Author Topic: Need help, bigger injectors, rrfpr, or chip for supercharged m42  (Read 5241 times)

SkidMark

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Hi guyz
You may have seen my post in swaps turbos and build ups showing my almost completed supercharger setup. The fab work, the easy part for me, is done. Now comes the electrical, simple, just need to lengthen some harnesses, and the fuel management, not so simple..  I need help deciding what and how I need to manage fuel.
I have several sets of injectors in various # ratings, 19#, 24#, and 32#, all low impedance (mustang injectors).
Which set do you all think would be a good starting point? Should I purchase a rising rate fpr?? Or will the larger injectors flow enough fuel with stock dme and chip?? I plan on buying a wideband so I can monitor my air/fuel ratios but cant quite squeeze it into the budget now. I would like to fire the car up to see if it is even going to work but Im scared!! I dont want to melt this engine down!! What do you think?? Im thinking I might run with the 32# injectors and give it a shot. I figure it is better to be rich than lean?? Dont pistons melt in lean boosted conditions?? I am also wondering about timing retard and detonation. The e36 m42 has knock detection so I am hoping the stock dme can deal with timing to an extent?? I am only running 5psi boost so???? A little octane booster or race fuel might help too? I know race fuel burns cooler has less problems with detonation. I am hoping somebody has a dasc setup on their car and can give me some guidance. I guess a turbo setup would probably be the same as far as fuel goes.. more boost more fuel, so any help or ideas will be greatly appreciated!! Thanks for reading my babbeling....Skid
1970 BMW 2002, 1988 BMW 325ix, 1979 BMW 320i m42 powered race car, 1969 BMW r75 cafe bike, Greasy fingers, Empty bank acct, Pissed off wife, Unhappy dog, Filthy garage.

SkidMark

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Re: Need help, bigger injectors, rrfpr, or chip for supercharged m42
« Reply #1 on: October 13, 2014, 02:55:12 PM »
I think I am going to buy a rising rate fuel pressure regulator (fmu), and start out with the 32# injectors. I will set the fuel pressure low to fool the dme into thinking it has the stock 19# injectors, (the dme is stupid and has no idea that the injectors and fuel pressure have been changed) so, it should be fine at no boost situations and drive "normal". When boost comes on, the rrfpr will increase the fuel pressure and the bigger injectors will start flowing more fuel.
Heres an example..

a 36 #hr injector at 15 psi fuel pressure will flow 19#hr 80% duty cycle
a 36 #hr injector at 43.5 psi fuel pressure will flow 34.3#hr 80% duty cycle

The stock m42 injectors are pretty close to 19#hr
« Last Edit: October 13, 2014, 04:32:08 PM by SkidMark »
1970 BMW 2002, 1988 BMW 325ix, 1979 BMW 320i m42 powered race car, 1969 BMW r75 cafe bike, Greasy fingers, Empty bank acct, Pissed off wife, Unhappy dog, Filthy garage.

bmwconnect

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Re: Need help, bigger injectors, rrfpr, or chip for supercharged m42
« Reply #2 on: October 16, 2014, 08:41:58 AM »
unless you plan on changing the fuel lines completely I would move away from using a RRFPR. They are known to make fuel pumps fail and burst fuel lines ;)  Get a proper tune for bigger injectors and you will be good.

Cheers
BarrieM/// BMW Tuner - OBD1 M42,M30,M20,M50,S50 Chips & OBD2 M44,S52,M52 Flashes
EMAIL:midnight-tuning@rogers.com
http://www.facebook.com/Midnight.Tuning.Solutions
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SkidMark

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Re: Need help, bigger injectors, rrfpr, or chip for supercharged m42
« Reply #3 on: October 16, 2014, 10:55:23 AM »
Barrie,
I have been trying to get in touch with you for a year! Will you PLEASE CALL ME!!! 775-342-4279
1970 BMW 2002, 1988 BMW 325ix, 1979 BMW 320i m42 powered race car, 1969 BMW r75 cafe bike, Greasy fingers, Empty bank acct, Pissed off wife, Unhappy dog, Filthy garage.

bmwconnect

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Re: Need help, bigger injectors, rrfpr, or chip for supercharged m42
« Reply #4 on: October 16, 2014, 02:10:15 PM »
I like to keep records so please email me direct at info@midnight-tuning.com

Cheers
BarrieM/// BMW Tuner - OBD1 M42,M30,M20,M50,S50 Chips & OBD2 M44,S52,M52 Flashes
EMAIL:midnight-tuning@rogers.com
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doitover

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Re: Need help, bigger injectors, rrfpr, or chip for supercharged m42
« Reply #5 on: October 17, 2014, 10:25:49 AM »
I have a Downing Atlanta on mine. The people that did it used larger injecotrs, rr regulator, and some chip.
It idles well and is okay as far as I can tell at near WOT. It gets 30 MPG on the highway.
It pings/knocks loaded at part throttle though. It also gets around 20MPG in town. I'm sure it could be
tuned better.

bmwconnect

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Re: Need help, bigger injectors, rrfpr, or chip for supercharged m42
« Reply #6 on: October 20, 2014, 08:23:11 AM »
I have a Downing Atlanta on mine. The people that did it used larger injecotrs, rr regulator, and some chip.
It idles well and is okay as far as I can tell at near WOT. It gets 30 MPG on the highway.
It pings/knocks loaded at part throttle though. It also gets around 20MPG in town. I'm sure it could be
tuned better.

It should never ping if it's tuned correctly . Be careful ;)
BarrieM/// BMW Tuner - OBD1 M42,M30,M20,M50,S50 Chips & OBD2 M44,S52,M52 Flashes
EMAIL:midnight-tuning@rogers.com
http://www.facebook.com/Midnight.Tuning.Solutions
Midnight YouTube Channel