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Hi - I took the car to a dealer and they compared it to a new car (2019?), It was automatic, so not a manual like mine, but claimed it behaved the same way. So nothing was resolved. My feeling is that this is something that was coded into the drive by wire software of the PCM for some reason. It sucks, but is what it is I suppose. I am really surprised more people have not found this exact same issue. A lot of the other posts seem to be unrelated. This is specifically in other than 1st gear - there is ZERO lag in frst gear. As I sais in y original post, if you feather the trottle and watch the supercharger gauge go towards boost just slightly, and then give it throttle, I don't feel much if any lag. If you just go at a steady speed without any throttle and add throttle - you feel that lag.
 

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Let me just add to be clear - the lag occurs in other than first gear, at ANY amount of throttle - even flooring it - UNLESS you lightly feather the throttle just before accelerating more aggressively. The slight feathering moves the supercharger boost gauge slightly toward neutral, but it is still well within negative territory. Frankly I am not sure exactly what that gauge is telling me when it is in negative territory. Even if there is a wastegate of some sort and it is open prior to nailing the throttle, why would I need ANY boost to feel instant response? The weather is now getting nice - I will try steady state at 4K rpm and higher to see what happens. I think it did the same thing there, but will confirm. Going through the gears from 1st to 4th show no lag.
 

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I think your boost gauge is measuring manifold pressure and when it is negative it probably means that it is below one atmosphere, and that the supercharger output is being bypassed. Regardless, I agree, you should not need any boost to get a reasonable response (what you are used to from similar sports cars).

From what you are describing, going from negative - less negative while cruising, seems like the actual throttle blade position is somewhere in the 25-35% range regardless of rpm's or accelerator pedal position.
 

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I have ‘17 Z06 M7.
I have not experienced any of the lag described.
I also have my exhaust set manually on “track” mode all the time regardless of the suspension modes selected (eco, weather, T, S, Tr).
Not sure if that maybe a contributing factor or not.
The only time I may be experiencing a lag is when I’m tooling around and just heel/toe downshifting, the throttle does not blip up as quickly.
Otherwise, no issues...


Sent from my iPhone using Tapatalk
 

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Thanks Landrew. Report back what you experience at higher RPM. I'd also suggest picking up an OBDII bluetooth dongle and use Torque or similar app to log your throttle, boost, airflow, etc. I don't know if there is a can reading for the bypass, but that would definitely tell us what is going on.

Manta-C7, while I applaud [email protected]'s work, I am not seeing how this is particular behavior is a throttle body issue. I may not have hit the floor but I am sure I was over the 25-35% range, and Landrew has said he's tried all positions including the floor. The PCM could actually be limiting the throttle position, but I would only buy that theory if it also did it in first gear.

What it sounds like is cruising at a steady speed opens the bypass, and then feathering it closes it so there is no lag. But without feathering the throttle first, the car is either delaying closing the bypass, or possibly gradually closing it.

Landrew, I may be telling you something you already know, but with the throttle closed, the engine is still trying to displace 6.2L of air, which is why you have vacuum.

(edit) Saw that [email protected] is Manta-C7's new name on corvetteforum. When and if I get my C7, I'll be experimenting with the TB for sure. Cheap mod that won't void the warranty. I am trying to convince my friend with the Z06 to try it, but he's new to this and afraid to mess with his stock car.
 

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JDWK, agree that a log is needed to properly troubleshoot. Another way to tell bypass is by monitoring manifold pressure, the valve should start closing at 10 inHg vacuum and be fully closed at 3.5 inHg vacuum.

When you are cruising you are at part throttle, and I don't think just by feathering it will reach the 10 inHg threshold to activate charge air. There is something going on at part throttle, which may or may not be the same that happens at wider throttle opening.
 

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Thx for all the suggestions guys. So I tried setting exhaust only to track as Shihhanshow's post indicates and holy crap - I think that did it. Maybe just a hint of lag if any - but way different from just being in overall Sport mode. The car seems transformed. I thought I had the console setting in track at one point and that didn't do it but I may have been mistaken. Will try that again next time out. Bottom line is that just changing sound to track made a huge difference and I am happy to leave it there. I always drive in sport and never thought the sound was much different when in full track mode, but I may not have pushed it enough to tell the difference. Anyway, the louder the better!
 

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Wow, good news, but that's really odd. I had the pasm in track, but I didn't even know the exhaust had a separate control, and I would have never thought it would cause the delay in boost that I felt. Is it possible I had the pasm in track, and the exhaust in comfort/street? Definitely test it out more when you get the chance, but logs would still be better.
 

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Wow, good news, but that's really odd. I had the pasm in track, but I didn't even know the exhaust had a separate control, and I would have never thought it would cause the delay in boost that I felt. Is it possible I had the pasm in track, and the exhaust in comfort/street? Definitely test it out more when you get the chance, but logs would still be better.
Well you are right. I must have been hallucinating. I went out for an extended ride and the lag is still there. It's there with just the exhaust setting as well as complete track mode and even at 4k rpm tho perhaps less are 4 k. I think when I went out before I was so used to feathering the throttle that I didn't do a good test. I should note that the lag isn't noticeable under light throttle. It's just when I more aggressively mash the throttle. Then there is a slight pull and a half second later it blasts off. I'll try to figure out how to gets logs.
 

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Yeah our brains can play tricks on us, which is why measurements are always better. Looking forward to those logs. I am going to test drive a C6 ZR1 in a couple weeks to see if it has a similar response, however, it is tuned so that doesn't make it a fair comparison. That may be the way to go for me. Not much cheaper than a new Z06, but it has its pros and cons. I've always wished car manufacturers (particularly Chevy) would sell me a new car without the drivetrain warranty for like $5k less, so I can mod away on a new car. You don't want to do that with a first model year, but towards the end, like now, I think it would be a good bet.
 

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Hi all - so I took my time to reply because I really wanted to drive the car a few times before saying this. I have a new theory. I think the car is learning how I drive. After all the attempts to punch the throttle to see if the lag is still there, I now have almost zero lag. The difference between now and a couple months ago is clear. Perhaps the ECM needed to learn my driving habits. The previous owner was someone that has many cars and always has a vette or two. I know you can't tell by talking to someone, but I don't think he drove very aggressively. He said he liked the non-Z07 version and had owned both. So hopefully this is the deal. Thanks again for your help.
 

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Hi all - so I took my time to reply because I really wanted to drive the car a few times before saying this. I have a new theory. I think the car is learning how I drive. After all the attempts to punch the throttle to see if the lag is still there, I now have almost zero lag. The difference between now and a couple months ago is clear. Perhaps the ECM needed to learn my driving habits. The previous owner was someone that has many cars and always has a vette or two. I know you can't tell by talking to someone, but I don't think he drove very aggressively. He said he liked the non-Z07 version and had owned both. So hopefully this is the deal. Thanks again for your help.
Hmm, an A8 does change it's shift timing and speed based on driving habits. Shift changes in a manual are all controlled by your head! Unless you are changing driving mode there are no other changes affecting Tip-In or lag (unless the car in named Christine!)

Have new graphs that attempt to display the difference between a controller for throttle Tip-In and a modified throttle Body that alters the shape of the entrance and exit.

They control two different things. Perhaps that will help define what can alter a "lag."

Throttle Body.jpg transient_flow_& Katech paper.jpg
 

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^^^^^ Yes, they do. I have one of those and it takes care of lag and also makes power delivery more linear, you always know what the car is going to do. I have had other ported ones before and the Soler one at Sandyeggo is the best one by a good margin. Incredibly easy to install too.
 
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