vac or dinan throttle bodies?

[Obioban]

If there’s a way to do it wrong, VAC will find it.

[Slideways]

P54B32 catalog has different part numbers for the throttle bodies. If the fuel injector bores are the same on both S54 and P54 ITBs even though the fuel injectors are different, then they possibly did do some bored out throttle bodies on the P54. That engine did have very aggressive cam options, so unless you go beyond CSL 268/264 with something like a Schrick 280/272 or 288/280, probably not worth boring out ITBs.

[9kracing]

If there’s a way to do it wrong, VAC will find it.

I literally LOL'd

[digger]

you're in a world of suck if VAC is your only option for parts

i would have a chat to Partee racing see if they do this for their engines they may offer the service

[ZHLPR]

Porting the throttle bodies is a valid way of making more power, regardless of the vehicle. The more air you can get in and out, the more power you'll make. So, in that line of thought, doing the throttle bodies is definitely worth it.

VAC probably can probably port a throttle body fine, but they are known for putting out shoddy quality products, so they aren't highly trusted on this forum.

If the only reason you're considering VAC is price, then you 100% should not be doing an all-motor build. That is not the place to be frugal.

Word, just curious more than anything. How bad throttle bodies can wreck your engine. And how VAC could screw these up.

[Cubieman]

If they came apart you would definitely have some bad engine damage, they would REALLY have to mess things up for that to happen however.

[9kracing]

Message Carbahn

[bigjae46]

If they came apart you would definitely have some bad engine damage, they would REALLY have to mess things up for that to happen however.

VAC would find a way...

[Chrisyphus]

Porting the throttle bodies is a valid way of making more power, regardless of the vehicle. The more air you can get in and out, the more power you'll make. So, in that line of thought, doing the throttle bodies is definitely worth it.

This is not the entire truth. There is FAR MORE that goes into induction tuning for NA than "mo bigga is mo betta" if it were, then we would have 3" primaries on headers. Velocity and inertia, as a result, are CRITICAL to filling and scavenging. In velocity stack design, optimising air velocity plays the most critical role, by a wide margin. There are only gains to be had in porting something if it is creating a meaningful restriction that reduces mass air flow- Someone mentioned above that the Dinan ported TBs gained 6 hp at peak, but lost power on the bottom end. I dont see the chart, so I dont know how accurate that is, but based on all the CFD and flow-bench studies I have done on intake dynamics, that is highly plausible. You should only remove material in ways that optimize flow conditions- just removing material for the sake of making the opening larger is playing darts in the dark. Sure, if we're talking about a Gen 1 350 Chevy, yeah... You probably can't go wrong by hoggin that out. But these are BMW M heads (and intake componentry). They are already highly optimized for the intended use case- going fast and being streetable.

If the only reason you're considering VAC is price, then you 100% should not be doing an all-motor build. That is not the place to be frugal.

This is the entire truth lol. Literally any other way of making power is more cost-effective. Not as satisfying IMO, but far more bang for your buck.

[9kracing]

Right well porting a head, porting throttle bodies.... it's all about improving flow. Which is why they are tested on flow benches.

You are correct, just hoggin out a throttle body will not necessarily increase power, and yes, could in fact loser power.

But, increasing flow is about potential power.

A well ported head or throttle body is capable of more potential power, with the correct supporting modifications.

[digger]

Right well porting a head, porting throttle bodies.... it's all about improving flow. Which is why they are tested on flow benches.
.

As soon as you start chasing flow on a flow bench you will go down the wrong path as making it bigger will flow more. You need to work on the cross sectional area and how much does the engine need/want and the flow bench can never tell you that. The flow bench can help with flow efficiency (though most don’t do this) but never size

[Chrisyphus]

As soon as you start chasing flow on a flow bench you will go down the wrong path as making it bigger will flow more. You need to work on the cross sectional area and how much does the engine need/want and the flow bench can never tell you that. The flow bench can help with flow efficiency (though most don’t do this) but never size

Bingo. I optimized our S65 velocity stacks for our carbon plenum and was able to gain 22 wheel horsepower (on our 424 XLC Chassis Dyno) as a result. The best profile I made and tested on the dyno was far from the highest flowing stack on our flow bench (SF 1020) and was not the largest ID of the ~ 40 profiles I generated. Funnily enough, the profile that gained the most power was the very first profile I designed. I only made and tested all the others because I could not believe that I got the profile so right based purely on the math I used to determine the optimal geometry, and because it looked SO different from what I intuitively thought would perform best.

I heard a quote years ago that has proven true time and time again- " the more confident someone sounds about fluid dynamics without real-world testing on the exact scenario being discussed, the less you should trust their opinion."