[jtmccabe]

Today I met forza1976 at the local AWD dyno and we did a baseline comparison on our cars. The altitude at the shop is 5700'.

335i E90 (red trace) best run: 67.2°F, 6% humidity
335xi E92 (blue trace) best run: 64.8°F, 7% humidity

SAE corrected results are first, followed by uncorrected:

[335Xray]

Interesting. Thanks for sharing.

[Terry335]

Good info! Looks like the xi has a lot more drivetrain drag... I wonder if the traction makes up for it in say a 1/4 mile run?

[E90ice]

Looks like torque is about the same for both cars...just the rwhp is about 20-30 higher for the RWD car.

[Driver72]

Interesting how the xi has more hp and tq below 3000 rpms though.
Wonder why?
Is it the difference between the way the AWD and RWD is measured on the dyno?

[purplewidow]

i was just in an ice storm and my 335 with stock 189's and blizzaks non rft's did outstanding i had no problems whatsoever....i am such a fan of rwd cars....only exceptions are a veyron and a 911 turbo and of course an suv for off roading and rally cars too...that being said...99% of the rest of us don't really need rwd cars esp in la where i have seen tons of xi's on business and seeing old buddies...i just don't get it...maybe in colorado or other mountainous regions...but i went up some dam steep slope and it had a fresh layer of ice that cars ahead ween't doing so hot on....keep in mind this is the same storm that closed i80 today a lil bit west of me....i just don't see the point...

they are not as fun as rwd esp on a track,

you don't fly around in the snow anyways going 10-20 over

your wasting gas

more weight, more electronics, more stuff to break

no active steering with the 3's(which it is heaven to drive with AS)

fat in the front through turns cause of weight(more weight issues)


i could name more but you get the point....rwd for life...but there are exceptions...this applies to the 3series and similar cars...not rally beasts and 911 turbos. exotics,,,some are engineered that way so they don't spin in circles....i guess 800lb's of tq could do that though!!!! not the 300 or even 500 in this car...you can do other things to counter instead of wasting weight on that buy a better suspension and tires...you'll save in gas for sure so mod up!!!!

[CanadianTSi]

Drive train loss FTW

[LODOSS]

Tq is obviously lower otherwise HP would be the same.

Looks like the extra load on the XI made it produce boost faster?

[vbb]

I must be missing something, because it looks like the 335i is putting down 302whp and 340wtq on the dynojet and you said that was stock?

Either I'm not seeing something or that dyno reads incredibly high.

[jtmccabe]

Originally Posted by vbb

I must be missing something, because it looks like the 335i is putting down 302whp and 340wtq on the dynojet and you said that was stock?

Either I'm not seeing something or that dyno reads incredibly high.

I think the problem is that the SAE correction does not take into account the FI engine's altitude compensation. It just applies a straight ~25% altitude correction, as if the turbos aren't producing more boost to compensate for the high altitude.

[jtmccabe]

Originally Posted by LODOSS

Looks like the extra load on the XI made it produce boost faster?

IIRC, that was the theory of the guy at the shop.

[forza1976]

Originally Posted by LODOSS

Tq is obviously lower otherwise HP would be the same.

Looks like the extra load on the XI made it produce boost faster?

someone who pays attention to the details... Nice pickup

[OpenFlash]

Originally Posted by jtmccabe

I think the problem is that the SAE correction does not take into account the FI engine's altitude compensation. It just applies a straight ~25% altitude correction, as if the turbos aren't producing more boost to compensate for the high altitude.

+1 At 5000' above sea level a 335i may only loose 10-15%, not the 25% that a naturally aspirated car would loose.

Shiv

[forza1976]

JT, thanks for posting. I have the video ripped from my mini dv camera but I need to get that uploaded to youtube and I will see what I can figure out on the morning.

As for the results, they definitely have me scratching my head. The corrected numbers aside, the uncorrected HP seems to stand to reason for our test elevation of 5700 feet above sea level. The torque numbers, corrected & uncorrected, definitely have me confused as they are very high. Can't see how I would have 270ish at this altitude and 340ish at sea level.

I'm guessing those guys at MAC autosport have something interesting in the way that dyno produces its results. I know dynojets produce higher numbers but the torque numbers just seem a bit high???

Would like to have Shiv or anyone with dynojet experience to weigh in on this as I see from his posts that he has a dynojet and a good bit of experience in this dyno brand??

[forza1976]

Originally Posted by Ethirtynine

I've heard several stories of an autoshop in Parker, CO overrating dyno results: A stock automatic wrx dyno at ~250 awhp, another WRX with BPU dyno at ~300 awhp, and a bone stock Evo dyno at ~280 awhp. I'm pretty sure it MAC Autosport, unless there's another auto shop around there.

That's the one brother. Probably stands to reason that they are overrating numbers. Annoying to have that variable in the mix. But at least we have a baseline number for future mods, just have to make sure that dyno is used in the future if mods are added.

[jtmccabe]

I'm not sure about the AWD car since there are more variables, like the increased load leading to more boost and torque below 3k. But for my RWD car, I'm estimating the actual power this way:

Uncorrected figures: 243 whp, 273 wtq
Assuming loss due to 5700' altitude is 12.5% (thanks Shiv): 273 whp, 307 wtq
Assuming loss due to 6MT is 12%: 310 bhp, 349 tq

Sound reasonable? Or is 349 lb-ft too far out of the ballpark for a stock car?

[jtmccabe]

One more dyno question. Since torque can be multiplied or divided by gearing, I'm assuming the torque plot is normalized to remove gearing from the equation. For example, if one engine revolution produces two wheel revolutions, the actual torque applied to the roller is halved so the dyno doubles the torque value to compensate. Is this correct? The dude at the shop didn't seem to know.

[Nikolas]

I'm not surprised by the difference in HP at all. But the torque being the same kind of surprised me.

Thanks for the info.

[Nikolas]

Looking again, I'm actually surprised that the HP difference wasn't more? Also the curves for the 335i look much smoother.

[flipmde786]

Originally Posted by purplewidow

i was just in an ice storm and my 335 with stock 189's and blizzaks non rft's did outstanding i had no problems whatsoever....i am such a fan of rwd cars....only exceptions are a veyron and a 911 turbo and of course an suv for off roading and rally cars too...that being said...99% of the rest of us don't really need rwd cars esp in la where i have seen tons of xi's on business and seeing old buddies...i just don't get it...maybe in colorado or other mountainous regions...but i went up some dam steep slope and it had a fresh layer of ice that cars ahead ween't doing so hot on....keep in mind this is the same storm that closed i80 today a lil bit west of me....i just don't see the point...

they are not as fun as rwd esp on a track,

you don't fly around in the snow anyways going 10-20 over

your wasting gas

more weight, more electronics, more stuff to break

no active steering with the 3's(which it is heaven to drive with AS)

fat in the front through turns cause of weight(more weight issues)


i could name more but you get the point....rwd for life...but there are exceptions...this applies to the 3series and similar cars...not rally beasts and 911 turbos. exotics,,,some are engineered that way so they don't spin in circles....i guess 800lb's of tq could do that though!!!! not the 300 or even 500 in this car...you can do other things to counter instead of wasting weight on that buy a better suspension and tires...you'll save in gas for sure so mod up!!!!

Not everyone has the time (to put on), money, and/or space for another set of tires and/or wheels. At least for me, I drive my car with all-seasons, and I'm ready for anything anytime. Maybe I'm not going to perform optimally, but I'll get by. 50 degrees a week ago, and snowing today...not a problem.

If I had the time and space etc, I would buy a rwd and keep 2 sets of wheels/tires. But I know I don't.

But that's just me. People that drive around awd's with summer tires and don't bother to change them...I dunno what they're thinking.

Another thing though...I feel like with the 335, the xi maybe makes better use of the power and holds the road better than rwd. I've only experienced 335i and felt like it's too easy to break traction. I wouldn't say the same between a 330i and 330xi, although strictly powering through certain curves the xi might hold better because of the varied power distribution. But I know rwd is the overall better driving experience.

[Seth_Horwitz]

Originally Posted by flipmde786

Not everyone has the time (to put on), money, and/or space for another set of tires and/or wheels. At least for me, I drive my car with all-seasons, and I'm ready for anything anytime. Maybe I'm not going to perform optimally, but I'll get by. 50 degrees a week ago, and snowing today...not a problem.

If I had the time and space etc, I would buy a rwd and keep 2 sets of wheels/tires. But I know I don't.

But that's just me. People that drive around awd's with summer tires and don't bother to change them...I dunno what they're thinking.

Another thing though...I feel like with the 335, the xi maybe makes better use of the power and holds the road better than rwd. I've only experienced 335i and felt like it's too easy to break traction. I wouldn't say the same between a 330i and 330xi, although strictly powering through certain curves the xi might hold better because of the varied power distribution. But I know rwd is the overall better driving experience.

I agree with both of you guys. I think you might see, though, that you wouldn't break traction on a regular 335i with Ultra-High Performance rubber on the car. (Which you would obviously have to take off in the winter. I learned that the hard way with my M3 quite a few years back.) All-Season tires are GOOD all year round, but snows/summers are GREAT in their proper season. If you have the room/money for a second set of wheels, I highly reccomend it. If the wife has a problem, you could always clean the spare set really well, stack them in the living room, and call it Performance Art.

[timtech]

Seeing this make me feel really good that I ran a 12.9 with a 335xi sedan with nothing more than a SSTT and all season tires.