308 V12 conversion begins

The TB flow came around pretty quickly. It started out down about 3cfm at .450 lift. I milled the shaft and a very light blend where it met the manifold and it was right back up to as good or better than without the TB....it looks like I own the TBs now
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I'm now the pround owner of 6 ducati TBs....if anyone knows of a deal on more please let me know.

 

F-chat connection came through again. It looks like I found 6 more TBs....but I'm still missing 4 stacks/injectors so if anyone has a line on those let me know. I would also still buy TBs sets that came complete and resell any left over stuff. I'm not sure I will use the Ducati stacks, I might build an air box with the stacks formed into the bottom of it, but it alway good to have options.


Now that I have (of will have soon) all 12 TBs I can figure out how to make them work on the V12 and then see what damage I'll need to do to the hood....I might need to pull Wil in on the hood issue.

 

Thanks Ernie, I missed that!

601 with the tiny 42mm TBs......I can't wait to see what the 54mm TBs do

 

I know, I know. We had colds all around last week, I started a new job this week (still sick) that's an extra 45 minutes each way, it's yard work time, tax time, and i still haven't finished the efi conversion side job..........soon.


I've got 6 TBs here now. 6 more TBs (but only 2 stacks/injectors) are on their way from England.....I think I cornered the world market on ducati 749/999 TBs. I've got the tubing to make the new intake manifold, but I might need to order more flat stock. Hopefully next weekend I can start working on the rest of the intake ports, it's going to take some time.....maybe I'll do the manifold first so I can see how everything is going to look.

 

Nothing really cool to add but I bought 2 more sets of TBs today that have the injectors and stacks so I've got 12 of everything and 16 TBs at this point.....1/2 way to a set-up for a stinkin hot 308/328 and it just so happens I also have a set of heads to match them to so if anybody is wanting to build a 350-400hp naturally aspirated QV/328 let me know and we'll add your money to the V12 fund

Tonight's mostly unrelated project after little one goes to bed is to flow a 360 head for a buddy and see what size TB it likes and see if any of the extra TBs I have belong on that engine. The flow numbers will be interesting for comparison if nothing else. Always so much to do and so little time these days....just 3 more years until Victor starts school and momma and poppa get a bit of a break.

 

360 heads work pretty well.....not quite as well as my TR heads of course, but pretty well. The 360 port is almost exactly the same effective diameter as the ports I put in the TR head for what it's worth.

140 - head with stack
131 - head with suzuki TBs
137- head with Ducati TBs
139 - head with my worked Ducati TB

All the TB setups would probably work a bit better with a real intake instaed on my quick clay intake, but the number will be close.

 

Maybe next year....at just under 2 years he's more dangerous to himself than anything else.

 

There's a lot to it and it's a diminishing return game besides. General type charts are based on who knows what really. What I look for is a TB that does not affect the head flow I worked so hard to achieve and the flow bench says I need the 54mm TB and I need to modify them to get a little more flow through them. I posted all the numbers, smaller TBs were looking to cost me about 6-8 cfm which amounts to about 3hp/cyl or 36hp or 4.5%. So while you could make say 1200hp from 12 54mm, you would make a lot more hp on that engine with bigger TBs. Ducatic uses these 54mm TBs on an engine that makes 116hp or 58/cyl and on another engine that makes 150hp or 75hp/cyl. I'm looking for 67, so right in the middle so you'd think they'd be fine.....but I found the TBs need some rework to be capable of the 67hp worth of air on my head making me think they are sized for the 116hp 750 and the 150hp 999 would do better with a bigger TB, maybe 58mm or so. Unlike cabs, with TBs the rule is "when in doubt go bigger" as there is very little down side to being too big but hp is lost evey time when you're too small.

It's hard to know what the right answer will be until you either put it on a dyno or a flow bench....all you can do is look at what other people are doing and then run the test. In my case the flow bench says I don't want anything any smaller than these 54mm TBs. Another think to point out is the throttle plate itself is where the restriction tends to be so it's getting pretty common for the plate to be much larger than the TB exit bore. The 54mm Ducati TBs drop from 54mm at the plate to an effective exit bore of 48mm (it's oblong but the area is the same as a 48mm diameter). It ususally works out that the throttle plate wants to be 4-8mm lager thanthe port it's feeding to not be a flow restriction of any kind.

I think a lot of the TB sizing stuff that's out there is really based on carb sizing stuff. It's taken as fact in many circles that EFI doesn't make any more hp than carbs.....but when you drill into it a bit you find a 40mm carb was replaced with a 40mm TB for the test when I might have picked a 46mm TB based on the flow. A carb needs to be small enough to carburette but a TB simply needs to be large enough not to hurt flow so the TB also ends up qite a bit bigger than the carb size would have been....and it make more hp every time.

 

Me too. I'm engineer so I alway trust the numbers during the design......and then hope reality agrees

 

A big TB relates to drivability mostly in the way the air flow changes as the gas pedal is pressed. A big throttle plate lets in LOTS of air at pretty small throttle opening so it can get pretty hard to control the engine just off idle. The solution is a very non-linear throttle linkage so the throttle plate doesn't move very much when you first start to press the gass pedal then move progressively faster as you go to full throttle.

As for the loss of velocity, it turns out the velocity at the throttle plate means very little, it does affect the overall intake track length a little but that gets sorted out when picking the velocity stack lengths on the dyno (or in the tuning software). The velociy that matters is at the valve seats and goes up with the larger TB because the flow goes up and the seat ID is fixed. With a carb what your saying is basically true becasue the velocity at the venturi in the carb is critical to allowing the carb to actually carburette, but with EFI those kinds of issues go away. EFI has other different issues but TB size really doesn't come into any of them, it's more about injector size, placement and control.

 

That must be the one that was on ebay about 6 months ago.....blue with a 400i engine. What are the odds of 2 blue 308s getting 400i engines I wonder?

 

You racers.....

Milling the shafts flat did help quite a bit. I don't think there is anyhting left to get on my set-up though since the head with the TBs is flowing the same as the head with a plain stack.....54mm is a big TB for this size port and engine.

 

I was driving home tonight and just about crashed the car....the cam guy called to say he opened the box I sent and was ready to get rolling.

After talking with him and thinking on the drive home.....I think I'm going to just make new masters for him to the specs Steve shared with me. Steve's grind works great in my engine in the software and great in Nick's engine in the software and on the dyno so I don't see any reason to risk grindingdifferent lobes just because he has the master....I don't need a '60s or '70s lobe design mucking up my engine. He said if I wanted to make my own masters he'd send me blanks so it would go pretty quick.