924Board.org

xpernet · Posted: Thu Nov 12, 2009 3:22 am Post subject: Modifying Intake for ITBs

I have a set of GSXR750 throttle boddies sitting that i want to fit into the car. I was thinking of 2 options:

Cut the stock plenum to match ITBs and flip upside down, so they are pointing up rather than being horizontal. Reason is i need alot of space for my supercharger to sit there... Would that have any adverse effects?

Or

Make one from scratch using fiber glass

what do you guys think?
_________________
1977 Porsche 924
Sunroof Delete
Megasquirt II EFI & EDIS
Carrera GTS / 944 Body

"If one does not fail at times, then one has not challenged himself." Ferdinand Porsche

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

I think it would be easier to get a weber carb manifold. Contact Jorge at European Motorworks. Or get one from Extrudabody.
_________________
erstwhile owner of just about every 924 variant ever made

xpernet · Posted: Thu Nov 12, 2009 3:52 am Post subject:

... But that will take all the fun out of the fabrication process... and im on a really tight budget now lol

Now that doesnt mean im going to do a shitty job lol...

If the intake was sitting upside down, would that affect air flow into the engine since its not sitting horizontal... Or wouldnt matter in a FI application?
_________________
1977 Porsche 924
Sunroof Delete
Megasquirt II EFI & EDIS
Carrera GTS / 944 Body

"If one does not fail at times, then one has not challenged himself." Ferdinand Porsche

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

In that case, making a fiberglass one would be less grief. I think you'll have a difficult time cutting the runners midstream and getting them to interface with the ports and match the required spacing for the ITBs. On top of that, we already know the angle of entry on the stock intake runners is really bad, so why not improve on that while you're at it.
_________________
erstwhile owner of just about every 924 variant ever made

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

The only concern I'd have with making one from 'glass would be heat and pressure related. I would do some research on what resins and materials one should use with that solution.

Ross Machine might have some parts and pieces that could help you make an intake out of extruded aluminum without the hassle of welding cast aluminum.

http://www.rossmachineracing.com/

Good luck and let us know how it comes out!
_________________
Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

Rich H · Posted: Thu Nov 12, 2009 7:10 am Post subject:

Proper choice of resin is important but it won't be a problem in fiber glass.
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

Martijnus · Joined: 29 Dec 2006 Posts: 2019 Location: Netherlands

I made my current runners from stainless steel. That's a pita to work on because it's so hard and tough, just like me.
I made them straight (just like me), but that meant having to space the throttle bodies.
No problem there, but on my next intake I'll do it different.

I'm planning to use fiberglass too. Should be able to do the trick. Has to be fuel resistant and deal with the temperature, but I've measured temps recently and the hottest I measured was 80C at the first cylinder.

So that means the intake won't be hotter than the coolant and I've seen specs of resins which cure the best at 70c, so that's great

I wouldn't flip the stock manifold. I've thought of using the stock manifold too, but if you cut it half way you end up with non-equal length runners. Not a real problem, but I wouldn't like it.

Besides that, if you flip the manifold, you've got a problem with the studs
_________________
"Rule: Turbo's make torque, and torque makes fun." (C. Bell)

924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

N/A it shouldn't be a problem since the air will be fairly cool and it will only see vacuum.

However, he's planning a supercharger, which in most cases cause excessive heating of the incoming air (usually more than a properly sized turbocharger)

So even with a charge cooler of some type, the intake charge will still likely be quite a bit warmer than ambient and when combined with the pressure in the intake it can cause it to fail.

Not to dampen the enthusiasm of the project, just didn't want anyone to miss some critical information in the planning stages.
_________________
Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

Rich H · Posted: Thu Nov 12, 2009 7:46 am Post subject:

Fiberglass can be very heat resistant if the right resin is used. Epoxy resins would probably be better than polyester and the strength is down to the design not the material.

Properly chosen epoxy can take temps over 150 deg C.
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

Martijnus · Joined: 29 Dec 2006 Posts: 2019 Location: Netherlands

if your intake temps will exceed 80c I'd do something about that... especially with a charger you're really screwing the efficiency that way. You're using power from the crank to heat up your intake temp, you can't get a proper ignition timing and you need to enrich the mixture a lot because of those high temps.

gone is your energy

my intake temps usually aren't that high, but in traffic jams etc they exceed 50C...which is quite a lot. Engine runs way smoother when the intake air is hot... but it's not the best for power. Be sure to design a cold air intake, the temps under the hood are high real quick.
_________________
"Rule: Turbo's make torque, and torque makes fun." (C. Bell)

924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment

xpernet · Posted: Fri Nov 13, 2009 2:03 am Post subject:

Thanks for all the replies guys!

Ill be hooking up an intercooler to keep the temps down... ill start posting pictures when i start fabricating to keep you guys posted!

Anyone know of a good source for Silicone Couplers other than the internet??
_________________
1977 Porsche 924
Sunroof Delete
Megasquirt II EFI & EDIS
Carrera GTS / 944 Body

"If one does not fail at times, then one has not challenged himself." Ferdinand Porsche

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

Your local large truck repair shops use large pieces of heavy duty rubber radiator hose. They might have some scraps available that you can use.

While not silicone, they should do the job. I've used them before on other turbo projects and they've held up fine. They are fiber reinforced and about 1/4" thick wall and are reinforced.

Alternatively, browsing the radiator hoses at your local parts store might get you some cheaper pieces of hose. Again, they have come in handy on various turbocharged projects over the years.
_________________
Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)