Fuel System Question?

Ok Im Going To Show My Stupidy Now. If You Have A Fuel System And Was Told Its A 1/2 Gal Rich How Do You Figure How Much Fuel To Take Out (i Know A 1/2 Gal)where Do You Take It From Main, Hi Speed, Nozzle Jets?. Is There A Formula To Figure This Out. Is There A Computer Program To Help With Your Tune Up Given The Atmosphere Conditions For Blown Alky Where Do I Find One?how Do You Figure How Much Fuel A Engine Needs If You Have A New Combo I Know You Need To Get It Flowed But What Determines The Amount Of Fuel How Do You Figure This? Just Thought I Would Ask I'm Learning So Go Easy On Me Thanks

 

It's very simple. If you have an area chart, you look to see what size nozzle flows approximatley 1/2 gallon. That nozzle will have a certain amount of area. Divide that nozzle (area) by 8 then remove that much area from each port nozzle. The formula is simple: nozzle size x nozzle size x .7854 (example .065 x .065 x .7854 = .0033183), then divide .0033183 by 8 which equals .0004147. Remove this much area from each port nozzle. You now require a .061 nozzle. This is as close as you will get. I have an area chart I can e-mail you if you would like. Send me your e-mail address and I will send it to you.

 

Thanks For The Reply That Tells Me How To Figure What Amout To Remove. Now How Do You Figure How Much Fuel You Need On A New Combo Such As Going From Just Running Hat Nozzles To Running Hat And Port Nozzles I Going To Have Jim Oddy Flow My Fuel System But I Want To Know These Things For Myself As I Get Further Into This Project So Maybe I Can Figure This Out For Myself Or Help Others As People On This Site Have Helped Me I Have Read Many Post On Here And Know There Are A Lot Of Very Smart People Out There I Would Just Would Like To Know How Things Work Or I Will Never Figure The Fuel Systems I Have The Basics Down Just Want To Learn The Tuning Side I Know It Will Come In Time Just Need A Helping Hand And A Little Guideance Thanks

 

Ok, you can reduce nozzle area,but when you do you change system pressure also. As far as im concerned, the system pressure needs to be maintained in order to not change the fuel curve. I would rather have a pump loop involved so that the nozzle area doesnt get too crazy and its easier to maintain system pressure.
Example: 526 roots deal,22.51 gpm pump flow,13.33 gpm system. Without loop hat area is .01791,port .02112 with an .080 hi speed at 68 lbs. System pressure is 143 lbs with a .174 main. -.5 gpm would be 12.83 gpm. Lets see what reducing the port area alone would do.reduced 13% for 12.83 gpm.Now system pressure is at 151.The olnly way to reduce that pressure is to put in a pump loop which is a line above and below the shutoff with a check valve and a jet and increase the nozzle area to get back to 143 lbs and fiddle with the main. Increased nozzle area by 3% to 10% reduction and put in a .050 loop at 50 lbs along with increasing the main to .172.Bingo,but that is a pretty large main.
If i had a loop in it in the first place in order to reduce the main down to something more reasonable it would look like this.
Same hat and port area to start. Loop at .142@40 lbs for a .115 main@13.33 gpm and 143 system pressure. Going for -.5 gpm.Reduced nozzle area by 6% and increased loop to .150 and am able to keep same main for a system pressure of 142 lbs. Now my hi speed will pop off at the same rpm and the fuel curve is still the same but i reduce the gallonage by .5.

 

Thanks Leon How Are You Figureing This Do You Use A Program Or? Jamie

 

If you post or send your e/mail address Leon or myself can send you some programs to help figure this out for you.

Bob Kraemer

 

I'LL TAKE WHATEVER HELP I CAN GET THANKS JAMIE FUNNYCARGUY@NETZERO.COM

 

Bob Kraemra .

I would really appreciate the program that you offered funnycar guy. I am also struggling in this area so your help would be appreciated.

my email is ftch@bigpond.com

kind regards
MJM

 

Bob Kraemer,
I could really use some help in this area also, if you woudn't mind e-mailing me the programs too. Thank you in advance. My e-mail is
rkay01@sbcglobal.net

 

Boy Bob, Im sure glad your so popular.HOw much are you charging?LOL

 

I have a car very similiar to yours. 510" chevy, dart 360, 110 pump, regular 8-71 at 42%. Makes 20-22lbs at 6000rpm in lights on 1/8th mile. Runs 4.60 at 153 consistently. I have an old mallory mag 3 at about 34 deg. Having someone set it up is obviously the best idea, but if your not going to do that maybe I can be somewhat helpfull. The biggest main jet we've ever put in is a 135, and that was in August in Oklahoma. My base is 120 main at 3000ft corrected alt. moving up or down 5 per 500' change. What kind of boost your making. We had a problem with being too fat when we first got the car. We had an 80(or so) main, and it was shooting fire out of the headers all the way down the track. We leaned out 10 per run and got to the base we are now at.

Your car should need significantly more fuel than mine, and if it's not showing signs of being way fat, firing out the exhaust, blowing raw fuel, it's probably way too lean.

When my dad got his first funny car, they spent the entire first year and couldn't make it run very good, so they kept leaning it out, never hurting anything. At some point during the season they decide to ask for help, so they get another, experienced racer to come over and look at their stuff. He then suggests a main jet, significatly fatter. That run they make the quickest and fattest run of the year, while also kicking a couple of rods. It's always sounded weird, but we have first hand knowledge of being to far on the "backside".

This is also another reason to have a pro set it up. If you start fattening up at a slow pace, at some point you could get close to the edge (coming the other way), and possibly do some serious damage. If not, I'd probably start at around a 100 main and work from there.

sorry for the ramble

bryan brown

 

Hey Bob, I think you may have tried to send me your fuel info, nut my inbox was full. I've cleaned it out. Can you send it again. Thanks

 

Please help

Leon, can you please help me....I would love to have a copy if there is any charge let me know. also I see you live in kansas and so do I. I live in pittsburg ks. small world...need help. Dave I run a 526 14-71 hi helix if you need more info. let me know

 

leon e-mail me

secondwindracing2000@yahoo.com

 

bryan brown,

I just wanted to confer with you and your Oklahoma Base is it at ThunderValley or Tulsa? I live in Mustang, Oklahoma
I have 509 BBC, Brodix BB3 heads, 110 pump, 85 psi pump press, 14-71 hi helix 20% over and run 29 psi boost MSD 12 amp mag 32 deg timing with only hat nossels 2-52 and 10-45. My base is set on 2300 density alt and is for 6.80 tune at 205 with a 160 main no high speeds or anything else in the system. I find it takes 500 to 750 foot change before i notice a change in ET even if the computer tells me to change it at a lessor Alt. I find that even if I add boost or timing it will not go any faster it crosses at 8300 Rpm. I think the tune is soft but I may be worng. Oddy said I was luggin the motor and to twist it tighter and add .025 more fuel to it and hang on. I am not real sure about that. Just was woundering why your base is @ 3000 Den Alt. I thought you took you best two or three consistant passes and use them in your computer to set you baseline. that is what I have done is this right? Thanks