Will a 95 transmission be compatible with a 90Q???
I can tell you for certain what sticking a 94-95 TCU into a 90-93 car in about 3 weeks after my new transmission has about 750 miles on the break-in period.
From what Q45tech says....that it would more your redline up to around 7,400 from 6,900. It appears that it will act almost exactly like a JWT TCU that you pay $450. The problem with moving the redline up is that the OEM ECU cuts off the gas to the engine at 6,900 rpms unless you have a JWT ECU which cuts off the gas around 7,400 rpms.
Just hang around for another month and I will be able to tell you exactly what it does. I am putting in a 92 transmission into my 95 car and I have both TCU' s (93 & 95). I will run each one to see how my car reacts and then post the results. I know that there is somebody else here with both Q's (91 & 94??) and they could do this test as well by just swapping out the TCU's to see what happens.
From what Q45tech says....that it would more your redline up to around 7,400 from 6,900. It appears that it will act almost exactly like a JWT TCU that you pay $450. The problem with moving the redline up is that the OEM ECU cuts off the gas to the engine at 6,900 rpms unless you have a JWT ECU which cuts off the gas around 7,400 rpms.
Just hang around for another month and I will be able to tell you exactly what it does. I am putting in a 92 transmission into my 95 car and I have both TCU' s (93 & 95). I will run each one to see how my car reacts and then post the results. I know that there is somebody else here with both Q's (91 & 94??) and they could do this test as well by just swapping out the TCU's to see what happens.
Well here I am following up on my word to tell you all how a 94-95 TCU works with a 90-93 transmission. It works fine...no problems at all from what I can tell. I have had it in my car for the past 3 days and no problems. I have first gear start and all transmission shifts are fine.
Speaking of transmission shifts, the redline did not change at all???? I must have done at least 15 1st-2nd gear shifts and the redline was right at 6,900 every time. I thought that the redline would have moved up to about 7,400 rpms as per Q45tech. It did not and I tried it with both the JWT ECU & OEM ECU. No difference at all. I also checked several times the 2nd-3rd shifts...no difference either. Seriously...I tried so many times these redline shifts that my car is even tired of redlining and my gas mileage must be around 10mpg.
I am now thinking that there must be a fail safe mechanism in the TCU to shift at 6,900 rpms regardless of gearing and the reprogramed JWT TCU's have this fail safe removed. I guess I am going to have to buy the JWT TCU afterall. At least I already have two TCU's.
Maybe if somebody else with a 90-92 transmission with TCS and has access to a 94-95 TCU can verify that running a 94-95 TCU gives you first gear start and does not move the redline up.
Speaking of transmission shifts, the redline did not change at all???? I must have done at least 15 1st-2nd gear shifts and the redline was right at 6,900 every time. I thought that the redline would have moved up to about 7,400 rpms as per Q45tech. It did not and I tried it with both the JWT ECU & OEM ECU. No difference at all. I also checked several times the 2nd-3rd shifts...no difference either. Seriously...I tried so many times these redline shifts that my car is even tired of redlining and my gas mileage must be around 10mpg.
I am now thinking that there must be a fail safe mechanism in the TCU to shift at 6,900 rpms regardless of gearing and the reprogramed JWT TCU's have this fail safe removed. I guess I am going to have to buy the JWT TCU afterall. At least I already have two TCU's.
Maybe if somebody else with a 90-92 transmission with TCS and has access to a 94-95 TCU can verify that running a 94-95 TCU gives you first gear start and does not move the redline up.
Wes....please understand that I am doing this test with my "JWT ECU" and not my "OEM ECU" so I should be shifting well within the redline, but I can't get the rpm needle into the redline zone. The shifts are still at 6,900rpms. I tested the JWT vs. OEM redline limit by reving the engine while in park past 6,900 rpms and the OEM does cut off the fuel at 6,900rpms while the JWT cuts off fuel at 7,200rpms and I also tried this by holding the transmission in 1st gear and pushing it beyond redline.
The JWT ECU is good. I only really feel the JWT above 3,500rpms and the engine sounds a little meaner (stronger). I really notice a difference near 6,900. I now see the need to get a JWT TCU to run up to 7,200rpms.
I will be doing some 1/4 runs tonight at the track with & without the JWT ECU to see how the 1/4 times are reduced.
I will be keeping my 95 TCU and sending it to JWT to get it reprogramed so it is not for sale. I will have a 93 OEM TCU and a JWT TCU to play with.
The JWT ECU is good. I only really feel the JWT above 3,500rpms and the engine sounds a little meaner (stronger). I really notice a difference near 6,900. I now see the need to get a JWT TCU to run up to 7,200rpms.
I will be doing some 1/4 runs tonight at the track with & without the JWT ECU to see how the 1/4 times are reduced.
I will be keeping my 95 TCU and sending it to JWT to get it reprogramed so it is not for sale. I will have a 93 OEM TCU and a JWT TCU to play with.
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Q45tech
- Moderator
- Posts: 14296
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
The JWT ecu doesn't change anything below 3,000 rpm or anything at less than 80% WOT. Even the tip in acceleration retard.
You are correct it really leans the extra richness [to cool cylinders which lowers power] above 6,000 to fuel cutoff. This is where you feel it most.
Why do you think you can trust the tachometer to better than 4-5% accuracy?
You are correct it really leans the extra richness [to cool cylinders which lowers power] above 6,000 to fuel cutoff. This is where you feel it most.
Why do you think you can trust the tachometer to better than 4-5% accuracy?
Thanks for your response Q45tech.
I really appreciate your confirmation about feeling the JWT only in the higher rpms (3,000+).
I thought that you would comment on the tach's accuracy...I just would have thought that I would be able to see some type of difference...at least see the needle go beyond 6,900rpms.
I really appreciate your confirmation about feeling the JWT only in the higher rpms (3,000+).
I thought that you would comment on the tach's accuracy...I just would have thought that I would be able to see some type of difference...at least see the needle go beyond 6,900rpms.
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Q45tech
- Moderator
- Posts: 14296
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
The transmission shifts by PRIMARILY speed sensor reading, has little to do with engine rpm.........although revs are monitored as a back up to speed sensor [rev sensor and turbine output shaft speed sensor] but they are less accurate than the ENGINE crank angle sensor which divides an rpm into 360 tiny parts vs their one pulse per revolution.
Engine rpm signal is not sent to TCU. Although from its own sensors it has a good idea but not the computer power to resolve say a 100 rpm difference........everything is focused on speed output shaft sensor............see graphs in FSM.
Engine rpm signal is not sent to TCU. Although from its own sensors it has a good idea but not the computer power to resolve say a 100 rpm difference........everything is focused on speed output shaft sensor............see graphs in FSM.
sorry guys...but it rained when I got to the track and they closed the track. It is the rainy season and so we get frequent quick late afternoon rain showers and after driving 70miles north to the track that sucked to find out it had just rained and they closed the track. I had to send back the OEM ECU today to avoid the core charge so I will not be able to do a difference 1/4 test. Car is in the shop getting a few things (mods) done to it for the next two weeks while I travel so the next time I do the 1/4 runs...my numbers should be a lot different and I will not be able to identify the improvements mod by mod.
As you all know, I have a 1990 Transmission in my 1994 Q45. Both the OEM TCU and the JWT trimode operate the transmission fine. I am just playing around with which TCU I like for gerneral driving and if I need the higher shifts with a boosted set up.
I have experianced no glitches with the ECU, even with a lower rev limiter setting to prevent overdriving the Centrifugal Supercharger.
Which TCU I stay with will be a final choice on my driving style.
All things going well, I am on the home stretch and will finally finish this car. Fingers crossed!
Regards
AGM
I have experianced no glitches with the ECU, even with a lower rev limiter setting to prevent overdriving the Centrifugal Supercharger.
Which TCU I stay with will be a final choice on my driving style.
All things going well, I am on the home stretch and will finally finish this car. Fingers crossed!
Regards
AGM
Congrats AGM....I am following very close behind in your footsteps but for now I am just building a NA Q45....trying to hold off on the SC, Turbo, NOS, etc.
I also will be testing the JWT TCU vs the OEM 93 TCU to see which one I like better.
AGM....you must have received the very last JWT Trimode TCU, very good timing if I must say so.
I also will be testing the JWT TCU vs the OEM 93 TCU to see which one I like better.
AGM....you must have received the very last JWT Trimode TCU, very good timing if I must say so.