As i have mentioned in the past i`m using a 4x4 MT75 gearbox with a twin turbo coswoth v6 engine.
I`m hoping to extract 400hp from the engine, with water injection i might be able to occasionally get 500hp (after sva i`m going toeventually lower the compression ratio).
I am aware that the third gear of said gearbox is weak, so i will limit the boost in third gear to limit torque by monitoring wheel /engine speed to calculate gear.
Anyone know what sort of power i should limit for the rest of the gears.
I recon that 4th being a 1:1 ratio it will be able to take 500 hp, as there is no torque multiplication (like lower gears), the diff and transfer case will take it.

Any thoughts?

Darren

[Edited on 6/3/08 by turbodisplay]

Why not use a T5 gearbox and not worry about limiting the horsepower?

its a bid a strange question because...

gears wich fase higher loads are also build stronger then the other ones...

sow first gear has the widest gearpinions etc etc.

sow it will depend on other wear (wich can wear an gear/particular gear out..)

and offcourse you have the fact that maybe a gear should have had 30mm
but that they gave it 29mm (it needs 25mm to survive) and thats it...

in other words maybe the safety factor isn't evenly spread and that could be the reason that one part gear is the weakest....

Tks


p.d. i would look for a BMW M3/M5/M6 gearbox should be able to cope with some power...

4x4 is the problem.
Even a skyline gearbox is too big, i`ve got one in the garden which "is an eyesore" .
I know third is a week point for sure as it is the most common for going bang.
The rs focus limits torque in first gear that uses an MTX75.

Darren

I have a mate, Paul, with a Dax Rush Quadra, and a Cosworth engine coupled to an MTX75 box.

Well it was.

Until the last track day when it lunched itself. Mind you the engine is in a very high state of tune (bigger turbo, custom map, bigger injectors, charge cooler etc etc). Not sure of the exact output, but it's around 350 bhp.

Paul's view is that cause the boxes cost £50 from ebay, they are like tyres, a wear item!

Mike

Yeah i have one spare, only problem is the replacement time / difficulty.
I need to remove the dash, 20 - 30 m6 bolts, disconnect the loom, lots of trim pannels etc.

Next car i make will have the gearbox and engine on a subframe!

Darren

turbodisplay - 4-500 horses is great. Im putting a supercharged 4 litre or a 5.3 V12 jag engine in after SVA and already have a bec/cec showdown lined up with tjoh84 (see here)

4.0 - Lexus v8?
Possibly the best v8 for cheappower.
When i started i designed my bay for a 4 pot, then i squeezed in the v6 with turbos.
I wish i could fit a v8 tt engine in now!

Darren

drive to the front is by viscous coupling so you cant shock load the front driveline. its 2nd and third gear that will give up .350hp is about the limit for a stock box in a sierra and thats about what youll get from your engine so if your car is significantly lighter than a sierra you should be ok,doesnt matter how much hp or torque you make its what the tyres make the drivetrain take that counts.

Have a word with BGH http://www.bghgeartech.co.uk/html/bgh_home.html
they may be able to beef up the box for you.

North of 300 BHP will eat the box in fairly short notice - yes the car is lighter but you are hardly going to take it gently are you?

T5 is your (only) answer unless you really love taking apart and putting together again on a regular basis...

EDIT: P.s. What turbos? Hybrids will get you over 600 without H2O but you will need a steel crank, group A rods and pistons and cams. BOA bottom end with BOB top and a decent ECU?...

[Edited on 6/3/2008 by NeilP]

my old saff 4x4 ran 350hp for several months before strippping third gear,the funny thing was it broke shortly after changing from 17" wheels to 16" with better tyres

RE turbos
I`m using a skyline r32 turbo and T3 from a renault 21.
Skyline primary turbo, with r21 turbo kicking in at 3-4k rpm.
I`m going to make a new intake manifold eventually, one less restrictive.
I`ve made my own ecu as i need many analouge inputs and quite a few mosfets to control the sequential turbos.
I was going to have traction control built in, but the person who made the boards made a mistake on the wheel sensor circuit. So i`m making my own traction control seperate which wil have the ability of outputting the gear selected.

Darren

1uzfe lexus aint that big....

should fit a normal locost engine bay, and if the turbo's partly hang out of the side of the car..... if done nice where's the shame in that?

if I'm not mistaken there iis a 4wd tremec T5 in some production cars.... maybe an idea, not sure btw

grtz Thomas

[Edited on 7/3/08 by thomas4age]

Re size of engine, I`m not making a seven, the problem is the front diff and prop limiting the engine length. Also the engine would be longer as an adapter plate would be needed.
As v8s go it is a nice compact unit i think i was told 60 cm cubed?

Darren