I just got my injectors back from WitchHunter. They cleaned them and flow tested them. They are standard 89-91 460cc injectors. Three of them tested at 460cc, and one of them was 458cc. The resistance was .1 higher than the rest, static flow was near the same, pulsed flow was acceptable but a little lower than the rest. The cc/min was tested at 43.5psi.

My question is: should I be worried if the overall cc/min is 2cc lower than the rest? This is the first time I've ever put cleaned/flowed injectors into a car I care about.

--Micah

 

I'm thinking no - on a stock tune, your injectors probably won't be maxing out duty cycle, and if everything's working normally, your o2 sensor will compensate for any rich/lean condition.

Think about it this way, your injector is off by less than 1/4 of 1%. Or 0.25%, which is a really insignificant difference.

Truthfully, I suspect that if you were to buy 4 brand new perfect 460cc injectors, they'd be further apart than yours are.

 

Mine were off a bit but they're fine. Here's my results...

Approximate pounds-per-hour flow :
1. 46.18
2. 46.18
3. 46.70
4. 47.21

So, if I'm converting right, mine are flowing 485cc to 496cc. Hmm, after converting it to cc it seems a bit much.

 

You should be pleased. Those are closer than most of them come back after cleaning.

 

Oh... Good deal. Thanks for the re-assurance. I honestly never really studied the results I got back from any of the places I've sent them to before. And... why would I.. I was putting them into a minivan.. or a taurus... or a cherokee.. But, for my 7... I had my spectacles out.

Thanks again.. Quite the learning experience.

 

I would be more worries about the fact that they should've provided ~460cc/min at 36psi. At 43.5psi they should flow ~500cc/min.

That only happens during low-load cruising when the ECU goes into closed-loop control. The rest of the time the O2 sensor does nothing..

 

Which for normal people would be at least 90% of the time. I'm also unfamiliar with the rx7 computer, but does it setup a fuel map using the o2 sensor once it reaches that point for injector instructions in open loop? I know the '94 Mustang does.

 

Should I REALLY be worried about that? Perhaps thats the mazda spec for testing the injectors? on their form, I didn't put what car it was from originally.... so they called me when they got them to ask. I told them. And they said "Thanks, we need to know what car it is for so we know what pressure to test it at."

I dunno... first time dealing with witchhunter.. but they seemed extremely professional.

 

If you'd ever watched a A/F meter on an FC you'd know that it is far less that 90% of the time.

 

For comparison's sake, 2 of mine flowed at 47.21 and the other 2 at 47.22 lb/hr. I had mine done at cruzin performance.

 

That's true - I tend to pay more attention to the road when I drive.

Besides, I don't drive like most people.

And noone knows about the fuel map? Like I said before - once the Mustang's computer goes into closed loop, it rewrites the map for fuel in open loop too. I had to replace the headgasket in one so I went ahead and ported the heads. But because the check engine light was on and it wouldn't go into closed loop, that thing was a DOG to drive. A couple of days later, once the light was reset, it feels about 15hp greater across the whole band, from the moment you turn the car on.

 

Download the Fuel and Emissions section at this site: http://wombat.sevarg.net/RX7/RX-7_Training_Manuals/

And the other items too if you want.

 

You mean you drive like a grandma? Closed-loop only occurs during constant-speed, light-load driving, so it would be impossible to spend 90% of your during time in closed-loop unless you were doing a very long freeway trip.

Self-learning is a common feature in EFI systems from about the early 90's, but our systems are a little too old for that. The fuel map isn't so much rewritten as slightly tweaked. It's used to correct for changes caused by the condition of the engine changing over time, but it can also compensate for mild mods.

 

*Sigh* No, I drive with my foot to the floor most of the time, which would be the reason I was saying it wouldn't do me any good to watch the Air/Fuel Gauge, not to mention that I don't have one. At the same time, most people, at least most people I've seen don't drive like I do - i.e. max acceleration at redlights - cornering at 35-45 mph, and most people commute more than 8 city miles to go to work.
I apologize that my 90% number was high enough that you felt the need to correct it. But for what I would consider an average commute, 30 miles to work, 5 city, 25 hwy, and shifting at around 3-3,500k, I would consider you're spending quite a bit of time in closed loop. I'll restrain myself from providing a percentage, since God knows someone will take issue with it.
So once again, once it enters closed loop mode the first time, the fuel map for open loop will also be changed to more closely reflect the performance of the vehicle, which I think was my point in the first place. Once again, I apologize for my use of the term "rewritten", I was using that as a blanket term for "changing all the numbers on the fuel map". One day I guess I'll have to learn the difference between changing and tweaking, because I always thought "tweaking" implied some sort of change. I guess I was wrong again.

 

Awesome find, thanks! And how much do I love that they listed "Sporty Rotary Sound" as a performance category?

 

Those TRAINING manuals were first posted by the NZCONVERTIBLE and the Hosting of the manuals was by a couple of other people, ALL of whom we can say THANK YOU to.

There are some tidbits in them that helped me understand things I wasn't aware of. Like how the fuel is delivered during the START CYCLE. That led me to make an electrical switching device to eliminate flooding problems on one of my cars during HOT starting. The switch cuts down the ms the fuel is delivered when the key is HELD to START.

 

Well.. I think we can all agree that my injectors are fine.

 

I interpreted your post to mean you thought your driving style (which you hadn't described) was responsible for spending a high proportion of time in closed loop. My misunderstanding.

If you spent that much of your commute on the highway in light traffic (i.e. so you can drive at a constant speed) then yes you could spend quite a bit of time in closed loop, but it still won't be anywhere near 90%.

Some people reading this might not know much about closed loop, and might assume your number was correct. If you post info that's wrong in a technical section you can expect to be corrected. There's no point getting all pissy about it.

I wasn't saying you were wrong, just that our ECU's don't do that.

I guess I need to explain it clearer. The fuel maps are actually not changed at all. The original maps remain unchanged because they're a fixed part of the firmware. Instead a correction factor is applied just like what happens to compensate for air temp and coolant temp changes. The correction is smaller and changes slowly but the concept is the same. On some ECU's this data is lost when the battery is disconnected, which can make some modified cars run a less than perfect for a short while afterwards as the changes are re-learnt.

I guess you should. I thought you'd realize that a "tweak" implies a very small change. See above getting pissy...