DIY H23 ITB's

[wed3k]

I might be interested in them, since my supercharger project isnt a good idea for a daily driver.

ill probably be nice and fabricate the tps mount for you :o

i think thats it? other than plugging some holes to utilize them for the vacuum block.
argh, i still have to call the guy.

[wed3k]

i hope i can get it this thursday.

ill either fuck around with them more and then sell it out....but at least take pictures of them mounted on a block.

[wed3k]

finally got them back, the guy didnt even start the project. he cut the fucking runners and that was it. what a fucking joke but at least he didnt charge me anything.

anyways, im gonna get ready to do more reasearch for runner length because i may be shooting for 8000-9000rpm on a h23 head swap setup along with a race header. as well as angling them upwards a tiny bit. muhhahahahah

[vi.descending]

think about it.....what car...let me rephrase it...what JDM car has ITBs and TWIN TURBOS???????? NON HONDA PRODUCT...


think maroon...think...its not that hard...what JDM "ONLY" car has ITBs and TWIN TURBOS ( wont pass emissions in the US )

Has noone got this yet?

I am dissapointed.

Seriously.

RB26DETT - SKYLINE GTR.

Thats the easiest question I have ever answered on this site LOL.

[NAiL05]

BMW lol. All of them come with ITB stock well most of them. Dunno bout the new boosted 3 series though i would assume they got them too.

[wed3k]

what the fuck are you guys even talking about?

[vi.descending]

BMW lol. All of them come with ITB stock well most of them. Dunno bout the new boosted 3 series though i would assume they got them too.

I dont know about the new ones, BUT the old M series (inline six) engines had ITB's.

what the fuck are you guys even talking about?

I DONT KNOW !!!!

[gloryaccordy]

BMW lol. All of them come with ITB stock well most of them. Dunno bout the new boosted 3 series though i would assume they got them too.

The new 3 series has no throttles... it has infinite stage "VTEC"

[Rosko]

FYI the "harmonic wave" someone was talking about is a sound wave. When the intake valve closes the incoming charge has no where to go and the resonant sound wave heads back up the runner. When it reaches the end of the runner it turns around (don't ask me how, lol) and heads back for the intake valve, thats ONE wave. Runner length will determine how many times this wave will travel up and down the runner before the intake valve opens again. Ideally it has been said to tune the runner length to the 3rd or 4th wave so that when this wave returns to the intake valve either the 3rd or 4th time the valve will be opening and the wave will carry the mixture in along with it. Thats near impossible to do though on most cars.


The first thing you need to figure is how long it is from the time the intake valve closes to when it opens again. You will need to know the duration of the cam and where it will make peak power. Idk what you have for cams so I'll use a stock H23 cam as an example which has an intake duration of 240 degrees. I'll guestimate that peak power will be made at 6000 rpm's Keep in mind that the intake valve only opens every 720 degrees of crank rotation (every other revolution) So at 6k rmp it takes the engine .02 seconds to make one complete 720 degree engine cycle.

60 / 6000 = .01 seconds per rev (60 secs in a minute / rpm)
2revs / cycle = .02 seconds per 720 degree cycle

Since we know the intake valve is open for 240 degrees, we know it is closed for 480 degrees

720-240=480 degrees between intake closing and opening

we already figured out that @6krpm it takes .02 seconds to complete a cylce, so we can backfigure how long it would take to go 480 degrees

.02 X 480 = 9.6
9.6 / 720 = .0133 seconds between valve closing and opening.

Now that you know that we need to figure out how far the sound wave can travel in that amount of time. The speed of sound (at sea level and 70 degrees farenheit) is 1128 feet per second

1128 X 12 = 13536 inches per second

So we want to figure how many inches that equals in .0133 seconds.

13526 X .0133 = roughly 180 inches

you can divide that number by two since the wave goes all the way up the runner and back down.

180/2 = 90 inches

Obviously you can't fit a 90 inch runner under the hood so that is where the multiple waves come into play. It has been said that the 3rd or 4th wave is the best to go with but thats just not possible to fit under the hood, and especially with an itb setup. So what you want is for your runner length to be a multiple of that (90 inches in this case) like so...

90 = 1 wave
45 = 2 waves
30 = 3 waves
22.5 = 4 waves
18.0 = 5 waves
15.0 = 6 waves
12.85 = 7 waves

Also keep in mind that the actual length is not really the runner length, but the distance from the valve head to the end of the velocity stack. I would guesstimate that its about 3 inches from the manifold flange to the valve head, so if you were tuning for the 6th wave your manifold would be about 12 inches long, the 7th wave would be 9.85 inches long from flange to v-stack.

The more waves you let go by the more it loses its effectiveness, so in your case you might want to tune for the 6th wave with a 12 inch long manifold. Using a runner slightly longer than that will lower your power band UNTIL it comes into range of hitting on the 7th wave. You could if you wanted to backfigure from the runner you have now to determine what rpm range it will perform best at.

If you want to get really technical figure up the speed of sound at your sea level and temperature. It can also get more involved when you start to think of runner length from the velocity stack to the top of the piston and how it affects things as the piston is dropping in the cylinder but this is just a starting point.

Hope some of that makes sense, lol

[wed3k]

FYI the "harmonic wave" someone was talking about is a sound wave. When the intake valve closes the incoming charge has no where to go and the resonant sound wave heads back up the runner. When it reaches the end of the runner it turns around (don't ask me how, lol) and heads back for the intake valve, thats ONE wave. Runner length will determine how many times this wave will travel up and down the runner before the intake valve opens again. Ideally it has been said to tune the runner length to the 3rd or 4th wave so that when this wave returns to the intake valve either the 3rd or 4th time the valve will be opening and the wave will carry the mixture in along with it. Thats near impossible to do though on most cars.


The first thing you need to figure is how long it is from the time the intake valve closes to when it opens again. You will need to know the duration of the cam and where it will make peak power. Idk what you have for cams so I'll use a stock H23 cam as an example which has an intake duration of 240 degrees. I'll guestimate that peak power will be made at 6000 rpm's Keep in mind that the intake valve only opens every 720 degrees of crank rotation (every other revolution) So at 6k rmp it takes the engine .02 seconds to make one complete 720 degree engine cycle.

60 / 6000 = .01 seconds per rev (60 secs in a minute / rpm)
2revs / cycle = .02 seconds per 720 degree cycle

Since we know the intake valve is open for 240 degrees, we know it is closed for 480 degrees

720-240=480 degrees between intake closing and opening

we already figured out that @6krpm it takes .02 seconds to complete a cylce, so we can backfigure how long it would take to go 480 degrees

.02 X 480 = 9.6
9.6 / 720 = .0133 seconds between valve closing and opening.

Now that you know that we need to figure out how far the sound wave can travel in that amount of time. The speed of sound (at sea level and 70 degrees farenheit) is 1128 feet per second

1128 X 12 = 13536 inches per second

So we want to figure how many inches that equals in .0133 seconds.

13526 X .0133 = roughly 180 inches

you can divide that number by two since the wave goes all the way up the runner and back down.

180/2 = 90 inches

Obviously you can't fit a 90 inch runner under the hood so that is where the multiple waves come into play. It has been said that the 3rd or 4th wave is the best to go with but thats just not possible to fit under the hood, and especially with an itb setup. So what you want is for your runner length to be a multiple of that (90 inches in this case) like so...

90 = 1 wave
45 = 2 waves
30 = 3 waves
22.5 = 4 waves
18.0 = 5 waves
15.0 = 6 waves
12.85 = 7 waves

Also keep in mind that the actual length is not really the runner length, but the distance from the valve head to the end of the velocity stack. I would guesstimate that its about 3 inches from the manifold flange to the valve head, so if you were tuning for the 6th wave your manifold would be about 12 inches long, the 7th wave would be 9.85 inches long from flange to v-stack.

The more waves you let go by the more it loses its effectiveness, so in your case you might want to tune for the 6th wave with a 12 inch long manifold. Using a runner slightly longer than that will lower your power band UNTIL it comes into range of hitting on the 7th wave. You could if you wanted to backfigure from the runner you have now to determine what rpm range it will perform best at.

If you want to get really technical figure up the speed of sound at your sea level and temperature. It can also get more involved when you start to think of runner length from the velocity stack to the top of the piston and how it affects things as the piston is dropping in the cylinder but this is just a starting point.

Hope some of that makes sense, lol

thats what i was going for in terms of changing my aluminum runner length...12"

ive decided to not rig this and just cut it at the flange, cut the TB's, extend them.

extend the runners, custom make a fuel rail mount and the such. of course this will take much longer espeicially with turbo plans in front of me.
so yea, just a little bit of an update. ill probabbly get aorund to cutting the manifold soon though.

[Rosko]

the rail mounts aren't too bad to fab. I cnc'd a set for a friend on H-T awhile ago. I wouldn't reccomend welding the t.b's on though (not that you were) That was a problem with his, the t.b. distorted a little and wouldn't quite shut completely right. The flange will likely warp as well and will need to be machined afterwards if the welder isn't careful.

[wed3k]

the rail mounts aren't too bad to fab. I cnc'd a set for a friend on H-T awhile ago. I wouldn't reccomend welding the t.b's on though (not that you were) That was a problem with his, the t.b. distorted a little and wouldn't quite shut completely right. The flange will likely warp as well and will need to be machined afterwards if the welder isn't careful.

yea, im attaching the tb's via silicone couplers.

the flange...im not sure what we'd use to surface it. we have a huge belt sander for cast iron exhaust manifolds, deck resurfacer or mill.

[HondaFan81]

wed3K:

Temporarily banned for your "riggin" comment, which I edited. Not a wise choice in words, very immature.

[wed3k]

anyways...

got the manifold cut on the bandsaw
i gotta do more calculations for runner length, get the flange milled, get them runners to be oval shaped and tig it up.



anyone interested to buy a starting set as well? i have an extra f22 mani i could hack up. i would need runner length as well.

[wed3k]

damn, i didnt even post my jig to cut this damn thing

next is milling the runners straight and figuring out runner length and runner fitment.