Frankacura

There you can see the restriction.
I didnt knew that you can get a 1 3/4" or 2 1/4" restrictor on same kind of headers.
But for the B18 it was absolutly the 1 3/4 that was better.

Frankacura

The ITR 4/1 Headers is at the machine shop. will come out on new 2.5" ID colector...

flesh199

yeah you can buy a small tube or a big tube header...These copy have to version.

non-VTEC

i would have that tri-y collector modified for a tru 2.5" collector with no restriction...

maybe do it to both the tri-y and the ITR and do back to back comparison? hehe

Frankacura

I can do what ever you guys are proposing to me.
But i will need to take also the donation to go whit it ! LOL
I just dont wanna Kill the Tri-Y that i will need for a B20nonvtec 180Whp.
And the 4/1 have longer primary tube so i like it more.
The guy that modify my 4/1 is a great worker so whait to see a F* and nice colector adapted to the 4/1 ITR...
When swaping a VTEC head on my bloc i will probably just pick up a new Tri-Y on bigger colector

wolve

just a pitty that longer primaries improve the pre peaktorque powerband further, opposed to your desire to prolong your power band. also the primary ID determines your peak torque point, and as we all know, the ITR's primaries are not excactly huge...

you'll benefit from the removal of the restriction tough!
custom header with short and stepped primaries in a 4-1 configuration with a 2.5"collector and a megaphone to your 3inch exhaust will probably suit your demands better, by maintaining torque up high

excited to see the outcome on the modded ITR tough!

Frankacura

If the restrictor 1 3/4 was my probleme. the difference will be more than notable

DA BOSS

iTrader: (1)

I don't see that pinch point robbing you of power - and if it does it won't be by much. Even the RMF Narrow has that --- I'm sure Randy would not have made that design if it was a limiting factor - here is a picture of my jet-coated NARROW... you can see the "restrictor" there - it's prob there to create a tad bit of backpressure which you NEED in order to make power.

wolve

wrong, backpressure is ALWAYS bad, however small it may be

1 3/4 is very small, it's as big as a normal primary!!!

the production RMF's narrow has a 2" throat size wich improves the powerband below peak torque. that's why RMF headers made great midrange power for a 4-1 (even more then alot of the quality 4-2-1's), because of the very good scavenging the throat size promoted.

BUT, throat size also limits peak power, simply due to the fact that a certain diameter pipe (throat) can only flow so much whp before becoming a restriction.

therefore, if you have a thoat size (choke point) the size of a normal primary, it's becoming a limitation fast!

this fact also made me sell the RMF copy right after i received it, due to the fact that 400+whp (big nitrous shot) and a 2" throat size is not ideal. it would've became a restriction

DA BOSS

iTrader: (1)

SO you're saying the SIZE of the pinch is the issue - not the fact that there is a pinch there at all. I got it. I misunderstood what you were saying - I thought that the argument was that the idea of that pinch is a flawed design. We're on the same page now.

vtec8200

I think the ''restrictor'' is there for a scavenging effect, and is very important. It would be great to have some input from the members who have built their own header like mar778 and others, this thread is already very informative. Testing is the only way I'm sure you will be porting the flange for anti-reversion and smooth out where the collectors meet.

h23V

good info in here

1.5Slowmatic

wow someone needs correcting. the choke point is not a restriction what so ever. The more of a step you have the better actually. Its not all about flow. Its about the pulses of exhaust gases. Look at the collector on the RMF, notice how long it is? Thats because you want that long collector. The HyTech replica doesn't have this unless you put some sort of extension piece after the collector of the same size.

Heres the SSR street sweeper


ASP header


Bisi



notice anything in common? The choke points and long collectors. Its not all about straight through flow. True header builders understand this and thats why they all share these things in common with each other.

Frankacura

I also do believe that 1 3/4 was very good for my LSVTEC 203Whp.
This headers is probably the raison why i did over 200whp on small 1.8L
Hy velocity in the colector did help but now on bigger motor and bigger flow it become restriction increasing the pressure in the headers runner gething the gaz back in the cylinder
The same tri-Y headers on 2 1/4 colector would be perfect for my 2.2L
But the price of this one is not perfect to my wallet.
And how could be good to cot a little shorter the 4/1 runner and get the end of the 4/1 headers with the Tri-Y desing and 2.5" colector. I mean make a tri-Y with the 4/1 ??

flesh199

like a said to you in the past...sometime something that work well for a 1.8 does not work as well for a 2.0l+engine.


If possible to show picture of the header when it will be ready.

Frankacura

I think i'm gething tired and i should not buy that 4/1 ITR headers as some have said. the primary runner are 1.67" OD as my tri-Y. and the Toda one is 1.9"
So i guess that some of you will just like what im about to say...
I will get a new BIG-TUBE Tri-Y headers

wolve

A choke point (throat size) itself is not a restriction, to small of a throat size WILL become a restriction.

the production RMF header had a 2.0" throat size (choke point) and it worked WELL on many 200+whp setups.

but honestly, do you think bisi runs a 2.0" throat size on his 9sec F22???
why not, because at his power level it WOULD become a restriction.

same reason i did not like the idea of a 2.0" throat size (choke point) at 400+whp for my own setup.

he's running a 1 3/4 throat size, same size as most headers primary diameter. at some level it WILL become a restriction!

choke points are beneficial as do nice collectors, but they have to be somewhat matched to the setup!!! wich in this case is probably not the case!

Frankacura

X2

What.

Men's headers come off the back of the motor...

Frankacura

So i will take the new Tri-Y headers from:
https://honda-tech.com/forums/performance-45/%7E%7E4-2-1-big-tube-tri-y-header-1-8l-2-0l-%2A%2Arace-proven-design%2A%2A-blow-out-2305665/
Unless someone tell me that its not a good idea...

Frankacura

Old headers

New headers

non-VTEC

those will probably work well.......but is the 450usd +dyno time and tuning worth the extra 5-6hp? that's about all i can see that 1/2" "restriction" giving you....

Frankacura

If i was performing 220Whp, i would not try to gain more hp.
But i really think that i'm in suffering past 5500rpm
I think the TQ line must continue to grow till 6500rpm.
So hitting 180tq@6500rpm to start there to lose some of peak TQ numbers and get the HP one around 7700 - 8000rpm and not 6300 - 6500rpm.
STOCK b18b: Engine Type 1.8L, DOHC, 4-cyl., 16-valve
HP, SAE net 140 hp @ 6300 rpm

If that headers is produce for B20 and up... Called Race headers, there is a raison why i should not use the small one...
"These spec are one step bigger than our regular B-series headers. They're best
for 2.0L+ or high rev engines,"

Frankacura

By the way, the small headers was also the good choice if i was to stay on the stock b18b cams...
150tq on B16 headers was possible cuz of the low rpm range. in the top end the hp numbers where not to hight, so the headers did not suffer yet. The velocity was helping to stay at maximum hp even after peak numbers.
Now i think we have lot more than velocity, so some back pressure.

dntnedvtec

you guys have too much knowledge....