macca
03-14-2009, 10:21 PM
I thought these pictures might be of interest to some people on here.
It shows similar cut-through photos of three different heads. There is the 2JZ-GTE head from a mk4 Supra TT, the RB26 head from a GT-R R34 Skyline and the BMW E46 M3 head.
Obviously the Toyota and Nissan are from a similar era but the BMW shows a good example of how technology has gone on in engine design and building since the mid-90's.
So, on with the show:
http://www.i-macca.co.uk/stuff/Head%20cut-away%20Toyota%20Supra%202JZ-GTE.jpg
This is the 2JZ-GTE head cut away halfway through the last two valves in-line on the head.
You can see the flow through the ports is very good for an engine of it's age, the ports are on the large side and there's little to be gained from work inside the ports for extra flow. Small bits here and there will help though.
http://www.i-macca.co.uk/stuff/Head%20cut-away%20Nissan%20Skyline%20RB26.jpg
http://www.i-macca.co.uk/stuff/Head%20cut-away%20Nissan%20Skyline%20RB26%202.jpg
This is a head cut-through from an RB26 Skyline R34 GT-R engine. You can see that the inlet port is quite nice for gas flow, smooth and large which is helpful for a turbocharged engine. It could benefit from a small amount of work around the valve seat area but is generally good.
However, the exhaust side is pretty bad and needs a lot of work to try and regain some flow out through these ports. The port is quite narrow in to small openings for the manifold and also not smooth and straight but with 'steps' along the top and bottom of the port. Not good! Luckily there is plenty of meat around the port for modifications to be made to enhance it.
http://www.i-macca.co.uk/stuff/Head%20cut-away%20BMW%20E46%20M3.jpg
And last but not least, this is the inlet side of the BMW E46 M3 head. Bearing in mind, this is designed as a purely normally aspirated head as opposed to the above two that were designed as turbocharged heads.
Nice long and smooth ports flowing directly to the valve seat area, creating a nice gas flow in the top of the combustion chamber, ideal for a nice lean burn. Knife-edging can just be seen where the two ports for the pair of inlet valves seperate down, good for not disrupting flow and causing turbulence as the gases pass the valves.
Another thing to note is the comparitively short valve stem guide. This keeps it out of the way of the gas flow, keeping the gas speed up and minimising turbulence. You can get away with smaller bosses more in a normally aspirated head as the heat build-up is nowhere near as bad. Longer bosses help to dissipate heat better from the valves in to the head and away from the combustion chamber, lowering chances of detonation occuring.
It shows similar cut-through photos of three different heads. There is the 2JZ-GTE head from a mk4 Supra TT, the RB26 head from a GT-R R34 Skyline and the BMW E46 M3 head.
Obviously the Toyota and Nissan are from a similar era but the BMW shows a good example of how technology has gone on in engine design and building since the mid-90's.
So, on with the show:
http://www.i-macca.co.uk/stuff/Head%20cut-away%20Toyota%20Supra%202JZ-GTE.jpg
This is the 2JZ-GTE head cut away halfway through the last two valves in-line on the head.
You can see the flow through the ports is very good for an engine of it's age, the ports are on the large side and there's little to be gained from work inside the ports for extra flow. Small bits here and there will help though.
http://www.i-macca.co.uk/stuff/Head%20cut-away%20Nissan%20Skyline%20RB26.jpg
http://www.i-macca.co.uk/stuff/Head%20cut-away%20Nissan%20Skyline%20RB26%202.jpg
This is a head cut-through from an RB26 Skyline R34 GT-R engine. You can see that the inlet port is quite nice for gas flow, smooth and large which is helpful for a turbocharged engine. It could benefit from a small amount of work around the valve seat area but is generally good.
However, the exhaust side is pretty bad and needs a lot of work to try and regain some flow out through these ports. The port is quite narrow in to small openings for the manifold and also not smooth and straight but with 'steps' along the top and bottom of the port. Not good! Luckily there is plenty of meat around the port for modifications to be made to enhance it.
http://www.i-macca.co.uk/stuff/Head%20cut-away%20BMW%20E46%20M3.jpg
And last but not least, this is the inlet side of the BMW E46 M3 head. Bearing in mind, this is designed as a purely normally aspirated head as opposed to the above two that were designed as turbocharged heads.
Nice long and smooth ports flowing directly to the valve seat area, creating a nice gas flow in the top of the combustion chamber, ideal for a nice lean burn. Knife-edging can just be seen where the two ports for the pair of inlet valves seperate down, good for not disrupting flow and causing turbulence as the gases pass the valves.
Another thing to note is the comparitively short valve stem guide. This keeps it out of the way of the gas flow, keeping the gas speed up and minimising turbulence. You can get away with smaller bosses more in a normally aspirated head as the heat build-up is nowhere near as bad. Longer bosses help to dissipate heat better from the valves in to the head and away from the combustion chamber, lowering chances of detonation occuring.