Very strange dyno results today - with Power Kit and Performance Exhaust installed

cstavaru · 01-12-2010, 07:33 AM

Hi,

So, first time testing the car in stock form I obtained 271whp on a Mustang Dyno (about 6 months ago). 95 octane used (101 octane euro).

Second time, with the BMW Performance Power Kit installed, I obtained 297whp. The same gas used (95 octane - 101 octane euro).

And today, one month after I had the BMW Performance Exhaust installed, I obtained a whooping...252whp...

I used the same gas as before. This time though I had the winter tires which are 225/45/17 instead of my usual 255/45/17 tires.

All the results are wheather corrected, on the same dyno at the same location.

I immediately headed to my dealer to ask if the Power Kit software is still there and was not overwritten by mistake during service. But the tech said its impossible, because I only had an oil change and the BMW Performance Exhaust install, both of which do not require reprogramming and a reprogramming requires the customer consent. He suggested to refill the gas tank with another brand.

Indeed, I came to the conclusion that the gas I have used today was bad: after I filled with the 95 octane gas, I felt no difference whatsoever comparing to the gas I have used until today (91 octane). Maybe a bit worse. Previously, when I filled the car with the 95 after 91, the difference was very significant. In our country there is a history of gas station employees adding water and substracting gas from the tanks.

I will switch the gas to another brand's 95 octane flavor and then re-test...

But, can the horsepower difference be this big ? Makes me wonder...

SIEN · 01-12-2010, 07:41 AM

Dynos can be heartbreakers... don't trust them. Trust your own feelings on how quick the car feels. Does it feel quicker? Is it quick enough?

cstavaru · 01-12-2010, 07:46 AM

Quote:

Originally Posted by SIEN

Dynos can be heartbreakers... don't trust them. Trust your own feelings on how quick the car feels. Does it feel quicker? Is it quick enough?

The car is just as fast as when using 91 octane. Plenty fast...but (usually) when I fill with 95, the turbo lag is gone and the car is significantly faster.

NRG · 01-12-2010, 07:46 AM

Interesting... I don't think that 4 octane points would shave off 40hp. Tire weigh does impact as well, but I don't think by that much. How's the but dyno feels after the exhaust installation? Is it possible that dyno was recalibrated after your last visit? Do as you said change the 95 brand and redyno.

enrita · 01-12-2010, 07:49 AM

you should always dyno using the same wheels .

cstavaru · 01-12-2010, 07:56 AM

Quote:

Originally Posted by NRG

Interesting... I don't think that 4 octane points would shave off 40hp. Tire weigh does impact as well, but I don't think by that much. How's the but dyno feels after the exhaust installation? Is it possible that dyno was recalibrated after your last visit? Do as you said change the 95 brand and redyno.

The butt dyno felt great immediately after exhaust install.I remember I had good 95 octane (101 euro) gas in the tank. But after that I filled only with 91 and felt ok, like it always felt with 91.

The winter tires (17" Goodyear GW3 run-flats) are heavier than stocks (17" Bridgestone Potenza RE050A run-flats), but could this make enough difference ?

marcel b · 01-12-2010, 08:33 AM

cannot imagine that change of tires make such a difference, especially as you staid with 17 inch. Maybe the wintertires are heavier, on the other side, the are only 225 and not 255, so the weight difference is I think marginal.
40HP you would would also feel, so if you don't feel a difference, it is strange the dyno gives such a difference.
To see the impact of a mod I do a before and after measurement using a driftbox (40-140kmh) This for me is more significant then a number on a dyno.

SIEN · 01-12-2010, 09:11 AM

Quote:

Originally Posted by marcel b

To see the impact of a mod I do a before and after measurement using a driftbox (40-140kmh) This for me is more significant then a number on a dyno.

+1 Dyno can only be reasonably accurate with same day/conditions... just too many variables to consider. Vbox testing from a roll and, importantly, your butt dyno is probably the best way to go.

Mike@N54Tuning.com · 01-12-2010, 09:16 AM

Quote:

Originally Posted by SIEN

+1 Dyno can only be reasonably accurate with same day/conditions... just too many variables to consider. Vbox testing from a roll and, importantly, your butt dyno is probably the best way to go.

+1

Mike

Proper Motion LLC · 01-12-2010, 10:05 AM

Quote:

Originally Posted by NRG

Interesting... I don't think that 4 octane points would shave off 40hp. .

Maybe not 40hp, but it will make a big difference. I remember with the JB+ preliminary testing 93 octane @ 75% setting made 20 more RWHP than 91 octane @ 75% setting. And that's just a 2 point difference.

And I believe it's been said our DME can make power adjustments depending on fuel up to 95-96 octane. (Without a piggy back or reflash I believe)

jpsimon · 01-12-2010, 10:13 AM

snow tires can mak a bigger difference on the dyno than you folks out there that never use them may think. Depending on model/brand they can be extremely soft and wobbly at speed (due to the very soft the tread and sidewall). but this is the one reason I'm not going back to the dyno until spring. gotta love 205/50 snow tires

01-12-2010, 07:33 AM	#1
cstavaru Brigadier General 313 Rep 3,262 Posts Drives: 2009 335i M Sport Sedan 6MT Join Date: Aug 2008 Location: Bucharest, Romania iTrader: (0)	Very strange dyno results today - with Power Kit and Performance Exhaust installed Hi, So, first time testing the car in stock form I obtained 271whp on a Mustang Dyno (about 6 months ago). 95 octane used (101 octane euro). Second time, with the BMW Performance Power Kit installed, I obtained 297whp. The same gas used (95 octane - 101 octane euro). And today, one month after I had the BMW Performance Exhaust installed, I obtained a whooping...252whp... I used the same gas as before. This time though I had the winter tires which are 225/45/17 instead of my usual 255/45/17 tires. All the results are wheather corrected, on the same dyno at the same location. I immediately headed to my dealer to ask if the Power Kit software is still there and was not overwritten by mistake during service. But the tech said its impossible, because I only had an oil change and the BMW Performance Exhaust install, both of which do not require reprogramming and a reprogramming requires the customer consent. He suggested to refill the gas tank with another brand. Indeed, I came to the conclusion that the gas I have used today was bad: after I filled with the 95 octane gas, I felt no difference whatsoever comparing to the gas I have used until today (91 octane). Maybe a bit worse. Previously, when I filled the car with the 95 after 91, the difference was very significant. In our country there is a history of gas station employees adding water and substracting gas from the tanks. I will switch the gas to another brand's 95 octane flavor and then re-test... But, can the horsepower difference be this big ? Makes me wonder... __________________ Mods(click): Cobb + RB Turbos \| Aquamist HFS-4 Meth \| Drexler LSD \| Bilstein B12 Pro-Kit \| Custom K&N Apollo Intake \| Wagner Intercooler \| Macht Schnell Downpipes \| BMW Performance Power Kit \| BMW Performance Exhaust \| BMW Performance Short Shifter \| M3 Subframe Bushings \|
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01-12-2010, 07:41 AM	#2
SIEN 23 Rep 130 Posts Drives: Quickly Join Date: Sep 2009 Location: US/UK iTrader: (0)	Dynos can be heartbreakers... don't trust them. Trust your own feelings on how quick the car feels. Does it feel quicker? Is it quick enough?
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01-12-2010, 07:46 AM	#4
NRG Lieutenant Colonel 36 Rep 1,658 Posts Drives: 2012 X5 35d Join Date: Mar 2007 Location: Montreal QC iTrader: (5)	Interesting... I don't think that 4 octane points would shave off 40hp. Tire weigh does impact as well, but I don't think by that much. How's the but dyno feels after the exhaust installation? Is it possible that dyno was recalibrated after your last visit? Do as you said change the 95 brand and redyno. __________________ Retired: 2005 N52 E90 330i Sport 6AT Retired: 2007 N54 E92 335i Sport 6AT Current: 2012 M57 E70 X5 xDrive35D
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01-12-2010, 07:49 AM	#5
enrita Major General 161 Rep 7,377 Posts Drives: 335i - Big turbos Join Date: Sep 2008 Location: Italian in Sweden iTrader: (0)	you should always dyno using the same wheels . __________________ 07 335i AT - MOTIV 750 - MHD E85 BMS flash - BMS PI - JB4G5 - Okada Coils - NGK 5992 Plugs - Helix IC - Snow Stg. 3 - Stett CP - Custom midpipes with 100 HJS Cats - Bastuck Quad - PSS10 - QUAIFE LSD - BMS OCC - Forge DVs - AR OC - ALCON BBK - M3 Chassi - Dinan CP - Velocity M rear Toe arms - Advan RZ-DF - LUX H8 - Level 10 AT upgrade
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01-12-2010, 08:33 AM	#7
marcel b Lieutenant Colonel 132 Rep 1,898 Posts Drives: F31 340i Join Date: Jun 2009 Location: Europe iTrader: (0)	cannot imagine that change of tires make such a difference, especially as you staid with 17 inch. Maybe the wintertires are heavier, on the other side, the are only 225 and not 255, so the weight difference is I think marginal. 40HP you would would also feel, so if you don't feel a difference, it is strange the dyno gives such a difference. To see the impact of a mod I do a before and after measurement using a driftbox (40-140kmh) This for me is more significant then a number on a dyno.
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01-12-2010, 10:13 AM	#11
jpsimon Team Zissou 3065 Rep 10,197 Posts Drives: 2022 AWD M3 Comp - SMB Join Date: Dec 2006 Location: CT iTrader: (7)	snow tires can mak a bigger difference on the dyno than you folks out there that never use them may think. Depending on model/brand they can be extremely soft and wobbly at speed (due to the very soft the tread and sidewall). but this is the one reason I'm not going back to the dyno until spring. gotta love 205/50 snow tires Last edited by jpsimon; 01-12-2010 at 10:29 AM..
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