Why has no one else mounted throttle bodies?

It's a sweet project and has the potential to produce significant performance gains IMO. Don't ask me to prove it as it's not important enough to me to prove it to spend cash on dyno time. The cost is significant with cost of TBs, machining adapter manifold(s), engine management, and plumbing. Injection control, and secondarily ignition control, involve aftermarket systems such as Motec or Haltec if maximum performance is to be obtained since the Motronic systems aren't tunable by laymen. I think today's cost of a decent system would be somewhere in the $5k range.
My goal was to eliminate the airboxes, mafs and ducting under the bonnet and just use old school injector stacks. Once the airboxes and mafs are eliminated, airflow management metrics change signals, eliminating Motronic possibilities. My system works well, albeit with airboxes and mafs. So, I'm 90% there. All (famous last words follow) I need to do is to mount a sensor to read engine speed. Long explanation as to why and where is too long to type. Many suggestions "allyagottadois" have been appreciated but not worked out so far. My sure solution has been more than I've had the motivation to do lately.

 

You'd probably eliminate the motronic for all engine management. The Motec would the be ideal choice, but expensive. My solution is a Haltec for injector management only after mafs removed, using a GM style airflow sensor, but I need independent engine speed with 4 pulses.

 

We stooges have been down this slippery path. The question is more like who has the money to throw at this experiment? I estimated the cost just to find out it there was potential at about $2200 and I was not willing to gamble the funds in this economy. Still can't see the point.

I looked at buying some 355 TBs - that was about $1000 is I got lucky on eBay. Then I needed 355 airboxes at whatever cost. And the fitting of the TBs to the manifold. And possibly new injectors with a higher flow rate.

Or, I was looking at some semi-custom Weber-style TBs - about $1600 and then there's the other things.

Also looked at a custom intake like what group77racing fabricated - about $3500.

Engine management options were several. Stock, intake only or new replacement (smog issues?).

Total it up and its a pretty expensive experiment.

 

The problem will be selling it later and trying to pass smog. You can't make that ever smog legal in cali without returning to stock. And as Vince points out the experiment...it is so much easier to buy a known reliable quantity aka faster Ferrari like a 550M 10 years old and still with modern horsepower to match the Z06 Vettes, CTS-V's, Merc's, and little displacement Ferraris and blow all but a couple of ricers into the weeds. The stock 348 now 20 years old is having trouble with Ford Fusions and Mazda 3's

 

Remove weight. Double bonus....faster and better hancling.

 

There is Fun, and there is MO FUN...... Sometimes a 'little' more weight is OK
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I was going to do it recently, but I couldn't find a set of 355 throttle bodies here in the UK. Those that were for sale were too much £££.

 

Dave has a set that he is not using...lol

 

Hey Vince and Bruce,

Talking about thinks that make power and great noise, when is the 358 doing its next trackday? Weather is cooling and best time to get low laptimes.

 

Eventually I'll get around to unplugging the intake system on my car. These engines need to BREATH, and they can't because the intake and exhaust systems are so restrictive. The throttle bodies are tiny at 54mm if my memory serves me correct. The 4banger import tuning crowd regularly up grade to 65mm tb's. That's roughly a 20% increase over our stock tb's. The intake plenum is also to small, and I'm not a big fan of the dual trumpet tops of the runners. I have had my intake ported, and the runners flow matched. If I remeber correct the flow increase somehing like 24% through the runners. But my tb's haven't been touched yet. Vince got his tb's ported but only jumped 2mm to 56mm, which is still to small in my opinion.

Then there is the issue of the air box, and air intake length. In my opinion it needs a complete redesign. I do like that the air box gets fresh cool air from the quarter window area, but that is about it. The distance the air has to travel before it gets to the throttle bodies is way long. The air being pulled into the air box has to travel through a corrugated flexable hose, then it enters the air box. The corrugation causes turbulence which isn't good for flow or velocity. The design of the air box looks as though it was designed to act as a resonator to cut down on intake noise. Not good for keeping the velocity of the incoming air accelerated that is already messed up from the corrugated hose. Plus the air box is sitting almost smack on top of the muffer/s which gets headed = not good. Hot air is less dense than cold air so the fresh charge of air from the windows is almost a wash. Then the air enters the mafs, which have 65mm openings but travel through the tube which has a sharp turn and reduces to the same size as the tiny tb's.

Then entire intake system needs a redesign = $$$ & time.

As Andy has proven once the 348 can breath properly it can make power. Last I heard he was giving CS's a hard time.

 

A couple of points:

A) If you did get a hold of a set of F355 throttle bodies, you will have to either weld up the TB or port out the heads to port match the 355 TBs to the 5-valve heads.

B) The F355 TBs have 44-45mm throttles per cylinder--equivalent throttle area of 88-90mm throttle for 4 cylinders (ala 348).

C) In track trim one can easily get away with Alpha-N fuel injection (which requires no MAF/MAP and works on pure throttle position and RPMs--however, you have to tune the fuel map every day to keep the engine spot on.)

D) even with freely flowing air into the cylinders, you still have to duck fresh cool air to the intake system to keep it from sucking hot engine/radiator air.

 

please repeat after me... you do not what velocity in airbox in front of the throttle body.

why does everyone here on F-chat assume whats good for the intake tract ie, manifolds, ports, valves, exhaust should be applied to the airbox? you want to increase pressure in the box not reduce it with high velocity.

you do have a point though with doing away with the corrugated hose and the stock plenum may be too small.

 

A) If you did get a hold of a set of F355 throttle bodies, you will have to either weld up the TB or port out the heads to port match the 355 TBs to the 5-valve heads
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To start, I'll say hello. I'm new to F-Chat and F-cars. We started shopping for our first after my wife and I were bit by the F50 GT1 on our Monterey trip a couple months back. I began searching for 348/358..cough, cough.. I mean 355 challenge cars immediately.

I’m not new to cars, only Italian ones. I know the search for more power is universal and the 348 could definitely benefit from additional ponies. Right before being consumed with the idea of owning our first Ferrari I was toying with the idea of an itb’d high compression engine build for my NSX. So it only seems natural for me to jump in with the same passion and ideas to share with the 348/355 community.

So let’s say I’m the guy that is going to step up to the plate. A like-mined, passionate engineer friend of mine and I have already been researching ways to make a kit like this a reality. While in search of the right 348/deal, a lot of the initial conceptual design elements have already taken shape. The idea of a kit like this I believe is in the minds of many here, who like me, see the potential for improvement. I love designing and making things for myself and see this one as something I can viably share with others. I had no plans of mentioning this publically yet, but given the timing of your question, I felt like this would make a fine second post on F-Chat.

Most individual throttle body kits normally have a high $/hp ratio and I wouldn’t see this one as being any different. However, I plan to use the highest quality materials and make it a masterpiece that goes beyond the obvious functional benefits of an itb system.

I can’t give an exact timeframe as we are finishing up a run on a much-needed part for another hobby of mine and both of us are currently taking care of other obligations. This project is next in line.

 

If you really want to have Maximum fun, I reccomend one of these!! (but two is better!!)
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Welcome.......the 348 guys need an adrenaline rush and this may be just what the doctor ordered.

Best of luck on your project.....

 

Thanks.. I know a lot of people don't like to modify these cars but in 20 years you'd think that this would be an available option.

Soon enough..