MelloYellow

Can we list all known/available ATI pulley sizes and the advertised boost?

4.10 = 5psi?
3.40 =
3.20 = 10psi

Which is the 7# and which the 8#?

Others?

Thx!

Black LS1 T/A

Actually, with a stock internals motor and stock exhaust, I achieved 12 PSI with the 3.20" pulley and 5 PSI with the 4.10" Pulley.

Assuming boost is a linear function of a change in pulley diameter, these values mathematically derive a slope of
-7.8

If I use +2.0 as as a starting point for pulley size (to make it easier to graph the y-intercept), I get a y-intercept of approximately +21.4 (via a graph).

From this graph I can derive the following equation :

y = -7.8(PD - 2) + 21.4

where PD = Pulley Diameter and y = new PSI.

So, for a Pulley Diameter of 3.40", the calculated Boost = 10.5

A 3.6 diameter pulley would yield 8.9 PSI of boost.

A 3.8 diameter pulley would yield 7.4 PSI of boost.

If, for instance, a guy achieved only 3.5 PSI of boost with heads/cam and performance exhaust (say, headers, aftermarket y-pipe and a cat-back) with the 4.10" pulley, but 10 PSI with the 3.20" pulley, these conditions would provide a slope of approximately -7.2 with a y-intercept of approximately +19.0.

Use the equation above to derive the boost values for various size pullies.

In this case, a 3.60" pulley would give a boost of ~ 7.5 PSI of boost.

I think (I could be wrong) the advertised boost is what they found the norm to be with, say, a stock vehicle and the 4.10" pulley (4.55 to 5 PSI) OR a modified vehicle and the 3.40" pulley (7 PSI) OR a HEAVILY modified vehicle and the 3.20" pulley (8 PSI).

But we all know there are so many variables to this: degree of mods, elevation, variations in cleanliness of the air filter, even how tight or loose you make the belt.

BUT, as I've shown, if you know what your boost is with two pulley sizes, you can approximate the outcome for any other pulley size, everything else remaining equal.

Of course, you don't REALLY need equations to do this. Plotting points on a graph paper and drawing a line could give you the same thing. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

TIFWIW <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

MelloYellow

Thx. For the real world estimates.

What size pulleys are available from ATI and in what increments? Are the pulleys available in any size in -.1" increments?

Also, just looking at ATI advertised boost ratings, how does ATI market theirs. If you ask for 10# do they ship you a 3.20 or a 3.40? Does ATI consider their 3.20 a 12# pulley?

If you buy a P1-SC 7# kit, what size pulley are they shipping?

<small>[ June 03, 2002, 11:52 AM: Message edited by: MelloYellow ]</small>

Mark C

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Black LS1 T/A:
<strong>

Assuming boost is a linear function of a change in pulley diameter, these values mathematically derive a slope of
-7.8

</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Its not linear. The relationship is at least second order, and probably third. Try to plot it this way:

As X goes to infinity, boost would go to 0. As X goes to 0, boost goes to infinity (well, we all know it really wouldn't, but we would only look at the real world portion of the curve).

Of course, to be accurate with the second order equation, you'd need another data point. I'll bet if you make some educated guesses and try out a few second order curves, you could get pretty close. Geustimating a third order might be tricky even though I suspect its correct.

Black LS1 T/A

MellowYellow,

I'm sorry, that part of the answer got buried in all that info:

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">
I think (I could be wrong) the advertised boost is what they found the norm to be with, say, a stock vehicle and the 4.10" pulley (4.55 to 5 PSI) OR a modified vehicle and the 3.40" pulley (7 PSI) OR a HEAVILY modified vehicle and the 3.20" pulley (8 PSI).
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">So, the only "advertised" pullies I know of are:
4.55 - 5 PSI (4.1")
7 PSI (3.4")
8 PSI (3.2")

Since the time I got my Inventory Sheet with those listings, I've heard one guy say he got a 3.6" pulley. But, I don't know if that was a misprint or real.

Black LS1 T/A

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Mark C:
Its not linear. The relationship is at least second order, and probably third.</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I don't know that the curve you would derive from manipulating Differential Equations (which would be mathematically expensive) would give you enough of a deflection from the line to matter. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

I'm inclined to just interpolate between the sets of values, or draw a linear graph. It couldn't vary by much more than 1 PSI between pulley diameters of one inch, could it?

Still, it would be interesting to see you float an example. Could be fun. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

Rock

It also depends on which compressor you use...

highgmc

ati base kit here (FMU)
slp longtubes, no cats, wide open borla

4.10 pulley I got #2-3 boost

3.40 pulley I get #4.5 boost

I wonder which pulley I will need to get around #8 boost when I goto the GWP stage2?

Rock

Terry.. where you from dude... I'm from PA as well and have a similar setup. I get 5 psi from the 3.4 pully. I have the 3.2 in the basement. I'll let you know how it goes if you remind me in a few days.

Nickn20

pulley size doesnt have much to do with boost, you must know the impeller rpm speed of the blower, that way you can calculate some theoretical boost, then depending on the motor setup that will once again change, also altitude will affect it as well. it also matters where you shift at as well, since blowers are dependant on rpm.

Todd2001SS

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by terry99ta:
[QB]ati base kit here (FMU)
slp longtubes, no cats, wide open borla

4.10 pulley I got #2-3 boost

3.40 pulley I get #4.5 boost

</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Same kit, saw the exact same actual boost levels as above. The pulleys are not giving the boost they advertise.

I am happy though. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

MelloYellow

Right, let's say we're talking max boost at 6000-6400 rpm.

Might be best if we specify P1-SC or D1-SC.

Black LS1 T/A

Sea Level

D-1SC, Stock Internals, Stock Exhaust
-------------------------------------
4.10" Pulley
6000 - 6300 RPMs, 7 PSI

3.20" Pulley
6000 - 6600 RPMs, 12 PSI

D-1SC, Stock Internals, MAC Headers/Y-Pipe
------------------------------------------
3.20" Pulley
6000 - 6600 RPMs, 10 PSI

MelloYellow

Thanks! Maybe I should play devil's advocate 1 more time.

What pulley size comes with the ATI P1-SC 5# kit?
<img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

<small>[ June 04, 2002, 10:19 PM: Message edited by: MelloYellow ]</small>

Nickn20

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Black LS1 T/A:
<strong>Sea Level

D-1SC, Stock Internals, Stock Exhaust
-------------------------------------
4.10" Pulley
6000 - 6300 RPMs, 7 PSI

3.20" Pulley
6000 - 6600 RPMs, 12 PSI

D-1SC, Stock Internals, MAC Headers/Y-Pipe
------------------------------------------
3.20" Pulley
6000 - 6600 RPMs, 10 PSI</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">crank pulley will affect this as well, dont forget to mention those sizes, if they offer diff ones.... did you notice a boost drop when you did exhaust work?

Black LS1 T/A

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Nickn20:
crank pulley will affect this as well, dont forget to mention those sizes, if they offer diff ones.... did you notice a boost drop when you did exhaust work?</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I have the only crank pulley I know they current ship with the P-1SC and D-1SC (GWP is going to make a larger crank pulley available to me if my boost drops too much with the 422 stroker, but they don't think it will... I expect some lower boost). I don't recall the diameter of the crank pullies.

If you note my post, I say it went from 12 PSI to 10 PSI with exhaust work only (the MAC headers and Y-pipe/Cats). <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

highgmc

Rock,
I am located near uniontown, pa, (about an hour south of pitts)

The ati p1sc base kit comes with the 4.10 pulley.

As it is now, I am not very impressed with mine and feel I could get better et's from heads and a cam. ALTHOUGH I am hoping that when I goto the gwp stage 2 with proper tuning and fuel I will like it...

MelloYellow

Ah, k, recap..

As sold by ATI,
5# 4.10
7# 3.40
10# 3.20

and we aren't sure if there is a 3.60

I wish there was a 3.30 pulley.
Will ATI make them per request?

Black LS1 T/A

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MelloYellow:
<strong>Ah, k, recap..

As sold by ATI,
5# 4.10
7# 3.40
10# 3.20

and we aren't sure if there is a 3.60

I wish there was a 3.30 pulley.
Will ATI make them per request?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">3.20" pulley is rated as 8 PSI by ATI <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

scottywheels

i have the 3.2 pulley and see 6 psi. ati said that is supposed to be 7 psi for the p-1sc-h.