I did 3rd gear pulls only because I had a Stock B14 ECU with a speed limiter that I would have hit in 4th gear. I would say dyno 4th.
Going to the Dyno....
I'm going to the dyno next week..I was wondering what is the difference from a 4th gear pull or 3rd gear pull? Last time I did all 3 of my pulls on 3rd gear..any advantage in 4th gear? Thanks
Manny
Manny
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I have BB ECU...I hit my limiter right at 7500 RPM
Manny
Manny
Its usually 3rd NA 4th forced induction.
SE-Rawkus said:I have BB ECU...I hit my limiter right at 7500 RPM
Manny
I believe he is talking about the actual govener of the speed.
I know. I hit my speed limiter at the end of 4th gear. I have a BB ECUdjmayhem said:I believe he is talking about the actual govener of the speed.
Manny
NA or turbo makes no difference. You use 4th gear because it is the closest to a 1:1 gear ratio. 3rd gives you a 1.286:1 ratio where 4th provides a .975:1 ratio. This is for an NX/SE-R, the G20 gears are different, but 4th still provides the closest to 1:1.nizzan4u2nv said:Its usually 3rd NA 4th forced induction.
Okay...4th is the closest to a 1:1 gear ratio....but what is the advantage (if there is any) of using a 4th gear pull over a 3rd gear pull? In other words, why haveing a 1:1 gear ratio ideal for the best pull possible?myprojectB13 said:NA or turbo makes no difference. You use 4th gear because it is the closest to a 1:1 gear ratio. 3rd gives you a 1.286:1 ratio where 4th provides a .975:1 ratio. This is for an NX/SE-R, the G20 gears are different, but 4th still provides the closest to 1:1.
Manny
You are lucky if you are hitting the speed cut at the end of 4th gear, cause with my GTIR ECU i hit the speed cut way before redline. 4th gear ends around 120 or so, I hit the speed cut at about 6200 rpms give or take a few 100 rpms.
Not lucky at all...When I hit my limiter, I'm at 120 mph in 4th gear @ 7400 (give or take 100 rpm's).RUTH'LESS NX2K said:You are lucky if you are hitting the speed cut at the end of 4th gear, cause with my GTIR ECU i hit the speed cut way before redline. 4th gear ends around 120 or so, I hit the speed cut at about 6200 rpms give or take a few 100 rpms.
Manny
Ok so then your ecu doesn't have a speed cut then, cause mines cuts out b4 120 mph. But thats a good thing though you can do that dyno pull and not worry about anything!
Well actually...after 120 MPH I can't go into 5th because my ECU won't let me go no-more. So I guess I do have a speed limiter; all BB ECU have speed limiters.RUTH'LESS NX2K said:Ok so then your ecu doesn't have a speed cut then, cause mines cuts out b4 120 mph. But thats a good thing though you can do that dyno pull and not worry about anything!
Manny
eah tell me about it I done hit the speed limiter so many times its crazy!
the reason why you dyno in 4th instead of 1st,2nd,or 3rd is cause with boost the engine has more torque so it will rev-out a lot faster. By dynoing in 4th there is a larger load on the engine so when you start at say 3,000rpm the engine is loaded up more so you may show peak boost hitting at say 4,00rpm. When you dyno in 2nd or 3rd and start at 3,000 the engine will rev-out faster and will show peak boost (or where the curve levels off a little) to gbe higher up, say 4,500-5,000 rpm. Also by using a higher gear it is a more acurate measurement because it can record more data points for every second. Because HP is a factor of torque over RPM your HP won't change from 1st gear to 4th gear. 1st gear has more wheel torque but it is also turning at a lower speed RPM. 4th gear has less wheel torque but has a higher speed (RPM).
Thank you..I have a better understanding now. I will do my 1st pull in third gear and then do my last 2 pulls in 4th gear and compare dyno graphs.SR20Turbofreak said:the reason why you dyno in 4th instead of 1st,2nd,or 3rd is cause with boost the engine has more torque so it will rev-out a lot faster. By dynoing in 4th there is a larger load on the engine so when you start at say 3,000rpm the engine is loaded up more so you may show peak boost hitting at say 4,00rpm. When you dyno in 2nd or 3rd and start at 3,000 the engine will rev-out faster and will show peak boost (or where the curve levels off a little) to gbe higher up, say 4,500-5,000 rpm. Also by using a higher gear it is a more acurate measurement because it can record more data points for every second. Because HP is a factor of torque over RPM your HP won't change from 1st gear to 4th gear. 1st gear has more wheel torque but it is also turning at a lower speed RPM. 4th gear has less wheel torque but has a higher speed (RPM).
Manny
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