port size/shape/angle how affects flow.

[jonathan yee]

here's the dilemma. building a 3sgte and don't know which head to use. previously only had the gen2 NA head to play with (don't want the gen2 TVIS head) and so started making an inlet manifold for it. but know i got my hands on a gen3 head for cheap.

plans for the build was i wanted it to rev hard 8-9000rpm making decent power/torque up in the top end. also i wanted it usable for daily driving and track/motokhana(it's going in an sw20 btw) hence the turbo recommended for good flow in top rpm was a gt35r with 1.06 rear. obviously this sucks for any power before 5krpm, so the plan is to go sequentials with a gt2560 for initial low end boost.

here's pics of the inlet mani so far. short runners for top end, hopefully the little gt2560 will give me enough and overcome the horrible torque hole the short runners give.

gen2 ports


this is the same plate against the gen3 head, the gen3 ports are marginally shallower in height but wider.


this is the gen3 inlet gasket on the gen2 inlet plate(the gen3 ports are a little smaller than the gasket.
and here's the gen2 head on top of the gen2 head


comparison specs:
gen2 ports size 48x35
gen2 "ported" size 51x36(this is the size of the inlat manifold plate i got made.
gen3 ports 56x33.

the gen2 ports are "higher" in the head meaning the ports are angle more straight down into the valve inlets approx 15deg from horizontal.

then gen3 has a shallower angle so the ports aim more at the valve stems approx 8deg from horizontal.

so the Q;s are, how much does the angle of the ports affect flow into the bore.

how much does the port shape affect airflow, the gen3 being more flat and oval with a funny kidney shape, gen2 more rounded.

the gen3 ports are bigger would this be better for top end or would this not matter so much with the short runners and a big gt35r forcing crap loads down its guts?

[toyboyracer]

http://www.circletrack.com/techartic...ech/index.html

http://www.popularhotrodding.com/eng...ads/index.html

[thechuckster]

http://www.performanceforums.com/for...php?t=67247264

gen3 head, serious porting, 1mm o/s valves, significant flow increase after two goes at the intake ports:
Lift - stock (cfm) - ported (cfm) - revised (cfm)
.1 - 92 - 94.5 - 94
.2 - 166.5 - 176.5 - 177.1
.3 - 219 - 235.2 - 242.2
.4 - 255.8 - 269.9 - 278.3
.5 - 264.6 - 288.1 - 298.2
.6 - 265.2 - 296.3 - 308.7

[jonathan yee]

thanks for the link's and reply's. i've no doubt that a good port job by someone that knows what they're doin would yield excellent results.

my question is which head do you think would be the best base to start from? ie: which head given the different port angle, size and shape would i best spend the odd 1k on for quality port work?

i'll reshoot the middel 2 photo's they cam out crap and you can't see jack

[toyboyracer]

I'm leaning to the bottom head as an unedjimcated guess it will cause better disturbance of the fuel vapor thus helping in atomization etc

Only a guess - So no flaming (lol) guys !

[midnight_purple_GA70]

im just wondering how you intend on fitting a compound turbo setup in an mr2?

i thought they were a tight squeeze with the standard motor and turbo?

or am i wrong?

[jonathan yee]

I'm leaning to the bottom head as an unedjimcated guess it will cause better disturbance of the fuel vapor thus helping in atomization etc

Only a guess - So no flaming (lol) guys !

you say this based on what?

im just wondering how you intend on fitting a compound turbo setup in an mr2?

i thought they were a tight squeeze with the standard motor and turbo?

or am i wrong?

well tristan can fit a camry V6 with sequentials, the big one bieng a gt40 so he'd be able to fit twin's with the 3sgte..... turbo's hang's over the gearbox.

[toyboyracer]

71-87 2-T / 3-T inlet ports are circular and then as time went by ports went more oval.

Guessing there was a reason behind it, so my best guess would be to go the bottom one.

Funnily enough Holden heads from Dinosaur days were oval - Go figure !

[jonathan yee]

well both heads are oval, just one more so, but according to this the gen2 head has a more down draft port and hence better...????

http://www.guy-croft.com/viewtopic.php?f=2&t=199

and here's the BEAMS head, wish it was mine.

[toyboyracer]

Beams me up Scotty, this planet's FAST !

Ok, I give in...

If good enough for Beams, it would then be the obvious choice

[Sam_Q]

the taller the port the higher the potential velosity before choke, this means that for the same given cross section the more upright port will flow considerably more air. So in a direct comparasin for two engines who both have the ports just big enough to not starve the top end; the upright port engine at low to mid revs would still have a high velosity due to the smaller cross section. This is before you even count the reduction in eddies + turbulence and the change to a more ideal venturi port shape.

Upright = win

[jonathan yee]

need to get some measurements of the beams ports etc.

so does the upright port design better across the whole rev range? i understand that some people put 1jz heads on 2j's for better port velocity due to smaller ports but i'd assume that only works up to a certain point in the rev range then you'd need bigger ports for outright flow in the top rpm.....

i have 3 of the gen2 heads at home, so i might do a home port job on one and whack it on the flow bench......

[Sam_Q]

in theory if optimised then yes it should be better everywhere. People put 2JZ bottom ends under 1JZ heads for a cheap capacitiy increase, then some people misread it who thought oh the japs know better and did it on purpose.

[MS-75]

You want to use the head with the bigger downward angle on the ports as the starting point.

It may not flow as well in stock trim (just a wild guess here though), but once you begin porting the head, it will blow the shallower port angled head out of the water.

On my 1FZ head, the inlet ports are at approx 30 degrees down angle, and the exhausts are flat like a 2J

My head porter went to town on both the intake and exhaust ports - we also have oversized valves in it.

The exhaust port has a larger x-sect and larger valves than a 2J, and when the all-out 1FZ ex port was compared to an all-out 2JZ ex port, it flowed a predictable 13% more than the 2J. (remember both ports are flat)

On the intake side, the differences between the x sect and valve sizes of the two worked heads (1FZ and 2J) was the same in ratio as in the exhaust ports, HOWEVER the 1FZ has canted inlet ports and the 2J has flat inlet ports. The difference in flow between the 2 ports was almost 35%........

Obviously that shows the huge difference canted ports make - and the more the better (up to a point obviously - but you are nowhere near the limt)