injector rant READ HERE rb20/25/26!

[Carl H]

ok, im tired of reading all these threads speculating on how much power the stock injectors can support on these motors, heres how it breaks down in laymans terms.injector sizing on a straight six works like this max bhp out of said injectors is the injector rating; so 270cc would mean that it can hypotheicaly support 270bhp at 100% duty cycle.

100% duty cycle is bad,mmkay kids, this leads to melted injectors and perhaps melted pistons.

so all these threads where you see ppl saying that you can make 300whp on stock rb20 injectors, you guys are complete fools to believe that.safe power out of stock injectors is almost the nominal output you get after intake and exhaust, 200ish whp is about 240hp at the crank and therefore over the 80% reccomended injector duty cycle.

sooo what im saying is if you plan to make good power on a rb20 injector upgrades are a must, on the 25 you can scrape by for a bit before you start running silly duty cycles and should you own a 26 you should already know what you are doing.

ok, now perhaps there will be a bit less misinformation strewn about.

[Vkoslak]

Thanks!

I can't remember where I heard 300 at.

Got some cheap injectors?

[Yellow4g63]

I bought some 700cc sard topfeed for $509 shipped new.

[Reignman]

Agreed. Its a waste to spend all the money and time on these engines and mods yet never upgrade injectors. Why risk damaging/destroying the engine when injectors and a good tune can give you a well running, reliable engine.

[DrifterTom]

b/c this is the first high hp motor for most of these guys. it takes blowing one up before you start to worry about the small things like fuel, a fuel map, and oil pressure

all they had to do their honda was an intake and turn up the fuel pressure and vrooom off they go in their race car

[Valley]

b/c this is the first high hp motor for most of these guys. it takes blowing one up before you start to worry about the small things like fuel, a fuel map, and oil pressure

all they had to do their honda was an intake and turn up the fuel pressure and vrooom off they go in their race car

wow... thats an ignorant post if i've ever seem one. also, high hp is subjective.
Modified by Valley at 5:38 AM 3/24/2006

[Reignman]

I think its an issue of research. What is posted on these boards is not always the correct way to do things (sometimes totally wrong). Also not wanting to spend the money to keep the engine safely running once upgrading.

[armysweitzer]

being that I asked one of those questions I think you guys are looking at horribly wrong.

Im sorry but this search engine sucks, get over it. Most of the topics are about what to use, hardly ever is there personal insight or expierence related responses.

When people do respond mostly its noobs trying to get a higher post count.

A great example is spark plugs, I looked in the parts reference list, 2394732947 responses of DIFFERENT types to use. Does anybody say what they liked or people who have used more then 1 type prefer....NOOOO (prove me wrong id love to know)

Speaking for myself now ( i feel a tad above noob status (completed and have a perfectly running rb s13) Usually have posts that Im sure have been mentioned somewhere before, does that mean ive found what im looking for. Probably not, I do it to cross reference prior responses to get a better feel for whatever im wondering.

Not to say there arent stupid posts like ...

-how much money is it for 2343 hp from a rb90?

-or what rb is best?

I think the best way to deal with this **** is to honestly respond to those who have questions about certain topics and simply ignore those who ask dumb questions. If we as a whole can weed out those who actually want to move forward in the RB community and those who want a super car super cheap we can improve these boards 10 fold.

But it will take a lot of effort and patience from the seniors here who shouldnt respond with posts like these, more with posts like for 300 hp id reccomend useing 440cc injectors with ____ software to control it. That way peoples questions are answered....

[a 1g terror]

b/c this is the first high hp motor for most of these guys. it takes blowing one up before you start to worry about the small things like fuel, a fuel map, and oil pressure

all they had to do their honda was an intake and turn up the fuel pressure and vrooom off they go in their race car

I learnd on a turbo B16 hatch.. the one in my sig* i blew that up a couple times I know better now.

befor teh honda was a DSM but we all know how that goes...

[Wulfgang]

I beg to differ, Carl. For sizing NEW injectors, all the things you said are correct, except for maybe the 270cc = 270 hp number. Other "rules of thumb" say divide the cc's by 5 - not 6 - which gives a number above 300 hp for the RB20.

But all of the rules of thumb, sizing calculators, FAQ's, all that... they are for sizing NEW injectors, and as such, they are conservative. Those calculations typically use a conservative duty cycle (80%) and a conservative bsfc (.55ish) based on a conservative gasoline mix (low energy content) and a low-tech (read "American") engine. Yes, you would be a fool to shoot for 400 hp and go out and buy 6 new injectors that can barely make 400 hp at 100% duty with an 11.5:1 AFR. I agree... that is stupid. So use the conservative numbers when shopping for new injectors.

Not so for OEM injectors. Once you already have injectors, there is absolutely nothing wrong with running up past 90% duty cycle as long as you are still running rich and not detonating. Do the math. Even if your injectors are wide open (typically somewhere above 90%), then as long as you still show 11.5:1 or richer on the AFR, then you've got some headspace left. If at 7000 rpm you still show 11.5:1 AFR, then you could over-rev by another 350 rpm before the AFR even goes to 12:1. It's all about the risk you are willing to take, but IMHO 350 rpm is plenty of room, especially when running 12:1 AFR on a mildly boosted stock RB20. If that's a problem, get yourself a shift light.

So if someone has an engine that is making 300 rwhp with 11.5:1 AFR and has dyno sheets to prove it, then nobody is a "fool" for believing it. We tend to believe what we see, after all. That same engine could probably be tweaked (FMIC and/or water injection for example) to run with a higher AFR and get into the 330 rwhp range because of a better AFR. In that case, why buy new injectors? The smaller ones get you better gas mileage (not that anybody with an RB cares about mileage).

The only "myth" I see is the one about melting injectors at 100% duty cycle. I'm not sure where that idea comes from. I know there used to be some old Nissan injectors that could catch on fire (due to a design flaw), but those were recalled. I have yet to see (or hear of) an injector that melted from running too high duty cycle. Heck, they pull less than 1 amp! Even if you connected them directly to the battery they'd only dissipate 12 watts.

Bottom line is this: if you want new injectors, size them conservatively. But if you want to see how far your old injectors will go, then get a wideband and go find the limit.

[armysweitzer]

i think you just proved me and carl wrong, lmao an actually informative post.

Thank you wulfgang, now time for some dyno sheets and readouts!!!

[Carl H]

good info, but each to his own and i perfer to run low duty cycles for the saftey that is offered.while you may be correct in saying that any injector is capable of running at 90-100% duty reliably, it is simply a risk i would rather not take as the overhead required is so little why trust your motor to running the injector on the edge.when you pass the 80% threshold you loose the accuracy of the injector to properly meter the fuel, with the solenoid cycling so many times it may miss a cycle or stick open on one; who knows at that point what could happen.

another thing to take into consideration is that some people run higher than the reccomended base fuel pressure to squeeze a bit more flow out of the injectors, while it does indeed work it is a bandaid solution and isnt as accurate as proper injectors and a good tune.

as for the gas mileage bit, that is a myth in and of its self.my car got 30mpg highway and 25city (20-22 if i romped on it alot), and it never had a problem.gas mileage is dictated by the tune and afr's underboost, not the injectors, a properly setup system (which is tuned) will get good gasmileage and still provide safe and reliable power.

but then again who am i to say whats right and whats wrong, i just dabble in these motors.my .02c

[rbsileighty]

Bumping up base pressure is fine as long as you know what it brings you up to... I have a conversion chart somewhere of how it affects the cc's...

So for cheating... I use to think so too, but higher fuel pressures allow for better atomization... which is better for everything. Just be sure your fuel pump can keep up and you have a FP gauge to be sure it is...

I could see you burning a coil if you ran 100% duty cycle all the time... but I doubt it since you will probably not be seeing 100% all the time (unless you're running RB20 injectors on a moded RB26 maybe...).

At Bosch (I use to be a fuel injection engineer) we ran injectors through all kinds of testing... and the "seating in" of the valve seat is true as Wulf said... you will increase flow as the injectors age (seen in endurance testing), but it's not a huge amount (unless you ran them dry forever... and then they'd leak... very badly)

So that's my 1.50'ish... just put a FPR and a good fuel pump and start from there... if you need more fuel (after testing with a wide band and adjusting what you have etc)... get bigger injectors...

[RB20DETodd]

I know im coming out of deep right field with this one but ARE DSM INJECTORS A DIRECT DROP IN in the rb20? can anyone confirm it?

thanks

[eh?]

The only "myth" I see is the one about melting injectors at 100% duty cycle. I'm not sure where that idea comes from. I know there used to be some old Nissan injectors that could catch on fire (due to a design flaw), but those were recalled. I have yet to see (or hear of) an injector that melted from running too high duty cycle. Heck, they pull less than 1 amp! Even if you connected them directly to the battery they'd only dissipate 12 watts.

I've had my RB25 injector duty cycle reading over 100% on my aem ems quite a few times. Actually the highest it read was 106%. AFR's were always nice and level. I was honestly more worried about buring an injector driver than the injector itself.(of course now I have a set of 760cc's)

[T4 RB25det]

I learnd on a turbo B16 hatch.. the one in my sig* i blew that up a couple times I know better now.

befor teh honda was a DSM but we all know how that goes...

haha, yeah 2 or 3 of your motors only lasted for a day, the other ones last a bit longer until you started to try and blow them

[Yellow4g63]

I know im coming out of deep right field with this one but ARE DSM INJECTORS A DIRECT DROP IN in the rb20? can anyone confirm it?

thanks

Im not sure if the stock DSM injectors fit, but they might. I tried some Denso 660cc injectors I took off my dsm before I sold it and they went right into the fuel rail.

[kamikazi]

i think the dsm injectors work, i just got a set of 7m-gte injectors for 75 bucks for my rb20 and their rated at 440cc.
Modified by kamikazi at 7:22 PM 3/28/2006

[DrifterTom]

i got mine for free. it pays to be the poor guy that the supra shop feels sorry for. i get all the throw offs. 350z seats, injectors, five greddy guages, endless advice, and others all free.

thats the only lucky thing that has happened to this car

[kamikazi]

dang, i wish i could get some free 350z seats.

[Vkoslak]

350z seats in a 240sx arent all that comfortable.Always made my butt go numb after an hour or so.

[johnzm]

good info, but each to his own and i perfer to run low duty cycles for the saftey that is offered.while you may be correct in saying that any injector is capable of running at 90-100% duty reliably, it is simply a risk i would rather not take as the overhead required is so little why trust your motor to running the injector on the edge.when you pass the 80% threshold you loose the accuracy of the injector to properly meter the fuel, with the solenoid cycling so many times it may miss a cycle or stick open on one; who knows at that point what could happen.

another thing to take into consideration is that some people run higher than the reccomended base fuel pressure to squeeze a bit more flow out of the injectors, while it does indeed work it is a bandaid solution and isnt as accurate as proper injectors and a good tune.

as for the gas mileage bit, that is a myth in and of its self.my car got 30mpg highway and 25city (20-22 if i romped on it alot), and it never had a problem.gas mileage is dictated by the tune and afr's underboost, not the injectors, a properly setup system (which is tuned) will get good gasmileage and still provide safe and reliable power.

but then again who am i to say whats right and whats wrong, i just dabble in these motors.my .02c

can you please explain why adding fuel pressue isint as accurate, or would be as you call it a "bandaid solution"??

last i chceked the higher the fuel pressure the more accurate the injector is going to be, along with increased atomisation, i wouldnt hesitate to increase pressure if i had the means (im currently only tuning with a chipped ECU)

#edit#and who gave you this 80% crap. its a NUMBER i have seen people run 120% with no problems.

based on my 3-4 years of professional tuning experienceUPGRADE INJECTORS WHEN YOU RUN OUT OF FUELyou get erratic AFR's or uncontrollable numbers theres obviously something else wrong, pushing an injector past 80% duty isint going to create an unsafe situation..

[Carl H]

can you please explain why adding fuel pressue isint as accurate, or would be as you call it a "bandaid solution"??

last i chceked the higher the fuel pressure the more accurate the injector is going to be, along with increased atomisation, i wouldnt hesitate to increase pressure if i had the means (im currently only tuning with a chipped ECU)

#edit#and who gave you this 80% crap. its a NUMBER i have seen people run 120% with no problems.

based on my 3-4 years of professional tuning experienceUPGRADE INJECTORS WHEN YOU RUN OUT OF FUELyou get erratic AFR's or uncontrollable numbers theres obviously something else wrong, pushing an injector past 80% duty isint going to create an unsafe situation..

i see raising fuel pressure as a bandaid because you are assuming that the fuel pump can keep up with the increased pressure, last time i checked unless you rewire the pump it is a known fact that the pressure tapers vs rpm; correct me if im wrong.

as far as the duty cycle is concerned sure you can run 120% duty, but its not flowing anymore than it was at 100% unless you can some how magicaly make it flow more when its already open all the time (and im assuming that you would do this by cranking the fuel pressure).afrs might be fine but thats only because the injectors are nothing more than a hole in a bucket at 100% duty, what happens when you reach the point where afr's start to increace but are already at 100% duty its not like you can get anymore flow out of them?

its obvious that there are 2 schools of thought when it comes to injectors, and i stand on the side that plays it safe by keeping the injector duty below 80%, atleast with 80% you have a bit of headroom should something happen and the motor require more fuel than you thought, cant really say that you have headroom at 100% duty can you?

its cheap to upgrade injectors (cheap being relative here) so why would you buy ones that are going to be at 100% duty at the power you want when you can get ones that will be at 60% for example, doesnt make sense to me.you dont size a turbo based upon its *max* power output (gt28rs is a perfect example) sure the turbo is capable of 350 horse power but that power comes at 25+psi of boost, why put excess stress on the motor when the same thing can be acomplished with something slightly larger and in the long term "safer".thats all im trying to get at with the injector sizing bit, take it as you like but as with anything make your own decision.......

*addendum*heres a few threads on say on how to make 500ishwhp on stock injectors and then how to go cry when your 500hp motor blows up cuz you were on stock injectors.

http://www.skylinesaustralia.c...04&hl=http://www.skylinesaustralia.c...18&hl=


Modified by Carl H at 1:16 AM 3/30/2006

[johnzm]

i see raising fuel pressure as a bandaid because you are assuming that the fuel pump can keep up with the increased pressure, last time i checked unless you rewire the pump it is a known fact that the pressure tapers vs rpm; correct me if im wrong.

as far as the duty cycle is concerned sure you can run 120% duty, but its not flowing anymore than it was at 100% unless you can some how magicaly make it flow more when its already open all the time (and im assuming that you would do this by cranking the fuel pressure).afrs might be fine but thats only because the injectors are nothing more than a hole in a bucket at 100% duty, what happens when you reach the point where afr's start to increace but are already at 100% duty its not like you can get anymore flow out of them?

its obvious that there are 2 schools of thought when it comes to injectors, and i stand on the side that plays it safe by keeping the injector duty below 80%, atleast with 80% you have a bit of headroom should something happen and the motor require more fuel than you thought, cant really say that you have headroom at 100% duty can you?

its cheap to upgrade injectors (cheap being relative here) so why would you buy ones that are going to be at 100% duty at the power you want when you can get ones that will be at 60% for example, doesnt make sense to me.you dont size a turbo based upon its *max* power output (gt28rs is a perfect example) sure the turbo is capable of 350 horse power but that power comes at 25+psi of boost, why put excess stress on the motor when the same thing can be acomplished with something slightly larger and in the long term "safer".thats all im trying to get at with the injector sizing bit, take it as you like but as with anything make your own decision.......

*addendum*heres a few threads on say on how to make 500ishwhp on stock injectors and then how to go cry when your 500hp motor blows up cuz you were on stock injectors.

http://www.skylinesaustralia.c...04&hl=http://www.skylinesaustralia.c...18&hl=

Modified by Carl H at 1:16 AM 3/30/2006

dont get me wrong here, im on your side for most of this, especially sice i see "lets make 600hp" threads once a week on here.. but some your data is flawed.. i.e. *calculated* 100% duty still has flow left, readabove that wear/tear on injectors can/does change their flow rating. also i understand that pressure tapers off with rev's. but your (i hope) running an upgraded fuel pump that can hold at least 50psi to redline, even with 16+m/s injector duration. i never meant to imply that running more than 50-60 psi is a worthwhile thing to do, because i have seen quite a few cars burn down from fuel line ruptures, and it ISINT pretty.

but yes, for all the people who ARENT that knowledgable, i can add tothis discussion

#1 injectors WONT get you more hp without tuning and other mods. (this for SOME REASON is a popular myth among beginners in the scene)

#2 you cant just throw 1000cc injectors on and expect the car to run properly. IMO everytime injectors are changed, the car needs to be retuned.

#3 80%, whileclearly being a "guessing game" is guessing on the safe side. if you dont have the knowledge or tools to moniter or tune your motor yourself, always stay on the safe side.

#4 dont expect bigger injectors to cure a failing/weak fuel pump.

BTW carl- what did u read that made u wanna rant?