IcemanG17

I know many 32V strokers have had great success with ITB's.....many getting close to 100hp/L but has anyone made an ITB for a 16V engine? I would imagine its easier, since each intake port has its own bolts..... Sure the Euro S intake flows pretty well....but ITB's have to be better.....especially with a stand alone fuel-ignition system that runs a MAP sensor....

Mongo

I was working on a set for a 944 I used to own a while back. Basically, it was a set of 2003 Suzuki GXR throttle bodies. The tapering on the inside was shockingly just 1mm smaller than the original intake ports on the head of the 944. Since the same heads were installed on the 928 (give or take a few internal differences), you may be able to fab up a system and incorporate an EFI such as TECGT. I

IcemanG17

I have seen systems like this made for VERY little $$$.....just find a wrecked bike in the junkyard and your good......I figure I need around a 45mm ITB....since the stock intake runners are 40mm....

Mongo

I don't recall the diameter of the TB before it tapers down. That would have to be researched. However, there are universal kits out there that offer that size IIRC.

Check out www.extrudabody.com

Jim Morton

... look at Jenvey's offerings.

For the 16V with the pieces below the spider intake, Jenvey offers some "bike-like" throttles. Next problem for the DIY-er is properly executing the needed linkage and air inlets.

Mongo

I wish I brought those throttle bodies up with me from SD. You could have a look at them and do some measurements. The GXR ITBs work great with the 8-valve heads. There was someone in the 944 forum that did the conversion for a track car and loved the throttle response. I don't know what it did for HP though. That car was really light so it was probably fast already.

BPG_Austin

A local 911 buddy built an ITB setup out of motorcycle throttlebodies. Great response, engine performed better in the high rpm ranges. I'd love to see a 928 application and expect similar results. Its on my list if I ever end up with a 16v project.

IcemanG17

I looked at them....lots of options....

Bummer is they are "british" prices....$300 each end up at $2400....not exactly within my "limited" budget.....

I figure my $$$ is best spent on aero and driving.....243whp in a 4.5L is already a record.... But ITB's just is SO sexy......one day when I have the $$$ to do it right.....proper intake-cam-heads-exhaust....all built as a system together.......that will be plenty of power for me!!!!

Next year sounds much better to me.....budget will be there....Doc Brown clutch-transmission.....+???

Billet cams, done right with proper head work.....I will give you a call!!! A 5.0L bottom end and the right 16V head to fit....it will be lots of fun

Jim Morton

just fyi... not to rain on anyone parade... but don't discount the real cost of all the "little stuff" past buying / sourcing a set of throttles. Even if the ITBs are free, getting a working system is still $$$. Been there, done that !

Sometime, bring your 243whp around and let see if it's "real".... hope so... there been lots of recent conjecture about MCE's dyno tests after the last couple of NorCal GTS races.

123quattro

I wouldn't doubt 243whp out of a 4.5L. I did 272whp with a 4.7.

justaguy

Brian
Sounds like a fun project but Don't under estimate the time required to sort out the things Jim has mentioned.
Mike S. already has Itbs figured out for a 5.0L you just need an engine complete with the 32v heads.
So get a good used 5.0 32v from Mark and add Mikes itbs. Should be good for 400 hp. Using headers and your programable ECU

Mike has a set of Itb's built for me. He's just waiting for time between real paying day jobs to rework the throttle plates. To make a tighter seal when closed to give a lower Idle RPM. I have a 5.0L engine built c/w 968 valves and modified cams/ported heads. etc ready to accept the ITB set up when Mike gets a chance to complete the ITB throttle plate modifications.
My goal is 500 Hp at the crank with a programable ECU.

danglerb

If your goal is see what sort of HP you can make, why bother with throttle bodies? Make some simple tubes and plug them with a cork, make some idle circuit maybe with a hose in the cork, let the engine warm up and pull the cork for a dyno run, cut the fuel injection at the end of run and put the corks back for the next one. Work out the details, then worry about throttles.

brianrheffron

I don't know much about the tuning scene in the US
but here in the UK the use of motorbike "constant depression"
carbs on cars is all the rage. All sorts of engines up to 2 or 2.5 litres
are being converted with one carb per cylinder and with very good results.
The supply of bike carbs seems plentiful and they are not too expensive.
Several companies can supply manifolds for popular cars that make the conversions easy.
A 2 litre four with a cylinder volume of 500 cc is not that far away from a
928 with a cylinder volume of 625 cc. It would seem to be a cheaper,
simpler conversion than fuel injected throttle bodies and no electronics to
deal with either. Link is to a typical magazine article.
Beyond my skill level but someone might want to give it a go.

http://www.totalvauxhall.co.uk/files...BIKECARBS1.pdf

dcrasta

Wow Why didn't I think of this years ago lol. 40Mm flatslide Mikuni carbs would sound so sweet!

danglerb

Local guy with webers said it sounded like a pack of motorcycles.