Boost Calculation and Tuning the 5.0 for Boost with Kenne Bell's Wisdom = 68 HP gain with 4lbs of Boost!!!!! | Ford Explorer - Ford Ranger Forums - Serious Explorations
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Boost Calculation and Tuning the 5.0 for Boost with Kenne Bell's Wisdom = 68 HP gain with 4lbs of Boost!!!!!

Blown

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I ran a large pulley to get it running safe and thought it time to maybe run my smaller pulley to get more boost. The calculations with the info. here from Kenne Bell gave me the confidence to run the smaller pulley for winter.

((14.7air pressure psi+ Boost in psi)/14.7 air pressure) X (engine liters/2)/2.2 supercharger in liters=Theoretical Pulley Ratio at sea level

14.7 is the air pressure at sea level. I live in Colorado. I found a chart and the air pressure here is 12.0psi at 5,500' altitude. That makes a huge difference for you flat landers out there. The supercharger was a big innovation in WWII to boost aircraft power at altitude. The opposite is true, think about dropping to sea level, one could blow-up a supercharged rig tuned for high altitude! The calculation for my rig reveals 10.3lbs of boost at sea level with the 2 3/8" pulley, a bit too much without more octane or intercooler! The boost gauge concurs with the calcs at 5,500'.

I run an F150/Bronco crank pulley at 6.5". I have a 4" pulley and a 3 3/8" pulley, ratio's are 1.63:1 and 193:1. I revisited the pulley/boost calculation over the weekend, Went through Kenne Bell's tuning stuff, put on the smaller pulley, tuned and gained 4lbs of boost! I am able to do so because of the altitude and cooler temps. According to Kenne Bell, 1lb of boost increase is 17-20 horsepower or 68 to 80 horses with an additional 4 pound of boost!!! It is noticeable!
Calculations:

Sea level ((14.7+10.3)/14.7))X(5/2)/2.2= 1.93
5,500' ((12psi +8.4lbs boost)/12)X5/2)/2.2= 1.93

Kenne Bell stuff from here: Jim Bell's Supercharged / Turbocharged Performance Guide | Kenne Bell
KB stuff:
1 psi boost requires 1.5 octane (minimum) 1 psi boost = .5 point CR (effective CR)
1 AF ratio = 2 octane (example 12.5:1 to 11.5:1)
1° advance = 1/2 – 3/4 octane point
20° ambient = 1 octane
10° engine coolant (160° -180° range) = 1 octane
1000′ altitude = .5 psi (2″ Hg)

I used the above from KB to check my tune by octane. There are other variables to consider if tuning for a set time and conditions in the Kenne Bell info. One assumption is that you are already using premium unleaded.

At 5,500' 8.4lbs of boost X 1.5 Octane = 12.6 points increase in octane required.

5,500' elevation X .5psi = 5.5X.5= 2.75 octane points
1.3 increase air fuel ratio from stock X 2 = 2.6 octane points
Winter Temps 20 degrees = 1 octane point
12 degrees spark retard X .625 octane = 5 (I split the difference between .5 to .75)

12.6 - 2.75 - 2.6 - 1 - 7.5 = -1.25 octane points = A good tune for here, but if I drive it down in altitude.............or the temps go up.........yikes!

I think I can make this pulley work. I am going to put a cooler thermostat in it and may build an intercooler later. The following lines from KB shows how this would help.
10° engine coolant (160° -180° range) = 1 octane
20° charge temp reduction through intercooling = .5 psi additional boost with same octane
 



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Blown

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I have refined my numbers some, probably not quite 4lbs gained but close. A screen shot of my spreadsheet is below and below that a paste of Kenne Bell's stuff. There are more variables than what are in my spreadsheet, those are out of our control like altitude and weather/air conditions. There needs to be a safety margin for condition changes. I suppose I could add all variables and this could be used to check your tune for the specific conditions on race day. You could tune for max power for the moment, but would risk pre-detonation in a daily driver as conditions change. I got a 2 octane margin of safety at 5,500'. That 2 octane margin could easily be needed in 100 degree summer temps.

tuning-spreadsheet.jpg


JIM BELL’S​

PERFORMANCE GUIDE​

This data is intended as a guide to proven common sense performance. It’s the result of 50 years of experience and thousands of dyno runs, street and competition testing with our company and customers vehicles.
1 psi inlet loss restriction = -30HP
1 psi boost requires 1.5 octane (minimum) 1 psi boost = .5 point CR (effective CR)
1 point CR = 2 psi boost (CYLINDER PRESSURE) 1 point CR = 2% HP
1 psi boost = 17-20HP after kit is installed 1 point CR = 3 – 5 octane
1 AF ratio = 2 octane
1° advance = 1/2 – 3/4 octane point
10° engine coolant (160° -180° range) = 1 octane
20° ambient = 1 octane
7oz can Lucas octane booster in 20 gal = 1.5 octane Typical +100° underhood filter loses 10% in HP 1000′ altitude = -1 octane point
1000′ altitude = .5 psi (2″ Hg)
6°F temp change = 1% air density 30% humidity = 1 octane
10° air charge temperature = 1% HP
20° charge temp reduction through intercooling = .5 psi additional boost with same octane
 






Blown

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I can use the 3 3/8" pulley for Colorado winters, but It will be too much other times of the year or if I drive down in altitude. I ordered a 3 11/16" pulley from Kenne Bell. I am running an old Kenne Bell from the early 90's so was lucky they had one. The only other size they had was 3.5"

Here's an additional formula from Kenne Bell:
Theoretical Boost =(Supercharger size X Pulley ratio)/(engine size/2) X 14.7 – 14.7 (14.7 = air pressure at sea level.)


Supercharger pulley 3 11/16" = 3.6875" Crank Pulley 6.5" 6.5/3.6875= 1.76:1 Pulley Ratio

(2.2X1.76)/(5/2)X12-12= 6.6lbs. (12.0 air pressure at 5,500')

(2.2X1.76)/(5/2)X14.7-14.7= 8.0lbs (14.7 air pressure at sea level )

That should keep it safe!
 






CDW6212R

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Interesting. I've got to do the math with a stock 6" crank pulley, so a 3.25" blower pulley should get me 9psi, by that formula. I've got a 7" crank pulley to use with a different balancer, so that ends up being 3" I'd need, to reach 12psi.
 






Blown

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I am tuning by octane with KB's experience. I am leaving a 2 octane margin in my tune for temperature increases in summer, 40 degrees equals 2 octane and that just a hot summer day. I'd like more boost but that is not happening without additional cooling with an intercooler or meth injection.
I am going to keep it simple, for now, at 6.6lbs,at 5,500'. I have written one tune for 5,500' elevation and one with less timing and more fuel to switch to on the fly when it's very hot or I drive down in altitude.

The hood would need a scoop to fit a decent size intercooler under the blower. I would get to make a custom intercooler. I won't hassle with meth injection for a daily driver, been there, done that and the additional tank to fill, plus trip to Bandimere dragway for meth, and then the big "if" as in if you run out of meth you could blow an engine. The engine is in boost for longer periods when climbing around Colorado and it used more meth.

The thing is, I am getting ahead of myself and would need to upgrade the t-case before adding more boost. I am not in a position to want to do all that now and need to just enjoy it for a while after all the build time...........................that said, I can run the 3 3/8" pulley for ***** and grin in the winter. I have seen up to 9lbs on the boost gauge on a cold morning with the 3 3/8" pulley!!!! Fun, but what will break???? That is around 150 to 180 additional horses over stock!
 






CDW6212R

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That 9psi level is a good limit for the non forged pistons, and that is just getting into higher IAT's there. I'm going to mount the blower to the side and run the output down into an IC plenum right on top of the lower intake.

You've seen Tim's Sport, he gutted a carb type intake and found space there for an IC, with the blower above it. That might be the best way depending on the IAT's and how big the IC is, or needs to be. I can make it fairly big, and hopefully there will be room behind it, for the inlet plenum to go along the firewall.
 






Blown

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Quote:" You've seen Tim's Sport, he gutted a carb type intake and found space there for an IC, with the blower above it. That might be the best way depending on the IAT's and how big the IC is, or needs to be. I can make it fairly big, and hopefully there will be room behind it, for the inlet plenum to go along the firewall."

Don, sounds like an interesting mount of the supercharger and it will make intercooling easier. Based on those I have seen in my searching , the heat exchanger in the intercooler needs to be pretty thick. I looked a bit closer at where the blower sits in the engine bay. A simple hood scoop won't make the room I need to put an intercooler under the blower. I could make room with a body lift or would need to side mount like you are proposing. Fun stuff, but it's not likely I'll do it. Ha, I can watch yours!


I got and installed the 3 11/16" pulley. Hmmm, I never measured it. I am seeing about 7lbs of boost and I like it! I got some additional tuning to complete, she's showing rich at high load/boost...........much better than the alternative, but I should be able to tune it out and having difficulties doing so. I am getting support from Tweecer.

I think I will be happy with what I got now................................I think I am more likely to build-up a Fox body for fun and speed.


Oh, running the 180 degree thermostat has helped lower IAT's as well as ECT.
The tuning stuff I put here and mostly from kenne Bell is conservative. I am running more timing, but I believe utilizing his stuff is a safe place to start!
 






CDW6212R

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Very good. That's how I see doing it the best way, safely to begin with and get things working right before stepping on it. I'm going to fab the blower plenum parts to go on my stock engine first, then when it's sorted out, swap the engine last. I have a TFS "R" lower intake to build on, those are the shortest lower intake, and have large ports. I've read those can flow 340cfm ported, whereas the GT40 is hard to get over 275cfm.

Keep driving it, have fun during Winter before moving on to another project, or upgrade.
 






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