D
Duner
Guest
Hey guys, I'm not sure this is in the right forum.....but thought I would give it a try. I am trying to diagnose a problem I'm having with my ride.
A few months ago, I added a cat-back system to my truck. Pretty much as soon as I did this, the truck slowed down. I've been trying to figure out the root cause every since. I could feel the power start to drop off after about 5000 rpm where it used to pull fairly hard to 6500. I used a DRB and checked everything a few weeks ago. The DRB said the truck was running lean at WOT. The DRB also showed a catalytic convertor temp of 1850 at WOT. Since it showed a lean condition (that plus the dyno session), I had the pcm re-programmed to add more fuel. Now I have what appears to be a fuel induced rev-limiter at about 5100 rpm. If I make the engine rev against this "limiter" in say 3rd gear or so, the catalytic convertor temp jumps to 2600 degrees. At just partial throttle, I can get past the "limiter" feeling, but at WOT it stumbles. It really does feel and sound exactly like a rev-limiter.
I'm wondering whether the high temps are the result of too much fuel, which is being burned inside the convertor.....which is causing the high temps.
or
Is the convertor partially plugged, which is causing backpressure and not letting the engine get to the higher rpm levels. I can get the engine to 6500 if I only use 1/2 throttle. If at 6500 you mash the throttle to WOT, it immediately drops back to 5100 and stumbles. At this same time, the engine temps climb dramatically to the 220-230 degree range.
or
Another theory is that maybe I'm actually running out of fuel. I will have to check the fuel pressure tonight and see if it drops at that rpm at WOT. If it's running out of fuel and running lean...I could understand the engine water temp jumping, just not the catalytic convertor temp jumping.
What kind of catalytic convertor temps should I be seeing at WOT?
http://members.home.net/cartel5/duner/Duner47Dyno.JPG
The engine slows down dramatically once it gets hot. Any ideas?
Red curve was 1st run, green is 2nd, black is 3rd.
A few months ago, I added a cat-back system to my truck. Pretty much as soon as I did this, the truck slowed down. I've been trying to figure out the root cause every since. I could feel the power start to drop off after about 5000 rpm where it used to pull fairly hard to 6500. I used a DRB and checked everything a few weeks ago. The DRB said the truck was running lean at WOT. The DRB also showed a catalytic convertor temp of 1850 at WOT. Since it showed a lean condition (that plus the dyno session), I had the pcm re-programmed to add more fuel. Now I have what appears to be a fuel induced rev-limiter at about 5100 rpm. If I make the engine rev against this "limiter" in say 3rd gear or so, the catalytic convertor temp jumps to 2600 degrees. At just partial throttle, I can get past the "limiter" feeling, but at WOT it stumbles. It really does feel and sound exactly like a rev-limiter.
I'm wondering whether the high temps are the result of too much fuel, which is being burned inside the convertor.....which is causing the high temps.
or
Is the convertor partially plugged, which is causing backpressure and not letting the engine get to the higher rpm levels. I can get the engine to 6500 if I only use 1/2 throttle. If at 6500 you mash the throttle to WOT, it immediately drops back to 5100 and stumbles. At this same time, the engine temps climb dramatically to the 220-230 degree range.
or
Another theory is that maybe I'm actually running out of fuel. I will have to check the fuel pressure tonight and see if it drops at that rpm at WOT. If it's running out of fuel and running lean...I could understand the engine water temp jumping, just not the catalytic convertor temp jumping.
What kind of catalytic convertor temps should I be seeing at WOT?
http://members.home.net/cartel5/duner/Duner47Dyno.JPG
The engine slows down dramatically once it gets hot. Any ideas?
Red curve was 1st run, green is 2nd, black is 3rd.
