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K20A2 Throttle Body Dyno Test: Stock 62mm vs Blox 72mm:

In the never ending quest for more power, I seemed to notice a trend. It appeared that most people putting together mild K20's were all using some type of aftermarket throttle body between 70mm and 74mm. It just so happened that my throttle body was cracked and we did have a Blox 72mm here at the shop. Seemed like a no brainer to do a little comparison while picking up a few horsepower.

My Setup Consists of:
Stock Internal K20A2
Custom 3'' Intake with BPI Stack an K&N Filter
RBC Intake Manifold
Skunk2 Megapower Header
Hondata K-PRO

Before Pictures:



After Pictures:




The Result:


No real change. Air Fuel Ratio stayed right on par, Played with Timing and Cam Angle but never really picked up anything unfortunately.

These are our results with this particular setup. The intake manifold was port matched to 72mm, And these are both average number's of three before and after pulls. :up:
 

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surprised as i have seen 3-4hp gains on some k20's. thx for doing the comparison, need more ppl like ipg doing these dyno comparisons. dyno stock and blox on same day?
 

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Basically the same. I'd say try 3.5" piping for the intake. When I went from 3" to 3.5" my AFR's went from 11.2-3 to 11.9-12.1. Not sure how much of a difference that is making but keep in mind the IAT sensor isn't hooked up yet inside the intake (I just taped it around a hose) and I haven't re-dynoe'd it yet. Still waiting for the right time to send out the i.m. and t.b. to maxbore.

Would you recommend a straight through 70mm t.b. or a tapered 64-70mm? I'm getting conflicting answers. Some say tapered due to velocity others are saying go with a straight thru so there's no restriction.
 

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These results seem very normal. A stock throttle body is actually good to flow good for a 400hp engine. Unless an engine s is highly modified, or boosted, no real gains with be made on a stock engine with larger TB.

Results were the same when tried on stock d and b series engines years ago too
 

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Without having seen any comparision on a TB Before it seems logical.

I see it as a train of air bubble/volumes, with every 4th volume bubble going into every 4th cylinder.
so the runners square area should be the main limitation.

Ofcourse it seems better to have a bigger TB as you don´t want more limitations.

I still want a bigger TB myself tho.

BR, Per
 

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FWIW, I saw the same thing as Tom on a mild K24 build (06 TSX + 12.5 pistons, Hytech, 3" ex, 3" CAI, RRC). 230-ish hp motor. Compared ITR TB vs 70mm Hybrid. No gains. Manifold throat ported to match for the 70 test.

Also saw very little difference between 3 & 3.5" CAI's on the next build (11.5 & Kelford 179-B...rest the same as above).

I've done a bunch of research on TB's, manifolds, and CAI's. Lots of good stuff out there if you spend some time with teh Google. TB sizing is not just total airflow (though that is a factor). For example, manifolds with larger plenums don't need as large of a TB as those with smaller plenums (there's more air stored in the plenum and less need to refill as quickly)

Here's some links...the first one has more links within, including some David Vizard goodness:

http://www.team-integra.net/forum/blogs/michaeldelaney/130-intake-manifold-tech-runner-size-calculations.html

http://www.rbracing-rsr.com/runnertorquecalc.html

And here's a nice quote:

The best way to find out if your TB is too small for your IM plenum is to determine what the intake manifold absolute pressure (MAP) sensor is reading (in the plenum) when you are at full throttle ( or wide open throttle (WOT) ) while the car is accel using a datalogger. The MAP should be equal to, or close to, atmospheric pressure. If it isn't or there is a MAP drop at WOT, then your TB is still too small.
 

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I'm hoping a few of you will chime in on this. Would these results have changed if bigger injectors were put into the mix? (RDX or maybe bigger?)

I know a bigger TB on a bolt on B-Series is a waste of money. Maybe the same goes to K-Series too?
 

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The best way to find out if your TB is too small for your IM plenum is to determine what the intake manifold absolute pressure (MAP) sensor is reading (in the plenum) when you are at full throttle ( or wide open throttle (WOT) ) while the car is accel using a datalogger. The MAP should be equal to, or close to, atmospheric pressure. If it isn't or there is a MAP drop at WOT, then your TB is still too small.
:new_slayer:
 

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And here's a nice quote:

The best way to find out if your TB is too small for your IM plenum is to determine what the intake manifold absolute pressure (MAP) sensor is reading (in the plenum) when you are at full throttle ( or wide open throttle (WOT) ) while the car is accel using a datalogger. The MAP should be equal to, or close to, atmospheric pressure. If it isn't or there is a MAP drop at WOT, then your TB is still too small.
I partly agree with this...if there is a MAP drop at WOT that simply reveals a restriction to flow somewhere in the intake between the filter (or velocity stack) and plenum. Yes...it could be the throttle body, but the restriction could also be due to the intake tubing.

The MAP is simply measuring the pressure gradient across the entire length of the intake. Pressure (gradient) = flow (air) x resistance (of the intake).

Resistance is influenced by the LENGTH of the intake tubing as well as the cross sectional AREA of the intake tubing and throttle body. So, if there is a drop in MAP at WOT you cannot simply say it's the throttle body without entertaining the possibility that the intake is the actual restriction (unless you also simultaneously know the pressure just proximal to the throttle body).
 

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I partly agree with this...if there is a MAP drop at WOT that simply reveals a restriction to flow somewhere in the intake between the filter (or velocity stack) and plenum. Yes...it could be the throttle body, but the restriction could also be due to the intake tubing.
Absolutely, there is a few things to play with before thinking of changing the tb.
 

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^^^ What would those things be?
 

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FWIW, I saw the same thing as Tom on a mild K24 build (06 TSX + 12.5 pistons, Hytech, 3" ex, 3" CAI, RRC). 230-ish hp motor. Compared ITR TB vs 70mm Hybrid. No gains. Manifold throat ported to match for the 70 test.

Also saw very little difference between 3 & 3.5" CAI's on the next build (11.5 & Kelford 179-B...rest the same as above).

I've done a bunch of research on TB's, manifolds, and CAI's. Lots of good stuff out there if you spend some time with teh Google. TB sizing is not just total airflow (though that is a factor). For example, manifolds with larger plenums don't need as large of a TB as those with smaller plenums (there's more air stored in the plenum and less need to refill as quickly)

Here's some links...the first one has more links within, including some David Vizard goodness:

http://www.team-integra.net/forum/blogs/michaeldelaney/130-intake-manifold-tech-runner-size-calculations.html

http://www.rbracing-rsr.com/runnertorquecalc.html

And here's a nice quote:

The best way to find out if your TB is too small for your IM plenum is to determine what the intake manifold absolute pressure (MAP) sensor is reading (in the plenum) when you are at full throttle ( or wide open throttle (WOT) ) while the car is accel using a datalogger. The MAP should be equal to, or close to, atmospheric pressure. If it isn't or there is a MAP drop at WOT, then your TB is still too small.
I've seen enough gains from 3.5" intakes to know it's not an anomaly, i know that much.

My personal car and my buddy's car both picked up 5-8 whp from 6000 to 7500 rpms with a 3.5" intake over a 3".



that's his dyno.

Thin line = PLM header, Injen CAI, full race 3" exhaust, 65mm throttle body
thick line = PLM header, Hybrid Racing CAI, Full race 3" exhaust and 65mm throttle body
 
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