924Board.org

[Arvidw]

Crap, that's why it didn't work. According to this webside it should be pin 11 http://www.dainst.com/info/edis/edis.html

Anyhow, i've fixed it quit differently: I used the tach-out of the MS2 to switch the coil of a relais on and off. (other side of coil connected to 12v). I connected the tach input to the same wire as the tach-out of the MS2. Because of the "coil capacity" it creates high voltage spikes when the MS2 disconnects the ground. This spike is caught by the tach which converts it to rpm. Works perfect, and I hope it will be doing that for all the miles to come


I'm afraid i'm having troubles again with my FPR. I didn't change anything in megatune the last couple of miles but for some reason it is getting richer and richer. (from AFR14 to AFR13 when Idling in last 50km when car was fully warmed up) I'm going to lower the fuel pressure upto the point the AFR = 14 @ idle and see wheter it changes again in the miles to come. Maby it is because I added injector cleaner and it actually works? Sounds too good to be true to me though

@Morghen, Thanx. I didn't intend to keep the original look however I'm quit pleased with it now. With the 53mm throtle bod, original air hoses and air box I can stil get 96kPa manifold preassure at 6500rpm which means there is only a 4kPa drop caused by the inlet hoses and filter which I think is not that bad

@Scorpio, i don't think a lot of EFI people are going to agree but I think that CIS is not that bad after all on a original engine. The benifids of EFI over a properly tuned CIS system are not that big and my EFI conversion cosed around 800euro's which I find a lot. It will pay back when I stick a supercharger to my engine however that is going to take a while...
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Porsche 924 2.0 Kompressor 136.1wHp @ 5650rpm / 201.9wNm @ 3900rpm (dyno @ dp-engineering.nl)

[Arvidw]

My new exhaust, constructed by Twan from jeroentjetuning.nl (with a little help from me, unfortunately my job consisted mostly of the removal of rusted broken bolts )

The downpipe is modified at the collector to go from two 49mm pipes to one 60mm pipe. (instead of the original 50mm diameter)


The exhaust is constructed from 60mm pipe with 2 freeflow mufflers:






It sounds great, it is "a bit" more noisy than the original (especially when you floor it). It sounds a little bit like a tuned japanese car, very strange but funny.

But the best thing is that, beyond my expectations, the car feels more powerfull I also "tested" it on a road where I know how fast I can accelerate. This sprint resulted in a higher speed than I ever accieved before. I am going to compare datalogs from before and after because I'm flabbergasted that it actually worked
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Porsche 924 2.0 Kompressor 136.1wHp @ 5650rpm / 201.9wNm @ 3900rpm (dyno @ dp-engineering.nl)

[Mike9311]

I can tell by that 2nd pic from the top that is nice work (grafting from the old to the new). Nice!
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1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[morghen]

looks great, i just run a pipe...sounds AWESOME...something like a subaru(because of the turbo) but more metalic(924 trademark) noise.
unfortunately its VERY stressful to drive such a noisy car and i can only cope to a couple of weeks before i swap back the original exhaust.
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Supercharger and EFI kits
https://www.the924.com

[bnoon]

I don't imagine that many 924's get the privilege to wear a custom TIG'ed stainless exhaust system. Nicely done!
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'80 924 Turbo - SOLD!
1986 Porsche 944 Turbo - SOLD!
Porscheless

[RC]

Awesome looking exhaust system. I`m envious!

What mufflers are those you used? Appear much better quality than the Powerflow SS ones.
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World`s quickest 924 2L slushbox

[Arvidw]

@morghen, a straight pipe you must be slightly mad Damn, I can't even imagine how much noise that is going to produce, expecially with the pretty high exhaust pressure a 924 engine creates.

@bnoon, Indeed, the best viewpoint of my 924 is now underneath the car

@RC, I've got Belgium mufflers but I don't remember the brand. My search on google didn't help either. The ony thing I do remember that the mufflers aren't cheap. 75euro for the round muffler and 120 for the endbox. If you really want to know I can ask Twan?

I think they are worth every penny because they are completely TIG welded and the 63mm pipe runs (partially perforated) trough the entire muffler (so no perforated steel midsection).
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Porsche 924 2.0 Kompressor 136.1wHp @ 5650rpm / 201.9wNm @ 3900rpm (dyno @ dp-engineering.nl)

[fiat22turbo]

Arvid, Morghen has a turbo car, the turbo loves low back pressure after the turbo and the turbo itself acts as a bit of a muffler as well.

On my other turbo cars, I've run 3" exhaust pipe with just a fiberglass packed "muffler" and a catalytic converter and it passed the noise (95db at 50 feet) and emissions for the local motor vehicle department. It is a little loud if you get on it, but as long as the exit is turned down, the noise isn't as bad since the ground disperses/redirects some of the sound energy combined with the muffler to help remove some of the noise from inside the cabin. Unfortunately, the fiberglass packing eventually fails and the noise gets too loud, and I've not found a solution to this that isn't overly expensive.

On my $500 turbo race car we had to meet the same noise constraints and ran a 2.5" exhaust system with a glass pack and a side exit. Never had a problem with noise for the entire 24-hour race, unlike many of the other Non-turbo vehicles. Car sounded pretty awesome since you could hear the turbo spooling.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[RC]

[Arvidw]

After the pipe dipped underneath the stabiliser it stay's nearly flat to the floor of the car. It is in fact tilted just a fraction upwards however I guess that it is no more than 5-8degrees.

We started out with a 90degree bend and for the rear section we chopped it in half creating one bend slightly smaller than 45deg and one slightly larger than 45deg. The deviation won't be much more than 2degree btw. The smaller bend was positioned near the muffler and the larger bend was near the TB-tube. I think two 45degree bends will work fine, this was our intention however the saw table wasn't cooperating

The "s-bends" near the centre muffler are in fact just 90deg bends cut in half and than welded up again.
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Porsche 924 2.0 Kompressor 136.1wHp @ 5650rpm / 201.9wNm @ 3900rpm (dyno @ dp-engineering.nl)

[RC]

Thanks for that Arvidw.

Good idea just cutting a 90* bend in half to suit. Will make a parallel offset and work out to half the cost since they`re often the same price as a 45*.
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World`s quickest 924 2L slushbox

[Arvidw]

My current cilinderhead is a little bit ruined by one of the previous owners of my car.

Some genius adusted the lifter to cam clearance by sanding the adjuster screws with a belt sander.


Unfortunately the worst part is still te come, he inserted some of the adjuster screws the worng way round so some of my valvestems are chamfered.




I already have bought a good NA head however I'm having doubts about making it a big-valve head with Ideola's kit.

Does it make any difference with my current setup, all original except for:
- Webcams 257dg camshaft
- 2.5" exhaust
- Megasquirt-II injection & ignition

Is it a modification many head machining shops can do, I mean are they going to complain about the limited space between the valve seals?
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Porsche 924 2.0 Kompressor 136.1wHp @ 5650rpm / 201.9wNm @ 3900rpm (dyno @ dp-engineering.nl)

[Martijnus]

[Arvidw]

I don't expect it to be cheap however I don't have a clue in what price range I should be thinking: 300, 500?

The 2.5" exhaust is in my case better, the preformance did improve over stock. (and I needed a new exhaust anyway)

The thickness of the adjusterscrews are indeed quite important, in my current cilinderhead I've ran out of the adjusting range on one of my valves. The valve clearance is only 0.06 too big but i don't like the Idea of being a the adjusting limit )
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Porsche 924 2.0 Kompressor 136.1wHp @ 5650rpm / 201.9wNm @ 3900rpm (dyno @ dp-engineering.nl)

[Arvidw]

Yesterday I took appart the spare cilinderhead. For the removal of the valves a special (and very cheap) tool was neccessary.



Yes, it is a 3euro glue clamp with some metal studs welded to it and it worked like a charm







Now I have a disassembled head and I spotted some improvementpoints:
- Match intake and exhaust header to block (eventually with allignment studs)
- Remove mold parting line ridges (pic 1)
- Improve flow slightly by enlarging inner radius (pic 2 & 3) This is quit rubbish now, the radius is nearly 0
- Smoothening of the sparkplug cutout in the head. Removal of sharp edges like the excess sparkplugthread (pic 4)
- Smoothen transistion between valveseat and head. (pic 5)
- More modifications neccessary? Please reply

To compensate for the loss of material in the combustion chamber I'm planning on buying a slightly thinner head gasket. I'm dropping the idea of the bigvalve head.








I've alway's done my own tuning with my 2stroke mopeds so I do already have good mills for the dremel grinder. Unfortunately these are too small for this job so i'm planning on buying these products:




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Porsche 924 2.0 Kompressor 136.1wHp @ 5650rpm / 201.9wNm @ 3900rpm (dyno @ dp-engineering.nl)