Large throttle body / speedo

[Guest]

I have been trying to find out which 5 cylinder audi throttle body I can fit to my 924 to give that little extra bhp. I have looked at a few around the scrap yards and they have all been very different. Can anybody throw some light on which one I need to look for and do I need to change the intake pipe as the shape of the throttle's I have seen are different from standard 924 shape.
My speedo !! The speedo registers mph but the miles and trip do not go round. Can anyone tell me where I could get another one or can I get mine refurbed or by parts to do it myself ??
Thanks for helping, Rob.

 

[924nutter]

I am preparing an article for the post about repairing the trip meter for the cost of a couple of nutserts. In a nutshell the tiny nylon plastic sprocket that drives the numbershaft cracks and doesnt drive the shaft any more. You need to carefully peel back the bezel to get to the innards. I have repaired mine by buying two 5mm nutserts from an engineering suppliers and supergluing them over the bush on the sprocket to close it back up. Thoroughly roughen all mating surfaces for good adhesion. Cut off the excess nutsert and carefully press the sprocket back onto the shaft. Does it work? Well mine has been working again for three months. I read somewhere that the sprocket is being remanufactured, and is available for £25.

Its too wet to look under the bonnet of the 924 but I will get the part number off it. They are for sale at a number of outlets, (eg Porscheshop) but I guess you don't want to cough up £145 odd.

 

[Guest]

I think that Porschapart offer a referb service.

 

[Mrkjblue]

I repaired my 911 speedo last year nice afternoon project, very similar to the 924 and gears should be available from http://www.odometergears.com/subpages/porsche.html

http://forums.pelicanparts.com/showthread.php?threadid=181176

 

[ClubSport 911]

to give that little extra bhp

Just be aware, that large = good only at high RPM and wide open throttle (racing?). At low speeds, you need to fill the cylinders quickly, and a smaller opening actually assists this process, by speeding the air-flow. If you go too large, you may well lose low down torque, and engine response will suffer. Throttle body size is always a compromise between low speed torque and high speed BHP.

Hence why Vario-ram was invented

For more detail, follow the thread here

Steve

 

[924nutter]

I am not an expert on these things, but as I see it, with a throttle-body, it is not so important to have high gas velocity through the butterfly. Bernouli's law says that as the speed of air increases, its pressure is reduced, but there is no pressure reduction effect required due to the presence of fuel injection, which promotes good droplet atomisation on its own, that, in turn, aids low speed torque due to more complete combustion. Given that the Haynes manual for the WA, and XJ coded Audi engines, shows displacement, compression ratios, valve diameters, and cam timings are all identical in European spec., it follows that gas velocity into the combustion chamber is more or less the same, therefore swirl, which assits both the combustion process, and scavenging, is also unchanged. Furthermore, as the fuel is injected, effectively not sucking through the narrowness of a carburettor, 10 brake horsepower and some 20lb/ft of torque is released without further modification to the engine. I would have said that the injected engine produces more power and torque with a lower gas velocity at the throttle butterfly, which it must have because there are no carb chokes to suck past. In any case, the primary butterfly, opens on its own for up to 50 degrees of spindle rotation, remaining unchanged in dimension from the standard orifice size, to aid fine throttle control. It is the secondary butterfly, which starts to operate as soon the tab on the end of the primary spindle reaches the end of the free movement slot, that is about 20% larger in cross section than standard giving rise to better airflow.