Upper VICS Mod for turbo cars.
#1
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Upper VICS Mod for turbo cars.
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..
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..
Last edited by Pinky; 02-04-2013 at 09:23 AM. Reason: Clarity
#2
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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.
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.
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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.
(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.
Last edited by Pinky; 02-04-2013 at 09:38 AM. Reason: Clarity
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Good idea. Thanks.
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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..
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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.
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.
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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...
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...
#13
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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.
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.
Thanks for pointing it out.
#19
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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.
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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.
Last edited by Full_Tilt_Boogie; 02-04-2013 at 11:38 PM.