Question for the engine gurus out there...
06-02-09, 06:10 AM
#16
Putting in the 3.76 rear will still allow a top speed of 177mph at 6500rpm. I have the same 3.76 rear end gearing but rev the engine to 8000rpm which should technically net 218mph in 5th gear at redline.
Taking into factor of a stock A650E transmission gear ratios you will get approximately the following speeds:
3.23 GS4 stock gearing will allow a top speed of 206mph @6500rpm in 5th gear
3.76 gearing top speed of 177mph@6500rom in 5th
3.92 geairng top speed of 170mph@6500rpm in 5th
4.27 gearing top speed of 156mph@6500rpm in 5th
Taking into factor of a stock A650E transmission gear ratios you will get approximately the following speeds:
3.23 GS4 stock gearing will allow a top speed of 206mph @6500rpm in 5th gear
3.76 gearing top speed of 177mph@6500rom in 5th
3.92 geairng top speed of 170mph@6500rpm in 5th
4.27 gearing top speed of 156mph@6500rpm in 5th
06-02-09, 08:34 AM
#17
Lexus Champion
I looks like Lexus limits the top speed by limiting RPM in top gear.
5th gear with stock gearing = 149mph at 4650rpm.
The interesting thing is that stock gearing at redline (6300rpm) in 4th gear = 153mph
With the Supra 3.769 ratio the electronic limit of 4650rpm = 125mph.
Redline in 4th = 127mph.
My LS400 drops from an indicated ~6200rpm to 5000-5100rpm 1st to 2nd shift.
If your torque converter is staying locked that should not be due to the torque converter itself but rather the signal to lock/unlock from the ECU.
If this is happening it would not cause (in and of itself) other tranny problems.
Another thought is how quickly your transmission shifts. Stock shifting is slow. During this transition there is load applied and by the time the shift is complete the resulting revs would probably be higher that a quicker shift that pulls down on the engine more quickly. Cars with the PI torque converter tend to shift more quickly. Again, something is going on here.
5th gear with stock gearing = 149mph at 4650rpm.
The interesting thing is that stock gearing at redline (6300rpm) in 4th gear = 153mph
With the Supra 3.769 ratio the electronic limit of 4650rpm = 125mph.
Redline in 4th = 127mph.
My LS400 drops from an indicated ~6200rpm to 5000-5100rpm 1st to 2nd shift.
If your torque converter is staying locked that should not be due to the torque converter itself but rather the signal to lock/unlock from the ECU.
If this is happening it would not cause (in and of itself) other tranny problems.
Another thought is how quickly your transmission shifts. Stock shifting is slow. During this transition there is load applied and by the time the shift is complete the resulting revs would probably be higher that a quicker shift that pulls down on the engine more quickly. Cars with the PI torque converter tend to shift more quickly. Again, something is going on here.
06-02-09, 11:58 AM
#18
I looks like Lexus limits the top speed by limiting RPM in top gear.
5th gear with stock gearing = 149mph at 4650rpm.
The interesting thing is that stock gearing at redline (6300rpm) in 4th gear = 153mph
With the Supra 3.769 ratio the electronic limit of 4650rpm = 125mph.
Redline in 4th = 127mph.
My LS400 drops from an indicated ~6200rpm to 5000-5100rpm 1st to 2nd shift.
If your torque converter is staying locked that should not be due to the torque converter itself but rather the signal to lock/unlock from the ECU.
If this is happening it would not cause (in and of itself) other tranny problems.
Another thought is how quickly your transmission shifts. Stock shifting is slow. During this transition there is load applied and by the time the shift is complete the resulting revs would probably be higher that a quicker shift that pulls down on the engine more quickly. Cars with the PI torque converter tend to shift more quickly. Again, something is going on here.
5th gear with stock gearing = 149mph at 4650rpm.
The interesting thing is that stock gearing at redline (6300rpm) in 4th gear = 153mph
With the Supra 3.769 ratio the electronic limit of 4650rpm = 125mph.
Redline in 4th = 127mph.
My LS400 drops from an indicated ~6200rpm to 5000-5100rpm 1st to 2nd shift.
If your torque converter is staying locked that should not be due to the torque converter itself but rather the signal to lock/unlock from the ECU.
If this is happening it would not cause (in and of itself) other tranny problems.
Another thought is how quickly your transmission shifts. Stock shifting is slow. During this transition there is load applied and by the time the shift is complete the resulting revs would probably be higher that a quicker shift that pulls down on the engine more quickly. Cars with the PI torque converter tend to shift more quickly. Again, something is going on here.
-I can't bring it to the dealership (who supposedly knows all about Lexus vehicles) because they would say they can't "possibly" diagnose the car due to the modifications.
-I cant's bring it to a local shop because they may not know how to fix this particular issue due to my mods.
This is the annoyance of modding because if an issue should arise it is hard to decipher which mod is causing the problem.
06-02-09, 12:22 PM
#19
Lexus Champion
...what should I do J?
-I can't bring it to the dealership (who supposedly knows all about Lexus vehicles) because they would say they can't "possibly" diagnose the car due to the modifications.
-I cant's bring it to a local shop because they may not know how to fix this particular issue due to my mods.
This is the annoyance of modding because if an issue should arise it is hard to decipher which mod is causing the problem.
-I can't bring it to the dealership (who supposedly knows all about Lexus vehicles) because they would say they can't "possibly" diagnose the car due to the modifications.
-I cant's bring it to a local shop because they may not know how to fix this particular issue due to my mods.
This is the annoyance of modding because if an issue should arise it is hard to decipher which mod is causing the problem.
06-02-09, 01:58 PM
#20
I would PM other PI converter owners and ask them to test their RPM at shift points. It may be a common instance when running the converter and or converter 3.769 gearing combo. It may not be anything worth worrying about. BTW, have you been to a track or done any measured runs, 0-60 and or 1/4 mile?
Also, it wouldn't even be fun because I NEED wider, stickier rears for traction in order to obtain proper figures of the car's performance. I contacted Derrick from D2 Autosport and I am looking into the Forgestar F05's (19X8.5 front / 19X10 rear) w/Toyo Proxes T1R's (275's in the rear). Those wheels are only 22.5lbs each!
A net savings of 7lbs per corner from my old (now sold) cast aluminum 19's.
I will try to PM a couple of members with my setup as you suggested. Thanks.
06-02-09, 07:59 PM
#21
Thanks for the response. So, how can I tell if the TC is staying locked all the time? If it is staying locked at all times is this a malfunction with this part?
Regarding the tranny ECU...wouldn't I get a different CEL code for that? I always check (and just checked this morning) my tranny fluid, it's bright pink (like I just changed it yesterday) and at the full line when hot (after driving for 20 minutes).
The reason why am mentioning this is because if the tranny ECU was the culprit and making my car shift erratically wouldn't it burn up my tranny fluid and brown it? The fluid seems to be fine especially since I havn't changed it in 2 years. Amsoil synthetic ATF FTW!!!
Regarding the tranny ECU...wouldn't I get a different CEL code for that? I always check (and just checked this morning) my tranny fluid, it's bright pink (like I just changed it yesterday) and at the full line when hot (after driving for 20 minutes).
The reason why am mentioning this is because if the tranny ECU was the culprit and making my car shift erratically wouldn't it burn up my tranny fluid and brown it? The fluid seems to be fine especially since I havn't changed it in 2 years. Amsoil synthetic ATF FTW!!!
a. not locking at all
b. locked all the time
your Trans Ecu could be bad in a way and you might not be getting a CEL, you wont always get a CEL if something is wrong, i have seen cars run missing 2 cylenders and cel wont come on.
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