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      09-08-2012, 07:13 PM   #100
RPM90
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Drives: 335i Msport w/sport AT
Join Date: Mar 2006
Location: Chicago

Posts: 6,095
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Quote:
Originally Posted by MaestroAl View Post
Mine's modified Also, the characteristics are that the MPS has an enormous surge of torque and "feels" liek aproper turbo car. You know how they build ... it's like a mountain of torque coming in to around 2500rpm and then there's this big hump up to 4500 rpm-ish before it tapers off after around 5500rpm. I hit around 360ftlbs at 3000rpm. BMW tuned the 335i so that it doesn't feel ilke a forced induction car but just feels like a straight six - the torque curve isn't a curve, it's a straight line. Yes, it's more refined and yes, it's more "BMW" but ... in my opinion ... it's got less character and needs to be worked harder to feel as quick.

It's just a perception thing based on how it's been tuned. I don't think anyone disputes that the 335i is a great car, it's quick and it's refined. It just doesn't feel as quick as it is unless you wind the nuts off it
That's one aspect of older turbo engines that I really love, the way the torque all of a sudden slams you back in your seat.
It feels massive because there's little torque at lower rpm until the revs build and the turbo spools and it's off to the races.
I had a new 1990 Plymouth/Mits Laser/Eclipse FWD 5spd.
I modded it with a 16G turbo and upped boost. Off the line you had to have a firm grip on the wheel as it wasn't the AWD model.
But, at speed around 60, drop the gears and slam the loud pedal that thing would leap like a scalded cat.
The other great aspect was that it would pull all the way to red line, and there was still a lot of torque there, but, red line.

Modern turbo's are different. With the addition of direct injection, these engines can now run higher compression ratio's unheard of in the old turbo days. With the higher compression ratio's smaller turbo's make sense, as the engine can still naturally develop good low rpm torque, and the smaller turbo's can spool so much quicker to add to that low rpm torque.
Add variable valve timing and how you have a torque "curve" that is flatter, but the table top is very high, and gives you that huge torque for a broad rev range.

The thing I wish manufacturers of "sport/sporty" turbo's would do is retune these engines so that they don't build all their torque at such low rpm.
Rather, move the torque curve higher in the rev band, using a bit larger twin scroll turbo's that flow better at higher rpm.
Instead of 300lb ft by 1200rpm, more like 225lb ft at 1200rpm that steadily climb, and perhaps peak around 2500-3000 but running to near red line.
So the curve looks more like a softly rounded balloon.
It would give it more character and allow the driver to enjoy the cacophony or whirly bits at very high rpm.

As it is now, most turbo engines have a diesel like torque output, but it dies too early. Sure, it saves on friction as we get a lot of power without having to rev it up, but again, for a sport/sporty automobile, that's part of the allure and pleasure.

I think I got lucky with my 335i Msport. My engine feels very strong.
It's the strongest feeling N55 of all the 335i's I've tested, which is about 5-6 of them. It even feels stronger than the N54 in my 135i.
I'm quite happy with it.
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