Easy way to increase power and torque at the wheels

[jibby]

Can any of you experts tell me the differential gearing ratio on a 1993 Supra tt LSD vs. the stock 1992 SC400 open end differential..Is there a difference? I have no idea if the gearing is matching up right on my sc. I have assumed all along it is the same, but after reading this thread it appears it is not. Any thoughts on this?... the 1993 supra tt LSD installed on the early model SC400, benefits or negatives in regards the gearing ratio's?

 

[Anaema]

you could just steal the LSD unit and not the ring a pinion gears, that would give you the benefit of an LSD and the same gear ratios as the SC400. considering the Supra LSD and the SC400 open diff are the same size.

 

[jibby]

Anaema, I have the Supra LSD already installed and running on my SC for like six months now. Just want to know where I stand with the Supra gearing ratio vs. Sc400's are they the same? I guess I can always google search for the answers, because there is no info on this forum...

 

[Damien]

The SC400's diff ratio is 3.916:1 which is the same as the auto TT Supra's diff so you're spot on. You'd have noticed if the diff ratio was different - I changed from the stock 3.916 to a TT Soarer 4.083 LSD and it definitely felt punchier.

 

[jibby]

DAMIEN - You just answered two questions that have been on my mind all day...Thanks Bro.... So 4.083 is the next step up in the ratio that you would suggest? What did that change do to your speedo, top speed, are you reving high while riding the highways? Thanks again great info!!!!!!!!!!

 

[Damien]

I worked out that it revs about 4% faster for the same road speed which isn't much but it definitely accelerates quicker and it's not buzzing it's head off on the highway. I don't have a g-tech so couldn't do back to back comparisons but the couple of guys who drove my car before and after all noticed the difference, but bear in mind mine is a manual.

So if the speedo says you're doing 60mph and it's 4% faster than what it should be that that's 104% of the actual speed. Divide 60 by 104 then x 100 to get the actual speed = 57.7mph.

Or if you want to know what the speedo is reading when you're actually doing 60mph it's 60 x 1.04 = 62.4mph but it's easier to mentally make it 5% which is 63mph on the speedo (take the first digit, divide it by 2 and add it to the whole number).

The diff you'd look for with the 4.083:1 ratio would be from a 5 speed manual SZ JZA80 Supra (ie. non-turbo).

Happy to help : )

 

[SC & RX]

I read somewhere that losing 1 pound of unsprung weight is the same as losing 2 pounds of sprung weight. So it really blows my mind when I see cars with wheels on them that I know weigh more than the stock ones they too off, even if they are the same diameter. One can go to: wheelweights.com to see what I mean.

Before anyone decides this should be in a different section... consider the performance benefits to this simple suggestion... smaller diameter tires

:shock:

That's right, I said smaller. While investigating an upgrade to 18" wheels a number of very interesting things became clear. First of all, it is VERY desireable to lower the weight of tires and wheels. Why? Lower weight allows them to be accelerated easier (power to weight) this gives a REAL increase in the horsepower (or whatever power rating is used) AT the WHEELS, where it counts. Secondly, using a smaller tire DIAMETER has the exact same effect as changing the gearing in the differential.

The case for my 1999 LS400. Stock 16" wheels weigh around 25 pounds
(I will weigh them when I get the chance, if anyone has done so already on the stock 5 spoke wheels please post your findings)
Stock tires are 225/60-16s and also weigh about 25 pounds. Combined weight is 50 pounds per wheel/tire. Stock tire diameter is 26.6 inches. Stock tire tread width (contact patch width) is 7.2".

As I posted in the exterior section (which includes wheels, I suggest a separate tire/wheel specific category) I am leaning towards the SSR forged GT1 in the 18x8 size. This wheel weighs 19 pounds. Going with a 225/40-18 gives me a 23 pound tire with a 25.0" diameter and a 8.3" tread width.

This choice gives multiple benefits.
*Rotational resistance is lessened in 2 distinct ways, 1st the 8 pounds per tire/wheel lighter weight, 2nd is the reduced moment of enertia due to the smaller diameter. Both yield usable horsepower gains at the wheels.
*Grip increases due to the over 1" wider tread.
*Torque at the wheels goes up 6.4% due to the smaller diameter which has the direct impact of having a better final gear. Due to torque multiplication of the gearing, the torque increases the following amount in each gearassuming a 22% drivetrain loss at peak power)
1st = +144rwtq (2391rwtq vs. 2247rwtq)
2nd = +93rwtq (1551 vs. 1458)
3rd = +61rwtq (1011 vs. 950)
4th = +43rwtq (712 vs. 669)
5th = +32rwtq (534 vs. 502)

Lightening the wheel/tires has a similar impact as using a lightweight flywheel without the engine feel drawbacks.

More positives. Reducing the unsprung weight makes the car handle better and the suspension more effective at recovering.

Also, in this case, the car gets lighter by 32 pounds.

All in all this combination could be good for 2 to 5 tenths 0-60mph and quarter mile.

Drawbacks, harsher and noiser ride due to stiffer sidewalls. More wheelwell gap, in this case about 3/4 of an inch. I have a set of Eibach springs so the gap will be less after those go on.

 

[INASNT]

I read somewhere that losing 1 pound of unsprung weight is the same as losing 2 pounds of sprung weight. So it really blows my mind when I see cars with wheels on them that I know weigh more than the stock ones they too off, even if they are the same diameter. One can go to: wheelweights.com to see what I mean.

So you would rather drive around with the **** looking stock rims than have some nice rims that make your car 0.01 sec slower?

 

[SC & RX]

So you would rather drive around with the **** looking stock rims than have some nice rims that make your car 0.01 sec slower?

No, that was not my point not at all. There are lots of lighter rims that look better, are wider and lighter than stock from companies like: Volk, Motoforge, OZ (Superleggera) Gram Lights, Work, Weds, Racing Hart, etc... The point I wanted to make was that a lot of the aftermarket wheels out there are heavier than stock, so if one was going to replace their wheels they should take the weight into consideration. And frankly, there is a bunch of sh** that people do to their cars that make them worse than before. Thigs like spinners that are just plain idiotic, too large of diameter rims that ruin the ride and decrease braking distance, etc... I wonder what the next fad will be. The US needs an agency like TEVA to keep people from making their safe cars into dangerous weapons by worsening the handling of the car. Next time you see a wreck, take a close look and you may see what I am talking about here.

 

[INASNT]

Yeah I know where your coming from. My other car is a race car with stripped out interior, RE55 tyres and around 550hp.

 

[SC & RX]

That must be a blast to drive. The only real fast times I have had were on a GPZ 750 I used to ride. And one time in a Pro Street car and then in a "dragster" that was on a rail at some place in Dallas. Is a race car fun like a motorcycle, but not the same piss in your pants feeling you get on a bike when you almost lay it down or nearly get smacked by an 18 wheeler? I know it probably doesn't hurt the same when you wreck.

Yeah I know where your coming from. My other car is a race car with stripped out interior, RE55 tyres and around 550hp.

 

[jibby]

Inasnt - 550hp not bad at all, that will get the job done in my book. What car do you have that in your Toyota or Nissan? Just curious?

Lighter rims, Driveshaft, flywheel all give you power gains.....

 

[Zuffen]

Don't forget with larger diameter rims you get a smaller sidewall height (for the same overall diameter) which will also slow down you 1/4 mile time.

Within reason the larger the profile the more flex the tyre (tire) has and the longer the contact patch it can achieve.

Larger contact patch = more grip = faster accellaration.

Sc & RX,

Larger overall diameter increases braking distance not decreases braking distance. They do reduce the braking system's efficiency if that was what you were aiming at.

 

[SC & RX]

You are correct, I was typing too fast and did not proof what I had written. I must have meant to write decreases braking effectiveness or efficiency, not decreases distance.

Sc & RX,

Larger overall diameter increases braking distance not decreases braking distance. They do reduce the braking system's efficiency if that was what you were aiming at.[/QUOTE]

 

[JBrady]

Wow, old thread, facts unchanged.

Tire width and diameter are part of a vehicles engineering. Changing sizes can help or hurt performance depending on the specifics. A larger diameter tire with no other changes will slow a car down and degrade the braking ratio. The larger diameter effectively creates more leverage AGAINST the brakes. A larger diameter wheel with lower profile tires will harshen the ride quality of the vehicle. There is no denying that larger wheels look great... just consider that you need to engineer the change to avoid a negative result and even with engineering certain trade offs are unavoidable.

 

[rivmasta]

Offroaders have been doing it for ages.

With an Oz Class 2 (16500cc) car if you're on a short track, go 30" tyres to improve corner exit speed - on a longer track where you dont want to be bouncing off the limiter in top - taller tyres, say 33" and you'll spend alot more time off cam and bogged down out of corners, and you'll have to increase your braking markers as the car doesnt pull up as well, but a heaps better top speed, better turn in, smoother on the rough stuff and if you can get it right, better response from the steering brakes.

smaller circumference = shorter ratio's basically.

 

[Nick M]

Nick, you are messing up the term inertia. Inertia cannot be gained or lost. I think you might mean momentum? Also, the flywheel accelerates faster in 1st than 4th. I don't know how you would get the other way around...

Your last paragraph makes no sense at all to me.. yes, the car will accelerate faster with the gearing change, but gearing change is not what we are talking about here. The gearing change does not affect what the engine is putting out at all. The bonus with smaller lighter wheels we are talking about here, is a smaller moment of inertia. Think about if you had a car wheel on the back of your bicycle. A heavy wheel is going to take all of your power to get going. Very little will make it to the road. The wheel actually takes your energy you are delivering, and stores it in the form of rotational kinetic energy. You can get this energy back by sticking your hand on it to stop it. You'll get heat. Now, put a nice light bicycle wheel on your bike. Even though the wheel is much bigger (and the gearing change suggests you will accelerate slower), the wheel has a smaller moment of inertia, and will eat less of your energy. You will accelerate MUCH faster.

Don't underestimate the amount of energy that rotating mass can eat up either! It is huge! With bikes, gains of 3-5hp at the wheels can easily be seen by taking a few hundred grams off the crankshaft. This is because the crankshaft rotates very quickly, and energy is eaten to the square of rotational velocity.

Lighter flywheels allow your car to accelerate MORE quickly. You say the increase in weight *helps*? No. It does not help you get it going. It helps it keep going once it is going, because it has more angular momentum. It is *harder* to get going. Weight never helps acceleration. Ever.

The only reason I can come up with to dyno a car in a 1:1 gear, is that the output gearset of the gearbox and driveshaft may represent a smaller load in higher gears, as they are not accelerating as quickly, and 1:1 "evens the field" across all motors, for the gearbox spinning load. I need to do some simulations though, with numbers for a real gearset and driveshaft, to see the effect that might be had. Hell, the problem is too complex for me to figure out without a few hours, if the driveshaft even IS a greater load or not...?

I dont know where these get to where they are, perhaps not rereading what you put up. I am only talking about the gear change from the smaller diameter. And the load with the higher or taller gears is greater not less. He could use lighter wheels that are the same diameter and get a small gain from driveline losses being lowered.

Lighter flywheels allow your car to accelerate MORE quickly. You say the increase in weight *helps*? No. It does not help you get it going.

No I dont think a heavier flywheel will help acclerate. I am pretty sure I have never said that in any forum.

 

[INASNT]

Less rotational mass more acceleration, easy formula