So in reality im spraying 20% more fuel into my engine when in open loop? I live in a city where I don't spend much time in closed loop. This might make sense why my stock 98 gets 19 mpg and my 97 gets 11 mpg. I think ill try putting the stock injectors back in for a while.

I still would like to know the exact cc's of all these injectors.

 

I thought people were claiming improved MPG's with the 703 injectors. Is that just on the highway, or when replacing trashed-out stock injectors?

DSD, are you running the stock intake? Better airflow might make a difference, too.

 

i have 2 XJ's... one is a 97 with a 3 inch lift, 31's and a surco rack. it's a auto, it has 021 injectors, and a 2.5" exhaust with a free flow cat, it gets 11 mpg.


my other XJ is a 98, bone stock with a 5-speed and it gets 19mpg.

i just can't see my lift etc and a auto trans making 8 mpg difference... it's driving me nuts.

and yeah i'd be willing to bet that the people seeing better fuel mileage with injector upgrades live in rural areas. when in open loop the computer program is being ran... so what ever value is there is what it's going to spray fuel duration wise. when in closed loop it will read off the o2 sensor and either add or subtract from that set value depending what the o2 sensor readings are.

i live in a city and it's all stop and go traffic. i think what i will try is to get a o2 sensor bung welded in as soon as i can get my hands on one and i'll install my wideband to get a idea of if i'm just running pig rich or if it really is my lift etc.

if it's my lift then i'm at a crossroads.... my 98 i bought crashed so i could do a 5 speed swap tp my 97. i won't have time to do the swap till summer so i fixed up the 98 and made it driveable. now i have to decide if i want to swap the trans and take the lift etc off my 97 or if i want to finish fixing up the 98 and make it a daily driver. i really don't want to have to maintain 2 vehicles and i really don't go off-road enough to justify having a jeep for off-road only.

 

Please tell me if I've understood correctly: In open loop, the controller just reads the TPS and the MAP sensor and sets the injector duration from a look-up table. In closed-loop (at highway speeds), it adjusts the injector duration to achieve the correct fuel ratio, which it reads from the O2 sensor.

In town, I just don't see the tires and rack making that much difference. Probably not the auto, either. That stuff makes a huge difference on the highway. Then again, an awful lot of the people getting 18+ MPG seem to do it with the AX-15 (myself included).

Questions:

1) So for city driving, you can fix the fuel ratio by getting one of those adjustable MAP sensor thingies, right?

2) Does the XJ engine controller use the values that it "learns" from closed-loop mode, and fill in the open-loop table with those values? If so, you may be able to fix this just by taking a nice road trip.

 

It doesn't need to be highway speeds to go into closed loop... its more of a engine load thing. And no the ecu wont adjust the preset values off what it sees while in closed loop.

The XJ must run rich to begin with. My 98 has a overhead console in it that is really accurate... when accelerating it would say I was getting between 5-7 mpg and if I let off just a little it would go to over mid 20's, while in closed loop in town around 50-60 mph I could get 30's.

 

Maybe that's why it responds so well to improved intakes. Makes me want to get one of those fuel ratio gauges for my dash...

 

An anti-fouling spark plug adapter from Autozone works for the narrow band. Will the wide band fit the same hole?

 

Those keep the o2 out of the exhaust stream. People usethat for the downstream o2 when they don't have a cat, it keeps the sensor out of the direct exhaust flow and keeps it from throwing a CEL.

 

We use them to mount sensors to exhaust pipes. Bore it a bit, and cut the male threads off.

 

I ordered a bung... it should be here by the end of the week. If I get it before friday ill have it installed friday and test friday night.

 

Any word how they would work on a 99 grand cherokee

 

Exactly what I did to replace my downstream 02. Just made up a pipe, popped a hole in her, cut down the spark plug fowler and welded it in with a crappy o2. When it cooled I pulled the crappy o2 and installed the good one.

Easy peasy, just dont breath the smoke when you weld it.

 

Yeah, the zinc fumes are not good for you.

To jeepcherokee99: They should work if it has a 4.0 with USCAR connectors.

 

I got my bung yesterday but was busy at work todays I didn't ha e time to install it. I did do a lot more closed loop driving this week and the mileage seems to be so far better than the 703's.

 

A couple notes.
-I put 703s in and didn't notice any difference whatsoever.
-A lot of people are saying their mileage used to be better years ago. Years ago our gas wasn't full of ethanol. Anyone that has driven a flex-fuel vehicle can tell you how much worse mileage gets on ethanol.

There are several options here that might work for the people that are really **** about getting the most out of an injector.
http://www.racetronix.biz/items.asp?...atus=0&Tp=&Bc=