krazy_1st_gen

i am working on my TII in FB project and need to know wut these two are for. please help. thanks

alwayssideways

my guess is the first one is the fuel pump realy and resister, and the second is the knock box module

RotaryResurrection

iTrader: (8)

1) 86-87.5 fuel injector resistor pack, bumps ~3.5 ohms of injector impedance up to a safer ~13 ohms at the ecu. 87.5+ cars did not use one, as those injectors are all ~13 ohms themselves.

2) motor failure box. Serves no important function, leave it alone.

krazy_1st_gen

so is the injector resistor pack the same as the resistor relay?

RotaryResurrection

iTrader: (8)

No. The resistor relay he referred to above varies fuelpump voltage between 9 and 12vdc to attempt to achieve better gas mileage. IT is mounted behind the passenger headlight, and is a somewhat similar but larger looking unit.

Neither of these parts should be screwed with by persons not knowing what they're doing. Just leave well enough alone.

hIGGI

iTrader: (7)

Never figured what Motor Failure Box does, probably only what it does have in the box :P

krazy_1st_gen

okay, so now i need the resistor relay. anybody have one for sale? im almost done with the car but still missing some parts. will post again as soon as i find out what im missing. thanks for the help guys

RotaryResurrection

iTrader: (8)

Run fulltime 12vdc to the fuel pump from a switched output in your cabin fusebox, and call it an upgrade. IT costs less and can be beneficial to modded turbo cars.

NZConvertible

How can bypassing the resistor be beneficial to turbo cars? Instead of full voltage only at high load you get full voltage all the time and as a result use more fuel when you don't need it. Full-load fuel delivery is unchanged, so I can't see any advantage, only a disadvantage.

KompressorLOgic

iTrader: (6)

seriously tho wtf does that " motor failure box do anyway" i got no clue could someoen explain what it actaully does.

RotaryResurrection

iTrader: (8)

Because even when at high voltage, you only get 12.05vdc to the pump. WIth this mod, you can push 14.3vdc to the pump, if your charging system is capable of producing that, which it should be. The way I figure it, that's a good 2-5% more volume from the pump...every little bit helps on a modded car, and it's a free mod. We didn't buy this car for gas mileage anyway, so what's the point of a dual voltage setup?

NZConvertible

I'm sure you're aware of the full rewire that relocates the relay/resistor to the rear and keeps it fully operational, while still reducing the voltage drop between the battery and pump to virtually nil. I've done this and know how effective it is. The fuel pump voltage is still reduced at times of light load. Bypassing this will simply wasting gas unnecesarily. I bought my 7 for performance too, but I didn't buy it to throw away fuel for no good reason. It's not like rewiring the fuel pump properly is particularly difficult or time-consuming.

RotaryResurrection

iTrader: (8)

I guess I'm just a fan of KISS...keep it simple, stupid

I figure 1 wire being run is much more reliable, and simpler than 4, or whatever the "proper" rewire requires. I've seen it in person and in writeups, just never bothered doing it.

My mildly modded FD with walbro and full voltage fulltime rewire made 21mpg on the last road trip...I'd bet most stock FD's with stock fuelpumps and stock fuelpump resistors couldn't match that. I don't think it matters one way or another in PRACTICE, though it sounds like a great idea in THEORY. I guess I'm just a real-world kinda guy.

NZConvertible

The change in AFR from manually switching the fuel pump voltage at idle has been measured and documented, and was not insignificant. I imagine the percentage change under other load conditions would be a bit less but still there. That's real world enough for me.

As for unreliablilty, the stock set-up has proven itself to be extremely reliable, and the reliability of a full rewire depends entirely on workmanship. I consider mine to be reliable enough to never give it a second though. I certainly don't think a single-wire set-up would be "much more reliable" because that implies a reliability problem with the stock set-up.

BTW, the best roadtrip mileage I've got in my older and less aerodynamic FC turbo 'vert was ~22mpg, with the rewired fuel pump cruising along at ~10V most of the time.