not the proper way of doing things, but thoughts, boost without management

[uk525td]

So, ive been sat ona thread in another forum, and a discussion kicked off about running low boost without management.
The discussion was that our M5x cars can be boosted to low figures, 6-9 psi was quoted with nothing more than a rising rate fuel pressure regulator.
Now, i don't agree with this whatsoever, im sure it would work, but i dont like relying on chance in these matters

So, whats the thoughts? in theory it would be fine but crude, although im not sure what the management would do (if anything) regarding timing.
I assume that when running a rising rate fpr you would keep the maf on the pressurised side of the inlet?

figures of 245 horsepower (god knows were this came from it may have been summoned out of the air) were bounced around, and no documented examples were presented, although i think ive seen pics of said builds previously.

so, just a friendly discussion, no answers like it will explode, it won't work, just practical arguments to the limitations. Not something i will do but interested to hear your thoughts?

[Captain]

You are not going to get any real responses out of anyone here except the short negatives remarks you said you did not want. If you search this section you will find the information you are looking for. No one wants to talk about this since it has been discussed at length and the end result is not anything anyone wants. No one here wants to discuss boost without engine management. Thats it, case closed, move on.

Just trying to be honest.

[uk525td]

thats cool
i just found it an interesting topic for which ive never really seen much discussion round here :)

[NOTORIOUS VR]

it's not just timing... the ECU will correct for the extra fuel as well from the RRFPR...

it's an all around bad idea... do it right and get a proper tune.

RRFPR's have no place in a boosted car these days.. it's not the mid 90's anymore

[bawareca]

.............

RRFPR's have no place in a boosted car these days.. it's not the mid 90's anymore

:thumbup:

It is 21st century,you can get a standalone for under $500.

[5mall5nail5]

Not only that but you'll over draw the MAF

[M5Hunter]

I'll be honest, I dont know a pile about the BMW ECU's, but most other manufacturers have fuel correction using the o2 sensors. Meaning no matter how much you raise the fuel pressure, the computer will try to maintain a set A/F ratio (usually around 14.67:1) by shortening the pulse width of the injectors. Obviously, in this case, that is not the desired AFR.

[uk525td]

yer but thats only under idle/cruise conditions
the dmes go open loop on load, as narrowband sensors cant measure the required ratios

[hakentt]

yer but thats only under idle/cruise conditions
the dmes go open loop on load, as narrowband sensors cant measure the required ratios

Stock ECU is the best ECU for these cars, and tuning software is free and information has been posted on this forum

[Mellor]

it's an all around bad idea... do it right and get a proper tune.http://www.demama.info/g.php

[5mall5nail5]

I'll be honest, I dont know a pile about the BMW ECU's, but most other manufacturers have fuel correction using the o2 sensors. Meaning no matter how much you raise the fuel pressure, the computer will try to maintain a set A/F ratio (usually around 14.67:1) by shortening the pulse width of the injectors. Obviously, in this case, that is not the desired AFR.

In higher boost and full throttle the ECU will go open loop and not try to trim anything, in theory. But, you cannot gain enough fuel flow through the stock injectors to satisfy that amount of air with manipulating fuel pressure alone. I've run an RRFPR on my older s/c setup on a 10:1 motor with no knock sensors - it "worked" but ... how well? And how much power was I making? And how much power more could I have made? All questions I have no answer for. Was running 9-9.5 psi from an ASA TM-12 CF supercharger non-intercooled. Throws the check enginel ight around 5000 RPM due to overdrawing the MAF.

[jone30]

Personal experience, I just bought a '92 325 with an older Mosselman Turbo system on it. All it basically is is a small turbo running, at the most, 6 PSI with a RRFPR and timing retard box. Previous owner put it on the car in '99 when he bought it. Hasn't given me any real problems in the 4 1/2 months I've owned it. Now, I do have plans to update the engine management to a proper system, but for now it works just fine and I'm ok with running it as is.

[bawareca]

^^^Yes it works,especially with the modest 6 psi.I used to run the car in my avatar with everything homemade except the KKK26 turbo and MB Sprinter intercooler @15-16 psi with just a bigger injectors and narrowband gauge :eek: It ran strong for more than 2k hard lived miles and has a countless kills on the track and the street,but i wouldnt go that route again.
We are at the 21st century now and MS is probably cheaper than what the RRFPR used to be back in the days:lol

[uk525td]

Good stuff so far thanks a lot


Stock ECU is the best ECU for these cars, and tuning software is free and information has been posted on this forum

See, here's the thing, i know it is possible, i tried researching tuning your own dme, seemed like a lot of equipment required, and a certain element of voodoo, everything seemed to need manipulating at the hex level.
Much simpler to go megasquirt and im sure, financially similar. I am aware ms is not considered as good as our stock DME's.