Analyzing Best Shift Poitnts based on HP/TQ Curves
Analyzing Best Shift Poitnts based on HP/TQ Curves
If I had a hp/tq curve plot from a dyno for each of my 5 gears, would it be possible for me to figure out where the best shift points are for maximum acceleration? Or would the info on gear ratios need to be factored in somehow? I figure each Max that's got slightly different power related mods will have a slightly different hp/tq curve which affects where the optimal shifts points are.
Any good analysis on this by anyone? Thx in advance.
Any good analysis on this by anyone? Thx in advance.
Re: Analyzing Best Shift Poitnts based on HP/TQ Curves
Originally posted by StygianMax
If I had a hp/tq curve plot from a dyno for each of my 5 gears, would it be possible for me to figure out where the best shift points are for maximum acceleration? Or would the info on gear ratios need to be factored in somehow? I figure each Max that's got slightly different power related mods will have a slightly different hp/tq curve which affects where the optimal shifts points are.
Any good analysis on this by anyone? Thx in advance.
If I had a hp/tq curve plot from a dyno for each of my 5 gears, would it be possible for me to figure out where the best shift points are for maximum acceleration? Or would the info on gear ratios need to be factored in somehow? I figure each Max that's got slightly different power related mods will have a slightly different hp/tq curve which affects where the optimal shifts points are.
Any good analysis on this by anyone? Thx in advance.
You will be making the same power in every gear so you will only need one dyno plot. And yes, you need to take the gear ratios into account.
Re: Re: Analyzing Best Shift Poitnts based on HP/TQ Curves
Originally posted by Nealoc187
You will be making the same power in every gear so you will only need one dyno plot. And yes, you need to take the gear ratios into account.
You will be making the same power in every gear so you will only need one dyno plot. And yes, you need to take the gear ratios into account.
Supporting Maxima.org Member
Joined: Aug 2001
Posts: 1,362
The generally agreed on optimum shift points are...
1-2 6500
2-3 6200
3-4 6000
I belive these were worked out by Dave B. They take into account the fact that the power drops off sharply after 6000 RPM but it is still fastest to go past 6000 RPM in the lower gears to enter the next gear higher in the power band. There are a couple of good threads discussing this including...
http://forums.maxima.org/showthread....hreadid=125797
http://forums.maxima.org/showthread....threadid=72017
http://forums.maxima.org/showthread....threadid=28571
I don't think any NA mods alter the power curve enough to change the shift points... except for the VI of course.
I have my own shift points I like to use, for example when racing a -
Civic - 3500 RPM
V6 Mustang - 4000 RPM
Z-24 Cavalier - 4500 RPM
V6 Accord - 5000 RPM
5.0 Mustang - Use optimum, turn off A/C if it's a 5 speed
1-2 6500
2-3 6200
3-4 6000
I belive these were worked out by Dave B. They take into account the fact that the power drops off sharply after 6000 RPM but it is still fastest to go past 6000 RPM in the lower gears to enter the next gear higher in the power band. There are a couple of good threads discussing this including...
http://forums.maxima.org/showthread....hreadid=125797
http://forums.maxima.org/showthread....threadid=72017
http://forums.maxima.org/showthread....threadid=28571
I don't think any NA mods alter the power curve enough to change the shift points... except for the VI of course.
I have my own shift points I like to use, for example when racing a -
Civic - 3500 RPM
V6 Mustang - 4000 RPM
Z-24 Cavalier - 4500 RPM
V6 Accord - 5000 RPM
5.0 Mustang - Use optimum, turn off A/C if it's a 5 speed
Originally posted by Anachronism
The generally agreed on optimum shift points are...
1-2 6500
2-3 6200
3-4 6000
I belive these were worked out by Dave B. They take into account the fact that the power drops off sharply after 6000 RPM but it is still fastest to go past 6000 RPM in the lower gears to enter the next gear higher in the power band. There are a couple of good threads discussing this including...
http://forums.maxima.org/showthread....hreadid=125797
http://forums.maxima.org/showthread....threadid=72017
http://forums.maxima.org/showthread....threadid=28571
I don't think any NA mods alter the power curve enough to change the shift points... except for the VI of course.
I have my own shift points I like to use, for example when racing a -
Civic - 3500 RPM
V6 Mustang - 4000 RPM
Z-24 Cavalier - 4500 RPM
V6 Accord - 5000 RPM
5.0 Mustang - Use optimum, turn off A/C if it's a 5 speed
The generally agreed on optimum shift points are...
1-2 6500
2-3 6200
3-4 6000
I belive these were worked out by Dave B. They take into account the fact that the power drops off sharply after 6000 RPM but it is still fastest to go past 6000 RPM in the lower gears to enter the next gear higher in the power band. There are a couple of good threads discussing this including...
http://forums.maxima.org/showthread....hreadid=125797
http://forums.maxima.org/showthread....threadid=72017
http://forums.maxima.org/showthread....threadid=28571
I don't think any NA mods alter the power curve enough to change the shift points... except for the VI of course.
I have my own shift points I like to use, for example when racing a -
Civic - 3500 RPM
V6 Mustang - 4000 RPM
Z-24 Cavalier - 4500 RPM
V6 Accord - 5000 RPM
5.0 Mustang - Use optimum, turn off A/C if it's a 5 speed
Thanks for all that info & links. One further question. I've heard from someone that works at a dyno shop that the displayed rpm reading on the tach can differ quite a bit from true rpm at the crank. Does that have any impact on your shift points listed above, like +/- 200rpm (or whatever the typical variation for a Maxima VQ engine may be)?
Supporting Maxima.org Member
Joined: Aug 2001
Posts: 1,362
Originally posted by StygianMax
Wow! Thanks for all that info & links. One further question. I've heard from someone that works at a dyno shop that the displayed rpm reading on the tach can differ quite a bit from true rpm at the crank. Does that have any impact on your shift points listed above, like +/- 200rpm (or whatever the typical variation for a Maxima VQ engine may be)?
Wow!
Thanks for all that info & links. One further question. I've heard from someone that works at a dyno shop that the displayed rpm reading on the tach can differ quite a bit from true rpm at the crank. Does that have any impact on your shift points listed above, like +/- 200rpm (or whatever the typical variation for a Maxima VQ engine may be)?
Originally posted by Dave B
Yesterday at the track I decided to shift to 4th because I had what I thought was a bad launch. When I got my timeslip, it turned out to be my best run to date. For those of you with the typical mods (intake, y-pipe, catback or B-pipe) you may want to try out these shift points. The points have been determined from my dynojet runs. The rpms I list are the rpms "indicated" by the tach (it reads about 300 rpms high).
1-2 6500
2-3 6200
3-4 6000
According to my dyno plot the 4th gen VQ looses power after 5700 rpms in 4th gear and then dramatically falls off after 6000. By staying in 3rd the entire length of the track, you end up laboring in 3rd at near 6500 rpms when you hit the timing boxes. The drag racer rule of thumb is that you want to be crossing the line at hp peak. By shifting to 4th, you are crossing at 5300rpms which is much better than 6500. Why? Because at 5300rpms I'm making 172 fwhp vs 145 fwhp at 6500. Even though it doesn't feel like it, you are still accelerating in 4th.
BTW, shifting to 4th should only be done by those who can shift relatively quickly or else you et and trap speed could possibly be worse. I don't powershift, but I come pretty close (ie rpms never exceed 6500).
Dave
Yesterday at the track I decided to shift to 4th because I had what I thought was a bad launch. When I got my timeslip, it turned out to be my best run to date. For those of you with the typical mods (intake, y-pipe, catback or B-pipe) you may want to try out these shift points. The points have been determined from my dynojet runs. The rpms I list are the rpms "indicated" by the tach (it reads about 300 rpms high).
1-2 6500
2-3 6200
3-4 6000
According to my dyno plot the 4th gen VQ looses power after 5700 rpms in 4th gear and then dramatically falls off after 6000. By staying in 3rd the entire length of the track, you end up laboring in 3rd at near 6500 rpms when you hit the timing boxes. The drag racer rule of thumb is that you want to be crossing the line at hp peak. By shifting to 4th, you are crossing at 5300rpms which is much better than 6500. Why? Because at 5300rpms I'm making 172 fwhp vs 145 fwhp at 6500. Even though it doesn't feel like it, you are still accelerating in 4th.
BTW, shifting to 4th should only be done by those who can shift relatively quickly or else you et and trap speed could possibly be worse. I don't powershift, but I come pretty close (ie rpms never exceed 6500).
Dave
Originally posted by StygianMax
Wow! Thanks for all that info & links. One further question. I've heard from someone that works at a dyno shop that the displayed rpm reading on the tach can differ quite a bit from true rpm at the crank. Does that have any impact on your shift points listed above, like +/- 200rpm (or whatever the typical variation for a Maxima VQ engine may be)?
Wow!
Thanks for all that info & links. One further question. I've heard from someone that works at a dyno shop that the displayed rpm reading on the tach can differ quite a bit from true rpm at the crank. Does that have any impact on your shift points listed above, like +/- 200rpm (or whatever the typical variation for a Maxima VQ engine may be)?
Originally posted by costcowholesale
but the dyno reads off the ecu which is the displayed rpm reading right?? so it'll be the same?
but the dyno reads off the ecu which is the displayed rpm reading right?? so it'll be the same?
Member
Joined: Dec 2000
Posts: 252
Originally posted by StygianMax
Hey D! Remember John at the dyno place (was JRP the name?) Anyway, he said the car's tach rarely ever reads true. It's either a bit high or a bit low. Never bang on. Probably a limitation of the analog mechnical stuff operating the tach vs. a full digital-based tach (just my guess). See Anachronism's post & the italicized portion.
Hey D! Remember John at the dyno place (was JRP the name?) Anyway, he said the car's tach rarely ever reads true. It's either a bit high or a bit low. Never bang on. Probably a limitation of the analog mechnical stuff operating the tach vs. a full digital-based tach (just my guess). See Anachronism's post & the italicized portion.
Floor it in first gear, or second. Don't shift until you hit the fuel starve at 6500 RPM. (the engine wil sputter at 6500, but nothing will be hurt) Look at your tach when this happens.
My tach indicates 6700 RPM, at 6500 RPM
Not DAVEB the parts guy
Joined: Aug 2000
Posts: 8,549
The tach is off by ~300rpms in 1st gear and ~200rpms in 2nd gear, ~100rpms in 3rd, and 4th is pretty close. This was easy to figure out because my shift light and rpm switch are hooked to the ECU rpm signal wire.
1-2 6500
2-3 6200
3-4 6000
You can't go wrong.
Dave
1-2 6500
2-3 6200
3-4 6000
You can't go wrong.
Dave
Senior Member
Joined: Feb 2002
Posts: 808
are you guys sure about the fuel cut off being at 6.5k... in my car as well as kingmax's, the cut off is 7k... in all gears...well, atleast 1,2,3.. maybe 4th. so are the tachs that far off or is it possible that for some reason we are able to run a higher rpm. i guess it really doesn't matter if we can or not, since there is no power there... it just seems odd that both our tachs run to 7k.
Originally posted by Dave B
This was easy to figure out because my shift light and rpm switch are hooked to the ECU rpm signal wire.
This was easy to figure out because my shift light and rpm switch are hooked to the ECU rpm signal wire.
MaxVQ - I'll try out your idea. From a later post in the thread, it seems that some folks have experienced slightly different points at which fuel cuts off. Interesting....
Indicated RPM are different than actual RPM. Dyno's will read off the coil, thus they show actual RPM.
Every piece of evidence I've encountered proves to me that the maxima's tach reads 200 RPM high at redline. Fuel cutoff is at 6550 rpms, and I can rev out to an indicated 6750 rpms, I've tried this with multiple ECUs, both in gear (while moving) and in neutral. Perhaps the automatics have a tach that is a little more off than the 5spd tach.
For your other question, I think the gear ratios are available in the FAQs. But it works like this : 1-2 is the biggest difference, 2-3 next biggest, 3-4 next, 4-5 is the smallest.
Every piece of evidence I've encountered proves to me that the maxima's tach reads 200 RPM high at redline. Fuel cutoff is at 6550 rpms, and I can rev out to an indicated 6750 rpms, I've tried this with multiple ECUs, both in gear (while moving) and in neutral. Perhaps the automatics have a tach that is a little more off than the 5spd tach.
For your other question, I think the gear ratios are available in the FAQs. But it works like this : 1-2 is the biggest difference, 2-3 next biggest, 3-4 next, 4-5 is the smallest.
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