SpeedTalk Store - Opinion Columns

max fuel pressure w/holley? tried 18 psi, got it to work

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Re: max fuel pressure w/holley? tried 18 psi, got it to work

Postby Matt Gruber » Sat Apr 10, 2010 6:06 am

R.Olds wrote:
The self regulated Carters are total junk, I have seen a dozen in the last year that did not work as advertised,. pressures from 2 psi to 16 psi, and never consistant. Now I use the non regulated Carters with seperate regulator.

Rick

So, i fixed the 18, down to 6 now, with a power resistor in series.
A budget turbo could use something similar, and when on boost, the power resistor would be bypassed, say, once it hits 3 psi boost.
.
.
tame a lumpy cam for the street, more street hp, 14.5-18 mpg around town (was 11-14) with a fully divided dual plane, see my site:
http://community-2.webtv.net/mattgru/carb/
drive off cold 1200 rpm no stall
Matt Gruber
Guru
Guru
 
Posts: 1617
Joined: Fri Mar 19, 2010 6:32 am
Location: near Daytona Beach FL

Re: max fuel pressure w/holley? tried 18 psi, got it to work

Postby F1Fever » Sat Apr 10, 2010 6:12 am

obviously ..... the questio here is not about how many psi a carb should run at or boost referenced regulators, all that is pretty obvious imo... the real question is what pressure can holley black be turned up to? 18 psi, 23 psi, 30 psi?
User avatar
F1Fever
Guru
Guru
 
Posts: 1649
Joined: Fri Feb 17, 2006 9:17 am
Location: Okla

Re: max fuel pressure w/holley? tried 18 psi, got it to work

Postby JDR Performance » Sat Apr 10, 2010 6:32 am

Too much fuel pressure will aerate the fuel and a lot of times you'll have to "bury" the float to keep it from bleeding over. For the blow through guys, setting the fuel pressure at the correct base setting and using a boost referenced regulator is the right way to do it.
JDR Performance
Pro
Pro
 
Posts: 399
Joined: Sat Mar 06, 2010 8:26 am

Re: max fuel pressure w/holley? tried 18 psi, got it to work

Postby F1Fever » Sat Apr 10, 2010 6:40 am

yes, obviously... finding a carb that runs at 18 or even 30 psi... lol... but what can a holley black safely take? If one will take 21 psi easily then we can try for 12-14 psi with a large safety margin. boost referenced regulators are relativity cheap, high flow, high pressure pumps, not so much esp if a holley black can handle 21 psi safely with a simple spring change... if there is no answer we will test and find out withing the next month.
User avatar
F1Fever
Guru
Guru
 
Posts: 1649
Joined: Fri Feb 17, 2006 9:17 am
Location: Okla

Re: max fuel pressure w/holley? tried 18 psi, got it to work

Postby Matt Gruber » Sat Apr 10, 2010 6:56 am

F1Fever wrote:yes, obviously... finding a carb that runs at 18 or even 30 psi... lol... but what can a holley black safely take? If one will take 21 psi easily then we can try for 12-14 psi with a large safety margin. boost referenced regulators are relativity cheap, high flow, high pressure pumps, not so much esp if a holley black can handle 21 psi safely with a simple spring change... if there is no answer we will test and find out withing the next month.

One a way i analyze a problem is to think up an extreme example. So, say u need 100psi, 200 psi to win a large bet. how? I'd think a long float arm would be needed to get enough leverage. Then maybe the viton tip would fail, so it might need a metal, alcohol needle. might discover other problems along the way. Good luck!
PS my 4165 has a side hung floats! is center hung shorter? i'd expect less max!
.
.
tame a lumpy cam for the street, more street hp, 14.5-18 mpg around town (was 11-14) with a fully divided dual plane, see my site:
http://community-2.webtv.net/mattgru/carb/
drive off cold 1200 rpm no stall
Matt Gruber
Guru
Guru
 
Posts: 1617
Joined: Fri Mar 19, 2010 6:32 am
Location: near Daytona Beach FL

Re: max fuel pressure w/holley? tried 18 psi, got it to work

Postby F1Fever » Sat Apr 10, 2010 7:59 am

#-o #-o what has happened around here...?
even with 21 psi of line pressure, the regulator maintains 5-7 lbs. even under boost, 5-7 lbs relative to the atmospheric pressure in the fuel bowls... well actually manifold pressure but
http://www.quickfueltechnology.com/bill ... lator.html
checking out of this thread, I must have missed the point of it entirely...
User avatar
F1Fever
Guru
Guru
 
Posts: 1649
Joined: Fri Feb 17, 2006 9:17 am
Location: Okla

Re: max fuel pressure w/holley? tried 18 psi, got it to work

Postby Matt Gruber » Sat Apr 10, 2010 8:41 am

fine, when it works.
One day when it, the regulator, craps out will the carb flood all over the engine and maybe start a fire? That is my point, fire prevention. If the carb can take high psi, that is an upgrade imo.
.
.
tame a lumpy cam for the street, more street hp, 14.5-18 mpg around town (was 11-14) with a fully divided dual plane, see my site:
http://community-2.webtv.net/mattgru/carb/
drive off cold 1200 rpm no stall
Matt Gruber
Guru
Guru
 
Posts: 1617
Joined: Fri Mar 19, 2010 6:32 am
Location: near Daytona Beach FL

Re: max fuel pressure w/holley? tried 18 psi, got it to work

Postby Stan Weiss » Sat Apr 10, 2010 9:25 am

F1Fever wrote:yes, obviously... finding a carb that runs at 18 or even 30 psi... lol... but what can a holley black safely take? If one will take 21 psi easily then we can try for 12-14 psi with a large safety margin. boost referenced regulators are relativity cheap, high flow, high pressure pumps, not so much esp if a holley black can handle 21 psi safely with a simple spring change... if there is no answer we will test and find out withing the next month.


Remember that you will see more pressure when you check it dead headed then at max. flow.

Stan
Stan Weiss / World Wide Enterprises
Offering Performance Software Since 1987
Image
http://www.erols.com/srweiss/index.html
User avatar
Stan Weiss
Guru
Guru
 
Posts: 2775
Joined: Tue Feb 20, 2007 1:31 pm
Location: Philadelphia, PA

Re: max fuel pressure w/holley? tried 18 psi, got it to work

Postby hondo383 » Sat Apr 10, 2010 12:44 pm

cjperformance wrote: The more pressure thru the needle and seat, the more fuel foaming/airation will occur which is BAD for maintaining an accurate feel curve.

exactly what i was thinking..i think its
bad enough fighting aeration at normal fuel pressures..
hondo383
Member
Member
 
Posts: 147
Joined: Sat Mar 03, 2007 1:01 pm
Location: massachusetts

Re: max fuel pressure w/holley? tried 18 psi, got it to work

Postby F1Fever » Sat Apr 10, 2010 1:27 pm

Stan Weiss wrote:
F1Fever wrote:yes, obviously... finding a carb that runs at 18 or even 30 psi... lol... but what can a holley black safely take? If one will take 21 psi easily then we can try for 12-14 psi with a large safety margin. boost referenced regulators are relativity cheap, high flow, high pressure pumps, not so much esp if a holley black can handle 21 psi safely with a simple spring change... if there is no answer we will test and find out withing the next month.


Remember that you will see more pressure when you check it dead headed then at max. flow.

Stan


I found there is a 19 psi spring for the holley black pumps (I assume it works for the reds and blues also). With that spring and a carb set for 5 psi fuel pressure we should be able to safely run 12, maybe 14 #' of boost. With a 16 psi low pressure cutoff switch before the regulator I see no problem with 12 lbs of boost. just to clarify what I was saying earlier...
User avatar
F1Fever
Guru
Guru
 
Posts: 1649
Joined: Fri Feb 17, 2006 9:17 am
Location: Okla

Re: max fuel pressure w/holley? tried 18 psi, got it to work

Postby Stan Weiss » Sat Apr 10, 2010 5:02 pm

The rating for the spring only tells you the max. pressure that it will let the pump make it does not tell you the pump can make that pressure under running conditions. Try flowing the pump. Lets say you have two (2) 0.110" seats. Put a plug with a 0.156" hole (same area as 2 0.110" holes) into your fuel line and you can check both pressure and volume.

Stan
Stan Weiss / World Wide Enterprises
Offering Performance Software Since 1987
Image
http://www.erols.com/srweiss/index.html
User avatar
Stan Weiss
Guru
Guru
 
Posts: 2775
Joined: Tue Feb 20, 2007 1:31 pm
Location: Philadelphia, PA

Re: max fuel pressure w/holley? tried 18 psi, got it to work

Postby cjperformance » Sun Apr 11, 2010 6:07 pm

Stan Weiss wrote:
cjperformance wrote:When running as blow thru you need to remember that the fuel inlet pressure may be higher than 4-6psi BUT this pressure will be relative to the boost pressure that is inside the fuel bowl. IE- if you run 10psi boost in blow thru form then to maintain a relative fuel pressure of say 6psi you need 16psi in the fuel line. In this instance the needle and seat only sees this ar 6psi ( the difference between bowl pressure(from boost) and fuel inlet pressure.)

As Joe says, too much pressure is not so good with a carb. The more pressure thru the needle and seat, the more fuel foaming/airation will occur which is BAD for maintaining an accurate feel curve. If you cant get enough fuel flow in there with 5psi in the line, then you need to rework the fuel system to flow more fuel at 5psi.


Shouldn't this be done with a boost reference regulator and not running the higher pressure all of the time?

Stan



Yes Yes Yes, I didnt go that far into it but should have.
Most definetly, The fuel pressure must constantly be referenced to boos pressure.
ie, for a 6psi relative fuel pressure the referenced reg/pump/whaterver controls your fuel press will maintain a 6psi difference, usually starting with say 6psi from intake vac thru to boost, then 1psi boost will give 7psi fuel, 5psi boost will give 11psi fuel, 20psi boost will give 26psi fuel and so on.
Craig.
cjperformance
Guru
Guru
 
Posts: 1467
Joined: Tue Aug 19, 2008 6:20 am
Location: South Australia

Re: max fuel pressure w/holley? tried 18 psi, got it to work

Postby blow-thru » Mon Apr 12, 2010 6:55 am

I think alot of people are forgetting a very important issue and thats VOLUME and trust me when I say that when you try to push a holley pump beyond its normal rating that the volume Seriously drops !!!!!.
This is the case with most fuel pumps which is why when you are specing a pump for an application N/A or boosted that they are rated at a specific flow at said psi ...
As for the added fuel pressure that alot of pumps have over the needed carb requirement, these are often rated at free flow which is totally different than under load plus the extra pressure needed to overcome G-forces and fuel line size and the list goes on and on....
Thus dont be persuaded by fuel pump specs as they can be very misleading !!!! and obtain much info on the brands your looking at {flow charts etc}
Cheers Carl...
blow-thru
Member
Member
 
Posts: 157
Joined: Wed Feb 21, 2007 7:18 am
Location: Perth Australia

Re: max fuel pressure w/holley? tried 18 psi, got it to work

Postby oldhead » Mon Apr 12, 2010 4:48 pm

HAS ANYONE HERE HAD A FIRE DUE TO A BAD FUEL PRESSURE REGULATOR????NO SUCH THING....Oldhead PS;Matt these guys are trying to help you,think about what there saying
Quicker then most
oldhead
Pro
Pro
 
Posts: 342
Joined: Sat Aug 13, 2005 8:49 am
Location: NE.Phila.

Re: max fuel pressure w/holley? tried 18 psi, got it to work

Postby Matt Gruber » Mon Apr 12, 2010 5:00 pm

oldhead wrote:HAS ANYONE HERE HAD A FIRE DUE TO A BAD FUEL PRESSURE REGULATOR????NO SUCH THING....Oldhead PS;Matt these guys are trying to help you,think about what there saying

It may very well be that there is no advantage to a more robust fuel inlet. I'm Ok with that analysis. Not everything i do turns out to be helpful. Thanks for all the replies!
.
.
tame a lumpy cam for the street, more street hp, 14.5-18 mpg around town (was 11-14) with a fully divided dual plane, see my site:
http://community-2.webtv.net/mattgru/carb/
drive off cold 1200 rpm no stall
Matt Gruber
Guru
Guru
 
Posts: 1617
Joined: Fri Mar 19, 2010 6:32 am
Location: near Daytona Beach FL

Previous

Return to Engine Tech

Who is online

Users browsing this forum: accurate engine, BigBlocksOnTop2, Calypso, Daniel Jones, dfitz16, mag442, nxtruck, Orr89rocz, Ranken Tech, vincenelson and 24 guests