Can Injectors be too big?

[rory]

As the title states, Im looking to upgrade to larger injectors (510cc) with supporting mods.
What im wondering is, is there any adverse effects by going alot larger in the first place.

Prices for say 510's and 1000's are similar enough and Im basically just looking to save money by not buying multiple sets over time, if i one day need to go larger.

Thanks

 

[khubner1]

Well not really if the tune is right.

 

[bazeng]

In my opinion, yes.

You ideally want an injector that makes your required power at 80 percent duty. This will allow you the best idle quality while proving enough fuel for max power.

Of you plan on going bigger later, get injectors to suit your later goals but keep in mind that you well lose idle quality.

By idle quality i refer to higher injector duty during idle which usually means better control. It also depends significantly on ecu.

 

[rory]

Ok, we'll I don't have any plans so far to require bigger, but we all know how it is with cars.

My plans are to install E3 ecu and afm, to go with my E3 turbo and exhaust.
So I should probably just stick with getting 510cc injectors?

 

[justgsr]

From what I know, "the bigger the better" but the bigger it is the harder it is to tune for low rpm,Idle and cold start and that. Ideally you would listen to what blazing said.

 

[brisvr4]

With what you are planning on installing I'd just stay with the 510's for now.
I run ecmlink with 2150cc injectors on E85 and it idles and behaves itself at part throttle like a stock car.
As mentioned it really comes down to what your goals are for the car.

 

[rory]

With what you are planning on installing I'd just stay with the 510's for now.
I run ecmlink with 2150cc injectors on E85 and it idles and behaves itself at part throttle like a stock car.
As mentioned it really comes down to what your goals are for the car.

wow!

Should i also be looking at upgrading the stock fuel rail ?

 

[evo-gsr]

No...stock fuel rail is capable of handling what you have in mind plus a lot more.

 

[bazeng]

The stock rail is fine.

Just make sure you check fuel pressures. If using a larger pump, you may encounter fuel overrun at idle. The outlet of the reg is small so if your pump flows a lot of fuel, your fuel pressure may be excessive at idle causing it to run richer and will require a lower duty cycle to run at a satisfactory afr.

Once again, the lower the duty on an injector, the poorer the performance. Your aim would be to increase duty at idle which well give the injector better control.

example: if you had a base pressure of 42ish psi, your injectors may need to rub at 4 percent duty to idle at 14:1 afr.

If your fuel pressure was 52psi and you could not reduce it, in order to achieve the same afr, your injectors works have to work at a lower duty otherwise you would probably run rich. So say without identifying injector or engine size, your injectors now need a duty cycle of 2 percent to idle at 14:1, (not calculated, just example), once again pending injector type and ecu type, you may run into problems such as injectors operating out of efficient duty cycle zone causing poor and inconsistent spray pattern or ecu not able to provide closed loop control at that low duty cycle (they can be limited and only activate closed loop once duty hits a specific percentage).

Hope that makes sense, just fed my daughter and can't get back to sleep...

 

[bazeng]

I have run 800cc, 1000cc, 1600cc, 2000cc and now 2350cc injectors.

I can honestly tell you that the smaller the injector, the batter the idle and cruise. Although the larger injectors work fine, tuning is much easier on the smaller ones. This results in leaner air fuel ratios which is what you want when chasing efficiency and economy.

To obtain the best of both worlds (idle, cruise and power delivery) a staged setup would be ideal. 1st set for your cruise, idle and low power stuff while the 2nd set comes on when you fang it.

 

[bazeng]

With what you are planning on installing I'd just stay with the 510's for now.
I run ecmlink with 2150cc injectors on E85 and it idles and behaves itself at part throttle like a stock car.
As mentioned it really comes down to what your goals are for the car.

Remember, e85 requires approx 40 percent more fuel to standard gasoline. So your injectors would be great for e85 but way oversized for gasoline.

It would be like running 1290cc injectors on 98ron fuel.

 

[OLDIE]

I have Bosch 780 inj ,stock FPR and was all fine until the pump died so installed an 044 pump and it is overfueling and starts missing >3000 if I plant my foot a little so am booked with tuner to remap the E6X and wondered if I needed an adj FPR or should the stock one be fine??

 

[bazeng]

The tuner might be able sort it out vis the tune but you would be able to fix it yourself with a fuel pressure reg. Which one is cheaper?

 

[OLDIE]

The tuner might be able sort it out vis the tune but you would be able to fix it yourself with a fuel pressure reg. Which one is cheaper?

Thanks Baz don't trust myself, do trust tuner as he built motor and tuned it as well so I guess he will do the remap.
Hope you get a better nights sleep tonght.

 

[EVO-00X]

Dont go too much bigger than what you think you will need for upcoming mods. It just takes up more time in tuning and getting idle right like Baz was saying. Some bigger injectors cant handle the lower end of the scale and will dribble fuel at idle instead of spray a nice consistent pattern, which in turn will give you poor idle.
Stock frame TD05 turbo sizes on 98 pump should never need to go anything higher than 700cc injectors IMO.
I think these days on our cars, with any kind of turbo running 98 pump up to 30psi on 1000-1200cc injectors, that as soon as you have E85 available to you in your area (say within a 20km radius of your home), go visit your tuner and start shopping for some bigger injectors. Else you can store E85 at home but not many people are cool to do that with anything larger than an air tight 10-20 litre manageable-size container only as they have to use it before the E85 goes off.

 

[caged]

Iv got an evo 9 with a vipec ecu on 2200cc bosch's that idles like factory 750rpms at 0.7% duty cycle 14.7:1 AFR on caltex fuel flex. If you have a good ecu and injectors Its not a problem at all.

Remember, e85 requires approx 40 percent more fuel to standard gasoline. So your injectors would be great for e85 but way oversized for gasoline.
It would be like running 1290cc injectors on 98ron fuel.

Iv found caltex fuel flex (tested E80) is more like 26-28% more over the last 4 cars iv done recently.

Else you can store E85 at home but not many people are cool to do that with anything larger than an air tight 10-20 litre manageable-size container only as they have to use it before the E85 goes off.

We store 360L of Fuel flex in air tight 60L steel drums for up to 3 and a half months at a time and have not seen any going off.

 

[rory]

Thanks heaps everyone.
There is a wealth of info here , to be honest its slightly overwhelming. Haha

I really don't have any intentions for going past the stated mods atm, and I'm not intersted in dragging or anything where I would need ridiculous hp, just looking to get the most from the td05 upgrade.

After reading through all of this (about 20 times) I'm guessing an afr gauge would definitely help me out.

Also once the evo 3 parts are all installed is there any actual tuning that can be done with a stock ecu?

Thanks again.

 

[evo-gsr]

You will need an ecu with a chip in it or ECM lite to be able to tune it

 

[rory]

I have a unichip piggyback lying around somewhere , and CNJ up here specialize in them.
Would that be sufficient ? If tuning is required.

 

[4piknup]

I have Bosch 780 inj ,stock FPR and was all fine until the pump died so installed an 044 pump and it is overfueling and starts missing >3000 if I plant my foot a little so am booked with tuner to remap the E6X and wondered if I needed an adj FPR or should the stock one be fine??

Caged had a link to some fpr mods to stop the overfueling that will work if you are over running your fpr