Anyone try twin throttle body?

[opie]

First off a 6 plate TWM is out of the question. I didn't find anything in the archives other than 'maybe' DrewZ had tried a twin TB on an L6.

 

Supposedly, you can get too heavy of a tip-in when you go with the larger TBs of 60mm and up. Would a twin alleviate this problem and still give big flow at WOT, or would it be worse. Originally, I thought of using equal sized plates like the GM F body, but some others mentioned the assymetrical ones (20mm at part throttle then a larger plate deeper into the pedal) They look like the better answer to the tip-in issue and poorer idle of too large a tb. See an example below. pic credit to Jeremy.

[Cody 82 ZXT]

I've thought of that before. With the bigger t-body's it seems like you at WOT all the time. The main proublem that I see in doing this is the fabrication it would take to get this thing to fit our manifolds. Another question is about the total CFM raing of a 60mm and one of these t-body's.

[opie]

I'm not so concerned about the mod to fit it as the function of it. I plan on welding a new flange on my intake for a 65mm anyway. The performance should be better don't ya think?

[Cody 82 ZXT]

I would think that you might pickup some low rpm throttle response but, loose some top end HP. In some of the reading that I've done it seems like when someone is going to make a car have big HP then they swap over to a single large TB. If you could find a big one or have one bored out to have enough CFM capacity then it might be an interesting mod. I guess your goals for the car a be the first thing to think about before you start cutting and moding things like an intake. I have no dought that it can be done and made to look good. If you do decied to do it keep in touch I'd love to see the progress on the item.

[TimZ]

There is no reason that this idea wouldn't work - the staged assymetrical throttles would help give a more manageable tip in response, and if you could get the total cross sectional area to be the same or greater than a single 60mm, there is no reason that it wouldn't flow as much or more.

 

That said, it looks like the throttle body that you pictured has a 20mm and a 40mm throttle, and their cross sectional areas do not add up to be the same as a 60mm. Believe it nor not, this combo only works out to an equivalent ~45mm single throttle.

 

The idea could work, though, if you can find a suitable combo. Assuming, of course that you can fab a suitable mounting flange for it, which would require considerable modifications to be made to the intake.

[z-ya]

Since a 60mm TB will flow enough air for just over 500HP, I would think that time would be better spent improving intake manifold/head/exhaust flow. Unless you are building a 500+HP turbo motor, the 60mm 240SX TB is plenty big enough. If you are building that monstor turbo motor, a Mercedes 65mm TB can be adapted.

 

Pete

[BLKMGK]

Tip-in on a 60mm TB isn't that bad - ask a Mustang owner. Older Mustang 5.0 TBs were like 50 or 55mm but in later years they got bigger I believe. Switching to a 75mm TB made a noticable difference - the throttle felt more hyper - but it was still plenty driveable IMO. Just do a simply 60 or 65mmTB andyou ought to be fine IMO. Accufab makes some awesome Mustang units!

[Guest Anonymous]

It should work ok, the progressive TB I think is a pretty good idea, that looks like a unit off a VW (if not, its just like they use, I think Neuspeed has a bigger version of the same deal thats a bolt on for VW's), I see them on Ebay all the time and wanted to try one on a project at one time. As mention as long as your cross section is bigger than what your using you should see some gain.

 

Regards,

 

Lone

[opie]

It's supposed to be off a 2 liter turbo nissan overseas. I see no reason it wouldn't work great and welding a flange on is pretty easy for a machine shop. I used the 60mm TWM and it was fine for me. It was probably the limit for a T5/3.7 in my taste. I have a 65 MerBenz tb and will weld a flange on the intake if I use it, but may try this since I would want the better manners this would give.

[jeffp]

I have considered this type T/B also. The part does give some advantages for cruise and just off idle response. The thing that made me not want to do it is the fabrication of the inlet coupler. I did not want to spend the time to make something for the part. Making a flange is really simple. I would be willing to bet you would not have to do any welding at all. If you start with a 1" plate, then do the bore for the orignal hole and bolts. Use a phil flat head scerew countersink the plate so the screw is flush with the palte. Then make the plate to match the outer dimentions of the new T/B and blend the scond Hole (the smaller throttle butterfly) into the first hole, similar to the way the T/B hole is shaped then it should work very well.

Rgarding the 60mm T/b flowing enough to get just past 500Hp, well is there anyone out there putting out 500hp for sure by dyno sheets. I can tell you I am, and I am running the 60mm T/B on my car. My problem was not the T/B but the limitations of the turbo. I could push 23-25psi with my turbo, and if you do the calculations you will find I just ran out of air for the engine to make anymore power. There is a give and taks situation here, you can push a part like a T/B further then most think, but what you start giving up is the efficiency of the system. The overall perssure drop across the system begins to increase with the increase of air flow, but if you have a power source that can overcome the pressure drop and still provide the engine to make your numbers, then what is wrong with that? The thing I have noticed, is that when you graduate from one application that makes X amount of power, the next graduation is costly, especially when it comes to changing out turbos and intercoolers, waste gates and all that neat stuff. So I say if it takes a little more kick to get what you want and you can do it, then do it that way, it is surely cheaper in the long run for you.

[Guest Drewz]

Not me!! I am running dual TB's on a 350chev......a little diff than what your thinkin. LOL!! Different is better!!!!!!

[opie]

Gotcha. Jeff, how come you don't have a signiture with your website address in it so "I" don't have to go looking for it. It's a lot of trouble, all that rolling of the mouse and clicking stuff. .

 

Well Drewz, you are using the first tb I initially thought of using. I pictured the F-body unit. You aren't using it on the pictured engine though .

[jp 280]

hey guys

ive been reading these forums for a while now

but thought i would comment on this as i own the throttle body, i dug it out of the box today the top butterfly measures 50mm the bottom one mesuring 30mm.

now as im in newzealand i never realised that the manifolds over there were different, this throttle body has the same bolt pattern as the other manifold i have altough the throttle body to match that manifold has two 40mm butterflys

now if i get this right there should be a picture of my manifold

this is the standard manifold here

[Kevin Shasteen]

Originally posted by Cody 82 ZXT:

.., I guess your goals for the car are the first thing to think about..,

I would agree here about Cody's statement and others. While the 4bl TB would be "cool" my question I'ld ask is what are your objectives relative to the intent of the car/engine? Are you turbocharging this or will it be a normally aspirated engine? I also think that a 4bl EFI engine would be cool-it would/should give that feeling of the 4bl's opening on a carb'd engine under WOT. Bascially all you are talking about is the manner in which the airflow velocity is throttled...yes/no?

 

These are my thoughts-if you are not turb/supercharging your engine (assuming L6 here) you must keep in mind that your engine is not the typical American V6/V8 configuration where you simply slap in a larger cam/Intake/Carb: yes we are still dealing w/airflow velocity but the approach is different.

 

Specifically, referring to the intake system where a carb or TB feeds the Intake's Individual Runners. Instead, on the L6-the TB feeds a Balance Tube...this Balance Tube then feeds the Individual Runners. Prior to the airflowing into the Balance Tube it must journey thru the Balance Tube Inlet. All three of these passages are calculated to match each other; as the principle involved uses pressure waves to tune the intake.

 

The L6 intake works off the Helmholtz Resonator Theory which deals w/tuning the intake by way of pressure waves. However, because the L6 Individual Runners are relatively short it is not a Truely Tuned Intake, none-the-less, it works off the same principles. This Resonator's purpose, seen in the picture on the previous post, allows the incoming air to slow down & gain density which creates a positive pressure that feeds the individual runners when their Intake Valves open.

 

The math for calculating the Inlet is easy, the balance tube not as simple & the IR's are easy; however-most IR's are not properly tuned due to under hood limited space restrictions; yet the principle still remains.

 

For a Normally Aspirated 6cyl Engine utilizing a balance tube-that 6cyl's individual runners will require 65-80% Vol. of the Balance Tube. Where a boost in the 3500rpm range is desired on a Turbocharged 6cyl it will require the Individual Runners being 30% larger than a NA engine.

 

The point I'm building up to is this: the velocity of the incoming air for an engine utilizing this configuration is matched to the peak rpm/displacement which is for a narrow rpm range. For it is the:

 

1) Displacement

2) VE%

3) RPM

4) Peak Power Requirements

 

that determines the size of the Balance Tube, size of the Inlet to the Balance Tube as well as the Length of the Individual Runners if you were going to Tune the IR's to the camshaft.

 

When working the math for the size of the Balance Tube, Inlet Cross-sectional Area, and Length of the Individual Runners you must keep in mind that the incoming air at the Inlet must maintaine @ 180 ft/sec at max.rpm. As you said earlier-to small of an opening and High Rpm is hurt while too large of an opening & low rpm is compromised.

 

So, I would again go back to the question of intent. As a previous poster mentioned about improving power "X Power" of one engine configuration to another requires considerable changes to all components involved.

 

I dont have any real hands on experience in upgrading L6's; but when it comes to L6 performance I have the understanding that the limitation to real power gains is found in the Cyl.Head.

 

In general, from what I have read the Intake Port Throat just prior to the Intake Valve requires the Port Cross Sectional Area to be 80% of the area of the Intake Valve for proper flow velocity thru the Port & thru the Intake Valve's Curtain area.

 

I dont know what the L6's Intake Valve Diam. is so I dont know what it's area (sq.inch's) would be either; but take a SBC 2.02 diam valve. This has a 2.02inch valve yeilding a 3.2sq.in. area requiring the intake ports cross sectional area to be 80%...which yeields a 2.56sq.in area at the port throat just prior to the intake valve.

 

Did any of this make since as this was just off the top of my head...maybe too scrabled?

 

To make a long story longer-let me try and put it all together here.

 

1) Normally Aspirated or Turbocharged

2) The TB isn't feeding IR's, it is feeding a Balance Tube

3) The Balance Tube feeds the IR's

4) Have you considered Banance Tube Inlet size relative to your camshaft spec's

5) What RPM are you wanting your Peak Power to surface? Are we wanting max rpm power or to simply add a little punch to a pre-existing system?

6) Have we even addressed the Cyl.Head Limitations

 

Questions/Smetions-cant we just have fun w/o all the specifics!

 

Here's the math I have come across; keep in mind this math is relative to a truly Tuned engine that utilizes the Helmholts Resonator which works on pressure wave dynamics: the second set of waves to be specific...no I dont fully understand the dynamics but I do understand the math formulas offered; here they are.

 

I) Determining Effective Cam Duration (ECD)

 

ECD = 720-(Adv.Duration - 30)

 

II) Optimum Intake Runner Length (L)

 

L = ((ECD x .25 x VE x 2)/(RPM x RV)) - .5 x D

 

ECD = Effective Cam Duration

VE = Volumetric Efficiency

RPM = Revoltions Per Minute

RV = Reflective Value (using 2nd set of Pr.Waves)

D = Individual Runner Diameter

 

III) Balance Tube Inlet Diameter (D)

 

D = SQRT(CID x VE x RPM)/(V x 1300)

 

SQRT = Square Root

CID = Cubic Inch Displacement

VE = Volumetric Efficiency

V = Velocity in ft/sec...needs to be 180 for max.rpm

1300 = Approx. ft/sec of Air Velocity w/Therm.Dyn at max.rpm

 

Hope this made some kind of sence-no hands on; I just read a lot...that is all a poor boy can do sometimes!

 

Forgetting all the above; if you were able to pull this off I would think your resulting effect w/two smaller butterflies & two larger butterflies at WOT; I would think you would gain power at both ends. Much similar to the difference between a Wedge Cyl.Head (2valves) -vs- a DOHC Head (4valves) ability to breathe.

 

Hope you figure it out-sounds like a lot of R&D is directly a head of you. Good luck.

 

Kevin,

(Yea,Still an Inliner)

[opie]

Welcome JP 280. Thanks for posting the pic of the intakes you guys got. That's the 2 liter turbo intake right? Do you know what year it's off? That's a clean and good looking piece.

 

Kevin, I must have missed the 4bbl intake post. I'm thinking about the use of duals, but not quad. I am talking about a turbo'd application for my L6 and wonder how that's gonna affect the resonance theorum you posted. My SWAG is that since it's forced induction app, that eliminates the need to utilize it? (I may be totally wrong). That's a lot of info to digest at once though. I'll have to visit it a couple of times. Thanks, Doug.

[jp 280]

no probs man

not sure what the manifold was originally off but i got it on a L28 which had a L20 t3 turbo bolted to it so it could of been swaped

the number on the manifold is P75

 

the manifold on the other L28 i have is similar except it has NAPS computer systems moulded in the top of it, like the nissan on the valve cover

and that uses the throttle body with the two 40mm butterflys.

 

later man

[Kevin Shasteen]

Originally posted by 1stGenZ:

.., Kevin, I must have missed the 4bbl intake post. I'm thinking about the use of duals, but not quad..,

My mistake I somehow correlated the title of the post w/the picture of one throttle body that had two throttle plates and came up w/dual throttle bodies (DOH!) both bodies w/two plates.

 

As the great philospher Roseann Rosanna Danna (from Staturday Night Live years ago) always said...."Oh-well NEVER MIND!" Accept for the math-the math is good stuff-so read it till you understand it. At least I found it most interesting. Try a search for pressure wave dynamics on the net-it should yield some interesting reading.

 

What you may or may not have considered is that the airflow velocity doesnt care if it is normally aspirated, turbo'd, or supercharged. All the airflow cares about is if, at WOT, has it reached supersonic speed or not. For once the airflow velocity goes supersonic-your power output will begin decreasing as if it fell off a cliff.

 

For addt'l info you may want to look at David Vizard's book on "Modifying SBC Cyl.Heads" where he touches on this subject. The only difference is in his approach. He doesnt look at the Throat Port of the Cyl.Head at the Valve, rather he takes the Cross Sectional Area of the Intake Port Inlet adjacent to the point where the push rods pass thru the heads; he's still dealing w/airflow velocity just approaching it at a different angle. Vizard also gives some good formulas, you can find them on a sidebar on page 75. Vizard refers to it as the "LPV" (Limited Port Volume).

 

Understanding what the airflow velocity is doing at any one point in the engine allows the builder to make the needed adjustments when modifying the engine; check the math out-it may hurt the brain to begin with but once you get it...you got it: and things are no longer as confusing as they once were.

 

Kevin,

(Yea,Still an Inliner)