Enginerring Qeustion

Alright for all of you tech junkies out there here is my qeustion!

Can you achive a 50/50 car balance using a RB engine and what main modifications would you use to achive this?

I predict cutting the firewall and tranny tunnel to move the engine back and using some sort of linkage for the shifter.

Has anybody come close to 50/50?

What is more imortant than the balance is how tune the suspension and tires; that's right, you can tune youre tires! Once you've got you're RB in go to a truck stop and get it weighed. Find the weight distribution. Lets assume its 53/47. The recomended inflation pressure is 29 psi for all four tires. The front has more weight so it needs more air in the tire. Take the recomended inflation pressure: 29 psi
Multiply it by two: 58 psi
Multiply by the % of car mass on the front wheels: 30.74 psi
Inflation psi front: 31

Repeat the procedure above using the % of mass on the rear wheels and you get the rear inflation pressure.
Inflation psi rear: 27

This is a good starting point. More tire pressure makes more grip, up to a point because it make the sidewall more rigid. If you over inflate the tire, your contact patch will be too small. Add air to the tires you want to grip the road better and release air from the tires that have too much grip. Experiment with it and find a balance that suits you.

What is more imortant than the balance is how tune the suspension and tires; that's right, you can tune youre tires! Once you've got you're RB in go to a truck stop and get it weighed. Find the weight distribution. Lets assume its 53/47. The recomended inflation pressure is 29 psi for all four tires. The front has more weight so it needs more air in the tire. Take the recomended inflation pressure: 29 psi
Multiply it by two: 58 psi
Multiply by the % of car mass on the front wheels: 30.74 psi
Inflation psi front: 31

Repeat the procedure above using the % of mass on the rear wheels and you get the rear inflation pressure.
Inflation psi rear: 27

This is a good starting point. More tire pressure makes more grip, up to a point because it make the sidewall more rigid. If you over inflate the tire, your contact patch will be too small. Add air to the tires you want to grip the road better and release air from the tires that have too much grip. Experiment with it and find a balance that suits you.


Ehh....while your math makes alot of sense, I don't know about that last paragraph. At least in drag racing, when you release air from your tires it makes the tire more "floppy", thereby putting more rubber to the ground. This equals more grip for a better launch. My point is that I thought it works in reverse of what you said, you inflate when you want less grip and you deflate when you want more. But I could be high.

more tyre pressure doesn't make more grip because if you over inflate past the tyre's recommended pressure the wheel buldges and contact between the wheel and ground is reduced. DO NOT DO THAT! it is also dangerous. Why? because if you start racing with overinflated tyre's the extra heat will increase the volume of the air inside which inturn increases pressure. When it reaches a certain pressure the tyre will burst and you'll be in shit creek as your car verre's across lanes of traffic.

I'd probably end up having to use ballast (or relocating certain things) to balance the car out so that you could achieve 50/50. If you moved the engine back a bit it would be easier to balance out. Lowering it down would also aid achieving a lower centre of gravity.

Add Weight To The Back, You'll Get A 50/50 Balance. Actually Yes A 50/50 Balance Is Obtainable With Quite Abit Of Modifications And Expense.

Which Rb? Because The Determines How Much Weight Needs To Be Removed/moved.

Rb20det In S13 Fb, For Example:
Fiber/carbon Fenders
Carbon Hood
Carbon Bumper
Stationary Lights
Move The Battery To Rear Of Car
Stainless Exhaust Manifold
Aluminum Intake Manifold/plenum, Piping, And Fmic
Forged Internals
Aluminum Flywheel
Coilovers
Aluminum Adjustable Supension Arms (front And Rear)
Swaybar (lighter But Stiffer)
Lightweight Wheels
Lightweight Brake Components
Remove A/c System Completely
Use A Copper Or Aluminum Radiator
Use A Lightweight Electric Fan
Remove Bumper Support
Then Fine Tune Your Suspension To Adjust Load Carrying Where Its Needed.

That Setup Should Remove Close To Or Over 200lbs If Done Right. The Body Parts Alone Will Save You Close To 75lbs, The Battery Moves 25-45lbs To The Rear Of The Car, The Internals And Flywheel Will Lower The Engine Weight By About 10-15lbs, The A/c System Is Close To 50lbs, And Eveything Else Saves You Quite A Bit Of Weight Also.

Well my buddie has already procured a RB26 and a RB25tranny I need to by a 180sx when I get back on Okinawa I'm going to build a Sil 80. I do plan on cuting and reworking the firewall back and redoing the tranny tunnel. Everything is getting pulled out and putting in a aluminuim dash and such to help with weight and shifting the engine back. I wondering if I should yank the rear tank and place a fuel cell closer to the center possibly in the cab (but thats not very safe) If anybody has any idea's theroies and tips keep em coming.

Also if anybodies looking for JDM parts let me know I can ask my Boy or you can wait till I get back And I'll yank em for ya.

Just between you forum guys I can find SR's CA's and RB's for cheap over there.

I Would Do A Fuel Cell Just For The Weight Savings And Anti-slosh Factor.

if you're that set on getting perfect 50/50 weight distribution, (although i'm sure musicsurfman would disagree) have you considered a lighter engine? how much hp are you looking to make when you're done.

I tell you the truth:

- Lower tire pressure increases the weight transfer in a straight line making hookup easier. Thus you could say more traction for braking and drag racing.

-More pressure reduces side wall flex and body roll so your handling is improved. The contact patch is smaller when you're sitting still but in a corner, compared to the contact patch a lower psi setting, the contact patch is bigger because it's not distorted by the side wall on the outside of the corner compressing. Not to mention the fact that the body roll is reduced.

-This effect can be applied to just one end of the car too. You can get sharper turn in by adding psi to the front and relieving some from the rear.

-The heat build up in the tire is caused by the flexing of the tire as it roles. The HEAT is what causes the blow out because the rubber simply gets too hot, THE PRESSURE IS NOT THE CAUSE OF THE BLOW OUT!

-Because of the above fact, more psi in the tire reduces the heat build up because the tire doesn't flex so much. So MORE PSI IS SAFER AT HIGH SPEED. Not to mention you'll handle better too.

Try this: take you're 240SX for a spin and you'll notice that if you don't use the gas and brake to shift the weight around you'll understeer just a little as you enter the corner. Inflate the front tire to 31 psi and the rear to 27 as I said and you'll notice the turn-in at corner entry improves. Try this, anyone who doubts what I say, try this and the truth will be revealed to you. Further, you can ask some pro road or rally drivers and they'll tell you the same thing. I tell you the truth, the world is not flat as was once believed.

Don't argue with me until you try this. If you've tried it and still disagree you either did it wrong (didn't follow instructions), don't want to admit the truth, or you don't have the talent to feel what your car is doing. If you like, I can tell you some good alignmet tips that can further tailor your car's handling to your liking. I've had many cars with greatly varying handling characteristics and these techniques work to improve, or tailor to my liking, the handling of all of them.

Try this: take you're 240SX for a spin and you'll notice that if you don't use the gas and brake to shift the weight around you'll understeer just a little as you enter the corner. Inflate the front tire to 31 psi and the rear to 27 as I said and you'll notice the turn-in at corner entry improves. Try this, anyone who doubts what I say, try this and the truth will be revealed to you. Further, you can ask some pro road or rally drivers and they'll tell you the same thing. I tell you the truth, the world is not flat as was once believed.

Don't argue with me until you try this. If you've tried it and still disagree you either did it wrong (didn't follow instructions), don't want to admit the truth, or you don't have the talent to feel what your car is doing. If you like, I can tell you some good alignmet tips that can further tailor your car's handling to your liking. I've had many cars with greatly varying handling characteristics and these techniques work to improve, or tailor to my liking, the handling of all of them.



Okay so I tried your theory in my corvette because my 240 isnt running yet. I had all four corners at 26 psi, and noticed a moderate understeer into sharp turns in my neighborhood. I then filled them to what you reccomended and noticed that it had a perfect steer with this setup, no understeer and no oversteer.

welp this could disaprove wanting 50:50 the entire time. When it counts most that you have perfect balabce is accelerating out of a corner. The other day I was watching my new BMI video that featured the 350z.

They had some engineers tallking about it and one thing they covered was the chassis and balance. They designed the Z to be a little bit front heavy, so that under acceleration when the weight shifts to the back of the car it has a 50 50 balance. Parked on the street it has like a 53 47 balance or such.

some food for thought.

If thats true 50 50 regularly would give u a real tail happy car exiting corners.

if you're that set on getting perfect 50/50 weight distribution, (although i'm sure musicsurfman would disagree) have you considered a lighter engine? how much hp are you looking to make when you're done.


The reason we went with the RB is due to the stock trim potential. were looking to push at least 700rwhp I know you can push a SR to around 500 with stock guts. If I can save money on machine work and parts witch will in turn save time I'll take the RB. But if you can justify the cost-HP in a SR we can always take the RB back to the yard.

I Would Not Argue With The Lighter Engine Comment, I've Always Said An Engine Choice Should Be Based On Your Goals. I Like All The Engines For Their Purposes But I Choose The Rb20det For Me Because Of My Plans And I Only Argue Its Side To Clear Up Some Misconceptions.

I'd Watch How Much Power You Push On A Stock Block. If Your Going For Dyno Power Great But As A Driver Or Race Vehicle I'd Do Some Major Precautionary Upgrades, Because Yeah It May Handle That Kind Of Power But For How Long?

I Would Not Argue With The Lighter Engine Comment, I've Always Said An Engine Choice Should Be Based On Your Goals. I Like All The Engines For Their Purposes But I Choose The Rb20det For Me Because Of My Plans And I Only Argue Its Side To Clear Up Some Misconceptions.

I'd Watch How Much Power You Push On A Stock Block. If Your Going For Dyno Power Great But As A Driver Or Race Vehicle I'd Do Some Major Precautionary Upgrades, Because Yeah It May Handle That Kind Of Power But For How Long?

I understand surfman. I'm not a newbie when it comes to building cars just to 240's (actually 180's). When I was on the Island being the grease monkey I am I started helping the guys who had 180's, silvias, and skylines build them into real nice machines. There not my typical are of expertise though. I've spent most of my time building Rockcrawlers and offroad vehicles. In that enviroment it will brake no matter how bullet proof you build it. With a SR I figure to turn 700 I'll need New pistons, rods, and a crank and do major head work. I may be able to get away with only swapping the Pistons and maybe Rods in a RB(Both the SR and RB will need bigger turbos). The only reason I feel I can get way with this is being in Japan RB's and SR's are their SB350 chevys. There in every wreckingyard and every shop has parts. I'm hopeing to tap all of you guys engine and 240 Experience due to the lack of experience on my part.