AbeFM

iTrader: (3)

Then the specific question is are the differences between the two heads (assuming no cam regrinding or parts swapping, but including some light grinding on the alum) pointing to a clear winner - i.e. will the grind of the VVT head prevent the sort of power a longer duration MSM cam can give you.

hustler

iTrader: (6)

while you're chasing down cams and unique heads, I'll just give it a couple more pounds of positive manifold pressure.

AbeFM

iTrader: (3)

Not chasing anything - I have them sitting on my workbench.

And, less boost = less backpressure, less lag, less heat, more timing, all around more performance and effeciency. THEN I can run more boost.

AbeFM

iTrader: (3)

From Integral's site:
http://www.integralcams.com/miata.htm
1.8 Mechanical Lifter Cam Profiles, 1999-2001 engines
Seat Duration Cam Lift
Stock (intake/exhaust)

248°/251°


.326"/.350" (8.28 mm/8.89 mm)
Stage 1L

252°/256°


.329"/.353" (8.36 mm/8.97 mm)
Stage 1

251°


.360" (9.14 mm)
Stage 2 257° .370" (9.40 mm)
Stage 3 263° .385" (9.78 mm)
Stage 4 274° .395" (10.03 mm)
Stage 5 288° .425" (10.79 mm)
Stage 6

292°


.440" (11.18mm)




1.8 Mechanical Lifter Cam Profiles for Turbocharged Engines
Seat Duration Cam Lift
Mazdaspeed stock factory turbo (intake/exhaust) 242°/244° .370"/.350" (9.40 mm/8.89 mm)
Stage 2 turbo (intake/exhaust) 257°/256° .370"/.353" (9.40 mm/8.97 mm)


1.8 Mechanical Lifter Cam Profiles, 2002-2005 engines with variable intake valve timing
Seat Duration Cam Lift
Stock (intake/exhaust) 242°/244° .370"/.350" (9.40 mm/8.89 mm)
Stage 1 (intake/exhaust) 252°/254° .373"/.365" (9.47 mm/9.27 mm)


Out of all this I get:
VVT: Stock (intake/exhaust) 242°/244° .370"/.350" (9.40 mm/8.89 mm)
MSM: Stock (intake/exhaust) 242°/244° .370"/.350" (9.40 mm/8.89 mm)
'99: Stock (intake/exhaust) 248°/251° .326"/.350" (8.28 mm/8.89 mm)
'94: Stock (intake/exhaust) 233°/254° .318"/.339" (8.08 mm/8.61 mm)
'90: Stock (intake/exhaust) 236°/248° .310"/.310" (7.87 mm/7.87 mm)

Also, I learned that the mazdaspeed site is filled with morons and maybe three guys who aren't morons but they don't know anything. :-)

The interesting thing from this info is the exhaust cams are NOT the same, according to these guys. "seat duration" is a few degrees longer on the '99 cams, though lift is the same. The lift is higher for the '01 and up intake cams across the board.

For that matter, the MSM and VVT cams have the same exact specs?! Good lord! I wouldn't have thought that...

If I had to guess, I'd have said the specs for the VVT and the '99-'00 cams were swapped on their page. I guess I'll just go home and measure it. :-)


Anyway, if all this is true, then there's no reason to run the MSM head, if the cams are THE SAME, then the only thing I'm losing out on are the MSM valve springs - since a few folks have said the valves themselves are the same.

AbeFM

iTrader: (3)

Good lord! The GUDE site says very little, but....

Camshaft 98 - 05 Mazda Miata MX5 1.8L DOHC

PART NO: MCZS04

DESCRIPTION: Strong pull from 4000 to redline.

POWER BAND: 3000 R.P.M. to 8000 R.P.M.

IDLE: (Good)

SPECIFICATIONS: Intake: LIFT – 0.420 DURATION – 231

Exhaust: LIFT – 0.400 DURATION – 228

Wow, that's some lift, isn't it? I've seen people saying 370 was too much. I wonder what they cost?

y8s

iTrader: (8)

you may want to verify that a 420 lift cam will actually rotate in your head without hitting the casting!

AbeFM

iTrader: (3)

Info from Integral:

which followed
Way better than Gude's first letter of "600 hp is do able call bill 951 317 5092". I mean, they have a nice site, maybe they do know what they are doing, but 1) it's not what I asked, and 2) they told me NOTHING.

y8s

iTrader: (8)

I'm not sure I understand. Lets say I can adjust my cam to have overlap only when I'm below 100kpa and then not when I'm in boost. Isn't that better than always not having overlap?

And contrary to what Integral says, I tried changing the cam timing at a set boost level and it made it worse to have it retarded at low RPM in boost. A graph will illustrate:

The green line is with the VVT set to be advanced 6 deg until 3psi and then retarded to -12.5 above that. It is not switched at any particular RPM (just boost).



note how the green line follows the "advanced" line until it hits 3 psi and then drops down to the "retarded" line? Clearly the overlap is helping there. It probably varies for different turbos since scavenging and backpressure play a role, but for my big turbo, it's good into the 4k range.

y8s

iTrader: (8)

here is a comparison of the datalogs from that run

run 3 and 6--
3, bright colors, is the full advance run that spool sooner
6, dimmed, is the switch@3psi run that spools slower

patsmx5

iTrader: (16)

It's crap like this that makes me second guess companies like Gude.

First thing I bolded and underlined- He's mostly wrong. This is one of the benefits of turbocharging vs supercharging. With a really high HP setup, overlap is good to clean up the combustion chambers, ridding them of hot gases and already burned gases so that you get it completely filled with new air/fuel, not 92% new air/fuel. Helps to "cool" the combustion chamber as well so a bit of knock suppression is had. With an SC through you loose some of your intake charge doing this and it results in less HP, through more HP per "measured" pound of boost. But with a turbo, it has no problem maintaining the same "level" of boost.

Second thing I boldded he is talking about exhaust cam timing, not intake cam timing.

Third fixed cam timing is not good. It's a compromise.

skidude

iTrader: (3)

Ok, I'm sure I'm way off here since you're all smart and seem to know what you're talking about.

Why not just use the MSM head and call it good? It was designed for boost. The VVT head was not designed for boost. I agree that VVT is cool, and has its merits but I don't know as it would really be worth all the extra time and effort if you have the MSM head sitting on a bench.

If I'm way off, just tell me so and I'll shut up.

patsmx5

iTrader: (16)

Way off.

AbeFM

iTrader: (3)

Pat: Thanks for posting my ramblings whilst I'm too lazy to do it myself.

Matt: My thought was just the opposite, more advance down low to get more spool, then back it off to where you get the best power. What are good values? I dunno. :-)

Still, it seems unless 5* advanced (to pick an arbitrary number) is the absolute best under all circumstances, you can only do better with VVT - unless your ability to control it is outside the bounds where you're not hurting yourself. I expect to start there, but not to finish there.

But so far (haven't been home in a while) I've seen nothing to point to any benefit of the non-VVT head over the VVT, though my toyota COP's might be hard to get on there? So it seems if I'm to put money into cleaning up a head, the VVT one is the way to go. Yes, it would be awesome to have better cams done for it down the line, but I think it's a bridge to cross when I get to it. In the mean time, toss in some valves (?) and pistons and portwork and get it going.

patsmx5

iTrader: (16)

You'll want to adjust the intake cam mainly to control intake valve closing w/ respect to cylinder position. The engine asks for the same amount of air on every intake stroke no matter what. Piston goes down a bore of the same displacement and creates a negative pressure every time. Problem is, as RPM goes up, the time that the valve is open goes down. As RPM goes to infinity, the open time of the valve goes to zero. Not ideal.

Sure would be cool to build a model that considered all the variables and run it to maximize total air flow and see what kinda curve we would get. It would be complex though. Maybe model a few points or something and build your cam timing curve off of that.

y8s

iTrader: (8)

wha? opposite of what? you described how I run it. it changes with RPM, not with MAP. at least not much. mazda's engine highlights suggest somewhat more detail than that (at least up to 101kpa) but for now...

Someone pays for my dyno time and I'll do runs at whatever advance / retard numbers you want. hell, i'll do every value from +6 to -12.5 in increments of 2 degrees.

oh and abe, regarding COPs:



1. you have to cut the flanges on the coils themselves (and gaskets)
2. you have to hone the holes in the valve cover a little so the coils fit (or at least I had to.. another part no may fit fine)

AbeFM

iTrader: (3)

Yeah - I have to admit, I would definitely take measured values long before computed ones! I like theory, but it rarely measures up.

Awesome news on the COPs, I was a bit worried about it, though sure I could make something work - but that's pretty clean.

for now, you can just call me "The Open Loop".