Some more info.
All heads checked with no manifolds either side, and trimmed ram tubes to suit each head. All checked with standard lift as per standard cams. Bare ports, with exhaust flowing out! Rb25 wasnt a neo and the variable valve timing wasnt activated for the test so that is a significant factor for the rb25 head right there. In no way was I trying to swing any arguements they are just the raw figures. In personal choice the rb26 head is the go as the inlet design is so far superior to the 2jz but the exhaust seriously lacks in standard form, as with anything these can all be modded but I am not giving away the figures we were able to pull out of the rb26 head. would shock a few people here with just how huge of a potential these can flow, but then you will get the ney sayers that will argue head porting a turbo is a waste of time or you lose down low torque etc etc.
very interesting figures there
also note that the 2J has a lift of 8.61/8.79mm while the 26 im pretty sure is only 8.1/8.2mm??
also, a guy in the the states flowed the 2J and 1J heads and got significantly higher figures than that!!
was done at 400lift (10.16mm) but not sure at what inches of water it was done at tho
his figures read:
std 2J as follows
238@400lift intake
154@400lift exhaust
std 1J
215@400 intake
133@400 exhaust
your 2J figures give a percentage of 87% while his gives 64.7%
granted his tests are done at alot more lift which will give a higher reading
cheers
Troy
also note that the 2J has a lift of 8.61/8.79mm while the 26 im pretty sure is only 8.1/8.2mm??
also, a guy in the the states flowed the 2J and 1J heads and got significantly higher figures than that!!
was done at 400lift (10.16mm) but not sure at what inches of water it was done at tho
his figures read:
std 2J as follows
238@400lift intake
154@400lift exhaust
std 1J
215@400 intake
133@400 exhaust
your 2J figures give a percentage of 87% while his gives 64.7%
granted his tests are done at alot more lift which will give a higher reading
cheers
Troy
A few more side notes for those interested.
The rb26 is one of the highest flowing heads we have tested in terms of cfm for the inlet, now most production cars run at around 70-80% effeciency on the exhaust side but the rb26 is down there, lot of this has to do with the big lump on the inside of the port, so it can be fixed.
I would expect up to 10cfm increase on the rb25 with vvt activated.
The 2jz head is a real strong perfromer however the inlet manifold is garbage so in real world terms i dont think it would be as strong as indicated here.
How is saying the 1jz head outperfroms the 2jz is an idiot the cam timing and lift is lower for starters!
The best factory head we have run at factory specs is definately the early evo mitsu heads with the inlet and exhaust flowing within 5% of each other, and flowing from memory around 130cfm.
Like gary has eluded to testing on a bench fro max number is like a dyno comp. it doesnt matter if you make 30 peak hp more if you dont start making power till 6g when the guy who came second starts making good power at 3.5g, his car is always going to feel and be quicker. When looking at these numbers bear the whole system in mind ie. inlet manifold design, and exhaust manifold design, room for improvements, and how they work in conjunction with a sum of other parts!
Cheers.
Daniel
The rb26 is one of the highest flowing heads we have tested in terms of cfm for the inlet, now most production cars run at around 70-80% effeciency on the exhaust side but the rb26 is down there, lot of this has to do with the big lump on the inside of the port, so it can be fixed.
I would expect up to 10cfm increase on the rb25 with vvt activated.
The 2jz head is a real strong perfromer however the inlet manifold is garbage so in real world terms i dont think it would be as strong as indicated here.
How is saying the 1jz head outperfroms the 2jz is an idiot the cam timing and lift is lower for starters!
The best factory head we have run at factory specs is definately the early evo mitsu heads with the inlet and exhaust flowing within 5% of each other, and flowing from memory around 130cfm.
Like gary has eluded to testing on a bench fro max number is like a dyno comp. it doesnt matter if you make 30 peak hp more if you dont start making power till 6g when the guy who came second starts making good power at 3.5g, his car is always going to feel and be quicker. When looking at these numbers bear the whole system in mind ie. inlet manifold design, and exhaust manifold design, room for improvements, and how they work in conjunction with a sum of other parts!
Cheers.
Daniel
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