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Head Differences: VTEC / i-VTEC Engines

77K views 14 replies 4 participants last post by  MichaelDelaney 
#1 ·
what would be achieved by combining a gsr motor w/a type r head? how would that compare to just buying a jdm type r motor?
thanks!
 
#2 ·
b18c5 head:



with the ITR head (coded as a PR3 head like the b16a and b17a and is just a b16a head that has been ported by Honda), you would have a different flowing head (60% less drag than the b18c1 head) with a higher head volume.



The ITR head volume is 42.7 cc compared to the GSR head at 41.6 cc.

If you have GSR pistons, this larger head volume would lower your static CR to 9.6:1.

The ITR head uses a single stage intake manifold (IM) with different flange mounting holes than the GSR and the intake port is a larger with a steeper throat cut valve angle. It has less aerodynamic drag from having less internal surface area than the GSR head and GSR 2 stage IM. Therefore the flow quality is much better on the ITR. The intake port approach into the combustion chamber is less vertical (you'll hear people say : less of a "straight shot" into the chamber than the GSR head) and directs the mixture motion into the chamber differently . The GSR head's ports are said to be "straight shot" or more vertical or steeper). The ITR head will make more top end power at the sacrifice of some midrange, since it has these characteristics compared to the GSR head attached to the GSR 2 stage IM. This changes, however, when you add a single stage IM and bigger cams however on the GSR head.

Greg Sumaroo stated that with the lower head volume in the GSR head, he finds that it works well with dished pistons in FI applications whereas the ITR head's larger head volume works well in N/A high hp motors using domed pistons that fill in the volume.

Here is a stock (unported) Civic b16a head (so it's not really an ITR head but you get the idea) compared to the GSR b18c1 head on a flowbench which only measures flow quantity and does not account for flow quality:



Notice that the unported b16a (PR3) head is the same in terms of flow volume compared to the unported b18c1 (P72) head...and it's not as dramatically better as people make it out to be. However the ITR head (a ported b16a head with "intake port bowl-blending" and modified valve angles) compared to a ported GSR head shows it's advantage at the upper rpms.




of course, you can have the GSR head ported & polished to flow better than an ITR head and use the Skunk2 single stage IM made to fit onto the GSR head to get the same effect of having less surface area and flow drag leading to better flow quality and more power at the upper rpms.

The ITR and GSR have the same identical rod ratio and so the port sizing for headporting would be similar. They both like long duration cams for N/A packages for the same reason.

Originally posted by Joe Alaniz said:
What I have noticed is that the B16A head has a different bowl shape to it ( compared to the B18C1). If shaped correctly you see really good high lift CFM gains. If you don’t well…. let's just say you gave someone money to just make it look pretty while overlooking this area. Over the years, many porters and head shops say bowls are for low lift, short side for mid lift and runner for high lift. This is where you target to change the flow characteristics at certain lifts. I am sure this applies to many heads but it just goes to show you that Honda heads are finicky. Where you think something shouldn’t work actually works!

one more thing that I have noticed is that on a lot of production multi valve heads, high ports seem to flows better in low to mid lift numbers while ports with a tighter radius tend to flow better at high lifts. I noticed this a lot with motorcycle heads also. They don’t lift very high. on the average they see about 0.300-0.350 in. (7.6 - 8.9mm) of valve lift only. A high port would work extremely well on this type of lift.

I would also like to comment that all of this testing was done a Superflow flow bench. There was no guess work done hear or “I don’t need a flow bench to tell me I’m correct” type attitude.









Quote: Originally posted by Endyn
The GSR head has a larger ID to the intake seat than the B16 head which is intended to feed a 1.8 liter engine...We don't see the differences that some seem to believe exist, with the B16 head being more swirl oriented and the GSR leaning more toward tumble.


on the all-out killer heads, our best head based on a B16 casing will outflow an equivalently prepared GSR by perhaps 5 cfm at .500 lift and that's not enough to cause one to out perform the other in the real world.


The inside diameter of the seat (of an 00-01 ITR head) is also larger than that of a stock B16 head, allowing higher flow rates necessary to feed a 1.8 liter combination.













Practical Stuff Summary:

Part Numbers for Different Head Components



The PR3 Head stamped codes differences:

PR3-2 , PR3-3, and PR3-4 : 89-91 JDM B16A EF8/9, 96-00 OBD-2 Integra Type-R (JDM ,Euro, Asian, USDM)


PR3 - J00 or J51 : 92 JDM Integra B16A EF8/9


an ITR head is a ported B16A head from the factory. Both are coded as PR3 heads. So they are the same head but the ITR one (PR3-2) has had better intake valves, stiffer springs, bigger cams, bigger LMD's, bigger ports, steeper valve angles, some bowl blending work done from the factory.




Ways to identify an ITR/CTR head

* the green paint by the distributor
* thinner ITR intake valvestem (12% lighter vs GSR/Si valve)
* minor port work by the valve seat in the ports
* dual valve springs on both sides (b16a civic and b18c1 gsr heads have only single spring on exhaust side not dual), notice yellow paint on intake side, blue on exhaust side
* lost motion assembly has a blue dot
 
#6 ·
I think you should read the headporting articles and threads here. We got into a long thread about costs. it depends on what you ask the headporter to do..that will determine your cost.

you cn also discuss with the headporter about your IM/TB, cams, redline, CR, the header you plan to use and how you want your powerband to behave and he can shape & size the ports, seat, and bowl to meet your expectations, whether you want a powerband with less compromises in the midrange or not.

Keep in mind, the more midrange you want, the less gains you get up top and vice versa...at least when it comes to N/A motors...FI motors or N/A motors with ITB's are another ball game.
 
#8 ·
bstrin5150 on Nov/07/02 said:
what effect does the 45 degree vs the 60 degree valve seats have?



more flow for upper rpms because it :

- promotes swirl filling (perpendicular to the bore centerline axis), as opposed to tumble filling (parallel to the bore centerline axis) in order to create a stratified charge in the chamber,


- assist in creating a venturi effect for the air:fuel mix to speed up again through the valve throat , after having slowed down in order to bend around the short turn radius (hopefully without mixture separation), as the valve "curtain" opens at low valve lift opening. You see that the 45 is on the long turn radius side where the flow tends to be slower compared to the flow at the floor. To even out the speeds from top to bottom and prevent mixture separation around the bend and down into the throat, you must speed up the flow near the roof (long turn radius).

The result is more flow volume at low valve lift because the port sees more of the combustion chamber, as viewed from the IM side looking down into the port throat.


Some reference terms you should know about valve jobs from www.alaniztechnologies.com :

CoNTINUOUS RADIUS or MULTI-ANGLE VALVE JOB vs. DISCREET 3 ANGLE VALVE JOB

A multi angle valve job is the cutting or grinding of 2 or more angles on the seat and valve. The purpose of a multi angle valve job is to improve airflow. By now you have probably heard of 5 angle and radius valve jobs. The truth is that this is more applicable in the American iron heads. There just isn’t enough material in the small diameter seats or valves to see any real noticeable differences on a flow bench. A 0.5% gain maybe seen on a flowbench but the flowbench has a plus or minus error factor that has to be eliminated before a true flow figure can be attained. Older American iron heads may benefit from a five angle or radius valve job but only because the head is so bad to begin with. The Honda head is different. Our flowbench testing has proven time after time that the correct angles and angle widths are what’s important. More CFM gains have been made through this procedure than applying 5 angles or radiuses.





BOTTOM CUT (THROAT CUT)

The bottom cut is just as it sounds, the cut furthest into the valve-throat area. This cut opens the throat diameter to mate up with the main seating angle. on Honda B16/GSR heads, this angle has the greatest affect on mid to high valve lifts.

BOWL PORT/BOWL BLEND/POCKET PORT (They all mean the same thing.)

This is the most important part of porting a head. This place if done correctly will result in good CFM gains. At the same time one wrong move here will result in a head that flows less than a stock. You can’t make any mistakes here. Our flowbench testing has shown us what to touch and what to leave alone. Most porter’s blend the short sides, as common practice, not realizing some of those edges are what makes the head flow well, as we discovered on an Honda S2000 head. Bumps and sharp edges are not bad all the time. once again flowbench testing helped us determine this.
 
#10 ·
From the Intake Valve Seat Angles Article:






the seat is 45 degrees and has a width range of 0.049-0.061 in. The service limit is 0.08 in. or 2mm. The actual seating area is less than this width range (usually 0.040-0.045 in.) and can be visualized using Prussian Blue dye applied on the back of the valveface on it's seat area and then snapping open and close the valve onto the valve seat in the cylinder head several times. The dye leaves the imprint of the seat width behind.

The typical throat cut is 60 degrees. By altering the angle to 45 degrees, if you look from the IM side of the port and through the port throat, the passageway "window" will "see" more of the combustion chamber at valve lifts below 25-33% net lift (or below 0.15 mm lift).

Endyn uses a throat cut that is even less steep at 38 degrees, followed by the discreet 45 degrees for the seat (which is narrowed down to a width of 0.045 in. instead of the stock minimum of 0.049 in. but he extends the 45 degrees to the next cut), then to 58 degrees top cut, and finally, they use an additional top cut angle (65 degrees on the short turn radius side and 70 degrees on the long turn radius side). They believe that if you run a less steep angle on the short turn side, the flow at the floor of the port will slow down and allow the flow at the port roof to catch up. This prevents mixture separation and also allows the air:fuel mixture to "roll" into the chamber in a swirl motion. Endyn blends these last 2 angles so that they are not as discreetly separated or concentric into the combustion chamber bowl. This is where the majority of gains are seen from 50% to 100% net lift.

So instead of the typical 60-45-30 angles on the stock 3rd gen. GSR P72 head or 70-45-30 on domestic heads, you get (38 to 45)- 45 (seat) -58-(65-70).

Other benefits to the 45 degrees extension?: A wider valve seat transfers more heat to the head where it can be shed than a narrower seat and will pound the valve backface less over time ...a good thing in terms of durability.

Remember also that the blending of the top cut angle(s) into the (polished) head bowl is also where Honda does most of it's porting on the B16A (PR3) head to get more flow gains in the upper rpms and more cfm at high valve lifts compared to the GSR P72 head instead of opening up the port volumes themselves, although the later factory ITR head porting had the ports enlarged further compared to the 97-99 ITR's with the casting flaws removed as well.


It appears that Endyn places a (reversion dam -like) step below the throat cut or at the throat cut that is 90 degrees. The width of this radius above the throat cut is proprietary. This is thought to prevent reversion up the intake port during low intake lift while the engine cycle is still in the compression stroke. It is a unique approach and I am not aware of anyone else using it.

he best way to kill reversion on the intake valve is to simply put a 90 degree angle on the side of the valve head. (flat with sharp edge margin to chamber side) We've never seen any worthwhile results from trenching the chamber side of the intake valve.

Valve shapes were the first place most of us began looking for reduction in reverse flow.

Intake valves like to have "square" edges...with the corner defining the break from the chamber side of the head to the margin being 90 degrees (or less) with a sharp edge (no radius) and the corner defining the break from the margin to the face angle being equally sharp.






Joe Alaniz trials different margin thicknesses in addition to altering the back cut.



Quote:
According to Alaniz, up to 50 percent of flow increases from head work can come from a proper valve job. Many believe that a thin 45-degree face on the valve is the way to go, and it does help at a specific valve lift. But by keeping the face a certain thickness, overall performance is improved. Alaniz also says that valve widths are equally important to maximizing flow.

Another pointer he gives us for intake valves relates to the thickness of the margins, which affect the way air passes by the valve. A correct thickness will allow air to flow smoothly past the valve, while an incorrect width will cause passing air to tumble as it comes off the edge, making for inefficient flow.


cheers
 
#11 ·
In a Straight Shot port, the design allows for a line of sight from the inlet directly to the front opening of the intake valve. Sometimes this design gives a lower flow value but because it is straight, we attain higher velocity of fuel/air entering chamber. It also creates a turbulent spin or swirling in the combustion chamber, yielding a more efficient and more complete burn.

A High Approach port is where a turn is necessary in the port design. The term "high approach" comes from angle of the last section of the port relative to the valve - it is more in-line with the valve stem.


The interesting observation by Joe Alaniz is "high ports" tend to flow better at low to mid valve lift ranges. Whereas the ports with "tighter radiuses" flow better at high lifts.

By flow better,here, we mean more flow volume (in cubic ft. per minute or cfm). There is no comment about flow quality and mixture separation after the short turn radius.

If I interprete what "high ports" means correctly, then the straight shot or more vertical port in the 3rd gen. GSR P72 head would prefer a cam with less lift than an ITR/2nd gen GSR/Si PR3 head.

I find this comment a bit of a paradox given the fact that Erick runs an Alaniz-ported P72 (3rd gen. GSR) head with Toda "Spec D" cams with a huge intake max. lift of 12.9 mm and the valve is open for a looong time.

So, I don't know if Joe has revised his thoughts on this comment after Erick broke the all motor Honda 1/4 mile record time at 10.59 sec. or whether he has altered the shape or seat angles to compensate for this to get more mid to high valve lift flow. Obviously he's not going to be telling us anything about his trade secrets.
 
#12 ·
Notice also the profile of the Spec R intake valve on the Japanese Honda diagram of the CTR 45 degree seat angle. Less of the valve is occupying space that would otherwise be filled with air fuel mix bathing around and above it. The valve face is much "flatter" or less tulip-shaped at the stem connection on profile or sideview. You get more of a venturi effect with a 45 occurs compared to a 60 when using this flatter profile valve. We call this flattened profile a back cut valve.

Less valve material also means less weight.

I've been advised however to not back cut my valves for durability reasons.


photo of the air fuel mix going around an opening valve and the venturi effect.

 
#14 ·


yes. any reputable, experienced Honda headporter will have a $50,000 Serdi cutter which precisely cuts the seat angles to the desired number with the widths of the seat having identical widths to within 0.001 in. tolerance. There is no hand cutting tool used when you go and get a proper 3 angle valve job.


Mike Kojima said:
The best valve jobs are done on a Serdi machine. The Serdi is very high precision which insures that all the valve angles and depths come out equal. Most low price shops use stones. Stones can give a good valve job but the stones must be dressed frequently and dial indicators must be used to insure that the seating surface remains concentric. Stones require a highly skilled person who is conscientious of doing a good job. A butcher can make a big mess with stones.


Portflow, Alaniz Technologies, Skunk2, AEBS, R&D, Leitner & Bush (in Canada), are some common names you hear who do these precisely to your desired powerband location gains.

It's (i.e. valve seat angle modification and bowl blending into the top cut valve seat) the biggest bang to the buck for headporting gains in the upper rpm powerband.

Here is an example of an imprecise valve angle job. Note that the right intake port throat cut width is not the same as the one on the left intake port :

 
#15 ·
To keep this thread current, we need to start compiling Kseries data on the JDM K20A, RSX Type S K20A2, and TSX K24A2 i-VTEC heads.: head volumes, valve diameters, cam specs, port volumes & EGR porting, etc. just like we have done so thus far on the Bseries heads.



For example, the DC5 chassis ITR has different cams and dual valve springs compared to the the RSX Type S cams and dual valve springs located only on the intake side.

K series head swapping is already a common thing.
 
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