turbo's and tranny gearing - the facts

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S

spectacle

Senior Member
Alright I know its been said and argued TO DEATH that a shorter geared tranny is faster on any givin motor whether its N/A or turbo, but I ran across this article on superstreet.com that says the following:

"Those who are into road racing will want to look into matching their transmissions to their engine setups. You can take advantage of a high-revving B16 motor at a road course by using shorter gears for quicker acceleration and keep a longer Fifth gear for better top speed and gas mileage. In drag racing, a turbocharged B-motor should have a tranny with longer gear ratios, like the ones found on an LS tranny, because of the spool-up time of the turbocharger. It’s not as high- or quick-revving like an all-motor car and needs the longer gears to catch up with. A lightened flywheel will also help the equation, allowing the motor to rev up more quickly."

source: http://www.superstreetonline.com/techarticles/27360/

i am by no means saying that they are right or wrong, i'm just trying to get the facts straight. I've heard arguments that have convinced me on both sides so I'm beginning to think that it depends on how much boost you're running and when does the turbo hit full boost, etc etc but I'm not sure. please post the facts with credible data and reasoning so that anyone who reads this will be clear on the facts.

no childish bickering...and if you don't know, don't post.
 
SuperStreet????????

Prepare for the flaming.....



And an LS tranny is only faster than a GSR tranny if your turbo doesn't spool by redline.....

:slap: :wallbash:
 
Originally posted by spectacle@Oct 21 2004, 06:57 PM
source: http://www.superstreetonline.com/techarticles/27360/

no childish bickering...and if you don't know, don't post.
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This article is so fucking retarded... shorter gears > longer gears.

1. "Honda factory parts are quite stout. The factory connecting rods are good for up to 50 hp over stock, which, if it goes over that mark, should either be shotpeened or swapped out for stronger aftermarket rods."

I agree honda parts are stout, but I guess I should be worried since I am making more than 100whp over stock? I have a d-series also, not b-series. What about these guys with GSR's making like 350whp on stock blocks? That's damn near 200whp over stock!

2. "We know that from the factory, the blocks are very well suited for all-motor racing but are weak when it comes to forced induction.

What the fuck?! Are these guys smoking crack? lol...

3. "Rather than spending a grip of cash building the SOHC, save the money and put it toward a base B16 or B18C motor."

A grip? I can easily build my d16 for less than I could get a b18c swap for, come on now...
 
beerbongskickass said:
spectacle said:
source:
3. "Rather than spending a grip of cash building the SOHC, save the money and put it toward a base B16 or B18C motor."

A grip? I can easily build my d16 for less than I could get a b18c swap for, come on now...
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I think they are getting that a B16 or B18C motor has more power potential than a SOHC. Then, after you swap, you can build the b16 or b18, and get more power out of it than a worked single cam.
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yeah the rational that longer gear ratios give a turbo more time to spool, or whatever they're implying is ridiculous

a shorter gear ratio will ALWAYS let you accelerate quicker. and longer gears will give you a higher top end. period.

the only reason one would need to use longer gears for a turbo car, or for any car, is if, in the case of drag racing, the car was redlining it's top gear before finishing the race-
 
rational :

High end horsepower allows you to take advantage of gear ratios, since Horsepower is basically a measure of how fast your engine can exert it's power. If it can exert it very fast, then it can "keep up" with faster spinning gears (to hold acceleration).


But the bottom line really is that the shorter the gear ratio, the faster the acceleration. Period. It's simple physics.
 
In most cases yes... but it is more complex than that. You do have to take into account spool up time between gear shifts, and you do have to worry about the time it actually takes to shift gears. Assuming that you don't have to worry about the miniscule spool time and delay during gear changes, then yes- shorter gearing is always better.
 
There isn't really any tech involved.

In two cars with identical horsepower, the car with the shorter gear ratio will win because it can spin the gears faster thus creating a higher speed sooner. In order for taller gears to be faster, the shorter gears would have to be so short that your turbo does not have time to create full boost, and shifting gears makes you fall even farther out of boost. In this case, and this case only, a longer tranny would be benifitial because you would build peak boost and in essance, more power.
 
Actually, there is a whole lot of tech involved. I'm just not going to sit here and work through a ton of math and make some handy dandy spreadsheet to show you guys how to select proper gear ratios.

What you basically want is a transmission that will enable you to have the highest force at the wheels for tha maximum amount of time- so fewer gear changes = good, more force multiplication = good. Grab a torque curve and work it out.
 
I think I'm beginning to understand this now...so if you have a smaller turbo that spools pretty quick it would be benefial to have shorter geared tranny opposed to a larger turbo that spools a lot later in the RPM's where the longer geared tranny would keep you in boost longer????
 
Originally posted by Slammed90Lude@Oct 22 2004, 12:20 AM
yeah the rational that longer gear ratios give a turbo more time to spool, or whatever they're implying is ridiculous

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bullshit.

LOAD on a motor and exhaust flow causes a turbo to spool. gearing has nothing to do with it.

the only reason one would need to use longer gears for a turbo car, or for any car, is if, in the case of drag racing, the car was redlining it's top gear before finishing the race-
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no.

98% of top 8-9sec drag cars out there run ITR geared trannys with 4.9 FDR's.

how can they do 180mph on it, you ask?

tires.

most of them run 26-28" tall slicks, effectively altering the final drive.

205/50/15's are 22.8 or something like that.

its a huge difference.
 
Originally posted by Calesta@Oct 22 2004, 11:49 AM
In most cases yes... but it is more complex than that. You do have to take into account spool up time between gear shifts, and you do have to worry about the time it actually takes to shift gears. Assuming that you don't have to worry about the miniscule spool time and delay during gear changes, then yes- shorter gearing is always better.
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if you go by this- there's 2 types of gearing.

1, the gear box it self. and 2, the findal drive ratio.

play with gran turismo if you don't beleive me.

you can set up a STUPID tight gear box, say 6-8k for EVERY gear (ignoring first of course) but with a stupid small final drive, 6-8k becomes 100mph difference.

so, the gear box gives your your rev range-- how much it drops between shifts.
while the final drive effects how long it takes to go through the revs.


end of story, shorter is faster.

the only time an ls is better, is if you want to highway race, do 180mph on 205/50's, or get better gas milage on long highway trips.

its not faster.
super street editors, like most magazine staff, are bunch of fucking retard ricers who hire SHOPS to do all their installs. have you ever noticed that?

they are journalists with a heavy cash flow to buy cars and pay others to build them.

everytime i pick up a mag, i find at least 5 critical STUPID errors. Like, the b18b GSR motor in the "Guide to B-series" or whatever it was they had a few months back.

retards, all of them.

today, car mags are good for 2 things- bitches, ads.
the end.
 
Originally posted by spectacle@Oct 22 2004, 03:26 PM
I think I'm beginning to understand this now...so if you have a smaller turbo that spools pretty quick it would be benefial to have shorter geared tranny opposed to a larger turbo that spools a lot later in the RPM's where the longer geared tranny would keep you in boost longer????
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no. you DONT stay in boost LONGER. thats bullshit. if you run a 12, and i run a 12, we were both in boost for 12 seconds (minus spool off the line).
after that, with proper tire size and tranny you won't fall out of boost for more than a split second when you first shift.

if you want to stay in boost "longer", drive slower, and run a 13.

again, a tranny has NOTHING to do with spool. its the motor that spools it.
BUT, if your tranny drops you to 4k on your 2-3 shift, and you have a larger turbo, you're going to fall out of boost and have to spool up again.

so, if anything, i would go the other way- shorter tranny with a larger laggier turbo. but i would still pick the short tranny for a small turbo too.
 
for best time at track, you should be at the end of your power band in 4th gear as you finish. for most normal ppl, because 5th is an OD

as far as honda blocks not being suited for turbo....i think the referance was made because of the open block design.

and yes, i understand that this is from SS mag. lol.
 
Originally posted by pissedoffsol@Oct 22 2004, 03:40 PM
if you go by this- there's 2 types of gearing.

1, the gear box it self. and 2, the findal drive ratio.

play with gran turismo if you don't beleive me.
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I like calculations with wind resistance, mass of vehicle, transmission and final drive gearing, power/torque curves from the engine and tire size to figure out exactly which gearing is best instead of using Grand Turismo.

:lol:
 
If you already have a Si or GSR transmission, what's the point of switching to an LS tranny?

Also, if you think a longer geared tranny works better for your turbo set-up, use it, because you must've done all the testing and calculations that show that you can have faster times than your current transmission.

If you want to top out your car in a 3 mile range.. go LS and win.
If you want some fun in a 1/8 or 1/4m, go short.

Transmissions, Spools, RPM, etc...

Most Honda Powerbands are VTEC and Up.. If you get a trans that makes you drop below that when upshifting, you're too long.
 
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