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jeepgcoman 12-19-2011 08:54 PM

Long Trip....Thrilled and Not So Thrilled
A week ago today I got back from another trip with my Hemi WK. This time it was over 2000 miles, and the first time I've ever had it down to sea level (My driving is normally at 2000-4000 ft.) for any length of time. About 600-800 miles was done at sea level to ~400 ft. I did my usual mileage checks, but I didn't keep track of altitudes and some of the other stats. I usually track. Here are the things that thrilled me and the things that didn't.

1. Compared to driving at altitude, when at or near sea level, the WK feels like it has a whole bunch more power. My guess is that since the beginning of the year I've picked up ~70-100 hp. at sea level......~30-40 hp. for headers and exhaust, ~40-50 hp. for cam and valve train, and ~10-30 hp. difference between 3000 ft. and sea level, based on ~10 hp. per 1000 ft. elevation. I gave it a pretty good workout a number of times and the new cam and valvetrain really comes to life more than where I usually drive.

2. Although I drive in hilly, mountainous areas most of the time, I don't get to drive on tight, winding, rural mountain roads with cows on the sides or in the middle of the road. I was able to give the lowered SRT suspension and sway bars on the WK a good workout though. I swear it handles like a sports car on the tight curves, especially when I can see far enough ahead and power out of them. If I did a lot of this type driving, I'd for sure add the SRT Brembo brakes. Great fun!!

3. I developed an exhaust leak at the header flange of the No. 1 (MDS) cylinder, probably when going over the High Sierras and Donner Pass. Because you can't hear it in the vehicle, I didn't notice it until I got to Southern CA. Around Sacamento I did notice erratic and less active MDS operation, and a noise (like popping a cork) when it went into MDS. The fuel economy deteriorated because the added oxygen introduced through the leaking flange had the O2 sensors sending a lean signal to the PCM, which caused more fuel to be added. This was quite evident when monitoring the Short/Long Term Fuel Trims with the DashHawk. I figure I lost ~2-4 mpg for at least 1/2 to 3/4 of the trip. This really bummed me out, as I was hoping for a fair improvement down at sea level. The final stats on the fuel economy were, 2162.4 miles on 111.53 gallons of 87, at elevation, and 89, at or near sea level. If my math is correct that figures out to be 19.388 mpg for the whole trip, about half of which was at elevations from ~1000-7200 ft. I had a modified 93 DS tune installed, and unlike at altitude, I did get some WOT knock retard, at sea level. None at cruise though. That was to be expected though.

4. Loose header bolts caused the leak and it'll have to be removed and a new gasket installed. What a pain in the a55 that's going to be.

Chaoul1 12-19-2011 09:07 PM

Re: Long Trip....Thrilled and Not So Thrilled
Post up some pictures of the Jeep! I want a video of your 0-60!

mrtosh 12-20-2011 12:42 PM

Re: Long Trip....Thrilled and Not So Thrilled
What're you running for headers? SRT logs?

Scottina06 12-20-2011 02:46 PM

Re: Long Trip....Thrilled and Not So Thrilled
nice write up...sux about the gasket

jeepgcoman 12-20-2011 04:20 PM

Re: Long Trip....Thrilled and Not So Thrilled
1 Attachment(s)
Mrtosh, I am running custom tubular headers with 3 in. collectors dumping into a single 3 in. system. The 3 in. system consists of a 3X12 in. glasspack, followed by a 3 in. Magnaflow 14589 muffler and a 3 in. Xlerator AP XS1229 muffler in the resonator position. Everything works great, with no MDS drone, except for the header flange exhaust leak I got on my last trip. Gaskets are on order, and work starts on Thursday. Not looking forward to it either.

Here you go. See post No. 8. And, here's the diff. between stock and header collectors:

jeepgcoman 12-20-2011 04:45 PM

Re: Long Trip....Thrilled and Not So Thrilled
Chaoul1, after the first of the year, I'll try to datalog a 0-60 time. I am curious too. Don't think it'll be that great though, since the Density Altitude where I live usually runs 4500+ ft. Race track doesn't open until April and I am hoping to have it tuned by then. For some pix of the WK, see Post 6 of this thread:

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