Throttle Bodies - why?

[The Black Flash]

So the current trend seems to be to stick throttle bodies on absolutely everything. But what are the actual benefits of doing this? I understand how roller or slide types will increase airflow at WOT because there's no butterfly spindle in the way; and I guess that the lack of a shared plenum could prevent problems with inlet pulses from other cylinders. But apart from that, it seems to me that unless an engine has a particularly poorly designed inlet setup, the gains aren't going to be that great; and what gains there are will only really be at WOT anyway.

So given the price of a throttle body setup, is it more about looks and fashion than actual performance? Do they provide some other improvement that I'm not aware of? Or are they something which have a large effect on some engines with restrictive inlet tracts, and which people have then just copied, assuming they will give the same improvement everywhere?

[The Black Flash]

Yes, that makes sense.

[The Black Flash]

Snake the Sniper said:

Black Flash, are you also on Locostbuilders? If so , although you'll know me as DIY Si, the other bloke thinking of the Alfa V6. I'm looking at fitting ITBs to the Alfa engine to free up the inlet and allow me to set the engine up properly to allow full power. Mainly because the Alfa inlet isn't really very good, and I think I can do better as I don't care much about induction roar or fuel economy. As said though, ITBs should give better power through out the rev range if sized correctly. This may in turn lead to better MPG and should give better drivability. Also, if set up correctly, they can sound very good too!

Yes, that's me! And on about a million other forums trying to get information about a myriad of things! I mainly post here and on the Dax boards though.

Trying to work out how best to spend my monies on tuning...better cams and inlet work, increase capacity, stick a supercharger on it...? Good to know there's someone else in the same boat.

[The Black Flash]

GreenV8S said:

Marquis_Rex said:

The individual throttles can dampen out part load in cylinder motion (depending on where the throttles are cited) and therefore limit combustion stability at part load- effecting things like lean misfire limit or EGR tolerance (thus limiting fuel economy at some points) and emissions for catalyst warm up

I'm trying to understand this last part.

Me too... by "dampen out part load in cylinder motion" are you referring to the motion of the air as it enters the cylinder? Saying that you get less swirl / turbulence with throttle bodies and hence poorer combustion, at part load ?

[The Black Flash]

trackcar said:

Bums. So it's a simple deflection issue and nothing so grand as I had hoped. I'd got an air de-elasticiser machine all drawn out in my head an' all

Would that not be a supercharger?

So it still seems to me that they're of most benefit on fairly tuned engines using cams with high overlap, and / or which will run at WOT a lot, and / or which have restrictive inlets to start with, and of much less benefit on a mildly tuned road engine ?

[The Black Flash]

900T-R said:

The Black Flash said:

So it still seems to me that they're of most benefit on fairly tuned engines using cams with high overlap, and / or which will run at WOT a lot, and / or which have restrictive inlets to start with, and of much less benefit on a mildly tuned road engine ?

I think that in the latter case, the throttle response advantage still stands.

Oh sure, I guess they'd be of some benefit in most cases. It's just a question of where best to direct limited cash.

Damn that limited cash.