I tried doing the calculator thing... but to be honest I don't understand what half of the calculator specs are...

My mods...

LQ4 6.0L 364c.i.
224/224 .581 114lsa
AFR 205 (59cc)
11:1 or 11:2:1 compression
Bolt-ons

446rwhp/416rwtq

currently i've got the stock injectors... my engine builder told me i'm on the edge of maxing them out with the HP i'm pushing...

if I did the calculator right, it said i needed 39# injectors... this right?

what brand is better?

I know nothing of this area of the car guys

 

You will be good with a set of 42's and still have a bit of room to grow. Thunder Racing has the Delphi's for a great price.

 

I would get a set of 60s because you never know what the future might bring. They are not that expensive either or hard to tune.

 

60s without a doubt are the way to go. I like the Mototron or the Fast injectors.

 

if i get the larger 60's, does that mean my fuel mileage will be less than the 42's?

This car is a DD guys... not a drag strip queen. And to be honest i'm completely satisfied with the power I currently have. Just wanna make sure i'm not shorting my engine the fuel it needs

 

A very good option is the FAST 36lbers. They are 40lbs at 4 bar and will easily meet your requirement. These were used by GM in the ASA motors, so all of the injector tables for the PCM are readily available.

 

can you explain what you mean by this?

 

These injectors flow approximately 36 lbs/hr at 3 bar (43.5 psi) and the LSx injection system runs at 4 bar (58 psi). So using these injectors at 4 bar increases their flow rating to approximately 40 lbs/hr.

 

Define hard to tune, define you reasoning for making him buy 60# injectors along with buying a fuel pressure regulator and setting it up instead of just buying 42# injectors and being happy.


DO NOT DO THIS. on a stock car without a FUEL PRESSURE REGULATOR YOU ARE ASKING FOR IT!
you will idle rich and wonder why, your car may stutter and you may wonder why...etc

 

If you are positive that the power level you are at now is all you want out of the car, then you will do fine with the 42s.

 

I would do the delphi 42s or even the ford red top 30 lb/hr which are actually ~34-35 at our fuel pressure. The ford red tops have injector offsets that are close to the stock injectors so just modifying the injector flow rate table will get it pretty close. Do not buy 60 lb injectors.

 

I don't have to define crap to you! Who the hell you think you are? Re-read my post freak!

 

In my web site is the math, and/or spread sheet for sizing injectors for your projected HP goals. Also, an easy How-To on rescaling said injectors. Check it and you may gain some insight.
Robert

 

I did not mean to jump on you like that BUT here is what would happen from you simply stating about getting 60#ers.

he would go out and buy them thinking oh hell yeh I got enough injectors for whatever mods I want and even now they will work fine...
then plug them in tune them and wonder why in the hell he is running 11.0 AFR at idle.

SO Please explain your statement about 60#ers if you are going to mention getting them on a somewhat stock car and what you would have to do to control them properly with a stock idle airflow (basically) so that you wouldn't idle rich.

The problem is people just go out and say just like you did about 60# injectors and I have been on these forums for almost 6 months now explaining all this injector stuff to people who have listened to others say just get 60#ers and then they wonder wtf is going on with their car at idle and I actually explain to them how it all works and they then understand it.

this is all the reason I have updated my STICKY in this FUEL AND INJECTION topic. I will make a write up to make sense of RC's page on injectors so that people can better interpret it, as I have got several people stating they don't understand how it works either. So that is my next plan.

 

OK my bad. I was out of line. But he said that his calculations said he needed 39 lbs of injectors. Instead of going for the 42s, I would then have gone straight to 60s. On the idling rich part then thats where I pay my tuners the big bucks. Some tuners I have worked with did not have a clue about what they were doing either.
I was one of the ones that started out with 42s, to then have to turn around and get 60s because I was maxing out my 42s. Double the effort and double the money. If I would have known I was that close at the beginning It would have been a different story.

 

his car is n/a yours is forced induction

 

Thats a ton of power for a DD. What size injector does the LQ4 use? Go back to your engine builder and see what he has to say and his recommendations.

 

Let's step back and look at the required size injector based on the inputs above. Assuming horsepower levels will remain constant for the near future, you would need an injector that is rated at 34 lbs/hr @ 3 Bar and use 4 Bar of fuel pressure to adequately fuel the car and stay within the 80% max duty cycle recommendation.

Here's the calculation:


So, looking at commonly available injectors on the market. A 36 lb would be the closest to your current requirement and has a little growth potential. A 42 lb would give you very significant growth capacity. This is all assuming you stay naturally aspirated. If you change to forced induction, the calculations significantly change.

Clear as mud?

HTH,

 

thanks ALL OF YOU so much... even with the bickering, I still got some good info out of it all

405HP_Z06... I'm looking at the specs you inputed on your program... my peak HP is at 7000 not 6000 if that makes a difference, and we just transferred my stock LS1 injectors/fuel rails over to the LQ4 engine... completely stock fuel system...

even with the changes I just mentioned, I think you are all right, and the 42's still look like a good injector...

here's my dyno graphs... if they matter for any of this...

 

Looking at the above posted graphs it looks like the peak is at 6400, unless I'm crosseyed from being so tired. I reran the numbers and the calculation didn't change except for the current duty cycle, no big deal. I edited the image to reflect 7000 rpm as peak HP.