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Old 08-15-2012, 10:48 AM   #1
Bealracing
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Default Blown Alcohol Bracket Tuning Qs

Now for a tuning question, hang with me here….

We use the Les Davenport “Jetsize” program and love it. It tells me just about everything I ever wanted to know about my fuel system. (keeping pressures where we want them, lets you know what changing a nozzle does to the main pill, fuel pump changes made easy, etc.)

We’ve been running a new 990 enderle pump on our BAE deal. I have been in the 110-130 main pill range (~125 psi) with a fresh hi helix Kuhl 14.71 blower typically in the 40%-46% over range (~30 psi) (no pump loop or hi-speed). Our promod is a bracket deal where the whole class dial in is 7.00 seconds. We’ve been doing good with using density altitude as the main tracker for tuning. We’re getting so close in points that qualifying position points are starting to mean quite a bit.

Our problem runs into making a change that’s in between pill sizes. At the last race, the top 10 boats were between 7.000 to 7.009. Our tune from a .130 to a .131 was almost a whole hundredth. I’m considering running a pill in the pump loop to get my main down to around a .070 pill. This way, a .070 to a .071 main (area difference of .00011) is about half the change of going from a .130 to a .131 main (area difference of .00020).

Comments? Or is there another way to do this?
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Old 08-15-2012, 10:12 PM   #2
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Default Re: Blown Alcohol Bracket Tuning Qs

Quote:
Originally Posted by Bealracing View Post
Now for a tuning question, hang with me here….

We use the Les Davenport “Jetsize” program and love it. It tells me just about everything I ever wanted to know about my fuel system. (keeping pressures where we want them, lets you know what changing a nozzle does to the main pill, fuel pump changes made easy, etc.)

We’ve been running a new 990 enderle pump on our BAE deal. I have been in the 110-130 main pill range (~125 psi) with a fresh hi helix Kuhl 14.71 blower typically in the 40%-46% over range (~30 psi) (no pump loop or hi-speed). Our promod is a bracket deal where the whole class dial in is 7.00 seconds. We’ve been doing good with using density altitude as the main tracker for tuning. We’re getting so close in points that qualifying position points are starting to mean quite a bit.

Our problem runs into making a change that’s in between pill sizes. At the last race, the top 10 boats were between 7.000 to 7.009. Our tune from a .130 to a .131 was almost a whole hundredth. I’m considering running a pill in the pump loop to get my main down to around a .070 pill. This way, a .070 to a .071 main (area difference of .00011) is about half the change of going from a .130 to a .131 main (area difference of .00020).

Comments? Or is there another way to do this?
Drop down one pump size.
I also have the same pump and problem.

Jim
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Old 08-15-2012, 10:35 PM   #3
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Default Re: Blown Alcohol Bracket Tuning Qs

I carry a spare 990 and the one I'm running was new this year too. I'd rather stay with the new pumps I have. I can accomplish the same thing with a pump loop I believe. I don't think the 110 pump will quite produce enough or will be right on the edge of my fuel requirement for this hemi. Most in my class are running an 1100 so I may already be at the smallest pump I can run. I'm keeping my rpm low right now and only using 10 gpm at 7000 rpm. This is causing me to step on the blower harder. I'm about to change gears to run higher rpm (8000-8500) and will be in the 11-13 gpm range and can bring the overdrive down some.
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Old 08-16-2012, 07:08 AM   #4
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Default Re: Blown Alcohol Bracket Tuning Qs

You may want to check your area difference as a percentage.
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Old 08-24-2012, 07:39 PM   #5
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Default Re: Blown Alcohol Bracket Tuning Qs

Beal Racing,
This is from Ken Lowe's Fuel injection book. You can buy the complete book at his site http://www.kenlowe.com.au/LFS_book_intro.htm

"With fuel injection there is a relationship between the nozzles and the main jet. A balance should be maintained so the main jet size is between .100 and .125. If you go over or under this range the car will still operate but the changes in the main jet will not have the same size steps. This is usually not a problem in normally aspirated systems as the fuel volume in these systems is not as large as in supercharged systems. If the pump size is slightly large and the engine is "rich" with this range of main jets then you have a few options. Put on a smaller pump, put an under drive on the pump, or install a pump sizer. You should keep the main jet between .100 and .125. There are plenty of people racing that do not follow this guide line although I feel they would be a better tuner if they did. Get a calculator out and do the sums on jet size area do them all between .050 and .150 you will see the percentage difference in the steps every .001 under .100 and over .125 When you start to change sizes. you think you are making a change of a certain size but the actual change is a smaller or larger percentage than you think. Larger than a .125 and the return hoses have so much restriction in the flow the hose starts to act like a jet. I did a test on the flow bench to show a customer once and he had a .190 jet in his barrel valve. I ran the system with the .190 jet and then WITHOUT a jet. It ad the same flow numbers without the jet as it had with the jet in the barrel valve. The return hose was acting like a jet.

Look at the chart below to compare nozzle size changes in percentages.
--------------------------------------------------------------------------------
.125 main jet has .01227 sq in of area.
.124 main jet has .01208 sq in of area. This is a 1.55 % change.
--------------------------------------------------------------------------------
.100 main jet has .00785 sq in of area.
.101 main jet has .00801 sq in of area. This is a 2.04 % change.
--------------------------------------------------------------------------------
.060 main jet has .00283 sq in of area.
.061 main jet has .00292 sq in of area. This is a 3.18 % change.
A 3+ % change for a .001 jet change is too much for a main fuel system. It is OK for a secondary system like a high speed, pump sizer, enrichment or lean out valve. If the main jet is too large the idle return hoses will restrict the flow back to the tank and if the main jet is too small the changes are too large to make small steps in the tuning. I have always said that small main jets can cause tire shake because if you are very close to the correct fuel system for your combination and you make a .005 main jet change from .065 to .060 you are changing the fuel system. This is a 17.3 % change. Do you REALLY want to make a 17 percent change to your fuel system ? Even if you only change it .001 you are changing it 3.2 % and if you are "on the edge" this might step you over. Lean cars on good tracks shake. Lean cars on loose tracks might be able to spin the tires and get past the shake.
"
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Old 08-24-2012, 07:46 PM   #6
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Default Re: Blown Alcohol Bracket Tuning Qs

This is from ken Lowe's Fuel Injection book.
" Main jet: The main jet is a removable drilled orifice he main jet sends some of the fuel back to the tank. The fuel pump supplies 100% of the fuel. If 70% of the fuel goes to the engine via nozzles then 30% goes back to the tank via the main jet. This allows the engine tuner to make one change and completely recurve the fuel delivery to the engine. This is different than carburetors where you have to change all the main jets to completely recurve the fuel system to allow for weather or other changes With fuel injection the nozzles only set the fuel pressure in the system. With fuel injection there is a relationship between the nozzles and the main jet. A balance should be maintained so the main jet size is between .100 and .125. If you go over or under this range the car will still operate but the changes in the main jet will not have the same size steps. This is usually not a problem in normally aspirated systems as the fuel volume in these systems is not as large as in supercharged systems. If the pump size is slightly large and the engine is "rich" with this range of main jets then you have a few options. Put on a smaller pump, put an under drive on the pump, or install a pump sizer. You should keep the main jet between .100 and .125. There are plenty of people racing that do not follow this guide line although I feel they would be a better tuner if they did. Get a calculator out and do the sums on jet size area do them all between .050 and .150 you will see the percentage difference in the steps every .001 under .100 and over .125 When you start to change sizes. you think you are making a change of a certain size but the actual change is a smaller or larger percentage than you think. Larger than a .125 and the return hoses have so much restriction in the flow the hose starts to act like a jet. I did a test on the flow bench to show a customer once and he had a .190 jet in his barrel valve. I ran the system with the .190 jet and then WITHOUT a jet. It ad the same flow numbers without the jet as it had with the jet in the barrel valve. The return hose was acting like a jet.

Look at the chart below to compare nozzle size changes in percentages.
--------------------------------------------------------------------------------
.125 main jet has .01227 sq in of area.
.124 main jet has .01208 sq in of area. This is a 1.55 % change.
--------------------------------------------------------------------------------
.100 main jet has .00785 sq in of area.
.101 main jet has .00801 sq in of area. This is a 2.04 % change.
--------------------------------------------------------------------------------
.060 main jet has .00283 sq in of area.
.061 main jet has .00292 sq in of area. This is a 3.18 % change.
A 3+ % change for a .001 jet change is too much for a main fuel system. It is OK for a secondary system like a high speed, pump sizer, enrichment or lean out valve. If the main jet is too large the idle return hoses will restrict the flow back to the tank and if the main jet is too small the changes are too large to make small steps in the tuning. I have always said that small main jets can cause tire shake because if you are very close to the correct fuel system for your combination and you make a .005 main jet change from .065 to .060 you are changing the fuel system. This is a 17.3 % change. Do you REALLY want to make a 17 percent change to your fuel system ? Even if you only change it .001 you are changing it 3.2 % and if you are "on the edge" this might step you over. Lean cars on good tracks shake. Lean cars on loose tracks might be able to spin the tires and get past the shake."
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Old 08-24-2012, 10:50 PM   #7
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Default Re: Blown Alcohol Bracket Tuning Qs

Quote:
Originally Posted by Rob Kozak View Post
This is from ken Lowe's Fuel Injection book.
" Main jet: The main jet is a removable drilled orifice he main jet sends some of the fuel back to the tank. The fuel pump supplies 100% of the fuel. If 70% of the fuel goes to the engine via nozzles then 30% goes back to the tank via the main jet. This allows the engine tuner to make one change and completely recurve the fuel delivery to the engine. This is different than carburetors where you have to change all the main jets to completely recurve the fuel system to allow for weather or other changes With fuel injection the nozzles only set the fuel pressure in the system. With fuel injection there is a relationship between the nozzles and the main jet. A balance should be maintained so the main jet size is between .100 and .125. If you go over or under this range the car will still operate but the changes in the main jet will not have the same size steps. This is usually not a problem in normally aspirated systems as the fuel volume in these systems is not as large as in supercharged systems. If the pump size is slightly large and the engine is "rich" with this range of main jets then you have a few options. Put on a smaller pump, put an under drive on the pump, or install a pump sizer. You should keep the main jet between .100 and .125. There are plenty of people racing that do not follow this guide line although I feel they would be a better tuner if they did. Get a calculator out and do the sums on jet size area do them all between .050 and .150 you will see the percentage difference in the steps every .001 under .100 and over .125 When you start to change sizes. you think you are making a change of a certain size but the actual change is a smaller or larger percentage than you think. Larger than a .125 and the return hoses have so much restriction in the flow the hose starts to act like a jet. I did a test on the flow bench to show a customer once and he had a .190 jet in his barrel valve. I ran the system with the .190 jet and then WITHOUT a jet. It ad the same flow numbers without the jet as it had with the jet in the barrel valve. The return hose was acting like a jet.

Look at the chart below to compare nozzle size changes in percentages.
--------------------------------------------------------------------------------
.125 main jet has .01227 sq in of area.
.124 main jet has .01208 sq in of area. This is a 1.55 % change.
--------------------------------------------------------------------------------
.100 main jet has .00785 sq in of area.
.101 main jet has .00801 sq in of area. This is a 2.04 % change.
--------------------------------------------------------------------------------
.060 main jet has .00283 sq in of area.
.061 main jet has .00292 sq in of area. This is a 3.18 % change.
A 3+ % change for a .001 jet change is too much for a main fuel system. It is OK for a secondary system like a high speed, pump sizer, enrichment or lean out valve. If the main jet is too large the idle return hoses will restrict the flow back to the tank and if the main jet is too small the changes are too large to make small steps in the tuning. I have always said that small main jets can cause tire shake because if you are very close to the correct fuel system for your combination and you make a .005 main jet change from .065 to .060 you are changing the fuel system. This is a 17.3 % change. Do you REALLY want to make a 17 percent change to your fuel system ? Even if you only change it .001 you are changing it 3.2 % and if you are "on the edge" this might step you over. Lean cars on good tracks shake. Lean cars on loose tracks might be able to spin the tires and get past the shake."

Rob is smart )))))
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Old 08-27-2012, 10:09 AM   #8
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Default Re: Blown Alcohol Bracket Tuning Qs

Thats the main reason for running a pump loop is to get the main jet size down. Then each jet change will be a "finer" adjustment. You make a jet change when you go from .130 to .131 and its a large change. Just figure out your jet area, change your loop jet and get your main jet down to a smaller size.
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Old 08-27-2012, 11:31 AM   #9
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Default Re: Blown Alcohol Bracket Tuning Qs

Comax, that is what I was thinking as well. I was just checking to see what other options were out there.
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Old 08-27-2012, 03:55 PM   #10
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Default Re: Blown Alcohol Bracket Tuning Qs

Maybe give Davenports a call and see what they have to say.
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Old 08-28-2012, 09:26 PM   #11
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Default Re: Blown Alcohol Bracket Tuning Qs

Jetsize is great,,, call Sean 403-938-6200
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Old 08-28-2012, 09:28 PM   #12
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Default Re: Blown Alcohol Bracket Tuning Qs

Yep, we've been using it for years. Definitely a great tool.
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Old 09-07-2012, 02:07 PM   #13
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Default Re: Blown Alcohol Bracket Tuning Qs

OK, new question....... We're in the points hunt with the LUCAS OIL series. To stay in the hunt we're forced to head to San Diego to their Bayfair Nationals next weekend the 14-16th. We generally run in around 4,000+ ft of density altitude. The weather there is trending toward cool... I'm estimating 1,000 ft of DA of which we have never run. With that big of a change, how do you guys dial yours back and be close? I can shoot from the hip and say 30% over and take about 20 out of the main, but am curious if there's a better way without having run in that air before......

Here is my setup from the first post on this thread......We’ve been running a new 990 enderle pump on our BAE deal. I have been in the 110-130 main pill range (~125 psi) with a fresh hi helix Kuhl 14.71 blower typically in the 40%-46% over range (~30 psi boost). Our promod is a bracket deal where the whole class dial in is 7.00 seconds.
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Old 09-07-2012, 02:17 PM   #14
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Default Re: Blown Alcohol Bracket Tuning Qs

G00D Luck,.................!
Later
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Old 09-07-2012, 02:20 PM   #15
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Default Re: Blown Alcohol Bracket Tuning Qs

Thanks, I'll need it!
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