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Last Friday I decided to take our new to us 2010 X5M and my 2000 M5 to Pompeii Motorsports here in Greenville SC to do some dyno pulls. The X5M is bone stock and has about 32,000 miles on it. The M5 has about 166,000 miles on it and as far as engine performance mods go it has a dinan CAI, Dinan stage 2 flash, IAT Relocation, and a muffler delete.

I’ve had the M5 for about 7 years now and lately it has been feeling a little low on power. So I changed the spark plugs, All CPS, TPS, MAFs, O2 sensors, Fuel Filter, cleaned and changed the O-rings on the vanos solenoids, replaced the oil separators and all hoses around and under the plenum, and changed the thermostat. After doing all that the car felt better but still didn’t seem to have the kick I remember it once having. I do understand I’ve had the car for a while now and this “power loss” may be imaginary but it sure seems real. So this sparked my interest to try to get some hard numbers to support my suspicion and help me to gauge the health of the engine.

The dyno is a mustang dyno and it was pretty cold out, about 37 degrees I think. The X5M was up first and on its best pull made 488HP & 470TQ. I was pretty happy with those results. Next up was the M5 and on its best pull made 301HP & 314TQ and I was pretty disappointed with those results. I was really hoping it would make somewhere around 350HP. I had previously dyno’ed it about 3 or 4 years ago at dyno labs in Georgia and it put down 348HP with only the muffler delete and it was about 80 degrees outside. The previous dyno was a dynojet so I did expect a little bit lower of a number than before but I figured with the intakes, stage 2 tune, and the fact that it was like 40 degrees colder would have made up for the difference.

With the X5 making as good of numbers as it did I’m thinking I have not found my power loss culprit yet for the M5. I’m thinking possibly the cats are finally getting gunked up, my fuel pump may be on the way out, or maybe I have a vacuum leak or something somewhere. Other than that I think I have pretty much covered all other maintenance that may be stealing performance. Some guys that were there at the shop were saying that given the amount of miles on the engine those aren’t bad numbers but I can’t accept that.

Anyone have any thoughts or suggestions that I may be overlooking?
 

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Nice.
I do miss my 2011 X5M.
I ran a 12.58 with my much lighter winter rim/tire setup.

I forget, but don't X5Ms typically dyno a bit higher? Could be your dyno is reading a bit low.
 
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