Here it is, the real deal.

Just had the EVO X and the EVO 8 head flow benched. I knew by looking at the EVO X ports, valve job, and the bowl area that the number would be good.

The testing was done a Superflow FS-600 at 25" of water. All CFM values where scaled to 28" of water to compare to common advertised figures. A proper bore adapter was made to represent the cylinder bore and it was flowed every .050" of lift. Low lift flow is also important so we started at .050" of lift




Intake side

Lift EVO 8 EVO X
.050" 41.6 56.85
.100" 80.5 101.1
.150" 119.1 147.2
.200" 152.7 185.7
.250" 182.6 215.6
.300" 201.5 234.8
.350" 209.4 252.5
.400" 210.9 265.7
.450" 204.6 274.5
.500" 206.2 280.2

Exhaust Side

Lift EVO 8 EVO X
.050" 34.5 34.1
.100" 67.4 74.1
.150" 104.8 127.8
.200" 138.5 156.8
.250" 172.5 160.8
.300" 192.1 182.6
.350" 202.6 185.9
.400" 207.7 189.3
.450" 209.4 190.9
.500" 211.0 192.6


Here are the graphs









You can see how superior the intake side is to the EVO 8. The exhaust side on the X has better low lift flow but gives up at higher lifts. I'm still impressed with the flow even for looking like small exhaust ports.

 

head flow numbers of the exhaust are interesting, what does this mean when you change the exhaust? I assume nothing right since this is at the head of the car.

 

I remember reading somewhere that Mitsu beefed up the intake and shrank down the exhaust for "economic/enviro" reasons.....guess this proves it.

 

wow, good info

 

Martin, do you have any idea how those flow numbers compare with a good ported 8 head, eg. cosworth head.

 

I can give my experiences. I flow a little different but I have come up with similar numbers. I flow at 50 inches and then convert to 28. It is more accurate and is more real world. You'll notice that Cosworths charts on their site are all given at 50.

An EVO 8 head on my bench flows nearly identical to what Martin posted...208 for me. A Cosworth head on my bench flows around 265 and the X head is better all over. The best 8/9 head that I have seen on my bench was just short of 290cfm...but it was no joke at all.

People are worried about the exhaust flow being lower on the X...I can assure you that this was by design for power...not just emissions. The EVO 8 head was very unconventional in how well the exhaust flowed compared to the intakes poor flow. You should see this sucker flow with a good valve job and short turn. The exhaust side cleans up nicely! I'll post charts of X vs 8 vs valvejob X, vs Cosworth8 vs ported X as soon as I stop being lazy

 

^I look forward to it.

 

Impressive, now JUN/HKS/GSC need to release some cams for it :P

 

what about compared to the Evo IX head?

 

Flows identical to the 8

 

Interesting indeed!

 

I wonder how much you could squeez out of the X head...full port job ect.

 

one interesting thing to not is how the stock EVO 8 intake flow actually drops a bit over .400" of lift. Something to think about when installing high lift cams on a stock head. I've seen good results with Jun 272 cams even on stock heads, these cams keep lift low but maximize the are under the lift curve. To really take advantage of the high lift cams they would need a good ported head.

 

so would you say that the jun 272 would be to big of a cams for the stock evo8 head?

 

Not at all. The only thing to watch for it spring retainer to valve guide seal clearance. From my measurements even most small lift cams will come very close to if not make contact with the guide seal. This can lead to damage to the seal and cause oil consumption through the guide.