Pinky

iTrader: (1)

As mentioned elsewhere, I'm putting an '04 MSM drivetrain into my '99.

I've been trying to come up with the best "mix" of parts to use. The '99 has the VICS system, and in reading up on how it functions I came across a lot of threads about gutting the manifold as well as modifying it into a true dual-runner design by milling the roof of the resonance chamber out to open it to the plenum.

Here's a pic I lifted from another thread, I think it was from Braineac, which explains normal VICS operation-



Ok, so basically, in a NA application the butterflys open above 5200 RPM to help cancel a pressure wave at the intake valve face. I figure on a boosted car, anytime I'm at 5200 RPM I've got 10psi pushing against the valve face; pressure waves are not a concern.

However, there are some advantages to having a manifold that has nice long runners for midrange torque and a big plenum, especially if it magically switched to a huge runner setup under boost. And so that's what I'm going to try out; I'm going to try converting the chamber to a second set of short runners, keeping the butterflys closed at lower rpm/no boost, and open them when it either goes over a certain RPM or boost level. (Megasquirt can do..)

Worse case scenario is I go back to the MSM intake, and I have a mill, so I figured why not.

I wanted to keep as much runner length (when the butterflys are closed) as possible, so I haven't touched the lower half, and have kept the runner sections in the upper intact. Basically just milled out the chamber roof.



Taking out the chamber allowed me to really open up the "floor" of the throttle body inlet, which is actually really sort of tight and oddly shaped. I suspect that the throttle body is the major restriction here, but every little bit helps.



So here's what it looks like milled and blended.



I'll report on dyno results when the car is all together..

Braineack

iTrader: (62)

so you made a long runner / short runner IM?


yeah, you'll have to play on the dyno to see what RPM is a good switching point but could prove to have good results to keep the torque up throughout the entire powerband.

Pinky

iTrader: (1)

Yes, that's the net result (long/short). However, experience has taught me that I am rarely smarter than hundreds of factory engineers, so I'm curious to see if it actually functions as such, or is beneficial in any way. It seems to make sense, from my simpleton "more is better-er" mentality, but the proof is in the dyno pulls.

(Wish I had a baseline turbo/normal VICS run to start with, but it seems like other folks pulls showed minimal difference with VICS on or off under boost, so... I'll just back to back it, on and off, and see what's what.

Braineack

iTrader: (62)

yep. do one on, one off, find the crossover point and run aonther with that point to switch. post results or ban.

thenuge26

iTrader: (2)

If you really want us to love you, do a run with your fancy one when you get it tuned (or you think you do), then pull it off and put the MSM one on for another dyno run.

Braineack

iTrader: (62)

just so the feeble minded can understand what's happening:



I always wanted someone to try this instead of the full porting a lot of people do.

Pinky

iTrader: (1)

Yeah, that really would be the most relevant info to have. How about this; I'll install the MSM intact, get the car dialed in that way, and then try swapping in the Hybrid VICS manifold? That way I'm not potentially fighting a manifold that is an utter failure when initially tuning the car and we can compare manifold to manifold in the most direct way.

Good idea. Thanks.

Pinky

iTrader: (1)

Precisely- nice illustration.

I saw a lot of the full-ported manifolds, and it didn't make sense to me, as it presumes that the combined runners are more restrictive than the throttle body, which I don't think is the case. My hybrid idea goes on the thought that there may be some benefit to changing the length of the runner. In a perfect world it would be more effective at that if opening the short runners closed the long ones, but given the whole "path of least resistance", it hopefully will still have some effect. We'll see..

Braineack

iTrader: (62)

I like short cuts, I think air flow does too.

Dot3

iTrader: (1)

In for results

thirdgen

iTrader: (26)

In case you needed more info, and you missed this thread, here's a link:
https://www.miataturbo.net/engine-pe...-intake-64204/
There's also a few other threads about this topic. I have yet to bolt that plenum on my car and see what happens.

Pinky

iTrader: (1)

I hope so; if not I'll have wasted a few hours of machine shop time, a manifold swap, some dyno pulls and a VICS manifold that in resonance chamber mode is useless on a turbo. (At least thats what I extrapolate from the factory engineers leaving it off the MSM when they reincarnated the 1.8.. Reasonable, yes?)

We'll see. I just scrubbed the engine bay, I'm going to touch up the paint on the subframe and firewall and maybe jam that MSM in tonight. I'll do paying work tomorrow...

Pinky

iTrader: (1)

Ewwww, that's ugly. I read a bunch of threads, but missed that one. I'd like to know more about the comparison runs; is it a real or virtual dyno, did they do much tuning, how many combinations did they try (hi/low open/closed boost/vacuum) but its hard to see any benefit from the runs posted.

Thanks for pointing it out.

y8s

iTrader: (8)

I like this thread more than I like threads about giant gutted VICS plenums.

If I were keeping my car, I might consider doing this.

soviet

iTrader: (10)

I might do this, thanks for the info

Braineack

iTrader: (62)

wait till he posts results. he has to or ban i say!

18psi

iTrader: (76)

Honda has been doing this for years. Integra b18c1 (gsr I believe) and K20a3 to name a couple. They know what they're doing (for the most part lol).

In for (hopefully nice) results

240_to_miata

iTrader: (2)

I have been considering doing this but I want to see some good results first. The "virtual dyno" didn't seem like a thorough test.

Pinky

iTrader: (1)

Oh, hell yeah, I'll try it. I mean, I already made the manifold and all, why not? I am going to take an earlier posters advice and do the MSM drivetrain install with the MSM manifold in place, since it's a proven combination and I want that run to compare, but switching out the manifold isn't that difficult. Never know, maybe it just needed more tuning or something. Like I said before, if those were well-tuned runs in the other thread, then this is a dog idea. No harm in bolting it up though.

Full_Tilt_Boogie

iTrader: (1)

I would argue that they don't know what they're doing.
For some reason people can't wrap their heads around using an auxilary output to activate the secondary runners on the GSR manifold, so instead they gut it and end up losing power basically everywhere.

Little known fact that the GSR head is the best B series Honda head (not the best cams), yet most Honda **** think its a POS because they're too stupid to know how to use the IABs in the manifold, and don't like that the flange is upside down so they can't swap to an ITR or Blox intake manifold.

When you see a diagram, its suddenly so obvious why gutting it is dumb:


EDIT:
Oh wait, you meant Honda has made variable length intake manifolds, not honda **** have gutted Honda made variable length intake manifolds.
I have the dumb today.