Larger Fuel Injectors For The XX

[XX4me]

(Updated with current info 11-30-03)

Thought you guys might find this interesting.

There is speculation that our stock XX injectors are in the 250cc per minute/23lb per hour flow range. This equates out to a max horsepower of around 225 before the injectors start malfunctioning caused by excessive duty cycle. This is to say they may not allow enough fuel at high RPMs and boost levels. Even at 200 horsepower they are working above their desired range. So what we need is an injector that flows more fuel than stock without having to do modifications of any sort and since we're using a PCIII and fuel pressure regulator we can adjust down to compensate for the higher flow rate when at low RPMs. This will allow running 200 horsepower at a reasonable duty cycle, or more in my case, without any fear of running out of fuel causing a lean/heat condition because the injector failed.

After some research I found that Keihin, the company that made our injectors, also made six other flow rates for the same style injector. If you look at the Keihin-us.com website (under OEM-products-fuel injectors-english) they show 6 different fuel delivery rates for the KN4 style, which is what we have, at two different fuel pressures.

Keihin Drawing#.........KN flow%....Max Flow.......Pressure

D30NA-AY4-0200-------25%-------=13.99lbs/hr @ 42.7psi

----------------------------------------=15.27lbs/hr @ 49.8psi

D30NA-AY4-0300-------STD--------=18.58lbs/hr @ 42.7psi

-----------------------------------------=20.28lbs/hr @ 49.8psi

D30NA-AN1-0101------+30%-------=24.17lbs/hr @ 42.7psi

-----------------------------------------=26.36lbs/hr @ 49.8psi

D30NA-AN1-0200------+60%-------=29.71lbs/hr @ 42.7psi

-----------------------------------------=32.37lbs/hr @ 49.8psi

D30NA-AY4-0400------+90%--------=35.26lbs/hr @ 42.7psi

------------------------------------------=38.45lbs/hr @ 49.8psi

Reference--------------+156%-------=47.32lbs/hr @ 42.7psi

The tricky part was no one knew what they were used in. They can tell you the Honda part number but not the keihin number and only if you know which car. By chance I stumbled across part of the puzzle while searching ebay. An individual was selling injectors for a 2000-2003 Honda S2000 car and lo and behold they match ours. So I then searched the web for S2000 forums and found http://forums.s2ki.com/forums, After doing a search on injectors I found out the ones in the S2000 flow 360-380cc/ 38lb per hour depending on who you ask and fuel pressure used at time of test.

After some searching for phone numbers I managed to get in touch with Paul Rodgers of Keihin USA. He was able to answer some of the questions I had regarding the KN4 injector.

First off he said the letters and numbers on the injectors don't signify specific models or flow rates but rather manufacturing date and batch codes. Therefore all the speculating I did regarding the ABS-E vs. B that are marked on the injectors is out the window. He said there is no way he knows of to differentiate between the different flow rates by looking at the injector. Removing an injector from a specific application or getting the number off the parts bag with the Honda label are the only ways aside from having it tested of knowing what the flow rate is.

I asked him about the chart on the Keihin-us.com site that showed different flow rates and he said those are the standard sizes offered by his company but that a customer like Honda can call up and have the injectors made for a specific flow rate. This means our injectors may or may not be one of the standard flow rates listed. Another aspect about the chart he clarified was the area under the Q=mm3/st. It has to do with the dynamic flow rate. How much fuel is flowed at 2 milliseconds, 6 milliseconds ect.

He also mentioned that the spray patterns would be the same no matter the flow rate for that style injector and that variation in the flow rates between injectors of the same size would be no greater than 1-2%.

That's about all I was able to get out of him that didn't fall under proprietary information.

So looking at the keihin chart it appears we have the standard or something close to it and the S2000 has the +90% model or something close to that. They are the same physical dimensions and impedance just different flow rates. Next quest will be to find out what applications the others were used on in case the PCIII won't compensate for the increased flow at low rpm or to fine tune the system with a lower flow rate which might be the case in a plain Hahn system. Today I talked with RC engineering (rceng.com) and managed to find out the new Civic SI has 310cc/30lb per hour injectors.

This gives us a number of choices.

Because the S2000 guys want more power/fuel too they go for after market injectors at $90.00 a pop. This means they have some perfectly good injectors sitting on their shelves collecting dust which they might part with. Elixxer posted an ad on the S2K forum and scored four for $100.00. You can do like I did and search ebay every few days for Honda injectors until some go up for auction, I got mine for $50.00 for a set of 4 new in bags, or you can stroll down to the Honda auto dealer and ask for the 2000-2003 injector for the Civic SI, or if you're power hungry the S2000, at $120.00 each.

I will send an XX injector off to have it tested to verify the size and will post the data when it arrives.

The fuel pressure changes after the '00 model and so there is a different part number for the '01-'03 models..

'99-'00 has a fuel pressure of 43 psi

'01-'03 has a fuel pressure of 50 psi

The part numbers for all the stock XX injectors are the same irregardless of year.

The Suzuki Hayabusa uses the same style injector but with a possibly higher flow rate. When they post the rate on another forum I'll post here.

Kind of long winded I know but I hope this helps.

Forrest

[XX4me]

It probably won't help you "sucker types" it's just a nifty bit of knowledge if you do venture toward the dark side.

[XX4me]

Pictures are always good.

CBR1100XX on the left

Honda S2000 on the right.

[XX4me]

Pictures are always good.

CBR1100XX on the left

Honda S2000 on the right.

[MiDNiTXX]

elixxer, did you confirm that the PC can handle the flow difference?

[kg4fku]

so is there a car that runs the stock bird injector or is the civic the closest one?

[XX4me]

I think the Civic is the closest one but there isn't any way to find out other than looking at injectors from various models since Honda car, Honda bike and Keihin part numbers are all different.

eliXXir (Dean) figured out that the busa also uses the same style injector as the XX just the next size up.

Check out this thread

http://pub31.ezboard.com/fazbiketechfrm9.s...picID=334.topic

[ralfybebedosekys]

Is there anyway to hook up a PCIII to a 1999 Bird, which normally only takes a PCII???

If so, then the larger capacity injectors could be used successfully on a 1999 Bird, yes?

Thanks for any help on this.

[XX4me]

?

According to Dynojet I can hook up a PCII to my 2002 for ignition retard purposes by just plugging it in. Might call them and see.

[ralfybebedosekys]

DynoJet emailed me months ago saying they knew of no way to convert a 1999 Bird for a PCIII.

I am hoping that someone at this site might have found a way to do it.

Thanks anyway though.

[MiDNiTXX]

elixxer, did you confirm that the PC can handle the flow difference?

I have no doubt that a PC-III can, a PC-II probably cannot however.

Remember, my case is a little different as I am installing a ECU replacement to mine so I don't use a PC.

Hmm, then I might be SOL. I have a PCII already and my budget is pretty much spent. I guess I could test it when I get the turbo tuned...but that will probably cost me an extra $300 to verify. We shall see...

So the busa injector is the next step up from ours? So a PCII could probably handle that small of an increase?

[XX4me]

If you read Gary Evans' posts about larger injectors the key isn't just the PC adjustments it's also the fuel pressure. If the pressure is lower at idle then you don't need as much electronic adjustment.

In your case I wouldn't worry about it just yet it's something you can easily add later when we get the bugs sorted out. And like you said maybe you could go one or even two sizes bigger with ease.

[MiDNiTXX]

Yes, in my case I don't "need" the bigger injectors, but I would like a comfort zone in that 220hp limit. Of course I would like to get it all done at one tuning sessions too, so thats why I'm following this closely so I can do everything just once

[XX4me]

Something I'm going to check on tomorrow is that there is indeed a difference in part numbers between the '99 pressure regulator and after '99.

Looking at the manual I noticed there is a different pressure rating for '99 compared to the other years. Good thing is it's lower.

This may mean we can install the regulator from a '99 which operates at 43 psi instead of 50psi. That's a 14% decrease in pressure which may be enough to fall in the range of adjustment for the PCII and certainly will help even the PCIII.

Partsfish sells the regulators for around $36.00.

[XX4me]

?

According to Dynojet I can hook up a PCII to my 2002 for ignition retard purposes by just plugging it in. Might call them and see.

HUH? You sure you checked with someone who spoke English?

I haven't checked the connectors......it's possible that the connects are teh same and that the PCII will work on the '02....just won't mod all the inputs. PCIII shouldn't work on the '99 system because all the inputs aren't there......whether it hooks up or not. I'd love to have the PCIII for mine.....just to use the accelerator pump.

Anyway.........you'd need the system off an '02 to be able to use the PCIII as far as I know. It would plug into an earlier bike......just have to supply a fake input for the lambda, I think it is.

Right Joe,

What they told me was the PCII will plug right inline with the PCIII and I should zero out all the values except the ignition retard. That way it wouldn't double dip into fuel. I'll let you know in about a week if it works or not.

ralfybebedosekys,

Elton Fish at EFR racing has a harness to do just that, BUT....... He does the work won't sell the parts.

[XX4me]

I think I came up with that number using the calculator on the RCeng.com site based on assumed flow rate and duty cycle.

[XX4me]

Checked with Honda today about the fuel pressure regulator.

Dean, you were absolutely right the 99-00 models use the 43lb regulator and the 01-03 and possibly 04 use the 50lb regulator.

I also checked on injectors and all years use the same one.

This means I can drop my low rpm off boost fuel pressure from 50lbs down to 43lbs and not have to remove as much fuel with the PCIII.

Cool.

[XX4me]

Good point.

The change probaly had to do with some sort of fucking mandate from the EPA.

[XX4me]

After some searching for phone numbers I managed to get in touch with Paul Rodgers of Keihin USA. He was able to answer some of the questions I had regarding the KN4 injector.

First off he said the letters and numbers on the injectors don't signify specific models or flow rates but rather manufacturing date and batch codes. Therefore all the speculating I did regarding the ABS-E vs. B is out the window. He said there is no way he knows of to differentiate between the different flow rates by looking at the injector. Removing an injector from a specific application or getting the number off the parts bag with the Honda label are the only ways aside from having it tested of knowing what the flow rate is.

I asked him about the chart on the Keihin US site that showed different flow rates and he said those are the standard sizes offered by his company but that a customer like Honda can call up and have the injectors made for a specific flow rate. This means our injectors may or may not be one of the standard flow rates listed. Another aspect about the chart he clarified was the area under the Q=mm3/st. It has to do with the dynamic flow rate. How much fuel is flowed at 2 milliseconds, 6 milliseconds ect.

He also mentioned that the spray patterns would be the same no matter the flow rate for that style injector and that variation in the flow rates between injectors of the same size would be no greater than 1-2%.

That's about all I was able to get out of him that didn't fall under proprietary information.

Hope it helps.

[demon]

Question for you fuel gurus. Could I install a fuel regulator off of a 2001 or later on my 99 to increase fuel flow without a power commander or would this give too much fuel at idle? I am currently running an AKRA 4-2-1 exhaust and no PC. The bike runs fine but a little more fuel would be nice. Just wondering if this would work cheap or if a PC would be a lot better for the money.

[demon]

That's kind of what I was thinking, but just wanted to make sure. The stock fuel reg would be fine for a PC, and that's probably the way I'm going to go. Log in some dyno time and do some tuning.