PRDA Forum Archive

[andy97]

Hi, I'm wondering if the old 924 series forum exists in an archive somewhere? I remember there being some useful posts about modifying 924s with the head from a Turbo & with bike engined carbs to get more power. CAn anyone point me in the right direction please?

Thanks

[admin]

Hi Andy

Unfortunately not; we had to lose the old forum when we developed the new website at the start of the year. It wasn't practical to archive the whole forum, so we started from scratch with the new site. Apologies.

If you have a specific question though, I'm sure someone on here will be able to help if you post it up?

Regards
PDA Site Admin

[ANDY97]

Thanks for the reply. I am not sure how to phrase the question really! But I do have a recollection of a thread on the old forum in which someone explained that the standard 924 engine didn't breath too well & was therefore difficult to tune for performance. However, one remedy to this was to use the head from a 924 turbo allied to throttle bodies or bike carbs, possibly also using the 924 series cam & vernier. I seem to remember that one 924 racer had done this, presumably on a road/ track day/ sprint car (as I am aware it would be illegal in the series).

I am fairly none technical myself (as you can gather) but I am just thinking out loud really about the possibilities for a 924 for CSCC Future Classics and the 360 MRC 6 hour race.

Thanks

[mart924]

HI there,

Dont think I did the post you are talking about, but here goes! The head on the 924 is extremely restrictive and that is where the problem lies. The turbo head has a combustion chamber whereas the normally aspirated head doesnt. Both pistons have combustion chambers, the turbo head has the combustion chamber to lower the compression ratio. The theory goes that you can use Golf pistons and rods which utilise a flat (ish) topped piston with the turbo head. There is nothing to stop you using carburettors, or for example a megasquirt with this - but the head is still the weak point, especially the hump in the intake port where the water jacket runs.

Achillies heel two is the valve seats, which are shrunk into the head. Larger ones would be required for bigger valves to be fitted. The valves aren't bad but are very thick and carry lots of weight as well as having a thick stem. Added to this, the valve guides are of good material, but impinge on the inlet port. New bullet nose guides would probably provide a useful increase in flow. If you add a decent bottom end, with everything lightened, and dry sump it, you would end up with a half decent 924 engine - but - again - in comparison to other 2 litre engines, you may struggle for outright horsepower.

Be interested to see how you get on

Martin

[mart924]

Oh yes, nearly forgot, the standard exhaust manifold is very heavy and doesn't flow - best weighed in for scrap! I have no proof, but I suspect a good tubular 4 into 2 into 1 would prove beneficial. However, Ford engines of the same heron head type can work well with a 4 into 1. 4,2,1 for torque, 4 to 1 for outright power.

Martin

[mart924]

Oh yes, nearly forgot, the standard exhaust manifold is very heavy and doesn't flow - best weighed in for scrap! I have no proof, but I suspect a good tubular 4 into 2 into 1 would prove beneficial. However, Ford engines of the same heron head type can work well with a 4 into 1. 4,2,1 for torque, 4 to 1 for outright power.

Martin

[andy97]

Hi Mart

Many thanks for your reply. It won't be me that's doing the work unfortnately (technically lacking) but I wll pass this on. There are a few people considering 924s for the 360 MRC 6 hour race at Snetterton in April, (maybe I'll be one of them but as always it depends on finance) & one or two already race in the CSCC 40 minute Future Classics races where regs are not quite so restrictive, so the mods you mention may appeal.

[gwynsms]

Hi Mart

There are a few people considering 924s for the 360 MRC 6 hour race at Snetterton in April, (maybe I'll be one of them but as always it depends on finance) & one or two already race in the CSCC 40 minute Future Classics races...

Chaps
I know of two 924's being prepared for the 360MRC 6hr race (and possibly other endurance races at Spa & Nurburgring). I'm advising these guys what needs doing and also pointing their preparation mods in a direction that keeps their cars compliant to this championship's technical reags. If they wish, they can then participate in class A,and not get punted into the invitation class. Food for thought for you Andy.....

Cheers
Gwyn
Happy New Year

[andy97]

Just been flicking through an old copy of the Micheal Cotton 924-944 book & in th chapter about 924 & 944s in competition he talks about the "DP 924" used in the US for racing. Apparently they had dry sumped engines, a CR of 11.9:1 and different fuel injection to give 185 Bhp from a N/A 2 litre. Not bad going for the late 70s/ early 80s. I can't help feeling that there must have been more to it than that! Anyone know any more?

Edited to add that i have found this info:
http://www.924.org/models/924D933.htm

[martinhall]

Hi there,

Maybe did see something about this, and from what I remember, the engine was a full race prepared unit with big valves, and maybe a steel crank and rods (getting older, can't remember like I used to!!!) Kugelfische injection was a timed mechanical system, and was used by Ford for the Group 4 Escort BDA's in tarmac form (Formula Atlantic spec). I also saw it on a BMW 2002 which had intakes like drainpipes, massive inlet trumpets and a slide throttle - you could even see the top of a piston with a torch! 185 from an eight valve two litre was not too bad, but for the amount of modification, a Ford, BMW or Vauxhall engine would be on a par or better. Would love to see the cylinder head as the standard 924 one we use is pretty poor from an airflow point of view.

Mart