Erik Gross method revisited

[Greg E]

I'd be much more willing to help you do it yourself, but if you really wanted me to build it, I suppose it could be arranged...

Haha, I can make one. If you could make up a wire schematic, I'd greatly appreciate it! Where can I get the relays from?

[RealMcCoy]

I already posted a diagram of my system:



Let me try and clarify what it is we're doing and what the diagram represents...

The relays I used were standard Bosch style relays. You can pick them up just about anywhere. They are all plainly labeled with the pin #'s 30, 87, 87a, 85, and 86.

Pins 85 and 86 are the signal circuit, when current flows through them, the relay is engaged. Pin 30 is the common high current post, when the relay is not engaged, it is connected to pin 87a, when engaged, it's connected to pin 87.

The circuit labeled "MPFI" is the fuel pump power source from the factory MPFI relay. We're using that to turn on the hotwire relays.
The circuit labeled ECU is the factory signal from the ECU to engage the resisted mode. The ECU grounds this circuit to engage the relay. We're pretty much duplicating the factory setup here.

So what we do is feed power from the MPFI relay to pin 85 on BOTH our relays, the hotwire relay pin 86 is grounded, so it automatically engages whenever the MPFI is powered up. the resistor relay pin 86 is grounded by the ECU, so it will engage when the ECU switches to non-resisted mode. The power out of the hotwire relay is split into two parallel circuits, one resisted, one not... The resisted leg is hooked to pin 87a of the resistor relay so that any time the relay is NOT engaged, you have resisted power. The non-resisted side is hooked to pin 87 so that when the ECU engages the relay, you have non-resisted power out pin 30.


This is the factory system we're replacing:





Let me know if I can clarify anything further...

[RealMcCoy]

Thank you to whoever fixed the thread title...

After several edits and second guessing my own thoughts, I think I finally clarified my clarification.... LOL

[green-lantern]

Good read, I admire the stubborn never let it beat you attitude that drives you to do the research. When I want to know something or why I got the results I did I pretty much won’t quit until I get the answer.

Good Job!

[i3igpete]

The moral is, no need for the AFPR.

the moral of the story is, twin stock FPR's...

[green-lantern]

And two throttle bodies

[CoreyB]

Dont listen to them, you will break a ringland.

[aaronatstate]

the moral of the story is, twin stock FPR's...

GTFO now Really we just need ram air, that way we'll make boost with an N/A!

[mb7050]

I was thinking of doing something similar because I hated the noise that walbro makes when hotwired but then I bought a denso fuel pump and an afpr ..

[KeithMac]

I'd be much more willing to help you do it yourself, but if you really wanted me to build it, I suppose it could be arranged...



That's what I usually recommend, but there are downsides... If you drive your car on long trips and lots of highway use, slowing the pump down will significantly prolong it's life. There is also the all too common complaint of the aftermarket regulators leaking, causing long crank times.



You have any way to test the current draw on those things?

The nature of an electric motor is that it will increase it's current draw as it's slowed down. If you bring it to a full stop, it's a dead short. This is why you will see starters and battery cables turned to bacon from a depleted battery, it goes against all logic until you examine the nature of a segmented armature electric motor.

In my above data, those resistors were only allowing 7.5 amps each through them with the pump slowed down to under half normal speed. It sounds like two resistors is still too much for dual pumps.

The Walbro has significantly less current draw under normal operation than a Denso, but I would theorize that it's much less tolerant to being slowed down. The Denso has 12 armature segments, while the Walbro has only 8. You get much less leeway for speed changes before you approach dead short status.

In your situation, I'd be tempted to experiment with an injector resistor pack... You'd have 6 separate segments you could run in parallel one at a time until you found the sweet spot.

I had 2 Walbros in parallel powered by 2 Resistor packs in parrallel, I have another Resistor so I could try 3 in parrallel I suppose.

Looked at the injector resistor pack but it doesn`t look substantial enough compared to the pump ones?.

It never dawned on me that they would inrease current draw as they slow down but it makes sense, have split many motors down before for repair so I`ve got a good understanding of what`s inside.