The Mother of all 335i vs IS350 threads (please read 1st post in thread!)
07-21-07, 12:02 AM
#812
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If only because of the ongoing debates here, I stopped by the local BMW dealer last night took a long test drive in the 335i, with a very accomodating salesman.
It had a sport suspension and a 6 speed transmission. My butt factor didn't think it was any faster than the 350, but that stick shift sure is more fun to drive. Very smooth and short shifts. The gearing requires getting out of first a bit too fast for me, there was no turbo lag in first gear and a little in second. If there is any real acceleration difference between the two, you'll only feel it on the track or doing dumb stuff on public roads...if then.
The 335i interior is no match for the Lexus in style, comfort or quality, and the 335i lists out for about $6K more than a similar IS350. My girlfriend kept asking if it came with a leather interior....and the salesman had to tell her twice, that it was an upgraded leather interior.
The 335i is a sports car with some luxury, while the IS350 is a sporty car with much more luxury. Take your pick.
It had a sport suspension and a 6 speed transmission. My butt factor didn't think it was any faster than the 350, but that stick shift sure is more fun to drive. Very smooth and short shifts. The gearing requires getting out of first a bit too fast for me, there was no turbo lag in first gear and a little in second. If there is any real acceleration difference between the two, you'll only feel it on the track or doing dumb stuff on public roads...if then.
The 335i interior is no match for the Lexus in style, comfort or quality, and the 335i lists out for about $6K more than a similar IS350. My girlfriend kept asking if it came with a leather interior....and the salesman had to tell her twice, that it was an upgraded leather interior.
The 335i is a sports car with some luxury, while the IS350 is a sporty car with much more luxury. Take your pick.
Last edited by fantom; 07-21-07 at 12:07 AM.
07-21-07, 12:02 AM
#813
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Speaking of speed, I wonder why no-one mentions how better IS350 performs in street start (5-60 acceleration). IIRC, the official numbers were
IS350 4.9sec
335i 5.6sec
There's significant difference, and street start is way more important number for real life driving than 0-60. Just my two cents...
IS350 4.9sec
335i 5.6sec
There's significant difference, and street start is way more important number for real life driving than 0-60. Just my two cents...
07-21-07, 08:25 AM
#814
Speaking of speed, I wonder why no-one mentions how better IS350 performs in street start (5-60 acceleration). IIRC, the official numbers were
IS350 4.9sec
335i 5.6sec
There's significant difference, and street start is way more important number for real life driving than 0-60. Just my two cents...
IS350 4.9sec
335i 5.6sec
There's significant difference, and street start is way more important number for real life driving than 0-60. Just my two cents...
What I do like a BMW / 335i, is that we can just Mess up the engine some much faster, with additional mods
THAT actually add REAL HP!
07-21-07, 08:28 AM
#815
Lexus Champion
We can see from this side by side test http://www.edmunds.com/insideline/do.../pageId=124138 that the automatic 335i is definitely the faster car. Also interesting that the BMW has a quieter engine.
In the 70's and 80's, I'd be hard pressed to pick a winner. As most have mentioned, it's probably closer to a wash. It did sound like the 335 needed a little more finessing and timing to get it's best time.
07-21-07, 11:55 AM
#816
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It's a fact? No it isn't. It's a myth. Turbos work off pressure ratios. Less pressure in, less pressure out. End of story. If you don't modify anything, you get the same power loss as an NA engine. It's physics. Boost is measured PSIG not PSIA, so 14 psi at sea level isn't the same as 14 psi in Denver. Your number in Denver still comes up just as short as it does for the NA boys.
Oh, yeah, I've lived in Denver and tuned motorcycles there too, so I have a pretty strong foundation in how this stuff works at altitude.
Oh, yeah, I've lived in Denver and tuned motorcycles there too, so I have a pretty strong foundation in how this stuff works at altitude.
The amount of boost is determined by the speed of the impellor, so at lower pressures it just spins faster taking longer to produce max boost (more lag) but still get to the same amount of power (or closer, anyway).
Right?
07-21-07, 12:15 PM
#817
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It's a fact? No it isn't. It's a myth. Turbos work off pressure ratios. Less pressure in, less pressure out. End of story. If you don't modify anything, you get the same power loss as an NA engine. It's physics. Boost is measured PSIG not PSIA, so 14 psi at sea level isn't the same as 14 psi in Denver. Your number in Denver still comes up just as short as it does for the NA boys.
Oh, yeah, I've lived in Denver and tuned motorcycles there too, so I have a pretty strong foundation in how this stuff works at altitude.
Oh, yeah, I've lived in Denver and tuned motorcycles there too, so I have a pretty strong foundation in how this stuff works at altitude.
07-21-07, 03:00 PM
#819
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Yep, I don't think anyone is disputing that. Take two engines, add n turbos to one and it will have more power than the NA engine at any altitude. I think the question is whether the losses to turbo engines are greater, less than or equal to NA engines at a higher altitude.
Everything I've ever read, heard, been told (apart from Lobux's comments above) leads me to believe that Turbo performance is less affected by altitude than NA. That being said, I want to hear the truth with explanation if Lobux is right, and I'll give credit where credit is due.
Everything I've ever read, heard, been told (apart from Lobux's comments above) leads me to believe that Turbo performance is less affected by altitude than NA. That being said, I want to hear the truth with explanation if Lobux is right, and I'll give credit where credit is due.
07-21-07, 05:12 PM
#820
Ran a 335 from 60-125 in my 350. I would say the cars are very close, but he could not close the gap at all. And I am not biased one way or another; my other car is an E46 M3.
07-22-07, 08:09 AM
#824
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It is not a myth. This has to be one of the poorest responses I have seen. Altitude has a major effect on NA engines, and much less on turbo engines. It is very simple to figure out. At Denver, you are down about 2.5 PSI of air pressure. So, 12.2/14.7(see level pressure) = - 17% loss. With a turbo with 10PSI of boost it would be (10psi + 12.2 at elevation) 22.2/24.7 (10+14.7 at sea level) = 8% loss. So you can see turbo's lose less power. More importantly, the BMW adds additonal boost (up to 3psi) at altitude to help compensate even more, so you are losing even less
10 psi boost @ sea level = pressure ratio 1.68
10 psi boost @ your chosen altitude = PR 1.82
This is an 8.3% increase in pressure ratio.
Depending entirely on where you fall on the compressor map, you will (more than likely) lose efficiency and therefore not make the power you expect. If the turbo is significantly oversized, you might stay closer to the efficiency you'd have at sea level, but you are still spinning the turbo faster, so there is more heat being generated.
It's physics, plain and simple. It is not simple arithmetic as you would want me to believe.
07-22-07, 10:41 AM
#825
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This isn't my practical experience. My Supra at Lake Tahoe was just as weak as my Corsica. You are assuming the turbo has the same efficiency at 10 psi with a 12.2 psi input. It doesn't. That's why there are compressor maps for sizing turbos, so you can see impeller speed, efficiency, and pressure ratio. To get that same 10 psi you got at sea level, you are going to have to turn the impeller faster. There is no way around it. When you do that, you lose efficiency, so more of the boost shows up as heat not actual air molecules moved. To use some arithmetic:
10 psi boost @ sea level = pressure ratio 1.68
10 psi boost @ your chosen altitude = PR 1.82
This is an 8.3% increase in pressure ratio.
Depending entirely on where you fall on the compressor map, you will (more than likely) lose efficiency and therefore not make the power you expect. If the turbo is significantly oversized, you might stay closer to the efficiency you'd have at sea level, but you are still spinning the turbo faster, so there is more heat being generated.
It's physics, plain and simple. It is not simple arithmetic as you would want me to believe.
10 psi boost @ sea level = pressure ratio 1.68
10 psi boost @ your chosen altitude = PR 1.82
This is an 8.3% increase in pressure ratio.
Depending entirely on where you fall on the compressor map, you will (more than likely) lose efficiency and therefore not make the power you expect. If the turbo is significantly oversized, you might stay closer to the efficiency you'd have at sea level, but you are still spinning the turbo faster, so there is more heat being generated.
It's physics, plain and simple. It is not simple arithmetic as you would want me to believe.