Polycarbonate Hatch - Opinions Sought

[944 man]

I have a couple of hatches which have polycarbonate windows fitted and other members might recall that I ran an early car with PC windows fitted all around.

I now own a 1988 Turbo which I had in tended to adapt into a lightweight car, but the all electric seats, big stereo and air conditioning have tested my mettle in that respect.

I recently polished a small square on both hatches and they came up well which has lead to my considering fiting one to this newer car, probably followed by the rear quarters, although Im not sure about the fronts because I have become reaccustomed to electric windows (and PC doesnt lend itself well to drop glass replacement).

So, my question is: would you, if cost wasnt a factor?

 

[Cater_Racer]

Hi Simon,

Tom and I put one in the car, it was from Performance Plastics.

It saves quite a bit of weight good for a race car, but I wouldn't go there with a road car.

The back hatch looses all it's integrity and flops about and distorts if opened, it derives all its structural strength from the glass, the frame is trim only. You have to take the gas struts off they are too strong for the polyhatch and would distort it when down, and fling it over the car when up.

It's a b*gger to get the glass out, we found no way but to smash it.

Looks fine, no struts, keep it closed (battery is a race one, screwed to the passenger floor) at it's ok, so long as you never want to open it. We do open it occasionally (usually when scrutineers want to inspect fuel cell) but it's not strong and best left closed.

Gerry

 

[944 man]

Hello Gerry. Im surprised to hear that yours is like that. I bought both of mine ready made and have run a car on the road for over a year with with one of them fitted. I found that it made an already lightened car a little skittish at the back and I ended up refitting the spare wheel to counter this, but that was the only problem that I had and I believe that a heavy Turbo will fare a little better in this respect.

I did remove the struts temporarily because the lack of weight combined with worn pins and worn catches gave me an ejector hatch, which caused pedestrians some concern! New pins sorted that and the worn struts suited it quite well.

 

[Andy97]

EMC Motorsport tell me that the loss of weight (c25 kg) over the rear actually messes with the handling and don't recommend it.
I suppose you could put weight back into,say, the spare wheel well to lower the c of g.

 

[Neil Haughey]

Its an odd thing. When stripped down there is very little weight in the back end. On my own car the lightest corner is the rear passenger one even with a conventional battery in a bat box in the original position, and this on a car with all fibreglass up front. I don't think you can get enough weight out of the front of these cars.

 

[Cater_Racer]

Kevin told me that it would mess up the handling, but we haven't noticed a problem, but then I guess we have a long way to go before we're that finely tuned.

I'm still metal on the front so we are 1200Kgs and a long way to go before we're really set-up.

Don't get me wrong the hatch looks fine, and we have no problems with it, but I don't know if performance plastics are uber-lightweight, but ours is not really that clever for opening and closing.

BTW the lowered coil-overs have vastly improved the handling, we knocked 3 seconds off our BH Indy times.

 

[zcacogp]

ORIGINAL: Neil Haughey

When stripped down there is very little weight in the back end. .... I don't think you can get enough weight out of the front of these cars.

Half a tick; comments like this somewhat fly in the face of the notion that the 944 has well-balanced, neutral behaviour because the gearbox in the back balances out the engine in the front.

If you corner-weight a standard 944, what sort of results do you get? And how do these change when the car is fully race-prepped?


Oli.

 

[Lowtimer]

I can't help you with individual corner weights which take left/right into accounts, but looking at front/rear...

When they were new they tested out as follows (relying only on reputable magazines which did their own measurements):
UK spec Lux - 49% front, 51% rear (Autocar, 1 May 1982)
US spec Lux - 50% front, 50% rear (Motor Trend, May 1982)
US spec Lux - 49% front, 51% rear (Road & Track, May 1982)
UK spec Lux - 48.6% front, 51.4% rear (Autocar, 29 May 1982, presumably with a sharper pencil than on 1 May)
German spec Turbo - 51% front, 49% rear (Motor, 6 July, 1985)
US spec Turbo - 50% front, 50% rear (Road & Track, special issue, 1986)
UK spec S - 51% front, 49% rear (Motor, 22 Nov 1986)
US spec S - 49.5% front, 50.5% rear (Car & Driver, Aug 1987)
US spec Turbo S - 51% front, 49% rear (Road & Track, June 1988)
US spec Turbo S - 50.9% front, 49.1% rear (Car & Driver, June 1988)
US spec 2.7 Lux - 49% front, 51% rear (Road & Track, Apr 1989)
US spec S2 - 49% front, 51% rear (Road & Track, Oct 1989)

Note that Turbos are generally marginally nose-heavy while NA cars are normally marginally tail-heavy, which makes sense given the weight of the turbo, intercooler and extra exhaust stuff.

 

[944 man]

Weight is more than balanced by keeping the fuel tank full. Sixty kilos on a series two car!

 

[Neil Haughey]

Correct. Normally test weight or corner weight with some nominal amount of fuel such as 20 litres which is enough to get through quali or if the car is really light always keep 15 to 20 in the tank to help balance i.e. fuel up to say half a tank. Not ideal though as the bottom of the tank is same side as the driver. Best thing is to get the car really light and stick a stonking big lead weight in the passenger side. This is what 968s in class 2 can do as their weight in the PCGB regs is quite high compared to a 944 S2. Would be a struggle to get an S2 that light that one could do the same, remember the regs reduced the S2 down to 1165kg including the driver which means a 1090 Kg car for someone like me. Mine is nowhere near that, I am around 1200 or so with me in it.

CSCC one would just go as light as is possible as they don't have a minimum weight. I believe Rob Holyman's S2 was incredible light, well under 1100 Kg ISTR he also ran a poly hatch and I believe he still claims the unofficial NA 944 lap record at Snetterton.