GeordieSteve Posted February 23, 2005 Share Posted February 23, 2005 Would that make much of a difference as to what injectors I'd need? I know someone else on here is using Envy hybrids Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted February 23, 2005 Share Posted February 23, 2005 It could do depending on the specs. Quote Link to comment Share on other sites More sharing options...
Gaz Walker Posted February 23, 2005 Share Posted February 23, 2005 What are Envy quoting for these turbo's?. Ask them for the inducer/exducer sizes and the spec on the exhaust wheel & I will answer from there. I am sure they wont mind if they are a genuine upgrade. FWIW Hybrids barely seem worth the effort/costs anymore. £1300 Terry. We don't give out technical specs of the hybrids - much like Leon. Our proof is in the power they make: Dyno leaderboard Gaz. Quote Link to comment Share on other sites More sharing options...
TLicense Posted February 23, 2005 Share Posted February 23, 2005 But remember most people run above the stock fuel pressure when modifying. Also, very few injectors have a decent spray pattern at Toyota's static. Tony, that is too general, what boost pressure are you basing the figures on? Remember the pressure rises with the boost. As far as I can work out, the rail pressure is actually kind of irrelevant for calculated HP for a particular flow of injector. (Although I'm still kind of working this out in my head so please correct me if I'm wrong) Y'see increasing the rail pressure (either by raised static pressure or by using a rising rate fuel pressure regulator) all you're doing is actually increasing the effective flow rate for that given injector. Hence why there's no pressure function in the calcs. IF you start to increase the rail pressure by either of the above, then you can increase the effective flow values as follows:- new effective flow rate = old flow rate * Square root(new pressure/old pressure) The pressure that you're boosting to if you are using a 1:1 fuel regulator (and I appreciate that most of us have rising rate regulators) is irrelevant also, as the pressure increase in the rail is cancelled out by the pressure increase in the cylinder. If you have a rising rate regulator then, for example for a 1:1.2 rising rate regulator (probably not realistic but for this example...) running at 14 psi then your new pressure = old pressure + 2.94. By my maths, if for example you raised the static pressure using the above rising rate regulator, from 31psi to 33.94psi then a 440cc injector effectively works out to be 460cc injector which would be capable of 338 BHP @ 80% duty (or 360 @ 85%). Quote Link to comment Share on other sites More sharing options...
MONKEYmark Posted February 24, 2005 Share Posted February 24, 2005 heres some good info on injectors. http://www.rceng.com/technical.htm injectors that drop into stock rail for jap cars are very expensive. ones for aftermarket rails are a lot cheaper to buy, but you need a resistor pack and new fuel rail. i always thought stock 440cc jap injectors were good for 400hp Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted February 24, 2005 Share Posted February 24, 2005 Tony, not to argue, but you are missing the way the FPR's work and the reason we have them on forced induction engines. Look at the RC tech page you posted. a static of 45 psi, then add 19 psi of boost, gives 64 psi of rail pressure agreed? Now punch in say 550 bhp, 6 injectors, 0.65 BSF, duty cycle 0.85, and a rail pressure of 64 psi, see what size injector you get. FYI my purple car made 690 FW bhp @ 25psi boost on 850's. That was on an engine dyno, so no BS figures. 40 psi static. No sign of fuel running out. Quote Link to comment Share on other sites More sharing options...
TLicense Posted February 24, 2005 Share Posted February 24, 2005 Tony, not to argue, but you are missing the way the FPR's work and the reason we have them on forced induction engines. Look at the RC tech page you posted. a static of 45 psi, then add 19 psi of boost, gives 64 psi of rail pressure agreed? Now punch in say 550 bhp, 6 injectors, 0.65 BSF, duty cycle 0.85, and a rail pressure of 64 psi, see what size injector you get. FYI my purple car made 690 FW bhp @ 25psi boost on 850's. That was on an engine dyno, so no BS figures. 40 psi static. No sign of fuel running out. No arguements at all mate, like I said I'm still working this out myself, so any input into how this is correctly worked out all helps. Perhaps at some point there could be a definitive how to size new injectors FAQ? A rising rate fuel pressure reg, AFAIK, gives you a certain increase in rail pressure for a certain increase in boost pressure yeah? A 1:1 reg, would give you a 1 bar rise in rail pressure for a 1 bar raise in boost pressure, whilst a 2:1 reg would give you 2 bar rise in rail pressure for a 1 bar raise in boost pressure? However, I still can't see how that makes a difference. The reason I say this is because you are including a delta in rail pressure, which is effectively changing the flow rate of the injector. All injectors are given a flow rate like 440cc, 1000cc or whatever. This must be done at a given pressure. If you change the pressure across the injector in any way from this given pressure then your effectively changing the flow rate of that injector. I've had a quick look, and from what I've gleamed of various sites is that 3 bar is used as a standard pressure. (If someone can cofirm?) It's also important that you look at the pressure across the inector NOT static plus boost pressure. After all we're only interested in what the injector can support at 80/85% duty cycle. That's will not change depending on boost pressure, in fact in a way it defines it. From what I've found on this BBS the stock line pressure is 31 psi(?) So that would actually mean that injectors rated for say 440cc at 3 bar (44.1psi) would actually be flowing a god deal less fuel at the stock rail pressure (and hence support less HP) That is of course presuming there is no rising rate regulator in the stock system. Again, I'm still working this out in my own head, so please feel free to correct any mistakes.... Quote Link to comment Share on other sites More sharing options...
TLicense Posted February 27, 2005 Share Posted February 27, 2005 OK so in my continuing attempt of trying to understand all of this, I've been reading the book Four Stroke Performance Tuning by A. Graham Bell (ISBN 1 85960 435 8) and basically I figured I'd mention here what he says as it would be good to bring some conclusion to this thread. So anyway in this book there's an excellent chapter on EFI, which confirms what I've said above. He says that most manufacturers state the static flow of their injectors at fuel pressures of either 2.5, 2.7, or 4 bar. He says that you should never run them at more than 5 bar otherwise you can lose control of them, and that he rarely sees any flow increase once the pressure has been increased beyond 4 bar. (However in calculating this you do not need to include boost pressure as this pressure is not seen by the injector due to the fuel regulator increasing the rail pressure proportionally to boost pressure) As far as what people have seen on there particular cars that disagrees with what I've found here, I've no explanation without conjecture, but logic dictates that there must have been other factors affecting the outcomes. My gut feeling is that maybe the injectors used were rated at a lower fuel pressure say 2.5 bar, which is then being run at a higher rail pressure when in actual use? As I say without knowing all the facts and details it's only conjecture. Regards Quote Link to comment Share on other sites More sharing options...
TLicense Posted February 27, 2005 Share Posted February 27, 2005 Sorry to sound a numpty here but are you saying that to get a hub figure I would need to take off approximately 20-25% of the bhp figure quoted or are you saying that the fly figure will be plus 20-25% of those figures? Sorry CJ, didn't see this question. What it means is that the figures I quotes are more or less flywheel figures. As most dyno's will give rwhp/hub horse power you should take that into account. I don't know what most people are allowing for transmission losses nowadays but basically you should take your "chassis hp" in whatever form that is (RWHP/hub HP) and add your transmission loss to this to get the HP that the engine is making. If your saying that you've got 20-25% losses and your making 400 RWHP then you should add 80-100 HP to that (I would err on the side of caution and go for the higher figure) then spec your injectors to support that figure. Hope that helps Quote Link to comment Share on other sites More sharing options...
Guest Usmann A Posted February 28, 2005 Share Posted February 28, 2005 Nope, Proper way to work out howmuch injector is needed is too calculate howmuch air the motor consumes at a given RPM. Looking at my scraps of A4 paper calcs, iv managed to find some info. It is depthy, like finding the mass of air, and comperssor ratio,VE(this is a task in itself),IC effiency,pressure ratio,etc etc, Once, CFM is worked out(rough example= CFM flow*Dr),then lb/min flow of air per each cycle, you can then punch in your target AFR and you have your ideal fuel flow. ie, eg,Calculated flow(this is all simplified and rough) 232.03 CFM* 2.024 Dr= 469.6 ACTUAL CFM flow 469.6 CFM* 0.76(conversion to lb/min) = 35.69lb/min 35.69 lb/min/4 cyl(4 pot)= 8.92 lb/min per each cycle AFR Target ratio 11.8:1 8.92lb/min /11.8= 7542 lb/min of fuel INJECTOR 83lb/hr injector 83lb/hr/60 seconds= 1.38 lb/min of capable fuel @100% duty Engine cycle injector hold open time: 7500 RPM/2 cycles per rev= 3750 cycles per rev 3750 cycles/60 sec= 62.5 cycles per second 1 sec/62.5 cycles= 0.16 seconds per each cycle 0.16=.16 milliseconds PulseWidth .7542 lb/min target fuel/1.38;b/min capable fuel= .5465 duty cycle 5465= 54.65 % duty. Sorry for the long post, ovbioulsy ive missed out Rail pressure, which can determine the actual flow of the injector, but I am giving a rough example of how fuel is to be calculated related to AIR. HTH, ps, I am going to sit down with my dad setup, and actually try measure temperatures for Comp efficiency,IC efficiency,so I can obtain near REAL enough Dr.with injector specs to compose a working map, and compare it to some more simplified ECUs, always fun doing some R&D! Quote Link to comment Share on other sites More sharing options...
TLicense Posted February 28, 2005 Share Posted February 28, 2005 Basically the method that I've stated (and until your post the only method I've seen/read/been told about) is by using BSFC to calculate injector size. Usmann I kinda see where you're coming from, and it would be a correct way to work out the duty cycle for a given RPM/AFR as far as I can see. BSFC is not interested at what AFR you use to create the reference 1 HP, or indeed at what RPM you make that HP. All it's interested in is creating it, and then multiplying that value up to suit the horsepower you intend to create in total for your engine. You can then divide that figure by the injector duty %age you desire to run max. This will give you a THEORETICAL flow rating. TBH I can see the way you propose being more accurate, but you will need to accurately be able to measure/calculate the CFM, which you'll not be able to do all too accurately without running the engine (to measure all the things you mention that you're going to meaure), which you'll not be able to do without injectors of a size large enough to start with. Kind of paradoxical. Another point is I don't think you need to be as accurate as that anyway. After all I don't think manufacturers supply 632.34cc injectors. So you'll only be rounding up to the next largest available injector that suits your application anyway. As I said I've looked into this quite a bit over the last 2/3 months as I'm speccing a fuel system for my car, and having looked at a few sources I've only ever seen the BSFC way of calculating required flow rate used. Interesting to see another way potentially being put into application though! Regards Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted February 28, 2005 Share Posted February 28, 2005 I can't comment on the technicalities or mathematical calculations involved in choosing the correct size injectors, but I have seen, (1st hand), a Supra running around 650 bhp on 650 PE injectors with a single Walbro pump, and the dyno plot shows no signs what-so-ever of it running lean, or even beginning to... Sadly, as yet, I don't know what the duty cycle was at that point, but I'm under no illusion that it's probably getting near the limit for both pump and injectors. Quote Link to comment Share on other sites More sharing options...
TLicense Posted February 28, 2005 Share Posted February 28, 2005 It's not so much the duty cycle as the static rail pressure that a) the 650's were specced for, and b) the static rail pressure they were run at. I've no doubt that they would be running high'ish cycles anyway, but running injectors specced at 2.5 bar at 4 bar rail pressure would make a considerable difference to the flow they can handle. If your running high octane fuel I guess that would make a difference too? Another major factor would be if you have 2ndry staged injectors, as you could have for example 6 primary injectors, and then if you go over 50% TPS at say over 50% total load, or even something as simple as if they go over 60% duty, you could then kick in a secondary set of injectors situated say in the intake runners. This way you could have say 2 sets of 440cc injectors, and have them jointly pumping out 880cc of fuel! Not likely that the car your talking about had this otherwise you'd probably have known about it. I'm just saying there must be other factors effecting the total amount of fuel flowing beacuse in theory that size injector at it's design pressure will not support that kind of HP. Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 28, 2005 Share Posted February 28, 2005 I never went into this much detail, I just went for a good size between stupidly big and not enough, and came up with 720's, and they work for me - here is an extract from a datalog: RPM = 6486 TPS = 99 Boost pressure (kgm/cm2) = 1.20 Duty cycle = 73% AFR = 11.36 Knock a point or two off that AFR and it's spot on. 650's would be on about 81% by now, so running 1.4bar of boost on a T67 with 650's is as far as you'd really want to take them but it's still within their performance envelope (and any more than 1.4bar on optimax is asking for trouble IMO) -Ian Quote Link to comment Share on other sites More sharing options...
Guest Usmann A Posted February 28, 2005 Share Posted February 28, 2005 Have you actually tried to workout BSFC on a 2J, I mean properly? What does staging injecotrs have anything todo with it?, anyway, staging injectors are better when MAP triggered, as TPS, does not exactly give a good indication of volume flow into the motor,and would forever be kicking on and off on crusing driving, and the Throttle blade can cause turbulence and affect AFR readings.(told by motecusa) It is all a very very depthy subject if one where to dive that deep into it, it would take ages. He also mentioned that, normal injectors are rated at a certain HP they support, but the designers do not take into account for forced induction motors which move more air, thus more fuel is used up, I think this is what you are seeing,yes? Quote Link to comment Share on other sites More sharing options...
dude Posted February 28, 2005 Share Posted February 28, 2005 £1300 Terry. We don't give out technical specs of the hybrids - much like Leon. Our proof is in the power they make: Dyno leaderboard Gaz. Everyone knows the turbos Leon WAS using(hybrids are sooo last year dhharlingg) were running RS500 internals , it makes me die when all it would take is to drop the turbos off at any manufacturer and get a spec in a couple of hours , if your punters dont know the specs how can they plan other mods ??? Dude Quote Link to comment Share on other sites More sharing options...
dude Posted February 28, 2005 Share Posted February 28, 2005 PS Dyno leaderboard Paul Evans made 490 hp on thors dyno on stock turbos just before they blew !!! Dude Quote Link to comment Share on other sites More sharing options...
TLicense Posted February 28, 2005 Share Posted February 28, 2005 Have you actually tried to workout BSFC on a 2J, I mean properly? What does staging injecotrs have anything todo with it?, anyway, staging injectors are better when MAP triggered, as TPS, does not exactly give a good indication of volume flow into the motor,and would forever be kicking on and off on crusing driving, and the Throttle blade can cause turbulence and affect AFR readings.(told by motecusa) It is all a very very depthy subject if one where to dive that deep into it, it would take ages. He also mentioned that, normal injectors are rated at a certain HP they support, but the designers do not take into account for forced induction motors which move more air, thus more fuel is used up, I think this is what you are seeing,yes? Usmann, No I've not worked out BSFC particularly accurately. I don't know of anyone who has engine dyno'd a stock 2J engine. But given an estimate of having 340bhp at the fly for a stock engine it is approximately 0.64 (certainly for my engine with 440cc injectors being run at 85% duty cycle) which is within what I've read as an acceptable estimation for a turbo engine. The reason I mentioned staging injectors was aimed at matt to mention that there can be many extra reasons for why an engine may appear to be giving better fuel flow through an injector than it really is. Sorry I was straying from the point... I guess calculating BSFC particularly accurately could indeed be a difficult and in-depth subject but as far as I've seen calculating how much fuel an engine requires to make 1 HP once BSFC is either known or can be accurately estimated is quite simple using the above formula's. As NA cars usually have a BSCF of approx. 0.5 and turbo cars have a BSCF of 0.65 this could be the extra fuel that he mentions, but this is taken into account in the calculation of flow required for HP by its inclusion in the calculation. For example to get 400HP in a NA car with a bsfc of 0.5 you would theoretically need 411cc of fuel at 85% duty. With a turbo (BSFC of 0.65) you would need 535cc of fuel. Suprising increase really. Ian, Out of interest which make of injectors was that with and at what static pressure. Perhaps it would be a good idea to build up a general idea of which manufacturers use which static pressure to define the flow of their injectors. Cheers Quote Link to comment Share on other sites More sharing options...
TLicense Posted February 28, 2005 Share Posted February 28, 2005 The reason I mentioned staging injectors was aimed at matt to mention that there can be many extra reasons for why an engine may appear to be giving better fuel flow through an injector than it really is. Sorry I was straying from the point... Sorry, I'm wrong there. It wouldn't be appearing to be flowing more than it really is. What I meant to say was it would be flowing more than it's "spec" or what it's sold as. Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 28, 2005 Share Posted February 28, 2005 Ian, Out of interest which make of injectors was that with and at what static pressure. Perhaps it would be a good idea to build up a general idea of which manufacturers use which static pressure to define the flow of their injectors. Cheers RC Engineering 720cc injectors, single cone, at 40psi static. Static = running the fuel system without the engine running, in case anyone else's definition differs At idle it's more like 32 to 34psi. http://www.rceng.com/technical.htm has some good stuff on it, including the effects of upping the fuel pressure. It also has a calculator engine for fuel injectors. Plugging in my numbers of 570fwhp, 6 injectors, .6 BSFC, .73 (73%) duty cycle and a rail pressure of 57.4psi (40psi static + 1.2bar/17.4psi of boost) it works out I'd need... 717cc injectors I guess turbocharged engines have a higher BSFC because they need to run richer under boost than a bhp-equivalent big-capacity NA engine. -Ian Quote Link to comment Share on other sites More sharing options...
TLicense Posted March 1, 2005 Share Posted March 1, 2005 Ian, as I've mentioned before, you don't add boost to the rail pressure as the pressure is equalised accross the injector when it opens, unless you were running a rising rate regulator... Other than that, that's the exact same formula that I've been rabbiting on about... (even from the same web page!) Quote Link to comment Share on other sites More sharing options...
SimonB Posted March 1, 2005 Share Posted March 1, 2005 From what I've found on this BBS the stock line pressure is 31 psi(?) So that would actually mean that injectors rated for say 440cc at 3 bar (44.1psi) would actually be flowing a god deal less fuel at the stock rail pressure (and hence support less HP) 31 psi is the fuel pressure under vacuum at idle (approx). Static fuel pressure is 40psi accrording to Terminators service manual. I see what you're saying about the fact that fuel pressure increases with boost - this is to counteract the extra pressure in the intake and maintain the same pressure difference between the injector and the intake. You basically need to calculate everything at static pressures. I'm going to run 50psi static, so that means my 440cc injectors will be the equivalent of 492cc injectors. 80% duty cycle is pretty conservative I would say though. I guess if you're speccing new injectors it's something to aim for though. Quote Link to comment Share on other sites More sharing options...
Ian C Posted March 1, 2005 Share Posted March 1, 2005 Ian, as I've mentioned before, you don't add boost to the rail pressure as the pressure is equalised accross the injector when it opens, unless you were running a rising rate regulator... Other than that, that's the exact same formula that I've been rabbiting on about... (even from the same web page!) Well, I just ran the same settings through except with 40psi instead of 57.4 and I get 480bhp, which I'm fairly sure is under what I've got based on recorded performance figures. I'm only saying what I've experienced, datalogged, recorded, and worked out from actual testing. Seems funny that the figures fit perfectly if you include the actual rail pressure and are wildly out if you don't - to me it shows how much boost you are running, but hey, I'm not gonna think about it too much because a) I've got 720's, b) I've got all the power I want, and c) I've got the ideal afrs at kosher duty cycles - what more do you want -Ian Quote Link to comment Share on other sites More sharing options...
TLicense Posted March 1, 2005 Share Posted March 1, 2005 31 psi is the fuel pressure under vacuum at idle (approx). Static fuel pressure is 40psi accrording to Terminators service manual. Ahh cool. I wasn't sure. It's the fact that the increase in rail pressure counteracts the boost pressure that you don't need to include it (unless the increase in rail pressure is greater than the increase in boost due to a rising rate regulator, in which case just increase it by the difference) Well, I just ran the same settings through except with 40psi instead of 57.4 and I get 480bhp, which I'm fairly sure is under what I've got based on recorded performance figures. I'm only saying what I've experienced, datalogged, recorded, and worked out from actual testing. Seems funny that the figures fit perfectly if you include the actual rail pressure and are wildly out if you don't - to me it shows how much boost you are running, but hey, I'm not gonna think about it too much because a) I've got 720's, b) I've got all the power I want, and c) I've got the ideal afrs at kosher duty cycles - what more do you want -Ian 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 Quote Link to comment Share on other sites More sharing options...
Toms Supra 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 Quote Link to comment Share on other sites More sharing options...
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