Have some real technical HP/Torque questions. Confused lol.
#1
Have some real technical HP/Torque questions. Confused lol.
Ok I pretty much thought I had a decent understand of HP and torque. Today I deceided to do some browsing and came across this site that gives you the equation to figure out hp and tq etc.
It says that torque = hp x 5252 / rpm and hp = torque x rpm/5252.
I was just pluggin in some numbers and some things just werent adding up to me. On the window sticker of my G it says 306hp@6800 and 268tq@4800.
If you do the equation on the site. 306x5252/6800 you get 236 lb/ft of torque. I dont quite understand this fully yet as its late and im pretty tired from work. If the G is supposidly only putting out 236 lb/ft at 6800 rpm then wouldnt you actually want to shift slightly before that?
Another thing that im curious about is take a car like say the honda s2000 which is 242 hp @ 7200. If you plug those numbers into the formula above it actually says that it produces 162 lb.ft of torque which if im not mistake is exactly what honda says, so why is the G so far off then?
My main reason for checking out this site was trying to figure out shift points and actually how to increase torque without F/I. I always just bring my car to redline if i wanted to acheive the fastest acceleration, but it seems like after reading this, thats not the case. If seems to me that by going off these calculations that higher in rpms you go past peek, the more the torque drops off, therefore hurting acceleration times. Am I wrong?
People with real knowledge on this subject please respond.
It says that torque = hp x 5252 / rpm and hp = torque x rpm/5252.
I was just pluggin in some numbers and some things just werent adding up to me. On the window sticker of my G it says 306hp@6800 and 268tq@4800.
If you do the equation on the site. 306x5252/6800 you get 236 lb/ft of torque. I dont quite understand this fully yet as its late and im pretty tired from work. If the G is supposidly only putting out 236 lb/ft at 6800 rpm then wouldnt you actually want to shift slightly before that?
Another thing that im curious about is take a car like say the honda s2000 which is 242 hp @ 7200. If you plug those numbers into the formula above it actually says that it produces 162 lb.ft of torque which if im not mistake is exactly what honda says, so why is the G so far off then?
My main reason for checking out this site was trying to figure out shift points and actually how to increase torque without F/I. I always just bring my car to redline if i wanted to acheive the fastest acceleration, but it seems like after reading this, thats not the case. If seems to me that by going off these calculations that higher in rpms you go past peek, the more the torque drops off, therefore hurting acceleration times. Am I wrong?
People with real knowledge on this subject please respond.
Last edited by logik05se; 07-08-2007 at 12:13 AM.
#2
I would think you want to drive through the peak torque to a certain point, then shift down to where you are at or near your peak torque, so shifting at 6800 RPM or greater the next gear you are back near peak torque.
The best way I've done this is just by repeated driving and feeling where the car stops pulling as hard, then shift at that point. Typically it just before (500 - 1000) rpm before redline. But then again I've only driven turbocharged 4cyl, until Last Tuesday.
The best way I've done this is just by repeated driving and feeling where the car stops pulling as hard, then shift at that point. Typically it just before (500 - 1000) rpm before redline. But then again I've only driven turbocharged 4cyl, until Last Tuesday.
#3
Originally Posted by logik05se
It says that ... hp = torque x rpm/5252.
... On the window sticker of my G it says 306hp@6800 and 268tq@4800.
... 306x5252/6800 you get 236 lb/ft of torque.
... 306x5252/6800 you get 236 lb/ft of torque.
... If the G is supposidly only putting out 236 lb/ft at 6800 rpm then wouldnt you actually want to shift slightly before that?
Another thing that im curious about is take a car like say the honda s2000 which is 242 hp @ 7200. If you plug those numbers into the formula above it actually says that it produces 162 lb.ft of torque which if im not mistake is exactly what honda says, so why is the G so far off then?
My main reason for checking out this site was trying to figure out shift points and actually how to increase torque without F/I. I always just bring my car to redline if i wanted to acheive the fastest acceleration, but it seems like after reading this, thats not the case...
#4
#5
Originally Posted by Jspeed
Again, it's the torque at the wheels that matters, and you must take gear ratios into consideration. You should upshift when the torque at the wheels is higher for the next gear than the current gear. To calculate this, you'd need the torque curve of the engine and all the gear ratios. In most cases, revving to redline yields the most torque to the ground.
Originally Posted by trey.hutcheson
Shifting before redline on the HR drops you to lower wtq in the next gear than the current gear, at least for the first 3 shifts(that's all that I've calculated).
I guess all these numbers are basicly useless though unless I do a dyno (or just read someone elses on the HR) and see exactly where the curve is.
#6
#7
Here is a story with an unrelated car- but it is related to the topic-
I used to have a 90 Mustang GT- 225hp 300tq from the factory- 5500 RPM redline-
If I shifted at redline, the car ran 14.7s- if I shifted at 4250-4500RPM the care ran 14.2s and 14.3s-
so just because there is a redline, does not mean that is always the best place to shift
I used to have a 90 Mustang GT- 225hp 300tq from the factory- 5500 RPM redline-
If I shifted at redline, the car ran 14.7s- if I shifted at 4250-4500RPM the care ran 14.2s and 14.3s-
so just because there is a redline, does not mean that is always the best place to shift
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#8
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1) Looking at VQ35HR dynos, the optimal shift point for our car is DEFINITELY at redline.
2) It doesn't matter that you are making what seems to be not enough torque, as long as you are making it at high RPMs. Say I had an F1 like-tranny and was making 150tq@15000rpms, that would mean at that point I would have ~430hp. As long as you can make decent torque through out the entire RPM band, you'll have low end and high end power.
2) It doesn't matter that you are making what seems to be not enough torque, as long as you are making it at high RPMs. Say I had an F1 like-tranny and was making 150tq@15000rpms, that would mean at that point I would have ~430hp. As long as you can make decent torque through out the entire RPM band, you'll have low end and high end power.
#9
Originally Posted by CalsonicVQ
1) Looking at VQ35HR dynos, the optimal shift point for our car is DEFINITELY at redline.
2) It doesn't matter that you are making what seems to be not enough torque, as long as you are making it at high RPMs. Say I had an F1 like-tranny and was making 150tq@15000rpms, that would mean at that point I would have ~430hp. As long as you can make decent torque through out the entire RPM band, you'll have low end and high end power.
2) It doesn't matter that you are making what seems to be not enough torque, as long as you are making it at high RPMs. Say I had an F1 like-tranny and was making 150tq@15000rpms, that would mean at that point I would have ~430hp. As long as you can make decent torque through out the entire RPM band, you'll have low end and high end power.
#10
Originally Posted by logik05se
by reading the dynos i was thinking about 6300-6900 was about rite...ill have to look again.
Point of shifting is to shift into the next gear at the highest possible torque, which is why you want to shift at 7500 on the HR's.
Same goes for the Revup
The HP vs Torque debate is never an easy subject unless you really understand physics.
.
#11
Originally Posted by skaterbasist
Shifting too early, which 6300-6900 definately is way too early, will bring you down to a lower torque curve after your shift. Shifting too late will also bring you down to a lower torque point at the next shift.
Point of shifting is to shift into the next gear at the highest possible torque, which is why you want to shift at 7500 on the HR's.
Same goes for the Revup
The HP vs Torque debate is never an easy subject unless you really understand physics.
.
Point of shifting is to shift into the next gear at the highest possible torque, which is why you want to shift at 7500 on the HR's.
Same goes for the Revup
The HP vs Torque debate is never an easy subject unless you really understand physics.
.
#12
#13
in DS mode, it goes out to 7500 in every gear. i only get to 3rd gear, and i don't remember what rpm i'm at, but it's a consistent 98mph at the end of the 1/4.
i've tried shifting myself at different points, and not taking it to redline or damn close (7200-7500rpm) will slow you down slightly. when i shifted at redline like the DS mode, my times were the same.
i've tried shifting myself at different points, and not taking it to redline or damn close (7200-7500rpm) will slow you down slightly. when i shifted at redline like the DS mode, my times were the same.
#15
Originally Posted by spacecowboy
in DS mode, it goes out to 7500 in every gear. i only get to 3rd gear, and i don't remember what rpm i'm at, but it's a consistent 98mph at the end of the 1/4.
i've tried shifting myself at different points, and not taking it to redline or damn close (7200-7500rpm) will slow you down slightly. when i shifted at redline like the DS mode, my times were the same.
i've tried shifting myself at different points, and not taking it to redline or damn close (7200-7500rpm) will slow you down slightly. when i shifted at redline like the DS mode, my times were the same.