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PostPosted: Mon Jul 19, 2010 11:55 pm 
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KB58 wrote:
Some (most?) internal pumps have a built-in pressure relief port that's constantly spewing fuel. Inside the tank it's not a problem, but obviously outside the tank it's a big problem. My brother's "external" pump had such a port which was impossible to tap into in order to feed it back to the tank.
I don't know about the Miata version of this, but if they have a built in pressure reg, when shifting to an external you need to make sure that the system still can regulate fuel pressure to the injectors or you'll end up with a rich running vehicle and damage the injectors.

Most have a FPR (Fuel Pressure Reg) at the Injector Rail, but some do not. My VW does, but my Audi does not! Confirm your application before changing something as important as a pump/reg. It could lead to a lot of headaches!

KS

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PostPosted: Tue Jul 20, 2010 12:02 am 
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The pump sets really low, right down with the fuel sock so I think KS may be right about needing fuel to cool it. (also- the FPR is on the rail in the Miata and requires a return line) Sitting that low, surely it will get a splash every now and then even when nearly empty. Also it may be worth a look to see where the fuel return from the rail dumps. It may dump over the pump to cool it. (which I think might be what Kurt said-I'm too lazy to re-read)

It's an odd shaped bit, bit You could probably make it fit in a plastic fuel tank. You may need to bend some tubing but I think you could swing it. I just went with the cheap Summit external pump since it was proven and seemed easier. I had no idea it would be so loud. The one good thing is that when you sucked up air (when the tank was nearly dry) it got even louder, emitting what was close to a squeal. :P That's how you knew it was time to fill up. :wink:


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PostPosted: Tue Jul 20, 2010 8:10 am 
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One of the nice things about my in-tank pump is that I can barely hear it. Not because I run a rotary and the exhaust sound overpowers the pump sound. And not because I am in my late 50's and can't hear worth a &^%$. When I turn the ignition on, before I crank her over, I have to pay attention to detect the pump is running. I usually wait the 4-5 seconds for the pump to build some pressure and stop running before I try to crank her over.

2nd) Does the Miata use a pump speed control resistor like my RX7? There is a large resistor and relay external to the tank, that operates the pump at a lower speed when a minimal amount of fuel is required. When needed, the relay turns off and shorts out the resitor putting full voltage to the pump. The control was fairly easy to implement with the Megasquirt so I did. I figured it was there to help extend the life of the pump. Just wonderin'.

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PostPosted: Tue Jul 20, 2010 10:28 am 
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the 1.6 has only a one speed pump -- and Chet the return line is the longer one in your pic and it dump down below the pump -- the main reason I use the in tank pump was that I wanted to use the Miata gauges and the fuel level sender was a different than most and I could not find an aftermarket replacement. I just cut the old tank up and used the flange (also used the vent flange, one way vent valve and filler neck fittings and check valve).

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PostPosted: Tue Jul 20, 2010 5:51 pm 
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A little more info on the Ford external pump.

This is a pic of the 80's bronco II/Ranger/F150 high pressure external pump I recently pulled. Some replacement pumps have removeable fittings on both ends, but one could slip a hose directly over the standard fitting. The insulator is a foam rubber sheet wrapped around the pump. It has spade terminals.


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PostPosted: Tue Jul 20, 2010 9:28 pm 
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Miatav8,MstrASE,A&P,F wrote:
A little more info on the Ford external pump.

This is a pic of the 80's bronco II/Ranger/F150 high pressure external pump I recently pulled. Some replacement pumps have removeable fittings on both ends, but one could slip a hose directly over the standard fitting. The insulator is a foam rubber sheet wrapped around the pump. It has spade terminals.
With that isolated bracket and all, that's a nice package.

Do you have any specs on it? PSI... GPM... Physical size?

Thanks!

KS

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PostPosted: Tue Jul 20, 2010 11:21 pm 
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shobley wrote:
Just about got the Miata body stripped, but I've not located the fuel pump - I must have unhooked the electrical connection somewhere, but I've not found the pump - do I need it for the final build, or will the tank I order have a more compatible pump?
Steve
From WikiAnswers, http://wiki.answers.com/Q/Where_is_the_ ... azda_Miata

"The fuel pump is in the gas tank. If you pull up the carpet behind the seats (where the top folds down) there is a panel on the driver's side that can be removed giving access to the gas tank. There you can unscrew another panel that opens up the actual gas tank. The fuel pump and gauge sender come out with that panel. "

My question to you is, why buy a "compatible pump" when you have the original one that is inside the Miata fuel tank now? Just remove all the screws at the top of the fuel tank around the place where the wires connect to the fuel tank and remove the pump and fuel level sender as a unit. (DON'T MAKE A SPARK WHILE REMOVING IT !!!) Save the gasket, you'll need it.

If you order a plastic fuel cell (Jazz comes to mind) just cut a hole in the new tank the same size as the in the Miata tank and mount the Miata stuff in it. If your new tank is taller than the Miata you will probably have to change the pump mounting hardware length so the pump is mounted near the bottom of the tank. You might also need to modify the fuel level float arm so the float has full travel from empty to full.

I used a universal fuel sender & gauge from JC Whitney that is adjustable for various height fuel tanks.

If you use a plastic tank you should make up a metal ring to match the screw holes in the cover so the new bolts/nuts you use will have a solid mounting surface inside the tank. For each of my small panels where the fuel gauge and fuel pump goes into my tank I made rings from 3/8" thick alum.

For ideas, see this article on my website how I mounted the original Suzuki motorcycle fuel pump in my Jazz fuel cell,

http://dmr-architect.com/~locouki/fuel-pump.html

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PostPosted: Wed Jul 21, 2010 5:44 pm 
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botbasher wrote:
Miatav8,MstrASE,A&P,F wrote:
A little more info on the Ford external pump.

Do you have any specs on it? PSI... GPM... Physical size?

Thanks!
KS

The original pump’s rating should be 125 LPH (33 GPH) @ 310 KPA (45 PSI). A "Performance Electric" P37 is the cheapest replacement pump from Rock at around $50. The largest engine application listed for the P37 is a 351 in a Ford E250. The 351 makes 210hp/315tq. I would be comfortable using the P37 with a 180hp/175tq VW 1.8L turbo. The bronco II this pump came from has a 2.9L v6 with 140hp/170tq.

Most pumps to fit the bracket are around $100 and are also applicable to the 460 applications. The 460 makes 230hp/390tq.

The bracket was used on everything from the 1986 2.3L aerostar to a 1991 7.5L F350 Super.

Check out the four to five pages of applications for this pump:
http://www.summitracing.com/parts/ATX-E2000

The pump in the bracket is 4.5" long with a 2" OD. The entire assembly is 6" wide x 5" high x 3.25" deep not counting the studs.

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PostPosted: Wed Jul 21, 2010 8:57 pm 
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Miatav8,MstrASE,A&P,F wrote:
.... I would be comfortable using the P37 with a 180hp/175tq VW 1.8L turbo.....
Thanks for digging those out for us.

The physical specs are nice.. a tight small isolated package, but it's the performance specs that would keep me from it.

We use 4 Bar FPRs on the VW lumps when looking to goose a few horses out of them. For the non-metric crowd, 1 Bar = 14.7psi, so just a shade shy of 60 psi. I know it would work at a basic level, but it's when it stops working that worries me! Long about 8k RPM... under heavy load... 21psi of boost... and the pump just can't push enough fuel. Well, there go my pistons..rings.. and valves!

I went looking for exact specs of the Bosch pump for the VW and found this.. I realize they are trying to sell parts, but if 1/2 of what they say is accurate, it's scary to a performance oriented mind!

Now I'm on a mission to find the VW specs.... you got me curious!

KS

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PostPosted: Wed Jul 21, 2010 9:07 pm 
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Leave it to a Langford to have it available for reference!!

The fuel pump delivers about 75 psi, which has never been a problem on cars since the injector lines are braided stainless steel from the factory, and "never" fail

Here is a page on the CIS system. I've used the pumps out of them several times now and they are great... just very expensive unless you buy aftermarket, but then as that last link showed... Do you really know what your getting in terms of performance?

I had also forgotten about the accumulator... guess I'm going to have to go rape a VW and not worry about a swirl tank!!

Cheers!

KS

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PostPosted: Wed Jul 21, 2010 9:30 pm 
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I've used Bosch CIS pumps in the past for various projects. They're one of the most reliable, powerful automotive fuel pumps of all. They're capable of more than 100psi -DEAD HEAD - and will run happily through a 30-50psi regulator without complaint. They can also deliver more volume than just about any fuel pump and will pull fuel a long way from the tank too.

The Bosch CIS system the pump was designed for needs around 90psi at the Fuel Distributor Control Plunger to control the movement of the Air Sensor Plate. If this pump can deliver that kind of pressure and last for as long as they do, it's a pretty safe bet it'll do the trick for your app.

An earlier post mentioned VWs. You'll find the same pump on everything that uses/used a CIS system. VW, Audi, Porsche, Volvo, Mercedes, some Saab and some other Euro cars including Bentley and Ferrari.

If I didn't have a pump, and I was OK with an external unit, I wouldn't consider any other pump even if it was free.

Geoff :zoom:


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PostPosted: Thu Jul 22, 2010 12:34 am 
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wkeeling wrote:
...I use the in tank pump was that I wanted to use the Miata gauges and the fuel level sender was a different than most and I could not find an aftermarket replacement. I just cut the old tank up and used the flange (also used the vent flange, one way vent valve and filler neck fittings and check valve).

William, could you give us pix? Or a link to your build log if it's already in there? And what tank did you use? Any extra gaskets?

I've done similarly but don't feel my system is ready for prime time yet. My main grumble re in-tank fuel pumps is it's hard to put the slosh foam around them. And I just cut the flange out of the tank with a plasma cutter...huh? Yes I know it's a gasoline tank, but it doesn't have any gasoline in it when I do it, the fuel pump is removed first, and all the other accessories, so the tank is well vented and I leave it outside and inverted overnight after I've disassembled it; I really don't think it's a problem, now that gas cutting torches are out of fashion.

[an important edit: just because I don't think it's a problem doesn't mean it isn't a problem! See Ol' Rowdy's post two below this one. Please don't blow yourself up on my say-so (don't forget, Danger is my middle name) and remember that if this came to a vote, most experience welders would say "Don't do it!"]

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PostPosted: Thu Jul 22, 2010 8:55 am 
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botbasher wrote:
Miatav8,MstrASE,A&P,F wrote:
.... I would be comfortable using the P37 with a 180hp/175tq VW 1.8L turbo.....
Thanks for digging those out for us.

60 psi.this.. I realize they are trying to sell parts, but if 1/2 of what they say is accurate, it's scary to a performance oriented mind!

KS


I thought you were on the fence about going NA or a stock turbo, which is why I suggested the P37 for those apps. You can still use the bracket with a pump that meets the flow requirement. If you know the flow requirements at 60psi, I'm sure one or more of these walbros exceeds it. Click the individual part numbers for flow charts and dimensions. AN6 fittings are available that screw directly into the Walbro.


http://www.expressfuelpumps.com/walbro- ... c-984.html
http://www.autoperformanceengineering.c ... _pump.html

Is the normal operating pressure of the VW 60 or are you raising it from around 45? If so, I wouldn't raise it if the pump is capable of the required flow at 45.

IMHO, the 5 examples in the link are pure salesmanship. Some designs are more efficient than others but the bottom line is the performance requirement. The pump should meet the requirement and not exceed it greatly, since the down side can be starvation from the gravity feed and heating and foaming of the fuel.

My point in bringing up the ford pump is to provide a cheap option to protect the pump for those who don't feel comfortable modifying an aftermarket tank to accept the oem assembly or just don't want to.The internal tank system is hard to beat.

Thanks for the corvair powered aircraft link.

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Last edited by Miatav8,MstrASE,A&P,F on Fri Jul 23, 2010 6:29 am, edited 1 time in total.

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PostPosted: Thu Jul 22, 2010 9:41 am 
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JackMcCornack wrote:
....And I just cut the flange out of the tank with a plasma cutter...huh? Yes I know it's a gasoline tank, but it doesn't have any gasoline in it when I do it, the fuel pump is removed first, and all the other accessories, so the tank is well vented and I leave it outside and inverted overnight after I've disassembled it; I really don't think it's a problem, now that gas cutting torches are out of fashion.
I've done this with both gas and plasma, but on tanks just pulled from a vehicle.

Empty the liquid from the tank and then you flood the tank with Argon (Nitrogen works too, but since we had TIG Argon was handy!), keeping a small positive flow going, you remove one leg of the triangle and a fire isn't possible. We were unsure of the flow rate needed at 1st, but found one filled, only a small maintenance flow is required if you keep the tank oriented correctly. Argon is heavier than air so keep all the openings at the top and "walla" a tank of fire proof Argon.

Not a suggestion for the weak of heart, but when the need arises... you gotta do what you gotta do!

KS

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PostPosted: Thu Jul 22, 2010 5:17 pm 
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You guys can go on cutting into tanks that had fuel in them
- but -
Years ago at my local junk yard there was a car that had been there for at least 5 years with the inspection cover and the filler hose on the top of the gas tank removed. There was no liquid fuel in the tank because the guys in the junk yard siphon the gas out of the junk cars to run the vehicles they use in the yard..

One of the workers was using the flame wrench to cut some metal loose under the tank and he accidentally cut into the tank which EXPLODED! He survived but it wasn't pretty. I would imagine that the heat caused the sludge or varnish in the tank to vaporize and the fumes exploded.
---

About the in-line pumps overheating, originally I was using a MSD #2225, 125#/" max, 43gal/hr, 7 Amp fuel pump which had enough GPH flow to run a Nascar engine. As other people have described it was -very- noisy. I also have an internal pump from a Mazda MPV which I thought I might use.

Here is a comparison of the Suzuki GSXR pump to the MPV pump. The MSD is even larger than the MPV pump.

Image


The point of all this is that while the fuel will cool the pump I don't think the lack of fuel is the only reason why an external pump might overheat. The typical 12V charging system is set for ~14.1V. If you are drawing 5 or 6 amps because of high fuel flow and/or a high pressure setting the pump is dissipating 70 to 84 watts of heat (of course some of the input amps are used to pump the fuel). The fuel will carry some of the heat away but the typical external pump I've seen is usually not out in the air stream so it has limited external cooling. Over a period of time the high heat can damage the motor windings if they aren't made with high temperature insulation. Even the motor on my electric water pump is rated at a lower temperature than the coolant it is pumping! :roll:

As Miatav8 et. al. pointed out ..........
Many (most?) of the accessory "high output" pumps are very overrated for most of our use considering that we run 12 or less gallon gas tanks on normal roads. Does your engine really require a pump that can empty the tank in 15 minutes? If the stock pump ran a car that weighed more than twice the typical Locost weight it should run a Locost.

The Suzuki flow test (minimum) is only 1.2 gal/hour. The adapter might have a restriction to cause some fuel pressure to exist.

Also, I'm pretty sure the pressure regulator on the internal pumps is set to a higher pressure than the one that is usually mounted on the engine fuel rail. In affect the internal regulator is a safety dump valve.

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