How about 550 throttle body on 348 project?

I got a question for you smart guys. If the whole deal with the 355 TB's on the 348 is about getting more airflow, why not do it easier by using a larger 550 TB's and hog out the inlet to the 348 plenum and bolt the 550 TB's on with a spacer plate? This would be much easier than using 355 TB's and for sure the 550 TB's can flow some air. This can be done with 550tb's or mustang or C5 corvette units for rediculosuly cheap and they are available everywhere. Plugzit took over 1 year to find his 355tb's. I do not think the 348 plenum is the flow restriction and if you wanted to make it better you could plate the USA 348 plenum to be like the taller IMSA 348 plenum for more volume. This would allow you to maintain all the 348 action like the vaned intake plenum for the better lowend throttle response. Mike, Group77,NO Doubt what do you think? Plugzit will you let me butcher your 348 intake plenum? Lets run the second project on my car and see what happens?

 

It'll work, no problem. Get busy buying parts!

 

O.K...if you are selling your 348 plenum I'll try it. There is a guy selling some 550 TB's or I can buy cheap C5 vette TB's that are just as big but cheap. I'll give it a try and then have ND burn some chips. I'm going to buy a wideband O2 unit so we can test both our rigs a bit more reliably. Is your machinist friend up to 1) making me two plates to make the larger TB's to the plenum, 2) hoging out the 348 plenum to max size or doing a cut off and re-weld a mounting boss for the bigger TB's, 3) making a spacer to increase the 348 plenum volume. What do you think?

 

I'd say your approach to the size of the plenum would have a lot to do with the size of the TB. Emersum bigol throddlebodies, bubba! Why doncha jis use my plenum n replace it with yours when yer dun? Man, I sure am comfy unner this tree in the shade, ainchoo? I'm excited, good project!

 

Already being done, however, the rest of the airflow parts will need to be tested to see which is the next limiting factor. I'll post pics when its time. Also, any larger TB will require the 348 plenum mount to be cut off and a new larger one welded on, its just easier that way. Again, I can't stress enough, you need larger injectors.

 

I was thinking the same thing Billybob.

 

Sounds good!! Though tunning will still be the 800 lb elephant in the room. When is the installation party??

 

Soon as some one buys the TB's I guess.

 

Yep, it's a stooge call-to-arms!

 

Did you do this conversion? Larger injectors is not an issue. In fact I think it is a waste of time to rechip without having the proper injector sizing otherwise you end up remapping the chips all over again. Did you fashion a plate from the larger TB to the smaller 348 TB mounting area or did you open up the 348 TB mounting area? Plenum mount = TB mounting point???? Whose TB did you use? Do you think there will be a throttle response issue due the the fact that more air may flow but flow slower? You can't run a car with an infinately large TB....

 

I'll probalby buy this guys 550 TB's unless he wants blood money. If so then I'll use corvette FAST90 tb's so if this project is a bust I can at least put the hot TB on my Z06.

 

Right. The horns from the intake plenum down to each cylinder would seem to me to still be the limit, though I don't know that for a fact.

What I like about Plugzit's 355 tb mod to his 348 is that he is placing the tb's as close as you can get to the cylinders...whereas just mounting larger tb's up on the 348's intake plenum leaves them 8 inches or so above the cylinders where the air still has to travel down the horns.

But...if the horns aren't the limiting factor and if it doesn't make that much difference between having tb's close or far from the cylinders, then going with larger tb's up on the intake plenum would surely be a faster and cheaper mod for 348 guys.

Worth looking into, anyway. So FBB's got a good idea. Let me know how I can help.

 

this is how I stay busy during winter in Wisconsin. Did the 30k major plus;

Hill tensioner bearings
Hill Viton cam seals
Hill Viton cam o-rings
Red wrinkle stripped off cam covers and repainted smooth Ferrari red
New Ferrari nuts and hardware
New waterpump
New thermostat
New Kevlar dual disc clutch
New 14 inch brake conversion 13 inch rear
No smog junk
2 65mm throttle bodies
2 75mm adjustable Air Mass Meters
Custom breather system
Dual wideband air/fuel meters with data logging
Custom intake manifold
Custom airbox
Custom exhaust from headers back
Euro 355 bumpers front and rear
New 355 grill, fogs, and euro corner lamps
Rear deck getting sprayed all silver to rid the black area

still have to cut holes in manifold for 30# injectors, mount IAC valves, fab linkage and get ceramic coated.
Should be running by end of March, then dyno time....
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Alright! This is going to be FUN!

 

What would you think about 2 giant ram horns (i.e. 1 per side) from the top intake plenum down to the cylinders instead of the 8 little ones?

 

That is cool!!

 

How do you find out id the air flow to cyl 1 is the same as cly 8 etc?? How did you decide on the taper of runner and runner length? Are you using an aftermarket ecu? What TB's and MAF did you use...5.0 L mustang? Chevy LS-1?

 

Could he reverse one intake plenum such that one tb is facing forward, with the other tb facing rearward...then connect the two intake plenums (e.g. some sort of cross-over) into 1 large plenum in order to insure that the front and back cylinders get air equally?

 

I have modified many 4 cylinder DOHC engines, as well as v8's and a few 12's. This manifold design is very popular and standard in the industry. The plenum volume keeps the airflow between cylinders balanced. The runner taper/length was determined by flowing the heads and then mocking up a few runner designs to see which runner would give the best power without sacrificing midrange torque. I opted not to port the heads nor change cam profiles this first go-around to see how much power could be extracted without much dollars. Ported heads are $4500 and 4 cam regrinds are $15-1700. So far I have less than $400 in the complete manifold upgrade. I still feel I'll get 425-450 flyheel hp. Remember, these cars are two 1.7 litre 4 cylinder DOHC engines. So, getting 225hp from one is fairly simple. I couln't justify spending an extra $6000 grand to get 50-70 hp more naturally aspirated. Bosch TB's and Bosch MAF's.

 

So you did not do any calculations with helholtz resonance etc and just trial and error flowed it? What ECU are you going to use?

 

Ohhhhhh, yeah! Beautiful work! Looking forward to seeing it completed. You're gonna make some horsepower man. I'm thinkin' the 348 is the most hot-roddable (is that a word?) of all!

 

My new QV intake is looking remarkably similar.......I just made velocity stacks and pressed then oval instead of welding though and I'm flowing in through the sides of the plenum tubes because of the blower. On the flow bench I'm seeing more air flow with the intake than just the bare head with a short stack.

Care to share what you got for flow numbers on the 348 head? I'm wondering how it compares to my ported QV heads, which I think are the same castings. My numbers are all posted on this thread:
http://www.ferrarichat.com/forum/showthread.php?t=129621
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Just wanted to say I have been following all of these threads with tremendous interest, and I really appreciate all the work you guys put into doing AND documenting it for the common good.

One of the primary factors in purchasing a 348 last year was its balance of modern design and limited electronics that let's us tinkerers do our thing. It was one of the few F cars I liked that I felt was easy enough for me to work on, and really seemed like a good value.

I've driven several other Ferraris, and although the 348 is no 430, it certainly is no slouch either. I suspect that the platform fitted with more modern suspension components and a few engine tweaks would have a completely different reputation if it were re-released today-- we are talking about a 17 year old car here.

With so many of us going after intake changes, I assume there is confirmation that this is one of the major performance bottlenecks? Does anyone know what the rationale behind this was during engine design-- detuning, reliability, oversight, etc?

Also, have dyno numbers ever been posted for any cars with the throttle body/intake mods?

 

I like the look of this project! If anyone wants another 348 to work on after this, let me know

 

Hemholtz resonance only comes into play during certain rpm's and are of minimal effect. Though runner length and crossectional progression is of greater concern.