injectors

[maxfield]

If they don't add fuel on low load, and they don't add fuel at any other load, what do they do?

I think you answered your own question.

Jack shit by the sounds of that

[--alpina--]

STTTTTOOOOP, sorry dudes, its 3.0 bar standard on the 325 regulator, what i meant to say is whats the highest we can push it up to before it decides to go wrong say.....

your right i meant to say BAR not PSI..... mea culpa...



jimi

[Turbo-Brown]

Eh, nay lad, standard fuel pressure is 3bar which is about 43.5psi, there being 14.5psi in 1bar.

Think the pump would be the first thing to stop. No idea what it's rated to in terms of either flow or pressure.

There's not really any point in increasing the fuel pressure though unless you're trying to extract more power (fuel flow) from a given set of injectors, and even if you do, the mapping will be out elsewhere with the new higher fuel pressure.

[reggid]

what does "fse" stand for? is it just an adjustable fuel pressure regulator?

[Turbo-Brown]

Think FSE is the brand name.

[fistagon]

Yeah it is for sure, if you Google it I think there is a description of what it's meant to do on their website, which you can take as you will. My gut feeling (based on experiments I did with the stock FPR) is that it doesn't change the fuelling, rather responds to changes with greater agility. By this I mean: if you blip the throttle from idle on a stock car, the pressure at the regulator briefly drops sharply before rising again. My theory to explain this is that as you open the throttle butterfly the vacuum in the inlet manifold collapses temporarily...this controls the FPR and hence causes the drop in pressure I saw. If the FSE has a mechanism to avoid this I reckon that would explain the improvements in throttle response diamondblack claims. Or I could be talking total arse.

Back on the Alpina and Hartge extra power question...does anyone know if they went the route of upping the fuel pressure to get more in on these cars - maybe 3.5 bar or something? That would surely have been a more economical route than putting on bigger injectors.
Also I suppose you have to consider that they were 2.7 liter cars (correct me if that's wrong) and therefore under most conditions (i.e. where the injectors aren't maxxed out) the car could deliver power more strongly and could feel every inch the 180 or 190 or whatever it was they claimed!

I'm still interested in getting to the bottom of this... as another poster hinted if you use the injector calculators and use a best-case scenario for the factors you plug in it still seems to me that the standard injectors look somewhat weedy. Any more ideas chaps?

[Turbo-Brown]

Thing about the standard FPR is that a sudden collapse in vacuum (i.e. pressure increase) should lead to a sudden increase in fuel pressure. The standard FPR is able to react pretty much instantaneously to changes in load. I'd guess that the sudden increase in duty of the injectors lead to the fuel pressure drop you observed.

Also I suppose you have to consider that they were 2.7 liter cars (correct me if that's wrong) and therefore under most conditions (i.e. where the injectors aren't maxxed out) the car could deliver power more strongly and could feel every inch the 180 or 190 or whatever it was they claimed!

Problem with that arguement is that you could never use wide open throttle and full revs as you'd melt a piston. Power is power, regardless of engine size.

I've copied this over from the other thread on injectors:

Right, just gone over there and found the thread:

http://www.e30tech.com/forum/viewtopic. ... highlight=

From Topic: interesting fact about the m20b25 and its factory injectors.

the interesting thing i noticed while i was modding a rom file today is that that at WOT the injecotrs are at 95% pulse rate... most car companies wont run thier injectors above 80% to increase longevity, why would BMW do something so cheap... the injectors barely support the engine at 100% under high revs we all know the engine is very lean with the factory injectors... why would BMW do that?

So lets do the maths:

149cc/min x 95%=141.55cc/min

((141.55cc/min)x6cyls)/5(rule of thumb)=169.86bhp which by my reckoning is about 1bhp shy of what BMW quoted for the M20B25.

You can see why I'm sceptical about vastly higher power claims on the standard fuel system!

Interesting / compelling no?

[fistagon]

Thing about the standard FPR is that a sudden collapse in vacuum (i.e. pressure increase) should lead to a sudden increase in fuel pressure. The standard FPR is able to react pretty much instantaneously to changes in load. I'd guess that the sudden increase in duty of the injectors lead to the fuel pressure drop you observed.

Ah it works that way round!

Also I suppose you have to consider that they were 2.7 liter cars (correct me if that's wrong) and therefore under most conditions (i.e. where the injectors aren't maxxed out) the car could deliver power more strongly and could feel every inch the 180 or 190 or whatever it was they claimed!

Problem with that arguement is that you could never use wide open throttle and full revs as you'd melt a piston. Power is power, regardless of engine size.

Good point, no mileage in that idea then...

I've copied this over from the other thread on injectors:

Right, just gone over there and found the thread:

http://www.e30tech.com/forum/viewtopic. ... highlight=

From Topic: interesting fact about the m20b25 and its factory injectors.

the interesting thing i noticed while i was modding a rom file today is that that at WOT the injecotrs are at 95% pulse rate... most car companies wont run thier injectors above 80% to increase longevity, why would BMW do something so cheap... the injectors barely support the engine at 100% under high revs we all know the engine is very lean with the factory injectors... why would BMW do that?

So lets do the maths:

149cc/min x 95%=141.55cc/min

((141.55cc/min)x6cyls)/5(rule of thumb)=169.86bhp which by my reckoning is about 1bhp shy of what BMW quoted for the M20B25.

You can see why I'm sceptical about vastly higher power claims on the standard fuel system!

Interesting / compelling no?

Yes indeed, 95% seems insane, no wonder my old injectors were past it!

[cubic]

http://www.rceng.com/technical.htm

plugging the numbers into that site seems to support my arguement?

they use 0.5 for the bmfc which is an assumption it may be 0.4 or 0.6 nobody can tell you which it is for any particular car, you'll need an accurate engine dyno and diagnostic equipment. Those numbers may apply well to a big American V8 but not neccesarily to a small 6cyl BMW

Anyone have anything to add about the injection system used (injector flow rate and pressure) on the Alpina and Hartge 2.7? That should tell us what the stock M20 units are capable of.

yes mate my C2 2.7 has blue 715 injectors and 3.0bar reg

[Turbo-Brown]

Couldn't measure the length of the FPR capsule with a vernier could you Cubic?

Just to rule out the possibility of Alpina having given them a squeeze to get more fuel pressure.

[cubic]

sorry mate since i moved house i can not for the life of me find my calipers i even tried blaming the wife but still no luck

i have however compared against another and there is definitely no difference. hope this helps... jay