Is my exhaust system too restrictive for my 6.0L? :TECH ONLY:
10-27-2008, 02:54 PM
#1
Is my exhaust system too restrictive for my 6.0L? :TECH ONLY:
Ok, well as I'm sure a lot of you have been following along with my 6L build and I stare at my dyno graph hour after hour and I still cannot for the life of me figure out WHY the power falls off so dramatically after 5200RPM. I suppose I can tear into the engine and check the valve timing and events but I am wanting to take a scientific approach to this, not a "try this or that" approach without any valid logic to back it up. The build again in a nutshell is as follows
6.0L
10.6:1 comp
hand ported 243 heads (just the bowl area area around the valves, nothing with the port shape was changed.
Stock truck intake with 44 lb/hr marine injectors
Vmax motorsports 218/224 .561/.581 114LSA +2adv
OBX long tube headers with offroad Y. (we'll get to talking about this in a minute)
3" single pipe coming off the ORY into a SI-SO magnaflow muffler and out the side.
When ordering the OBX long tubes I ordered them for a 4.8/5.3L so that it would hook up to my existing home made magnaflow catback without modification. The ORY that comes with the OBX kit looks identical to the pacesetter ORY but it has resonators (no biggie) and then they merge into the magnaflow catback. Just like shown here.
Does anyone see anything wrong with this? I was going to buy an exhaust back pressure guage but when I saw the price on one I was like yowsers! $110 for a cheapie. I am wondering if the setup is working so good that the exhaust even if it's slightly restrictive, is dramatically making it worse than an engine that would have stock heads. This is just bugging the hell out of me as I know everything in this combo is perfect except possibly the cam timing and or the exhaust. There's no reason the truck intake shouldn't go up to 6200 on a 6.0L
Here's my best dyno run as a refresher.
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.
.
6.0L
10.6:1 comp
hand ported 243 heads (just the bowl area area around the valves, nothing with the port shape was changed.
Stock truck intake with 44 lb/hr marine injectors
Vmax motorsports 218/224 .561/.581 114LSA +2adv
OBX long tube headers with offroad Y. (we'll get to talking about this in a minute)
3" single pipe coming off the ORY into a SI-SO magnaflow muffler and out the side.
When ordering the OBX long tubes I ordered them for a 4.8/5.3L so that it would hook up to my existing home made magnaflow catback without modification. The ORY that comes with the OBX kit looks identical to the pacesetter ORY but it has resonators (no biggie) and then they merge into the magnaflow catback. Just like shown here.
Does anyone see anything wrong with this? I was going to buy an exhaust back pressure guage but when I saw the price on one I was like yowsers! $110 for a cheapie. I am wondering if the setup is working so good that the exhaust even if it's slightly restrictive, is dramatically making it worse than an engine that would have stock heads. This is just bugging the hell out of me as I know everything in this combo is perfect except possibly the cam timing and or the exhaust. There's no reason the truck intake shouldn't go up to 6200 on a 6.0L
Here's my best dyno run as a refresher.
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.
.
Last edited by hirdlej; 10-27-2008 at 03:33 PM.
10-27-2008, 03:36 PM
#7
This is the only part in my motor that I CANNOT assure you of. I never degreed it but installed it dot to dot. - I would like to remedy this just before yanking the cam out. I may try putting a dial indicator on the valve stem before I put the truck away for storage in a week.
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10-27-2008, 03:47 PM
#10
Do you have a log of a WOT run, doesn't have to be the dyno runs, just any run where you log Dyncylair_dma (that is the EFI Live PID, hopefully it is same in HP Tuners.)...
Nevermind, I remember that you posted that your were SD....
Nevermind, I remember that you posted that your were SD....
Last edited by BlackGMC; 10-27-2008 at 03:53 PM.