From what I read it seems that custom tuners will lean the ECU/engine to achieve more power. So why are larger (380s or 400) injectors installed for more power, providing more fuel?

 

I bet it seems counter intuitive to you doesn't it? But is is true....and many do 440 or 500 or even 550 with good results and a tune. It has to do with scaling the injectors....bigger injectors do provide more fuel....but without a tune, they can provide too much and the car will run richer than optimum. The car can compensate using its fuel trim system and the o2 sensors to lean or enrichen the flow by about 20%..... However under High RPM with pulleys...more fuel is needed, more fuel than the stock injectors can provide.....to be a bit more technical it has to do in part with the pulse length the injectors squirt...the faster the rpm's, the less time the injectors have to squirt....even less to inject it at an ideal time. So bigger injectors work better....make more power, and often can get similar fuel economy when tuned.....sometimes....depends on the goal of the tune.....most go for HP. So bigger injectors do allow a car to make more power, by burning more fuel......if you are from the days of carbs...it is like re-jeting a carburetor....as long as you can flow more air to match the fuel...you will make more power...just slightly more complex due to computers!!

 

Makes sence.....Thanks!

 

Good write up Tim ! Even I can understand it

When I added my JCW 380's I had a definate loss in the MPG department. But gained more power and drivability for sure. My OBC kept reading great fuel mileage because it was not accurately measuring the pulse length of the "squirt". So even though the OBC said like 34 mpg was actually getting around 28 I think.

I have a Unichip and will try that for now. But ultimately a remote tune by Jan or the JCW disk from Inksip are on my short list. If I do the latter, I will have an extra set of injectors and an extra JCW Airbox to sell

 

Yep good write up! Basically a 340 injector can deliver the same amount of fuel say a 380 will, but it takes longer. With a larger injector and the air to match it, you can deliver more fuel and air (more boost) in a shorter amount of time. More fuel burned = more HP! Of course a good tune is more than just leaning the motor out......

 

Question-I am having a thumper head put in today- I have the stock inj. in now but have the 550's and was waiting for a tune- Should I put the 550-s in now w/o the tune or leave the stock and wait for a tune( may be awhile) -- 06 s - thumper head,cam,headers,exh. etc---thanks

 

DO NOT INSTALL THE 550's.
the car will not run...or will run so poorly it will barely be drivable.
The car can using the computer compensate for about a 20% change in the injector flow...so 380's or 400's is about the max you can do until you get a tune. Abouve that the var will run poorly, throw warnings, lights, etc.