Hi All,
I have a dilemma with my car which I would like to share with you and see if anyone can see a solution.
I\'m running 275rwhp on stock twins, no porting, big intercooler and \'zorst.
When max tuned it at reworx, geff said i could uprate the fuel pump and get a regulator, and get myself an extra 50hp with the standard injectors, as there is more boost to be used but the fuelling isn\'t there.
Well day to day i can easily hit 98% inj duty, and the other day i actually got 100%, and recently i have noticed a slight hesitation/flutter on high boost at high revs (5000+).
I changed the spark plugs and cleaned the air filter (it was FILTHY) and the hesitation definately died down but it still feels as if it may be holding back a tiny bit, it just doesn\'t feel as strong as i\'m sure it has previously been.
All I can think is the fuelling is lagging behind a bit, which would indicate need for a bigger pump, but surely if the injectors are already hitting 100%, how can I pull more power out of it?
I thought 100% meant a chance of running lean, but geff said I could run 100% all day long no problem. I\'m confused!
So do i need a bigger pump and regulator and things will be good, or should i get bigger injectors too, or am i completely off the scent and it could be something entirely different? Help!
I mention 20b boy purely cos you guys re-built it so you know the car pretty well. Any advice from any of you smart, smart people is much appreciated!
:):):)
Right lets confuse things.
If you have a hose pipe and turn the tap on full its running at 100%.
Now put a big pump on it and run at half tap, the hose is running at 50% of its capability but with the pump falsing it its only running half speed but with more water.
The 1600 injectors people keep asking/talking about, if you talk to bosch who make then they dont call them 1600\'s as thats misleading, becuase its capable of flow 1600 at 5 bar pressure but if you had a small pump it would only push 3 bar and so only (example) 1300cc of fuel.
There is a conversion to work out what cc of flow your injectors will run at what bar, but its too late to dig it out and understand it.
OK,
A bit of early morning maths.
I design mechanical services and this calc is used everyday, i thing its relevant
Pressure(of pump) x pressure(of pump) = Flow(through a fixed size oriface / your injectors)
So on your stock set up youve got (for example)
10 x 10 = 100%(duty)
but due to the square law, to increase your duty over the 100% we only have to increase the pump size a bit.
so if you want 150% normal duty:
square root of 150% = 12.25
so basically, to get 150% duty through the injectors you only have to increase the size of the pump by 25%
Confused ......Good
Nick
(Remember that it will have to be re-mapped)
it think this is getting a little more confusing than it needs to be. You seem to be talking about two different issues, first: you mention the car isnt as strong as used to be, thats an issue that is alittle more difficult to sort out, as it could be many things, including you turbos wearing out etc etc.
The other issue is what Geff/max has told, :put a better pump, and a fuel press reg, you can run more bhp", thats because with an adjustable fuel press reg and better pump, you could run a higher fuel pressure to the injectors, so that means for every period that the injector is open, more fuel will be going through the \'orifice\'. So you need to open it less to let the same fuel through or you get more fuel for your existing cycle. Yes you would need it mapped, as your fuel flow would be completely different.
I hope i havent missed the point of your question.....
Everyone is keeping up well so far!!
Ok I had the car tuned last month and i may be imagining it but i just feel the 2nd turbo is not quite pushing as hard as it was right after the tune, especially in 3rd gear and upwards, 1st and 2nd go by so quick you dont get a chance to feel any difference!!
It might just be that i am getting accustomed to the power, and it is definately less \'fluttery\' than before I changed the plugs and cleaned the filter.
So if we assume the engine is running ok now, the question is, do I need to worry about the fact that I can hit 100% duty? I really don\'t want any more detonation in my life!
I would be a little bit worried hitting 100% duty cycle all the time. Does this mainly happen in third or fourth gear?? If so it could be because the 2nd turbo is running too much boost in the higher gears so the fueling is increasing as a safety margin so that you don\'t detonate. Your best off speaking to whoever mapped it for you and getting them to check the map and maybe take some boost out of the 2nd turbo!!
Also, you say it\'s not pulling as much as it use too in 3rd gear. Are you still getting the same boost out of your 2nd turbo as before. If not, could be a vacum line or something if it\'s not holding boost!
Hope this doesn\'t confuse the situation anymore.
Well it is currently running .8 primary and .7 secondary due to lack of fuelling for higher boost, and hence why geff suggested a bigger pump. i just cant see this working with the same injectors, surely 100% duty is the max possible flow through the injector aperture, regardless of what is pumping it?
I\'m probably not understanding the basic principles of how injectors/pumps etc work and relate to each other.
All i know is I just want to make sure my engine is running sweetly.
Uprated fuel pump and fuel pressure regulator will do the trick. I had the same setup before and you can safely run more boost like this. I have a FSE variable rate fuel pressure regulator for sale for £50 if you are interested. Was only on my car for a couple of weeks so is more or less brand new. Then you just have to get the pump and the car mapped again!!
Dan, turn the tap on your hose just a little and sqeeze the end of the hose, you get a small amount of water out, turn the tap on full and squeeze the end the same amount (same aperture) and a lot more will come out. Same effect as turning your fuel pressure up......
You cant do it with the stock pump and an adjustble fuel pressure regulator as the stock pump doesnt flow enough.
The stock fuel pressure is about 43 psi, with an adjustable fuel press reg, you can run about 50psi, which is more fuel through the same size hole!!!
The duty cycle % just relates to what percentage of time the injector is open and allowing fuel through it. So 100% means its constantly open. Fuel pressure is unconnected, but more pressure means more fuel. If i\'m not explaining this properly, somebody please feel free to expand.
So, i\'m not the only one confused! Why, if an injector can handle more fuel - why upgrade to bigger injectors, like so many people have done!?
That is actually a really really good explanation, thanks!
its kind of making sense now.....
Quote from: nikpSo, i\'m not the only one confused! Why, if an injector can handle more fuel - why upgrade to bigger injectors, like so many people have done!?
Because you can only upgrade the fuel pressure to a certain point before you start bursting fuel lines and connectors and there is a upper limit of how much an injector will flow not matter what the fuel pressure is.
Of course running 100% duty on injectors is fine, but the life span of the injector goes down as the inbuilt solenoids have to work that bit harder in holding the injector open for longer peroids of time.
Aha! Thanks - makes sense! Cheers.
So, let me get this - you can run more fuel through the standard injectors, even at 100%. However, it may be a good idea at some point, if doing this, to upgrade the injectors, just so that they\'re not working quite so hard. Right?
So I was told that the pump and reg will get me 50ish extra horses, so will stock injectors be alright at 50psi pressure running around 320rwhp?
If geff seems to think so, then i would assume it will be ok?
I actually think I get it now! Woo! :D
good, i;m glad about that. You will have to speak to Geff about BHP figures, but you will have no problem running 50psi stock boost pressure, Geff may even advise a little higher. But best speak to him if he is tuning the car as he will want to know what the fuel pressure is set to for tuning.