Ducati throttle bodies on 2110

[Tobias Bylund]

Hi, been browsing here for a while, never posted before though.

I have been looking for a cheaper way to fuel inject my 2110 than to buy i.e CBs kits, after reading up on STF and the samba and found other who have used motorcycle throttle bodies i scoured Ebay for different configurations that might be easy to convert to a vw engine.

The coolest ones i´ve found are the ducati 749/999 throttle bodies. They have the injectors located above the butterflies, shower style, like F1 engines. They are quite big though, 54mms. Ive would be using two pairs of the these, controlled by a MyECU computer, that ducati riders use for aftermarket tuning. The bodies doesnt have the correct spacing as they are, but that is easily modified, so is the linkage.

My question is this, will 54mm be too large for a 2110 engine with 42x37,5 valves, 11.5 CR, K8 cam? Or is it possible to just step down in injector size to keep them within the desired duty cycle? Or is the air velocity just going to be too low to get proper atomization? Below is a picture of the throttle bodies, kinda cool looking huh? =)

[Rick_Eberle]

The injectors will probably be fine, the problem will be the size of the throttle plates. 54mm is pretty bloody big! It might work for a drag engine turning huge RPM's, where all you want is top-end, but on a street engine forget it. Your throttle will be like an off-on switch.

They are cool, though!

[Tobias Bylund]

Hmm... thats kinda the answer i was afraid i would get, there is a guy here in sweden who is running 51,5 IDAs on a 1915 that he is roadracing, but i know there is a difference between carbs and throttle bodies when it comes to comparing bore size, and theres the venturi in the carb that chokes the bore down a bit.

The older ducati 748 had 50mm throttle plates, that might be better, still pretty big, but they dont have the injectors placed above the butterflies... might not make much of a difference in reality, would have been a cool feature to have though.

I see that you are running gixxer throttle bodies, were they easy to adapt to the type 1 manifolds? What plate size are they?

Thanks!

[raygreenwood]

The "shower" style injector...will be lousey for an automobile....unless you plan on having the TB plate roughly 2" from the valve...or turn extreme rpms all the time. Its a totally different dynamic from motorcycles to cars. Ray

[Rick_Eberle]

I see that you are running gixxer throttle bodies, were they easy to adapt to the type 1 manifolds? What plate size are they?

They are 42mm, which is too big for my 1.7 Type 4... the manifolds had to be cut down and machined, and the tubes moved 10mm closer together. Details here.

There is a BMW bike TB that is 36mm, and the same bore spacing as the Type 4 manifolds. A guy here in Australia has used that set-up, and it seems to work well for him.

[raygreenwood]

So you had to "split" the twin TB and then rejoin the two barrels? Ray

[Rick_Eberle]

No, not the TB's, but the manifolds.

The TB's started out as a four barrel, that is basically two twins bolted together. I had two sets of four barrels, so I split them in half, and used the linkage side of each set. (They were REALLY cheap - both sets for under US$300, with injectors, TPS's MAT sensor, etc).

So, starting with two sets of these:


Split them, and ended up with two of these (I had to make a TPS bracket for one):


The manifolds were EMPI's, cut down from the top to where the ID matched the TB's, and then cut between the ports and rotated around the port opening to give the 80mm spacing:



Then I made some transition rings to join it all together (they are bolted to the manifold - not shown in the photo):





For the linkage, I'm using a crank made from the old air cleaner bracket, that uses the stock 914 throttle cable, and the GSXR cables:



You can see that working in the video.

I know that 42mm TB's are "too big" for a 1.7, but they seem to work quite well. The mid range and part throttle response is great (though I mainly use TPS based Accel Enrichment, not MAP based). At 6k RPM, the MAP falls by two kPa at WOT.

[Piledriver]

Very Nice.
Source for the stacks?

I scored a set of 40mm GSXR TBs (600&750) off an `06, and a set of NIB 42s off a Yamaha 1100 jet ski.

The latter are really neat as they are true ITBs, flange mount, and only ~50mm "long".

I think I have ~$115 total in both sets (Incl shipping), so keep an eye out on EBay.

A 40mm TB flows like 48IDAs with 40mm vents... But with EFI, a little too big isn't going to kill you, the 44ss WOULD probably work fine on the 1700.
(I ran 44IDFs for years, and got >50MPG on the highway)

The 52s.... Maybe not, but I bet they would work fine on a single IDF manifold as long as the injectors were at the ports.

I have an Evil Plan for the intake mainifold... Audi inspired.
Quad TBs and 3 plenums...

[raygreenwood]

Nice work! ...yes....$300 for the whole set up is hard to ignore. Ray

[Rick_Eberle]

Source for the stacks?

They are the stock Suzuki part... they also mount the TB's to the airbox on the bike. I cut the airbox up and mated the peices to my air cleaners.

I have an Evil Plan for the intake mainifold... Audi inspired.
Quad TBs and 3 plenums...

I'd like to see that!

[raygreenwood]

So Piledriver.....would that be ....four individual TB's at head level....with a center plenum and two smaller plenums all upstream of the TB's?

BMW has done some of that also. I think that if properly designed.....it can negate issues of TB sizing quite a bit. It would put more emphasis on proper sizing of the primary and secondary plenums.....but the tunability and smoothness should be superb. It should absorb reversion well. Ray

[Piledriver]

This is hijacking the thread seriously...
Will move to it's own and link here if the thread owner wishes.

What I'm working up is basically 3 large dia short tubes... 1/3 and 2/4 have their own ~1.5L plenums, and the TBs (or just runners) will go into the ends.

(Although I have a theory that TBs near the ports may help mixture quality at low/medium throttle settings due to the extreme turbulence plume)

The whole shebang would easily fit on TOP of an industrial (low profile) T1 shroud, but I' using it it in a 914 on a T4.

The secondary plenums will be tangentially slot fed from the primary plenum (4" tube, length/volume TBD), on top/center.

If you can't visualize, I'll try and do up a sketch or such and post.

Recommendations on volumes appreciated, was going to start with the std calculations, quick back of the envelope calcs show I should be able to get 1st-4th reflections in the usable RPM range of the engine, using the (nominally) 4-2-1 design.

It could work with a single TB just as easily, but I like the concept of having all that air volume (at ~1 bar++) as close to the runners as possible for throttle response, the quad TBs should deliver.

Goal is to build it so I can swap the whole center arrangement out for various setups so I can test easily.
(still want a 4>1 and 4-2-1 collector style tube center to try)

Trying to make it work with shortened/tweaked 2.0 914 runners, 38mm ID IIRC. Those match the ports, and have the perfect entry angle/injector placement/mounts etc.

I'm still at the point of trying to score the 3-4" SS tubing scraps I need, but it's just a matter of time.

If all else fails, it may just end up being fiberglass, messy, but straightforward...

The "low profile" 42s will probably end up on the T3. As they are true ITBs, I can set the spacing (or even mount angles/butterfly axis) anywhere sensible. (T4 intake ports are not straight in, except on the 1.7 heads... They are spread about 15 degrees from vertical front/rear, probably to induce swirl. IDF manifolds don't even try to match the correct entry angle.)

[raygreenwood]

I surmised most of where yoy were going from the three pot configuration. Cool! The straight angle on the 1.7's....I beleive ...was done in the beginning planning to work with the EFI runners better. The 1.7 had the most development time under its belt and FI was well underway in 1966-68 (I have a photocopy of the original blueprint for the ECU wireing end connectors.....it dates to 1966) . I think they thought a lot about the end combo and package while they were getting it off the ground....and little things like the straight shot ports, the quench area to match the dome and the shape of the plenum...were better on teh 1.7 than the later engines. Ray

[Tobias Bylund]

This is hijacking the thread seriously...
Will move to it's own and link here if the thread owner wishes.

No no, thats fine, its an interesting topic, building your own ITB setup from different parts. And it makes it easy for me to find the thread again

Im searching ebay for usable bodies that i can hack up and convert in to something for my engine, the GSXR 42mm sounds like they would definitely work out.

//Tobias

[Steve Arndt]

Check out Subaru TGV tumble generator valves that new turbo Subarus have. We had a 2.5 legacy turbo engine in the shop that I spent a few hours looking at. The four individual throttles are are very close to the heads are closed most of the time. The system is drive by wire. It also has a central plenum and single throttle just like older Subys. The TGVs have a segment where the butterfly is missing. This forces ALL the intake air to take the long, outside wall. The injector is positioned right in the very velocity area. The TGVs only open up when there is enough bulk airspeed to sustain atomization.
http://www.drive.subaru.com/Win03/Win03 ... e_Idle.jpg

http://www.drive.subaru.com/Win03_Manifold.htm