Walbro 340 vs TT340 (Aeromotive 340)

[Blazer406]

First, this is a long post..... so read on if interested.

My goal here is to present in-car flow tests between these two pumps. Fuel lines are stock. Pump has been hot-wired. Flow tests were done by unhooking the return line down by the frame near drivers side motor mount and aiming end of the line into a 2.5-3 gal graduated "car-wash" bucket I got from Wal-Mart. I have the battery hooked to a battery charger to simulate the alternator running as it would normally be while driving (or racing). I have a Accufab adjustable FPR on stock rails. I have a Snap-On Fuel pressure gauge hooked up on the end of the stock fuel rail.

Pump # 1 is a Walbro 20000169 (I'm told this is/was the same pump as the ones Walbro used to modify the base for the buick application that everyone refers to as the Walbro 340) The only difference is the foot of the pump was changed so an off-the-shelf pump would work for the buicks instead of modifying the base of ford pumps.

Pump # 2 is a TurboTweak 340. I'm told these pumps are basically the Aeromotive 340 everyone wants.... but comes in a plain white box. The are supposed to flow exactly the same as the Aeromotive.

Test # 1 was with Pump #1 installed in my GN... as I began running some flow tests yesterday to chase a high BLM on my TT 6.0 WB chip. I am also running 80# injectors and feel there should be enough flow @ boost to supply injectors with enough fuel to get to 80% duty cycle or more.

Regulator adjusted up until the gauge showed 70 psi (this would simulate the flow the pump would be putting out at 27 psi boost if base FP was set to 43 psi)

Put a graduated bucket under the unhooked return line.

Put a sharpie mark at 1 gal and 2 gal to make it easier to see.

Bat charger hooked to battery and on 10 amp setting for 1st test

It took about 1 min 23 sec for the 1st gal and 2:58 total for 2 gal....

Changed bat charger to the 50a start setting and ran test again....

1:13 for the 1st gal and 2:28 total for two gal.

Ok.... Now for my math.

Per Wikipedia, gas has a density of about 6.07 lb per gal.

Assuming I need at least enough fuel to get to 80 % duty cycle.... I get....

Fuel required:
80#/hr x 6 cyl = 480 # / hr x 80 % DC = 384 # / hr

Fuel available:

1st case - bat charger on 10 amp
2 gal in 2:58 = 6.07x2 (lb) / 2.9666 (min) X 60 (min) / 1 (hr) = 245 lb / hr

2nd case - bat charger on 50 amps
2 gal in 2:28 = 6.07x2 (lb) / 2.4666 (min) x 60 (min) / 1 (hr) = 295 lb / hr

So if my math is correct, I don't have enough fuel to get those injectors to 80 % duty cycle at 25 - 27 psi boost.

At this point I changed fuel filter and re-ran the test and achieved identical results on the 50A battery charger setting (my fuel filter wasn't restricting flow which was good)

Not happy with the results, I swapped in the TT340 pump and re-ran the flow test @ the 50A setting (Test #2).

Test #2 - TT 340 with regulator still set to 70 psi and battery charger on 50A setting.

It took 1:50 for 2 gal.

Doing the math:

2 gal in 1:50 = 6.07x2 (lb) / 1.8333(min) x 60 (min) / 1 (hr) = 397 lb / hr

Now we are getting somewhere! If you refer above, I figured out I needed 384 lb / hr to achieve what many would refer to as the upper limit of what you would typically want to "push" injectors to. The school of thought is to step-up your injectors if you need more than 80% duty cycle. IMHO, 80's are large enough to get a full weight car into the high 9's before they will need replacing.... or quicker if you are using alky too.

Bottom line is there is a nice (simulated real-world) difference in the old Walbro 340 and the newer Aeromotive 340 style pump..... 102 lb/hr difference at 70 psi.....

I have not had a chance to drive and see if there is any issue with my return line being too small with the new pump. The paperwork that comes with the pump states that some people have problems with the pressure being to high at idle. I set mine at 45 psi base fuel pressure just fine with the return line hooked up and flowing back into the tank without the car running. I have not checked the FP yet with the car running and vacuum line hooked up..... I will update this thread when I have driven the car more and checked the FP more.

Hope this helps some people.....

 

[DavzGN]

First problem I see with your test is that you are testing volume to your return line. You may have restrictions to your return line that doesn't occur for the fuel rail. Second problem is how accurate your bucket is. My father-in-law has two plastic water jugs that are identical and one says 4gallons and the other says 6 gallons. So unless you did some testing to verify the marks in the bucket your test only show the percentage better one pump is over the other.

David

 

[Blazer406]

First problem I see with your test is that you are testing volume to your return line. You may have restrictions to your return line that doesn't occur for the fuel rail. Second problem is how accurate your bucket is. My father-in-law has two plastic water jugs that are identical and one says 4gallons and the other says 6 gallons. So unless you did some testing to verify the marks in the bucket your test only show the percentage better one pump is over the other.

David

The bucket has marks for every quart and gallon on one side and liters on the other side. I believe it to be accurate. It would be very easy for me to verify with a measuring bowl used for cooking, but I believe the marks to be accurate.

The test also flows through the return line at least down to where it goes into the frame rail. This is real-world tests. I am sure you can get slightly higher flow results with the pump itself sitting in the bottom of a 5 gal bucket and a short piece of line running through a pressure gauge and some adjustable regulator. The premise here is to test the system as close to what you have hooked up in-car. In theory, the regulator adjusts so that the one side of the regulator maintains the fuel rail pressure constant... at whatever you set it at. Any "back-pressure" from a restriction in the return line will cause you to adjust the regulator lower to compensate. Bottom line is you are testing the "system".... not isolating to test one component of the system. Unless you are planning to size your return line up to -6AN with smooth bends back to the tank, why would you test it that way? I wanted to flow the system through the stock lines....since that is what I am running.

 

[jasjamz]

Yery Nice! Are the TT340s larger than the Walbros?

 

[87GN_70GS]

Great test! One piece of info I would've liked to have, only for my curiousity, would be the voltage at the pump...with a voltmeter connected as close as possible to the rear most pump connection and record the value at the 2 charger settings.

 

[Blazer406]

Yery Nice! Are the TT340s larger than the Walbros?

Not that I noticed.

Main difference I noticed is the sock is much larger...and the pump suction diameter where the sock goes on is probably almost twice as big. The instructions say to not use the stock rubber mounting foot as it will interfere with the pumps operation. My guess is the suction wouldn't even stick through the hole in the bottom if you left the rubber on the bottom.

 

[Blazer406]

....snip..... Second problem is how accurate your bucket is. My father-in-law has two plastic water jugs that are identical and one says 4gallons and the other says 6 gallons. So unless you did some testing to verify the marks in the bucket your test only show the percentage better one pump is over the other.

David

I have a pic.... but I didn't want to host the pic myself.... not sure why I can't insert images directly in the post anymore?

I used a Pyrex 4 cup (1 quart) measuring cup and filled it up 8 times and it was right on top of the 2 gal mark on the inside of the bucket. I would say the bucket is close enough for the purpose of this test.

 

[jasjamz]

Not that I noticed.

Main difference I noticed is the sock is much larger...and the pump suction diameter where the sock goes on is probably almost twice as big. The instructions say to not use the stock rubber mounting foot as it will interfere with the pumps operation. My guess is the suction wouldn't even stick through the hole in the bottom if you left the rubber on the bottom.

Thank you, Good thread as always!

 

[Nick Micale]

I would be very interested in how well a DW pump would do in this test? Since you are comparing pumps in the same environment and test set-up, the performance/flow results would be valid.

If you are willing to test a DW, I can ship you a pump, and will pay for the shipping both ways?

 

[kidglok]

I would be very interested in how well a DW pump would do in this test? Since you are comparing pumps in the same environment and test set-up, the performance/flow results would be valid.

If you are willing to test a DW, I can ship you a pump, and will pay for the shipping both ways?

when the idiot at the gas station filled my car with regular, i pumped mine out from the fuel rail. took about 2 1/2 minutes for 5 gallons

 

[AZMotorgod]

Great offer Nick, I would love to see the times for the DW too.

 

[Blazer406]

Never text your wife while simultaneously replying to a post on the board, and trying to get a wet flopping 2 yr old out of the bath tub..... Multi-tasking at its finest....

 

[Blazer406]

Nick, I'd be glad to do the test. I'll pm you my address?

 

[Blazer406]

I'll do the TT340 test over the day I swap the DW pump in there to verify the results back again on the TT 340 pump.

I'll also see what the voltage is at the pump during a test with the battery charger on the 50A start setting.

 

[mgmshar]

Finally, someone getting actual data from a car with these pumps. Great test!

From a fellow ME...

 

[Blazer406]

when the idiot at the gas station filled my car with regular, i pumped mine out from the fuel rail. took about 2 1/2 minutes for 5 gallons

I'll put a few more pieces of data out there. Before I removed the Walbro pump.... I backed the pressure down to 65 psi and ran a 2 gal test.... then 60 psi...... again.. flowed 2 gal and timed it. The results show how the pumps volume output climbs as the pressure goes down.....which is exactly what I would expect.

I'll re-state the 70 psi data for comparison's sake.

Walbro @ 70 psi - batt charger on the 50A setting
2 min 28 sec for 2 gal = 295 lb/hr

Walbro @ 65 psi - batt charger on the 50A setting
2 min 6 sec for 2 gal = 346.9 lb/hr

Walbro @ 60 psi - batt charger on the 50A setting
1 min 57 sec for 2 gal = 373.5 lb/hr

60 psi would simulate 17 psi boost with a 43 psi base fuel pressure.

The volume output has dropped over 20% with a 10 psi rise in fuel pressure. This goes to show you how important the fuel pump is when you begin to run higher boost..... just because it flows good at 43 psi doesn't mean anything about a particular pumps capabilities are going to be at higher pressures.

One quick compare.... the old Walbro 307 was considered a 255 LPH pump back in the day..... so was the Walbro 340...... both 255 LPH. The 340 looks (on a flow chart) like a different pump at 70 psi than the 307...... even though they are both 255 LPH pumps. My point is, you really need the flow data from the pressures the pumps will have to put out to run at the boost level you run at. That is why most (extremely high boost) racers opt for a large Weldon external pump. They really are in another class when it comes to high pressure fuel pumps.

 

[Blazer406]

After piddling with it some more... I do have FP issues at idle.... with everything cold... it will only adjust down to about 45 or 46 psi..... and seems to not want to go any lower. I can crank the car and it runs fine... but hooking/unhooking the vacuum line yields no change in FP..... if I cut the base pressure up to 50..... and then hook the vacuum line up... it will pull it back down to 45 - 46 psi.... Not sure what to do next now. I was not wanting to mod my return line. The closer to factory appearing, the better to me. I'm not a huge fan of all the bling if it doesn't add HP. I'd perfer it to look mostly stock and run high 9's....

 

[87GN_70GS]

After piddling with it some more... I do have FP issues at idle.... with everything cold... it will only adjust down to about 45 or 46 psi..... and seems to not want to go any lower. I can crank the car and it runs fine... but hooking/unhooking the vacuum line yields no change in FP..... if I cut the base pressure up to 50..... and then hook the vacuum line up... it will pull it back down to 45 - 46 psi.... Not sure what to do next now. I was not wanting to mod my return line. The closer to factory appearing, the better to me. I'm not a huge fan of all the bling if it doesn't add HP. I'd perfer it to look mostly stock and run high 9's....

That's not all bad news, depending on what ECM you're running. The stock ECM will compensate once in closed loop. Open loop (i.e. cold) idle may be a tad rich. Other ECM (FAST, EZ EFI, Speed Density, ME, etc may not have a problem cold).

I would not recommend 50 psi base. You risk reducing pump output at WOT for the sake of idle/open-loop (unless you have tiny injectors and fuel demand is low).

 

[Blazer406]

That's not all bad news, depending on what ECM you're running. The stock ECM will compensate once in closed loop. Open loop (i.e. cold) idle may be a tad rich. Other ECM (FAST, EZ EFI, Speed Density, ME, etc may not have a problem cold).

I would not recommend 50 psi base. You risk reducing pump output at WOT for the sake of idle/open-loop (unless you have tiny injectors and fuel demand is low).

I only temporarily bumped the FP up that high to see if the diaphragm was still working and it would still pull the FP back when vacuum was applied....

It is back on 45 or 46 psi base now....

I should have enough pump to keep up now.....

 

[Bent6]

I installed an Aeromotive "Stealth" 340 pump on one of my street cars a while back after the previous Walbro began to fail. I modified the hanger a bit so that I could still retain the rubber isolator without interfering with the pump. I knew this pump flowed well but it's nice to see some verification of the advertised flow numbers.

One note of caution.......as this pump is more powerful the electrical requirements are also higher. A "hot wire" setup is fine but special attention should be paid the the wiring after that point going through the stock harness into the tank sending unit/pump hanger. Mine burned the thin gauge 25 year old ground wire off the pump hanger. I rewired mine with heavier gauge power and grounds going into the tank. I recommend anyone using this pump to upgrade the factory in-tank wiring.