How much do 720cc injectors affect emissions?
 

Basically how much richer will the car run with 720cc secondaries if everything else is stock?

I'm rebuilding my TurboII right now, and one of my secondary injectors is bad. I'm just going to replace both secondaries with 720s now, as I'm going to do it eventually when I start upgrading anyway. The thing is, I have to pass smog first.

Will I be at risk of failing the smog test with the bigger injectors if all the other smog equipment is intact and working?

You'll fail emissions unless you have something (ie. S-AFC) to tune them down. The car will run quite rich past 3800 RPM.

ASE Master/LS1 This is how the feed back system works on all OBD1 & OBD2 cars.Once the ex is hot and the O2 starts working the PCM will know if the fuel mix is to rich or lean and will ajust under normal cruse (stedy speed). If you scane the PCM it will tell that the fuel trim is off but I,m able to adjust if some one had put in bigger nozzles.Once you step in to it the PCM changes to defert program (WOT)stops useing the feed back , PCM goes to aset values. If these nozzles are bigger the PCM doesn't know this and those will run much richer then spic. Also on cold start up will run much richer until it goes into (closed loop) feed back. If you have a OBD2 it most likly will set a code , the lite may not come on but when you go for your inspiction they are going to reteve any and all data thoes you fail.

RX-7s are not OBD cars. The car will run rich if larger injectors are installed, plain and simple. Please do not post misinformation.

So if it's not then the O2 is just there for the ride ?

You don't seem to understand how the stock ECU works.

The secondary injectors don't fire until two conditions are met:

1. The engine is above 3800 RPM
2. Load on the engine requires more fuel

Therefore, under cruising conditions, only the primaries are used. This is also when closed loop operation occurs, and is the ONLY time the stock ECU pays attention to the O2 sensors.

If the original poster puts 720CC injectors into is secondaries, the car will run pretty rich under LOAD, most likely causing him to fail the "accelleration" or "load" section of the e-test. Wile the secondary injectors DO NOT effect cruising, he has already failed the test.

Just read what I wrote.

Sounds like the begining of a good relationship,lets get to know each other, sarav@quik.com
https://www.rx7club.com/attachment.p...postid=2355383

What you wrote is correct, but it doesn't have any bearing on RX-7s since they are NOT OBD compliant. It simply doesn't apply to the original poster's question.

Nice RX-4. I have always wanted to get my hands on one, or a Cosmo.

I have 720cc 3rd gen injectors on my car. I passed fine with no S-AFC or aftermarket fuel controller. Not only this, but I also had no air pump, a high flow cat, and apexi dual n1's.


-marshall

3rd gens have 550cc primaries, 850cc secondaries. And they are side feed. They won't even fit into FCs without serious modification of the fuel rails and intake plenum...

Thank you ,at the time this was all there was on the lot I would have also taken a cosmo. Knowing how things work is all way a bearing. To offen I see things come in to my shop where some one has then this to get that and doing so off set that. My rule is ,I won't feel bad if the person is well infromed thoes can do any thing they what.

Hmm ok. I know i have 720cc secondaries, the owner before me told me they came out of a 3rd gen. I'll look for the reciept and see what kind they really are now, thanks for that info Aaron.

Hmm....
Both of you guys are correct....
During an emission test, they rev it up in gear, under load to whatever the specified speed is. It will definatly not be in closed loop then, I beleive they then hold it at a specific rpm for a little while, it may jump into closed loop then.
The other thing- I'm not 100% sure, can't remember off the top of my head, but I *beleive* that closed loop operation actually ceases once rpms exceed 3800, at which point the secondaries come on.
The car, theoretically should run about 15% richer once the secondaries come on (injectors are about 30% bigger, and they are 2 of 4 (50%)
Whether that will be enough to fail an etest probably depends on how the condition of the car.
I also don't know how much weight that acceleration aspect carries in the overall score of the etest. Maybe someone with more info can fill me in.

gambone your 51?? And you know how to use a computer. Very impressive. My father is 48 and dosent know how to even turn it on.
Props man.

I live in Salem Or , no DEQ yet , Portland Or does have and from time to time I get one in and I'm the drive man at my shop. I have a copy of the rules and they make my head spin so I just put them on the dyno and find what's going on and turn it until the readings come into DEQ spic.or what ever it takes.Some of the owners think they are being ripped off , in there minds it is running just fine. One thing , if I do this what will be the chane reaction , My RX4 don't stand behind it your eyes or yourr noies will burn

I don't know the exact procedure for the emissions tests, but would it not stand to reason that they are driving it gingerly. eg. To accelerate they're probably shifting at ~2700 or something. With this in mind wouldn't the primaries be the only injectors that are used in an E-test?

Bambam7 is correct that the car is in open loop above 3800rpm.

The simple answer is you shouldn't run larger injectors without some way to tune them properly. Otherwise you run very rich, use lots of gas for no reason, lose power and probably fail emissions. With a properly tuned fuel controller or standalone, all of those problems disappear.

Kaneto, what do you mean by one of your secondaries is bad? Most of the time they can be reconditioned, and getting all four done would still be considerably cheaper than two new injectors and a fuel controller.

In theory. ;) But then, they could also be like a certian-garage-in-London (who will not be named) that let my car sit for 45 minutes, drove it onto the dyno while it was still in cold start, then promptly failed me. :)

I know they can be reconditioned. It's not expensive, but it's still something I would have avoided if I could. Basically I'm dropping in 720s and a microtech about a week after I pass emissions, and I was wondering if I could just go ahead and get by on the 720s and not spend the money reconditioning the old ones.

So my options are pretty much recondition the old injector, or go ahead and install the 720cc injectors and microtech before and and tune the secondaries a bit lean.... and hope they don't see the aftermarket ecu?

i have never heard (nor asked) of aftermarket computers being illegal in any cars. if you pass, you pass i would think. OBDII is different, but all our cars are pre-96, so that's another story. i'd like all the info on OBDI vs II (and above), but wouldn't know where to find it. also, our cars not having OBD at all (however you meant that, Aaron; i hate to misquote) is new to me. is there another name for the computer?

California emissions include the visual inspection. A microtech isn't CARB approved, so if the inspector sees it, he can fail the car.

As far as I can tell, OBD-I was required in 1988 in California by CARB, and OBD-II was phased in in 1994 in California and required by 1996 nationally. According to a site I found, OBD-I "was relatively simple and only monitored the oxygen sensor, EGR system, fuel delivery system and engine control module." OBD-II is basically more comprehensive and starndardized. I found most of that info at http://members.aol.com/carleyware/library/us796obd.htm if you're interested. The EPA site is really confusing and only has stuff about OBD-II.

I'm back ASE/L1 , X Mazda tech , 76 RX4 owner since 78.Reconditioned nozzles and what they realy are, frist they con not be taken apart , they are tested , cleaned , checked for flow and given a number value. it then goes into a bin. Some one needs a set of 4 or 6 what ever. They go to the bin and get all with the same value number , this # relates to the flow so you are getting a mached set. My be a little higher or a little low then spic , but it will be in the ball park. Now think about the ones you are going to send. Mr. 89Turbo944 you are sharp, yes I'm 51. Mr. Kanete your post is turnning out to be one big cat fight, stay with it , lot af good stuff is comeing out.

It's illegal to make any modifications to any part of the emission control systems. I believe that is federal law. The ECU is a rather important part of the emission control systems, so technically it is illegal to change it.