924Board.org

[Juho]

I got this idea yesterday when looking at my turbo head, what if i made with my itb manifold small separate intake runners for injector holes, bored injector holes bigger for better flow.

What you think?, my main concern is that this would cause turbulance on top of valve.

[morghen]

Well first thing to mention is that in your picture is a NA head not a turbo head, the runners look different on the turbo.
Second, its no real use to make the entrance larger if the valve itself stays smaller...or the runner just before the valve.

If i remember correctly you're building a high compression NA, right?
I would concentrate on making moving parts as light as possible, maybe do a small porting job on the intake/exhaust ports but not more.
Also i would run larger pistons with larger 88mm bore to increase the capacity to 2.1L
That way you will probably get a 5-7hp gain from the bigger capacity, 5-7hp from less rotating mass and 5-7hp from better flowing head...so in the end you'll be seeing 15-20hp more with an easy to rev engine.
If you also increase the CR of the engine you can probably get another 10-15hp.
The rumor on the internet is that the NA fuel system kind of tops out at 160hp so keep that in mind as well.

I was contemplating this exact recipe before i went with the supercharger idea.
I abandoned the hot NA idea because the price would probably be more than 2-3000 euro and the character of the car would not change much.
Basically it would still feel like the 924 but with a bit more power on the top end.
I wanted a bit more spice for less money...also i may be old but i kind of wanted the car to go quicker without making so much noise...so the instant extra torque of the supercharger made sense for me.
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https://www.the924.com

[Juho]

[safe]

Use the injector port for injecting fuel... If you would want to inject in the TBs, fill the ports with epoxy. Smooth air flow is key.
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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe

[Juho]

you dont think this would result more air in the cylinder?

[Cedric]

Could work, but could also disturb the flow that comes along the wall. It's not something i would just throw in before evaluating it in the flow bench.
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1980 924 Turbo
www.instagram.com/garagecedric/

[Juho]

Im trying to create "simulation" of this in fusion 360 to see if theres point, Just trying to toss around ideas to get more power with na setup

[safe]

How would you get this extra runner from the TBs?

I think you can make improvements with making the port straighter towards the valve, but that is a huge amount of work.
Also not sure that the port is that restrictive in size, it more the bends in it, the valves are quite small too.
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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe

[Juho]

[Juho]

[safe]

[Juho]

i find it way more fascinating chasing more power in na, also the car is goint to be a track car and i want it to be more simple and reliable.

[MikeJinCO]

I agree with Morgan on getting the reciprocating parts lighter, both Mike9311 and myself are working on that. The only person who has gotten the NA head to flow much better is Gegge. I found and Hayes Lewis would confirm that the stock NA head tends to stall on flow at a little over .400 lift. Hayes is working with some cam grinders to make low lift cam for his race car. I think a duration range of 280- 285 degree with a .425-.450 lift would really work well. My testing on a 931 head showed it worked better(and higher overall) up to .450, but it almost flattened at .500. One thing to keep in mind is that with our Audi gearboxes, you don't want a long duration cam/small power band as the motor drops about 2000rpm between gears. Apparently the Euro Audi 5 speed has a bit tighter gearing than the US box.
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Mike


'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild)

[Juho]

Should i remove these ridges when porting my 931 head?

[safe]