While the folks at the machine shop drag their feet, I might as well install the new fuel pump..... pulled the pump and found that a Pepsi bottle is perfect to temporarily seal the tank opening:

Then, discovered the pleasant surprise - the VR4 turbo pump is a direct drop-in for the Montero pump <img src="/forums/images/graemlins/kewl.gif" alt="" />

The filter retaining clip must be pried off (there's a new one in the package) if you want to use the original Montero filter:

- but the instructions say the pump warranty is good only if the supplied new filter is installed, so that's what I used:

used a new flange gasket:

and mounted the new pump with a new piece of hose and new clamps (all packaged with the pump):


And it's now installed in the tank - just need to cut the harness feed connector and rewire it to the MegaSquirt relay board. Voltage here is critical, the OE wiring is waaaaay inadequate and so is the wiring supplied with the MegaSquirt harness. Since I don't know the exact amperage draw of the pump, I'll allow for a maximum of a 3% voltage drop at a 15A maximum current guesstimate and run AWG 8 wire. That should take care of the pump's electrical requirements under boost pressure. <img src="/forums/images/graemlins/kewl.gif" alt="" />

Hopefully, this pump will be the best $110 I've spent so far.

Frank

Does it hafta be Pepsi??? <img src="/forums/images/graemlins/barf.gif" alt="" />

I kid, I kid <img src="/forums/images/graemlins/smile.gif" alt="" /> Sounds like a fun day, Frank. <img src="/forums/images/graemlins/cheers.gif" alt="" />

#8 sounds a hair large, Frank. NEC states that for 15 amps, #14 is called for. (Actually capable of more depending on insulation). # 12 would allow for enough leeway. Capable of 35 amps (but restricted to 20 amps in NEC).

Also, go to West Marine ( or other boating store) & get waterproof butt splices for everything. Much more expensive, but much better.
If you want an outlet for them cheaper, I can PM you one. Need to buy quantity, but worth it in the long run.

Ed

Ed -

Yes, it's large by automotive standards for N/A engines..... but when you add boost, the fuel pressure regulator causes the pump to work harder and draw more current. As you know, with increased current comes voltage drop, depending on wire size and run length.

I see that Jeff Lucius checked the VR4 Denso pump at 15psi boost and found only 10.2-10.5v at the pump. I don't know what size wire is used, but it's probably AWG14. He does say that the run is about 12'. He does not mention testing for current draw, but in the article claims that the Denso pumps can draw more than 16A:

Stealth 316 page

According to tests run by RC Engineering, the Denso pumps also appear to be power hogs. Below is a link to the results of tests run on various pumps at 13.5v and 16.5v. I don't want to use a voltage booster, so I paid close attention to the area around 50psi on the charts, where my pressure will likely be under boost. If you look at the tabs at the bottom of the page, you can select the different pumps tested:

Pump Tests

I'm running a longer route than OE... up the driver side and across the top of the firewall to the relay behind the passenger headlight..... it's ~15' from the pump to the pump relay. If I run 14AWG, the voltage drop is 11.7% to the pump. However, you need to figure the voltage drop of all of the wires in the circuit - battery to relay/relay to the pump. Making it more complicated than perhaps it needs to be is the maximum wire size that will fit in the connector on the MegaSquirt relay board.

Unless I can step up a size in the relay board, I'll run 14AWG from the battery to supply the entire relay board (including the ECU). If I start with ~20A total (estimated) through that wire for 2', voltage drops from 13.6v to 13.4v at the relay board. 14AWG will run from the relay board for a foot or so before it's spliced into a larger wire to make the 15' run to the pump - so that's a loss of another .1v or now down to 13.3v. If I run 14AWG all the way to the pump, voltage will drop to 12.0v on a 15A draw.... certainly adequate. But, if I run 8AWG, the pump should see 13.0v minimum. <img src="/forums/images/graemlins/kewl.gif" alt="" />

Granted, that's not a lot of difference..... and the pump may never draw 15A, but it is a difference - and after my previous experience with the fuel system, I want as much protection as I can reasonably get.

In looking at the OE fuel pump electrical system and knowing the OE fuel pump was tired, I suspect that the entire system was inadequate - old pump, small wiring, restricted fuel flow and high pressure demand under boost causing more current draw causing reduced voltage and less volume = disaster!

I did go to West Marine - and got 8AWG sheathed duplex marine wire.... I know it's overkill (and very expensive).... but I know pump voltage ain't gonna kill the engine.

For splices, I use a metal sleeve (strip them from a standard butt splice)... crimped, soldered and covered with shrink tubing - adhesive filled where possible. <img src="/forums/images/graemlins/kewl.gif" alt="" />

Frank

Have you measured this?
We run both 14 and 12Ga and this works fine with a Bosch 044 pump on 670HP engines that use 80 PSI for base pressure and a 1:1 rise from there. Most of the Porsches I have setup ran 14Ga.

Awh man. good job on that. <img src="/forums/images/graemlins/smile.gif" alt="" /> <img src="/forums/images/graemlins/smile.gif" alt="" /> You can do electrical work with me ANYTIME!!!

Charlie -

No, I haven't measured it, but the electrical resistance/length/voltage/current relationship is available in several calculators to save the effort of doing the mathematical calculations.

This calculator is based on 140*F, but it's what I used for the calculations:

Voltage Drop Calculator

Here's another one that shows the voltage drop to be 9.73%, but it's provided by the American Boat and Yacht Council and I assume it references marine grade wire... which has about a 10% higher size/load factor, partly because of the hot environment in an engine compartment and degradation in a salt environment:

ABYC Amperage Tables

This one is also from a marine source and shows only a 4.7% loss.... but at 30*C:

Manray marine

Here's another from Advanced Power Products - a supplier of my Concorde AGM battery - same as the ABYC results above - not surprising, since the solar cells are commonly used in marine storage applications:

Advanced Power Products

I don't know what the Bosch pumps draw.... and I'm not saying the Denso pump won't run at a reduced voltage, but if it does, it'll draw more amperage - and how much more is an unknown to me. The pump does run more efficiently at higher voltage.... and particularly at that run length and with the small (5/16" O.D.) fuel line, I just want to take that worry out of the equation..... once bitten, twice shy.

I've never run more than AWG14 either, but this time I dang sure will. <img src="/forums/images/graemlins/kewl.gif" alt="" /> It might have been simpler/better to increase the fuel supply line size to 3/8" - maybe I should do that as well.

EDIT:[The above was stated incorrectly - voltage reduction won't cause an increase in current - amperage will instead drop, but so will flow. Also, "efficiency" is used incorrectly - "increased supply" was the intent with higher voltage.... sorry for the confusion]:EDIT

Frank

Charlie -

Note the Endyne information about the Bosch pump:



Endyne

Lucius seems to agree with the data:



It appears that Bosch pumps are more efficient than Denso. On the Porsche, where is the battery - front or rear? What size wire runs from the battery to the relay? How long is that run? How long is the run from the relay to the fuel pump? If those other wires are large and the run to the pump from the relay is short, you can get away with a smaller wire size without sacrificing any pump efficiency - particularly with the more efficient pump.

Frank

I wired mine with 8ga. Just dumb luck, I guess...

Not at all - particularly if you're gonna turbo that thing..... but it really depends on the pump efficiency and somewhat on fuel line size.

If you look at the test results on the VR4 Denso pump that I have, it's pretty bad compared to the larger pumps - which is why the VR4 guys replace their pumps if they run over 10-12psi boost pressure. It seems to me that their problem with the pump is a combination of things - the wire size, length of run, a resistor in the circuit to drop pump voltage at idle, 5/16" fuel line and length of run, boost pressure and an inefficient pump.

I need about 1600 cc/min or 96 l/hr fuel delivery... add a 30% cushion for pump aging/wear to make it say 125 l/hr. The bench test on the VR4 pump (in the comparitive graphs) showed it to be the worst of the tested group and only flows 150 l/hr at 50psi and 125 l/hr at 60 psi..... and that test was performed at 13.5v. <img src="/forums/images/graemlins/scared.gif" alt="" /> Granted, the pump tested was a used one and maybe a little tired, but it shows me that I'd better get plenty of voltage to it if I want enough fuel.

I wanted to use an in-tank pump that would fit without major modification and was guessing it would at least fit with minimal modification when I ordered the pump. I got very lucky with the direct fit, but the downside is a low-performance pump compared to the larger choices. However, it might be good enough to take me to 10psi if I ever want to try it.

Frank