Ian C Posted March 1, 2005 Share Posted March 1, 2005 what do the standard injectors look like? colour etc? Im finding loads of stuff done to mine by previous owner but I wanna check i got standard ones before i upgrade lol Grey = J-spec 440s Lavender = UK spec 550s Pink = VVTi 440s Yellow = Power Engineering 650s Those are the only ones I have experience of that will fit in a stock fuel rail. There are others but I've no idea what they are like. -Ian Quote Link to comment Share on other sites More sharing options...
Miguel Posted March 1, 2005 Share Posted March 1, 2005 1 more for your list Ian. Brown = Power Engineering 800s Quote Link to comment Share on other sites More sharing options...
Ian C Posted March 1, 2005 Share Posted March 1, 2005 Ian, I'm not trying to argue or dismiss what you've experienced etc, just trying to learn more. To this end, I was wondering if you'd had your injectors flow tested before you fitted them? If so can you let us know how much flow they passed and at what pressure? 720cc injectors must have been rated at a certain pressure. If you run anything but that pressure then you're effectively changing the flow rate, agreed? Anyway I'll leave trying to convince you not to include boost pressure for another day Cheers Tony I didn't think you were mate. Although I have a reputation for thinking things through in minute detail and gathering loads of info before making a decision or changes or whatever, there are points where I draw the line. I didn't research too much into the injectors because I didn't need to - I just found out which makes were good and which were shite, and simply went for ones easily big enough without going daft. In fact these came up as a 2nd hand 5000mile old bargain for half their new price, so I thought "yep, they'll do" To my good fortune, they are perfectly trimmable with an E-Manage and perfectly sized to run a T67 on race fuel with the boost wound up. Phew Fascinating as this discussion is I can't really add to it as I've got what I need and I don't need to spend any time or mental effort on working out why it shouldn't behave the way it does according to some formulae I'm trying to find the bastard wheel sensor wires on the facelift ABS ECU at the mo, that's keeping me busy I didn't get them flow tested but I did get Chris Wilson to clean them. If he flow tested them he didn't tell me the results. They are real big single cone buggers though. See bottom right on attached pic. -Ian Quote Link to comment Share on other sites More sharing options...
MONKEYmark Posted March 2, 2005 Share Posted March 2, 2005 some people seem to make things too hard, just look what works on other cars see what injectors they running and what electronics and take a chance. i would have thought go for a big injector with plenty of headroom incase your plans change. i got some 850`s and 960`s. wonder if a fuel kit with new rail and lines will be too much for stock turbos. i know you would need a ecu to control them. sometimes rather than go over things with a fine tooth combe just take a chance and try them, if they dont work out its your own fault. you just have to look at all the big power cars see what they running. http://www.to4r.com/toptenhp.php Quote Link to comment Share on other sites More sharing options...
Guest spoolin turbo Posted March 6, 2005 Share Posted March 6, 2005 for guys interested I can get you direct drop in injectors and fuel kits for a damn good price. Hit me up if interested. I use the same name on supraforum if you wanna check me out. Thanks Ryan [email protected] Quote Link to comment Share on other sites More sharing options...
dandan Posted July 14, 2006 Share Posted July 14, 2006 Looks like I missed this interesting thread but thought I'd add that the increase in fuel pressure from the fpr (when under boost) has absolutely F.A. to do with the flowrate through the injector. A regular 1:1 rate fpr will give a constant pressure differential across the injector (this will fluctuate slightly due to transient effects but we'll ignore that for simplicity). All these calculations people are looking at online use pressure differential for the rail pressure term (rail pressure+boost pressure will never come into it). The pressure differential is the pressure in the rail with no boost/vacuum source connected to the fpr. Or you could measure your rail pressure when idling normally and then subtract the vacuum you are seeing in the plenum, shown on your boost gauge. I'm sure most people know this but got a little concerned with why people started throwing boost pressure into the equation - boost pressure has no bearing on the fuel flow through the injector with a non rising rate fpr. Quote Link to comment Share on other sites More sharing options...
AndyT Posted April 5, 2007 Share Posted April 5, 2007 Right, I've done a bit of maths and come up with the following:- 440cc injectors at a stock fuel rail pressure should see you OK for approx 323 BHP at 80% max duty cycle using a BSFC of 0.64 (which my car was when stock) 550cc injectors should be good for 404BHP 650's should be good for 477BHP 850's = 625BHP 1000 = 735BHP 1600 = 1176BHP This has been calculated using the formula's given here http://www.rceng.com/technical.htm Obviosuly increasing the rail pressure will increase the potential output of the injectors, as would increasing the duty cycle. Hope that helps Tony Nice link Tony. Thanks. Quote Link to comment Share on other sites More sharing options...
Wez Posted April 5, 2007 Share Posted April 5, 2007 Looks like I missed this interesting thread but thought I'd add that the increase in fuel pressure from the fpr (when under boost) has absolutely F.A. to do with the flowrate through the injector. A regular 1:1 rate fpr will give a constant pressure differential across the injector (this will fluctuate slightly due to transient effects but we'll ignore that for simplicity). All these calculations people are looking at online use pressure differential for the rail pressure term (rail pressure+boost pressure will never come into it). The pressure differential is the pressure in the rail with no boost/vacuum source connected to the fpr. Or you could measure your rail pressure when idling normally and then subtract the vacuum you are seeing in the plenum, shown on your boost gauge. I'm sure most people know this but got a little concerned with why people started throwing boost pressure into the equation - boost pressure has no bearing on the fuel flow through the injector with a non rising rate fpr. If the fuel pressure across the rail is higher due to the manifold pressure acting on the FPR then for any given time space more fuel will be injected. I thought our 1:1 stock FPR means that for example static 2.5bar, one bar boost is 3.5bar fuel pressure. I am on a stock FPR with 650cc injectors running 1.4bar at 510hp Quote Link to comment Share on other sites More sharing options...
dandan Posted April 5, 2007 Share Posted April 5, 2007 If the fuel pressure across the rail is higher due to the manifold pressure acting on the FPR then for any given time space more fuel will be injected. The fuel is being injected into a region of higher pressure though Wez. If you applied 3 bar to the rail and injected into a beaker the volume would be the same as if you applied 5 bar to the rail but were injecting into a sealed beaker held at 2 bar. It's the pressure differential from one end of the injector to the other that is important and this is held (ignoring dynamic effects - not what we're discussing) constant with a normal 1:1 boost/vacuum referenced fpr. With the ign on you will probably see around 40psi in your rail. At idle this will be more like 30psi and at 1.4bar boost you'll be around 61psi rail pressure. The regulator makes sure the injector is always working with the same differential pressure - in this case, close to 40psi. Quote Link to comment Share on other sites More sharing options...
dandan Posted April 5, 2007 Share Posted April 5, 2007 I thought our 1:1 stock FPR means that for example static 2.5bar, one bar boost is 3.5bar fuel pressure. Correct. Doesn't mean more fuel goes through the injector though. Quote Link to comment Share on other sites More sharing options...
Wez Posted April 5, 2007 Share Posted April 5, 2007 If thats the case why does turning the pressure up allow you to run a lower duty, surely its because more fuel is flowing for the given time. What am I missing here? Quote Link to comment Share on other sites More sharing options...
dandan Posted April 5, 2007 Share Posted April 5, 2007 If you adjust the regulator from say 40psi static to 50psi then yes that 10psi has a direct effect on the volume of fuel injected. You then maintain a 50psi differential across the injector, as opposed to the 40psi you had before you adjusted the regulator. That is a different story to another 10psi of boost, which via the regulator raises the rail pressure to 50psi... the differential is still 40. Fuel flow will increase if the pressure differential increases (Rail pressure - intake pressure = differential pressure) Quote Link to comment Share on other sites More sharing options...
dandan Posted April 5, 2007 Share Posted April 5, 2007 If you had a massive tank of water pressurised to 50psi and connected a hose to it, water would squirt out at (near as dammit) 50psi. If you connected that hose to a tank of air which was held at 50psi then no water would flow into the air tank. The pressure in the runners acts against the fuel pressure coming through the injector. You'd need to exceed that intake pressure before any injection of fuel actually happened. Quote Link to comment Share on other sites More sharing options...
dandan Posted April 5, 2007 Share Posted April 5, 2007 Any clearer Wez? Quote Link to comment Share on other sites More sharing options...
Ian C Posted April 6, 2007 Share Posted April 6, 2007 At risk of undermining whatever the hell I wrote ages ago, Dandan has it spot on I think I was just arguing about some online calculator or something -Ian Quote Link to comment Share on other sites More sharing options...
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