Honda / Acura K20a K24a Engine Forum banner

21 - 40 of 61 Posts

·
USDM > *
Joined
·
4,858 Posts
Again, circumference (aka cross sectional area) is only one piece of the puzzle. Length of the intake is also important and likely explains why some people get conflicting results with 3" and 3.5" intakes. The math shows that it is possible to have a short 3" pipe that creates less resistance than a long 3.5" intake.




Delta P = pressure gradient
L = length
D = diameter
Q = flow


As Bernardi (aka AWH) correctly stated above, at some point the intake (tb and intake tube) is no longer a restriction and increasing the diameter of the intake tube and tb is pointless.

People try to simplify this to a one size (aka 3.5" intake) fits all scenario and then wind up confused why they didn't see the expected gains.
 

·
Registered
Joined
·
1,080 Posts
Again, circumference (aka cross sectional area) is only one piece of the puzzle. Length of the intake is also important and likely explains why some people get conflicting results with 3" and 3.5" intakes. The math shows that it is possible to have a short 3" pipe that creates less resistance than a long 3.5" intake.




Delta P = pressure gradient
L = length
D = diameter
Q = flow


As Bernardi (aka AWH) correctly stated above, at some point the intake (tb and intake tube) is no longer a restriction and increasing the diameter of the intake tube and tb is pointless.

People try to simplify this to a one size (aka 3.5" intake) fits all scenario and then wind up confused why they didn't see the expected gains.
Ah but herein lies a problem and a solution.

Problem: what is the proper intake length.
solution: test that shit

See, when hybrid racing was making that intake, they tested different lengths different sizes and different transitions from 3.5 to 3"

What you see is the best result of that testing. It was tested on bolt-on and bolt-on + camshaft cars.

Not all cars are the same, but in this scenario, it's obviously close enough.
 

·
USDM > *
Joined
·
4,858 Posts
Ah but herein lies a problem and a solution.

Problem: what is the proper intake length.
solution: test that shit

See, when hybrid racing was making that intake, they tested different lengths different sizes and different transitions from 3.5 to 3"

What you see is the best result of that testing. It was tested on bolt-on and bolt-on + camshaft cars.

Not all cars are the same, but in this scenario, it's obviously close enough.
I agree 100%....math will get you close, but testing is required for confirmation.

Regardless, my point (and Bernardi's) is valid that for some people, there will be no benefit from increasing the tb and/or intake diameter. I'm just trying to temper the "3.5" > *" enthusiasm.
 

·
The Professional
Joined
·
1,873 Posts
Hm. Wondering how much more you would've picked up with a tapered bored t.b. to help create more velocity for that 3.5" intake. I'm pretty convinced now that a straight thru 70mm t.b. isn't going to give a relatively stock motor any gains. Or very little. Either way i'll be sending out my i.m. and t.b. to maxbore when i can find the right time. I won't be able to do a back-to-back dyno but i'll be able to tell whether i gained or not.
 

·
Registered
Joined
·
37 Posts
Had a K24a2 in my Si and when we tested throttles, a ZDX 78mm tapering to 70mm would yield more gain than a straght skunk2 74mm. It was a 2007 TSX engine, Brian crower Stg2 cams and valvetrain.
 

·
The Professional
Joined
·
1,873 Posts
Had a K24a2 in my Si and when we tested throttles, a ZDX 78mm tapering to 70mm would yield more gain than a straght skunk2 74mm. It was a 2007 TSX engine, Brian crower Stg2 cams and valvetrain.
Interesting. So you tested both the zdx tapered throttle body and the straight thru skunk2 74mm throttle body and the zdx gained more? Would it be possible for you to post up the graphs? I'd like to see how much you gained and where in the rpm range.
 

·
Registered
Joined
·
37 Posts
Interesting. So you tested both the zdx tapered throttle body and the straight thru skunk2 74mm throttle body and the zdx gained more? Would it be possible for you to post up the graphs? I'd like to see how much you gained and where in the rpm range.
Could try to find it. Lost tons of stuff moving home. Should be in a box with all my drag slips lol. But yes it yielded a little more, not a lot but still.
 

·
Registered
Joined
·
5 Posts
Greetings,

I'm new to the K20 powerplant. I just bought a Honda Fit with a complete K20Z3 swap with a BLOX 72mm TB. It has the same OEM MAP sensor like the one above. However, it has a vacant hole in the same location that the OP has placed a grub screw is in. For now, I've covered it with tape to alleviate any vacuum leaks, but the suction is so great that the tape gets sucked in.

I just want to know the original purpose of that hole (I know it looks weird the way I wrote this). At first, I thought it was for another OEM map sensor, but I can't seem to identify another map sensor that will make use of that hole.

Can someone please identify that hole's purpose for me, and also provide the dimensions for the threading so that I can cover the hole with a similar grub-screw if the hole is not needed?
 

·
Registered
Joined
·
24 Posts
Thanks for posting up the charts, good info! I was considering a tb upgrade but not if this will be the end result. I know applications can differ as mentioned, but I'm not going to gamble ~$400 to find out :)
 

·
Registered
Joined
·
219 Posts
Greetings,

I'm new to the K20 powerplant. I just bought a Honda Fit with a complete K20Z3 swap with a BLOX 72mm TB. It has the same OEM MAP sensor like the one above. However, it has a vacant hole in the same location that the OP has placed a grub screw is in. For now, I've covered it with tape to alleviate any vacuum leaks, but the suction is so great that the tape gets sucked in.

I just want to know the original purpose of that hole (I know it looks weird the way I wrote this). At first, I thought it was for another OEM map sensor, but I can't seem to identify another map sensor that will make use of that hole.

Can someone please identify that hole's purpose for me, and also provide the dimensions for the threading so that I can cover the hole with a similar grub-screw if the hole is not needed?
EVAP solenoid
 

·
Registered
Joined
·
377 Posts
head is the biggest restriction on an engine if your head don't flow more than 300cfm you will not benefit from a throttle body over 64 mm. do head work and you will see changes even between the 2 tb you tested
 

·
Registered
Joined
·
377 Posts
ps bigger throttle bodies allow for a faster response power gains will be minimal unless you are turbo or got bolt ons and head work to support it. air is like peanut butter at those speeds and it has to go through small head passages .
 

·
Registered
Joined
·
706 Posts
Love threads like this that make me not want to waste money on a mod I don't really need for my setup. I've been itching for a Hybrid tb just because I don't wanna have the adapter anymore lol. I'll stick with a maxbore oem tb.
 

·
Registered
Joined
·
377 Posts
you need to check your intake air pressure if it stays low you have a restriction before the intake manifold and a throttle body upgrade will help but if you are running a stock rbc rbb or prb head you nead head work first. but as said before you will see faster response but not more power other wise since a biger throttle body will alow for pressure equalization faster than a small one anything bigger than 64mm is a waste and could be detrimental at low to mid range due to reduced velocity with one larger.
 

·
Registered
Joined
·
377 Posts
Will a forced induction installation will make the difference using 70mm + TB ?
I like test like this.....no BS test, thank u
yes the more pressure the more viscous the air due to compression a biger throttle body will allow more air to pass at higher volume
 

·
Arouse the DAMPFHAMMER!
Joined
·
6,266 Posts
Anyone have any experience how these throttle bodies feel. Any issues?
Had both, stock K20A2 TB and 74 mm TB without any problems in operation.

Going from 62 to 74 mm diameter is pretty different in response feeling, as the big TB has a bigger opened cross section compared to the smaller one for the same valve angle. So consequently same foot angle at acceleration pedal = higher MAP. This feels in terms of load response great, but in terms of exact low load control more insensitive.

There are brands offering TB's with a compensation mechanism of above named issue. This works via excentered valve shaft steering mechanism, which I much appreciate for better low load control when DD. For racing this is not a real issue :D.
 
21 - 40 of 61 Posts
Top