Double Throttle Bodies

[ToranaJudd]

Came accross this Pic, How is this done and it it practicle for Twin Turbo?



Cheers Judd

[ed_ma61]

pm Peewee...

[Peewee]

Yes, thats mine

A better/closer pic for you


Basically I bought a second manifold, and had my machinist make what you see.

The thing is that the 2nd TB is actually upsidedown, in order to put the linkage on the same side, and simplify the setup.
The 'snout' was welded up upright, but the flange was cut off, and welded on upsidedown, in order to do what I asked.

As for FI, I don't know, as I didn't have it made for FI.
But I've been told that for FI you should put some sort of barrier down the middle.

[Cobra]

This is a twin Turbo/Twin t/b setup in a Cobra
http://www.planetsoarer.com/twinturbo/twinturbo.html

[Zuffen]

Edz has a similar plenum for his EH Holden build up.

[WDoherty]

if you are going n/a i can't imagine why you would need another throttle body. Ours is pretty large i think 70mm and ls1's make over 400rwhp on an original throttle body (which can't be that much bigger b/c i know it was a big deal that the ls2 went to a hugh 90mm) so for the n/a flow capacity of this engine, i can't see any benefit.

[Peewee]

Go drive a car with twin TB's and you quickly realise why people want them.
Sure, on stock cams they won't produce any more power, but the midrange response compared to stock is awesome.

[Glen75]

Originally Posted by Peewee

Go drive a car with twin TB's and you quickly realise why people want them.
Sure, on stock cams they won't produce any more power, but the midrange response compared to stock is awesome.

Do you think that is due to gain volumetic effiecency or just due to have more cross section of butterfly open at half throttle? If the latter, couldn;t the same be acheived by having a diffent shaped "cam" of the throttle cable linkage?

[rivmasta]

Originally Posted by Glen75

Do you think that is due to gain volumetic effiecency or just due to have more cross section of butterfly open at half throttle? If the latter, couldn;t the same be acheived by having a diffent shaped "cam" of the throttle cable linkage?

I ran the numbers through EAP on a stock engine

with 1 TB @ 88mm Vol Eff maxed at 80.6% @ 4500 rpm
with 1 TB @ 100mm Vol Eff maxed at 81.0% @ 4500 rpm
with 2 TB @ 88mm Vol Eff maxed at 81.8 @ 4500 rpm

With cfm's of 969, 1247 and 1939cfm respectively I would have expected a larger pickup than this... stock cams though... yawn...

however ran it on a modified engine (rally hi torque) and the vol eff changes from 96.7% at 6000 to 98.9%. It also picked up 4pd torque at 4500rpm and 12hp at 7000. this was a single 100mm compared to twin 88mm. This high in the scale a change of 2.2% in vol eff must be a fair bit more mixture in the chamber!

At the end of the day though, this is a simiulation only - what it doesnt take into account is airflow disturbance inside the plenum from 2 opposing columns of air coming in increasing or decreasing intake runner velocity. You'd have to flow bench for accurate numbers, but it seems very plausible to me that vol eff would pick up by a substantial amount in line with a substantial more amount of cfm.

[Lambo]

Hi Guys, Maybe you can answer this one for me, i am toying with doing the twin throttles bodies for twin turbos, i was hoping to use the stock computer with an injector upgrade with maybe a piggyback of some kind, i only want to run 7-8lb boost ,but i figure the flow from 2 turbos would overload the original AFM, i assume the above 2 intakes can't be done with a stock computer because only one side will have an afm, so how does the computer know about the extra air from the otherside, or do i have to do away with the afm altogether and run aftermarket, maybe there is a clever way of running 2 afms , divide the intake pelum and then each afm only sees 1/2 the air flow,and run 2 stock computers, each one running a bank of 4 cylinders, provided the crank trigger and camshaft triggers could go to both computers, i believe thats what BMW did for the early v12 it had 2 separate computers one for each bank. Another idea would be to have a circuit that takes the voltage and frequency from the AFM and effectivly 1/2 s it, or somehow combines the 2 outputs that are feed to the ECU so you could then run 2 afm,s Any thoughts.

Regards
Lambo