Duk, I can't quite follow what combination your engine is (was it the 4agze with supercharger and turbo?) or am I getting confused?
My bad, I haven't communicated properly what I have. It's an AW11 (first) model factory supercharged MR2 (*** import) that I added a turbo to. The original supercharger is still there. The turbo blows through an enlarged throttle body and into the SC (standard pulleys). The SC then feeds a slightly bigger, but still in a poo place air to air intercooler.
As for Richard, I've seen his port stuff, but personally I'd be just as happy to go with Vin Sharp, the last head he did for me was a work of art and worth every cent. In fact it's such a shame I sold the engine, but hey, it financed the twincharge so can't complain.
That's excellent! If a local enthusiastic business owner like Vin is doing work that you believe is up to what you are trying to achieve, then they should be supported. I've bought from Vin in the past and enjoyed a 40+ minute phone call with him about Alfa suspension and (some how
) SPICA fuel injection on the Montreal engines
I know the Camira manifold is not much to look at, but it is doing a remarkable job. I could put a water cooler on the engine, but honestly, there's that much crap in the engine bay and so much elec-trickery on the car that I think I need to keep it simpel, not complicate it further.
My concerns were for the change in internal diameters that I saw in some of the photo's (on the 'other person's' thread). Going from big to small is 1 thing, but going from small to big........
True Duk, I should look at bigger spark plug gaps, Although I am currently running 0.9mm which is not to bad, and I don't seem to have any issues now I have current!!
"I read in a magazine...." Seriously, there was a great article in 'Zoom' some years ago about a built Skyline GTR that was under performing compared to an essentially identical car. Identical except for the HKS capacitive discharge ignition. Boost pressures were similar to yours and the improvements impressive.
As for big port design Duk, from everything I have seen / read it seems to me that port velocity on a turbo engine is not a real big issue. Mind you, I am cautious about big ports purely from the fact that by removing metal you are reducing the stiffness of the head, and that could lead to head gasket issues....maybe. I do recall Jim Steck going for 45mm intake and 41mm exhaust, which would seem like a good place to start...maybe 1 more mm on intake. Vinnie puts 48mm valves on the intake,,mosters! You'd have to be mm perfect, best left him me thinks! I guess you get diminishing returns due to valve shrouding...but it must work, on NA just fine as Vin got serious Hp out of my motor..try 155Hp at the wheels, not bad for 8v NA motor.
Big ports with big valves are 1 thing. Big ports with under sized or impeded flow from shrouding is another. Again I can only offer what I've seen rather than directly measured myself, but the better performing head from the Toyota 4AG(Z)E heads is actually the smaller port version. Even with the 5 valve heads, of the 2 versions, it's the later, smaller port version that works the best. It is a little irrelevant tho, as I am talking about smaller capacity engines with larger valve CSA, but the/my theory is that there is no point in trying to make the port flow any more than the valve can actually let through.
PolyQuad - A new four valve power concept
(website has gone to the sh!t house) talks about a full blown Mitsubishi (16 valve) drag engine (827RWHP) where head porter David Vizard 'felt' that even the small port version was to big.
Sorry to harp on about it, just felt it needed to be mentioned.