What injectors

[Bigwilly6754]

OK if u had a garret t3/t4 60 trim what fuel injecters would you run!???

 

[talonted_one]

It would depend on your expected or target horsepower range is. If you go by RC engineerings calculations in order to safely support ~400 hp @ 85% duty cycle I think you would have to run ~720cc injectors. We all know you don't need that big of injectors but that's to be safe.


So I don't think anyone can really say what size injector until we know how much power you wanna make.

 

[Bigwilly6754]

say if i wanna run 450 wheel horse power!

 

[talonted_one]

I would suggest 720cc.

that should give you more than enough room to tune. I have seen people use 660s with sucess

 

[SOURCE1064]

I went with RRE's chart and got 720cc for my 60-1.

 

[CraigB]

I have a 60 trim and I run 4 550s and 2 450s as sub injectors. The 720s would be a pain to tune at idle and low end. If you just want to run 4 injectors then run the 660s.

 

[kpt4321]

If you want to make that much power on race gas, 650's will be fine. *Maybe* even 550's.

To make that on pump, you'll probably need something bigger than 720's...

 

[talonsport]

and if i put another 4 450cc original inyector with an aditonaol controler for them ?

what do you think of that?

 

[talonsport]

and if i put another 4 450cc original inyector with an aditonaol controler for them ?

what do you think of that?

 

[Drifte]

i think 4 more injectors sounds like a bit of work. why not go with 550-650, its easier to tune idle and bottom end. I tuned 450's for a 1.5l honda, thats a challenge.Any one have any ideas of gas mileage when you increase the injector from 450 to some massive beasts?. i figure if you don't boost, you don't use any more, but is that true?

 

[brads]

Injector sizing also depends on what fuel management you are using. If you are stuck with something like an AFC or emanage that alters airflow to get your correct fuel delivery, then you need to watch injector size so you dont get too much timing. If you are running something like DSMLink, an EMS, or other standalone, where injector size can be adjusted independently of timing, put in 850s or bigger. Size really isnt too critical for them, and just get an injector big enough so that you wont have to upgrade later.

Brad

Originally posted by Bigwilly6754
OK if u had a garret t3/t4 60 trim what fuel injecters would you run!???

 

[nigma]

thats a very very very bad idea to put in as big as possible injectors !!! you will not be able to stable idle with them. just imagine if you have 450cc injectors and you have something clsoe to 1ms (1/1000 of second) injection time, and you change injectors to 850cc that will make injection time close to 0.5ms what kind of injecors will be able to stay openned for that short period of time ? injector inertia will not let to do it and acuracy too. you will not be able to idle with this injectors on 4g63 unles you idle at 2000rpm or more

 

[nowayout]

I have to go bigger on injectors too. i concider 750 to be the max without a standalone,

I have a VPC and AFR combo.

 

[brads]

Originally posted by nigma
thats a very very very bad idea to put in as big as possible injectors !!! you will not be able to stable idle with them. just imagine if you have 450cc injectors and you have something clsoe to 1ms (1/1000 of second) injection time, and you change injectors to 850cc that will make injection time close to 0.5ms what kind of injecors will be able to stay openned for that short period of time ? injector inertia will not let to do it and acuracy too. you will not be able to idle with this injectors on 4g63 unles you idle at 2000rpm or more

You are wrong. You can easily idle with 850s, plenty of people using DSMLink and 850s will tell you that you dont need 2000 RPM idle like you suggest. Look at your injector on time at idle. There is plenty of room to decrease injector on time at idle, even with my 720s, I could go bigger, no problem. I have 2ms injector on time(after the injector on time is scaled for the larger injector), at 850 RPM, with 720s. That idle was as smooth as the stock 450s too.

Like I said, with a good fuel management system, its not a problem. Buy a big enough injector so that you don't need to buy them again if you upgrade anything else. 850s are good.

If you are using a piggyback, injector sizing is much more critical.

And 1ms is not a magic number for injectors either. That is VERY dependent on the injector itself, some are much quicker than others. Some disc style injectors would stay open for that 0.5 ms period you are describing, even though its not even relevant here, because idle injector times are much higher than that, as I already pointed out.

Brad

 

[mclaren55]

Go with 4 450's, and 4 780's!

 

[swordfish]

Or 4 X 800cc and 4 X 1600cc

Oh wait, guess I need to get my mind off an alcohol fueled 2.4L

jeff

 

[GSX4LIFE]

I wouldnt go anything under 750s. Big Injcs, and low duty cycles are nice.

 

[nigma]

i have stand alone and 650cc injectors and idle injection time is lower then 1ms with 650cc!!! at sequential injection mode(one inection per combution cycle that takes 2 revolutions of crank) imagine that at multi point where injection ocours few times per combution cycle this injection times will be even shorter, with 850cc injectors your injection time need to deliver right amount of fuel will be lower then 0.76s per combution cycle, divide that in 2 when multi point injection injects atleast 2 times per cycle and you have your self a problem... i speak not from hearings or anything i have actualy used that i know that, and 650cc injectors are enought for 450 - 500 wheel horse power(with slightly hier fuel preasure) do you plan to make more ?

 

[brads]

Your idle injection time is lower than 1 ms with 650s, but thats also with a higher fuel pressure, as you yourself said. If you did the calculations, how big of an injector with a 3 bar fuel pressure would they be equivalent to?

Also, if you set up larger injectors properly, you take into account that due to the size, they usually open and close slower. So if you went from a 450cc injector to a 900 cc injector, you wouldnt just halve the on time, you would halve it, then add a constant to it to account for the slower reaction of the injector. I checked my data logs with stock 450s, stock cams, and I was getting 2.1 mS injector open times at 850 RPM idle, with the ECU basically all set up like stock. With 720s, cams, and a 950 RPM idle, My injector on time is 1.9 mS, but the AF ratio is about the same. The 720cc injectors have a dead time that is 450 microseconds longer than the stock 450cc injectors, so that cuts the actual time the injector is open down to about 1.5 mS. Doing all the calculations on it, accounting for the higher idle airflow, it comes to just about the same air fuel ratio.

As for why I say go bigger than 650s, its because some people want to make good power on the crappy pump gas we are stuck with(91 or 93 octane), which requires you to run richer AF ratios than if you were running some higher octane gas, or race gas.

It certainly sounds like you are running that engine very lean at idle, compared to how they came from the factory. Maybe it is because you are running different gas there, than what we get in the US? Do you run a closed loop idle?

Brad

 

[nigma]

well you are right about gas we use here it is 98 octane so it is better and so on.. but i use 3 bar base fuel preasure i do not run 500 nor 400 HP at the moment so no need for hier fuel preasure and i do not run close loop idle, i do not have oxygen sensor on my car right now. i'll set up wide band later
for the moment i'm building T4 turbo then i might need hier fuel preasure...anyway 650cc injectors are more then enough for 99% of dsm tuners... there aint so many ppl that have more then 400whp. and 650cc injectors will do the work up to 400hp even on your gas

 

[brads]

I agree 650s are probably as big as most people need, but this guy was asking for injectors to match a 60 trim turbo with a goal of 450whp. With just a 50 trim, I nearly max out my 720cc injectors on 91 pump gas. Injectors ideally should be sized so you don't go over 85% duty cycle, both to make sure the injector has enough time to close properly before its opened again, and also so that you don't overheat it. It makes sense to put in a bigger injector than you need, as long as you keep it small enough so that it can still idle well. This means you don't come close to maxing it out at 400whp, and have more room to play with if you decide to go for more power. 850s are small enough to still idle well.

This does not apply to piggybacks where when you mess with your fuel mixture, you also mess with timing. Sizing for them is a little more tricky.


Brad