IM dyno comparo: VICS vs VTCS vs Flat-top (EUDM)
03-20-2012, 03:12 AM
#43
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Because intake manifold resonance tuning depends on volume flow and not mass flow. In boost, the volume flow in the manifold is the same - it's just denser. The speed of sound changes little with pressure. This is also the reason why the correct VICS switchover RPM is close to 5500 RPM, both for n/a and boosted engines.
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03-20-2012, 03:23 AM
#44
My theory is that it's not worth the effort, and here's why.
a) We know it makes zero difference N/A.
b) N/A is effected by VE changes where FI really isn't.
c) While gutting it may affect VE, it does not change the fact that your throttle body & your intake runner sizes are not changed a bit.
d) Therefore, I theorize that it won't make a bit of difference on a FI car except if you like adding mods to your mod sheet.
a) We know it makes zero difference N/A.
b) N/A is effected by VE changes where FI really isn't.
c) While gutting it may affect VE, it does not change the fact that your throttle body & your intake runner sizes are not changed a bit.
d) Therefore, I theorize that it won't make a bit of difference on a FI car except if you like adding mods to your mod sheet.
b) Change in VE doesnt change power output for FI?
c) But intake runner sizes are changed.. especially if using the vics butterflys to get the dual lenght runners effect.
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03-20-2012, 02:55 PM
#46
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My VICS is zip-tied to use only the long runners because I'm power limitted in my class but wanted that nasty torque. I don't have a dyno yet and the dyno won't tell the truth because I had bent valves previously.
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03-20-2012, 03:51 PM
#47
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Originally Posted by JasonC SBB
Yes operational, at 5400 RPM. I find 5600 RPM the "correct" point when RPMs are slowly rising. If RPMs are rising rapidly a lower switch point is better.
I was talking about say, 2nd gear vs. 4th gear. In theory for 2nd gear you need the switch point lower, and higher for 4th gear. 
Yes operational, at 5400 RPM. I find 5600 RPM the "correct" point when RPMs are slowly rising. If RPMs are rising rapidly a lower switch point is better.
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03-20-2012, 04:27 PM
#48
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/\ I am of the same mindset, though have don't have much proof of this theory (but neither do like 99% of us discussing this). A bottleneck in the intake is more significant than a bottleneck in the ehxaust IMO, and I'm not sure simply enlarging the plenum while keeping stock tb and runners will do much (on top of what the VICS already does). But again, intake mani resonance, waves, etc etc all that isht is over my head....I just know the basics
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03-20-2012, 04:37 PM
#50
Also: have you seen how terrible the throat is between the TB and IM on a 99+?
I've changed my mind at this point about messing with the stock IM altogether. Not worth it. Going to leave hte 01 as is and run OBX/honda or make a custom sheetmetal one if I exceed 300whp
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03-20-2012, 05:29 PM
#51
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Call Magnus Moda or AMS and (profit).
Profit is in parentheses as accounting notation of a negative value.
Profit is in parentheses as accounting notation of a negative value.
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03-20-2012, 06:01 PM
#52
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At that point it would be stupid not to just fit a whole 'new mani.
Also: have you seen how terrible the throat is between the TB and IM on a 99+?
I've changed my mind at this point about messing with the stock IM altogether. Not worth it. Going to leave hte 01 as is and run OBX/honda or make a custom sheetmetal one if I exceed 300whp
Also: have you seen how terrible the throat is between the TB and IM on a 99+?
I've changed my mind at this point about messing with the stock IM altogether. Not worth it. Going to leave hte 01 as is and run OBX/honda or make a custom sheetmetal one if I exceed 300whp
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03-21-2012, 01:06 PM
#57
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b) Not really. For any pressure row, if you have a stable AFR output across the row & there are swings in VE, you will see corresponding swings in your fuel values across that row. Since FI forces the air in as opposed to coming in under a vacuum, the end tuned result is most typically a smooth, flat fuel row with a slight rise around torque peak. Doing this same excercise in a N/A car you will often see dips & bumps in the fuel curve corresponding to VE changes.
c) Runner length or volume may be changed, but the TB diameter & port diameter are not changed. Neither is the valve lift. These are limiting factors.
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04-19-2013, 12:52 AM
#58
Sorry to bump this ancient thread, but I figure its better than starting a new one. For a mostly stock Miata track car with some simple bolt ons (intake, tubular header), do you think the 99-00 VICS intake manifold would be better for area under the curve than a squaretop manifold? It's hard to say based on the dyno here, since the engine already makes like 60% more power than stock.
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04-19-2013, 10:17 AM
#59
A lot of people (me included) are subscribing to using the VVT head + the Squaretop.
The VVT head will make up/mask any mid-range losses with the Squaretop, and you still get the high-end power of the Squaretop. It is a compromise, but if a compromise feels this good, I really don't mind.
The VVT head will make up/mask any mid-range losses with the Squaretop, and you still get the high-end power of the Squaretop. It is a compromise, but if a compromise feels this good, I really don't mind.
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04-19-2013, 10:37 AM
#60
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Here are some more comparos from the same sessions on our 11:1 Stroker VVT Hydra motor.
Run 31 is the VICS, and run 25 is the FTM. Gain some, lose some. For the price difference I'd do VICS w/ an adjustable intake cam gear or VVT.
Run 31 is the VICS, run 20 is VTCS.
Run 20 is VTCS, and 25 is the FTM.
Run 31 is VICS, Run 51 is w/ Extrudabody IRTBs. BTW I really don't care for IRTBs on a car you need to reliably drive.
And finally, we have run 31 w/ the Stroker VICS vs. a 1999 built 1.8 with our externally gated FM2R turbo kit running the GT2871R turbo. This is our laggiest turbo setup on a smaller engine, time to cry in your beer about response. :P
Run 31 is the VICS, and run 25 is the FTM. Gain some, lose some. For the price difference I'd do VICS w/ an adjustable intake cam gear or VVT.
Run 31 is the VICS, run 20 is VTCS.
Run 20 is VTCS, and 25 is the FTM.
Run 31 is VICS, Run 51 is w/ Extrudabody IRTBs. BTW I really don't care for IRTBs on a car you need to reliably drive.
And finally, we have run 31 w/ the Stroker VICS vs. a 1999 built 1.8 with our externally gated FM2R turbo kit running the GT2871R turbo. This is our laggiest turbo setup on a smaller engine, time to cry in your beer about response. :P
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