Polyquad head - Staggered valve sizing to initiate swirl

[andrew_mx83]

i found some of the info in this link http://www.gofastnews.com/showthread...-power-concept posted in another thread very interesting and am toying with the idea for my 7m race motor, as opposed to the usual 1mm OS all round (32/34 inlet & 27.5/28.5 exhaust)

Thoughts?

[twiztd]

first thought is i think your link is broken...

[Duk]

1 thing I noticed with my SC AW11 MR2 is how much more torquier (OK, every thing's relative here ) it is at low revs than my RB20det S13 Silvia.
Now before people start going on about positive displacement superchargers and comparable weights, this observation is made before the SC is switched on and the difference in weight isn't as great as most people think. Certainly comparable to the differences in engine capacity.
Why this difference? I can't say for sure, but the big port 4AG(Z)E head does have a port bias about it where #1 cylinder port points more toward the front of the engine. I see this as making the inlet valve closest to the front of the engine more likely to flow slightly better than the the other valve and so, possibly, creating a degree of swirl in the cylinder during filling.

The only real way would be a direct comparison of 1 engine tested and tuned (fuel and ignition) with both a conventional port design and a Polyquad design. Use the same cams, inlet manifold and extractors/exhaust to remove variables.

[Duk]

first thought is i think your link is broken...

Things have changed by the looks of it:
http://www.gofastnews.com/showthread...-power-concept

[andrew_mx83]

thanks duk thats the link


there is another whole article from the same bloke on port shape/size but id like to keep this thread about the staggered valve sizing... i am putting a SHITLOAD of design & engineering time into this motor so am happy to go down this route, but only if there are benefits to be had

BUT i would hate to spend over 12 months and around 10 grand building the motor to find that i would have been better off sticking with the usual 33/28.5 combo. to go the polyquad route involes changing valve seats etc so would be very pissed off if i went to a lot of cost & effort for no real gain.


some rough numbers on total valve area:

[oldeskewltoy]

If the purpose is to initiate swirl... why bother with it on the exhaust side... after all the dynamics of the exhaust are far different then the intake.

[Duk]

If the purpose is to initiate swirl... why bother with it on the exhaust side... after all the dynamics of the exhaust are far different then the intake.

Maybe it's effective during the overlap period???

[Duk]

thanks duk thats the link


there is another whole article from the same bloke on port shape/size but id like to keep this thread about the staggered valve sizing... i am putting a SHITLOAD of design & engineering time into this motor so am happy to go down this route, but only if there are benefits to be had

BUT i would hate to spend over 12 months and around 10 grand building the motor to find that i would have been better off sticking with the usual 33/28.5 combo. to go the polyquad route involes changing valve seats etc so would be very pissed off if i went to a lot of cost & effort for no real gain.

The thing with doing things differently is that you aren't guaranteed anything except education and experience. I doubt there'd be many(any?) people in the world that would have applied such an approach to the 7M, so I think you will be even harder pressed to get conformation about end results.
Ultimately you will have to get your hands dirty and find out for yourself.
Beside, if you were after the same results as everybody else, you'd just be following what everybody else does, and that is perpetually boring.

[TERRA Operative]

If the purpose is to initiate swirl... why bother with it on the exhaust side... after all the dynamics of the exhaust are far different then the intake.

The smaller exhaust valve near the larger intake valve helps prevent the intake charge 'cross-flowing' out the exhaust during overlap, according to the article. (read the 'cross flow suppression' paragraph).

[oldeskewltoy]

The smaller exhaust valve near the larger intake valve helps prevent the intake charge 'cross-flowing' out the exhaust during overlap, according to the article. (read the 'cross flow suppression' paragraph).

but it also requires the exhaust valve to be placed deeper in the head... or did I mis read that......???????????

[oldcorollas]

so which is more effective in a 4 valve head? swirl or tumble? and does it make any difference?

isn't valve circumference more important than valve area?

[andrew_mx83]

The thing with doing things differently is that you aren't guaranteed anything except education and experience. I doubt there'd be many(any?) people in the world that would have applied such an approach to the 7M, so I think you will be even harder pressed to get conformation about end results.
Ultimately you will have to get your hands dirty and find out for yourself.
Beside, if you were after the same results as everybody else, you'd just be following what everybody else does, and that is perpetually boring.

already going for an 80thou overbore

TBH, most of what im doing is pretty far from the "normal" with 7m's that there is not really any experience/education anyway but maybe im playing with enough unknowns already and this is just something else that could let the whole thing down. (using 5m crank, reground cams, 12:1, carbies etc and shooting for a redline of 9000)


and yes, the plan if i go down the polyquad route will be to recess the exhaust valves 60thou back into the head.... this is conveniently the same amount as my base circle reduction on the cams so will make sourcing valves easier as well as reducing cross flow


OC.... from what i read, 2 valve heads have swirl, 4 valves have tumble.... the polyquad system gives a combination of the 2 which he calls "twirl" kinda like a tornado i guess. i can see it being good, you would get a very even burn throughout the whole cylinder that way.
not sure if its valve area or circumference..... i was always told the important bit is the "curtain area" at max lift.... which i guess would be (circumference x lift)?

[andrew_mx83]

valve circumference (total):
stock = 374
1mm o/s = 386
polyquad = 383


curtain area (total):
stock = 2802 (7.5mm lift)
1mm o/s = 3283 (8.5mm lift)
polyquad = 3256 (8.5mm lift)


so the polyquad consistently comes up a bee's dick smaller than 1mm o/s