adjusting fuel pressure on TBI - Various Options
Bruce Plecan
nacelp at bright.net
Sun Oct 22 00:41:49 GMT 2000
This is a multi-part message in MIME format.
------=_NextPart_000_0202_01C03B9F.4CCCC160
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
This ought to go near the FAQ or something
Good Coverage
Bruce
----- Original Message -----=20
From: Walter Sherwin=20
To: diy_efi at diy-efi.org=20
Sent: Saturday, October 21, 2000 2:55 PM
Subject: Re: adjusting fuel pressure on TBI - Various Options
Assuming you are using the common GM 2bbl TBI's, you have the =
following options for playing with fuel pressure (NOTE: most garden =
variety 2bbl TBI regulators were factory set for a range of 9-13psig, =
but be aware that there were also some identical looking ones that were =
set for "other" ranges. So, it's best to check where you're at before =
swapping). Options are as follows......
1) Bolt on an aftermarket adjustable TBI regulator from Turbo City, =
Hypertech, JET, etc. All of these will adjust up to about almost =
15psig, depending upon your setup and pump voltage. This would be a =
logical replacement for a factory 9-13psig unit, for an engine that has =
been warmed over with a few mods.
2) A step beyond......GM TBI regulator P/N 17113186 is a direct =
bolt-on jobbie, and will give you about 18-20psig fuel pressure. =
Additionally, this regulator has vacuum compensation capability. If you =
hook the included vac port to manifold vacuum, then you'll get a part =
throttle fuel pressure decay of roughly 1psig per every 2"Hg manifold =
vacuum. This comes from certain marine and HT502 applications.
3) A little bigger step beyond.......GM TBI regulator P/N 17113079 is =
a direct bolt-on jobbie, and will give you about 26-32psig. It does not =
have vac compensation. This comes from some of the late 90's BBC =
applications.
4) You can add vac compensation to any TBI regulator, if you have the =
time and patience to get creative. Basically, you just need to make =
the can assembly that surrounds the backside of the diaphragm "sealed", =
and then plumb it to manifold vacuum. You can either do this thru =
sealing/welding shut the existing can, or machining a new can. The shop =
manual tells you not to disassemble these regulators, but in truth they =
are quite easy to dis/re assemble if you are careful. =20
5) You can change the setpoint of your stock regulator by roughly +/- =
2psig, quite easily. Sometimes without even having to disassemble it. =
Remove the whole fuel meter cover and regulator assembly from your TBI =
and flip it upside down in your left hand. You should note a =
rectangular window cut in the side of the regulator can, with the end of =
a tang visibly located somewhere between the extreme ends of that =
window. The tang is attached to the spring perch within, and it's =
relative up/down position is roughly proportional to the setpoint of the =
regulator. Move tang up, more pressure, move tang down, less pressure. =
Now, look at the bottom of the can and you will probably see a beefy =
collar with what appears to be a screw tack welded in the middle. You =
can either dremel away the tack weld and manipulate the screw, or, you =
can try this next approach. Firmly grasp the collar with a good set of =
vice grips or channel-lock pliers, and gently attempt to force the =
collar counter clockwise. Chances are pretty good that the tack welds =
between the can and the collar will snap, and you can then proceed to =
turn the whole collar assembly counter clockwise to raise the pressure =
slightly. If this does not work for you, or if your regulator does not =
have a collar (as some don't), then you'll have to disassemble the =
regulator to modify it. Again, spin the perch counter clockwise on the =
screw shaft to compress the spring and raise the pressure.
6) The external regulator approach.........You can also leave your =
stock TBI regulator in place (no need to gut it unless planning to get =
really wild with pressures, and fear a burst diaphragm), and then =
graft-in any flavour of external regulator, into the TBI return fuel =
line, remote from the TBI assembly. The external regulator can either =
be a "fixed" pressure jobbie without vac compensation (intended to =
continually override the setpoint of the stock TBI regulator), or, it =
can be a "variable" vac compensated jobbie (intended to provide more =
fuel when needed and then cut back and allow the stock TBI regulator to =
take control during cruise). =20
7) Whether to run a fixed pressure, or a variable pressure, at the =
TBI injectors all comes down to your personal level of comfort with the =
TBI software at hand. The most elegant approach is to select a fixed =
pressure operating point, then modify the software injector BPC's to =
suit, and then cal the VE's to suit your engine mods (this carries with =
it the assumption that you will either measure or calculate your new =
injector flow rates at your new pressure setpoint). But, if software =
modifications are troublesome, then variable pressures can be used to at =
least get things pretty durn close, and then rely upon the INT/BLM =
features to reign things into control.
8) As a general rule of thumb, I've found that most GM Rochester TBI =
injectors will comfortably tolerate up to 30'ish psig without issue, =
assuming that they are connected to individual 4/1 amp drivers. There =
are some TBI injectors that can be driven has high as 70psig, but they =
are an exception rather than the norm.
Sorry for the long missive, but I thought I'd dump as many related =
ideas as I could in one place, while I had the chance, in case someone =
was surfing the archives in a couple of years.
Walt.=20
----- Original Message -----=20
From: thom358=20
To: diy_efi at diy-efi.org=20
Sent: Friday, October 20, 2000 11:14 PM
Subject: adjusting fuel pressure on TBI
Is there an adjustable fuel pressure regulator for a TBI setup? is =
there a way to bypass the origional, or gut it and run an aftermarket =
regulator? I am would like to run more fuel pressure, but I want to be =
able to adjust it. Any thoughts are appreciated.
THOM
------=_NextPart_000_0202_01C03B9F.4CCCC160
Content-Type: text/html;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=3DContent-Type content=3D"text/html; =
charset=3Diso-8859-1">
<META content=3D"MSHTML 5.50.4207.2601" name=3DGENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY bgColor=3D#ffffff>
<DIV><FONT face=3DArial size=3D2>This ought to go near the FAQ or=20
something</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Good Coverage</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Bruce</FONT></DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3Dwsherwin at home.com href=3D"mailto:wsherwin at home.com">Walter =
Sherwin</A>=20
</DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Ddiy_efi at diy-efi.org=20
href=3D"mailto:diy_efi at diy-efi.org">diy_efi at diy-efi.org</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Saturday, October 21, =
2000 2:55=20
PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> Re: adjusting fuel =
pressure on=20
TBI - Various Options</DIV>
<DIV><BR></DIV>
<DIV><FONT size=3D2>Assuming you are using the common =
GM 2bbl TBI's,=20
you have the following options for playing with fuel pressure =
(NOTE:=20
most garden variety 2bbl TBI regulators were factory set for a range =
of=20
9-13psig, but be aware that there were also some identical looking =
ones that=20
were set for "other" ranges. So, it's best to check where you're =
at=20
before swapping). Options are as follows......</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>1) Bolt on an aftermarket adjustable TBI regulator =
from=20
Turbo City, Hypertech, JET, etc. All of these will adjust up to =
about=20
almost 15psig, depending upon your setup and pump voltage. This =
would be=20
a logical replacement for a factory 9-13psig unit, for an engine that =
has been=20
warmed over with a few mods.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>2) A step beyond......GM TBI regulator P/N =
17113186 is a=20
direct bolt-on jobbie, and will give you about 18-20psig fuel =
pressure. =20
Additionally, this regulator has vacuum compensation =
capability. If=20
you hook the included vac port to manifold vacuum, then you'll get a =
part=20
throttle fuel pressure decay of roughly 1psig per every 2"Hg manifold=20
vacuum. This comes from certain marine and HT502=20
applications.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>3) A little bigger step beyond.......GM TBI =
regulator P/N=20
17113079 is a direct bolt-on jobbie, and will give you about =
26-32psig. =20
It does not have vac compensation. This comes from some of the =
late 90's=20
BBC applications.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>4) You can add vac compensation to any TBI =
regulator, if you=20
have the time and patience to get creative. Basically, you =
just=20
need to make the can assembly that surrounds the backside of the =
diaphragm=20
"sealed", and then plumb it to manifold vacuum. You can either =
do this=20
thru sealing/welding shut the existing can, or machining a new =
can. The=20
shop manual tells you not to disassemble these regulators, but in =
truth they=20
are quite easy to dis/re assemble if you are careful. =
</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>5) You can change the setpoint of your stock =
regulator by=20
roughly +/- 2psig, quite easily. Sometimes without even =
having to=20
disassemble it. Remove the whole fuel meter cover and regulator =
assembly=20
from your TBI and flip it upside down in your left hand. You =
should note=20
a rectangular window cut in the side of the regulator can, with the =
end of a=20
tang visibly located somewhere between the extreme ends of that =
window. =20
The tang is attached to the spring perch within, and it's relative =
up/down=20
position is roughly proportional to the setpoint of the =
regulator. Move=20
tang up, more pressure, move tang down, less pressure. Now, look =
at the=20
bottom of the can and you will probably see a beefy collar with what =
appears=20
to be a screw tack welded in the middle. You can either dremel =
away the=20
tack weld and manipulate the screw, or, you can try this next =
approach. =20
Firmly grasp the collar with a good set of vice grips or channel-lock =
pliers,=20
and gently attempt to force the collar counter clockwise. =
Chances are=20
pretty good that the tack welds between the can and the collar will =
snap, and=20
you can then proceed to turn the whole collar assembly counter =
clockwise to=20
raise the pressure slightly. If this does not work for you, or =
if your=20
regulator does not have a collar (as some don't), then you'll have to=20
disassemble the regulator to modify it. Again, spin the perch =
counter=20
clockwise on the screw shaft to compress the spring and raise the=20
pressure.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>6) The external regulator approach.........You can =
also=20
leave your stock TBI regulator in place (no need to gut it unless =
planning to=20
get really wild with pressures, and fear a burst diaphragm), and then =
graft-in=20
any flavour of external regulator, into the TBI return fuel line, =
remote from=20
the TBI assembly. The external regulator can either be a "fixed" =
pressure jobbie without vac compensation (intended to continually =
override the setpoint of the stock TBI regulator), or, it can be a =
"variable"=20
vac compensated jobbie (intended to provide more fuel when needed =
and=20
then cut back and allow the stock TBI regulator to take control during =
cruise). </FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>7) Whether to run a fixed pressure, or a =
variable=20
pressure, at the TBI injectors all comes down to =
your personal=20
level of comfort with the TBI software at hand. The most elegant =
approach is to select a fixed pressure operating point, then =
modify=20
the software injector BPC's to suit, and then cal the VE's to suit =
your engine=20
mods (this carries with it the assumption that you will either measure =
or=20
calculate your new injector flow rates at your new=20
pressure setpoint). But, if software modifications are =
troublesome,=20
then variable pressures can be used to at least get things =
pretty=20
durn close, and then rely upon the INT/BLM features to reign things =
into=20
control.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>8) As a general rule of thumb, I've found =
that most GM=20
Rochester TBI injectors will comfortably tolerate up to 30'ish psig =
without=20
issue, assuming that they are connected to individual 4/1 amp =
drivers. =20
There are some TBI injectors that can be driven has high =
as 70psig,=20
but they are an exception rather than the norm.</FONT></DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>Sorry for the long missive, but I thought I'd dump =
as many=20
related ideas as I could in one place, while I had the chance, in case =
someone=20
was surfing the archives in a couple of years.</FONT></DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>Walt.</FONT> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<BLOCKQUOTE=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3Dthom358 at netzero.net =
href=3D"mailto:thom358 at netzero.net">thom358</A>=20
</DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Ddiy_efi at diy-efi.org=20
href=3D"mailto:diy_efi at diy-efi.org">diy_efi at diy-efi.org</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Friday, October 20, =
2000 11:14=20
PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> adjusting fuel =
pressure on=20
TBI</DIV>
<DIV><BR></DIV>
<DIV>Is there an adjustable fuel pressure regulator for a TBI =
setup? =20
is there a way to bypass the origional, or gut it and run an =
aftermarket=20
regulator? I am would like to run more fuel pressure, but I =
want to be=20
able to adjust it. Any thoughts are appreciated.</DIV>
<DIV> </DIV>
<DIV>THOM</DIV></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>
------=_NextPart_000_0202_01C03B9F.4CCCC160--
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org
More information about the Diy_efi
mailing list