Dual TB (not ITB) Idea

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Vee Dub Nut
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Dual TB (not ITB) Idea

Post by Vee Dub Nut »

Was sitting around brainstorming about new/different intake ideas for my new engine build, and I thought I'd get some feedback here on one idea that stuck out to me...

Essentially this idea revolves around building a small plenum on top of each IDF intake, and then mounting a single TB to each of the plenums. You'd end up with two throttle bodies, one feeding each bank. Something like this:

Image

I think what I like about the idea is that it would give you more ITB like response, but retain some of the driveability/feel of a single TB. Sort of an average of the two designs.

I like the thought of ITBs for the quicker throttle response they provide, and the isolation of individual barrels in regards to cam/intake dynamics with bigger cams. I'm not real keen on packaging with them though when it comes to turbos. As for single TBs, I like the smooth throttle action and response from a single, but they can be challenging with larger cams, and I haven't just come up with a stellar way to plumb everything in how I want it without having a TON of volume behind the throttle before the intake valves.

Seems like this idea could be made to work pretty well. Linkage for them could be easily enough fabbed, and basic TBs could be had from the picknpull off a multitude of cars. I also think i could package these easier with an IC in the engine bay. On the flip side, I would be concerned that these would have a propensity to idle goofy like single throat dual carbs, but maybe this would be lessened with the longer runner length from the valve all the way into the plenum?

Just thinking out loud, and trying to think of something outside the box to try. Thought I'd see if anyone here had thoughts on this design, or ideas of why it would, or would not work.
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Re: Dual TB (not ITB) Idea

Post by Devastator »

Making sure I understand. You are thinking 2 manifolds like you drew with a TB on each?
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Re: Dual TB (not ITB) Idea

Post by sideshow »

So an electronic version of a single throat dual carb arrangement (solex, kadron, ict, baby dell), but with your spin of a slight plenum and no ½ balance tube?

Beats me if it work better than before, where do you plan on injectors? In the runner in theory should work better than in the plenum.
Yeah some may call it overkill, but you can't have too much overkill.
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Re: Dual TB (not ITB) Idea

Post by Piledriver »

Charge stealing will always be a potential issue on any dual plenum setup with pairs like that, any flat 4 will suffer to soe extent (think Kadron Idle Syndrome).

GM helped the Corvair cylinder to cylinder balance by offsetting the carbs...
That would probably be a good idea, in this case ~same could be achieved by extending the plenum past the second runner to ~match the TB run or more.

Of course firing order would count 21 43 is the pairing/order so at least you can have both TBs on the front or back using that trick, but it might be educational to make a somewhat adjustable length plenum (distance past the far runner) and run it NA and check the AFR on the set, then test each cylinder for balance.

If you are running seuqntial, you can tweak the fuel to balance things out.
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Re: Dual TB (not ITB) Idea

Post by Vee Dub Nut »

Devastator wrote:Making sure I understand. You are thinking 2 manifolds like you drew with a TB on each?
Yea, two manifolds like I drew, one on each bank, each with their own TB
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Re: Dual TB (not ITB) Idea

Post by Vee Dub Nut »

sideshow wrote:So an electronic version of a single throat dual carb arrangement (solex, kadron, ict, baby dell), but with your spin of a slight plenum and no ½ balance tube?

Beats me if it work better than before, where do you plan on injectors? In the runner in theory should work better than in the plenum.
More or less...

Not sure what size (i.e. volume) I would target on the plenum. Been reading on that, but I see advice all over the place on that. I would have the ability to impact runner volume with the uprights that connect to the existing IDF mani to the plenum by changing their length, as well as controlling plenum volume overall.

The manifolds would be CB IDF ones with injector bungs, so they will be mounted down pretty low on the runner. I went with these intakes over the stock encasing style, as these keep the runners isolated from each other longer, where as the end casting style merge quickly past the head.

I could easily run a balance tube between each plenum if necessary.
Last edited by Vee Dub Nut on Sun May 19, 2013 5:58 am, edited 1 time in total.
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Re: Dual TB (not ITB) Idea

Post by Vee Dub Nut »

Piledriver wrote:Charge stealing will always be a potential issue on any dual plenum setup with pairs like that, any flat 4 will suffer to soe extent (think Kadron Idle Syndrome).
Sure.. All of the options except true ITBs would have this problem to some extent (stock end casting style, or plenums on IDF manifolds connected to a single TB etc...). Seems as though the IDF intakes with the longer runners would give some benifit though.
GM helped the Corvair cylinder to cylinder balance by offsetting the carbs...
That would probably be a good idea, in this case ~same could be achieved by extending the plenum past the second runner to ~match the TB run or more.
Do you mean essentially having the same volume on both ends of the plenum past the runner?
Of course firing order would count 21 43 is the pairing/order so at least you can have both TBs on the front or back using that trick, but it might be educational to make a somewhat adjustable length plenum (distance past the far runner) and run it NA and check the AFR on the set, then test each cylinder for balance.
That's an interesting thought. Hrmm...
If you are running seuqntial, you can tweak the fuel to balance things out.
I do plan sequential this time regardless (now on MS3), so I agree that I should be able to tailor injection to smooth out any issues. Just trying not to design something majorly flawed to start with.

Thanks for the input.
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Re: Dual TB (not ITB) Idea

Post by Piledriver »

GM helped the Corvair cylinder to cylinder balance by offsetting the carbs...
That would probably be a good idea, in this case ~same could be achieved by extending the plenum past the second runner to ~match the TB run or more.
Do you mean essentially having the same volume on both ends of the plenum past the runner?
Yes, but not just volume, length to the TB blade or better, bell mouth at transition to pipe.
There might even be a benefit to having the trailing cylinder side be longer-- only testing will say.

I'm slowly working on a dual plenum slot feed idea but it will only work on T3/T4 style pancake cooling, or perhaps under a 911 or raised Corvair setup, basically 2 plenums as large crossover pipes, with long slot feeds in the center.
(180 degree plenum pairs for 1/3 & 2/4)

The idea is to use the slot area/plenum size to set the tuning, ~decoupling the TB area from the equation.

Still haven't decided if it's going to be ITBs near the ports or a pair on either end of the feed tube.
Dev is working on some compact TBs that may allow ~on head mounting on a T4 or perhaps aftermarket spread port head.
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Re: Dual TB (not ITB) Idea

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Re: Dual TB (not ITB) Idea

Post by Vee Dub Nut »

Cool! I hadn't seen that thread recently. That's EXACTLY what I was thinking up more or less.
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Re: Dual TB (not ITB) Idea

Post by TouringBubble »

Someone beat me to it ... lol. I was about to say you'll know how it works soon. I'm trying to finish up the wiring this week/weekend and will try to start her up Sunday or Monday.

I'm running twin plenums and dual TBs just like you are thinking. Steve and I have spoken briefly about it. We have different ideas on the subject, but he actually has data and real world info to back up his arguments ... I've just got theory and limited testing.

I don't have a crossover pipe on my setup, per se. But I do have large vacuum ports on each plenum connected through a common vacuum manifold. This manifold is mainly for a balanced feed for the FPR and Megasquirt MAP reference, but also functions as a low volume cross flow.

My theory is that the minimal crossflow will provide some vacuum balance and feed a little air back and forth to keep the separate banks happy. Also, the plenums have a bit more volume to help fight any charge stealing issues.

I'm not running sequential injection. I'm going to attempt to run batch injection, but I might have to run simultaneous ... we'll see. I've got 560cc injectors that everyone says are super large, but they were fine idling as the stock injectors for the Evo. On E85 the extra fuel needed should open up the option for batch injection ... I prefer it as I feel it lets the fuel charge mix a little better than 3 squirt just sitting on the valve.
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Re: Dual TB (not ITB) Idea

Post by Steve Arndt »

Can't wait to see how it works out for you.
All theory aside, the proof will be in how it actually performs.
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Re: Dual TB (not ITB) Idea

Post by TouringBubble »

I agree. And I hope it works ... I've dumped a bit of cash in to this setup. lol.
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Re: Dual TB (not ITB) Idea

Post by Piledriver »

Evos run sequential, don't they?

Setting up MS2 sequential fuel is pretty easy, and not expensive.
(JBPerf 4 channel board, 5v>1K pullups on the coil drivers and use LS2 or IGN1A coils, or dirive direct w/o the pullups.)
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Re: Dual TB (not ITB) Idea

Post by Vee Dub Nut »

TouringBubble wrote:Someone beat me to it ... lol. I was about to say you'll know how it works soon. I'm trying to finish up the wiring this week/weekend and will try to start her up Sunday or Monday.

I'm running twin plenums and dual TBs just like you are thinking. Steve and I have spoken briefly about it. We have different ideas on the subject, but he actually has data and real world info to back up his arguments ... I've just got theory and limited testing.

I don't have a crossover pipe on my setup, per se. But I do have large vacuum ports on each plenum connected through a common vacuum manifold. This manifold is mainly for a balanced feed for the FPR and Megasquirt MAP reference, but also functions as a low volume cross flow.

My theory is that the minimal crossflow will provide some vacuum balance and feed a little air back and forth to keep the separate banks happy. Also, the plenums have a bit more volume to help fight any charge stealing issues.

I'm not running sequential injection. I'm going to attempt to run batch injection, but I might have to run simultaneous ... we'll see. I've got 560cc injectors that everyone says are super large, but they were fine idling as the stock injectors for the Evo. On E85 the extra fuel needed should open up the option for batch injection ... I prefer it as I feel it lets the fuel charge mix a little better than 3 squirt just sitting on the valve.
Thanks for the added info on Dori... Definitely a cool project.

I was thinking a balance tube would likely be in my design too, primarily like you to provide a common reference for MS, but it would have some low volume balance effect I'm sure.

We'll see... I'm still not 100% on what route I'm going to take with my next motor. I got a lot of the stuff i need to go turbo again, but still have some just run it NA thoughts (hence my Garrett T3/T4 for sale again to see if anyone bites). I like the challenge of the builds and power of the turbo stuff, but seems overkill for how I use the car. That and I'm not getting any richer LOL.
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