I did this to mine, who wants to buy it?

 

I have an extra '99 mani already, but if this works it'll be on my to try list. Keeping the butterflies seems the most sound idea. Be interesting to see where the switch open is best

 

quite possibly going to end up being around 5250 still maybe closer to 6K where the torque starts dropping off again.

 

In for results. Go Pinky!

 

In for results. I did something similar to this on my Starlet and it worked a treat.

 

In for results! If this works well I'll be copying you. If only you could mod the other runners with butterflies too to make sure it goes the way you want it to.

 

I also did this. The short runners lift the power line up starting from about 6.5k. In other words you gotta make them an inch longer to lower the benefit down to about 5.5k. If you're revving up to 9k then this mod is great however for our stock redline its a bad mod because it ends up being useless and you get rid of the VICs. You end up with a rather nasty dip from 5k to about 6.5k

After experimenting with this what i think is a good idea is to cut the top of the runners here. Will post pic in a sec.

Here you go, cut the red part so you shorten the intake and lift up the power band. Dont touch the green part though since you want to keep the VICs in tact unless you plan on increasing the redline another 2k.

I gotta lower my boost to the stock level so i can do few tests (clutch slipping at current level)

 

needs more dyno proof.

 

Honestly no clue where to do a virtual dyno run any more. The only place here is getting too crowded while the shop next door (sound performance) wants 200 bucks per hour. Not something i can afford at the moment.

I did do 2 virtual dyno runs when i first gutted the manifold. I did 2 runs one with closed one with opened. The closed run maxed out at about 5k rpm then started going down till redline, the open run was horrible until about 6.5k rpm then spiked and hit the redline at 7k.

I did post the virtual dyno results here on the forum on one of the gutted manifold threads back when i gutted it.

 

I can't see why the fundamental characteristics of airflow in the manifold would be significantly different whether the absolute pressure inside the manifold is 100 kPa or 200 kPa. One could argue that the density of the air will be slightly higher, but in either case the way in which the air behaves as it moves through the system should be essentially the same.

 

Exactly. Thats why you want to keep the vics.

 

what if you replace the top/bottom half gasket with a half inch or thicker spacer?

 

That wont work since the runners end on the bottom manifold. Adding a spacer on a gutted manifold will be more like a bigger plenum. I dont know what it would do if you keep the vics in tact and make the space bigger though.

 

So Pinky...

Results?

 

What about spacing the entire manifold an inch away from the head (or half or something) to bring the rpm band of the whole thing down with this mod combo?

 

That would work better. That or welding "runners" to the upper side where the plenum is.

 

umm...:

MX-5 Miata Forum - View Single Post - Turbo + VVT + VICS

 

I believe that diagram is actually wrong.

AFAICT VICS doesn't change runner length, it couples in a set of stubs to change the resonant frequency of the intake runners.

 

Yup, the speed of sound doesn't change with absolute pressure (it changes with temperature).
Speed of sound temperature air formula without no barometric pressure calculator table air density of air calculation mach 1 acoustic impedance propagation air density sea level velocity ideal gas 20 degrees or 21 degrees Celsius C cold warm - sengpi
This is supported by observations that the VICS effect in % terms is the same for NA cars and the above 6 psi car.

 

The diagram is modified just to show the picture... Heres the original.