088: Is Your Throttle Body WAY Too Big? [

[@hpa101]

🔥 Win a T-Shirt or Mug by leaving a written review that can even include a technical question for Andre to answer - hpcdmy.co/reviewpodcast This also really helps us gain more traction for the podcast, ensuring we can keep bringing you more and more episodes with legends like this 😎 - Taz

[@dsmubz]

Andre asks all the right questions, thank you.

[@andrewgould6194]

Andre I love the all of the podcasts.I always learn something you manage to get some of the best people to interview on the podcast.

[@houseofgain]

Great timing, I'm setting up a microtech on a single cylinder 2 stroke for my superkart and I've been trying to decide on single or twin throttle bodies with 4 injectors, 2 of which will be staged and running at the trumpet inlet (external). Wish me luck 😂😂

[@hpa101]

You've got this mate! Going to be a ton of fun when you're out the other side too - Taz.

[@houseofgain]

@@hpa101 that's the plan, it'll either break records or break conrods 😂

[@hpa101]

Let's be honest, there is potential for a combination of both there 😂 - Taz.

[@gordowg1wg145]

Single throttle would be a heck of a lot simpler to get the intake length and tuning right. What engine is it?

[@houseofgain]

@@gordowg1wg145 I thought that too, however I have a set of 4 tb's here from a triumph daytona, they're 38mm, I want to keep the air speed as high as possible, so I was thinking a staged throttle opening. It's a ktm 250sx engine.... basically

[@R.B_B]

Will be great a podcast with Gale Banks about diesel performance and performance in general turbos, supercharged they superteubo projects.

[@GroovesAndLands]

People point out how small my 68mm Bosch DBW throttle is for my 500whp 2JZ... :eyeroll: With good PID settings on a DBW throttle, you can do a pretty darn good job tuning the TPS vs. APS curve to tame a giant throttle.

[@zac2384]

I feel like that's the perfect size. My 83mm Q45 feels no better than my stock GE TB

[@chippyjohn1]

Throttle body sizing is about displacement and rpm, not power. Even 68mm is on the large size, 50mm would be the minimum for a 3 litre at 7000rpm

[@GroovesAndLands]

@@chippyjohn1 No argument here. If people would stop thinking of engine airflow in terms of volume - and instead think of it in terms of density - they'd make much better performance parts decisions. Until then though - bigger is just always better!

[@chippyjohn1]

@@GroovesAndLands It is about volume though, and velocity. A 3 Litre engine at 7000rpm is consuming 175 litres/second. If it is at atmospheric pressure or at boost it doesn't matter. The density of the air will change, but the volume and velocity will not. A larger throttle body is needed if the air has to make tighter turns, if the velocity is too high it may not feed a cylinder as well. Larger throttle body and larger plenum means slower air velocity before the inlet. More important on a six cylinder to have a larger manifold due to cylinder overlap an inconsistent inlet velocity.

[@GroovesAndLands]

​@@chippyjohn1I wrote a different reply, but after re-reading your comment - realized we actually aren't disagreeing about much. I will push back a little regarding your comment about larger TB and plenum helping distribution. I agree it MIGHT help - but the fluid mechanics involved are far too complex to make any generalizations. My intuition suggests a 50mm throttle on a JZ or RB type plenum would create a supersonic jet of airflow entering the plenum - making it difficult for that air to make a tight 90º bend towards the runner inlets. Probably worse for first couple cylinders. But again, there's a lot of dynamics going on here and I'm not willing to go off intuition alone. That said, I don't think anybody would put a 50mm throttle on a turbocharged JZ or RB. I think 65-70mm is totally suitable.

[@KvasoooO]

Hey guys, I am wondering if I missed anything about the friday podcast. Was looking forward to hearing it😊

[@hpa101]

Hey Simon! Andre is taking 3-4 weeks off from the podcasts sorry. We couldn't manage to squeeze in the time it would take to get ahead of things before he left. Andre and more guests will be back though, I promise 😎 - Taz.

[@KvasoooO]

@@hpa101 I would never believe you guys would answer to such a question so quickly. You really are amaizing, keep up the good work and thanks for the answer. Rrgards, Simon