I just got a call from witch hunter injector services about the 1300cc injectors I sent off to him for cleaning and flow testing.

he told me that one of them at 100% duty cycle is flowing 1700ccs, and the other is flowing 1520ccs

That is a HUGE difference at 100% duty cycle.

However he told me at 50% duty cycle there is only around a 5% difference between the flow rates.

Either way, that is still WAY over the 1300cc mark, I didn't even think it was possible to hit those ammounts with a stock size 850cc injector.

Anyone else have a similar experience with this? I'm almost worried to put these into my car, as I have no idea what they will really flow. The way they flow on paper, I should set them as 1500cc injectors instead of 1300cc injectors in the PFC.

Anybody else have a problem with something like this from RC bored out injectors?

 

Based on the fact that they aren't even (1700/1520) I would send them back to RC Engineering for an exchange/refund. Did you buy the inj's directly from RC?

 

I bought them from another member who had them modified by RC. But I mean that is a horrible horrible difference, and I didn't even realize it was possible to double the stock flow numbers and have them work.

 

Since you got them used, I wonder if they were really modified by RC. All the 1200/1300 modified injectors I've seen from RC come with a flow test sheet. The numbers are usually close to the 1200 or 1300 cc flow.

Jack

 

I can ask the member who sold them to me, but that is just insane and honestly I don't know any other company out there who will modify injectors besides RC. Most cleaning and flow testing places will not modify injectors.

 

There have been other places floating around who modify injectors. I would get a refund from the forum member. Seems like that person sold you worthless injectors.

 

I had a set of "1300's" that I was told was modded by RC, but I got them secondhand so I couldnt know for sure. They were engraved just like RC does, and said 1300.

Anyway they both flowed right at 1500cc. I used them 1.5 years and never had an issue.

 

just put the higher flowing injector in the rear.

 

I like the way you think

 

Interesting way to do things....I'm going to wait until the guy from Witch Hunter cleans them and sends them back. He was going to do a bit more testing for me @ 60% duty cycle and 85% and email me the flow results. He was hoping after cleaning and leak down testing that they would be a little bit closer at 85% duty cycle, since that is the maximum I'll end up pushing them.

Thanks for the help / insight guys, depending on how far apart they are I'll probably just do what Guitarjunkie mentioned.

 

You should have sent them to RC. Are they disc style or ball/speed? With the ball/speed type ive had many trouble in the past with them not flowing anywhere near equally. Also, you said they flow those numbers at 100% duty (you should not look at what they do at 100% because you should not run them that high), what duty were they rate at 1300cc's? most injector rating is under 90% duty because you do not want them running too high or they will fail. this is why most injector readouts when purchased new will say " 1300cc @ 87% duty." When they flow over their rating they may output more just by the fact that they are staying open longer.

 

Guys these WERE done by RC Engineering from what I know. The guy who sold them to me stated that they were modified by RC Engineering.

These were flow tested at 100% duty cycle at the numbers I posted above, the guy from witch hunter told me that at lower duty cycles they were a bit less and a lot closer in flow ratings (only 5% difference at 50% duty cycle)

 

as i said 1 up ^, he should have told you what they flow at 85-87% duty. This % is what is most aimiable to run with your setup. if they are more than 5% apart at 85%, I personally would not chance it. But it is somewhat normal to see higher cc's at higher duty cycles. Too high of a difference is what may cause some problems. I say "may" it may not also.

 

The only problem I can see it causing is making the car run too rich.

I'm probably going to try these out, and if they don't work out for me (cause rich spots) I'll probably just send off my current 850cc injectors to RC and have them modified to flow 1200ccs, sicne most people say they are a lot more accurate at that flow rating.

I'm also going to email the guy from witch hunter and see what he says about how far off they were at 85%

 

FYI, injectors are rated at flow rate with 100% duty cycle at around 42psi of fuel pressure (can't remember the exact PSI, but it's around there). So, a stock 550cc injector will flow 550cc at 100% duty cycle at ~42psi fuel pressure.

So, Witchhunter is doing the right thing in his testing. Boring out injectors is just a tricky business, so who knows the whole story with what's up with those injectors. Personally, I would be a bit hesitant to run them. IMHO, when you want to make big power, you really have to do the injector RIGHT. Brand new injectors - not used, not bored out. That's just me, though. Injectors are so finely calibrated that I could see small problems add up to bigger problems.

Dale

 

We have had no success in our attempts to get higher flow rates from injectors by modifing
them. They get really sloppy at low duty cycle rates.(Rich) Spray patterns are usually disrupted by the attempted mod. You are better off getting an injector that comes in the flow rate you want, unmodified.

Joe Geiman
Gasoline Alley fuel Injection
Speedway, IN

www.lindertech.com

 

For you guys ripping on bored-out injectors.....hundreds of FD owners have used them over the course of several years with very few reported problems.

It's nice to say just go with bigger unmodified injectors, but the ONLY solution that leaves is the big Bosch 1600cc injectors. This requires removing emissions, installing an aftermarket fuel rail, and and aftermarket pressure regulator. That solution simply doesn't work for a lot of us.

FWIW, my RC-bored injectors tested out at 1298cc and 1304cc, IIRC.

 

Must be nice lol.....


I sure hope that when I get mine back from witch hunter that they are a little bit closer, as the guy I talked to was hopeful that they would get a bit closer after cleaning and leak testing.

 

Just to update this situation......


It looks like after cleaning and re-testing they are a little bit closer @ 100% duty cycle.

One injector flows 1536 @ 100% and the other flows 1640 @ 100% duty cycle.

When they are at pulsed 2500rpms (not sure what duty cycle this is) they are a lot closer (179 and 185cc )

Overall even at 100% duty cycle there is only a 6.5% difference in flow, and with the mods i have this car will never see more than 85% duty cycle. I think I'm still going to run them, I feel much better about the numbers now that they were cleaned and re-tested, I guess they were a bit off on their numbers when I spoke with the guys from witch hunter over the phone.

Anyone still see a problem with doing this? Also, the tests were done at 43.5psi of fuel pressure, our stock system is only 40psi correct?

I think I'm just going to take guitarjunkie's advice and put the higher flowing injector on the rear housing.

 

I wouldn't run those injectors. The chances seem fairly good that your car won't run right and you'll need to replace them anyway. And at worst, you'll break your engine and end up spending a lot more money than the cost of a few injectors.

Send them to RC and see what they get when testing. I am curious to compare the measurements from RC and Witch Hunter.

Injectors are flow rated at 43.5 psi of pressure and 100% duty cycle (and various other standard conditions). Flow rates change by well known amounts at lower or higher pressures and duty cycles (there are simple formulas for both). That does not mean the injector is a different size, it just means you aren't running it under the standard test conditions.

I guess what I am saying is that you should enter the standard flow rating of the injector into your fuel management system. Don't try to adjust the value since you aren't running standard pressure, or lower max duty cycle, or whatever. You'd only be outwitting yourself at the expense of your apex seals. Enter the flow rating from the standard test conditions. There are a few exceptions to this rule, but if you have to ask, you shouldn't deviate.

-Max

 

LOL.....damn now I don't know what to do. It just sucks because this is basically $350 down the drain between buying the injectors and getting them tested

I think for now I'm just going to tune my car with the stock injectors, once I run those past the safe efficiency level I'll think about something else. I just wanted to start with the bigger size injectors so I don't have to re-tune again later on and I'm not limited by fuel. I have the RP fuel pump going in this week as well.

Maybe I'll just go 850's in the primary rail..... seems like a better alternative since I'm not willing to go to 1600cc injectors and buy a datalogit at this point.

 

The "standard" pressure which most all injectors are rated at is 43.5 psi (3 Bar) and at 100% duty cycle.

I am not a big fan of modified injectors, most are problematic.

Gordon
WitchHunter Performance

 

Going with 850's in the primary gets you 3400cc total flow, boring your 850's to 1300 and keeping stock 550's in the primary gets you 3700cc flow. Unless you really need that extra 300cc I am perfectly happy with 4x850.

While there are many people who had no problems with modified injectors it is impossible to argue that they are just as problem free as the stock injectors. If the chance of failure is even 1% higher in a modified injector that is too much for me as any failure will mean almost certain apex seal damage.

 

Well I was able to get my hands on a new set of 1200cc injectors, so I'm goign to give them a whirl since their test numbers came out ok.

I'll eventually upgrade my primary injectors to 850cc injectors as well so I'll have all the fuel I could possibly need.

 

if u wanna sell those other injectors cheap....let me know they r the same I have in my car...and an extra set wouldn't hurt. by the way I run 550 in promary and bored 1200 in secondary...and 15 lbs no problems ..and it was tuned rich so I can keep my apex seals