MSP volumetric efficiency

peepsalot · May 27, 2005

Spooled said:
Ha, I was just going to see if anyone had tried that. I noticed that they don't post an email address in the contact section.

Yeah, they are sneaky, there was a single hard to find page I found that had an email address on it. I had to do a search on the site for "email" to find it.

Spooled · May 27, 2005

Can someone quickly explain roller and flat tappet cams to me? Which do we have for intake and which for exhaust?

TurfBurn · May 27, 2005

We have flat tappets in all cases... we have no rocker arms or rollers... direct flat tappet valves.

TurfBurn · May 27, 2005

And this is the map for the Large 16G... I run the evo derivative which spools faster and flows another 50-80 cfm more... it is also a perfect match for the car... and the best part is... it costs less than HALF that of the GT28RS as you can pick up an EVO III 16G for about 500 bucks.

Spooled · May 27, 2005

So is the difference basically just that the cams directly push down on the valve (I'm assuming the contact point is a tappet?), and the roller refers to the rollers on the arms of a pushrod engine?

Spooled · May 27, 2005

TurfBurn said:
And this is the map for the Large 16G... I run the evo derivative which spools faster and flows another 50-80 cfm more... it is also a perfect match for the car... and the best part is... it costs less than HALF that of the GT28RS as you can pick up an EVO III 16G for about 500 bucks.

It looks like an FS-DE could run that at about 6psi with decent results. Am I right in saying that?

TurfBurn · May 27, 2005

Spooled said:
It looks like an FS-DE could run that at about 6psi with decent results. Am I right in saying that?

Try 22 psi.

Spooled · May 27, 2005

The only thing that I see is that the efficiency of the center island is only 71 percent. That seems a little low.

Spooled · May 27, 2005

TurfBurn said:
Try 22 psi.

Oops, I was subtracting 14.7 for atmospheric when looking at the pressure ratio. Isn't 1.0 = 14.7 atmospheric, so 0.4 * 14.7 = 5.88?

TurfBurn · May 27, 2005

No PR = (Boost + 14.7)/14.7

Spooled · May 27, 2005

It must be 14.7 * 1.4 = 20.58 if it's not an absolute scale???

Spooled · May 27, 2005

TurfBurn said:
No PR = (Boost + 14.7)/14.7

Ahh... got it, thanks.

TurfBurn · May 27, 2005

Spooled said:
The only thing that I see is that the efficiency of the center island is only 71 percent. That seems a little low.

Yeah that is one downside... but this turbo spools as fast as a T25.. The Evo III that I have is a little more efficient than the map you see, so that helps as well and the overall average for the entire width is closer to that of the GT28... Keep in mind you are only talking about a couple of horse and things that can be overcome with other things.. just think how much more intercooler you can get for the 5 bills you saved buying this turbo instead.

Spooled · May 27, 2005

TurfBurn said:
Yeah that is one downside... but this turbo spools as fast as a T25.. The Evo III that I have is a little more efficient than the map you see, so that helps as well and the overall average for the entire width is closer to that of the GT28... Keep in mind you are only talking about a couple of horse and things that can be overcome with other things.. just think how much more intercooler you can get for the 5 bills you saved buying this turbo instead.

I can totally agree with that. Performance/$ that turbo rules. They used to use those on the old DSM's (same engine as the Evo, pretty much). It's definitely proven!

TurfBurn · May 27, 2005

Spooled said:
So is the difference basically just that the cams directly push down on the valve (I'm assuming the contact point is a tappet?), and the roller refers to the rollers on the arms of a pushrod engine?

Not completely.. I'm not as up and up on that as I should be... but the jist has to do with how the lobes get shaped because of the mechanics of the different systems... and then you have to deal with the contact point etc... Our OHC motors are very different in how they apply force to the valve than a pushrod motor. And flat versus roller is a pushrod thing.. and I don't do pushrod motors... all you need to know is that we have "solid rocker" systems in that we have a solid cam and solid tapets... and the cam directly pushes onto that tapet to push down the valve.. traditionally roller systems have a bearing that rides along the cam... so you don't have the "impact" and some of the friction levels of two solid metal surfaces grating across eachother.

TurfBurn · May 27, 2005

Spooled said:
Wouldn't the lobe seperation be the same thing as altering the overlap? I wouldn't think that we would benfit from much less overlap, and I understand that too much overlap would just blow fuel out the exhaust ports, but I haven't really seen anyone play with the phasing on an MSP yet. I've heard rumors, but no actual reports on successful gains. Also, I think the people that were playing with that had a different turbo. Any thoughts on this?

Yes and no.. lobe seperation allows you to advance/retard the cams individually. It does also affect the seperation... but that is the big advantage of a DOHC system in that you can seperately adjsut the intake and exhaust side and open and close that seperation angle... I have to re-read the section on it but that book that I mentioned that peeps bought talks about turbo motors and which kind of cam advancement/retard you want to improve your output and on which cam specifically.. but yes it affect the lobe seperation angle, but it allows you to leave one cam in place and still open close when it did before, but then have the other one open/close sooner or later etc...

Spooled · May 27, 2005

TurfBurn said:
Not completely.. I'm not as up and up on that as I should be... but the jist has to do with how the lobes get shaped because of the mechanics of the different systems... and then you have to deal with the contact point etc... Our OHC motors are very different in how they apply force to the valve than a pushrod motor. And flat versus roller is a pushrod thing.. and I don't do pushrod motors... all you need to know is that we have "solid rocker" systems in that we have a solid cam and solid tapets... and the cam directly pushes onto that tapet to push down the valve.. traditionally roller systems have a bearing that rides along the cam... so you don't have the "impact" and some of the friction levels of two solid metal surfaces grating across eachother.

Wow, it seems like there is a lot to benefit from having a roller touching the cam as far as friction and wear.

Time to make a trip to the shop for exhaust!

Protege2ner · May 27, 2005

Spooled said:
Oops, I was subtracting 14.7 for atmospheric when looking at the pressure ratio. Isn't 1.0 = 14.7 atmospheric, so 0.4 * 14.7 = 5.88?

If im not mistaken the 14.7 is a ratio as in 14.7:1. It is the stoiciometric air/ fuel ratio ("read" perfect mix). Atmosperic pressures are usually alot higher unless expressed in BAR

apocman · May 27, 2005

peepsalot said:
I just emailed a contact at garrett asking for them to provide the T25R compressor map. We'll see how that turns out...

You get that done and I'll drive to Austin and ******* detail your car by hand!!!!

it has to be for the T25R though and not another variant

apocman · May 27, 2005

Man, this is how a thread should read!!!!! perfect educated not blanket statement posts!!! People break things down and explain why they are saying something!!!! that's it!!! I'm making thread love to all you "keep it data real" posting freaks!!!

(humpleg) (kissass) (rockon) (nana) (alright)

MSP volumetric efficiency

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