Stu @ M Developments

iTrader: (12)

Basically Phil... you mean you didnt know that and thought the injectors flowed more fuel at the higher pressure...

I think a RRFPR with a ratio of around 1.2:1 would give such a small increase in flow that it would be virtually pointless to be honest.

Quick example:
With 1.5bar of boost we would only gain around 4psi of fuel pressure by using a 1.2:1 reg over a std weber 1.0:1

4psi extra fuel in a rail running 73.5psi isnt going to allow us any more safe boost boost at all to be honest, it will just stress the pump and fuel lines some more.

Hope thsi helps.

Mike Gurney

Stu - don't some diesels use variable fuel pressure to flow to the injectors ?

what other methods can be used to control fuel pressure - could it be done with an elctronic linear actuator ?

Stu @ M Developments

iTrader: (12)

Diesels?
Most petrols do it too ... Cossie's are grotty old dinosoars mate.... just fookin fast with it

Got an Evo 7 in at the mo and that has electronic fuel regulation too...

Anonymous

Fellas,

As interesting a read this post is, I'm getting confused now

Is'nt the cossie fuelling simply a case as the base fuel pressure being set in the chip that is running under normal (i.e. off boost) conditions in order to maintain ecomomy, and then on boost the positive pressure in the plenum will increase the fuelling through the rev range to conplement the boost increases ???

I'm sure it's not as complicated as some people are making it out to be?

Let's not try to reinvent the wheel as I'm sure if these ''cheap'' tweaks could be carried out to acheive greater power outputs, then it would surely have been done now and someone would be making a great deal of money from it

Also, IIRC aren't injector capabilties governed by their flow rate as opposed to the pressure that is run through, i.e. a yellow injector can only flow up to it's max flow rate no matter what pressure you force the fuel in at ???

Rene

cool quote

foreigneRS

yes that helps Stu, thanks. is 1.2:1 all that you can get then?

say you had 2:1 running at 1.5 bar boost, you'd have a rail running [3.5 + (1.5 * 2)]*14.7 = 95.6 psi = 6.5 bar.

that is the equivalent fuel rail pressure of a std regulator seeing 3 bar boost. this sounds like a lot, but is it really stressing the pump (compared to 2 bar boost on greys)? if you're doing this on yellows, the volume the pump needs to supply is not greatly increased. if it's ok for the pump, surely an extra 1.5 bar, or 22 psi is worth having?

how does this fuel pressure increase translate into injector flow / power anyway?

Mike Gurney

"Also, IIRC aren't injector capabilties governed by their flow rate as opposed to the pressure that is run through, i.e. a yellow injector can only flow up to it's max flow rate no matter what pressure you force the fuel in at ??? "

the more fuel pressure you throw at an injector - the more it will flow

it goes up as the square of the base fuel pressure or something like that - i covered it a college yonks ago - Karl have you got the calc to hand ?


Stu - the EVo is it rising rate and electonic too - does it have a plunger or something - what sort of fule pressure can it run at idle and max ?

foreigneRS

let's not try and think of anything new then, is it? let's not have interesting technical discussions and try and improve ourselves through knowledge and understanding (one of the reasons that this board was started up)?

what do you want people to post?

what do you think creates a flow rate? it is the pressure difference.

Stu @ M Developments

iTrader: (12)

Nope, not at all mate. Read the post again, the increase in boost does "NOT" increase the flow rate of teh injector at all


Youd best not try, given you dont understand how the current wheel works


Once again.. read the post, MOST manufacturers now use elctronic pressure control.. it is cheap and it does work


foreigneRS,
The problem we have again is the square of the fuel flow, and the fact that as we increase pressure for the very reason of us being able to increase boost, we are creating further problems for ourselves by heading quickly towards the pumps flow max and possible lockout.

Bigger is still better.

Anonymous

Sorry I spoke ! don't mind me (dosen't this board ALSO give someone the ''freedom of speech'' within reasonable bounds)

You carry on with your stimulating and highly informative discussion and indeed further and improve your knowledge through heart felt understanding and knowledge.

If an injectors flow rate can be increased with a pressure increase then why do we have the luxuries of larger flow rate injectors i.e. dark greens, light blues , greys etc and why not just run a load of pressure through a set of yellows for any level of power ???

Mike Gurney

"If an injectors flow rate can be increased with a pressure increase then why do we have the luxuries of larger flow rate injectors i.e. dark greens, light blues , greys etc and why not just run a load of pressure through a set of yellows for any level of power ???"


you would need to run massive fuel pressures

also the spray pattern changes to a wider spray

Karl

Cossiep.

This is because we only have a set pressure range we can work to dicated by the pump. We cannot continue to increase fuel pressure past the pumps maximum working pressure for the flow rate we require! (we dont want pump lockout)

As such we are pretty much dicated by a maximum working pressure of between 5.5 - 6 bar on a cossie. If you take a car that runs 2 bar boost you can see that the base setting is going to be in the region of 3.5 - 4 bar which is exactly how all cossies are setup.

richm

CP - what Stu is trying to say, is that the answer to all these questions is in the post if you read it through, including this one..

Anonymous

Cheers Fellas

Trying to read the post AND digest it properly in between the boss handing me work

Stu @ M Developments

iTrader: (12)

foreigneRS

right. i understand now. thanks Stu, Karl, Rene and others for this interesting post.

Stu @ M Developments

iTrader: (12)

Thank's for participating with decent input...

Rene

one for the tech essay?

Stu @ M Developments

iTrader: (12)

Yes.. i think maybe it is Rene..

Let people consume it for a while then someone remind me to shift it in a day or two

JesseT

So to make yellows handle 500 hp, all we need is to tune the pressure regulator to 19 bar?
Sounds easy. I wonder why people spend their money on greens?



No, honestly this is a good topic as even I can remember it from the past.

foreigneRS

cos even with greens, you'd have to tune your pressure regulator to 18 bar to get 500 bhp

tonypastie