Correctable flaw in the 20v intake design?

[Sam_Q]

so basicly I am wasting my time?

[thechuckster]

not really - but there are simpler and probably cheaper ways of achieving noticeable butt-dyno increases (e.g. cams, pistons, etc.)

fwiw: RACE magazine had some interesting articles on porting a while back. They did a comparison test on a head with various techniques.

[Sam_Q]

I dont think there is anything to be gained from a change in pistons other than less load on the bearings. I think shaving the head or a thinner gasket is a better option. However I hear your point, for me its just a matter of wanting to do everything if I can without much cost for the fun of it.

any chance of finding out what issue of race magazine had that article? sounds interesting.

Also I am quite happy to make this part if I even only get a 2% power increase. For me it would be a fun thing to make and it would cost me about $40

[oldcorollas]

if you can do it cheap. then why not. everything is a learning experience

[-GT-]

Sam, it's something that i've heard of on a number of occasions, and seen basically exactly what you're describing as a way of addressing it - basically the throttle/port alignment being corrected by a 'wedge' under the throttles. Only really on full house builds though so it might not become an issue until there's big cams and a lot of porting? ie part of a complete change to the head flow characteristics?

Interestingly though, the 20v port angle is a lot flatter to the cylinder than the 16v - i think it's part of changing the whole inlet tract approach to the chamber? Taking that bend out of it...? Tired rambling now.

Either way, i've got a pic or 2 around somewhere, doesn't show heaps but it gives you an idea of the size and angle used, i'll try and remember to dig it out tomorrow. And if you get around to making one i might even ask if you can knock a 2nd one out...

[Sam_Q]

if you could dig any pictures up at all it would be really appreciated

[RGHilux]

Toyota has many reasons why they do things the way they do. Most commonly, cost, ease of manufacturing, and packaging in certain chassis. I am sure all three are factors in why the intake design is the way it is. You have so many other factors affecting the airflow in the intake port that will cause a change from turbulent flow to laminar flow as well as change the location of the boundary layer, such as the surface finish/bowl area/short turn and long side length differential/seat & valve angles/chamber shape/etc. that you cannot apply so much significance to the manifold until you have the rest of the equation worked out. Best thing to do is finalize the head porting first, THEN work on your manifolding. As to your manifold plate, it is highly possible that it will help flow in certain ranges...the question though is that is it in the areas you need it and does it cover the majority of the valve opening range. Only way you are going to know, is if you put it on a flowbench, and then on a dyno. Can you bolt the plate to the head with countersunk socket head capscrews and then use shorter bolts to attach the manifold to the plate?


I've been a cylinder head porter and engine builder for almost 20 years. If there is any question that you think I might have an answer for you, feel free to ask.

[Sam_Q]

thanks RGHilux,

It is not possible to use countersunk bolts or counterbored hole and then bolt something on top as there simply isnt enough room. It is actually quite a tricky thing for me to make but I have an idea on how to do it. But as with my usual policy I will show pics of what I have done if I do it.

[-GT-]

Ok, dug out a couple of pics, thanks to Gunmetal for forwarding these to me;

[Sam_Q]

thanks for posting the pics. However at this point I dont see the point in continuing seeing that a few people have conveyed this has been tried and did jack shit.

[Sam_Q]

oh also I dont get how they got that to bolt up like that, I mean the top nuts seem to be done up like stock when thats just not possible because the studs would come out at a different angle, excentric studs maybe?

[Sam_Q]

heres where I was up to:



the greater part of the angled peice machined

[-GT-]

Yeah i did some head scratching over those pics last night, but it was late and i was tired so i wasn't suprised at the absence of flashes of brilliance.

I wouldn't be so quick to dismiss this, it's something i'd included in a brief spec of a build if i was to do it. I think there's a pic on bill sherwood's site showing the differences between the 16v and 20v wrt to alignment between inlet port and manifold, and to quote his page;

The alignment between the inlet manifold and inlet port is rather bad and some good improvements can be made there, as can the area just above the inlet valve seats as they have a very nasty machining mark from the factory.

From his page again, 20v cross-sectioned, inlet on the left;



And 16v for comparison;



Of interesting note is the changes in the cross section of the ports of the 20v, versus the relatively consistent 16v ports. Point of this thread though is the angle between the inlet manifold (which obviously isn't shown in that pic), but if you're familiar with the engine you know it sits a lot more horizontal than the angle of the port.

[Sam_Q]

yeah but thats all theoretical. I look at it with my own eyes and think it should make a difference but I have multiple reports now that its been done and didnt do shit.

[oldcorollas]

maybe they did it wrong