Honduh Chicken

I read this in the ITR forum.

"Naturally, porting and polishing excessively won't yield good results -- it will only upset the balance between displacement and peak rpm's. Some basic physics explained... In any cylindrical enclosure/piping, the closer air is to the metal wall, it will flow slower, and the closer it is to the center of the cylinder, it will flow faster. As rpm's increase, slight variations in the enclosure will cause for serious air flow disturbances. Logically speaking, a straight, cylindrical port would prevent any problems of air-flow disturbance, but with street cars and their limited engine bay space, the port has to be bent. The stock port is built to within such precision that it can already withstand rpm's of up to 7,000 rpm without creating any unwanted air-flow disturbances, but once it reaches 8,500 rpm, the engine struggles to keep the air flowing smoothly. To augment this problem, two of the best mechanics at Honda were selected and assigned to manually port and polish the engine components. Though this limits production to 25 engines a day, this allows for the engine to reach 8,500 rpm, and respectively, 200 horsepower. For those of us who want to port and polish our GS-R engine parts, unfortunately, Honda would not disclose to us the details of this procedure.
Next, the valves and the valve springs needed to be upgraded in order to be able to withstand the high rpm's and the increased fuel injection. In order to increase air flow efficiency, the angle of the valve seat opening was tightened from 60 to 45 degrees. Also, bigger and lighter valves help to deliver more fuel. Instead of making the valve bigger, Honda engineers made the cone bigger and reduced the stem radius even further. In specific, the underside of the valve cone was shaved to its limit, and the valve shaft width was decreased from 5.5mm to 4.6mm -- making the valve 12% lighter than stock. Amazingly, the valves are made so precisely that their static balance differential is basically 0.0. We jokingly asked Mr. Suga what he would do if Honda's parts manufacturers sent over valves that had weight differences. His reply was quick and simple. "We would toss them out." Hm... very strict. Past 8,000 rpm, other valve-related problems occur. Such problems include surging, jumping, bouncing, etc... In order to prevent such problems, the valve springs are made by dual-bound springs. Furthermore, Honda used non-cylindrical, "flat" springs in order to keep the spring height near-stock, and still increase rebounding power.
The camshaft lift amount was changed for both intake and exhaust valves. The intake lift was increased from 10.6mm to 11.5mm, and the exhaust lift was increased from 9.4mm to 10.5mm. To compensate, the intake opening timing was increased from 10 to 15 degrees before piston apex, and closing timing was increased from 40 to 45 degrees after the piston reaching base. Likewise, the exhaust opening timing was increased from 40 to 45 degrees before the piston reaching base, and the closing timing was increased from 7 to 10 degrees after piston apex. By doing so, the valves remain open longer -- allowing for more air to enter the combustion chamber.

Two of the best mechanics at Honda port and polish the manifolds by hand in order to create a high-rpm engine. Due to the manual process, only 25 engines a day can be created.

The intake port was simplified from a dual-port to a single-port -- in hopes of making high-speed air flow better. The stock exhaust piping that varied in width from 48.6mm~50.8mm was upgraded to a full piping with 57.2mm width all the way. Furthermore, the fully stainless-steel header a-pipe employs a 4-2-1 design, but with no sharp edges in the A-pipe when going from 2 to 1. This is a feature that is said to be impossible to do in mass-production."

and my question is..

I just built a head for my boosted GSR. I used ferrea valves, 1mm over intake and .5mm on exhaust. Ferrea dual (flat) springs and hardware. 70mm throttle body, skunk2 intake manifold.

Since my upgrades weren't engineered by honda and hand ported and polished at the factory, how do you think my head will stack up as far as efficency? I'm not concerned nor am I asking how much power it will make, or if it is better or worse than the ITR head. but I am asking if you think using high-end after market components on a GSR head will be as efficent as an ITR head?


EDIT: BTW this is a forced induction application

Honduh Chicken

bump..

Lucky_Smurf

They should stack up pretty well as far as efficiency goes. You've got to remember your trying to flow a lot more air than a stock ITR. Also from what I understand the ITR head is a b16 head cast with upgraded valve train components.

Honduh Chicken

So you CAN mix-match after market products with good results? Because from what I know, when honda builds an engine, everything was engineered to work togeather, valves, intake manifold, throttle body, when you start changing everything does it start messing with the air flow causing it to draw air with disturbances etc?

m R g S r

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Lucky_Smurf &raquo;</TD></TR><TR><TD CLASS="quote">They should stack up pretty well as far as efficiency goes. You've got to remember your trying to flow a lot more air than a stock ITR. Also from what I understand the ITR head is a b16 head cast with upgraded valve train components. </TD></TR></TABLE>


Same cast, different porting.

Lucky_Smurf

Mixing and matching components in a valve train should cause you too many problems as long as you are specific about what you want and get components that are meant for the application. However somethings are meant to go together. For example I wouldn't by springs from one place then retainers from another. Also if your looking at cams your gonna need to worry about clearances. So make sure the shop that's doing your work is aware of that.

Honduh Chicken

well my valve train is all ferrea, my cams are stock GSR. What I ment by mix-match was skunk 2 intake manifold, ferrea valves, etc. I know it doesn't matter who makes what.. but I ment using parts that were not designed to work togeather.. like the skunk 2 manifold wasn't ment to flow air through different sized valves etc.. Is all that after market stuff throughly tested? or is a skunk 2 manifold just designed and welded togeather based on the principal that bigger and straighter flows better?

Lucky_Smurf

They are usually tested pretty well. I know a lot of people make a lot more power with an aftermarket intake in the upper rpm range. If that helps.

97ITR60

The head is the same cast but the stock heads were supposed to be hand ported and polished as opposed to the b16. it is not only a difference in the valvetrain or cams. If you buy a ITR head from the dealer they are not hand done or so I have heard. My four cents...not just two because I heard this from a honda mech at R&D.