Stock Injectors

[Alpha D]

Question is pretty straight forward. I was curious as to whether one could achieve similar flow as in close to, or the same flow the 560cc Evo injectors (or 510yellow tops) In combination witha stock fuel pressure regulator....out of 450cc stock injectors in combination with a aftermarket FPR and of course up-ing the base fuel pressure....

I could sit and do the math, with my school book but am more interested in precautions of doing such....basically why its a bad idea or why it wouldnt be the best thing to do and if it is possible roughly how much more psi would be needed to gain the same flow in cc by tweaking the Fuel pressure.

*For the ones that are curious why i would even want to achieve such a trivial matter...well i have one faulty injector, (Straight busted lower plasttic piece) but do not feel like purchasing a complete set of new 560cc injectors for 100+ but i do have a Aeromotive fuel pressure regulator and wouldn't mind picking up a stock set of injectors, i might just dig around the garage and find a set....and run those until spring season comes around and E85 injectors go back in. If this idea might work... Plus i would like to know just for laughs and gigglez.

I do know that some people have figured out what bare minimum size injectors to use for e85 in combination with only safc by just making minor adjustments. & i figured, wow that is a very practical way of figuring out different combinations and getting the best results out of your set up.

Anyways at worst scenario it will be a simple ''No where near'' or interesting experimental ideas. Chip in what ever you know...ill be searching the internet as well because i have a strong feeling im not the only one that has wondered such a thing. 100cc just dosnt seem that much to me...?

[JET]

You can, but your fuel pump becomes less efficient and you can run in to issues with the injectors if you run too much pressure. You will need to run 20% higher pressure to get there assuming your pump can handle it, so ~46 base pressure if it is the 1g in your profile. If you keep the boost low you can probably get away with it if you have an upgraded pump.

[Alpha D]

Dual walbro 255lph dedicated 12V power source...or the separate relay style set up deal which ever the correct terminology for it is.....Im really curious all of a sudden just how much can be squeezed out of those small smurfs ha. Currently at 18PSI...and i should change my profile picture its out dated anywhos -.-....with that being said what do you think JET?

[asshanson]

Looks like you'll need to run about 59psi base pressure to simulate 560cc injectors. 20% more pressure doesn't equal 20% more flow.

http://www.csgnetwork.com/fiflowcalc.html (450cc = 42.8 lb/hr, start with 38psi base pressure)

[Alpha D]

Now that's quite a bit of pressure, but at the same time i dont think it is ...and im saying this because (Now correct me if im wrong) for every pound of Boost pressure you run youre adding one PSI to your base fuel pressure correct?...Im not sure if thats the exact relationship, but i do know that Boost or manifold pressure somehow effects fuel pressure.

Now with the 59psi of base pressure plus 18psi of boost pressure we come to 77psi under WOT...ill have to go over the math again and post later for verification, but take for example my e85 set up 1450cc injectors dual fuel pumps but only about 45psi i believe and 28psi of boost equals 73 psi...am i correct to say that based on that math there shouldnt really be any bad side effects to running a higher fuel pressure?

Now doing this i would probably have to pay attention to my afr's? what other things should i keep an eye on...i was basically just gonna go by the feel of the car...i only have a narrow band installed currently and well that dosnt tell me how rich or how lean i am heh lol

[Shane@DBPerformance]

If you want a true 560cc you need to go even farther. Injectors are rated at 43.5psi, the 1Gs run a weirdly low base fuel pressure for some reason. To get the full true 560cc you would need to crank the base fuel pressure up to 67psi, but 59psi would emulate dropping 560cc injectors into a stock 1G fpr setup.

[Shane@DBPerformance]

The main downside to running high pressure is that fuel pump flow usually drastically falls off the higher the final fuel pressure is. Some injector also have problems at really high pressures and they also don't how much the math says they should at higher pressures.

[Alpha D]

Originally Posted by Shane@DBPerformance

The main downside to running high pressure is that fuel pump flow usually drastically falls off the higher the final fuel pressure is. Some injector also have problems at really high pressures and they also don't how much the math says they should at higher pressures.

With that being the case (maintaining full flow)...does/would that mean that pressure also might drasticly drop off? As in it wont be able to maintain the pressure ? Because without flow there is no pressure? and with no way of knowing what your Fuel pressures drop of to....(no fuel pressure gauge inside the vehicle) it seems very un advisable to attempt this...even though the part about simply running 59psi of base pressure dosnt concern me as much as the 67psi...

(Again idk if either can be consider safe or unsafe) Im just out of the realm of understanding and experience to calculate the potential ''oopsy's'' maybe this is an experiment that should be conducted on a dyno or so ? Not while daily driving the car ha

Since the injectors also play a big role in how much flow they can handle or how much pressure behind the fuel that is being pushed out of them would a more quality injector put a different spin to the situation?

[Shane@DBPerformance]

When flow runs out then pressure drops.

[asshanson]

Was your car running 1g base pressure or 43.5 when it was tuned on the 560cc injectors? That will tell you if you need to run 59 or 67psi base.

Either way I wouldn't recommend it, aren't the 560cc injectors pretty cheap?

[Alpha D]

Yeah most go for a hundred bux a set, i was just curious as to how well the theory would work in practice. Things always seem alright on paper untill you try it...and yep it was stock fuel pump .... hmmmm

[Alpha D]

Also for you gus with all the tuning software and know how to self tune or dyno tune, its not often almost ever I hear of fuel pressure being increased to get more flow out of an injector once its reached max duty cycle or w/e maxxed out injector means...how do you figure out what is to much pressure for an injector? because for example: If i just buy a set of injectors... the company dosnt know what pressure my car runs....Is there a standard or so? Never bought brand new injectors (i assume the instructions would shed light on that?)

In school we learned that most modeen vehicles have like a min of i think it was 60psi...its been to long i do not remember the generalized psi spec that was given..however the point is there was a standard which most new cars hovered around..

I know direct injection cars like the newer cobalts run a much higher base fuel pressure, granted the injector design might be different and cant be exchanged ...with a dsm injector clip..or that of a toyota..... So lets just say... hypothetically speaking they could fit...wouldnt yu get a different cc rating or fuel flow? lol if you purchased a aftermarket injector

[Shane@DBPerformance]

Standard pressure is 43.5 psi aka 3 Bar, which is the pressure that most injectors are rated at. You usually aren't going to have problems with running too much pressure on a fuel injector or them starting to act weird until above 100psi.

We sometimes raise or lower fuel pressure on cars on the dyno to either get more out of the injectors or more out of the fuel pump. For example if someone has way too much injector, but not enough fuel pump, then we might run a lower than normal base, but if you go too low then atomization suffers and you can start getting a funky idle/low throttle.

Often people don't play with it much though, because it requires making changes to the entire tune whenever you change the base pressure. Like if you run out of injector towards the end of a tuning session, then decide to raise the base 10-15psi to make the injectors bigger, then you need to go back and retune the idle and part throttle again.

Direct injection cars run fuel pressure in the thousands.

[asshanson]

Most injectors are rated at 43.5psi. However, some specific to a platform can be rated at that pressure, like a lot of vette injectors are sold with a flow rating at 60psi, probably just for marketing purposes.

[Shane@DBPerformance]

Yea, GM injectors are often run and sold at 4 bar. So a 60lb/630cc injector for GM would be a 550cc injector if run at 43.5 psi base fuel pressure.

[19TsiAwd90]

Originally Posted by asshanson

Most injectors are rated at 43.5psi. However, some specific to a platform can be rated at that pressure, like a lot of vette injectors are sold with a flow rating at 60psi, probably just for marketing purposes.

s10's(aswell as all 4.3l vortec motors)use a weird type of injectors called spider injector, and they run 60+psi of fuel pressure. They are VERY picky about fuel pressure when a pump starts getting weak they WILL NOT start(i know from experiance T.T). im sure there are other platforms that use higher pressure too, i guess Vettes use the modern day injector so this might not even be related. just thought i would share something.

[Alpha D]

This is amazing, thank you guys ! I feel like i actually learned something hehe! In conclusion with all the input: ''It is NOT a smart idea to raise my fuel pressure nearly 26PSI to get more injector !'' Reason being it will throw my whole Tune of balance...which makes perfect sense ! Theory is proven to be none practical in this scenario...sucky !

Most injectors are designed around a 3bar spec that answers the question i had!

[Alpha D]

Originally Posted by asshanson

Most injectors are rated at 43.5psi. However, some specific to a platform can be rated at that pressure, like a lot of vette injectors are sold with a flow rating at 60psi, probably just for marketing purposes.

Marketing? Which sort of marketing are we talking about? Like aftermarket or dealer...im assuming aftermarket since i dont see why they would use that in the performance spec as a point of sale dealer wise? Sounds like it would be over the head for most consumers?

I consider my self an enthusiast and i didnt even know head from tail well...

If i do ever feel adventurous though, im safe playing around with fuel pressure up untill or close to 100psi roughly...granted the whole tune will have to go hand in hand. With this new knowledge gained, I will have to decide on an injector size, for the up coming E85 season... since i sold my 1450 FIC i wonder if 1000CC will support 400WHP...but thats a discussion for another day. Not to mention i know for sure there is an equation for figuring injector size out...

I remember the first book i read called ''How to build a high performance mitsubishi engine or 4G63T'' had all kinds of interesting math in it. Again Thank you guys !

[asshanson]

Originally Posted by Alpha D

Marketing? Which sort of marketing are we talking about? Like aftermarket or dealer...

Aftermarket. If they rate them at 60psi they look like bigger injectors.

Originally Posted by Alpha D

If i do ever feel adventurous though, im safe playing around with fuel pressure up untill or close to 100psi roughly...granted the whole tune will have to go hand in hand. With this new knowledge gained, I will have to decide on an injector size, for the up coming E85 season... since i sold my 1450 FIC i wonder if 1000CC will support 400WHP...

1000cc injectors could probably get you close to 400whp on Shane's dyno. Your Walbro pumps won't like 100psi, they start to really taper off after 75-80psi. Look at this flow chart (13.5v brown line):

[Alpha D]

Originally Posted by asshanson

Aftermarket. If they rate them at 60psi they look like bigger injectors.



1000cc injectors could probably get you close to 400whp on Shane's dyno. Your Walbro pumps won't like 100psi, they start to really taper off after 75-80psi. Look at this flow chart (13.5v brown line):

Where did the graph go? or are you referring to the previous link...didnt see one there either? Yeah its time to look into a new fuel pump set up as well i think...not to mention all the nightmare story's ive read about with one pump throwing in the tower mid pull through causing a sudden change in afr's sometimes to fast to let of and engine damage occurring.

What monster pump's do people even run now a days. I know map sells those DW300 or something weird pumps...and i also hear of import image selling some sort of Bugatti veryon pump that gtr's seem to like ect ect