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Just got my first dyno on a dynojet for a baseline run with 3200 miles on the clock. Pretty disappointed, got 329 max HP and 324 max TQ on two back to back runs. The third was worse, but by that time the motor was pretty heat soaked. Ambient temp was 95 degrees, and it was running pretty rich above 5000 rpm, but I still think the numbers are on the low side. The guys at the dyno shop said they had dynoed three other GTOs and all were in the 340 range, but during cooler temps. Since I have owned the car, I knew it was not a factory freak and it has kind of felt down on power since I started playing a little. Did the proper 500 mile break in and even changed the oil at the 1000 mile point and then again at 3000. Changed the plugs awhile back and the plug in the left bank (driver side) cylinder just one up from the firewall keeps getting the porcelain black after only a week. All other cylinder's plugs are crystal clear so I may have a problem with either an injector or possibly a ring that never got seated. I'll post the graph as soon as I can get it scanned. I think I'll take it to the dealer and have them scan the computer and investigate the one cylinder.
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05 GTO MN6 (Blk/Blk), NGK TR55IXs, more coming...
 

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I have no interst in perusing Mustang message boards, but if anyone has or wants to, I would be interested in knowing the Dyno numbers off the 05. Specifically posts where the owner referenced high ambient temps and humidity. The RWHP shouldnt be more than 235 all things being equal. I am interested in thier loss due to temp.
 

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JMVorbeck said:
I have no interst in perusing Mustang message boards, but if anyone has or wants to, I would be interested in knowing the Dyno numbers off the 05. Specifically posts where the owner referenced high ambient temps and humidity. The RWHP shouldnt be more than 235 all things being equal. I am interested in thier loss due to temp.
I lurk a little bit to see what the competition has/does. I've mostly seen 260 to 275 in stock trim. they seem to vary more than LS1/LS2 cars. With an exhaust and an intake and a tune, most are in the 300 range at the wheels.
Definately better than the 99-04, those cars were in the 215 to 225 range.
 

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The Mustangs are pretty easy and cheap to make fast, but any engine will lose power due to heat and humidity. My 2001 Cobra would drop almost 20 rwhp in a single dyno session and it was, like the GTO, an all aluminum motor. It got heat soaked very quickly.

BTW, I still love Mustangs (still not a fan of the new one yet with the exception of the new Cobra), but I love my GTO and got a good deal on it.
 

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Yes the heat and humidity probably had a good hand in affecting what outcome you had on the results. Also though, like you said you only have 3200 miles on it so far, meaning the engine more than likely isn't completely broken in and performing at its peak. I've heard people saying that even at 15k miles the car seems to pick up another amazing boost in power. So most likely just keep driving the baby around and get more miles on it and the engine will just become stronger and stronger. On mine I noticed the first major power boosts at 500 and then 1000 miles. Then another at I think 3500, and I'm right around 5100 miles right now. Hopefully I'll be expecting another nice boost in performance soon ;)
 
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