stomperxj

Recently finished a swap into my 98 Cherokee.

05 LM7 - 140k
00 LS1 intake with stock LS1 0280155890 injectors
00 Camaro exhaust manifolds

I finally got through a full tank with no mechanical issues and it came out to 12.3mpg. Seems like it should be a lot more than that.

I had my tuner set the rear O2 sensors to no error reporting and I only have B1S2 hooked up along with B1S1 and B2S1. Would only having one rear O2 hooked up be causing a rich condition? B1S2 looks like it is functioning properly and B2S2 shows a flat line on the graph obviously because nothing is hooked up to it

Also on the way home from a 15 mile trip today I did a couple full throttle passes up to about 60mph and it seems like the top 25% of the throttle pedal doesn't do much. I checked my throttle travel and its opening to 99.6% according to Torque.

So I realize I am driving a lifted brick of a vehicle but my fuel economy should be better according to others that have done this Cherokee swap. Maybe I was expecting too much but it seems like it should be better.

This is a short trip I did recently. I realize this was a cold start and lots of warm up time but 5.9 seems horrible. The 16mpg that Torque is reporting is way off for the average. The tank previous to this was about 11mpg.

Start-warm up for 10-12 minutes
4 mile round trip-stop and go, nothing over 35mph
Shut off





Everything seems to be somewhat normal. Anyone have any ideas why I would get 5.9 mpg even on a short trip? It smells rich when I go out after warm up too.

I have done tons of reading and I don't know what to check next. I am going to pull a couple plugs from each bank later tonight to see how they look.

Also, it has new knock sensors and knock sensor harness, new cam sensor, new temp sensor, all 3 O2s are new Bosch units.

Anyone have any ideas?

jeremytap

Only having 1 o2 will cause problems. Even just hooking up 1 front one would have been better than the back one.

stomperxj

So do you think I should hook up B2S2 in the pipe next to B1S2 and run all 4?

TomM

iTrader: (56)

So I'm confused. You said your tuner turned off the rear 02's, yet you said B1S2 is reporting. Unless I am missing something, that is a rear 02 on the drivers side.....

The front 02's are as follows..

B1S1 is drivers side front
B2S1 is passenger side front

The rear 02's are as follows...

B1S2 is drivers side rear
B2S2 is passenger side rear

So what do you have, and what is connected?

T,

ls1nova71

iTrader: (4)

The rear O2's dont have anything to do with fueling, they just tell the PCM if the cats are working.

stomperxj

I told my tuner I wanted to run 1 downstream O2 sensor because I thought they were separate. Tuner turned off "error reporting" for both rear O2s because he said he could not do only 1. He said the rear would still help adjust fuel curves but not throw a CEL.

This is the current setup:

B1S1 is in the drivers side down pipe
B2S1 is in the pass side down pipe
B1S2 is in the pipe post cat
B2S2 is not connected.

stomperxj

So if only 1 is working what does the computer do to compensate?

I know absolutely nothing about tuning or how the computer adjusts things...

gofastwclass

iTrader: (2)

You only need bank 1 sensor 1 (B1S1) and bank 2 sensor 1 (B2S1) for fueling. Like ls1nova71 said, anything else is for emissions.

In theory, nothing will change. I've never tried it though, I always remove both. The rear O2's confirm the cats are working and set a code if they aren't.


Incorrect injector data in the tune will skew everything as will incorrect MAF information. Depending on where your MAF is placed and if the engine was calibrated for the new location, you may have a rich condition even with proper injector data.

Changing the intake path and exhaust path (headers, duals, etc) will also change the VE which will also skew your fueling.

You changed the intake manifold, exhaust manifolds, intake air path and potentially MAF location. To get the proper power and economy requires a full driving tune, not a simple "turn off VATS, rear O2's and other emissions junk."

rpturbo

iTrader: (47)

If thats what your getting for mpg's, you need a new tuner, because that tune, is a piece of ****.

stomperxj

Thanks for the great info gofast. All of those items are different from stock I'm sure. I never knew I needed a tune on top of the one I got. Looks like I need to call the one guy in my area that does tunes. I think he charges $300 for a drive tune.

Haha I guess you get what you pay for. I paid $75. The guy that tuned this never mentioned I should get drive tune either. He does tons of these... you would think he would mention that at some point.

Thanks for the info guys. I've been for awhile on this.

LilJayV10

iTrader: (39)

why only one 02?

stomperxj

I have 3 O2 sensors, 2 upstream, 1 downstream

rpturbo

iTrader: (47)

I am sorry I didn't give you any real feedback. It pisses me off that people do that. I have been there. Honestly, I would be afraid of that tune though. Don't risk the engine, because of a **** tune. He either, didn't put in the correct injector data, didn't tune the VE, and also probably raped the maf table. He probably only adjusted the PE.

If you want to avoid this in the future, and want to learn to tune yourself, like I did, pm me, and I can help point you in the right direction. I am in NO way a tuner, but I did tune my own junk, and it gets ~20 mixed driving, and ~24 on the highway, and it's far from done.

stomperxj

No worries. I liked your comment and agreed with it

From what he told me he left everything OEM except for a little more timing and turned error reporting off for the rear O2s and deleted EVAP. I sent him the numbers off of my LS1 injectors but have no way of knowing if he changed it for those and the LS1 intake or not.

I sincerely appreciate the offer for help. What hardware is needed to do my own tunes? Is there way to do it on a laptop or is HP Tuners the only option?

gofastwclass

iTrader: (2)

I use HP Tuners and I run it from my laptop. I've been using the software since 2009 and it's absolutely amazing. I strongly suggest getting a wideband O2 sensor with the tuning software so you can tell exactly what your air / fuel ratio is. I also suggest reading everything you can get your hands on before you start.

The problem with HP tuners (or any tuning software) is the learning curve is fairly steep. If you aren't a technical minded person, forget it. You will find yourself hating the process and you will feel you wasted your money. If you are interested, check them out at http://www.hptuners.com/. You can even download a demo of the software and see what it's about plus read and post in their forum to understand what you are buying without spending a dime.

There is another brand but last I checked, their software is a bit more expensive and in my opinion, a bit less friendly for someone starting out. Think Chevy vs. ford vs. dodge. None are bad, just different ways to get to the same destination.

stomperxj

Thanks for the tips. I really appreciate it. I have briefly looked at HP before but not sure I can justify the cost just for 1 rig right now. I do have an 81 Fairmont I plan on swapping at some point so I might pick it up at a later date.

I have a lot of reading to do. I know nothing as far as tuning goes...

gofastwclass

iTrader: (2)

You're welcome. Between the steep learning curve and the initial purchase price, it is absolutely not cost effective for a single vehicle use unless you plan on making lots of changes in the future.

2ToeRacing

iTrader: (5)

I am pretty much going through the same thing. I just bought a 01 camaro SS that the guy installed SLP headers n Y pipe and borla out back. He used a Diablo sport hand held tuner and my gas mileage is **** to say the least. I get about 200 miles a tank,I do get on it some but not enough. Its like a fukin toilet flushing my gas.

I'll be watching this post to see what happens,good luck learning the tuner.

rpturbo

iTrader: (47)

Most tuners that do a "part time" tune gig, try or should I say, tend to get away with just adjusting the MAF at best, or changing the PE value or some combination of both.

I knew 3 guys who all had a "tune" done, and myself. When I pulled all of their tunes when I first started learning, I had literally spent less than a week reading and learning, and had 1 of their tunes better than the "tuner" who supposedly, had been tuning for almost 20 years. All of the tunes had the same basic look to them. VE wasn't touched, maf was raped, timing was "added" and PE was rich, in all cases, the idle wasn't touched, I guess that wasn't part of the "tune" for $400+.

stomperxj

This was a budget tune from a gentleman that has a popular site with tons of pinout info and general info on Gen3 stuff. I'm a little disappointed nothing was mentioned about getting this stuff fixed after the swap. I suppose he wouldn't sell a lot of tunes if he told everyone they had to get another one after it was running.

And just so I can start learning:

PE - Power Enrichment table? What does this do?
VE - Volumetric Efficiency? Does this have to do with intake tube sizes and filter box pre throttle body?

Thanks again for the replies. Sincerely appreciated.