adding a second throttle body to the existing setup.

[Davezj]

Hi guys,
I know there has been talk on here a long time ago about increasing the size of the throttle body, but no one seems to have done anything with it.
i think it is due to the hassle of adding the TPS, APS, idle control, traction control, etc to the larger throttle body.
This would be a real pain the butt.

so my question is why can't we add a second dumb throttle body to the plenum to potentially increase air flow into the engine.

when i say dumb throttle body i mean, no sensors, no idle control, just a butterfly flap. the original throttle body would still have all the control on it.


It could be driven by an extension cable or some kind of linkage off the existing throttle body. as long as the air supply comes from the out put of the intercooler somewhere i don't see why it would not work.
the second throttle body would not even have to be the same size as the original it could be smaller to make i easier to fit.

i would have thought it would make life easier if the second throttle body opened at the same linear rate as the original e.g. when the original was 1/4 open the second one would be 1/4 open, original 1/2 open the second one 1/2 open. and so on.
the air going into the engine would still be metered by the MAF correctly.

i dont see many drawbacks, maybe the traction control vacuum actuator? but i don't know if there would be any real benefits either. it would only be beneficial if the existing throttle body was a restriction to the air flow.


Anybody like to comment on this thought.

[c0xxy]

Bit more response, better flow up top. Be surprised if it was beneficial on td03s.
Linkages would have to be rods so no chance of cable stretching n throwing things out.
Would b nice to see 3 or even 6 throttle bodies sat straight on top of the manifold. I bet ITBs on an Na v6 would sound lush

sent from ash

[hbkuk1]

I did this on my FTO twin setup, made no real difference I could notice ran exact same time at santapod and didn't really change the sound at all

[Davezj]

So you dont think it will make any difference effectively having a larger throttle body on turbo car.

i suppose it all depends on weather the throttle body is most restictive part of the air flow system from the turbos to the inlet valves.
the most restictive part of the system is going to be the inlet valves, am i right?

i suppose the question is,
is the throttle body capable of flowing 2.5L of compressed air at 7250rpm
all cylinders fire once every 2 revolutions of the engine sothe consumes 2.5L of air every 2 revolutions ((7250/2)*2.5)= 9062.5L per minute?
If the answer is yes then the trottle body is sized correctly

[foxdie]

Initially this seems like a good idea, but what you're going to do is cause turbulence inside the plenum. If you fire air in from both ends, sure you may achieve higher pressure, but the air will be turbulent and result in minor losses. After all, this is why porting / flowing is a thing

DISCLAIMER: This is for indication only, this could be a very bad idea, I have no experience in modifying intakes, do not attempt this unless you're bat**** insane.

A small amendment to your idea would be to modify a stock plenum that fed the left 3 cylinders from the left and the right 3 from the right side (forgive the crude photoshop)..

dual-intake-plenum-flow.png

The gold band between the red and blue arrows would have to be cut out with an angle grinder and a aluminium / steel cylinder inserted and welded in to stop airflow between each bank of three.

There are a lot more things to consider here too such as cylinder firing order, possibly requiring 1 dual output or 2 single output intercoolers etc...

As for gains, I think the only situation this would really help would be for those going twin aftermarket big turbochargers, the idea does give food for thought though, with this turbos could be located in alternative positions etc..

[swinks]

Dave, not worth a hassle.
In real terms, throttle body from v6 or vr4 fl is big enough. You can try with Boomba Racing or S90 with 75mm. These throttles get factory sensors (tps, iscv).
What you get is sharper response, no power gains. Purpose of fitting is to help with air flow when big turbo fitted ideally with oversized head intake/exhaust valves. This will make big laggy turo spool quicker and prevent premature surge.
In case of td03, no point really for owners of fl vehoicles. Owners of pfl cars may consider v6 or fl throttles to help with spool and response.

[Davezj]

That seems to be the logical answer.

thanks all for spending the time to give you opinion on the subject.

i just wanted to get a sensus of opinion.

[Davezj]

Initially this seems like a good idea, but what you're going to do is cause turbulence inside the plenum. If you fire air in from both ends, sure you may achieve higher pressure, but the air will be turbulent and result in minor losses. After all, this is why porting / flowing is a thing

DISCLAIMER: This is for indication only, this could be a very bad idea, I have no experience in modifying intakes, do not attempt this unless you're bat**** insane.

A small amendment to your idea would be to modify a stock plenum that fed the left 3 cylinders from the left and the right 3 from the right side (forgive the crude photoshop)..

dual-intake-plenum-flow.png

The gold band between the red and blue arrows would have to be cut out with an angle grinder and a aluminium / steel cylinder inserted and welded in to stop airflow between each bank of three.

There are a lot more things to consider here too such as cylinder firing order, possibly requiring 1 dual output or 2 single output intercoolers etc...

As for gains, I think the only situation this would really help would be for those going twin aftermarket big turbochargers, the idea does give food for thought though, with this turbos could be located in alternative positions etc..

i wasn't actually considering splitting the feed at all, i was considering effectively enlarging the existing throttle body by adding a second entry point into the plenum from the same air feed on the same side of the plenum by welding a boss on the plenum and fitting a small throttle body on to that.

what you have suggested would require doubling up of all the sensor related to the trottle body air intake and ecu, which would make it quite complicated. TPS, APS, TCL, idle control valve maybe a MAF trying to balance the banks would be too tricky.
but an interesting conceopt to consider.

[Joe90]

It's been done on other V6s and works well.
Everything can be made to work with enough time and patience.
If you don't know what you're doing, it won't work.

No, it doesn't require doubling of any sensors either.
It makes sense if you've got 2 turbos, 2 intercoolers (prevents surging problems cause by twin turbos), 2 BOVs, it also makes it easier on AFM flow as you can easily add a 50% bypass.


As a mod on it's own, maybe not much use but when it's combined with other compatible mods, it's a winner.

[hbkuk1]

I did this on my FTO it made absolutely no difference at all it's pretty much the same engine without the turbos I can't see it helping the vr4 the turbos are the bottleneck