Fuel System - gas and alcohol

Old 08-30-2007, 07:53 AM
  #11  
davis419b
Senior Member
EXPERT BUILDER
 
Join Date: Jul 2005
Location: Wylie,Texas
Posts: 276
Default

Wait a minute, Bigger engine pulling more air with more velocity but less fuel, that does not make any sense to me and I have been running alcohol for 15 years.

Tom, Do you run a smaller jet than the guys with smaller engines?
davis419b is offline  
Old 08-30-2007, 08:11 AM
  #12  
davis419b
Senior Member
EXPERT BUILDER
 
Join Date: Jul 2005
Location: Wylie,Texas
Posts: 276
Default

George, What size pump do you run?
davis419b is offline  
Old 08-30-2007, 08:47 AM
  #13  
gdmii
Senior Member
MASTER BUILDER
 
Join Date: Oct 2004
Location: Newport News, VA
Posts: 139
Default

Originally Posted by davis419b
Wait a minute, Bigger engine pulling more air with more velocity but less fuel
Nope, I didn't say less fuel. I said less jet. I'll see if I can explain it a little better. Let's say you and I both have 1150s, your 565 and my 496, and we both have 165 jets installed. If you're right on then I will probably be lean. Since you are pulling more air than I am you are pulling more fuel through that 165 jet than I will be able to. Since I can't increase the airflow through my carb my options are to increase the jet size or go to a smaller carb to get the velocity of the air up. Air velocity through a venturi is suction. The more suction you have, the greater the pressure differential, and the more fuel you can pull through a given restriction, in this case the 165 jet. I don't have the velocity so I need less restriction, i.e., a larger jet.

BTW, I'm running a BG400 pump.

George
gdmii is offline  
Old 08-30-2007, 08:58 AM
  #14  
davis419b
Senior Member
EXPERT BUILDER
 
Join Date: Jul 2005
Location: Wylie,Texas
Posts: 276
Default

I would be more inclined to believe that with an electic fuel pump you need a bigger jet for more volume due to the lack of volume the pump delievers. Have you ever ran a mechanical pump with your set-up. Years ago i bought an alcohol carb from Barely Grant. I had a Barry Grant pump and they told me it wouldnt work and they were right. Have had a mechanical pump every since. I do not believe you need that bid of jet with an Enderle pump.

Zipper, where are you i need you to jump in here !!
davis419b is offline  
Old 08-30-2007, 09:48 AM
  #15  
curtisreed
Senior Member
RACING JUNKIE
 
curtisreed's Avatar
 
Join Date: Feb 2004
Location: KIEFER, OK.
Posts: 1,312
Default

I can tell you that what George is saying is the exact thing I am going through right now. We have an older Rupert 950 that we had on a 468. It had 165 jets in it, I put it on my 383 that is a lot milder motor that the 468 and have had to go up to 173 jets, went quicker and faster than with the 165s, and I am going to go up even more the next time out. I am using an electric pump also. The one thing that I will have to watch with an electric pump is emptying the bowls faster that the needles will let fuel in with the bigger jets because I can't raise pressure with rpm like a mechanical pump, even though that is probably the better way to go.

Curtis
curtisreed is offline  
Old 08-30-2007, 09:57 AM
  #16  
davis419b
Senior Member
EXPERT BUILDER
 
Join Date: Jul 2005
Location: Wylie,Texas
Posts: 276
Default

I rest my case! Find me someone who is running that big of jet with a belt drive pump, you wont. The guy in question here is running a belt drive pump. If you run the right fuel system you wont need all that fuel pressure bleed off crap, just set the fuel pressure and go!!
davis419b is offline  
Old 08-30-2007, 10:36 AM
  #17  
zipper06
Senior Member
RACING JUNKIE
 
Join Date: Jan 2006
Location: La.
Posts: 2,890
Default

Originally Posted by davis419b
I would be more inclined to believe that with an electic fuel pump you need a bigger jet for more volume due to the lack of volume the pump delievers. Have you ever ran a mechanical pump with your set-up. Years ago i bought an alcohol carb from Barely Grant. I had a Barry Grant pump and they told me it wouldnt work and they were right. Have had a mechanical pump every since. I do not believe you need that bid of jet with an Enderle pump.

Zipper, where are you i need you to jump in here !!
Sorry i'm not alcohol carberator person, but i am a firm believer in front mounted mechanical pumps. My car is setup both for gas and alcohol. I have an 8 gal fuel cell in the trunk and 2 holly blues, and a 1/2" feed line, regulated at 8lbs. I also have a 3gal. cell in the front for alcohol running the toilet bowl with a DSR mechanical pump. If i were to put an alky carb on i would use the mechanical pump and regulate it with an 8lbs bypass off a fuel log/tee. 1 line out of the pump 1 line back to the tank. Real simple setup and cost effective, and you will never run out of fuel in the carb.


just my .02

Zip.
zipper06 is offline  
Old 08-30-2007, 11:14 AM
  #18  
gdmii
Senior Member
MASTER BUILDER
 
Join Date: Oct 2004
Location: Newport News, VA
Posts: 139
Default

Originally Posted by davis419b
I would be more inclined to believe that with an electic fuel pump you need a bigger jet for more volume due to the lack of volume the pump delievers.
Obviously the pump, whether electric or belt driven, needs to be sized correctly but in your statement above if a pump lacks the needed volume adding a larger jet for even more volume would only exacerbate the problem. Electric pumps work fine if the pump is big enough. That's all I have run. I do have the PCI bowls on my carb so supply is not a problem.

Curtis, you are going in the right direction.

George
gdmii is offline  
Old 08-30-2007, 11:31 AM
  #19  
davis419b
Senior Member
EXPERT BUILDER
 
Join Date: Jul 2005
Location: Wylie,Texas
Posts: 276
Default

I dont care what masterbates the problem its all about electric verses belt drive pumps. You are sending JP in the wrond direction!
davis419b is offline  
Old 08-30-2007, 11:38 AM
  #20  
gdmii
Senior Member
MASTER BUILDER
 
Join Date: Oct 2004
Location: Newport News, VA
Posts: 139
Default

The guy in my post above that had 209 jets installed is using a belt driven pump. I didn't invent physics I just have to apply them like everyone else. I don't intend on getting into a pizzing contest on which pump is better. Different type pumps require different setups. Like I said in my original post, it works for me. If it doesn't work for you that's fine, too. And I'll let it rest with that.

George
gdmii is offline  

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service