6.0-928S

Hi All,
Does anyone have any experience or knowledge on the feasability of using Weber 48 IDA's on a 928. Hood clearance issues are not a concern.
(fabricationg is a disease!)
Thanks, Hammer

sublimate

http://www.thedeathknight.com/928/928_Carbs.html

Robert_H

How about these on a 928 ?

6.0-928S

Yeah Rob,
I spoke to Inglese today. Trying to get as much backround info that I can before I do this! Although I'm not looking for all the bling in your photo!
Hammer

Jim bailey - 928 International

It is probably much better to go to individual throttle bodies and aftermarket fuel injection, The weber carbed cars (stock hood) had issues with boiling the fuel in the float bowls when you parked it hot. Plus in hard cornering Webers tend to sputter as the float bowls shut of the fuel. There has over the years been a few weberized engines, I will admit to having 4 dual throat webbers 44IDAs in a box at home.

Normy

I don't think Webers are any substitute for a good FI or engine management system...but GAWD do they look good!

N!

Drewster67

I hear there is a definite improvement in HP and TRQ over FI. Dunno is this is solid or not.

6.0-928S

I have had Webers in the past (427 Ford) & I don't think I would lose anything to the fuel injection. It made great power & torgue & the throttle response was much crisper than my stock fuel injection. I felt they were easy to tune, & would adapt to cam, timing & mechanical performance upgrades. I'm an old hot rodder, not an electrical computer wizard. I just spent over 2 grand between 3 shops (including the local Porsche dealership) on driveability concerns & I still have problems & no one has the answers. If I could tune it myself I'd have a lot more fun with it. Just kickin' around ideas in my head as I get ready to install my stroker motor. The long block is set but I have to decide which way to go for an induction system. The stroker is ported & has the 968 valves, & will have bigger cams so I can't just drop it in with the factory FI! Must tinker...must tinker....
Hammer

FBIII

Do a search here using "928 carb" and the fourth posting down will be an ebay listing for a 928 with 44's on it. You maybe able to contact the seller I think he also was selling the setups. I never heard of or experienced Webers sputtering in the turns. I had 45 dcoe's on a DB4 and IDF's on an AMV8. They were always the carb of choice for serious road racing.

slate blue

This is what I'm using, you can remove the secondary throttle if you like. They taper down from 65mm to 42 mm which perfectly mates with the 2 valve head.

dr bob

I'd have to go look through the storage bins to verify... I think there are 8 each 38, 40, 42 and 44mm chokes out there for 48IDA's. Part of a BIG box of tuninig and go-fast bits I've paid for storage on for about long wonderful 30 years.

Meanwhile, the individual throttles and sequential port injection make a package that's a LOT easier to tune. More than a few folks claim to be good Weber tuners, only a few can make smooth power with them. Too often, peaky performance is mistaken for best performance. Reality is that surging in a corner can be fatal, and a peaky motor is no fun to drive on the street that's for sure. Many remember the big whooosh that happens as the throttles open too fast, the fuel charge goes lean and clings to the manifold walls for a second or two before it flashes off to a momentary over-rich condition before finally settling down. That whoosh is a power lag, mistaken for a power surge.

Anybody else have multiples of IDA's in their past? Anybody run the 58's on the 2 liter flat six 911 motor when the einspritzen didn't? Ahhh, the good old days!

FBIII

Bob are you sure your memory isn't getting a little fuzzy after 30 years? Sounds like to me your describing an old Holley four barrel. What I always marvelled at was the crisp throttle response webers have.

dr bob

Depends on the rest of the engine you are putting them on. Carrol S. liked to put them on the cobra 289's, so every sports car 'racer' with a 289 had to have them. With 44mm chokes of course, when 32mm chokes would have produced the "crisp throttle response" you remember. 48IDA's are way overkill for any of the small breathers. But they do look cool, especially with polished stacks. To make them work well, you need to have a free-breathing engine underneath.

For those reading at home, the IDA series features no cold-start enrichment, but has darn near everything else adjustable/tunable. And that tuning, at least the "changing things" part, is very easy. All the jets and emulsion tubes are assembled into a stack that inserts from the top. So except for removing a screen cover, you can get to them with no other disassembly. The primary and secondary venturis (chokes) are changeable from the top after removing the inlet bell (a couple 8mm nuts) on the hole you want to modify. The only thing you cant get to from the top is the accellerator pump cam. Good or bad, each cylinder can be/has to be tuned individually.

I've done more than a casual amount of Weber tuning on lots of cars. My favorite was my 246GT, with the stratos heads and intake. Three 48IDA's on a 2.4 liter V6, what a sweet song right behind your head! A bit of work to drive in traffic, and a --chore-- to get started again after a hot soak. Cold starts no problem, but a hot soak boiled the fuel out of the bowls into the intakes and cylinders. Ahhh, the good old days...

docmirror

I have a modest amount of background with Weber carbs on various cars, but none on the 928. I would not recommend the Weber for anything except vintage class cars where originality or 'bling' is desired. The were the cat's meow in the '60s, but modern FI is more than a match for any carburator.

Someone mentioned crisp throttle response and someone else seemed to see the opposite. Here's what happens: There are 4 basic circuits on the vertical Weber. Idle, mid-range, main, and accelerator. Where folks get into trouble, is from the idle to the mid-range circuit. They overlap, and are active in much of city day-to-day driving. If the idle jet is sized wrong, it will either generate a rich condition, or a lean condition at somewhere between 1700-3000RPM depending on MP, cam timing, runner length, diameter, etc. If you open the throttle plate, and look just upflow from the idle screw, you will see four staggered holes in pattern. These holes are the transition, or mid-range circuit.

Idle jet too small, and the car will 'pop' and hunt in transition. Idle jet too big, and the car will lug, and blow a puff of black smoke in transition. Accelerator pump can mask these symptoms, so I usually block it off with a BB while adjusting. There's a bunch of other things that can make or break a Weber setup, and if you don't have a box full of jets and tubes, you're just guessing. Every installation is different, and if you change altitude, or temperature, things change again.

Other issues; Reversion, if the intake runner is small, there is a start-stop effect in the carb throat and throws off the stoichiometry, but makes for that beautiful Weber howl! Idle synchronization. Get a Uni-Syn gauge, and learn to use it. Fuel pressure too high, Webers like 2-4 PSI at the bowl, that's all. Float level is very critical for driving in the twisties. etc, ad infinitum. Just go here and buy the TEC3:

http://www.electromotive-inc.com/

My most challenging was getting a Lambo Muira running right with four triple IDFs. What a be-atch. I spent days......

Doc

Jim bailey - 928 International

FBIII .." I always marvelled at was the crisp throttle response webers have." the question then is compared to what ? My old 911 race car ran Porsche Mechanical fuel injection with individual throttle bodies after An excursion to 10,000 RPM or so ( shifting at 8,500 rpm to 5th driver found third) I borrowed a weber carbed engine for the next event. Although a bigger motor and admittedly without a lot of tuning it "baubbled" in the hard corners this was a 2000 lb 911 on 12 inch slicks. Dr Bob has a lot of experience with track cars and weber carbs. There has also been more than one 928 running around with a big holley 4 bl grafted to the intake plenum !