BMW Bi-turbo engine

BMW would soon be releasing a bi-turbo version of their I6, that would lead to a gain of 51 HP to 306, and torque to 293 (gain of 73). The link below has additional details

http://www.topgear.com/content/news/stories/527/

This sounds so exciting!! With the new engine, I am pretty sure a 530 would feel very fast, close to a 545/550. I would think it would shave .5 from the current 0-60 number to < 6.1.

But it looks like we have to wait about an year to see this on the 5 series - long wait indeed.

Do you see any cons to BMW adopting the turbo route? Would it be as smooth as the current I6? How about turbo lag? How about relaibility? There would be more complexity in the engine which may make it less reliable in the long run.

Any idea why BMW did away with turbo engines in the 80-90s? And why are they bringing it back again? Aren't turbo engines supposed to be less reliable than their regular counterparts?

Reply » BMW Bi-turbo engine

"... By using two smaller turbos instead of one large one, BMW reckons it has eliminated turbo lag..."

There's an answer right there. Sure sound VERY exciting

...I am ready to place my order but with the confirmed facelift and news of Twin Turbo engines, 1 year seems like it may be worth the wait.

One con however, maybe the need to cool down the turbo before turning off the engine...???

It's been a while since I last had my GS-X which I had a turbo timer in it, but maybe turbos now a days no longer need to cool off with the engine on???

Reliability sure is another factor to really take into consideration with turbos.

Maybe BMW did away with the Turbos in the 80~90's since they were less sophisticated, less reliable, more expensive.

Can't wait to get more news and confirmation of implementation of the Twin Turbo engine into the 5 Series

Reply » BMW Bi-turbo engine

Quote:

Do you see any cons to BMW adopting the turbo route? Would it be as smooth as the current I6? How about turbo lag?

The fact that the two small turbos combined don't have appreciable lag is what frees BMW to offer a turbo engine. The new bi-turbo plant is supposed to offer most of the torque (90%?) from 1800 rpm up to the power peak. So yeah, expect it to be smooth. Turbo lag is why BMW stayed with naturally-aspirated engines until now.

Quote:

And why are they bringing it back again?

More power from small-displacement engines, which means better performance with efficiency, and the two small turbos bring it with no lag.

Reply » BMW Bi-turbo engine

If the 306hp bi-turbo does go to e60, say, in MY2008 as 535, we'll see:

1) 535 will be as fast as 540. Recalling the number of 540 in 2001, 282hp, 0-60 in 6.2 seconds (5-spd auto) and 5.8 (6-spd manual). 535 will have more hp, less weight, and 1 more gear for auto, so its performance should be in par with the 540 5 years ago.

2) The reason that BMW didn't use turbo engine (for US market) for 2 decades is - turbo lag. At that time, turbo engine produced great output but along with turbo lag. It might fit sports cars well, but definitely not a good choice for sedan. Now with technology improvement, it's no longer a problem.

3) However, long-term reliability and maintainability is still a issue, as X550-ED indicated. An old turbo engine tends to be more trouble-prune than an N/A engine. One thing I don't understand is - why BMW not just simply use a bigger N/A engine, say 3.5L? Someone may say it breaks the 50/50 weight balance, but since BMW can balance the even-heavier 4.8L engine, 3.5L shouldn't be an issue.

4) It does come with some product lineup issues: 306hp with less weight will make 535 too close to 550 in terms of performance. Also, usually Z4 shares the platform with 3 couple. If 335 coupe, why not Z4 3.5 (or Z4 3.0S or whatever names), then it will too close to the just introduced 330hp Z4 M.

I planned to buy a NY2007 e60 with the hope of either engine bump-up or "de-banglizing" facelift or ideally both. To me, it worths waiting.

Reply » BMW Bi-turbo engine

You should all be very excited about a turbo engine!

First, if the I-6 is getting the turbos, it will be just as smooth (you don't feel any vibration from the turbo itself).

Second, turbo power is relatively "free" - meaning you don't lose horsepower to accessory drag (like a supercharger). It is all waste gas driven.

Third, it is very easy to increase hp output on a turbo motor. The engine will have stock "boost" (the pressure fed into the engine). Raise it a few pounds, and you get gobs more power. As long as the EFI doesn't allow predetonation, it is relatively safe. I would expect an easy bump to 325 hp, with 350 hp an simple stretch. Want more power? Add a larger intercooler, larger turbo, more fuel, and more boost...

Fourth, with synthetic oil, and modern cooling systems, burnt bearings are pretty much a thing of the past. After a hard run, just drive mellow for a minute or two... no big deal. A turbocharger unit should last 80K miles.

Reply » BMW Bi-turbo engine

Quote:

"... By using two smaller turbos instead of one large one, BMW reckons it has eliminated turbo lag..."

There's an answer right there. Sure sound VERY exciting

...I am ready to place my order but with the confirmed facelift and news of Twin Turbo engines, 1 year seems like it may be worth the wait.

Porsche has been using 2 turbos on the 911 Turbo ("twin turbo") for years, and there is definitely turbo lag on those cars--time will tell on the BMW engine.

The 997 turbo has variable turbine geometry, which is supposed to dramatically reduce lag.

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