135i: N54 vs N55 - My Humble Opinion

[squeedle]

I don't want to start a war, but I did want to just share my experience after doing a ton of research on these two engines and the disconnect between what I read and what I felt this weekend during several test-drives.

On paper these engines are basically the same. And we've all read the usual threads highlighting differences (reliability vs moddability, etc.). And as far as transmissions, the usual sentiment is that DCT is the more "performance-oriented" compared to the steptronic. But as far as my personal experience, the N54 cars are DRAMATICALLY more fun, more "urgent", and less laggy.

A couple months back I test-drove my first 135i, an N54. It totally blew me away, and I couldn't stop smiling. After that I knew I wanted a 135i, so I started researching feverishly. That led me to decide I definitely wanted an N55, due to reliability and slightly better mileage, and DCT (I love the DCT in my Jetta).

So on Saturday, I went to test-drive an N55, expecting an identical experience to my last test-drive. But it wasn't. The car flies after it gets going, but I felt like I had to wait for it to get on the same page as me. At first I dismissed my experience as user error, or misremembering that N54 test-drive. Or wondered if the N55 I test-drove was perhaps not running at 100%.

So I decided to drive as many 135's as I could on Sunday to settle the issue for myself. I drove 3 N55's and one more N54. And damn if the results weren't identical. The N55's felt really fun, but not in the same ballpark as the N54. The N54 was just, "I need to own this car right now.".

Anyway, suffice it to say I'm set on buying an N54 now, "reliability" issues be damned. And I hope I haven't offended anyone. This is just my opinion. I wanted to share it with the Internet in case someone else finds this useful. Moral of the story: go test-drive these things. All the advice in the world can't compare to 5 minutes behind the wheel yourself.

[The Wind Breezes]

Just to get this straight you've never owned either car, "test drove" some stock unmodified cars and think there's a big difference between stock tune N54 and N55 motors? lol...

N54 can make a lot more power tuned without upgrading the turbocharging, but didn't come with a badass semi auto trans. Also, this topic and pretty much every variation on it you can imagine has already been discussed to death.

[squeedle]

Thank you for your thoughtful and considered reply. You are wonderful.

[Esteban]

Owned an '08 N54 135i with the Steptronic and currently own an '11 N55 135i with the DCT. Only difference I really noticed was the DCT shifted faster and the N55 sounded better. The '11 is not totally stock now but was when I bought it. Bought both cars new btw.

[squeedle]

Yes, the DCT is fantastic (and 7th gear is nice for fwy cruising). And agreed, the N55 DEFINITELY sounded a lot cooler. I forgot to mention that, glad you reminded me!

[Esteban]

My DCT works fine but some people find them a little 'glitchy'.

[c1pher]

I am not aware of any delay on my 135is with DCT. I'm wondering if most of these cars needed their ECUs to adjust. A lot of cars at dealerships just sit.

N54 is easier to get more power. However, in my experience, this extra power probably causes you to have to upgrade a lot of other things to either put the power down or address reliability issues that become exacerbated due to adding moar powa.

[Cavpilot2k]

Everyone has different experiences and priorities, but the key is that you did the smart thing. You tried them for yourself and made the decision that suits you best, and nobody can tell you what that is but you.

Welcome (soon) to the family.

[Dylanize]

The lag is from the DCT not the engine.

[MightyMouseTech]

Originally Posted by squeedle

On paper these engines are basically the same.

Not even remotely! They are very, very different. N54 uses a throttle body, on the N55 all throttle control is done by the Valvetronic system at the valves, so no throttle body. This also means two vacuum pumps inside the valve train. Different style of fuel injectors as well.l

[Dylanize]

Originally Posted by MightyMouseTech

Not even remotely! They are very, very different. N54 uses a throttle body, on the N55 all throttle control is done by the Valvetronic system at the valves, so no throttle body. This also means two vacuum pumps inside the valve train. Different style of fuel injectors as well.l

LOL.

The N55 definitely has throttle body, however you are right that basically all throttle control is done through valvetronic. The throttle body essentially is a fail safe, it's usually either wide open or fully shut.

[MightyMouseTech]

Originally Posted by Dylanize

LOL.

The N55 definitely has throttle body, however you are right that basically all throttle control is done through valvetronic. The throttle body essentially is a fail safe, it's usually either wide open or fully shut.

Yes, just there as a fail safe, does not do anything in normal driving.

[squeedle]

Originally Posted by MightyMouseTech

Not even remotely! They are very, very different.

Sorry, just meant in terms of torque and hp, and I6, etc. Trying to keep things brief and it backfired.

[squeedle]

Originally Posted by Dylanize

The lag is from the DCT not the engine.

Then that would make it even harder to "tune" out, yes?

[MightyMouseTech]

Originally Posted by squeedle

Sorry, just meant in terms of torque and hp, and I6, etc. Trying to keep things brief and it backfired.

Ah, OK. Carry on.

[VRG_135]

Originally Posted by squeedle

I don't want to start a war, but I did want to just share my experience after doing a ton of research on these two engines and the disconnect between what I read and what I felt this weekend during several test-drives.
.
Anyway, suffice it to say I'm set on buying an N54 now, "reliability" issues be damned. And I hope I haven't offended anyone. This is just my opinion. I wanted to share it with the Internet in case someone else finds this useful. Moral of the story: go test-drive these things. All the advice in the world can't compare to 5 minutes behind the wheel yourself.

.

[squeedle]

^ LOL, I tried to include as many disclaimers as I could, but you may be right.

[atr_hugo]

Had both an '08 135i w/ N54 and now a '13 135i w/ N55 - the folks here have got it right on the money. Both cars I own(ed) have manual transmissions. Here's my take on differences:

- N54 had partial throttle engine braking, the N55 only closes it's 'throttle' when your foot is completely off the accelerator - had to figure that out when going downhill on the east side of Trail Ridge Road ; -)

- The single turbo on the N55 is getting an exhaust pulse every 120 degrees of engine rotation, the two turbos in the N54 receive an exhaust pulse every 240 degrees of engine rotation - the N55 'feels' like it is smoother in acceleration to me, almost like what I've experienced with a V-12

- BMW adjusted the exhaust note after the '08 model, the '13 N55 has a nice snap, crackle, and pop to it that the '08 didn't

- The differences are subtle and, from my perspective, revolve around the Valvetronic and single vs two turbos

[VRG_135]

I was very lucky. I really wanted a 2009 135 convertible. And it had to be auto (wife can't drive a stick). Fell through. Found a coupe in Houston, drove down to buy it, that fell through. Gave up. Then by pure dumb luck find the car I currently have on a Toyota used car lot. I think the DCT is much more enjoyable to drive (after the 12-15-14 (?)0 treatment. But I think either of these cars are a total blast with a stick.

[davis449]

Originally Posted by atr_hugo

Had both an '08 135i w/ N54 and now a '13 135i w/ N55 - the folks here have got it right on the money. Both cars I own(ed) have manual transmissions. Here's my take on differences:

- N54 had partial throttle engine braking, the N55 only closes it's 'throttle' when your foot is completely off the accelerator - had to figure that out when going downhill on the east side of Trail Ridge Road ; -)

- The single turbo on the N55 is getting an exhaust pulse every 120 degrees of engine rotation, the two turbos in the N54 receive an exhaust pulse every 240 degrees of engine rotation - the N55 'feels' like it is smoother in acceleration to me, almost like what I've experienced with a V-12

- BMW adjusted the exhaust note after the '08 model, the '13 N55 has a nice snap, crackle, and pop to it that the '08 didn't

- The differences are subtle and, from my perspective, revolve around the Valvetronic and single vs two turbos

This is exactly my evaluation N54 vs. N55 and I had DCT in my former '12 135i and now on the 2016 Z4. The N55 had a, IMHO, better exhaust note both pre and post PPK1. We'll see how I feel after tuning the N54.

[Esteban]

Originally Posted by Dylanize

The lag is from the DCT not the engine.

These cars are turbocharged so they all have some turbo lag. Personally, don't really notice any more lag from the DCT than I did in the Steptronic.

[c1pher]

I don't really feel much if any lag at all either due to the motor or the DCT. And the DCT is very good in sport or manual mode, shifting very quickly.