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Old 01-12-2009, 05:51 PM   #1
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Default VICS Manifold

I've seen the threads with people gutting the manifold lately, but I'm not so much interested in doing that. Going to retain the VICS system.

Long story short, the '99 head I have is going to the machine shop this week, they're not doing anything crazy with it, just removal of casting blemishes, and with the combined information from Pat (thanks again!) and input from the machinist doing the work, he's going to get it to breathe better, but just not going all out with it per se. I was going to wait for one of the aftermarket intake manifolds that are coming to the market, but don't feel like waiting anymore, and I'm getting tired of adding more money/aspects to the build. Really need to focus on paying off debt and finishing school.

Anyway, is there anything I should get done to the manifold as well or is it just as well left alone? Has anyone done anything to one? It was suggested to port match the runners where they meet the head, good idea? What else? TIA
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Old 01-12-2009, 06:02 PM   #2
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Old 01-12-2009, 06:11 PM   #3
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I've seen the threads with people gutting the manifold lately, but I'm not so much interested in doing that. Going to retain the VICS system.
I saw your thread. I don't want to gut it.
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Old 01-12-2009, 06:23 PM   #4
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If you don't want to gut it, then leave it alone. Gutting it helped some, but it's not a "fix". Travis needs to get a 99' intake manifold finished that cost less than my car.
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Old 01-12-2009, 06:30 PM   #5
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You wouldn't really want to cut the intake manifold at all. (Hate to rain on your parade pat.) Increasing runner cross section can help add a couple horsepower on top at a massive expense on bottom depending on what you've done.

Things not to do:

Do not port match to the head. The stock runners should be slightly smaller then the port, this aids in keeping reversion out of the runner, and your not going to increase flow, just volume which means less velocity and less torque.

Do not widen any part of the port unless your doing the whole port (extrude hone) but expect to loose some amount of bottom end when doing a process like this.

What you could do:

Remove casting marks in the manifold (whatever you can get to) Removing marks from just one part of the runner really isn't going to help, so if you can't access the whole runner just leave it alone.)

Port match intake manifold to throttle body, but not throttle body to intake manifold. (Do not modify the throttle body to the plenum hole is what I'm trying to say, but if the plenum is in the way of the throttle area when your looking through it remove as necessary.)

Depending on boost amount you could remove some of the throttle shaft of the throttle body this is known as "stabbing" the shaft. Just be careful. Too much removed could mean a throttle plate in your intake manifold, and a fun time slowing down a motor at uncontrolled wide open throttle. (ignition key or I guess if you had good brakes and caught it at low rpm you could choke it death.)

All together you could probably spend 4 or 5 hours on the intake manifold meticulously detailing it, but the performance increase you would expect would be maybe a percent or two.

Thats my take on it anyway. Maybe someone else has some better ideas.
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Old 01-12-2009, 06:42 PM   #6
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Originally Posted by TravisR View Post
You wouldn't really want to cut the intake manifold at all. (Hate to rain on your parade pat.) Increasing runner cross section can help add a couple horsepower on top at a massive expense on bottom depending on what you've done.

Things not to do:

Do not port match to the head. The stock runners should be slightly smaller then the port, this aids in keeping reversion out of the runner, and your not going to increase flow, just volume which means less velocity and less torque.

Do not widen any part of the port unless your doing the whole port (extrude hone) but expect to loose some amount of bottom end when doing a process like this.

What you could do:

Remove casting marks in the manifold (whatever you can get to) Removing marks from just one part of the runner really isn't going to help, so if you can't access the whole runner just leave it alone.)

Port match intake manifold to throttle body, but not throttle body to intake manifold. (Do not modify the throttle body to the plenum hole is what I'm trying to say, but if the plenum is in the way of the throttle area when your looking through it remove as necessary.)

Depending on boost amount you could remove some of the throttle shaft of the throttle body this is known as "stabbing" the shaft. Just be careful. Too much removed could mean a throttle plate in your intake manifold, and a fun time slowing down a motor at uncontrolled wide open throttle. (ignition key or I guess if you had good brakes and caught it at low rpm you could choke it death.)

All together you could probably spend 4 or 5 hours on the intake manifold meticulously detailing it, but the performance increase you would expect would be maybe a percent or two.

Thats my take on it anyway. Maybe someone else has some better ideas.
The stock plenum on the manifold is just too small. Doing what I did eliminated the VICS chamber and made for a larger effective plenum. It made a decent difference in power. Before the motor stopped making power at 6K. Now it stops making power after 6500. I'm sure I saw a 5-8% increase in power from 6K+. Now what it did for low RPM power, I can't really say. Car is stronger down low more than ever, but I also turbo'd it. So while you may have your reasons as to why NOT to do what I did, I can tell you it helped.

That said, if you read my thread I linked, you'll see I'm not thrilled with the results and am planing to build a new one w/ a larger plenum or buy a better one if somebody builds a decent one that's affordable.
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Old 01-13-2009, 05:56 PM   #7
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I don't think Paul's/Artie's gutted VICS manifold had any negative effect on his torque curve.
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Old 01-13-2009, 09:09 PM   #8
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Didnt the dynos they posted show that the tq curve was almost identical and then pulled all the way to red line instead of dying with the gutted manifold??
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Old 01-13-2009, 10:12 PM   #9
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Well it would depend on a variety of factors. With very targeted intake tuning you can create a positive tuning pressure of between 2 and 6 P.S.I. ( With the miata and stock cams probably a whole lot more the 2 PSI then the 6.) There is a certain rpm level that you simply can't have worse tuning, their is already reversion at low R.P.M. so torque is already bad. As your bring the engine online, if your turbo is in the process of spooling up you won't notice a power difference at all in the mid range. This is because there is more restriction in the intake (due to bad tuning) and the the turbo compensates the bad tuning with more pressure(because its moving air not pressure). So torque is eqaul during spoolup(about.) If you have a small turbocharger and you can pretty precisely control boost (within .5 P.S.I.) you will see a decrease in torque. Its pretty much a given, otherwise everyone would run around with 1 inch runners and sewer pipes on their cylinder heads. Even in turbo race engines cross sections and runner length are controlled and made as small as possible.

Odder things have happened that torque goes up as runners get bigger and bigger all over, but theoretically, thats pretty freakin unlikely. Velocity is good, and too little means the air never gets flowing to fill the cylinder even with the help of pressure (its a balance between velocity and density that gets you the best power.)

In a intake port you could visaulize it like moving a heavy trailer over a 50 foot distance within a certain amount of time. However much weight you get over the line is how you a scored(amount over time so (velocity*cross section*density)/time). If you can wind your car up fast and move the whole thing over the line before the time is over it might be better then trying to move a really heavy trailer over the line half way. Optimal tuning happens when you just pull the trailer in when the timer goes off.

That is to say in real life, optimal tuning happens when the air gets flowing fast early, and the cylinder is on the very verge of reversion into the intake port when the time is over.

I give anyone the props in real world data, but just hacking up the intake manifold and increasing the mass of the air the port has to pull when it opens has to have a negative effect on torque somewhere.
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Old 01-13-2009, 10:28 PM   #10
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Quote:
Originally Posted by TravisR View Post
Well it would depend on a variety of factors. With very targeted intake tuning you can create a positive tuning pressure of between 2 and 6 P.S.I. ( With the miata and stock cams probably a whole lot more the 2 PSI then the 6.) There is a certain rpm level that you simply can't have worse tuning, their is already reversion at low R.P.M. so torque is already bad. As your bring the engine online, if your turbo is in the process of spooling up you won't notice a power difference at all in the mid range. This is because there is more restriction in the intake (due to bad tuning) and the the turbo compensates the bad tuning with more pressure(because its moving air not pressure). So torque is eqaul during spoolup(about.) If you have a small turbocharger and you can pretty precisely control boost (within .5 P.S.I.) you will see a decrease in torque. Its pretty much a given, otherwise everyone would run around with 1 inch runners and sewer pipes on their cylinder heads. Even in turbo race engines cross sections and runner length are controlled and made as small as possible.

Odder things have happened that torque goes up as runners get bigger and bigger all over, but theoretically, thats pretty freakin unlikely. Velocity is good, and too little means the air never gets flowing to fill the cylinder even with the help of pressure (its a balance between velocity and density that gets you the best power.)

In a intake port you could visaulize it like moving a heavy trailer over a 50 foot distance within a certain amount of time. However much weight you get over the line is how you a scored(amount over time so (velocity*cross section*density)/time). If you can wind your car up fast and move the whole thing over the line before the time is over it might be better then trying to move a really heavy trailer over the line half way. Optimal tuning happens when you just pull the trailer in when the timer goes off.

That is to say in real life, optimal tuning happens when the air gets flowing fast early, and the cylinder is on the very verge of reversion into the intake port when the time is over.

I give anyone the props in real world data, but just hacking up the intake manifold and increasing the mass of the air the port has to pull when it opens has to have a negative effect on torque somewhere.
Here's a datalog of my car running naturally aspirated on the stock 99' intake manifold. New air filter in the stock intake system. I one day removed the intake completely just to make sure it wasn't the restriction and it was not. Anyways, look what happens to pressure in the manifold at WOT. The MS reads vacuum and it was hooked to a port at the rear of the manifold. Same port everyone else uses. FWIW, I did a lot of headwork and that may contribute to this.

MAP is the teal colored line at the top, and RPM is yellow. This is a pull in second and third to 7834.

Name:  datalogpic23-26-08-1.jpg
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That's why I say the stock intake manifold SUCKS.
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Old 01-13-2009, 10:38 PM   #11
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I wish that had a scale on it. I like these charts the MS pumps out, seeing the real data is great. What you really need is a more normalized chart... You have an excel sheet of that? I could normalize it and really look at the numbers. Graphs are pretty, but don't really tell me crap about whats going on. Those little spikes every 400 rpm or so are either electronic jitter, or some really funky harmonics in the intake manifold (not likely).
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Old 01-13-2009, 10:49 PM   #12
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I wish that had a scale on it. I like these charts the MS pumps out, seeing the real data is great. What you really need is a more normalized chart... You have an excel sheet of that? I could normalize it and really look at the numbers. Graphs are pretty, but don't really tell me crap about whats going on. Those little spikes every 400 rpm or so are either electronic jitter, or some really funky harmonics in the intake manifold (not likely).
The datalog is an excel sheet, so yeah, I have it somewhere. I'd have to find it, which might take a while as that datalog is pretty old. You can download MegaLogViewer for free and then look at the logs yourself. And then can move frame by frame and it will show you the exact number of anything it recorded.

And yes, that's noise causing the map line and coolant line to jitter. I latter changed some grounding and that resolved the issue.
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Old 01-13-2009, 10:59 PM   #13
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Well I know two things by looking at this. One either the port where you have the map sensor at is in a high pressure region (completely possible) or your map sensor reads atleast 3 KPa too high.

I think this might be throttle body restriction your seeing here. As a rule of thumb on powerloss. (Corrected map)/(Ideal map)=percent loss. Pressure in the intake manifold will make a difference. Err, a not easy to calculate difference, but as velocity goes up at the geometry limiting feature (whatever that maybe) losses will go up with the sqaure of that speed. A larger plenum can compensate for instantanious velocity spikes felt at the throttle plate which de-pressurizes the plenum, but these are normalized values from the perspective of the map sensor reading. (basically larger plenum makes power go up but not the pressure drop go down)

So what you really need to fix this problem is a larger throttle/opening, because regaurdless of how well you smooth the runner pulses, your engine still demands a certain airflow through the smallest bottleneck, which is going to be the plenum opening/throttle.

(I edited this alot I appologize, my posts sometimes don't read well on the first write, or even the fifth or sixth)
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Old 01-13-2009, 11:07 PM   #14
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Well I know two things by looking at this. One either the port where you have the map sensor at is in a high pressure region (completely possible) or your map sensor reads atleast 3 KPa too high.

I think this might be throttle body restriction your seeing here. As a rule of thumb on powerloss. (Corrected map)/(Ideal map)=percent loss. Pressure in the intake manifold will make a difference. Err, a not easy to calculate difference, but as velocity goes up at the geometry limiting feature (whatever that maybe) losses will go up with the sqaure of that speed. A larger plenum can compensate for instantanious velocity spikes felt at the throttle plate which de-pressurizes the plenum, but these are normalized values from the perspective of the map sensor reading. (basically larger plenum makes power go up but not the pressure drop go down)

So what you really need to fix this problem is a larger throttle/opening, because regaurdless of how well you smooth the runner pulses, your engine still demands a certain airflow through the smallest bottleneck, which is going to be the plenum opening/throttle.
I fail at uploading things. I have the logs, but I can't seem to attach them.... No idea why but it's not working. I can email them to you if you'd like. I've found 3 logs so far that have 7700-7800 RPM pulls.

I did the math a while back. I assumed a 90% VE and figured that the there's no way in hell the TB is the restriction. You could do the math I guess, but I really don't think it's the problem. IMO, the stock plenum is too small. Have you ever seen a stock 99' intake manifold? It's got like 1L worth of volume tops. It's tiny.

And the map sensor had a very small diameter and long hose feeding it such that is would see a smoothed map reading. Helped low RPM idle a bit.
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Old 01-13-2009, 11:25 PM   #15
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I got a 122.2 ft/s through the throttle orifice at 7800. While thats not scorching your going to see losses. If you assume you loose 10 percent of that flow area from the throttle and its turbulences your upto 135 ft/s. Thats pretty high really. If I was extra motivated I could use bernoulli to calculate the pressure differential, but I'm hungry and damn tired.
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Old 01-14-2009, 08:50 AM   #16
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Didnt the dynos they posted show that the tq curve was almost identical and then pulled all the way to red line instead of dying with the gutted manifold??
Ehhh I guess I was wrong. There was a difference looks like...VICS not working on the "stock" IM pull.

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Old 01-14-2009, 10:18 AM   #17
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I would like to test a gutted manifold vs. my "cleaned up" 00 manifold back to back on a dyno. I have kept my eye open but I have not found a cheap one yet.

I do know one thing though, VICS certainly does work well (enough for me to go blindly screwing with it) at least on a naturally aspirated car. It was worth 7 ft/lb peak and 10 ft/lb in the midrange on my car.
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Old 01-14-2009, 06:53 PM   #18
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OK, so now this is even more confusing..

My build will be done in about 1 month..

DO I do the Pat mod or the Paul Mod????

I am thinking Pat's Mod is on the safe side and maybe I should just do that until this is all figured out ...
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Old 01-14-2009, 06:56 PM   #19
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I have to say it pulls pretty good up top. See my kill story. It pulls better than I originally said. It does well. I'll dyno it one day, but I'm gonna say do it my way for now. It definately helps. And if you keep the VICS butterflies working, you shouldn't loose any torque like the graph above.
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Old 01-14-2009, 08:28 PM   #20
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Yeah, thats what i was thinking..

Cool.

I also read the Kill, I just didnt post a congatulatory post
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