4AGE small port --> making the ports smaller again

[YelloRolla]

You can easily do 2 banks with different strokes on an 8 with a little creative journal machining. Remember how much $$ they threw at this.
I dont see where it states that it's a pair of v4's. And I'd say that'd be against the rules. Also at one point he clearly states "Nasty numbers for a Detroit relic!"

Think about how the best way is to machine a common crank with different strokes. One stroke on 2 journals and another stroke on the other 2. It would be easier to balance as well as making the manifold layout symmetrical - remember he does state that they had different lengths and volumes for the manifold runners.
I imagine that the cylinders 1 and 2 as well as 7 and 8 would be one stroke and cylinders 3,4,5 and 6 would be the other configuration.

edit/ BTW two vee fours is a creative way of describing it - not two engines joined. Even TOO referred to "each cylinder" as an "individual engine"

[myne]

Well, I admit that'd be the easiest way, but neither of us can be sure if that's what actually happened.
Regardless of that, I'm not advocating different bore/stroke in an inline4 so it doesnt really matter. What got my attention was the different inlets and cam profiles - something that COULD be attempted on a bigport modified to be an 8-port.

Imagine 4 smallish ports optimised to say 3500-7500 rpm and 4 smallish ports with a different shape optimised for 6000-9500rpm. Chuck in custom cams that suit the different ports and slightly different length inlet runners and you *might* end up with an engine that has a fat torque curve from 4500-8700.

That was my point. Though my numbers are pulled out of my ass, it looks more appealing to me than simply going for a smallport that can only be optimised for 1 rev range.

[tricky]

I wonder what'd happen if someone turned the bigport into a distinct 8 port?
There's obviously enough room to spare for a divider, allowing seperate management per port.
I theorise that you could adapt each port, possibly with it's own cam grind for different ranges allowing for a broader power band.

This is something that I've seriously thought about too. It really makes a great deal of sense to manage the runners by individual valves rather than as a single port feeding two valves.

Advantages would include a nice, direct, high velocity path to each valve, and there would be no reason to keep the valve ports identical, so you could do some independent trickery.

The sticking point for this would be creating a divider of the correct shape for nice flow characteristics. The best way would probably be to hog the port out, fill it back up quite a way and port it on a bench to achieve the best results.

[mic*]

Myne, that seems like a good idea, the cam profiles would be interesting.

Im thinkin you would need a VVT style cam that could;

run a shorter duration on the large port relative to the small port at 3500-7500rpms (your "smaller port" target range) to optimise cylinder intake velocity by forcing flow through this port and valve.

then engage a longer bigger lobe for the "bigger port" target range up higher.


On the actual topic of the thread, if you want to make your ports smaller, i support the shape descibed by Dimitri. It reduces cross-sectional area, which increases velocity, yet the flow characteristics "can" remain unchanged because the shape is more efficient for flow around a bend/curve.

In a very simple sense its like a banked corner for air.

The distance which each molecule of gas in the air has to travel around the bend or curve is closer to even so flow is smoother. This equals better flow for given X-sectional area (which has been reduced already for better intake velocity).

[ira11y]

Do you care explain how a big port (all else being equal), will benefit a turbo application?

Jase im hardly going to try and compete with you in knowledge on turbo applications given your form, and my well known aversion to being blown

the basic reasoning as i have understood it, which given the delevlopment of modern engines over the last couple of years may have changed due to technological advance and greater understanding of flow characteristics in those engines, is that with a correctly matched turbo the larger port port head is able to develop more power overall due to the basic principal of capacity.

i am not saying in anyway that this means better or more useable power... just more overall.

Something that i have never seen (not to say that it hasnt been done) but would be really interesting to figure out is to take a generic turbo and run it on both 20V heads and the big and small port respectively at a fixed boost of say 5psi, measure the volume capacity of each head from the entrance of the port and also entrance area of the valves as a total.

then take the figures and using the volumes of each work out which has a better characteristic for the turbo application.

As has been pointed out over the years there are lots of changes that could improve any standard engine to suit any one particular application.

[Hokey]

Just trying to get my head around this. so the whole point of making the ports smaller is to get less fuel going back into the port when the piston comes up on the compression stroke? couldn't this be fixed with less duration. or better cam timing?
that site was a very interesting read

[roadsailing]

in a way...

the idea of making the ports smaller is to make the air move faster, thus increasing its inertia. this inertia helps pull more air/fuel into the cylinder, to the point where it will keep going in when the piston is moving up.

make sense? i tink that wasn't the best explaination.

[oldcorollas]

tis a few things...

higher airspeed past valve, reduction in reversion when exhaust pulse comes back too early..

but really, it is a not particularly well understood art. some of the manufacturers have good simulation software, but it is just not that easy to simulate the complex fluid dynamics of a piston engine....

otherwise ports would all be the same design

[Nim]

Myne, that seems like a good idea, the cam profiles would be interesting.

Im thinkin you would need a VVT style cam that could;

run a shorter duration on the large port relative to the small port at 3500-7500rpms (your "smaller port" target range) to optimise cylinder intake velocity by forcing flow through this port and valve.

then engage a longer bigger lobe for the "bigger port" target range up higher.

mic*, just so I'm clear, are you talking about changing the timing of your cam? That's what VVT is. Or are you talking about adjusting the lift and duration, which doesn't really have an acronym (Unless you count VTEC YO!).

I dunno how you’d do VVT on an inline block with different grinds, but some kind of variable lift and duration would be do-able. Where would you get the Variable Lift and Duration set-up from though? You’d need a whole new head. Then you’re not talking about a 4A-GE head anymore, and possibly engine. You'd need a 2ZZ-GE, B18C or B16A.

[myne]

I'll explain my idea a little better...

| Uu Uu uU uU |
| Oo Oo oO oO |

If that was the head of the engine viewed from the inlet side, the O & o represent the customised ports, each more optimised to a different RPM. The U & u represent the "large" and "small" cam lobes. The cam is fixed, but the valves run different profiles eg u could mean 260* and U could mean 304*. Obviously individually they will still flow _OK_ outside of their optimum ranges, but together they should combine to extend the usable range of power. To keep some idle characteristics with mad cams, use TVIS to block the "larger", more top end focussed ports. That will effectively make it an 8valve on idle.

So it goes
Idle - 4000rpm : "TVIS blocks "high" cam lobe (8valve)
4000-7000rpm : "low" cam lobe comes into its range, TVIS is open (16valve)
7000-redline : "High" cam lobe comes into its range, TVIS is open (16valve)

The point of it is to exploit TVIS for half decent low end with cams that are "too big" and THEN allow the different flow characteristics of the 2 completely different grinds to extend the power band beyond what either could do by itself.

You'll never quite reach the power a plain 304* cam will provide, but you also wont run out of breath where the 260* cam would.
You wont have to wait as long for the power to start, it will last longer but it wont peak quite as high. The result should be more drivable.

It's my idea of a "vtec" compromise with the parts at our disposal.

Dimitri, I dont suppose you could run this idea past your friend?
Since he has the bench and the plasticine and all

[oldcorollas]

[QUOTE=Nim]mic*, just so I'm clear, are you talking about changing the timing of your cam? That's what VVT is. Or are you talking about adjusting the lift and duration, which doesn't really have an acronym (Unless you count VTEC YO!).

I dunno how you’d do VVT on an inline block with different grinds, but some kind of variable lift and duration would be do-able. QUOTE]
lets see now......

how about.... toyota VVTl-i???

varies lift and duration.. and the timing...

http://www.corollaperformance.com/TechInfo/VVTLi.html

vtec yo... fuckoff.... honduh forum? no.. toyota form? yes... relevance of vtecyo to toyota when it has superior VVTL-i? priceless

as for continuously variable lift.. BMW throttleless system..


myne, afaik, there IS a bike engine that did just that (as far as uneven grinds go) but i cbf looking for it now..
but sure, in theory it sounds ok... but you may be limiting things a bit because of the available valve head area. it's all well and good to have high port velocity, but if it botles up at the valve.....
then again, perhaps, since actual flow is limited, then it might work very well

all you need to do to try it properly is to port divide a TVIS head with stock cam.
if, with one full port/valve blocked off you get more torque than with TVIS and 2 valves open, then sweet!, but if you still get less torque than with 2 valve heads open, even tho the port is half blocked. then it's not much help...

all you would need to do is to tig some sheet onto a TVIS manifold and then carefully insert (although of port is blocked but valve open, it'll create some serious vacuum and probably suck the divider )

less talk, more action

edit: or just get old set of cams, grind off one lobe and stick 'er in.. dyno back to back with stock cams and no divide and go from there

[Darren]

Darren, you're telling us that the engine made more mid range and top end? I think that you told me this story in person once before. Just the way it is written "reduced the power loss" which I am sure that is a gain, and that is what you meant. Fuck it, I am work too, I just want it ot be clear to others reading your results.

Jase

Sorry about that Jase. The original power curve looked like a lightning symbol, meaning it levelled off and even dropped slightly right in the mid range then went vertical again. After the trumpet mod the curve only levelled off about half as much as before. It's really tuff to describe in words....

I wonder what'd happen if someone turned the bigport into a distinct 8 port?
There's obviously enough room to spare for a divider, allowing seperate management per port.
I theorise that you could adapt each port, possibly with it's own cam grind for different ranges allowing for a broader power band.

Love the way you're thinking. I have a spare head at home (i think it's a ported tvis one) and a tig, i'm prepared to donate the head and have a go at the mods if someone else will come up with a modified cam and a test vehicle. I could probably wangle a couple of free dyno runs too.

My only concern is the injectors, aren't they in the head right where the divider would need to be?

Darren.

[Nim]

lets see now......

how about.... toyota VVTl-i???

varies lift and duration.. and the timing...

http://www.corollaperformance.com/TechInfo/VVTLi.html

vtec yo... fuckoff.... honduh forum? no.. toyota form? yes... relevance of vtecyo to toyota when it has superior VVTL-i? priceless

Here we go again. Try actualy reading my post, rather than just being insulting.

Note I mentioned the 2ZZ engine, with the VVTL-i. VVT is generaly accepted to stand for Variable Valve Timing. Toyota adds the L to denote variable Lift aswell. This is 'cuz it incorporates VVT (which I described in my post) and variable lift (L). I don't beleive Toyota actualy had a head that just has variable lift, and as such, it doesn't have a stand alone acronym. Honda does and they call it VTEC, hence my comment, which was supposed to be a joke (VTEC yo? I mean honestly). Anyway, once again you've gone off topic to insult me and explore your ilogical hatred of anything non Toyota. How very mature of you.

myne, it's an interesting idea. You could involve TVIS to help stop the engine being a pig down low. My comment on using a Honda B engine or 2ZZ-GE was directed at *mic, who seemed to be suggesting using variable lift, rather than a butterfly in the intake runner.

[myne]

My only concern is the injectors, aren't they in the head right where the divider would need to be?

Yeah :/
The manifold would have to feature a revised position. I guess ideally you'd put 2 smaller injectors facing directly at the valve, but the standard one, off to the "small" side should do it well enough I guess...
You'd think though, the 4age has been around for 20 years now, surely everything that can be done has been done?

[Nim]

Yeah :/
The manifold would have to feature a revised position. I guess ideally you'd put 2 smaller injectors facing directly at the valve, but the standard one, off to the "small" side should do it well enough I guess...
You'd think though, the 4age has been around for 20 years now, surely everything that can be done has been done?

Not necessarily. People are allways inventing more and more crazy things to do to engines. Especialy as the 4A-GE gets cheaper and cheaper, so it becomes more economical to make these crazy modifications to.

Also, why go for 2 smaller injectors? Go for 2 standard sized injectors! Double your possible fuel flow.