hardwiring fuel pump required?

[Pantera Chris]

Need a fairly quick answer on this if possible.

A few people have told me to hardwire my new Walbro fuel pump but my  mechanic who works on very high spec jap cars says it isn\'t really  required for the sort of power level ill be going for (320bhp ish /  stock injectors etc), although he usually works on Evos and Nissans!

Is hardwiring the pump REALLY required at my tune? If so, ill have to buy a kit in with a relay.

Thanks,
Chris

[philiwily]

If you check your voltage at the pump it will be less than battery voltage due to the circuit running around the car through relays, resistors etc . If your going for 320bhp on standard injectors your injector duty will be very high(90\'s%) but lower if your pump is pumping more fuel.
Plus it\'s not that big a job.
Note: The voltage at the pump on idle is lowered by a resistor so don\'t measure it then.

Phil

[Pantera Chris]

have done it now, thanks

[neil_jdmr]

Does it actually lower injector duty or just raise the voltage to the pump thus increasing rail pressure ?

Thanks

[philiwily]

The duty is controlled by the ECU, if the fuel pressure is raised after it is mapped the duty would stay the same but the air/fuel ratio would change(richer), this could be corrected by lowering the duty.

[neil_jdmr]

Just as I thought,

Thanks phil

[Pantera Chris]

Right, just finished. Its a piece of .... to do if you know how. I used this diagram although I didn\'t do the extra earth bit (splicing the black wire). I also didnt bother extending the original wires, just cut the red one in half and wired straight to the relay.

[turbotoaster]

it does make a difference and is worth doing, for example i needed to trim about 0.5 afr out of my idle map when i did this and also pulled some fuel out of the map to compensate throughout the rev range

[Pantera Chris]

Did you splice in the extra earth wire (shown from the thick black cable).

I guess this is just for extra stability?

[turbotoaster]

electricity works like a railway.

you can have 20 sets of tracks running into a station but if you only have 1 track leaving the station everything backs up and doesnt flow properly.

yes i ran a ground back to the chassis, since my battery was in the boot i actually used the same ground point as my main one off my battery.

Is you battery in the boot, i found a good place was on the left hand side of the boot where the plastic interior is bolted, scratch off the paint to get to the bare metal and hook up there.

ive maxed a set of stock injectors out at standard rail pressure at 360 flywheel bhp.
also ran 4x850cc with 20psi of boost on a stock pump......i wouldnt recommend that mind as that was more me learning mapping than anything else.

i would recommend no matter what bhp but not doign it is ok up to 330bhp id say, after that its up to around 370 flywheel bhp with a rewire, after that id change pumps

[Pantera Chris]

Thanks mate. The battery is in stock location. I have rewired as above to a brand new Walbro apart from the extra earth. Ill try and get this done if it makes a difference?

ps - have used the same earth point as you (rubbed the paint off first).

[turbotoaster]

well for the 10mins it will take to do it cant hurt, the better the circuit the more effiecient the setup.

walbro is a nice quiet pump so should be perfect for your needs, what are you planning on doing, just running it on twins for a while?

Havent decided how im going to wire mine up yet as im gonna be running 2x044s externally, luckily im gonna run them under the car else id go deaf!! means i can happily run at 20psi for a while then wont have to change when i go to big single

[Pantera Chris]

Yeah I need to get my arse in gear, I really do!!

Will be running stock twins at about 330bhp hopefully yeah. Just want to make sure there are no weak links! Already replaced leading coil and leads with new ones and now pump and fuel filter

[turbotoaster]

changing the fuel filter is a good idea, pain in the arse to do but defo worth it, you can have 1000 fuel pumps but if that fuel filter is blocked you just not gonna get the fuel you expect.

I heard you got the coil and leads from atkins over the water? what did they charge.

Im gonna run a seperate system with dynatek amp and coils, works out at £400 all in and with work with everything up 700-800bhp from what i can see, though i think it maybe a bit overkill for most people.

The biggest thing ive learned since tuning a rotary is intake temps, the lower you can get them, the lower the knock, the more you can push the engine, while that might sound obvious running a big front mount makes such a difference.

I got less knock at 20psi of boost with a big cooler than 14psi with a slightly upgraded stock mount cooler so get one if you havent already.

A cool rotary is a happy rotary

[Pantera Chris]

Coil cost me about £160 including shipping and customs.

Others have told me about intake temps too. Have a trust stock mount at  the moment but I really need to sort the ducting out as im running the  stock stuff. Hits about 35 degrees C on a run.