[PRAY]

FMJ-jr. I hope this doesn't come off as a hijack. It is all for the sake of going faster.

Snow,

I absolutely believe you holding gear benefited your case. But I have some things I would like to ask and point out.

Your first run was at 6:18, what time was your last run? Was there a large DA shift to the negative in that time frame? This is just simply a question and doesn't have a lot to do with my next portion.

My next point is time in gear and shift extension. I personally believe that 1/2 and the 2/3 shift need to be executed at 6,500 due to shift recovery rpm and the overall time spent in those gears. There isn't enough time for the loss of power after peak to take effect. I was seeing about a 20rw drop by 6,500 from peak on my car. 3/4 and 4/5 I am still not really sure on. Somewhere around 6,300 should be about right since the recovery rpm for those shifts, especially the 3/4 is around or above 5K. You are also in those top two gears for about 40% of your run. You are in 3/4/5 for about 65% of your run. I think anything that would generate more wheel speed and momentum in the lower three gears will only benefit the top end. Unfortunately we have to factor in TM at this point. Every time the car shifts it takes just under or up to .5 sec according to my logs. Timing gets cut about 150rpm or .12 seconds before the actual shift and doesn't come back in until .38 seconds after the shift. The crappy part is that once you get your timing back the TB blade closes for about .3 seconds as well. It doesn't happen every run and each time how drastic it is is different. But it is there and effecting E.T. and MPH. I am trying to nail down where that is coming from so I can get rid of it. I know it is part of TM but finding it will take some testing. So with four shifts you are losing up to 2 full seconds off of your run. Not to mention that while this is going on your MPH plateaus for a second and then picks back up as well hurting forward momentum. I plateau mph for .15 sec on the 2/3 shift. I lost 2mph on the 3/4 shift and it took .3 sec to recover that. I lost 1mph for .2 sec on the 4/5 shift.

This time in gear leads us to another phenomenon, COTS. From looking at my logs COTS is coming in right after the 2/3 shift and is in full effect by 6K in 4th where it is commanding almost a full point of enrichment. So for the majority of your long run out gears you don't have the correct amount of fuel. You are rich. With taller tires you may spend more or less time in the higher gears with less than ideal AFR. You will spend more time in 4th but may not have to shift to 5th depending on your finishing MPH. Timing could also be effected by the taller tires. The tires are putting more load on the engine to turn and could put it in parts of the timing map that can cause KR. Not saying it is but it could. It would have to be logged to be confirmed or denied. Just something to consider.

I do have concerns about taller tires that are unaccounted for in the tune since this is a tq based computer. Calculations are based off of all the stock gearing and tire heights and the feedback they provide to the car along with all the other sensors. What I don't know is if the height gives a false high or low tq reading. The actual MPH the computer is seeing for a certain RPM is much higher than what it is expecting to see due to height. But there could be some benefit there with the tq tables depending on which way the height effects the final output. There are also less shifts with a taller tire and more time spent in the lower gears with a taller tire. More time in the lower gears could stave off COTS a little longer. Another benefit is that .5 sec you get back for the last shift you don't have to execute.

I will have to think about how the transmission is figuring shift points since it is MPH based and RPM triggered. (which isn't true for the 1/2 and 2/3 shift. It is basically MPH dependent. You can raise the RPM to what every you want and it will still shift at 5,500.) You have to hit the MPH tables to get the 1/2 and 2/3 shifts up to a more acceptable RPM. The MPH the ECM/TCM is getting is a false reading compared to RPM. You will be at a much higher MPH for a given RPM with taller tires. This could actually be benefiting the pass if the leeway between the MPH/RPM split is large enough.

I have also read that the first three gears in the Camaro have the final drive ratio of a TH400 with a 4.10 gear. I haven't confirmed this as fact. Depending on the power of the vehicle, old schoolers have been running 28" tall tires forever. I ran them on my 69 Camaro. But I didn't have a 4/5/6 gear to shift to. I would really like to test a DR or slick of the stock height with 4 shifts vs. a tall tire with only three shifts. That would be an interesting test for sure. The 1/8th and 1/4 results would be really curious since in both scenarios you are short one shift with the taller tires. You can also look at it like you put a 2.42 gear in the rear with a taller tire over the 2.77 with the stock tire. I would assume that just like on a dyno this would attribute more power to the ground with less drive train loss. But then there over all tire weight to consider. SO MANY VARIABLES.

I am really glad this came up. Gave me lots to think about.

[Fraxum]

Originally Posted by PRAY

FMJ-jr. I hope this doesn't come off as a hijack. It is all for the sake of going faster.

Snow,

I absolutely believe you holding gear benefited your case. But I have some things I would like to ask and point out.

Your first run was at 6:18, what time was your last run? Was there a large DA shift to the negative in that time frame? This is just simply a question and doesn't have a lot to do with my next portion.

My next point is time in gear and shift extension. I personally believe that 1/2 and the 2/3 shift need to be executed at 6,500 due to shift recovery rpm and the overall time spent in those gears. There isn't enough time for the loss of power after peak to take effect. I was seeing about a 20rw drop by 6,500 from peak on my car. 3/4 and 4/5 I am still not really sure on. Somewhere around 6,300 should be about right since the recovery rpm for those shifts, especially the 3/4 is around or above 5K. You are also in those top two gears for about 40% of your run. You are in 3/4/5 for about 65% of your run. I think anything that would generate more wheel speed and momentum in the lower three gears will only benefit the top end. Unfortunately we have to factor in TM at this point. Every time the car shifts it takes just under or up to .5 sec according to my logs. Timing gets cut about 150rpm or .12 seconds before the actual shift and doesn't come back in until .38 seconds after the shift. The crappy part is that once you get your timing back the TB blade closes for about .3 seconds as well. It doesn't happen every run and each time how drastic it is is different. But it is there and effecting E.T. and MPH. I am trying to nail down where that is coming from so I can get rid of it. I know it is part of TM but finding it will take some testing. So with four shifts you are losing up to 2 full seconds off of your run. Not to mention that while this is going on your MPH plateaus for a second and then picks back up as well hurting forward momentum. I plateau mph for .15 sec on the 2/3 shift. I lost 2mph on the 3/4 shift and it took .3 sec to recover that. I lost 1mph for .2 sec on the 4/5 shift.

This time in gear leads us to another phenomenon, COTS. From looking at my logs COTS is coming in right after the 2/3 shift and is in full effect by 6K in 4th where it is commanding almost a full point of enrichment. So for the majority of your long run out gears you don't have the correct amount of fuel. You are rich. With taller tires you may spend more or less time in the higher gears with less than ideal AFR. You will spend more time in 4th but may not have to shift to 5th depending on your finishing MPH. Timing could also be effected by the taller tires. The tires are putting more load on the engine to turn and could put it in parts of the timing map that can cause KR. Not saying it is but it could. It would have to be logged to be confirmed or denied. Just something to consider.

I do have concerns about taller tires that are unaccounted for in the tune since this is a tq based computer. Calculations are based off of all the stock gearing and tire heights and the feedback they provide to the car along with all the other sensors. What I don't know is if the height gives a false high or low tq reading. The actual MPH the computer is seeing for a certain RPM is much higher than what it is expecting to see due to height. But there could be some benefit there with the tq tables depending on which way the height effects the final output. There are also less shifts with a taller tire and more time spent in the lower gears with a taller tire. More time in the lower gears could stave off COTS a little longer. Another benefit is that .5 sec you get back for the last shift you don't have to execute.

I will have to think about how the transmission is figuring shift points since it is MPH based and RPM triggered. (which isn't true for the 1/2 and 2/3 shift. It is basically MPH dependent. You can raise the RPM to what every you want and it will still shift at 5,500.) You have to hit the MPH tables to get the 1/2 and 2/3 shifts up to a more acceptable RPM. The MPH the ECM/TCM is getting is a false reading compared to RPM. You will be at a much higher MPH for a given RPM with taller tires. This could actually be benefiting the pass if the leeway between the MPH/RPM split is large enough.

I have also read that the first three gears in the Camaro have the final drive ratio of a TH400 with a 4.10 gear. I haven't confirmed this as fact. Depending on the power of the vehicle, old schoolers have been running 28" tall tires forever. I ran them on my 69 Camaro. But I didn't have a 4/5/6 gear to shift to. I would really like to test a DR or slick of the stock height with 4 shifts vs. a tall tire with only three shifts. That would be an interesting test for sure. The 1/8th and 1/4 results would be really curious since in both scenarios you are short one shift with the taller tires. You can also look at it like you put a 2.42 gear in the rear with a taller tire over the 2.77 with the stock tire. I would assume that just like on a dyno this would attribute more power to the ground with less drive train loss. But then there over all tire weight to consider. SO MANY VARIABLES.

I am really glad this came up. Gave me lots to think about.

Thanks Pray for the discussion. My DRs are taller than stock. I stay in 4th either way.

[Speedy1975]

Cliff notes please for us ADD types? LOL

[PRAY]

This is the stuff that keeps me up at night. LOL

Cliff notes:

1. Taller tires can help in certain circumstances due to less shifts with the stock ECM/TCM tunes. If your car is fast enough to need 4 shifts no matter what, then I think short tires will be faster.

2. Taller tires could also be effecting shift rpm up and possibly skewing the ECM/TCM calculated TQ tables. If the shift RPM is skewed up then it is a benefit. Not sure about the TQ tables.

3. I firmly believe COTS is kicking in on a lot of these stock cars. I think that is why the non tuned cars are usually only seeing 22-23mph on the top end. Weather could correct some of this. Cool down and times between runs along with ECT and IAT effect this greatly. Some people are seeing up to 27mph on the top end. I think 1/8 mph changes are due to the factory TCM changing the first three shift rpm's at will.

4. The TCM is costing a bunch of time at the track with the stock tune.

5. In my opinion the 1/2 shift and 2/3 shift need to be executed around 6,500. 3/4 and 4/5 probably 6,300. I will test this and see.

6. The stock tunes in the ECM/TCM are effected by so many factors that you never know what the heck is happening at the track if you don't log real data. It is almost impossible to tell what did what with out good logs.

I think that covers it.

[SS 1LE]

Originally Posted by PRAY

5. In my opinion the 1/2 shift and 2/3 shift need to be executed around 6,500. 3/4 and 4/5 probably 6,300. I will test this and see.

Really? Isn't the car not making anymore power and starting to drop off well before that? The two dynos I saw had power starting to drop off around 6000 if I recall...

[PRAY]

You are correct. But the car moves through 1st and 2nd so quickly it won't notice. It is all about shift extension and recovery rpm. Those two gears drop off hard to 4,600 or so when shifted at 6,500. TQ is pretty flat on these cars from 4,000-4,600 and then starts to fall but that is where hp takes over. TQ is what gets you going but hp keeps you going. So I want the car to shift back to peak tq or just past it to where the hp curve takes over. In the higher gears the car has time to realize the power loss and could nose over. The 3/4 shift at 6,500 takes you back to 5,160 or so. If you shift it at 6,300 it drops back to 4,900. 4/5 at 6,500 puts you back to 4,900 but realizes the most hp loss after peak being your longest gear at that rpm level. So shifting that at 6,300 and possibly 6,400 could be benefiting depending on set up and tire height. I am going to experiment with shifting 1st all the way up to 6,700, 2nd up to 6,600 and down from there to see what it gains or loss at the track.

[PRAY]

I have good buddy that I have worked very close with in the past that is the CTS-V king. His stock block, stock converter car has gone 9.1's@150+. The cars he does don't have big cams but he shifts them between 7,200 and 7,400. These are cars that make well over 700rw tq at the hit. He is running all stock ported blowers and they nose over as well. Still shifting that high makes him faster. In stock converter A8's we need all the tq down low we can get for the 60ft. But after that it is a hp race. If I could keep all my shift recoveries above 5K I would. I however wouldn't trade any mods that will drop my low end tq off. Every tenth in the 60ft is worth two tenths on the big end. TQ with a stock converter are critical.

[JFM-jr]

I do not have datalog capabilities I wish I did. Everything points to COTS for me tho with a trap speed speed of over 96mph at the 1/8 yet it fell just short of 23mph on the back half.

[Speedy1975]

Originally Posted by PRAY

This is the stuff that keeps me up at night. LOL

Cliff notes:

1. Taller tires can help in certain circumstances due to less shifts with the stock ECM/TCM tunes. If your car is fast enough to need 4 shifts no matter what, then I think short tires will be faster.

2. Taller tires could also be effecting shift rpm up and possibly skewing the ECM/TCM calculated TQ tables. If the shift RPM is skewed up then it is a benefit. Not sure about the TQ tables.

3. I firmly believe COTS is kicking in on a lot of these stock cars. I think that is why the non tuned cars are usually only seeing 22-23mph on the top end. Weather could correct some of this. Cool down and times between runs along with ECT and IAT effect this greatly. Some people are seeing up to 27mph on the top end. I think 1/8 mph changes are due to the factory TCM changing the first three shift rpm's at will.

4. The TCM is costing a bunch of time at the track with the stock tune.

5. In my opinion the 1/2 shift and 2/3 shift need to be executed around 6,500. 3/4 and 4/5 probably 6,300. I will test this and see.

6. The stock tunes in the ECM/TCM are effected by so many factors that you never know what the heck is happening at the track if you don't log real data. It is almost impossible to tell what did what with out good logs.

I think that covers it.

Cool. I'm a data logging nut. I hit the track for the first time with my 2SS on Sat. Diablo hasn't released support for the 2016 Camaro SS yet (but did the SS for whatever reason) so I couldn't get my good data log I'm used to. However I did use an OBDII tool and have a log. I need to review to see how thorough it was. I'll share what I see in the thread I posted.

http://www.camaro6.com/forums/showthread.php?t=471802

[JFM-jr]

Originally Posted by PRAY

FMJ-jr. I hope this doesn't come off as a hijack. It is all for the sake of going faster.

I FULLY welcome the ongoing discussion

Originally Posted by PRAY

I will have to think about how the transmission is figuring shift points since it is MPH based and RPM triggered. (which isn't true for the 1/2 and 2/3 shift. It is basically MPH dependent. You can raise the RPM to what every you want and it will still shift at 5,500.) You have to hit the MPH tables to get the 1/2 and 2/3 shifts up to a more acceptable RPM. The MPH the ECM/TCM is getting is a false reading compared to RPM. You will be at a much higher MPH for a given RPM with taller tires. This could actually be benefiting the pass if the leeway between the MPH/RPM split is large enough.

Couldnt you just raise the MPH figures to say 220MPH wich would eliminate it from the equation and leave RPM as the remaining/sole shift dependent parameter?

[laynlo15]

I know there is more left, but not this year. It was 2000 DA and 82 degrees, my car was heat soaked like crazy. There were almost 100 cars in one of my classes and over 80 in the other class and it was pretty hot under the hood when I got into the water box, so I'm sure my 60' times and my ets suffered, as you noted I do have one of the higher mph cars on the board considering my mods. Its just the heat here in Missouri and the number of cars hurts a bunch. Just no way to keep the car cool under the hood going thru the staging lanes. I'll take 3 barrels instead of 2.

[PRAY]

Originally Posted by JFM-jr

I FULLY welcome the ongoing discussion


Couldnt you just raise the MPH figures to say 220MPH wich would eliminate it from the equation and leave RPM as the remaining/sole shift dependent parameter?

No, not from what I saw in the C7 I was working with. EFI Live didn't have the RPM tables available yet so all I had was MPH to work with and I was none the wiser. When I got to a certain MPH the car wouldn't shift any more. It would just over rev and skip a gear. Not good at all. I had to drop the MPH back to where it would execute shifts. Turns out I surpassed the MPH threshold for the RPM and there was no buffer anymore either. So the trigger wasn't being met before the execution command to shift. It F'ed it all up. I think also from what I am seeing in the logs is that the TM drops out prior to the actual shift. So it has to do something with the MPH vs. RPM delta. If it waited till the RPM to actually shift it wouldn't know to drop out spark for TM.

[JFM-jr]

https://m.facebook.com/story.php?sto...&id=1659042438

Video of my 11.65 run as you can see the place was empty

[laynlo15]

Don't have facebook