348 throttle body porting

As Rob'Z and I discussed in this thread http://ferrarichat.com/forum/showthread.php?t=342739 I volunteered to send him my throttle bodies to have them ported. I was supposed to have send them to him last Monday but didn't get them shipped out until today. You know the whole Thanksgiving week thing, sorry about that Rob. Anyway they are on their way now.

Here is the how-to thread I posted in the tech section http://ferrarichat.com/forum/showthread.php?t=346550 on removing the throttle bodies, and the throttle position sensors.

Rob asked me to do some mic-ing before I sent them too him. Both the front and rear openings of the TB came in at roughly 57mm, with the middle mic-ing in at 54mm. The opening starts at 57mm and tappers down to the 54mm, with the throttle plate right smack in the middle of the small part of the TB. Then just after the throttle plate it quickly opens back up to 57mm on the back side. Seems to me they were trying to make the TB have a venturi effect. But all I think it does is act like a daggon restrictor. Especially with the throttle plate sitting smackdab in the middle of the opening screwing up the air flow. Not forgetting to mention reducing the total inner area of the TB. So even though it's 54mm with out the plate, the total area could be acting as small as 50mm with the throttle plate taking up space = T I N Y! The TB's seems to have plenty of meat on the walls as those came in at 4mm thick at the front opening. I also mic'd the opening on the intake plenum, where the back of the TB mates to the plenum top. That came in at 58mm on each side, 1mm larger than the rear opening on the TB.

It's gonna be interesting to see what you can do with the TB's Rob.

Here are some pics of the TB I borrowed from the how-to removal thread.
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

in my previous DIY TB porting work (other brand toys ), one observation, we found that as opposed to boring a max diameter straight through, there was not a noticable power difference, but a noticable driving response, by intentionally having a slight taper/ramp-up before the throttle plate & after....why? it seemed that it encouraged some acceleration of airflow through that point, prevented a slight hesitation/stall sensation experienced with a straight through max bore, most noticable when going from a zero or slight throttle opening...something to consider

fortunately you don't have an AIS plunger/motor to deal with, but as the air bypass ports lead in at 45 degrees (approx) then hopefully taking that much 'meat' out of the bore, doesn't adversly alter the positions relative to the throttle plate (difficult to see in pics)


look forward to seeing the results great stuff!

 

good note garnet !! I have seen the benefits of feathering cross sectional flow areas during flow tests. This reduces turbulence and helps maintain homogenous air density.

 

Been giving it some more thought, and I think I have an idea why they put that venturi in there. My guess is because of the super long path the air has to take just to get to the throttle body.

I just ran out to the garage and shoved a tape measure through the intake opening. From the edge of the opening in the quarter window to exit of the flex tube. Then roughly the turn from the entry of the air box to the exist of the air box. Next from the intake portion of the MAFS to the exit of the tube where it would attach to the TB. Guess what it's length was? Roughly 70", that's just 2" inches short of 6' FEET!!!! It could be a couple of inches shorter or longer, but that is the ball park, and is for sure way over 5' feet long. That is an EXTREAMLY long way for the air to travel before it gets to that tiny 54mm opening in the center of the TB.

So no WONDER they wanted to try and make a venturi in there. Because if you are at a stand still, then mash on the throttle, you aren't gonna get jack squat for air. The engine has got to work hard to get the air moving over that longass distance before it even gets to the throttle plate. Way easy for the air to slow down when it has that long of a distance to travel, especially if you get off the throttle and then back on it.

Damn near SIX 6" feet of intake, then to have to squeeeeeeeze through that coffee straw of a throttle body = not good for power in my opinion.

 

Did another measurement right now. Pulled off one of the MAFS and mic'd the front and back openings. Both inner diameters measured 66mm.

Yeah dude, I am thoroughly convinced the 348 engine is choked off BIG TIME.

It's gonna be interesting to see what the difference is in the flow of the TB's before and after the port job. Hog those bad boys OUT Rob.

 

This sounds very interesting. I will have to keep a close eye on this thread and seer Ernie's results.

--Mike

 

Is it a venturi or bell nozzle? You may want to work that angle as I know that is used in areas where intake restrictors are required (but not a spec shape) to make the orifice seem 'larger'. It works extremely well on racing classes that are limited to a certain cfm carburetor (look up the HO racing 'rocket box' for a practical application). If the TB's are truly a restriction, creating a venturi or bell nozzle will reduce/remove it as the restriction. Maybe Ferrari did that and that's what you're seeing? If so, changing the shape could hurt it. If you eliminate the venturi altogether, you drop efficiency of pressure recovery on the outlet. It becomes an orifice instead of a venturi or nozzle. Fwiw, venturi is around 96% efficient, straight orifice is 68% efficient. So you could potentialy go from a 54mm opening with 96% pressure recovery one side to the other to a 56mm opening with 68% recovery...I know this isn't the case, but you might be able to get better results by increasing the efficiency of the venturi by converting the shape to a bell nozzle rather than hogging it out a couple mm and ruining the shape.

Can't you calculate whether it's a restriction or not based on TB size (treating it as an orifice) and airflow requirements?

 

Well when I looked inside it appeared to be straight, so I'm guessing venturi as I see no curves. My calipers weren't long enough to get inside from the front, and I could just get them on the back edge of it from the rear. But just eyeballing it I could see a definite hard angle where it necked down, with a sharp ridge where the throttle plate would rest at full closure. Both on the inlet and exit side. It's also not even. The tapper appears to be biased to the right side of the throttle body on the entry side, and biased to the left on the exit side. Probably due to how the plate opens, or my bad camera angle?

As for the bell nozzle I found this calculation. But I dunno how Rob would machine that? If it needs to be machined like that at all. He did say he was gonna put a 7º tapper in it.
Image Unavailable, Please Login

 

Open up the throttle plate and stick a straight edge in. It will be pretty obvious if the port is completely straight or not.

 

I would Mitch, but the Fedex man has them. Rob should be getting them tomorrow.

 

i think you will see a change, probably will feel it, from the TBs being significantly bored.....in an early N/A car of mine, the TB went from 50+mm to a 90mm (swapped + modded TB).....just from a straight swap of a larger OEM TB (with venture shaped bore) the car was still quite responsive at tip-in of throttle (in fact more so).....it was when bored out that same TB straight through (only a couple mm taken out + new plate installed) that throttle respose went flat a bit

IMO even going to as large a ported TB you can with that OEM piece, you're not going to be overly huge I.D. still, and would be surprised if it had to much negative effect.....after all, you are not likely to get the TB I.D. to the 66mm of the MAFs

it would be interesting to use the TPS sensor bosch part# to cross reference what other cars/engines used it, and if amoung them is a potentially larger TB available for potential swap in??

next restriction looks like the 2-1-2 airbox of that intake system IMO

 

Not even close to 66mm. Biggest I think it can go would be 59-60mm. We'll find out soon enough.

For sure.

 

Ernie, what is the part # of the TPS? i'm curious to check on if any potential larger TB swap candidates

 

0 280 122 044

 

That would be tough to build/machine for sure. You'd have to start the bell right at the throttle plate and it would rapidly get bigger than the intake inlet on the plenum so you'd have no way to mate it up unless you also redesigned the plenum.

After further contemplation, I think you'll be fine if you can do it straight through at 57mmm as that appears to be what the size of the plenum inlet is. If you go larger, you will just have to taper back down to whatever the inlet size on the plenum is. Did you measure the opening on the plenum? If they did a straight taper down, taper up it's to create a venturi so that the transition to the minimum CSA is efficient. So, if you open up the minimum CSA (and it's the limitation), you should get improvement. I guess I didn't fully think it through before. If you needed more air using the same TB, you could make a new plenum inlet that allowed a bell nozzle coming off the TB...What strikes me as interesting is that they did the taper at all. It makes me think that they made the rest of the intake tract a little bit larger than needed and sized the TB to get velocity right. Meaning, something else is the limitation and the TB is sized to match it. Otherwise, why not just put a 57mm TB on it from the get go?

 

Yup.

Both came in at a bit over 58mm

Well one thing for sure is looooooong intake track cannot be good for flow. Especially how they have it routed.

The other thing is the way the plenum is configured, with the tb inlets on the sides. What's the point of having a high velocity charge if it's just gonna smack into the back side of the plenum top. Plus the top sits so low that the top of the runner stacks are sitting right in the path of the incoming air.
Image Unavailable, Please Login

 

lots of meat there to open it up if you so chose

true, but compare the size/volume of the plenum to say an enzo plenum, and it doesn't seem that much better.....but definitely could be improved as you say

in my reading, found FBB refer to Gothspeed as maybe having made? plenum spacers, to this end?? ....but your already well versed with all this and the H manifold
http://ferrarichat.com/forum/showpost.php?p=137255487&postcount=33

some interesting feedback from daniels build, about the stock TBs
http://ferrarichat.com/forum/showpost.php?p=140259344&postcount=54

found this post, refers to "group77racing" having already found/used alternate TBs (and MAFs) of larger I.D. (from volvo?)
http://ferrarichat.com/forum/showpost.php?p=137257053&postcount=39


IMO i don't know that the overall intake track length would make as big a difference, provided all the mods made are aimed toward minimizing resistance for engine to draw air from


dug up this thread, UCH explores a shorter intake track length

http://ferrarichat.com/forum/showthread.php?t=240272&highlight=355+ram+air



IMHO a minimal $ effort results orientated approach would include: find TBs up to 65-66mm and plenum ported to match........port/polish work (like daniels) of the plenum lid and runners........draw intake air from both side grates and also 3/4 windows to a pair of much larger volume air boxes (composite and insulated), and eliminate the oem center 2-1-2 airbox....use smooth inner-bore silicon piping (look at marine silicon hose, can be bought in large bore and long lengths)


Image Unavailable, Please Login

 

I will taper the TBs from entry to throttle plate. They will have a nice long radius, this was a big improvement on the 300ZX TBs I've done. They had an abrupt change in angle from the TB entry to the throttle plate bore, smoothing out that transition is key.

I was out sick today so hopefully I will get a chance to take a look at the 348 TBs tomorrow.

Stay tuned.


Rob

 

A HA!

No wonder you haven't been one here. Well get better Rob.

 

What do ya think?


Rob
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

looks good Rob

what did the T-plate diameter end up being?

 

57mm, it was the max I could go without compromising the wall of the bearing seat. I removed a lot of material at the leading edge and formed a nice taper down to 57mm to maintain velocity. The flow should greatly improve, I hope to get them to the flowbench tomorrow.


Rob

 

I LOVE IT!!!!!! Beautiful work Rob!!!!!

Can hardly wait to see the flow numbers.

 

Interesting thread chaps.

 

so TPS is actually bosch # 0 280 122 004 ....no wonder i couldn't fine anything

http://ferrarichat.com/forum/showpost.php?p=141016878&postcount=28



other then in list (above link) there appears to be a couple of inexpensive alternate TB swaps, one is a volvo 65mm (shown in pic) and possibly a 75mm, both fit the proper bosch TPS...they are physically same/similar to OEM 348 TB, and use the same linkage (ball) connection

the OEM 348 TBS are mirror image of one another, but a swapped 2nd TB can be tasked easily enough

a pair of 65mm ported out to 67mm, would match the OEM 348 MAFs, making a nice match IMO

turned out great Rob

what is the dimensions of the mounting studs (4)?? i can check on that also, thx ....i believe they are same 10mm bolts

.
Image Unavailable, Please Login