924Board.org

[Rick MacLaren]

Well this is the point I've been harping on Bob, namely, that there have to be decent grinds for these cams given that the 911 turbo and 944 turbo are known for being 'cam'd' once guys really do up the engine. I have a pal with a 911 turbo that has a stage 1 grind and you can totally feel it.

[Zuffen]

well if there is a series of cam profiles worth looking at, the old euro car and Panos mags should tell .

I know there were several aftermarket cams for the 924 ...the turbo on the other hand was so limited that the factory is the only source for that info. Of course what may work for the 924 may work for the turbo

I would think a good tuner with a Dyno can help solve this issue of the best cam profile.

but as far as I know on the 944 the performance gains are in rechipping the dme.

As for the 911, 25 years and VW bugs have helped work those engine out.



I still think the best thing to do is convert the CIS to a modern fuel management system and then go from there

[ This Message was edited by: Zuffen on 2002-01-03 16:34 ]

[Peter_in_AU]

totally agree with Bob (as usual).

Think about it. What are the major differences between a '70's Porsche turbo'd engine (931 or 930) and a modern turbo'd engine?

More cams? Yeah but as long as there are enough cams to open all the valves then so what.

More valves? Yeah, lotsa valves make a difference on a NA engine but the percentage gain on a forced induction engine is much smaller.

Higher compression? The original Porsche 930 and the 924 GTR ran at 7:1 now that's positively agricultural 9.0 or 9.5 to 1 is standard now. Why?

Higher boost? The little tech spec book rates the Euro 931 at a max of 0.73 bar and the Carrera GT at 0.78 bar (reasonably standard factory boost levels today). The US 931 was only rated at 0.47 bar but that was probably because the US was pioneering unleaded fuels and the early stuff was total crap.

Better turbos? Modern factory turbos hit full boost at somewhere around 2000rpm compared to the 3500+rpm required to get the old ones working. But because the factory boost is still limited to around 0.75 bar then you don't get more power, you just get it faster.

What else? Higher tolerance manufacturing, better fuel (yeah right) more anti-smog gear?

OK, you know the answer. It's engine management. Not just distributor-less ignition, not just electronic fuel injection, not just MAP sensors or MAF sensors or intake temperature sensors or knock sensors but the whole lot. Engine management allows you to make everything wilder; more boost, more compression, more ignition advance. Basically the right amount of fuel mixed with the right amount of air ignited at the right time.

If you remember the mid-80's (one of my favourite decades) you might remember such things as the BMW/March IMSA GTP cars pumping out 800hp from a 2.0 4 cylinder or the BMW 1.4 liter Formula 1 qualifying engines making 1400hp and the 1.4 race engines making 1100hp and doing it for almost 2 hours (reliability was a bit of a problem in the early engines). And the thing that made them possible was the engine management, without that the engines would have been dust in microseconds.

Oh, and I didn't mention intercoolers because they will wake up any forced induction engine, old or new.

If you're serious about getting modern power from a 931 then you need to use modern stuff, EFI, turbo, air metering and a programmable computer. And when you add up the cost you'll probably find it cheaper to bite the bullet a buy an EMS that does everything rather than buying an ignition controller and a fuel controller.

Peter in smokey Sydney A

[data]

Why are you guy's so interested in the gtr cam any way, I have a 924 gtr that i race in PCA and a gtr cam does not idle well below 1400 rpm and is not streetable. It would be a waste with the small turbo ( k26)
and standard manifolds. The factory engine actually have the least amount of horsepower
of this genre. The most powerful engine i have encountered made 680 in sprint mode and 540 in race trim. These engines had 2 cooling systems ( seperate for the block and head) but a crude fueling system and very little management.
Talk to steve gruenwald @ integral cams 507-645-9308 about a street cam.
A good cam is only worth 24-35 hp the advantage being to put the power curve highier up the rpm scale for track use or hard street driving. With your 931 add a intercooler 1 bar of boost and get rid of that doofy epa 931 gearbox ( use a 944 box)
and that bitch will move.

[Zuffen]

What chassis Number are you running?

And where are some pics on this beast?


_________________
Bob Dodd
14 Porsches and counting.
6 931 two of each year, including a 80S
3 924 77,77,80 all for parts
4 944 82,84,85,86 all for parts
1 sad 912 for parts

[ This Message was edited by: Zuffen on 2002-01-04 14:08 ]

[Zuffen]

Guys see how this string is progressing.

We all need to work on effectively adding a modern engine/fuel system to the 2.0 block.



_________________
Bob Dodd - 924turbo@cox.net
931 1982, 944 1982 euro, 924S 1988SE, 93 968 tip 06 Silver Cayenne S, 06 Black Cayenne S

I have Way too many cars, parts for the 931,944 and 951

[Rick MacLaren]

Peter: Agreed. Electromotive's site puts a lot of engine management into perspective. Well explained and documented. I'd like to try for an Electromotive system when I get my next semi annual bonus from work.

[data]

Hey check this site for Electronic ECU
for a conversion to efi
http://www.dtafast.co.uk

[Rick MacLaren]

That site is excellent.