ITBs as an eco mod?

[19bonestock88]

So I was watching YouTube videos about cars (passing time) and I came across a video from Engineering Explained where Jason goes into pros and cons of individual throttle bodies, one of which he said was reduced pumping losses due to not having to pull a vacuum on as large of a “container” with ITBs versus an intake manifold and plenum. Is that to say that properly sized ITBs can increase the efficiency of an engine? Assuming that the rest of the air intake is similar and there’s a plenum above the throttle bodies?

[freebeard]

It's Okay to watch Youtube videos, but no one will go looking without a link.

The most radical setup I've seen had the throttle bodies right down against the intake valves with the injectors above them.

More injectors, more problems?

[19bonestock88]

That’s a solid point, but he does show some compelling science…

https://youtu.be/uS3yHPfT9I8

Makes me think that an ITB setup could be better all around than the manifolds that come on most engines

[aerohead]

Originally Posted by 19bonestock88

So I was watching YouTube videos about cars (passing time) and I came across a video from Engineering Explained where Jason goes into pros and cons of individual throttle bodies, one of which he said was reduced pumping losses due to not having to pull a vacuum on as large of a “container” with ITBs versus an intake manifold and plenum. Is that to say that properly sized ITBs can increase the efficiency of an engine? Assuming that the rest of the air intake is similar and there’s a plenum above the throttle bodies?

There's a context to Jason's comment, and he'd have to get into the specificity of an individual engine to flesh that out.
The very existence of a throttle plate introduces an extremely high-drag excrescence within the flow path, regardless of the interior dimensions.
From engine power curves you'll see that an engine's pumping loss fraction reduces and available brake-horsepower output generally increases with load, however, internal friction is increasing as well as energy lost to exhaust, engine oil, cooling system, etc., so pumping loss 'improvement' needs to be compared to concurrent 'degradation' of other engine parameters to reveal the 'net' overall effect.
Jason is kind of a ' boy racer' and what might impress him might work against those with different objectives.
Smart money is on load reduction. Get rid of all you can which requires horsepower to overcome in the first place.

[Ecky]

Yes. The smaller the volume behind the throttle plate, the smaller the pumping losses (as I understand it). ITBs are an improvement, but you still want some kind of plenum with a single opening, and you'll want to use mass airflow to meter air, because a MAP-based system typically doesn't work well with ITBs.

Even better than ITBs is moving the "throttle" right to the valves. Honda's R series engines (2006+ Civic) vary the intake cam to control valve opening and therefore throttling, under some conditions. It still has a throttle plate, but that gets held wide open when it changes to variable valve timing throttling. Honda claimed a 16% reduction in pumping losses over their standard VTEC system.

[cRiPpLe_rOoStEr]

Originally Posted by Ecky

Even better than ITBs is moving the "throttle" right to the valves. Honda's R series engines (2006+ Civic) vary the intake cam to control valve opening and therefore throttling, under some conditions.

Just think about Fiat's Multiair engines, or that Freevalve system.

It still has a throttle plate, but that gets held wide open when it changes to variable valve timing throttling.

On the newer iterations of the Fiat Multiair engine series, the throttle plate was retained mostly as a quick vacuum source for the brake booster.

[19bonestock88]

All good insights guys! I may tinker with it down the road after the engine is running again

[cRiPpLe_rOoStEr]

I remember seeing something about an air-fuel mixer which didn't feature a throttle plate, meant to be used on Volkswagen-engined ultralight aircraft. It was targetted as a possible replacement for carburettors, due to claims of being less subjected to icing as it didn't have a throttle plate, yet I'm not sure if that could be some source of inspiration if you decide to make individual intake bodies.