Get serious about VVT
 

VVT tune, Tec 2 vs. Hydra in a CSP car, + E85 - MX-5 Miata Forum

I keep seeing stuff like that. A good VVT tune verses VVT at full retard (or advance). So?! It's almost meaningless. Example:

Take the Miata, extend the driveshaft and hang the motor over the front bumper. Wow, now it handles like shit. Then, take it and hang it off the back bumper, wow, it handles like shit. But put in an adjustable one, and look how well it handles.

No surprise. You're comparing the two worst cases to an adjustable one.

I want to see a plot with the VVT fixed somewhere sensible - you know, 0 advance OR retard. Not fixed at one end.

I'd much rather see "I picked up 5 ft-lbs in the low end and 3 hp on the top end over the "best compromise", than "I got 65 ft-lbs more in the low end than I did when I pulled three spark plugs and ran diesel"

C'mon people. Show me something worthwhile.

not worth the effort.

Devil's advocate: Why not?

http://y8spec.com/dyno/vvt_range.jpg

purple line is 3 degrees retarded.

you can interpolate mentally based on advance, retard, and half way between, can't you?

or are you 3 degrees retarded?

You are 3-degrees retarded. How does your "dynamic" cam profile (at best) compare to my super-awesome 99 cam?

somewhat less duration, but i have more overlap except that I have less overlap too.

I thought the 01 intake cam had the same duration as the 99?

For a CSP car completely worth the effort to run one of those motors with working VVT.

Miata MX5 camshaft specifications

randy claims slightly less, but not complete data. some day I will degree one and measure it.

Absolutely. With a turbo, even things like broken ring lands or a hole in the block can be compensated for with more boost. But NA you actually have to try to make power. And everywhere, for CSP.


I thought it had more. I was pretty sure the VVT cam was a lot better than the 99. Ah, no, short duration, high lift. Seems like with better cams it'd be awesome. Interestingly, the earliest dyno runs FM did showed the '99 and the VVT car basically the same. :-)

The MSM is decent, though, on intake and exhaust. I think the VVT exhaust is better, too, than 99. There was a thread on m.net which listed it out pretty well.

Yeah - the posts I read are all "When I measured it, I got something different"

Interesting how from 4200 to 4800 RPM y8's dynos don't show a large difference in output no matter where the cam phase is. In the n/a motor retarded was hugely weaker - it needed overlap to get the VE from the exhaust scavenging. This effect is probably more pronounced with a proper header like the guy in the post.

y8s are you confident that the Hydra software hits the target cam phase? Did you datalog actual phase and confirm it was hitting its targets at around the time you did these dyno plots?

Hydra doesn't log the phase so I have no idea. I only know that full retard is full retard.


The adaptronic on the other hand....

(note this is an old map and the VVT isn't set up at all--the stock ECU is controlling VVT)

Matt:
Wow, yeah, that's pretty amazing. :-) Can you find a way to watch the cam with a timing light? Hmmm, guess not. An o-scope would tell you, but kinda a PITA for a quick test.

(Will edit when more ex info gets posted)


Jason: Your PM's are full. Check the alternator thread, people are having issues with the light not turning off all the way, would like to hear your thoughts on it.

And that's very odd, about the midrange not caring about cam timing, you're right, I've seen those graphs but it never struck me.