LSD or not

[mr-p]

Right,

After coming to terms with my donor having a DOHC lump in it, it appears that I have a 7.5" 3.92:1 open diff.

After a bit of research here & on LCB it seems that this is not ideal for this type of car, and the ratio is too low for a zetec(which may be the favoured option), what is the general opinion?

Should I start the hunt for an LSD to be better for the long run?

Also my donor came with an MT75 box fitted & a Type 9 in the boot, is there a winner in the box dept?

Mr-p

[spud69]

Hello Mr-p,

The open diff is fine in the roadster, the only time you will really notice the difference is when you are really pushing it on the track or road. You can still achieve some great power slides and donuts with the open diff. The only time you will really notice it is on tight powered turns where it will tend to spin up the inside wheel. The roadster is such a well balanced and grippy car the open is fine. For the cost of an lsd its not really justifiable for the roadster. However, i do plan an lsd upgrade in the future. For the 3.92 diff the dohc is quite good on torque that you will probably benefit from the longer gear range in 1st and 2nd so wouldn't be a problem, mine is a 3.62 and 1st and 2nd are a bit short. You will find the open diff easier and safer to drive until you get used to the handling and characteristics of the car.

The ford 2l dohc is a good engine but its also quite big and heavy, you'll also need to consider replacing the EFi side of the engine due to its size and complexity. Due to its age you will also have it easier on the emmissions tests, no cat required.

The MT75 gearbox is a strong box capable of taking more power than the type but it is slightly bigger and you will need to modify the tranny tunnel a bit and end up with a slightly smaller footwell put won't be a problem. The type 9 is a good box, upto about 250 horses. Fit a quickshift stick and remove the damper and it feels much more positive and racier.

Have Fun.....AndyH

[mr-p]

Cheers Andy,

Thats sort of cleared that up then the diff is staying where it is, I had to move the pass/s bracket over a bit as the top mount is wider than the lower one but no problem.

Think I'll flog the DOHC & box, start the hunt for a zetec & use the type 9. Is it true you need a cat for anything after '95?

p

[spud69]

Yes it is, you also need a Lambda sensor with some kind of fuel injection system or throttle bodies with a megasquirt system.

Try considering a ford cvh engine for your test then its an easy upgrade to a zetec engine, new ones are cheap. There's is plenty of info on here and locost for the swap.

AndyH

[deezee]

I'd just throw in the DOHC for the test. Bin the EFI and pop on some cheapo bike carbs for £50. Make a inlet manifold for around the same and use megajolt. Thats one perk of the DOHC, it has a trigger wheel built into the crank, complete with sensor.

Whatever engine you use, your going to be spending money on it to make it fit (exhausts, manifolds, sumps and management) So you might as well pass your test with the engine you have got, then throw in something else when emissions aren't a problem

Oh and to answer the LSD question, a RWD 260bhp MR2 turbo only had it as a optional extra, so until your getting over 200bhp/tonne and wanting to go wide open on the throttle out of a corner, I wouldn't bother.

[mr-p]

The question now is how easy is it to swap the DOHC for a Zetec? Wouldnt it be a pain in the ass to redo the exhaust, mounts etc?
The DOHC route is definately the cheapest option for getting it on the road as it is sitting in the drive.

Is it right that what ever it goes through the test with is what its tested by forever, so a post 95 Zetec would not be a worry. The reason being the missus has a 2000 2.0 Mondeo which may not be MOT renewed so it may be canabalised or do a deal with the scrapppy for a motor + other bits i need for the build.

p

[snapper]

I would build it with the DOHC, diff and gearbox that you have, then swap out after IVA.
The diff is not as much of a problem as the gearbox, diffs are easy to change and the 3.9 gives very good acceleration, the main problem being the very low 1st gear and the big gap to second in the Ford MT75 and Type 9.
The rev limit of the engine is another factor, down load one of the many gear ratio programs and have a play with wheel, tyre sizes, diff ratios and gear ratios.
When you get the lower gears working as you want the higher gears are far to long and vis vers.
Ideal ratios are 1st 2.8 to 2.5 2nd 1.8 to 1.6 3rd and 4th are ok 5th could do with being about 0.9 not the 0.825 that it is.

[mr-p]

Cheers all, have direction & lots to do again without using spends..