Tuning transmission for Drag Racing
- Thread starter SubClot
- 45 comments
- 43,654 views
- 195
- itstheDRE4M
Make sure when you shift that your RPMS drop to where your MAX TORQUE is.
- 9,303
- Norwich,Norfolk
- GTP_DaxCobra
This. 👍
Say your max Tourque is 3k revs, make sure when you change gears you are always in the power band.
veyron1001
(Banned)
- 343
The one that makes the tires spin less.
- 318
- curtis_boy
1/4 mile, 2/4 mile, whole mile what you looking for?
- 45
- SicKmcNasTy
don't listen to people talking about max torque... engine torque is a pointless value, don't even get me started on this topic... you wanna keep your car within your POWER band... as a general rule of thumb, 85% of your peak power should be the point you're at when you shift, and you should be shifting anywhere from 400-600rpm after peak hp, this is where your car will be pulling hardest (relative to its speed and subsequent drag) because, since WHEEL torque is what matters (this takes into effect your trans gear ratios, final gear ratio, and tire size) you produce peak wheel torque just past max hp, unfortunately in this game they don't tell you where max wheel torque takes place, but trust me when i say its AFTER max hp... if your max hp is at 7000rpm and you're making 600hp, and lets say you're making 510hp 6200rpm, that means you wanna keep your gearing between a range of 6100/6200 and 7400 rpm
- 1,155
- artic_zap
Wrong! It's impossible to produce peak torque after peak horsepower. Horsepower is a direct calculation from torque. Torque and horsepower also always cross at 5252 RPM.
And the game does tell you where peak torque is. It's in the settings menu.
- 45
- SicKmcNasTy
Wrong! It's impossible to produce peak torque after peak horsepower. Horsepower is a direct calculation from torque. Torque and horsepower also always cross at 5252 RPM.
And the game does tell you where peak torque is. It's in the settings menu.
you're another victim of that simple misunderstanding, and like i said, engine torque means absolutely nothing, i'm talking WHEEL TORQUE, not engine torque, two completely different concepts... you need absolutely no torque to produce hp... look at jet engines for example... 0 ft lbs of torque, yet thousands of hp... steam engines are the complete opposite end of the spectrum, millions of ft lbs of torque, yet only ~5-10hp... which one is faster? and which one gets more work done? remember... work is measured in POWER... torque doesn't do anything what-so-ever, you can have 10,000 ft lbs of torque and yet not move an inch... but if you have even just 1hp, you're moving and doing work
- 864
- NorCal
- oppositelock27
Yeah, that's not true. Even if it was, some cars have peak torque under 2000 rpm. I wish GT showed wheel torque per gear like this:
This shows the exact accelerative force being applied through the tires. With this we could set gear ratios as well as shift points perfectly. Otherwise, there is no "rule of thumb" to resort to.
- 864
- NorCal
- oppositelock27
You're thinking of corrected chassis dyno numbers, which try to calculate actual engine output. I'm talking about the total force at the tires after the engine torque is multiplied by the individual transmission ratios and final drive ratio. This information is much more useful for choosing gear ratios.
- 23,800
- Philippines
Maximum torque is meaningless. Many turbocharged cars make maximum torque at under 1500 rpms, but you don't want your shifts to take you that low... because you lose gear multiplication on each upshift. You want to hold on to the lower ratio as long as possible, and as long as your wheel torque (as mentioned) is higher than your wheel torque would be in the next gear higher.
You want your car to be producing the most average horsepower in each gear, regardless of where peak torque and peak horsepower are.
Generally, for drag-racing, you want to lengthen first gear enough so that you minimize both wheelspin and bog on the launch. Having first gear stretch to around 80 km/h is sufficient in many cases, depending on your tires. Then space the gears afterwards so that you get a nice, tight spread. But if your setup has a distinct pause between shifts, you may want to go for a spread that's a bit wider.
You want your car to be producing the most average horsepower in each gear, regardless of where peak torque and peak horsepower are.
Generally, for drag-racing, you want to lengthen first gear enough so that you minimize both wheelspin and bog on the launch. Having first gear stretch to around 80 km/h is sufficient in many cases, depending on your tires. Then space the gears afterwards so that you get a nice, tight spread. But if your setup has a distinct pause between shifts, you may want to go for a spread that's a bit wider.
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- 1,155
- artic_zap
Even then, torque and horsepower go up as gears get taller. Its physics.
- 864
- NorCal
- oppositelock27
- 23,800
- Philippines
Are you saying hp goes up in higher gears? As in... you get more hp in 5th than 4th?
If so, that's merely an artifact of the dyno itself... not hp. Longer gears allow for more time for boost to build on the dyno, which results in a higher number... but this is an artificial reading.
On the street, where there's naturally more resistance for the engine to work against, it'll still/always pull harder in the lower gear... unless the engine is torque-limited for safety reasons... and even then, the car will still accelerate faster where it's generating more wheel torque, which is usually in a lower gear.
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You have to understand what a dyno does. It simulates resistance at the wheels for the engine to push against. Not enough, and the engine will never need to generate full power to spin up the roller or push against the dyno brake... and will not often generate full power, thus.
And then we take the fact that the dyno actually measures wheel torque, then uses an algorithm to translate that into what it thinks torque at the transmission is... difficult when the dyno doesn't actually know what gear you're in, and assumes that you are in a gear that gives an approximately 1:1 ratio between the engine and the road.
Dynos can tell you lots of things, but you have to understand what it's telling you and how that relates to the real world.
If so, that's merely an artifact of the dyno itself... not hp. Longer gears allow for more time for boost to build on the dyno, which results in a higher number... but this is an artificial reading.
On the street, where there's naturally more resistance for the engine to work against, it'll still/always pull harder in the lower gear... unless the engine is torque-limited for safety reasons... and even then, the car will still accelerate faster where it's generating more wheel torque, which is usually in a lower gear.
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You have to understand what a dyno does. It simulates resistance at the wheels for the engine to push against. Not enough, and the engine will never need to generate full power to spin up the roller or push against the dyno brake... and will not often generate full power, thus.
And then we take the fact that the dyno actually measures wheel torque, then uses an algorithm to translate that into what it thinks torque at the transmission is... difficult when the dyno doesn't actually know what gear you're in, and assumes that you are in a gear that gives an approximately 1:1 ratio between the engine and the road.
Dynos can tell you lots of things, but you have to understand what it's telling you and how that relates to the real world.
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- 448
Just to reiterate the chart that oppositelock posted, this is a graph of torque, after gearing multiplication, by an Integra Type-R for all 5 gears and with different final drive ratios. Not only can you see the torque decrease with each gear, but you can see the shorter final drive ratio gives higher torque (at the expense of top speed):
- 23,800
- Philippines
Good luck getting your 500 hp sportscar to outdrag a 200 hp Civic from a dead stop while locked in 4th gear.
I suppose you've never ridden an 18/21/1,000,000 speed bike? Which gear is it easiest to accelerate from a dead stop in?
The lowest gear gives you the most power. To the point that you can't even dyno many supercars in lower gears as you will destroy the dyno.
- 45
- SicKmcNasTy
good to see some other experienced posters here 
most forums noone can figure out what i'm talking about and, like i did earlier, i have to dumb it down significantly... some of you guys seem to know what you're talking about and i like seeing that! max WHEEL torque is what matters, hp actually matters, engine torque means nothing at all... once everyone comes to this realization there won't be any of these questions about how to tune transmissions! keep the knowledge flowing!
most forums noone can figure out what i'm talking about and, like i did earlier, i have to dumb it down significantly... some of you guys seem to know what you're talking about and i like seeing that! max WHEEL torque is what matters, hp actually matters, engine torque means nothing at all... once everyone comes to this realization there won't be any of these questions about how to tune transmissions! keep the knowledge flowing!
- 448
Okay, quick lesson:
Absolute Gear Ratio = Gear Ratio * Final Drive Ratio
Absolute Gear Ratio x Engine Torque = Torque to the Ground
The higher the final drive ratio (0.700 > 0.500) for identical gearing, the higher the absolute ratio. The higher the absolute ratio, the more torque is put to the ground.
The more torque put to the ground, the faster/harder you'll accelerate. This is how gearing and torque multiplication works.
has anyone messed with tuning a car for the tunnel using only 5 gears?
i ran into one guy in a zr1 and he said he stretched out the gears to where he only uses 5 gears for the tunnel. tops out around 240, tunnel end to end
i tried it the the final gear ratio had to be in the 2.2xx range
i ran into one guy in a zr1 and he said he stretched out the gears to where he only uses 5 gears for the tunnel. tops out around 240, tunnel end to end
i tried it the the final gear ratio had to be in the 2.2xx range
- 448
I suspect if you took two identical cars, with one using all gears (albeit shorter gearing) and one just using five gears, the shorter geared car would win.
In certain circumstances in drag racing (depending on the finish line) having slightly longer gearing can be better. If I was driving a car in a 1/4 mile drag race and I had to shift into 3rd right before the finish, I'd be better off probably having marginally longer gearing to allow me to hold onto 2nd gear through the finish to save that shift time.
Some manufacturers will give cars gearing specifically to get to 60mph/100kph in as few shifts as possible to maximize testing times (just to look good compared to competitors), even if this isn't ideal.
For this though, where you're at 200+ MPH, you want the gearing to just be optimized. Ignoring a gear isn't optimizing it.
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