View Full Version : Inline pump? How?
I'm curious as to physically how this works... A stock fuel pump say rated at 110 L/Hr feeds an inline 255 L/Hr somehow delivers more fuel to the injectors?
A lot of sport compact guys I've seen are doing it and it supposedly works. I've tried doing research and came up with no results. I've even questioned every guy at our Technical Support Center and they couldnt give me an actual answer.
My thoughts on it... Once both pumps are on the in tank pump would not be able to keep up with the inline pump. The inline pump will push more volume then the in tank pump can keep up with, causing it to run dry between the two.
On the other end of the argument, the VW guys "think" because the in tank pump causes less pressure ahead of the in tank pump the in tank will then flow more... this is true. However until it reaches it's max free flow point. After that point (or until the ID of the line poses a restriction) it wouldnt be beneficial. Ex. A 110 L/Hr pump free flows at 110 L/Hr at say 80psi... well attached to 3/8" ID line it now flows 100 L/Hr at 50psi... well after you turn on the inline pump this would cause the in tank pump to have less pressure ahead of it causing it to flow more volume. Just my thinking on it...
Ive also heard mentioned of placing a surge tank between the two pumps... again though, the in tank would fill up the tank until the inline kicks on and runs it dry.
Any thoughts?
-Bryan
BadAssPerformance
03-09-2010, 01:50 AM
The second pump reduces the load (pressure) off the first pump so it can pump more then designed. IIR, GLHS's had two pumps in tandem... stock in tank and inline from Shelby. Works ok if both pumps are healthy...
The second pump reduces the load (pressure) off the first pump so it can pump more then designed. IIR, GLHS's had two pumps in tandem... stock in tank and inline from Shelby. Works ok if both pumps are healthy...
Yah that's what I had thought. I just wasnt sure to try it on the VW or not...
Ondonti
03-09-2010, 02:28 AM
The feed pump is allowed to flw 110lph or more (whatever its rated at for ZERO psi, probably much much much more then 110lph).
The secondary pump handles ALL the pressure creation. a 255lph walbro intank at 12.0v (non high pressure, relief valve opens around 70psi) pump at 80 psi only flows 140lph. External Walbros have no relief so they flow more then the intank. so in the end, adding a single external walbro will flow more then an internal even with a little pump.
I have the AMS fuel pump tests saved on my desktop but they seem to be removed from the internet and the clone thread on NASIOC seems to have been deleted.
If I was home I would just put the picture files into my photobucket.
contraption22
03-09-2010, 07:41 AM
The second pump reduces the load (pressure) off the first pump so it can pump more then designed. IIR, GLHS's had two pumps in tandem... stock in tank and inline from Shelby. Works ok if both pumps are healthy...
I thought only the '85 Turbo L-bodies had two pumps.
Aries_Turbo
03-09-2010, 09:53 AM
when you decrease the amount of pressure a pump has to create as it pushes against a resistance (aka regulator and injectors that resist the flow vs the inlet of another pump thats sucking fuel up) the flow goes up drastically. put a vac/pressure gauge between the pumps and see what its doing. you can use a boost gauge with metal line if its just a temporary test. also watch the pressure at the rail.
if at high boost/rpm/power production, the gauge reads vacuum between the two pumps, then you may need a larger intank pump to feed the secondary pump, especially if the pressure starts dropping off at the rail.
brian
when you decrease the amount of pressure a pump has to create as it pushes against a resistance (aka regulator and injectors that resist the flow vs the inlet of another pump thats sucking fuel up) the flow goes up drastically. put a vac/pressure gauge between the pumps and see what its doing. you can use a boost gauge with metal line if its just a temporary test. also watch the pressure at the rail.
if at high boost/rpm/power production, the gauge reads vacuum between the two pumps, then you may need a larger intank pump to feed the secondary pump, especially if the pressure starts dropping off at the rail.
brian
Great idea. But I thought fuel pumps don't suck? ;) Or do they? That's a serious question lol.
contraption22
03-09-2010, 02:09 PM
Fuel pumps will suck. But the harder they have to suck, the less they can push.
contraption22
03-09-2010, 02:12 PM
when you decrease the amount of pressure a pump has to create as it pushes against a resistance (aka regulator and injectors that resist the flow vs the inlet of another pump thats sucking fuel up) the flow goes up drastically.
brian
Exactly. This is why a given pump can supply more volume with bigger injectors and lower fuel pressure vs. smaller injectors at higher fuel pressure.
Some high performance fuel pumps have two ratings. One for n/a applications and one for boosted applications, because boosted applications generally run higher fuel pressure.
turbovanmanČ
03-09-2010, 06:17 PM
VW's and some other manufacters run a small intank pump to feed the big inline pump, they can run stupid fuel pressures etc and not effect the intank pump but once the intank one fails, all kinds of weird things happen.
shackwrrr
03-10-2010, 05:34 PM
Fuel pumps will suck. But the harder they have to suck, the less they can push.
Nothing sucks. Substance is only pushed from an area of greater pressure to a lower pressure. you lower the pressure behind the pump and atmospheric pressure pushes fuel into it.
92spiritrt
03-10-2010, 07:06 PM
I thought only the '85 Turbo L-bodies had two pumps.
i don't think they did, at least the '85 glht i had only had one in tank pump.
Ondonti
03-10-2010, 08:30 PM
BTW, a cheap way to balance fuel pump flow would be to use the stock 12v wiring on the inline pump and then hotwire the intank pump to 13.5-14v (altenator voltage). This should make up the difference between the pumps if you do see vacuum.
I spent a bunch of time trying to get dual inline walbros to not overpower the rising rate regulator I was using. Ended up using bridge rectifiers to drop voltage to my pumps to decrease flow. You could also do that for less then 5 bucks until you feel like upgrading the intank pump. Truth is that even dropping voltage at the external pump, it will flow more at high pressure then a single intank walbro because of the lack of pressure relief.
TheCanadian007
03-10-2010, 10:16 PM
As far as adding an inline pump goes, if one were to convert a carb engine to Turbo MPFI and use an inline pump, could one just rig it up and keep the stock sender/pickup tube? Thoughts upon this?
amoparacer
03-11-2010, 12:07 AM
The external Walbro 255 will support cars up to 700 hp. On my shelby 924 I use a walbro 255 intank and a walbro exteranal 255 in line two support 120 injectors with E85
Speedeuphoria
03-11-2010, 06:17 PM
I spent a bunch of time trying to get dual inline walbros to not overpower the rising rate regulator I was using.
Is this b/c your return line is too small or just something to do w/ RRR's?
strang3majik
03-11-2010, 06:22 PM
i don't think they did, at least the '85 glht i had only had one in tank pump.
no body believes that my Omni GLH carb car has an original electric in tank fuel pump, either...lol
It has the wiring under the carpet, the fuse in the fuse box with factory "fuel pump" writing on it, and it kicks on with the key and everything as it should, and I can tell its not aftermarket...but...no one believes me...haha.
Juggy
03-11-2010, 07:18 PM
i purchased a carbed L body tank and a universal rear sump, im ditching the intank walbro and going with an external pump!
going to run -10 line and fuel filters then -8 to the rail with -6 return
cant wait!!!! and hopefully i dont have anymore fueling issues :)
last year i was burnin sub 12's@115mph in the 1/4 on a mere 45psi fuel pressure @ 25psi boost hehehe.....if only i had known sooner.
contraption22
03-11-2010, 07:50 PM
i purchased a carbed L body tank and a universal rear sump, im ditching the intank walbro and going with an external pump!
going to run -10 line and fuel filters then -8 to the rail with -6 return
cant wait!!!! and hopefully i dont have anymore fueling issues :)
last year i was burnin sub 12's@115mph in the 1/4 on a mere 45psi fuel pressure @ 25psi boost hehehe.....if only i had known sooner.
Somebody here was about to attempt that, but then decided to go another route when they realized that the fuel sump, and more specifically the fittings, would be the lowest point in the car, some 2" lower than the tank itself. Scary for a car that sees alot of real world driving.
rx2mazda
03-11-2010, 08:52 PM
Somebody here was about to attempt that, but then decided to go another route when they realized that the fuel sump, and more specifically the fittings, would be the lowest point in the car, some 2" lower than the tank itself. Scary for a car that sees alot of real world driving.
That's my set-up. I was worried about that at first too but, after getting it in the car, the rear track bar sits lower than the sump/fittings. I may still fab up some sort of guard for the bottom.
Juggy
03-11-2010, 09:08 PM
Somebody here was about to attempt that, but then decided to go another route when they realized that the fuel sump, and more specifically the fittings, would be the lowest point in the car, some 2" lower than the tank itself. Scary for a car that sees alot of real world driving.
the car had 2 flats when i looked underneath and there was def room for the sump. i wouldnt be too worried about fittings, just angle them the right way and they wont point towards the ground ;)
That's my set-up. I was worried about that at first too but, after getting it in the car, the rear track bar sits lower than the sump/fittings. I may still fab up some sort of guard for the bottom.
oh nice, what line are you running?? fuel pump? etc....i was going to go with dual fuel filters, 70 micron prefilter then 30 micron after external pump. thats where it will go to -8 as well. gonna go with -10 on the pump and filters because thats the size of the pump fittings, and id rather try and have that thing suck as freely as possible! sump has 1/2" npt fittings...so it should work out nice
rx2mazda
03-11-2010, 11:41 PM
oh nice, what line are you running?? fuel pump? etc....i was going to go with dual fuel filters, 70 micron prefilter then 30 micron after external pump. thats where it will go to -8 as well. gonna go with -10 on the pump and filters because thats the size of the pump fittings, and id rather try and have that thing suck as freely as possible! sump has 1/2" npt fittings...so it should work out nice
Combo of 1/2 aluminum hard lines and -8 flex-lite to the rail. -6 and 3/8 hard line return. Twin Bosch 044 pumps with HP check valves. There are pics in my PLOG thread.
92spiritrt
03-11-2010, 11:53 PM
i'm doing a similar setup. i can post a pic of where everything will be mounted tomorrow. the way mine is done is with a sump on the factory tank(1/2"npt). i am running two -8's out of the sump into a y block that turns into a -10. then after the filters and pump it will be a -8 feed. i haven't installed it yet. hopefully within the next week or so.
Great info guys. Took a lot out of this post. :nod:
92spiritrt
03-12-2010, 04:42 PM
here is what i was talking about. i haven't made the bracket to hold the pump and first filter(75 micron) yet. it is a little low, but not any lower than my exhaust and i've had no problems with that hitting during street driving. the sump is about 3" tall and the pump diameter is 2-5/8". the second filter(10 micron) is going where the stock filter is located. it will have a -10 line running from the pump to filter then drop to -8 feed to the rail. i'm going to try using the stock feed line as the return being that most people run a -6(3/8") line as a return and the stock feed is 5/16" so it should be close enough. the -8 lines running from the sump still have to be cut down(they were pulled off of my gremlin). this is all going into a spirit r/t by the way.
http://i180.photobucket.com/albums/x82/92spiritrt/spirit/100_0665.jpg
http://i180.photobucket.com/albums/x82/92spiritrt/spirit/100_0664.jpg
Juggy
03-12-2010, 06:45 PM
nice, looks like the competition engineering one?? thats what i got. 4041 or something like that was the #....1/2" NPT
yes i was going the same route, -10 filters and pump to -8 feed. im already running -6 feed, so i dont have to worry about the return line, as ill use the original feed from the carriage as the new return ;)
im only planning on running a single pump....
here is what i was talking about. i haven't made the bracket to hold the pump and first filter(75 micron) yet. it is a little low, but not any lower than my exhaust and i've had no problems with that hitting during street driving. the sump is about 3" tall and the pump diameter is 2-5/8". the second filter(10 micron) is going where the stock filter is located. it will have a -10 line running from the pump to filter then drop to -8 feed to the rail. i'm going to try using the stock feed line as the return being that most people run a -6(3/8") line as a return and the stock feed is 5/16" so it should be close enough. the -8 lines running from the sump still have to be cut down(they were pulled off of my gremlin). this is all going into a spirit r/t by the way.
http://i180.photobucket.com/albums/x82/92spiritrt/spirit/100_0665.jpg
http://i180.photobucket.com/albums/x82/92spiritrt/spirit/100_0664.jpg
92spiritrt
03-12-2010, 07:09 PM
yep its the 1/2" comp engineering one. you are better off imo to use a single pump. a friend of mine had a dual intank walbro 340 pump setup in his ttype. one of the pumps failed at the track and he ended up melting a piston. since one pump was still running the motor didn't shut down but it couldn't supply enough fuel for all six cylinders. after that happened i would never even consider running multiple pumps.
contraption22
03-18-2010, 11:53 AM
Does anybody know if you can simply put a carb'd Lbody pickup in an EFI Lbody tank to run an external pump?
TheCanadian007
03-18-2010, 12:12 PM
Does anybody know if you can simply put a carb'd Lbody pickup in an EFI Lbody tank to run an external pump?
What about carb tank/pickup with external Walbro 255 pump? (Mounted under the car where the stock filter is.)
Juggy
03-18-2010, 12:32 PM
Does anybody know if you can simply put a carb'd Lbody pickup in an EFI Lbody tank to run an external pump?
that baffle pan might get in the way of things
What about carb tank/pickup with external Walbro 255 pump? (Mounted under the car where the stock filter is.)
yes this is definitely doable
Aries_Turbo
03-18-2010, 02:01 PM
Does anybody know if you can simply put a carb'd Lbody pickup in an EFI Lbody tank to run an external pump?
does the carb pickup come up and out of the tank similar to how the EFI pickup exits the tank?
if it does, and you hold the EFI pickup side by side the carb pickup and make sure the carb pickup inlet draws fuel at the same level and location as the EFI pickup while avoiding the baffling, youll be all set.
Brian
contraption22
03-18-2010, 03:04 PM
What about carb tank/pickup with external Walbro 255 pump? (Mounted under the car where the stock filter is.)
This works fine as long as you never plan to do any hard cornering or hard launching under 1/2 tank of fuel. This is the setup I am using now.
Does anybody know if you can simply put a carb'd Lbody pickup in an EFI Lbody tank to run an external pump?
I think that's how Cliff's old Silver Bullet (now Barry's car) was set up. I seem to recall Barry did a little bit of modification to the pick up itself, but I'm almost positive it's still the carb'd pick up with an external pump.
contraption22
03-18-2010, 03:48 PM
Hey... I actually did find a pump, pickup, and sender assembly from Airtex on RockAuto.com
PN E7073S
Its for tbi apps, but I wonder if you can just change out the pump?
Aries_Turbo
03-18-2010, 07:08 PM
Hey... I actually did find a pump, pickup, and sender assembly from Airtex on RockAuto.com
PN E7073S
Its for tbi apps, but I wonder if you can just change out the pump?
i bet you can. thats what i did with my k car. tbi car, turbo (walbro 255) pump.
Brian
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