And there's no reason to PWM it. I had stable idle fuel pressure with that super shitty AEM FPR. A fuel lab should handle it no problem.

 

This isn't lost on me. My SSR install here is mostly just to play with it for my own experience. It's entirely likely that I will fiddle with it for a while and then take the SSR and flyback circuit out of the car for another project later on. The real application for SSRs is cars using big fuel pumps who want to run the stock FPR and maintain idle quality.

 

I have a Walbro 450 in mine, and I can't say I ever notice it, apart from when priming.

 

Wired up the fuel pump hangar today. Ignore the extra hole that some dumbass drilled in the wrong place. I had an adapter to attach to the factory FPR flange, but decided to just cut it off instead for simplicity.






Just waiting on some sleeve to protect the external hoses and then I'll plumb in the new Fuelab FPR and filter.

 

Ninja edit before my response...

 

Those are nylon nuts, I have no idea if the are stable in gas.....do you?

 

Its supposed to be a bolt on one side and the nyloc nut on top




Not sure what andrew got

 

It's now a long set-screw with two nylocks. Nylon is OK. It's a thermoplastic which is fine for use with E85. Same with the acetal isolators. The o-rings inside the isolators are Viton and the thread sealant is Gasoila (PTFE-reinforced). Studs are stainless steel.

The only things I'm not sure about are the wiring to the pump itself and the OEM fuel sock. The OEM fuel sock is sort of required and I will have to replace it every couple of years, probably. The wiring is hopefully OK, since I was unable to source the bare Walbro-style connector (everyone just sells an assembled pigtail). If/when I go to a Walbro 450, that's a Metripack connector and I will use my own 10awg Tefzel-insulated milspec wire (same as what's in the rest of the wiring).

http://iqlearningsystems.com/ethanol/downloads/Ethanol%20&%20E85%20Material%20Compatibility.pdf

 

Replacement fuel tank lid? I've never seen a black one before, the only ones I've touched are gold cad plated.

Very nice though! Do want.

 

Maybe it's just dirty?

--Ian

 

Andrew, please check your email.

 

Looks very nice!

Good job, except for the dumbass part

I trust the sealed hole will not be included in production units, or is that an option port?

 

Getting there. Need to grab a couple of -6AN unions to finish the lower plumbing.

 

This is cool stuff.

Question, which may be answered somewhere ...

Are you guys bumping the gauge on the line running back to the battery when you are tying the FP directly to the battery? The increased current through that line will result in a voltage drop, may only be on the order of tenths of a volt, but when going to these lengths ...

That voltage drop will also play into the battery charge voltage. As the battery voltage increases (in the stock configuration) the charge current drops. This in essence negates the voltage drop due to charge current. Adding a 30A bias to the charge current will result in a constant voltage drop.

If addressed, rehash, sorry

 

I ran 10AWG (or equivalent in parallel) from the pump to the battery. Both negative and ground. Everywhere. Fuse holder, relay connections. Pump pigtail, etc.

 

Sure, but the run from the battery to (essentially) the alternator is now going to carry the additional fuel pump current. Under nominal operating conditions, the current in this line will flow into the battery (charging). The battery doesn't actually source much (if any) current to the car when running. It may provide hold-up power during periods of high load, but most of the power used to run the car is sourced by the alternator, at the main relay box.

 

Afaik the run from alternator to battery is much bigger.

Also the stock wiring is like 18 or 20awg. and runs under the dash.

 

Oh, I am not questioning the merits of getting away from the stock wiring at all for the Fuel Pump. I can't believe Mazda did it this way in the first place.

Maybe the precision schematic shown here will help with what I am describing. By tying the fuel pump into the battery, you are creating a voltage divider at the battery + terminal. Under normal operating conditions (battery charging) I have measured the voltage drop from the Main Fuse Relay box to the battery in the tenths of volts to 1 volt range. This is without the added load of a fuel pump. I eyeballed the stranded conductor count on my '91 at the battery, and it looks to be in the 8AWG range. I am sure somebody around here knows what it actually is. The drop across 10ft of 8AWG @ 30A is ~ 0.4V.

 

Oh, and I hate it when engineers identify a potential (unproven of course) issue without providing possible solutions ...

I think when I fix the Mazda fuel pump design flaw, I will run a dedicated line from the Main Relay box to the fuel pump. I will probably use the Air Bag fuse slot as well, it is currently unused. I don't really care if the fuel pump sees some voltage drop, it has downstream regulation that will compensate.

I think my biggest concern would be having the battery transition from charging to discharging more often. Typically, the battery should only discharge during cranking. With the added voltage drop due to the FP current, I fear it will be discharging more frequently, which is not ideal on several different levels.

 

Ah ok. Yeah I haven't measured voltage at the battery. My hope is that the battery will help alleviate that voltage drop when the alternator can't keep up if that makes sense. Because the alternator (at the battery) and battery are varying voltage sources. Whichever is highest should be the one "feeding" the pump.

Edit: I now see your post about why it is a concern.

Shouldn't the alternator be charging upwards of 13.5-14 volts. The battery should be 12.6ish. So unless you have a 1V drop over the run from the alternator to the battery it should be ok.