When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Two things to check/do.
1. Check the trans fluid level and if it's correct by the book, then add between 1/2 and a full quart.
2. Make sure the trans fluid temp is at least 150 F before leaving the staging lane.
Two things to check/do.
1. Check the trans fluid level and if it's correct by the book, then add between 1/2 and a full quart.
2. Make sure the trans fluid temp is at least 150 F before leaving the staging lane.
Thanks but I had zero issues with trans.
Belwo log is shifting at 7900 rpm
60ft is 1.62
Log below for shifting at 8100 rpm
60 ft = 1.599
Long story short, faster 60f shifting at 8100 although it takes longer time to shift both 1-2 and 2-3, compared with shifting at 7900 rpm (1.599s vs 1.62s).
You say you have zero trans issues. Your scans say you do. Doesn't it make you wonder why I launch at 1800, shift at 6800, have the same 4000 Yank and 2.56 rear gear, but only bolt-ons with about 100 less HP, yet cut .10 quicker 60's and ET's and nearly the same mph?
You say you have zero trans issues. Your scans say you do. Doesn't it make you wonder why I launch at 1800, shift at 6800, have the same 4000 Yank and 2.56 rear gear, but only bolt-ons with about 100 less HP, yet cut .10 quicker 60's and ET's and nearly the same mph?
you are clearly missing the point. If I shift at 6800, my ET is 11.4-11.5. What makes you say that I have trans issues? Rpm bumps when the TC is engaged?
You say you have zero trans issues. Your scans say you do. Doesn't it make you wonder why I launch at 1800, shift at 6800, have the same 4000 Yank and 2.56 rear gear, but only bolt-ons with about 100 less HP, yet cut .10 quicker 60's and ET's and nearly the same mph?
pls dont get me wrong, really appreciate your inputs. I have cleared all trans issues surely. I would blame either suspension or track prep. Will keep you posted
2020 Corvette of the Year Finalist (track prepared)
2019 C6 of Year Winner (track prepared)
Originally Posted by GrandpaC6
you are clearly missing the point. If I shift at 6800, my ET is 11.4-11.5. What makes you say that I have trans issues? Rpm bumps when the TC is engaged?
A few observations...
You're not launching at 2700RPM. The converter is probably flashing that high but you're definitely not launching at that RPM.
When you mention the torque converter engaging, if you're talking about locking up the clutch at WOT then that's a really bad thing to do. Not only will it slow you down, it's also only a matter of time before you burn up the clutch completely as it's not designed to be engaged at WOT. Yank converters are super efficient so locking them is totally unnecessary.
You've got really big timing drops when the car shifts. It's hard to tell from the scans whether you're hitting the rev-limiter or TM is still enabled in the transmission but either way that's costing you a good two tenths (one per shift) on the first scan and on the second it looks like it does it right after you launch and then two more times after that.
Track prep and suspension issues aren't affecting you at all as you don't appear to be spinning at any point, at least on those two scans.
Your correlation between higher shift RPM and better 60ft times is quite possibly incorrect as the difference between 1.599 and 1.62 is negligible at best. Just today for instance my 60ft times were 1.400, 1.383 and then 1.401 without changing a single thing, and the runs were made approximately 15-20 minutes apart so the weather wasn't a factor nor was track prep as I almost never spin off the line anymore.
On paper your car should be a lot faster as I've gotten 3 cars to run in the 10.7s while only making a little over 400rwhp AND with only 3600 converters.
As others have mentioned I also believe you're spinning the motor too high. Just because you can go that high doesn't mean you should. As a frame of reference I lowered my shift points down from around 7800 to 7300 to try to avoid oil starvation issues. As it turns out the car actually picked up a bit much to my surprise. A good rule of thumb that's worked for me is to shift at peak HP and have the shift extension fall back down to where your peak torque occurs.
You're not launching at 2700RPM. The converter is probably flashing that high but you're definitely not launching at that RPM.
When you mention the torque converter engaging, if you're talking about locking up the clutch at WOT then that's a really bad thing to do. Not only will it slow you down, it's also only a matter of time before you burn up the clutch completely as it's not designed to be engaged at WOT. Yank converters are super efficient so locking them is totally unnecessary.
You've got really big timing drops when the car shifts. It's hard to tell from the scans whether you're hitting the rev-limiter or TM is still enabled in the transmission but either way that's costing you a good two tenths (one per shift) on the first scan and on the second it looks like it does it right after you launch and then two more times after that.
Track prep and suspension issues aren't affecting you at all as you don't appear to be spinning at any point, at least on those two scans.
Your correlation between higher shift RPM and better 60ft times is quite possibly incorrect as the difference between 1.599 and 1.62 is negligible at best. Just today for instance my 60ft times were 1.400, 1.383 and then 1.401 without changing a single thing, and the runs were made approximately 15-20 minutes apart so the weather wasn't a factor nor was track prep as I almost never spin off the line anymore.
On paper your car should be a lot faster as I've gotten 3 cars to run in the 10.7s while only making a little over 400rwhp AND with only 3600 converters.
As others have mentioned I also believe you're spinning the motor too high. Just because you can go that high doesn't mean you should. As a frame of reference I lowered my shift points down from around 7800 to 7300 to try to avoid oil starvation issues. As it turns out the car actually picked up a bit much to my surprise. A good rule of thumb that's worked for me is to shift at peak HP and have the shift extension fall back down to where your peak torque occurs.
pls dont get me wrong, really appreciate your inputs. I have cleared all trans issues surely. I would blame either suspension or track prep. Will keep you posted
Stretch out your scans so you can see at least 5 times the current length. Look at your launch rpm vs mph and watch it rise then fall slightly and rise again. The most likely cause is pump cavitation from lack of fluid and that kills 60 ft times. You get the same issue upon those high rpm shifts, which is what subfloor mentioned. That's why I said to overfill the trans to avoid starving the pickup when the fluid climbs up the back of the pan.
Cold fluid adds to the problem, due to lack of volume. I personally will sit in the staging lines with the engine running and in gear, just to heat fluids.
You have lots of power that's trying to make up the difference that your trans is loosing.
2020 Corvette of the Year Finalist (track prepared)
2019 C6 of Year Winner (track prepared)
Originally Posted by HOXXOH
Stretch out your scans so you can see at least 5 times the current length. Look at your launch rpm vs mph and watch it rise then fall slightly and rise again. The most likely cause is pump cavitation from lack of fluid and that kills 60 ft times. You get the same issue upon those high rpm shifts, which is what subfloor mentioned. That's why I said to overfill the trans to avoid starving the pickup when the fluid climbs up the back of the pan.
Cold fluid adds to the problem, due to lack of volume. I personally will sit in the staging lines with the engine running and in gear, just to heat fluids.
You have lots of power that's trying to make up the difference that your trans is loosing.
I'm almost positive the RPM fluctuations are due to the engine timing being pulled on the shifts, not from fluid starvation as his 60ft times simply aren’t low enough.
And rather than post better pictures just go ahead and post the actual scans and tune. I'll be able to tell you quite a bit as to whats going on during the passes that way.
Stretch out your scans so you can see at least 5 times the current length. Look at your launch rpm vs mph and watch it rise then fall slightly and rise again. The most likely cause is pump cavitation from lack of fluid and that kills 60 ft times. You get the same issue upon those high rpm shifts, which is what subfloor mentioned. That's why I said to overfill the trans to avoid starving the pickup when the fluid climbs up the back of the pan.
Cold fluid adds to the problem, due to lack of volume. I personally will sit in the staging lines with the engine running and in gear, just to heat fluids.
You have lots of power that's trying to make up the difference that your trans is loosing.
I am positive that I have at least overfilled the trabs by 2 quarts. Just emailed subfloor the tune. Now it is better, still have timing drop 1-2 shift
I am positive that I have at least overfilled the trabs by 2 quarts. Just emailed subfloor the tune. Now it is better, still have timing drop 1-2 shift
I'm still seeing the RPM on the launch rise quickly, then fade and rise again, vs the MPH which has a steady rate. I don't see anything else that'd cause that to happen.
BTW, what's your fluid fill procedure?
2020 Corvette of the Year Finalist (track prepared)
2019 C6 of Year Winner (track prepared)
Originally Posted by HOXXOH
I'm still seeing the RPM on the launch rise quickly, then fade and rise again, vs the MPH which has a steady rate. I don't see anything else that'd cause that to happen.
BTW, what's your fluid fill procedure?
The behavior of his RPM is totally normal and not indicative of a problem.
When the car first launches the RPM rises quickly, subsides a bit and then starts rising again. The part where it subsides (at the white line shown below from one of my recent scans) is right where the converter couples (to quote Dave Myers from Yank). I can't remember the terminology as it's been years since I've had to explain it, but it's no different than when you start off reasonably quickly from a stop light, where the RPMs rise then settle in as the car starts moving forward.
The behavior of his RPM is totally normal and not indicative of a problem.
When the car first launches the RPM rises quickly, subsides a bit and then starts rising again. The part where it subsides (at the white line shown below from one of my recent scans) is right where the converter couples (to quote Dave Myers from Yank). I can't remember the terminology as it's been years since I've had to explain it, but it's no different than when you start off reasonably quickly from a stop light, where the RPMs rise then settle in as the car starts moving forward.
So maybe it's the difference in power level or launch RPM, but his starts to fade a lot before rising and your's get's to a more constant rate of rise. When mine (admittedly lower power) faded that much before rising again, an extra quart made the scans look like your's and the 60' time became quicker.
BTW, I've always regretted not taking your offer to change plugs at Sonoma. It might have run quicker than the 10.80 at Sacramento the previous day.
We have modified the torque mgmt as well as acceleration thresh tables. Now the timing doesn’t drop between shifting.
yesterday, we participated in a rollrace. We managed to achieve a trap speed of 131 mph three times. I though we could easily get 135+ as our best 1/4 trap speed was 128. RPM when we crossed the line was 6700. Probably a different rear gear other than 2.56 may work better, aiming 7500 rpm at the finishing line on third. Any idea whether I can use 2.73 grand sport rear diff or not? Is it a bolt on option for c6 A6?
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Slideshow: A Jaguar designer's personal project imagines what a modern front-engined Corvette might look like if Chevrolet revisited the golden age of the Stingray.
