engine in the 2007 Corvette with standard shift? As one dealer explained, "They all do it." At least the three 2007 Corvettes I tested do it. I could not test a Z06 or other year Corvettes with "drive by wire" throttles. The short story is that engine power lags throttle pedal position changes by about 1 second. The delay is caused by the computer software. This is what I am talking about (long story):

Test 1. With the clutch pedal depressed, engine at idle, give the throttle pedal a quick "blip." After the pedal is back to the idle position the engine speed will "blip." The delay is about one second.

Test 2. With the clutch pedal depressed, put pressure on the throttle pedal and hold the engine at 3000 RPM. Quickly let the throttle pedal return to the idle position. The engine speed will hold at 3000 RPM for about one second, and then coast down to idle speed.

Test 3. Find a deserted stretch of road. In second gear, accelerate to 3000 RPM. Let the throttle pedal return to the idle position. Wait one second. Quickly depress the clutch pedal. The engine speed will coast down to idle speed immediately without the one second hold at 3000 RPM as in Test 2.

This defect causes the following problems.

Problem 1. Engine stalls. I have owned many cars with manual transmissions, and have not had this problem. With this car, when the clutch is at the engagement point, the driver must anticipate the need for engine power by one second before further engagement of the clutch. This is tricky on uphill starts. Also, if other manual shift cars are routinely driven (no throttle delay), it is easy to forget the delay, and engage the clutch normally, resulting in engine stall. This is a safety concern. It would be easy to get hit from behind when the engine stalls at an intersection.

Problem 2. Excessive clutch wear. To avoid engine stalls, excessive clutch slip is required.

Problem 3. Slow shifts. To up-shift smoothly, the engine and clutch speeds should match before the clutch is re-engaged. Because the engine RPMs do not start to drop for one second, up-shifts are slow, especially during the dreaded 1-4 up-shift. Try test 3 again when up-shifting and you will experience how quick an up-shift could be if the delay could be eliminated.

I have a case open with Chevrolet. The second dealer I took my car to also opened a case with engineering at Chevrolet. Chevrolet claims I am the only person complaining about this. It appears that they will not move on this complaint unless others come forward. If any other C6 owners feel that this needs to be addressed, please contact Chevrolet's Customer Assistance Center (CAC) at 1-800-222-1020 or cac@chevrolet.com. Make sure that they assign a case number. If we can reference enough case numbers in one letter to CAC, they might move on a solution.

Marina Blue

Chevrolet advertises that unnecessary throttle movements are eliminated, which gives better highway gas mileage. I don't know whether this feature is for better mileage or to help control detonation in this high-compression engine. It may accomplish both.

The last stick shift I drove, before my C6, was my 1967 Chevelle. Throttle response was immediate and the clutch felt much more connected. The C6 clutch-throttle combination was not to my liking in the beginning, but now I have no problems starting on a hill. I can easily start on a very heavy grade with practically no roll-back and very little clutch slippage. It takes some getting used to, but the clutch-throttle combination will feel natural after more time and experience.

Tom400CFI

I agree w/the OP; The throttle response is terrible. I can't beleive how much worse it is than cars from the '80's! Not the right direction.

mlongo99

1 second is a GROSS exageration. I drive it just like my other manual transmission car, which I do drive frequently. I don't need excessive clutch slip to avoid stalling. The clutch is trickier to learn than most, since there's not much feedback from it, but other than that, nothing about driving this car strikes me as odd.

I'm pretty sure the revs drop slowly because the programming is set that way. Not sure why though.


BTW, even if you could convince someone that the car is prone to stalling, claiming that it's a safety issue is quite a stretch.

oneblackvette

Ok at first I thought you were joking. The C6 as most newer cars for emissions idles low at 650 rpms. Before going any further I would disconnect the battery for 5 mins then reconnect. Be sure that ALL accessories are off before you restart the car. Make sure to reset your window stops. This makes the PCM begin to learn a few things all over again. It helps the PCM reestablish the idle and how to get there.

There is a big input difference between free revving and revving under load.
The trans likes to meet the gear , I find I have to keep on the throttle touch a little to make prefect up shifts.

As for your “This defect causes the following problems.” That was a joke right?

Just for reference what was your last two cars?

PS do people really shift at such a low rpm that they really use that 1-4 skip?

foliva

I've got an 07 Z51 with manual. I've noticed the problem you describe, however, I did not do the extensive testing you've done. When I blip the throttle from idle, I notice a lag in throttle response. The lag is not 1 second, but it is noticable.

I also noticed that the car was difficult to drive smoothly due to what I believed was a clutch issue. It wasn't bad, but it was noticable. I was able to drive my 93 Vette with manual alot smoother. I've been autocrossing for about 8 years & alway practice smooth driving & gear transitions on the street - all within legal limits.

I recently had my car tuned by Chuck Cow when he was in Orlando. After the tune, the first thing I noticed was that the throttle response was better -- not perfect, but better. The throttle tip-in was also ALOT better. I can now engage the clutch & shift (toe-heel) much smoother than before.

At the time the car was tuned, I spoke to Chuck about my throttle response observations. He said that his tune would help, but the end result would not be perfect since there was an issue with accessing the throttle control algorithms -- probably due to liability reasons.
His assessment of what the end result of his tune would do regarding throttle response was accurate -- better but not perfect.

Before the tune, I thought I would have to possibly go with another clutch or, as some have suggested, a C5 clutch spring. Now, I do not believe that I need it. The COW tune was well worth the money spent for this issue alone.

GeneL

Thanks to all that have commented. My answers to questions raised:

Although the lag may not be 1 full second, it is much closer to 1 second than 1/2 second.

Last two standard shift cars were a 2000 Miata and a 91 Vette.

The 1-4 shift sneaks in once in a while. I plan to buy a kit to disable.

foliva, I am very interested in your tuning solution. Can I do this myself? I have seen many threads regarding the purchase of tuning kits. What happens to the GM warranty?

mlongo99

Even though there's a slight delay when idling and you give the throttle a quick stab, I can't say I've ever had to be conscious of it when actually driving the car. Does it actually act differently? I don't know. But I can say that it's been a non-issue for me.

If you're going to get a tune, you can disable the skip-shift via programming. For most people, getting a tune is best left paying a pro to do it. If you're only going to need it once, it's cheaper that way, plus you're using their knowledge and taking the guess work out of it. If you're thinking of doing it yourself just to save on labor costs, think again and pay someone. If you plan on tuning frequently as you mod the car, and have a real interest in learning how to do it, then doing it yourself may be the way to go.

If your car is stock, or near stock, you can save money by doing a mail-order tune. It won't be absolutely perfect, but it will be damn close. There are 2 well respected tuners that I can think of on this site that offer such services. I've heard nothing but good things about both of them. I went that route and have been very happy with the results. It was an excellent value.

As for warranty coverage, there's no definite answer, but the chance of being denied coverage due to a tune are very low. They would need to claim that tuning led to the damage of the broken part, which eliminates lots of possible failures. Second, how would they ever even know it was tuned? Looking at your parameters is just something that isn't done during troubleshooting/repairs, and even if they did, how would they know the numbers had been changed? Some people are more paranoid about it, but IMO odds of getting denied warranty are slim to none. I would be much more concerned about other mods that you could detect just by looking at them.

Jahan

I think the reason for the delay is to improve emissions and fuel economy, but I'm not sure how.

I have noticed that The C6 doesn't have that right now throttle response that my 98 Mustang GT (supercharged/tuned) or G35 Coupe had. I've driven several sports cars that just don't feel as fast or sporty as they should because of poor tip-in and throttle response. Ford GT, Many Corvettes, GTO, CTS-V, etc.

I'm hoping a good tune will do the job with my 08.

Thrill6

I have a 99 C5 and a 2007 Z51 C6, both with manual transmissions and I have never noticed any delay in throttle response (and both are drive by wire.) I have noticed that the spring rate on the clutch pedal on the C5 is smoother than that on my C6 and getting the clutch to engage smoothly is much more difficult. There are quite a few threads where people have replaced the spring on the C6 with the C5 spring and have commented on how they like it much better (and the clutch is easier to engage smoothly) I think the spring costs around $10 and is pretty simple to install.

I think the testing that you have doesn't mean anything. The engine computer is very smart and knows that that there isn't any load on the engine, and the car is standing still which is different than real world conditions. Pushing the gas pedal in hard at idle and then letting go (as in Test 1) is not a real world test, nobody drives that way. If you press the gas pedal slowly, you will not see any delay in throttle response. If there was any delay in throttle response in real world driving conditions, I'm sure people would notice it, expecially the guys who track their cars.

JFTaylor

Clean out your Mass Air Flow Sensor.

Get a reputable brand MAF cleaner.
Remove the MAF sensor
Spray (Do Not Touch) the interior wires & the sides until clean
Let dry naturally
Reinstall.

JLMounce

I've experience this from day 1 in my car.

Though not close to what I would consider 1 second, it's noticeable.

I notice, that depending on engine speed, vehicle velocity, and a host of other seemingly random variations that the throttle almost seems to "ease" in disregarding speed of throttle input.

In realistic terms it is not slower, but at times this car certainly "feels" slower than my 99 Cobra.

Certainly something that is noticeable. In fact I'm almost at the point of selling the car because of little issues like this. The car is smooth, and looks sexy and handles nicely, but it feels very casterated by the factory programming. Not unless every input is ideal do you reall get your 400hp.

My next step is to try a tune, but I fear if this does not cure some of these issues with my "performance" car, that the garage may find itself without a Corvette.

oneblackvette

robbiC5

My '05 has 4600 miles on it and the lag has been there since day one. I would also say that it is between 1/2 and 1 second but out driving, I don't really notice it. What I'm saying is that it doesn't really have any adverse affects, I only notice it when I'm tinkering with the car in the driveway and rev it a few times.

Invisiguard

lol, first off, I feel sorry that you wasted so much time testing this out thinking it was a 'defect'.

nope, this is a 'feature' of most modern electronic throttles. The reduction in quick throttle response (supposedly) improves fuel economy and emissions, I just think its annoying, but you get used to it, the poserers there you just have to put your foot into it further. Lighter flywheel, a tune, and ported TB also pick up more throttle response.

foliva

Yes, I believe that you can do this yourself. The caveat is that it will take you time to understand how all the various tables interact, and how manipulate them to do what you want.

I had a former colleague do this on his BMW M3. After a year, he understood his system well enough to provide the service for others. But, he also ended up selling the car after a year because of the hard miles he put on it gaining the expertise (it was also turbocharged).

Clearly, what you pay for with a tuner is his expertise. This stuff is learnable, but you need to decide for yourself if you want to travel down that road.

I opted for spending money versus time to get a good tune.

foliva

GeneL: Regarding the warranty, there are people on this board who have a much better understanding than I do about this, but my view is you're playing the odds with the warranty issue.

If you have a minor problem with the car that's engine related, the odds are the dealer will take care of the problem & get the car out of the shop.

If you have some sort of catastrophic engine problem, the odds are they're going to dig a little deeper before honoring the warranty.

Remember, you can do some damage by 'simply' moving the peak firing pressure to the point where it occurs at exactly TDC. There's a company in Calgary that has a huge connecting rod in front of their building that's twisted like a pretzel because this happened. Betcha that cost someone a BUNCH of money!

chucky7

[QUOTE=GeneL;1561041306]Thanks to all that have commented. My answers to questions raised:

Although the lag may not be 1 full second, it is much closer to 1 second than 1/2 second.

Last two standard shift cars were a 2000 Miata and a 91 Vette.

The 1-4 shift sneaks in once in a while. I plan to buy a kit to disable.

Pull fuse (I think it is #10) under the hood. You won't need a 1-4 kit then. It will disable it for you.

Do a search if you aren't sure

Charlie