Fuel Pump Regulated To 4 Bar?

[bales 1]

if you would prefer me not to post theory then i can refrain from doing so.

 

sorry to cause offense i thought that this forum wanted an intellectual input from its users, if mistaken or have come across in the wrong way im sorry

 

james

 

That wasn't what I meant by my post at all, it is good to have an intellectual input. But equally you can't question someone credentials when your own reasons aren't neccesarily based in experience.

 

Also how have you managed to do an automotive engineering degree and yet you are only 20?

They are either 3 or 4 years depending on whether its a BEng or MEng??

[wracing 19]

beng started when 17 distance, hence why i said one of those kids pushed through education gcse,alevels... and certificate pending.

 

i have never questioned anyones experience/credentials just dont like people quoting mappers what does it prove??? the last 'mapper' i met didnt know what egt is, having said that i have met some very talented people!

 

james

[taylorspug 7]

Saveit- Ive run one of the pumps at 4 bar for quite some time before and it coped fine, its still in my car now in fact. So in my experience the pump will cope fine. This is in reference to an early style pump from an 88/89 car, i have no experience with the later style phase 2 pumps, other than knowing they dont flow as well as the early items.

[Saveit 0]

Thank you. Just was i was looking to hear. I have an early style pump, so i would imagine it would be fine.

[taffycrook 2]

Saveit, the pump will cope with 4 bar. They are prone to failure, and I would replace it with a higher spec item once/if this happens.

 

WRC, the injector will not draw more current with an increased pressure, but it may take slightly longer to open, but we are talking micro seconds.

Current draw is constant, if all other viables remain constant, by this I refer to voltage and resistance. This is seen during snap acceleration testing of the current draw, injectors show no current change despite the difference in rail pressure during tickover the rail pressure reduces by around 0.5 bar as soon as the throttle is opened this increases yet there is no measurable change in current. The profile of the current draw changes by a small amount.

 

Bales, nowt wrong with theory. But its far more fun in practice.

[wracing 19]

current consumed by injectors has been tested on a car with different fuel pressures, with peak and hold (low impedance) both the peak and the holding current increase on high impedance current is also effected. the equipment used was a oscilloscope with current loops and also a current sensing resistor.

 

microseconds matter when you are getting into the realms of high flow heads and sequential injection....

[DrSarty 90 1 Cars]

Very interesting thread, even though Saveit has got the answer he was looking for. I'd still say the discussion is valuable though as it's fascinating to see two 'sides' at it in healthy technical and real world debate.

 

I have two very quick points:

 

1) Would be interesting to hear what Mr Sandy Brown would add to the technical debate

 

2) (Not a cat amongst the pigeons I promise) My 2.2 16v (~225-230BHP) and buckets of torque, had recommendations from two respected sources to just run the FPR on the bike body fuel rail, which is set at 2.8BAR. I'm running GTI6 injectors. Just wanted to know how this fitted in with the discussion?

 

I am not taking any sides, as I've just gone by recommendations like Saveit was doing. I do not know enough about this and would like to learn.

[DrSarty 90 1 Cars]

Double post. Soz.

Edited July 15, 2009 by DrSarty

[wracing 19]

 

i found this quite interesting if you wait till the end. no viable differences in spray pattern or atomization just what appears to be increased flow, even though American the bosch type injectors we use are there. even though some of the injectors are different manufactures failure occurs at a certain point!

 

james

[DrSarty 90 1 Cars]

James>

 

That is a useful video, but you must consider that this proves exactly why you've had a 'bit of heat' in this discussion.

 

The strictly technical approach could lead someone on a merry dance, and this is precisely why this older sounding guy has made this video.

 

What he's showing is that the manufacturers' specs are not telling the whole story. In effect, just like CO2 emission and fuel consumption figures for cars in their sales or official literature that the govt and customer sees, they are potentially (mostly) manipulated figures.

 

By using real world testing, even by a guy like this guy in the video - who may have no technical quals at all but has been pissing about with injectors for years and knows them inside out, i.e. he has 'feel' - he can see through the technical haze and steer you towards better results based on what he knows will work rather than what some book says will work based on a certain set of figures. If the figures are spurious in the first place then who do you trust?

 

So I think we can agree that both have their place, but there is simply no substitute for experience, and one should be careful when arguing strongly based on calculations and figures and schooling; an amount of real world testing will often tell a different story.

 

So for info, as the yanks use funny units:

The 43.5 lb/in^2 fuel pressure he refers to is 3.11 bar. When he ups it later to show one of the injectors failing (to 60 lb) then that's 4.29 bar.

 

What I am realising now is that when Sandy said about all of his trial and erroring with injectors, that he chose and recommended (including for my engine) the Bosch GTI6 injectors based on a great spray pattern which is something you can't really define in a spec sheet. Whilst the flow rate spec is not as high as others, and therefore perhaps these injectors being perceived as 'not as good', the real world test tells a different story.

[taffycrook 2]

current consumed by injectors has been tested on a car with different fuel pressures, with peak and hold (low impedance) both the peak and the holding current increase on high impedance current is also effected. the equipment used was a oscilloscope with current loops and also a current sensing resistor.

 

microseconds matter when you are getting into the realms of high flow heads and sequential injection....

 

I test injectors using a scope all the time. I can predict the current draw of an injector within measurable tolerences, the pressure has no effect as its not part of the electrical circuit. What changes is the profile of the current due to the change in pressure, the solenoid has to overcome the spring tension and inertia of the pintle which is added to by the pressure acting on the surface area which is small and therefore has little effect.

For example a sticking injector, which if we use your logic would draw more current (harder to move the pintle), draws no more current, but the profile is much altered.

 

I agree micro seconds matter, but thats why you map the fuel system. I normally see an opening time of 3ms for an injector at tickover, however it takes almost 1ms to open and around 1/2ms to close. Increasing the fuel pressure by 0.5-1 bar does not effect this significantly, but would result in increased fuel delivery.

 

Folk who suggest a given pressure for a injector and expected power output, have based this on expierence of past mapping. Thus the base map can be closer to the ideal, so less time is required to map the system and reduces costs.

We have a car with a 5 Bar pressure reg, it runs well but many "experts" would say its a touch high and is effecting spray patterns. But it makes 280ish bhp from 2.0ltrs N/A. I am sure if it had bigger injectors and reduced pressure it would make the same power, with plenty of additional mapping. ( It's injectors draw similar current to other injectors with similar impedence)

[StuF215 1 1 Cars]

 

Slightly off topic here but thought id take advantage of you FPR guys

 

I have the later style bosch 3bar regulator on my V6 but its not passing a SINGLE drop of fuel when I prime the pump, therefore my injector rails are dry!

 

Can these fail/block?? Its hasnt been used for 18 months I have never come across a blocked one!

 

£60ish from pug for a new one!

 

Thanks

Stu

Edited July 20, 2009 by StuF215

[taylorspug 7]

Have you taken the fuel feed hose off the rail and ran the pump to make sure the pump is working correctly?

[StuF215 1 1 Cars]

Yes fuel comes out of filter. You can hear the pump building pressure if you leave it connected. I then removed the outlet on the 2nd fuel rail and no fuel was passing. I tested the 2nd fuel rail and that was passing fuel fine so I eventually narrowed it down to the fpr. Only thing I could think of was it needing a vacuum to work but how would the system prime before cranking, so I dismissed that one.

 

I even tryed to pump fuel backwards through the rails with no joy.

 

Would you be able to blow through the brass piece and hear the air coming through the orange ring? I cant.

[welshpug 1,661]

only if you had lungs capable of 3 bar

[StuF215 1 1 Cars]

only if you had lungs capable of 3 bar

 

No not me, i'll ask the girlfriend she might have more luck