Dual intake runners, better without???

[spetz]

I am playing around with the dual intake runners, and have noticed that there pretty much isn't any difference power wise (from what I can feel) whether it is connected or not.

Now, my question is, would it be better to eliminate the hole system so that those 6 butterflies inside the plenum can be taken out and maybe produce some more top end power?

[Chiangstar]

i dont have any emperical evidence but im pretty sure your low end will suffer if you do that... they wouldnt have put them in there for nothing... the VTEC YO!!!!! systems also have dual intake runners and you dont here about people taking them out...

simon

edit: if you're going to do so, i do believe that your fuel map can be tuned to accomodate the lack of the secondary runners though... a friend of mine did it with his prelude and was making 127kw at the wheels at the time...

[spetz]

Well,
My theory is, that it will be a trade off for less low end, but more top end? I mean, if you had a look inside, those 6 butterflies, 1 per runner MUST be restricting air flow?
So, less torque below 4500 rpm but more there after.

And having driven the car with the motor taken off so they are always set to short runners, I can say there is very little loss of low end power.

At the same time, my theory is with taking this system out, and doing the following:
Shave about 30-50mm off the runners to have even shorter runners (more top end again). Porting them (extrude hone or something) and welding a custom plenum onto the end with an oversize TB.

The benefits that I see here:
Shorter runners = more top end (and the runners look very long)
Extrude honed intake runner without the need to find larger butterflies
Bigger plenum will be cheap to make

Cons are:
Loss of low end power

What are your and other peoples thoughts on this? Can people do a test and actually take this intake runner mechanism off just to test and see how performance goes? It is easy to take on and off

I really think this is a gimmick that gives very small gains which is a good trade off to take it out for more top end power

[mr_bishi]

I've removed the plastic airflow inserts from mine as they look like they restrict flow entering the plenum and it does 'seem' to go better. I've left the butterflies inplace though.

[spetz]

Yeah those plastic things seem so pointless. They are there for only low end power though. I understand the theory behind it, but looking at it looks like it is making more harm then good
Although once it kicks into "short runner" most of the air is gotten from where the butterflies open.

Which is exactly my thoughts that without them it should go better.

[Mitsiman]

We did some testing on a Mivec engine we transplanted into a Mirage vehicle.

WIth a Haltech E11, we picked up 40hp at the wheels between using short and long runners. The short runners provided the majority of the horsepower but lost a lot of low down rpm torque.

The problem to date has been the inability of an aftermarket computer to be able to control the variable inlet manifold unit - even motec can't.

We have now just finishd and are testing our new inlet manifold controller which is a rpm driven switch set which means we can now use this with any aftermarket computer to control the inlet manifold now which is great news for those wanting to do some heavy mods.

But to answer your question - yes there is a definite benefit to running the duel system - but without the factory computer switching it properly, you won't notice the differnce unless you are actually tuning for it.

[spetz]

Mitsiman,

I have taken the switch off so that the car runs permanently on short runners. It has lost a bit of low end power, but if by taking out the butterflies we can gain 10-15hp atw then this loss of low end torque is really worthwhile!
I haven't driven the car with only long runners but I am assuming that would probably be very bad for top end. I am just thinking that with dissing this hole system, we can shorten the runners even more (by say about 4cm) and easily weld a large plenum on it. Without the restriction of the butterflies, and other mods like oversize TB this may produce some very good top end gains for a good price.

I don't see why people are so fussed about low end power. When ever you want to have fun in the car, it'll be high in the rev range, and the 6A12 is so rev happy, just use a lower gear...

[EURO]

I don't see why people are so fussed about low end power. When ever you want to have fun in the car, it'll be high in the rev range, and the 6A12 is so rev happy, just use a lower gear...

take off at traffic lights... lol

[Mitsiman]

The thing to remember and this is what most people forget, is that you need low rpm torque as well in order to get good acceleration. Yes you may have an extra say 15hp at the top end - but if it takes you half the drag strip before you get to that power level, the car that has more low rpm torque is already gone.

ITs like anything - a balance of low and high rpm and setting things up. With massive high rpm vehicles, they run lower gear ratio's to enable them to get to that rpm range very very fast and thus overall go faster.

Personally - I woudl stick with the low / high rpm runner setup, put a nice big twin tb system on there, do some porting work and you have the best of both worlds.

[spetz]

This brings me to another question,
Can you supply gear ratios? The standard FTO ones are way too tall.
And can you supply a hypo intake manifold? Maybe with shortened original runners???

[Mitsiman]

Yes you can play to some degree with gear ratio's in the FTO by using some lancer gears I beleive. But that is as much as I know.

Yes we could make a custom manifold short runner setup no problems. Run a large airbox setup on it with something like a big 80 -90mm single throttle body

[spetz]

What sort of gains would such an intake make?
On a fully rebuilt engine with ported heads, RPW extractors, exhaust, emanage and other little bolt ons?


Is the lancer gear stuff strong enough to put into the gearbox? And is this using the 1.5 or 1.8 gearbox?