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Discussion Starter · #1 ·
How much air do people THINK they need to move to get a larger TB and how many have actually dyno tested outcomes?

I know that on a near stock setup that going oversize can hurt more than help, especially without tuning.

I am about to take my car down for a bit for electrical and transmission work, and am looking at other things that can be done at the same time. I am running about 12:1 compression, along with the Crane 0012 cam. Currently have the Edelbrock performer x manifold and an integra lS throttle body on it.

I never measured the throttle opening size on the manifold, jsut bolted up and drove away. Trying to decide if stepping up to a larger throttle body is worth it now. i know I flow a lot more air than before, but how much velocity is lost going from 60mm to 64mm or 66mm...?
 

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I have seen tests where nothing changed adding those to a stock motor, might have been a later gen civic though. It needs to match the porting on the intake, I would assume you need to match what the intake can move (volume) air efficiently enough to allow for the bigger TB, which in your case you have.

The reason you wouldn't see gains or losses on a stock setup is the port match. If the TB can take in more air but it stops at the intake plenum you get no gain. Like Hyper Threading P4 processors. Sure you have more washers at your laundromat but the same amount of dryers, so no more or less gets done. Consider the washers the TB and the Dryers the Intake Manifold. Again I want to say this was an 8th gen, swapping only TB from 60mm - 64mm.
 

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I dunno if it helps, kinda off topic, but Ive seen a Port Flow Type R TB with a blue TB blade (idk what size it was but not much more than stock) make 235whp NA on a B20V with lowish compression (11) and decent cams crower type r's
 

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Discussion Starter · #4 ·
I recall back in the day having put a 4mm overbore TB on a stock F22a1 engine and it looked cool, i felt cool and it did nothing except have a surge of power on opening throttle always followed by a little stumble before smoothing out.


what do you guys think of swapping the h23 vtec tb from a PDE head? Its a ~65-66mm opening on the big end and tapering to ~62mm at the plate. It looks like most aftermarket throttle bodies are 66mm and larger which seems way too large for what I have. Compression, cam and bolt ons help, but I just cant see needing that much.


funny side note...running some calculators that say a 45mm to 53mm throttle body is as good as i need!
High Performance Math
 

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Discussion Starter · #5 ·
I need to read a lot more about the physics/engineering behind air flow. I have a decent grasp of the basics from fire hydraulics as far as pressure and flow etc, plus a decent math background, but the more I read and look the more i realize how little I really know. I am thinking IF the h23 tb is nearly free AND I port match it may be a decent gain at the top end at least. Though I really need to meausre the manifold opening as well...
 

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Discussion Starter · #6 ·
Just to update...

The Edelbrock Performer X D series manifold has a 62mm throttle opening. I have been using the 60mm integra LS TB. I am likely to go ahead and put the h22 tb on to avoid a step. 2 mm more wont kill me...
 

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No it should work to your advantage up top not having the air stepping up the 2mm all the way around the opening, I would assume.

Although it does kind of compress the air. I wonder if we stepped down to a 10mm TB from a 72mm over some 2mm step downs, if we had high enough compression, we could build an FI intake system......lol. Physics steps in to thwart me again though.....
 

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Discussion Starter · #8 ·
I know steps when designed correctly can enhance flow/velocity...but i am not smart enough to figure that one out on my own lol
 

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I used a 68mm on my B20 build.

But I also port matched it and had 2.75" CAI.


But considering all the other mods like 11.1 compression, cams, head port work, etc etc. Im sure the extra airflow helped my torque curve overall.
 

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Discussion Starter · #10 ·
yeah i bet you are moving a lot more air than me lol.
thats a good amount of compression on a b20, must have been a blast to drive.
 

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A 60mm will make nearly 200whp before becoming a restriction. When I switched my H23A's 62mm for a 60mm (long story) I started seeing a vacuum at WOT after 5000 rpm. If your MAP sensor does not show a vacuum at peak HP, then it's not too small. Larger aftermarket TB's will feel better because of the linear pulley (stock is progressive), meaning it opens faster at low throttle angles for the same pedal movement.

BTW the only people I've seen that have proof that a bigger TB *always* helps are the people who have a vested interest in selling you a larger TB or over-boring your stock TB.
 

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Discussion Starter · #12 ·
Interesting about the vacuum. Out of the blue the other day I found the edelbrock throttle body that was designed for use with the D series perofrmer x manifold....on amazon...for $105 shipped rather than the 449 MSRP. I grabbed it.

Once my car is running again I will have to data log to get a look at an RPM vs map reading graph.
 

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If your MAP sensor does not show a vacuum at peak HP, then it's not too small. Larger aftermarket TB's will feel better because of the linear pulley (stock is progressive), meaning it opens faster at low throttle angles for the same pedal movement.
This right here. If you are not pulling vaccum during WOT, a larger TB wont help you, and switching to a larger throttlebody will lower your throttle preciscion, which will likely make it harder to get good gas mileage.

High Performance Math

These sorts of calculators are always an estimation, so take it with a grain of salt. They claim a 1.8L making peak power at 8500RPMs should have a TB size between 52mm (street use) and 60mm (race use).

I can tell you that my b18c1 with cams, a header, 2.5" open exhaust, intake manifold, and CAI, came with a 70mm throttlebody and switching to a stock 60mm made the car WAY more responsive on the low end, it averaged about 7 more MPG, and it had no noticable less of top end.
 
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Discussion Starter · #14 ·
I really appreciate you guys sharing that info. I am glad I went with nothing more than I have coming (65>62mm) that is matched to the manifold. I am thinking about more aggressive cam in the future as well. The math I have done says I COULD be making 160 crank HP right now, but I do not believe my ignition curve is very well put together...I need Dyno time.
 
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