Ok guys here some more info to chew on. Check out all the pics. I really like the factory valve job and the port design. The valve guide bosses are flush and the core shift is much better. The machine work in the bowl area (below the valve seat) is also much nicer. The intake has a nice angled entry, providing a nice straight shot at the back of the valve. The exhaust port also has a slight angle to it. The major difference is the exhaust side on the X. The exh. valve is smaller, the throat is smaller, and the ports are smaller. It seems to be optimized to the stock turbo and it might become a restriction at big horsepower. It does look like there is a lot of material around the port to do some work so that is a plus.

First two pics are the evo X and VIII intake valves. Shows the X being 1mm larger valve





Next Exhaust valves, the EVO X has a smaller exhaust valve.

























-Martin

 

Good info Martin! So the head on the X is more restrictive than the IX?

 

Awesome pics! Great detail....

 

I'd say it is.

On the intake side, it seems that the X has more room to get air, but then it has significantly less room to get the combustion out. The ratio of intake to exhaust sizes is more significant than the VIII (which appears more "balanced") and indeed seems to indicate they designed the head around the stock turbo.

This seems like it will become a problem when upgrading to a larger turbo to get big power.

 

Like martin said the head flows very well but due to port sizes it might become a restriction when making bigger power. There is room to improve it though...and you know we will

Eric

 

I am sure your were bouncing in your little chair from all the excitment you get from this. First off its exhaust valves are a little bit smaller, if you read the OP, and looked at the pics, then you should know that ams said that there is alot room arround the port to port it out even more. But you failed to say that why? And then you just repeat what was said about it being a problem with big power.
Honestlly, I dont uderstand you man. You knock the car so much. Hey thats your opinion and right. But your just so dumb, because these shops are posting 100hp+ gains over stock. I think its safe to say that the amount of hp these shops are gaining with the amount of mods, are for sure more repsonsive then any other evo period. How can you not see that its black and white. Please for the sake of this forum. Stop posting in these sections. You dont like the X, everyone gets it. Go post in other sections, so that the X forums are not littered with your BS. Let me guess Off topic.

 

That's going to make for some interesting aftermarket head work. I can't wait to see all the hype around ported 'race' heads for the Evo X. Let the games begin!!

Thanks for posting the info, Martin.

l8r)

 

It sure will Markus. There is allot of room for porting and whatnot on the head. Makes me feel all warm inside lol

Eric

 

I was under the impression that narrower exhaust ports helped increase exhaust gas velocity and effectively reducing lag. How LONG are the exhaust ports compared to the IX? If its shorter on the X, can we assume that if someone (like less than 20% of Evo owners) decides to go with a 35r or bigger, he will have better results from porting the X head than someone would experience on the IX? This is of course assuming there is enough area to safely port. I think for the X's intended purpose (a better track car and a superior sports sedan), it is a step in the right direction. Sort of like with motorcycles where on many occassions, engineers reduce the size of exhaust valves and ports or expand them model to model, year to year. They are only getting better.

When will we see the head flow bench test comparison? I'm sure Cosworth will release flow data in the next few months.

 

There is ALWAYS room for improvement with EVERY car. That's not the point of this thread. The comparisons are stock-for-stock.

What does that have to do with the limits of the head with bigger turbo? Which is what I was commenting on.

Dude, I don't know what your problem is but let it go.

I have a right to comment about whatever I want.

I know the head flows pretty well, and I know the car has made some really good results but you can't expect the X to be perfect. Nor should you be offended because people comment on its shortcomings. For the last time, I don't hate the X, I just don't think it's perfect like some purchasers on these boards want it to be.

-M

 

Yeap, that's exactly what I was thinking. Probably why the car feels very impressive in the low end powerband. Must be really nice to drive around in traffic!

 

Kudos to NoTec. I was thinking the same thing. Mitsu maybe going the extra mile for that faster spooling turbo. I dont know that we are going to really know how well the head flows without putting it on a flow bench. I guess you could measure volume. But how can you measure the effect of mivec on the exhaust side ? if the mivec holds the exhaust valve open longer than the size of the port is kind of mute, isnt it ?

 

Hmm, narrower exhaust valves, but larger intake valves AND a much larger diameter combustion chamber. I'd say that the head seems to flow better overall than the 9, but that at the 500+ level, my guess is that martin might be right that it could be a little restrictive. We will have to see, though, because the other aspects of the head seem to actually flow better than the 9. We will see when we get there, I suppose.

 

Thanks, I think it is a better design for a street car and better for X owners in general. It wont really suck too bad because it will benefit those who will never go bigger than a 20G sized turbo. As stated before, short of 500+ hp, the design will probably be sufficient. The Mivec issue is different and I am not too sure if I agree with your last sentence. I know the guys in the Ecuflash forum have a 400+ post topic going explaining mivec and how it works inthe IX. Also a lot of very interesting maps floating around in there. I personally have seen gains of damn near 30 hp and 35 tq in parts of my powerband from tweeking the mivec map. Not sure if it works the same in the X though.

When will the EVO get mivec that controls lift TOO?????

 

First off...are you qualified to even say that? Second...what are you basing your comment on? The fact that it has a smaller exhaust valve?

The EVO 4G head has highly unusual intake to exhuast flow ratio when compared to most motors. On my bench the intake flows 208cfm @ 28" and the exhaust flows 198. The general rule of thumb passed down for ages has been that exhaust flow should be 80% of intake flow...but I can tell you right now that a Pro Stock head has a much lower exhaust flow percentage.

On my alcohol Honda motor we originally ran a 2mm os intake valve and 1mm os exhaust valve...and we picked up power on the dyno going to a 3mm os intake valve and 1mm UNDER stock valve...increased intake flow by 20cfm and lost 15 on the exhaust. The cold air coming in moves through the port differently than the hot air exiting, and is a lot more to take into consideration than just the size of the silly damn exhaust valve....the shape of the port, the length, the cross section, how the bowl area and short turn transitions into the seat, etc. They probably increased velocity...and yeah it is probably designed to optimise performance with the small factory turbo. But less efficient than a 4G? That is a pretty tall order to fill to make something flow worse than that

A little off topic, but while I'm talking about this goo...the 4G has some issues that most machine shops and head porters overlook. One of those is that you can NOT do proper valvejob on a 4G head without using a torque plate to simulate the head being torqued to the block. If you do one without the plate, the instant you torque the head to the block the seat is deformed and won't seal properly. I see it all the time. Guys do a real nice valvejob, vacuum test it and it seals with flying colors, then they install the head and the motor leaks down 15-20%. A VJ with a torque plate will achieve a near perfect seal after the head is torqued. That problem is taken futher when guys do a 1m os valve without installing a larger seat...happens all the time and there is lots of power to be had in simply doing a proper valve job

Cheers