15:1 Air/Fuel Ratio. How bad is that? - The Unofficial BMW M5 Messageboard (m5board.com)

bluestreak · 27th March 2005, 08:58

i had a dyno today and the air to fuel ratio was 15:1. Not to mention that the dyno result were 328hp and 298 torque(yes it's an s2). there is no doubt that my torque number have gone way down since i got the s2. i dynoed one time at 352hp and 308 torque. but dynoed at 328 and 316 with just the s1. someone help me understand whats going on.

mottati · 27th March 2005, 09:04

i have a hard time beliving that. How does the car feel? Stronger than before? That afr is lean, dinan is typically conservative, which is rich at high load. The guys at powerchip can usually gain 8-12 hp on an s2 by leaning it out a bit, i believe. Is this the same dyno you ran on before?

bluestreak · 27th March 2005, 09:27

no it's not the same dyno. yes the car feels a little stronger but i can also feel the torque loss. it was also dynoed in 4th with no fuses pulled(not my fault). the new dinan clutch feels slippery. it doesnt sound right to me. these are two runs done on the same dyno. it doesnt matter what dyno i went to my car shouldnt lose torque.

run 1 328hp 316torque (S1)
run 2 347-352hp 298-308 torque (S2)

however the a/f ratio cant be good. can it be fixed? i know they dont really do anything but download the dinan overwrite program.

i was told that lean means that the motor is getting the right amount of fuel and cylinders could detonate and that running richer would increase horsepower.

jimmyz2 · 27th March 2005, 09:30

Go to Buford BMW and tell you want a refund.

mottati · 27th March 2005, 09:35

I had asked wayne at powerchip about the afr from the dyno shop after getting my car dyno'd after the headers. He said there are way too many variables to getting an acurate afr on a dyno, from the position of the tail pipe sniffer to basic maintanance of the dyno and afr analyzer, so i wouln't put too much weight on that. If the clutch is slipping, that could certainly be a factor. Not removing the fuses is also a problem, as most M5's that i've seen dynoed cut back on power at the top end as the dsc goes crazy with the rear wheels at 120+mph while the fronts are stationary.

According to all the dinan literature, your s2 should have more torque everywhere, not less. On my car, i lost about 10hp at 3k rpm with the headers, but i feel it's something i can barely feel, and the mid-top end gains more than make up for it. I wonder if there's something else not right on your car, like a mafs, cps or??

If I were you, first thing i'd do is go to another dyno shop, if you still get crappy numbers, go back to your dinan people.
Mike

Quote:

Originally Posted by bluestreak

no it's not the same dyno. yes the car feels a little stronger but i can also feel the torque loss. it was also dynoed in 4th with no fuses pulled(not my fault). the new dinan clutch feels slippery. it doesnt sound right to me. these are two runs done on the same dyno. it doesnt matter what dyno i went to my car shouldnt lose torque.

run 1 328hp 316torque (S1)
run 2 347-352hp 298-308 torque (S2)

however the a/f ratio cant be good. can it be fixed? i know they dont really do anything but download the dinan overwrite program.

bluestreak · 27th March 2005, 09:38

i considered getting rid of my m5 today for the first time because this is way to frustrating for the money being spent. i was going to get the dinan supercharger but at the rate im gaining power ill end up with maybe 400 at the rear wheels even with it.

we changed the position of the tailpipe sniffer and they even connected to the computer module that is used by emmisions, there cant be any error in that. the readings were the exact same. i will admit that the guys who dynoed my car had no clue about how to dyno and m5. they were used to dynoing 350z's but still i think those results are bad. the car feels like it want to accelerate like mad then it hits like an 85% sprint at wot. it doesnt feel or sound right to me.

gsfent · 27th March 2005, 09:40

Quote:

Originally Posted by bluestreak

no it's not the same dyno. yes the car feels a little stronger but i can also feel the torque loss. it was also dynoed in 4th with no fuses pulled(not my fault). the new dinan clutch feels slippery. it doesnt sound right to me. these are two runs done on the same dyno. it doesnt matter what dyno i went to my car shouldnt lose torque.

run 1 328hp 316torque (S1)
run 2 347-352hp 298-308 torque (S2)

however the a/f ratio cant be good. can it be fixed? i know they dont really do anything but download the dinan overwrite program.

Assuming the dyno is measuring correctly, that is way lean at WOT. The S2 adds the Dinan headers. It is almost as if someone forgot to reprogram the ECU to account for the headers. At part throttle you may not be doing much harm, but at WOT you want to be in the 12's. Air leaks usually cause a rich condition, so have someone check your ECU.
Regards
Jerry

mottati · 27th March 2005, 09:41

Quote:

Originally Posted by bluestreak

i considered getting rid of my m5 today for the first time because this is way to frustrating for the money being spent. i was going to get the dinan supercharger but at the rate im gaining power ill end up with maybe 400 at the rear wheels even with it.

The real potential problem with the M5 is all of the little electronic sensors and obd2 stuff. If everything isn't working at 100% the car will be down on power. Do you have a code reader? Might be worth checking if there are any fault codes stored.
Mike

bluestreak · 27th March 2005, 09:48

i really just need to go to the track and see what it does. if my 1/4 mile times and traps are slow then ill be major league pissed. im only in the minors right now, AAA league. but thanks for the inpu guys and any further info is greatly appreciated.

jimmyz2 · 27th March 2005, 09:50

"I had asked wayne at powerchip about the afr from the dyno shop after getting my car dyno'd after the headers. He said there are way too many variables to getting an acurate afr on a dyno, from the position of the tail pipe sniffer to basic maintanance of the dyno and afr analyzer, so i wouln't put too much weight on"

In all reality,I just don't and cannot accept this statement.