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      05-13-2021, 09:08 PM   #1
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Can you feel turbo on M50i

The X5 M50 is my first turbo and have a (stupid?) question. Are you supposed to feel the turbos kick in? I kept it in 2nd gear from about 1000rmp to redline and did the same thing in 3rd gear. I just felt constant acceleration, but no boost.

I had it in the dealer the last few days because they had to replace the steering rack which involved dropping the suspension, getting a realignment, etc. I took it for a spin after. Believe me it's still fast, but I swear I could feel more of a boost when accelerating before I took it in. Maybe it's just my imagination. Is there any way to test if the turbos are acting normal??
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      05-14-2021, 10:57 AM   #2
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The turbos are there and active. "Kick in" was what many turbocharged engines did in the past or at least gave that general feel as a result of what is know as turbo lag. This has been eliminated to a great extent if not totally on some engines.
Be glad that you don't need to wait for them to "kick in".
I have a relatively new '21 M50i and can tell you that the power delivery from this engine is absolutely stunning in stock form. Of course many of us always look for more. I'm ready to try the JB4 as there are no available flash tunes for the '21s until it is unlocked or whatever.
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      05-14-2021, 10:18 PM   #3
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lol, its not a 2 stroke with powerband. Constant turbos
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      05-14-2021, 11:24 PM   #4
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higher compression ratio direct injected turbo
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      05-16-2021, 10:10 AM   #5
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I had an old 300ZX Turbo back in the day that would lag terribly and then "kick in" like the old four barrel carburetor with mechanical secondaries would do.
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      05-20-2021, 02:24 PM   #6
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I only feel a little lag if I punch it from a stop, especially a rolling one. I didn't notice this that much with my X5 40i.
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      05-22-2021, 12:35 AM   #7
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Today's turbos are smaller with less inertia, and the intake and exhaust valves are specially configured to bring the turbos up to speed quite fast and at a low RPM. If you look at the torque curve, it builds at a fairly low RPM, and is much flatter than turbos of old that took awhile to come up to speed, then kicked you in the butt. This makes handling and efficiency better since things are smoother.
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      06-10-2021, 08:50 PM   #8
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OP does have a point. I have a highly modified twin turbo 3000GT VR-4 that has a half second turbo lag when accelerating, where it kicks in and snaps your neck with power.

I guess it hadn't crossed my mind, but yes, my M50i has almost instant power. The changes you guys are talking about must be really well done to eliminate this lag.
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      06-11-2021, 10:29 PM   #9
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Quote:
Originally Posted by Wild Blue View Post
OP does have a point. I have a highly modified twin turbo 3000GT VR-4 that has a half second turbo lag when accelerating, where it kicks in and snaps your neck with power.

I guess it hadn't crossed my mind, but yes, my M50i has almost instant power. The changes you guys are talking about must be really well done to eliminate this lag.
I also have a 3000GT Spyder VR4 with DR650s and it might have a bit of lag but seems as fast as my M50i.
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      06-12-2021, 03:44 PM   #10
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Engineers have spent decades perfecting turbo engines to eliminate lag. OP wants it back.
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      06-13-2021, 07:28 AM   #11
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Quote:
Originally Posted by todd92 View Post
Engineers have spent decades perfecting turbo engines to eliminate lag. OP wants it back.
They have made profound progress in that arena. The turbocharged vehicles I owned years ago like the old 90s era 300ZX twin turbos etc. really sucked with a huge lag prior to the forced induction having an effect on power delivery.
Fast forward to 2021, take a BMW X5 M50i for a spin, turbo lag nonexistent.
I gave up on the Asian tin cans 25 years ago, don't know if they have solved the turbo lag problem in their vehicles or not. The Germans seem to have nailed it. These engineering solutions shouldn't be that difficult for Hyundai, Kia, Subaru, and the like to copy.
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      10-14-2021, 10:51 PM   #12
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Ya, the design of these turbo engines was specifically done to reduce any sort of turbo lag. The "hot-V" design almost all but eliminates any pre-turbo exhaust tubing. The turbos are basically bolted to the exhaust ports (on top of the engine) with 2-3" of total tubing between the exhaust ports and turbo inlet.

Because of the small volume of exhaust piping pre-turbo, this helps spool up the turbos very quickly. This is basically the best way to design a turbo engine if no lag is your goal
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      10-18-2021, 09:19 PM   #13
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Quote:
Originally Posted by fstezaws View Post
Ya, the design of these turbo engines was specifically done to reduce any sort of turbo lag. The "hot-V" design almost all but eliminates any pre-turbo exhaust tubing. The turbos are basically bolted to the exhaust ports (on top of the engine) with 2-3" of total tubing between the exhaust ports and turbo inlet.

Because of the small volume of exhaust piping pre-turbo, this helps spool up the turbos very quickly. This is basically the best way to design a turbo engine if no lag is your goal
Are the two turbos twin scroll as well?
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      10-19-2021, 05:58 PM   #14
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I had a 2002 WRX, the lag in that was something else. I currently drive an Ascent while I wait for my X5M50i to arrive. That has almost no lag at all. Turbo tech has come such a long way the past 20-30 years.
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      10-20-2021, 12:45 PM   #15
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Twin-scrolls, variable geometry, better/shorter manifolds, etc., mean that modern turbo-charged engines are much more tractable than they once were. My '82 Saab 900 Turbo was a blast to drive in Colorado's mountains, but you did have to learn how to drive it w/o getting hit by the rather massive turbo lag. The M50i? Really can't notice it at all.
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      11-12-2021, 08:50 AM   #16
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Quote:
Originally Posted by Chick Webb View Post
Twin-scrolls, variable geometry, better/shorter manifolds, etc., mean that modern turbo-charged engines are much more tractable than they once were. My '82 Saab 900 Turbo was a blast to drive in Colorado's mountains, but you did have to learn how to drive it w/o getting hit by the rather massive turbo lag. The M50i? Really can't notice it at all.
It's also blow back turbo so shots through exhaust instead of blow off turbos constantly spool you can here blow back out exhaust not much lag after 3000 in sport plus with gear shift in s.
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