Is my exhaust system too restrictive for my 6.0L? :TECH ONLY:
10-27-2008, 07:50 PM
#22
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The last note I would like to add is that if you look at my AFR, it starts to richen as the RPM's climb. This is telling me that it's not getting enough air (and I know it's not the intake tubing itself). So is this a result of a poor camshaft or poor exhaust? I tuned the truck personally and I can tell you my power enrichment past 4K is perfectly LINEAR so there's no reason for it to start falling like that.
10-27-2008, 08:36 PM
#23
I don't feel that the exhaust is the problem, LT's, no cats, and 3" pipe should be good for your set up. As mentioned, I'd look towards something in the tuning to correct the rich a/f condition. Just curious, is there any advance ground into the cam?
10-27-2008, 09:26 PM
#24
Ok guys, regardless if some of you may not agree with my tune, the fact of the matter is the AFR never gets any richer than 12.5:1 AFR. This isn't going to be the reason the HP falls off so dramatically. Also my total spark advance is 28 degrees with premium fuel. In the end, we can argue 'til the cows come home but the fact of the matter is the AFR is perfect 13.1:1 all the way up until the power starts to drop off at 5300-5400RPM where is very slowly dips to 12.5:1 AFR. I don't think this is enough to warrant a 30 RWHP loss. The fact is, it doesn't matter how I'm getting the AFR there, it's there. Also, spark advance is spark advance, 28 degrees wrung out the most power out of this combo we could. If you want to call the tuning "flawed", that's fine. In the end, the AFR being good and the spark advance being spot on, what's causing the quick declination of HP? The AFR dipping towards the top is telling me it seems as though there's a restriction somewhere with inhaling or exhaling.
10-27-2008, 09:39 PM
#25
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Ok guys, regardless if some of you may not agree with my tune, the fact of the matter is the AFR never gets any richer than 12.5:1 AFR. This isn't going to be the reason the HP falls off so dramatically. Also my total spark advance is 28 degrees with premium fuel. In the end, we can argue 'til the cows come home but the fact of the matter is the AFR is perfect 13.1:1 all the way up until the power starts to drop off at 5300-5400RPM where is very slowly dips to 12.5:1 AFR. I don't think this is enough to warrant a 30 RWHP loss. The fact is, it doesn't matter how I'm getting the AFR there, it's there. Also, spark advance is spark advance, 28 degrees wrung out the most power out of this combo we could. If you want to call the tuning "flawed", that's fine. In the end, the AFR being good and the spark advance being spot on, what's causing the quick declination of HP? The AFR dipping towards the top is telling me it seems as though there's a restriction somewhere with inhaling or exhaling.
I'd like to see a log of the tune posted to see what cells you are in when it starts going rich...
10-27-2008, 10:57 PM
#27
Well, here's another log I did while doing a dyno pull (see attached) . I hit 95KPA and maintain that manifold pressure. I also was under the impression that when in PE, your computer automatically goes to 105KPA regardless what your real reading is and your PE miltiplier is based off that.
10-28-2008, 01:55 AM
#29
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Should tune to get the highest power, not tune to get the "so-called" best a/f ratio.
Hard to do on an intertia only dyno. On a loaded dyno hold the rpms and tune at varying rpms until best power is made in each rpm cell. Roadrunner helps immensely in this area.
You want more fuel at peak torque rpm, then lean it out at peak hp rpm.
It cant be coincidence that your fattening a/f ratio happens at the same rpm as your power dropoff.
If you suspect an exhaust issue, try an open header pass.(if thats easily done)
Goodluck man, I hope it all works out.
peace
Hog
Hard to do on an intertia only dyno. On a loaded dyno hold the rpms and tune at varying rpms until best power is made in each rpm cell. Roadrunner helps immensely in this area.
You want more fuel at peak torque rpm, then lean it out at peak hp rpm.
It cant be coincidence that your fattening a/f ratio happens at the same rpm as your power dropoff.
If you suspect an exhaust issue, try an open header pass.(if thats easily done)
Goodluck man, I hope it all works out.
peace
Hog
Last edited by hog; 10-28-2008 at 02:05 AM.
10-28-2008, 08:37 AM
#30
What indication do you see that it's "toast"? It's still switching however I see it's reading 150mv less than the one on the odd cyl bank. Could this possibly be an indication of a bad ground instead? Maybe I should try switching them side to side. The 02's were fine before the 6L swap I'm almost positive of it. Also on about 5 separate occasions since the swap, after startup I've been having what I would consider a soft miss like the truck isn't hitting on all 8 cylinders. A hard miss I would consider ignition related where it causes the engine to jerk, this definatly seems fuel related where it doesn't jerk but the engine just isn't quite firing like it should. I've checked all the injector connections and coil pack connections so I don't think that's it. Also mind you, when this occurs I AM NOT setting a cyl misfire DTC. Usually a mile or so of driving clears this up. It's similar to starting a twin cylinder engine when it's cold and it'll only hit on one cylinder until warmed up. At any rate, can someone tell me every point on the engine harness where the grounds connect? I should clean them and reattach them before I store the truck for the winter. I wonder if a bad ground is causing the bad 02 readings. Also the wideband is stuck up the tailpipe AFTER both pipes merge. Meaning if I had bad fueling on one side, I wouldn't know it since the reading is a combination of both pipes merging. Hmmm interesting point. Let's say on bank 1 I have a 13.1:1 AFR and on bank 2 I have a 12.1:1 AFR. Would this cause the CURVE of my graph to fall off like it is or just make my HP numbers higher? I'm not concerned about numbers at this point. Just confused when the curve drops off so dramatically. I hope this post makes sense.