Hey Matt, If you watched the Singapore F1 race, did you catch the part about them using pneumatic valves due to the fact that at 18k rpm they would pretty much experience a permanent valve float with springs? Interesting stuff. Curious to see when that tech will filter down to street level.
There was a post on MiniTorque about that... it's basically an airspring. What's cool about that is you can make it very stiff with little effective mass. Matt
Nice link. Always wondered about how they actually worked. Wonder when it will get down to our level?
My guess is it will take a while... We've got some time left doing variable lift and timing with current tech.... But the FIAT application may be the tip of a new valve control iceberg, so to speak. [ame=http://www.youtube.com/watch?v=5IrPcmMHqHE]YouTube - Fiat Multiair Technology Explained[/ame] It's not a true pnumatic system but it's a step beyond the current mechanical variable lift tech, like on the Price Cooper engine. It's pretty cool! But I bet it will give tuners fits... Matt
Matt... I have seen this already on OEM cars. Man, for the life of me I can not remember which.. Cad/ Jag / Merc.... but it isnt that new, and is being used today on some topend street family cars. And it isnt that the tech isnt here for the MINI... just the cost to do it at this time. yes? I think that the cost of a mod is what is keeping that mod off the car. lol Just me..................................... Thumper
Other pnuematic systems may have been tried, but none are currently offered on any car I know of. But this FIAT system is being used on small, cheap cars. Also, when compared to the hardware that goes into the BMW variable lift tech, this seems like a better approach because the hydraulic control is faster than the rotating cam that's used by BMW. None that I am aware of do what this system can do with basically programmable ramp rates for the valve that are arbitrary in thier shape. Most of the ones that I'm familiar with use either descrete different lobe profiles (like Honda VTEC) or use a variable ratio rocker arm (like BMWs variable lift technology). I did a few minutes of searching, and can't see any apps of anything more compable than this. The pure hydrolic listed in the F1 reference is a camless desgin. This one isn't, but with good control of the solenoid, it get as close as any system out there. Matt
Using mechanical components to develop the force and electronic solenoids to control the motion of the valve is similar to the current method used on Diesel fuel injection systems. These systems pulse the injector at the beginning of injection for emission reasons. We see the difference in the noise. Modern diesels do not go knock knock at low engine speed.
Some numbers for Supertech stuff. Dual Spring 44.5g Ti retainer 5.7g 1.8mm oversized intake valve 45.3g 2.3mm oversized exhaust valve 40.6g Keeper .7g
So the supertech double spring is actually lighter than the PAC racing beehive spring? Isn't the beehive spring 48.8grams, about 10% heavier than the supertech dual spring at 44.5 grams?
They are also just a bit less pressure than the OEM springs when installed, and when they are opened. just a thought..... Thumper
Yep... your math isn't failing you! The PAC has a significantly higher seat pressure and spring rate. You can see it in the windings. There are also distribution issues (lighter end of the spring is what moves fastest), but cause this beehive isn't a huge one, they are small (but real). The SuperTech uses a spacer. At zeroth order this mass doesn't count. If surge comes into play, it does. I have no clue about how to account for it in simulation though. Anyway, all different ways to skin the cat! And the numbers are what they are. Matt
From memory... OK, I gotta say I hate manufacturers web sites! The Supertech site blows, and all the PAC numbers are for a different application so it was time to use some Excel. It looks like the seat pressures for the PAC spring are about 130 valve closed, and about 255 at 11 mm lift. Rate is about 300 lbs/in. The seat pressure is higher for the PACs, both open and closed. The numbers change a bit depending on the actual spacer thickness used. Jan posted some numbers for the springs as well on the a Minitorque thread, but he left out the spacer thickness and mass. (Nathan, do you have those numbers?) But like I've posted before, I don't know how to take into account the use of spacers. If they stay put, the mass seems like it doesn't come into it, but if they don't stay put, the mass does come into it! Ack! My head hurts! Anyway, what I can say is that both sets are better than stock, that's for sure. And better than the Cosworth single spring set-up (that in itself is a bit better than stock, 1 gram lighter and more consitant in rate). What isn't in the mass and rate numbers starts getting beyond my skills to speak to in terms of engine performance and MINI applications. These are things like coil bind (limit of valve lift), ressonance and surge effects, and what are the real consiquences of running spacers. Matt
your head should hurt................when does a spacer move like a spring? the mass is not relevant...........
Fiding truth from fiction takes work! If the spring is surging and loses contact with the head, there can be motion of the spacer. If it's not then no big deal, like I wrote before. Matt
I've killed off a lot of posts here including my own that did nothing to move this discussion forward. Here is the deal. There is a lot of good info in this thread, however there are parties that stop at nothing to make it look bad when there is no reason to except to further personal agendas between competing vendors. That ends in this tread now. Now everyone go cool off for a while...and post again here later when your blood pressure is lower and you have something to contribute.
What I've learned... when I started all this, it was to educate about valve spring technology. I hope that I've helped many with that. When it comes to specifics for the MINI, in my learning about valve springs, it's been a long and sometimes painful journey. The stock springs work in the stock motor. An inexpensive way to get more headroom is to just use Ti retainers with stock spring. But keep in mind the variation in the stock springs is larger than any of the aftermarket I've looked at (and I've personally only looked at the stock, stock replacement Cosworth, and the PAC Beehive), so you may have to sort through a bunch to get a mached set, or shim them to get the same seat pressure. Also, the Cosworth single spring has been obsoleted by Cosworth, so slowly but surely, they will no longer be an issue. The Supertech and the PAC springs are both better performers than the stock or Cosworth single spring for high lift / high RPM applications still. What the final limits of each are I don't know. But the limits aren't based just on the spring and retainer, the rest of the valvetrain matters as well. So it goes full circle, the high performance dual spring or beehive aren't for the street car. They are for those with modified valvetrains and raised red lines. Matt