Part Weights

[944 man]

Thats what Id suggest. Ditch everything and chock up the replacement PC window in the runners (far smarter than riveting). Sliders in PC windows only look nice when theyre new in the box: in practice they look very scruffy very quickly. The easisest way to add ventilation is to fit a clear brake duct into the rear quarter and fix ducting hose to it; which you then direct where you like inside the cabin. Dont forget to add exit holes in the opposite quarter or your ears will pop!

Are you retaining the original 28 kilo glass hatch?

 

[Neil Haughey]

Hatch has to be retained for PCGB but seems in Future Classics one has a bit more technical freedom. I need to go to one of their races soon with my brother to have a proper look around and see what ppl are doing. I agree that with the freedom to do it I would defo use rear quarter window venting.

 

[Neil Haughey]

Hard to believe this was almost 2 years ago now, been doing all sorts of things with the car recently to get it ready for next season. The biggest change is I have sourced a fresh LSD gearbox courtesy of Barry Hart (Hartech). Rebuilt front shocks going on and a new Dansk exhaust so I have a perfectly serviceable OEM exhaust (very heavy) if someone wants it for a bit of cash.

Seemed like an oppurtunity to add some more items to this thread so I have edited the first post.

Cheers
Neil

 

[944 man]

IIRC the rebuild kit for the OEM LSD has a 917 part number prefix. I enquired after one once at Merlin Nottingham and had to sit ina new 968 for ten minutes to recover!

Is this an OEM diff or a Kaaz?

 

[Neil Haughey]

OEM rebuilt to the max of the turbo settings range. Unfortunately there isn't a Kaaz unit available for our cars, I asked Kevin about this last year. It was pure luck that Baz had one available as S/S2 boxes with the LSD seem to be rare as hens teeth.

 

[Hilux]

ORIGINAL: 944 man

IIRC the rebuild kit for the OEM LSD has a 917 part number prefix. I enquired after one once at Merlin Nottingham and had to sit ina new 968 for ten minutes to recover!

More than a brand new Quaife ATB? - circa £700 when I enquired when last I owned the 944T as none of the OEM LSD's will be working anywhere near their proper potential after 20 plus years without a full rebuild.

 

[Neil Haughey]

Apparently you can still get the ZF LSD new for 1200 notes. Given that my box was pretty worn, unbelievable noise developed in neutral and difficult to get into 2nd etc. it was perfect timing to make the swap.

My luck has really started to turn with this car, first there was my issues with the rear brakes locking up all the time in race 3 at Silverstone and the car feeling increasingly difficult and edgy to drive. Turned out my front left damper was completely shot but I had been stiffening the others in previous races in an attempt to make the car more planted [hindsight says should have gone the other way]. Then when the 3 good ones are put on the dyno it turns out I have always had full race GAZ 2 ways not track day valved units as they were originally specced, thus I was always tending to have them too stiff. Better still the rear coilovers matched really well and produce really nice flat damper dyno curves with lots of 'nose' i.e. low speed damping, so I had just the fronts rebuilt and modified with Koni race bearing/seals and pressure tube support. Then this gearbox turns up through Baz just at the time when I note by original box is starting to give me some real concern.

Fingers crossed now that the backfire I had when test driving my new smooth cut rev limiter hasn't done any damage to the engine.

 

[944 man]

ORIGINAL: Hilux

ORIGINAL: 944 man

IIRC the rebuild kit for the OEM LSD has a 917 part number prefix. I enquired after one once at Merlin Nottingham and had to sit ina new 968 for ten minutes to recover!

More than a brand new Quaife ATB? - circa £700 when I enquired when last I owned the 944T as none of the OEM LSD's will be working anywhere near their proper potential after 20 plus years without a full rebuild.

About the same cost, but a Torsen type LSD (which I believe the Quaiffes are) is far from ideal, I think.

Neil, Im surprised to hear that Kaaz dont offer a diff, because I thought that Kevin tried to sell me one? Id decided to buy one if I ever had an OEM needing a rebuild...

 

[Neil Haughey]

I thought the same which is why I asked him, advice was to find an LSD gearbox.

Personally I wouldn't want an ATB diff on these cars. The 2 problems I have had which the LSD should help with a lot are both due to an unloaded wheel picking up. The car (S2) doesn't really need any more traction in the dry but being able to trail brake more and get on the power in bumpy corner exits would be nice. I have suffered in both areas at odd times where the inside wheel either locks under braking during transition or the back end whips out after a bump on corner exits when the open diff suddenly transfers the power across the rear axle. In both cases its just a bit better stability required by keeping the 2 wheels moving at similar speeds.

 

[TTM]

What kind of clutch-type LSD would you gentlemen recommend?

I have heard wonders about the OS Giken unit but it's a bit on the expensive side.

 

[Lowtimer]

My luck has really started to turn with this car

Funny, isn't it: the more money you spend on improving it, the luckier you get

 

[Jonny944CS]

ORIGINAL: Neil Haughey

OEM rebuilt to the max of the turbo settings range. Unfortunately there isn't a Kaaz unit available for our cars, I asked Kevin about this last year. It was pure luck that Baz had one available as S/S2 boxes with the LSD seem to be rare as hens teeth.

Neil,

Do you know what the 'max of the turbo settings range' refers to in terms of a test torque-to-turn?

I picked up my turbo LSD from ebay for ~£100 a few years back. It was advertised as requiring a re-build, so I guess few people bid. When I got it home and tested it, my torque wrench read ~28Nm. The only spec I could find was that the value should be above 25Nm.

I can certainly feel it working - so much so that I had to add a little more rear ARB stiffness to re-balance the car.

 

[Neil Haughey]

I have no idea, Baz told me but I was tired from all the driving and quickly forgot [] [&o].

 

[Neil Haughey]

ORIGINAL: Lowtimer

My luck has really started to turn with this car

Funny, isn't it: the more money you spend on improving it, the luckier you get

Careful, could jinx it []

You are right though its just a combination of perserverence, money and attention to all the little details.

 

[333pg333]

It all sounds good Neil. Can you remind me what your car finished up weighing after ditching all the OEM parts listed?

 

[Hilux]

What kind of clutch-type LSD would you gentlemen recommend?

One that doesnt transfer 80% of the drive in an instant which is why you can drive a 944 in a straight line sideways if you get caught out!! It was one of the things I was keen to replace on my old 944T or reduce the bias.

About the same cost, but a Torsen type LSD (which I believe the Quaiffes are) is far from ideal, I think.

Torsens are different and designed more for 4wd so as to lock completely both wheels automatically

Quaife ATB (automatic torque bias) diffs dont lock quickly like an open plate type but move the torque mechanically away from the spinning wheel smoothly and with no lock up. Not used one myself but I know people who do (in front and rear cars) and they are a revelation over open diffs I am told especially in FWD cars. Fit in original housing and forget. No adjustments or dedicated slip oils required.

 

[Jonny944CS]

One that doesnt transfer 80% of the drive in an instant which is why you can drive a 944 in a straight line sideways if you get caught out!! It was one of the things I was keen to replace on my old 944T or reduce the bias.

???
The only factory 944 LSDs I am aware of are 40% locking. 80% would be way too excessive for road car handling and surely lead to wear/damage of driveline parts!

I have no idea, Baz told me but I was tired from all the driving and quickly forgot.

I re-checked my notes, the torque-to-turn range for the factory units is between 10Nm and 35Nm - I'm guessing this was what Baz was referring to.

Quaife ATB (automatic torque bias) diffs dont lock quickly like an open plate type but move the torque mechanically away from the spinning wheel smoothly and with no lock up. Not used one myself but I know people who do (in front and rear cars) and they are a revelation over open diffs I am told especially in FWD cars. Fit in original housing and forget. No adjustments or dedicated slip oils required.

The ATB behaves like an open diff if one wheel is completely unloaded - not great for racing or track days...

In a RWD car the quicker lock-up characteristic of a (40%) plate diff is a help not a hindrance, IMHO.

Also, if you have an ATB fitted make sure the MOT man is aware, or you may find the brake testing procedure leaves you with a bag of scrap metal.

 

[944 man]

A fault shared with the Torsen. My MX-5 has a Torsen II rear and whilst its far better than the viscous type early NAs were fitted with, it still has this achilles heel. Later Mk2.5s have an adapted Torsen which includes an extra mechanical element to prevent their opening if a wheel is lifted, but these are relatively uncommon.

Simon

 

[Neil Haughey]

ORIGINAL: 333pg333

It all sounds good Neil. Can you remind me what your car finished up weighing after ditching all the OEM parts listed?

Hi Patrick, it weighed 1130 Kg with 4 gallons onboard. This includes btw fully working pop up headlights, electric windows and OEM exhaust. With me in it 1202 Kg which puts me 12Kg over the class 2 limit. With my new Dansk exhaust on the car could well be right on the limit. If I take the headlights and a few other things off the car I will have to stick some lead ballast in the passenger seat area.

 

[Hilux]

ORIGINAL: Jonny944CS

One that doesnt transfer 80% of the drive in an instant which is why you can drive a 944 in a straight line sideways if you get caught out!! It was one of the things I was keen to replace on my old 944T or reduce the bias.

???
The only factory 944 LSDs I am aware of are 40% locking. 80% would be way too excessive for road car handling and surely lead to wear/damage of driveline parts!

I have no idea, Baz told me but I was tired from all the driving and quickly forgot.

I re-checked my notes, the torque-to-turn range for the factory units is between 10Nm and 35Nm - I'm guessing this was what Baz was referring to.

Quaife ATB (automatic torque bias) diffs dont lock quickly like an open plate type but move the torque mechanically away from the spinning wheel smoothly and with no lock up. Not used one myself but I know people who do (in front and rear cars) and they are a revelation over open diffs I am told especially in FWD cars. Fit in original housing and forget. No adjustments or dedicated slip oils required.

The ATB behaves like an open diff if one wheel is completely unloaded - not great for racing or track days...

In a RWD car the quicker lock-up characteristic of a (40%) plate diff is a help not a hindrance, IMHO.

Also, if you have an ATB fitted make sure the MOT man is aware, or you may find the brake testing procedure leaves you with a bag of scrap metal.

My understanding is that pre 1984 Porsche diffs are 40%

If so then in my opinion they offer limited benefits on a track because they release at very low torque figures. 944`s have 80% diffs as far as I know but shoot me down if I am wrong as its all a learning curve to us all.

ATB`s are perfectly fine for a track day car - it is with super grippy tires and racing suspension they can come unstuck.

80% diffs are best for full on track cars but the 944 LSD`s unless rebuilt do not function properly and the bias is more extreme unless set up properly hence my original comments.