Rep Power: 0

I have search and i could not find a good answer, but what is the biggest size fuel injectors. I know some of you might be like y do u need bigger fuel injects, i need them because i making a custom turbo kit. I already have a T3 turbo and a PMS fuel system. And know i need to know what is the BIGGEST SIZE INJECTORS that can fit in our engine. THANKS

 
Rep Power: 0

PM Riceburnerex. He will know for sure, and you should get a fairly quick response.

 
Rep Power: 0

You can fit 1000 cc custom injectors if you want. Bigger is not better. You dont want to starve injectors or it shortens the life. Stock injectors are 248 cc. I have 310 cc prelude injectors on my turbo set up. You can go with s2000 injectors if you want or call up rc and have them customize you somthing.

Later, Phil

 
Rep Power: 529

Would there be any point to putting larger injectors on an otherwise stock engine?

IronFist

 
Rep Power: 420

Not really, but you'll run rich and make more power.

 
Rep Power: 0

What if you're not thinking of adding a turbo, but staying with the intake... what would be the best type of injectors? CC?

 
Rep Power: 0

actually running too rich decreased HP

 
Rep Power: 420

Well, it depends. The air/fuel ratio should be kept at 14.7:1 to burn all of the fuel and to produce maximum fuel efficiency, but the air/fuel ratio could be kept at 12.6:1 to produce maximum power. This is even more useful if you've advanced your ignition timing since you could run slightly rich to cool down the intake charge (since fuel acts as a sort of coolant). The leaner you run the more heat the engine produces, so the more likely the chance of detonation occuring. It depends on your setup and on what your goals are.

Air-Fuel Ratio and the SRF Air-Fuel Curve

Not sure what the size should be for injectors when not going with a turbo? I guess it depends if you can control their pulse width since just swapping them in is kinda pointless without tuning. Maybe tuning the stock ones will allow you enough adjustability to run at 12.6:1 throughout the entire rpm range?

 
Rep Power: 0

I think you'll have to do some ECU mods before you can get more ignition timing advance or much if any more fuel/air mix into the engine, no matter what size injectors you have.

 
Rep Power: 420

Actually, the ECU opens the injectors with by opening the circuit and running a certain voltage through them. Probably 12V. The duration of that signal is set in the ECU since the ECU expects the injectors to be a certain size. Our cars are probably set up for maximum fuel efficiency, so if you could choose injectors that are slightly larger than stock you could increase the ratio to be optimized for performance. Kinda a neat hack if you want to be all NA. That's assuming that the air/fuel ratio is optimized for maximum gas milege and that it remains relatively constant after the engine is warmed up. It probably does though, so this sort of modification may produce a nice horsepower increase. Say an extra 10 - 15 horsepower. Kinda expensive though since you'll need four injectors. Not to mention that the fuel economy will drop to something like 20mpg on average.

 
Rep Power: 529

Is there a downside to this?

+10-15hp =

IronFist

 
Rep Power: 0

All I see happening there is an over rich mixture with raw gas going out the tailpipe, and a poor running engine. In order to take advantage of bigger injectors, I believe you're going to have to do several other mods to be able to burn that extra gas. Playing with the fuel/air ratio by itself isn't going to add any power.

 
Rep Power: 0

yeah you have to do more then just put in new injectors, you have to have a good air/fuel which is ajusted and controled threw a computer and proper fuel pressure. to do it and get any benifits you need

A fuel management system
Larger injectors
fuelrail/ fuel pump (ajustable)
and some way of monatoring it
probably would want to upgrade your ignition too

this is all pretty pointless if you don't have a reason for more fuel delivery

You need a clean burn too, like bartkat said, fuel will just not burn and go down threw the exhaust if you are running rich. so don't expect it to pass emissions. You don't want to have unburned fuel going threw you catalytic converter.

about the only plus side to this would be to get rid of you cat and have that extra fuel coming out and your car could shoot flames but thats pretty hard on the car. and it's not like you could drive around shooting flame where ever you go.

you could build the block and shot a huge shot of nitrous and that would also need this fuel system upgrade. thats what I was thinking of doing sense I can't afford a turbo right now and when I get the cash for the turbo everything would be ready to go.

 
Rep Power: 420

No, see... That's exactly how it works. There's more than enough air going into the engine since the air/fuel ratio is probably close to 14.7:1 (the optimum air/fuel ratio for gas mileage); I.E. 14.7 parts of air to 1 part of fuel. Since (as stated earlier) the optimum air/fuel ratio for making power is 12.6:1; 12.6 parts of air to 1 part fuel. We can either decrease the amount of air going in to the engine or increase the amount of fuel going in to the engine to make the air/fuel ratio 12.6:1, but it's not possible to decrease the amount of air going in to the engine unless you have a vaccum pump that decreases the intake pressure below atmospheric. Haha. Anyway, you do it by increasing the amount of fuel that you inject.

I think that you shouldn't think of it as injecting extra fuel into the combustion chamber. There's only a certain volume of air and fuel that can fit in to the combustion chamber before compression. It's simply changing the air/fuel ratio. Anyway, now that I think about it simply changing the injectors won't be enough. The sensors in the header and near the cat detect the air/fuel ratio of the engine. The ECU will try to adjust the fuel delivery to keep the air/fuel ratio as it has preset in the fuel maps. You'de need something to trick the ECU into thinking that everything was allright. You need to read up on how those O2 sensors work. I think it's possible to use a resisitor to lower the output of the sensor and compensate for the extra fuel that you're injecting. Then you'll make more power.

The downside is more HC (Hydro-Carbon) emissions. You might not pass inspection. Also, fuel is inherently corrosive. It'll get past the piston rings and get into the oil (more than usual). It might build up in the intake manifold and you might get a backfire. It might cause corrosion of the header gasket (more than usual). Nothing serious though. Not at 12.6:1 anyway.

 
Rep Power: 0

I've seen cars tune the best to 13:5 ish. 12:6 is a tad on the rich side. 14:7:1 is only in theory IMO. Trying to tune for this on thewest coast with 91 octane is asking for detonation. This is speaking for NA. Turbo I agree in the mid to low 12's AF ratio for a street car

 
Rep Power: 0

Grey,

This is proabely somewhat before your time, but the application is still the same. Consider the manual (or automatic) choke on cars made prior to fuel injection. Also consider larger carb jets, more barrels on carbs, etc. It's all the same principle.

 
Rep Power: 420

Yeah, I agree. Going beyond 12.6:1 air/fuel ratio doesn't increase horsepower. That's how chokes work in lawn mowers for example.