Larger Whipple Math


T

TrackDay

GT Owner
Mar 20, 2006
128
a) First question.
Larger of the two Whipple pulleys delivering around 18 - 18.5 psi of boost + piston compression = what final compression ratio?

Mind you this is the tamer of the two pulleys the smaller one delivers around 21 psi!
 
I don't think so.... why don't you ask Dustin Whipple.
Bony - BIG WHIPPLE owner
 
Track day is right.

Mine is on dyno as we speak.It all comes down to fuel.If you do go with high
boost fuel and driveablty become an issue.
 
GFORCE said:
If you do go with high
boost fuel and driveablty become an issue.
Click to expand...

Fuel maybe, driveablilty, not sure about that......:biggrin
 
methanol injection in an inexpensive kit such as snow performance could easily take care of the issue, or e85 would work also
 
GFORCE said:
Mine is on dyno as we speak.It all comes down to fuel.If you do go with high
boost fuel and driveablty become an issue.
Click to expand...

Please post your results, size of pulley and what gas you tuned for.
I show'd mine, now lets see yours:lol :rofl :lol
 
The boost you will see depends on the other mods you have done. For example, I believe the 3.625" pulley will yield around 18-19lbs boost on a car with an upgraded, free flowing exhaust, TB, filters, etc..
 
Now rumor has it (a good one I might add) that during the tuning session a number seen was in the 720 range….. now I do not know if once completed, when the tuning began, or simply one of the numbers during the process.

Regardless from what I heard she like the bigger pump.

All the best

Shadowman
 
The question remains

If the tamer pulley pumps 18-19 psi what is the resulting cylinder compression ratio?
 
 
Thanks for the link!
Final compression ratio = [ (boost/14.7) + 1 ] x engine compression ratio
Ok so someone check my math (at sea level)
GT motor adds compression of 8:1
Larger Whipple with lower compression pulley = 18.5 psi
[ (18.5 / 14.5) + 1 ] x 8.4
= final compression ration of 19 : 1

Last question to follow.
 
Last edited:
It looks to me like your answer is correct, but the numbers may need a little clarification. From the equation on the previous thread:
Final compression ratio = [(boost/14.7 + 1] x standard or static compression ratio.
Boost is in lbs/sq in (or psi).
14.7 = lbs/sq in, or psi, of one atmosphere at sea level.
8.4: 1 = standard compression ratio for Ford GT motor.
So, at 18.5 psi boost on the larger Whipple, the final compression ratio =
[(18.5/14.7) + 1] x 8.4 =
(1.26 + 1) x 8.4 =
2.26 x 8.4 = 18.97.

Or, a final compression ratio of about 19:1, as you said.
 
Last question:
So anyone using the larger Whipple basically could only run safely on race fuel at full boost?
Or take their chances that 91-93 octane and a bottle of octane boost might still result in large repair bills.
 
TrackDay said:
Last question:
So anyone using the larger Whipple basically could only run safely on race fuel at full boost?
Or take their chances that 91-93 octane and a bottle of octane boost might still result in large repair bills.
Click to expand...

No sir, I am tuned for 91 California pump gas... Giant 3.75" old lady's pulley installed. Requires proof a membership in Republican party and documented proof of donations to conservative canadates.
 
Help with figuring cfm at different rpm would be appreciated.
 
If you know boost pressure, you can use this to get an estimate...
http://www.modularfords.com/forums/...alculator-for-a-4-stroke-ic-engine-64994.html
You'll need to modify some of the variables, but hopefully they will be obvious.

It can also be calculated directly knowing the pulley ratio, supercharger displacement, and the supercharger's VE. (Any restriction within the inlet track can also be included, if it is known.)
 
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Black2003Cobra said:
If you know boost pressure, you can use this to get an estimate...
http://www.modularfords.com/forums/...alculator-for-a-4-stroke-ic-engine-64994.html
You'll need to modify some of the variables, but hopefully they will be obvious.

It can also be calculated directly knowing the pulley ratio, engine & supercharger displacement, and ethe ngine & supercharger's VE's. (Any restriction within the inlet track can also be included, if it is known.)
Click to expand...

Black Cobra

About 6 posts above yours they calculated the numbers and the formula is there.

Dave
 
barondw said:
Black Cobra

About 6 posts above yours they calculated the numbers and the formula is there.

Dave
Click to expand...
I was addressing californiacuda's question about calculating the volumetric-flow rate.
 
so how much timing are you guys running at 19 psi of boost and what kind of spark plugs are you runnin?
 
Fast Freddy said:
so how much timing are you guys running at 19 psi of boost and what kind of spark plugs are you runnin?
Click to expand...

Freddy I updated my dyno run post so you can see the timing as well as other information. The timing was set to 20* in the tune, but due to the air temps it was really 19.5*. I have since lower it to 18* for a larger safety margin. Plugs are NGK TR7IX gapped to 0.028".

http://www.fordgtforum.com/forums/showpost.php?p=90206&postcount=31
 
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