FUSE69

If you want the intake pipe to sit inside the MAF, just above the screen, then you should use a 3.5" pipe. (IIRC, Max is about 3.58" OD pipe)
I suggest mounting in this fashion, otherwise the edge of the MAF will cause an airflow obstruction.

If you take off the standard airbox you will see that the outlet from that box sit's over the MAF, so that the airflow has a direct path without obstruction.


Otherwise, yeah, as Rob posted OD of the MAF is 96mm.

FUSE69

OK, so i've had a few questions regarding this induction system that I made... so here are a few pointers on what I believe should be achieved to gain the best results....
I am by no means a specialist in Fluid Dynamics.....
So if anyone that does have a diploma or such in Fluid Dynamics and disputes what I have below then by all means please contribute to the conversation...

(that being said, what I do know about fluid dynamics, pretty much tells me that this induction system SHOULDN'T work very well.... but hey... I'm willing to suck-it and see... just have to get back to the dyno)







When I get the chance (perhaps on the weekend) I can probably dismantle everything and take some better pictures of the final product if anyone is interested....

//Ben

Mike Frye

Ben,

That's pretty cool!

I'd love to see how it does on a dyno compared to the stock setup and all other factors being equal.

Mongo

I'm just curious what your intake pressure is with this new airbox setup. There has to be gains here since there are "no leaks" when compared to a factory airbox.

FUSE did you use the sealing ring off the airbox for your MAF / intake pipe to hookup?

PorKen

Ben - sweet rendering!



These filters would be what I'd want. (From prototype engine.)


red line shows vestigal carbed manifold exhaust x-over port on OB heads

FUSE69

Yes, i designed it around the old sealing ring from the airbox... I recently went and bought a new one from Porsche as I discovered they were surprisingly cheap.
I had a bit of a hard time installing it all together with the new ring... it is now guaranteed airtight!

Here the sealing ring to MAF can be seen.

Alan

Ken lots of filter area which is nice but at least 2 hard 90 degree bends on each path - 4 on each path if you count the transition into & out of the filter medium... (but the surface area available there probably negates most of that restriction). It does seem that the rear box transitions could be radiused quite well and I suppose no reason not to radius the "T" to the MAF as much as in the other examples - but it doesn't seem they did?

Alan

Mongo

Damn! Where the hell can I find y-shaped aluminum or silicon tubing at?!

I have googled the entire planet

Mongo

Would using a 4" " tee " cause turbulence?

I found a steel tee that could be used for a merge collector.

dprantl

One thing I really didn't understand is why Porsche would choose such a BAD intake arrangement. Straight pipes going all the way to the firewall to take 90 degree bends, only to take another 90 degree bend into the MAF, then do even more than a 90 degree bend to go UPWARDS (!), then to the sides, only to turn around and go back into the engine. Could it be any worse?? It's no wonder no stock 928 engine ever got better than 64hp/liter, even with the variable resonance intake flappy on a 5.4 liter GTS. They really should have put dual throttle bodies and MAFs, one on each intake box which would mean straight shots with only one bend each into the engine. Kinda like Ferraris of similar vintage.

Dan
'91 928GT S/C

928SS

iirc, they wanted a certian sound, it flows fine for a stock motor and it was easy to yank for accessing the rest of the motor? that's what the porsche 928 book I have says. they even have an exhaust note tuning valve, so sound was a REALLY big deal for them. and most listeners agree that the 928 sounds pretty cool in stock form.

also had to pass smog and get some kind of semi-decent mileage...

the car was detuned cause most drivers would have killed themselves and the insurance would have been unobtainable... speed limits abound too - most have realized that 900rwhp isn't average joe/jane street material long ago.

dprantl

Fair enough on the sound. But to have the car so detuned I don't buy. There were stock Ferraris around with 500hp back then. In '86 the Countach had 450hp as well. Maybe it was the BS hold back the 928 so it's not faster than a 911.

Dan
'91 928GT S/C

928SS

there will always be rumors about that too...

wasn't exactly a slouch - it did set the speed record.

but I suspect the target market was different too, hence the automatics on so many of them. I think of it as the "scarface car". for folks w/$$ to burn that wanted the pcar thingy on the front to get the attention they wanted, but didn't want to figure out that shifter thingy and extra pedal on the floor like the 911's/pasta rockets had. especially when they were usually too wasted or doing whatever while driving.

I got one cause I like the lines, V8 and was hoping to find a ton of $$ under the seats... 2 out of 3 wasn't so bad I guess.

Altharos

Yea all I found under my seat was an empty powerade

inactiveuser1

Also was searching high performance filters for the 928 and found the page at:
http://www.928gt.com/s-3-performance.aspx