Oversized Fuel Injector

[othebe]

I'm a little lacking in my knowledge of fuel injectors so was hoping to get some information on it.

I'm currently running a full Tyga exhaust with an open airbox + PCV AutoTune module. Given I've set my AFR to 13.2, I would assume you'd need a certain amount of fuel to meet that ratio. Why would a bigger injector help? Is it that the original just can't cope with the amount of fuel required, or that is stressed under high loads?

Does a larger injector have a larger diameter allowing for more fuel to come through, or is some other type of mechanism? If so, any idea what the diameter/size/cc difference is between the original and the oversized?

Given my setup (exhaust/airbox/PCV/autotune) under a target AFR of 13.2, would an oversized injector provide more HP?

Also, is this the part? https://store.grayareaktm.com/product-p/233u-350.htm

Would love to hear you guys opinions, and sorry if these questions are supposed to be trivial knowledge. Thanks!

 

[Fangfactor]

Thats a good question, I was also wondering the same thing

 

[chevaliernoir]

That's a good question indeed.
Here are some answers ... And additional questions...

In order to get more torque/power you need to burn more air/fuel mixture.
With optimized intake/exhaust you succeed to put more air, so now we need to put more fuel.

The injector is just open or closed. Not in between.
So if you want to inject more fuel, you need to open it a longer time.
This is what PCV is doing. And it works well.

The issue is at high rpm : you don't have the time to inject the fuel quantity you need.
Note that at 12000 rpm, the maximum time available is only 10 ms. (And even during this time, the engine intake valve is open about 3 ms.)

In order to inject more fuel during a reduced time, there are different possibilities
The one commonly used on our bike, is to use a bigger injecter. This means, as you foresee injector with bigger hole. So for the same duration more fuel flows.
One of the issue (there are other....) is that this will happen in any condition, so it will impact the complete rpm and TPS range.
An other solution would be tu have 2 injectors. This is the solution used on powerfully V2 or V4 at Ducati or Aprilia, for example.
The third solution I see (and that I like the most) is to increase the fuel pressure. Then, even if the injector is the same, there is more pressure to push the fuel throw the holes, so the flow increases. But in order to add 20% flow, for example, you need to increase the pressure by 40% (that is already quite a lot)

I wrote I'm not a big fan of using a bigger injector. One risk is a wrong targeting.
I mean the injector does not only open and close, it also generates a spray pattern. It could be sometimes very wide (shower injector) or very narrow to Target only the intake valves.some injector don't even have the spray in their axis but bent in direction of valves. This targeting is very important for emission (but we don't care), but also for drivability and throttle response. If most of the fuel you inject just make the intake manifold wet, that will influence the nature of the fuel you will burn (small drops from the injector, or very big drops flowing along the intake manifold)
There is an other important parameter on injectors, it is the size of the droplets. Good injector has very small droplets. Bad injectors has big. This influence the combustion, influence the startability, emission... And sometimes power.

Don't take it wrong, i don't say it's a mistake if you go for bigger injector.
It seems everybody is happy with that so I have no doubt it's a good solution if you lack fuel at high rpm.
Just that I would be interested to compare spray of original and high flow.
I imagine the spray is good for our application.

If I miss fuel, on my side, I will go for higher pressure (it s cheaper and without risk of wrong targeting)

 

[John390]

you HAVE to have a larger injector if your engine needs more fuel. The stock injector can only go so far. It can only deliver so much fuel.

If you have an open airbox, full exhaust and the higher flowing intake runner, you WILL need a bigger injector. No questions needed.

You can get a good quality one, and one that people have used and we know works.

There have been many dynos before and after.

If you run it on the stock injector and you need a bigger one, you will probably damage the engine.​

 

[Superpacman13]

I'm a little lacking in my knowledge of fuel injectors so was hoping to get some information on it.

I'm currently running a full Tyga exhaust with an open airbox + PCV AutoTune module. Given I've set my AFR to 13.2, I would assume you'd need a certain amount of fuel to meet that ratio. Why would a bigger injector help? Is it that the original just can't cope with the amount of fuel required, or that is stressed under high loads?

Does a larger injector have a larger diameter allowing for more fuel to come through, or is some other type of mechanism? If so, any idea what the diameter/size/cc difference is between the original and the oversized?

Given my setup (exhaust/airbox/PCV/autotune) under a target AFR of 13.2, would an oversized injector provide more HP?

Also, is this the part? https://store.grayareaktm.com/product-p/233u-350.htm

Would love to hear you guys opinions, and sorry if these questions are supposed to be trivial knowledge. Thanks!

The original injector doesn't posses enough of a "hole" to pass enough fuel to fit the requirements of that setup. A new injector with a bigger "hole" will allow your fuel system to meet the needs of the modifications you have installed. I have still yet to have a stock injector cc tested but we settled on the current size as it will suit the maximum amount of fuel needed for a full blown superbike on MR12. Most don't have this setup but some do so its easier to size down the injector with a tune then make it bigger!

 

[othebe]

Thanks for all the information. Superpacman13 can you elaborate on what you meant when you said "its easier to size down the injector with a tune"? chevaliernoir mentioned that an injector is either in an on or off position, but this sounds like it could run in between?

Also, two more questions:
- Would running the oversized injector mean lower fuel economy since we're shooting more fuel and running rich?
- It sounds like the higher flowing intake runners would need the oversized injectors. Since the RC390R already comes with the high flow intakes, does it still need the larger injector?
- John390 can you point me to the dyno results you mentioned? I can't seem to find them, perhaps I don't have the right keywords?

Thanks!

 

[John390]

If you run an oversized injector that is of good quality and only as big as you need (bigger is not better) your fuel economy will not suffer. You will have to tune it of course using an aftermarket addon computer or a flash tune by someone who knows what they are doing.

Once this is done, your fuel economy will be as good or better than stock. yes I did say better. Every car I have tuned has gotten better mileage than stock. My bike is no different. Once you increase the efficiency of the system(reduce restrictions, tune runner lenghts etc|) your engine can work less hard to move the mass of bike and rider. It can also work less hard just holding it at a set speed while cruising.

I don't know exactly where the dyno results are, but there are some on here and on the Duke 390 forums.

Anywhere from 5-8hp to the wheels. My biggest factor in knowing that these parts work IS that you need more fuel once you have done all of the supporting mods. If you could get away with the stock injector, I'd say that maybe the intake runner wasn't that big a deal. But we know that the stock injector runs out of fuel around 7k rpm once you put the runner in with an open box and open exhaust.

and no the R bike doesn't need a bigger injector because it has a closed airbox and restricted exhaust. To need more fuel, it needs to have all 3 parts installed.

 

[othebe]

Thanks for that informative post John. So what I'm understanding so far is that even though the injector is either ON or OFF, the ECU/Powercommander controls how much fuel is actually sent through the injector. So running a larger one doesn't necessarily kill fuel economy, but just lets you tune it further.

 

[John390]

yes, the injector is either closed or open.

how the fuel is metered is by how long the injector is open.

The injector is duty cycled from about 10% to about 90% This means that at 50% duty cycle its open as long as its closed. At idle its closed way more than it is open, and at WOT and higher rpm its open quite a bit more than its closed. Running an injector at 100% duty cycle is bad for the injector

If you open it for a longer time, it will spray more fuel, simple.

now, keep in mind that the time we are talking about is very small amounts of time. It has to spray before and or when the intake valve is open. This is only a small amout of time as the engine is spinning quite quickly, even at idle.

Most duty cycles are measured in miliseconds.

 

[Vitboy]

i'm also lacking knowledge with the relation between the bigger injector and the ECU.

I have the injector from Gray area but i have not yet installed it. My dealer finally refused to install it so i will do it by myself.

As i'm new with these stuff, i'm wondering how the bike will start with it ? Is there a risk of having too much fuel for the bike to start ? Or do you need a special map on the bike before install it ?

Also does anyone have tried it with a rapid bike evo ?

Sorry if my questions are dumb but i don't want to install this for nothing.

 

[ZachNap]

i'm also lacking knowledge with the relation between the bigger injector and the ECU.

I have the injector from Gray area but i have not yet installed it. My dealer finally refused to install it so i will do it by myself.

As i'm new with these stuff, i'm wondering how the bike will start with it ? Is there a risk of having too much fuel for the bike to start ? Or do you need a special map on the bike before install it ?

Also does anyone have tried it with a rapid bike evo ?

Sorry if my questions are dumb but i don't want to install this for nothing.

I installed the oversized injector and didn't get it tuned until a few weeks afterwards. The ecu seemed to do an alright job dealing with the injector, I would definitely get it tuned sooner rather than later if you put the injector in. my local tuner said he was surprised with how well the ecu handled the extra fuel. I'm also running a powertronic ECU, my Turner's only complaint about the ecu is that the map is a little resolution but besides that it's good.

 

[musti]

Thank you everyone for sharing your thoughts and experience about oversize injectors.

I found a link:
https://store.grayareaktm.com/ProductDetails.asp?ProductCode=233U-300&CartID=1

Would this be it?

Instead of buying an oversized injector, can I modify my stock injector?

 

[musti]

For me to get it shipped to India, it is pretty expensive. I will also be charged custom on this...

 

[ZachNap]

For me to get it shipped to India, it is pretty expensive. I will also be charged custom on this...

View attachment 6591

That's the one I got, its a little expensive but its absolutely worth it.

 

[musti]

That's the one I got, its a little expensive but its absolutely worth it.

Thanks for your feedback.

We both have a similar setup except for the fact that I have the Competition wereks exhaust.

Getting I have to pay customs when item imported to India. Can these guys hook me up with a lower cost invoice so that I dont have to pay a ton of money for customs?

I didnt find a customer support page on their website.

 

[Superpacman13]

Hi there, Where the shipping option says UPS select the more options category and you will see USPS and the rate will be much more agreeable.

 

[musti]

Hi there, Where the shipping option says UPS select the more options category and you will see USPS and the rate will be much more agreeable.

Thanks for replying.

Customs and duties is charged on the total of the retail + shipping

Is there a way I can pay the retail, but you can print / provide an invoice of a lower retail price?

 

[Superpacman13]

No, that is fraud

 

[musti]

ok

 

[musti]

Hi there, Where the shipping option says UPS select the more options category and you will see USPS and the rate will be much more agreeable.

What is the difference between the stock injectors and your over sized? Can you please share some specs information and the direct link to purchase the item from your website.

Thank you.