High altitude yes but A/B same day/dyno is relevant. Still a useful data point even though it is a vtcs.

 

So Kosher salt?

He still doesn't have VVT running, so he's going to get that tuned. I don't think the basemap for the vvt really helped him so he's gonna take it to get tuned.

Troof. Thanks again for doing this.

Unsure how the stoker motor stacks up. Absolute gains will be different, but I guess relative%'s should hold up.

 

Thank FM, they did the turbo A/B. Motor specs, fuel, boost level,compressor type don't really matter. Just that it was F/I and not N/A. We're not looking for absolute numbers because those are meaningless. We all just want to see the difference between the S2 and an OEM manfold when it's force fed.
Now we have VTCS numbers which is nice to see. Next we'll see squaretop vs S2. Hopefully on the same engine/tune so we can see a A/B/C result.

 

But numbers count! Can't sell parts on percentages!

 

You had given an educated guess that the pattern you saw normally aspirated would hold with forced induction. I would say that FM's result is confirmation of that.

 

Sorta, We tested against the squaretop, FM tested against at de-butterflied VTCS. We, and most of the Miataverse see a few percent gain with the squaretop vs the VTCS at higher RPM. FM appears to have seen no gains on the squaretop vs the VTCS/VICS which is odd though.

 

So I wouldn't be misinterpreting that graph if I observed that the VTCS is the better manifold everywhere except >6000rpm?

 

you would be actually, considering that plot shows it's only marginally better between 3.5 and 5k. everywhere else is equal or much worse.

 

If you want mid-range you're better off with a VICS than even a de-butterflied VTCS. The VTCS is pretty much the worst manifold you can bolt to an NB head.

--Ian

 

Our best ever torque between 2000-5500 was with an unmodified VICS with two switching points tuned on the dyno for that engine. OEM has one switching point at 5500 IIRC. We often had trouble detuning our 2.0L race engines in PTE with the squaretop so we switched to the VICS. Nipped a bit of top end but allowed even more torque. We built a fancy 2.0L BP6D (N/A) PTE dyno classed motor in 2013 that made within 5whp of peak power from 4000-8500rpm. So yeah, the VICS is the low end torque monster of all the options. Squaretop seems to give the greatest overall power area, S2 greatest peak. With a 6psd on a road racing car with peaky powerband or Rotrex the S2 might be just the ticket.

 

I've been watching these threads closely, as I've been considering changing out my VICS IM for either the Skunk 2 or Squaretop. Based on Emilio's post above, it sounds like I might as well stick with what I have for the best street drivability.

 

Seems VICS win for street drivability as well as autox to drive out of corners with a bit of extra hp / torque.

 

If you can get it onto the dyno with VICS active, play do pulls all open and all closed. If you have more than one crossover point, there is power to be gained with a second switching point. This how we tune variable cams too. Bump the entire map in steps. Compare all runs. Use a combination of the values to make a full table. Run at multiple loads too, not just WOT.

 

Not sure where you guys are reading that the vtcs was gutted. The fm post and dyno graph state "stock vtcs manifold".

 

it doesnt' even matter. Because the butterflies aren't even what kills the power

 

Per the diagram in this post ( https://www.miataturbo.net/engine-pe...41/#post715625 ), I had always just assumed that VICS was an on / off switch and "to determine the best crossover point: do two dyno runs, one with it open and one with it closed. The point where the curves cross is where you set the change." Is that wrong? How would you find the second crossover ? Thanks.

 

This isn't the thread for the 10 billionth clueless confusion between vics and vtcs. There are (MANY) other threads for that.

 

This.

 

The VVT Mega Page ? The Car Passion Channel

 

Apologies for taking thread off topic. I was just curious about the second VICS activation point. Anyways .. back to Junk 2 discussion while I go google.