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Anyone driven a Merc A45s?


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Jul 21, 2022
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Like many others I'm (patiently) waiting for my i4 & aside from watching a few reviews, haven't got any driving experience of what the engine is actually like.
So anyone tried it? Was it any good?
I considered buying one as my 'stand in' until the emira arrives but the 50k+ is a bit rich for my liking, so I bought a cayman instead...
Like many others I'm (patiently) waiting for my i4 & aside from watching a few reviews, haven't got any driving experience of what the engine is actually like.
So anyone tried it? Was it any good?
I considered buying one as my 'stand in' until the emira arrives but the 50k+ is a bit rich for my liking, so I bought a cayman instead...
I sold my 718 Cayman just prior to ordering my I4 on 9th July 2021. I decided I would get A45 untill the I4. However, I couldn't find a A45, dealers had them listed, but in actual fact they were only on paper not actual stock. I got a A35 instead, which has the predessor engine to the M139. What I would say is, the A35 was a excellent car and a far better daily driver to the 718. Considering the engineering and technology within the M139 and the fact it has 116hp more than the A35, the M139 must be a absolute stonker of a power plant.
Modern Mercedes turbo 4 cylinders, including the M139, are characterized by low lag, very good low-end torque, and mediocre redline. The torque curve is programmed to fall as the engine nears redline, so it gives the sensation of a larger displacement normally aspirated engine. It does not build and grow stronger as classic sports cars with small NA engines tend to do, which is what gave those sports cars such endearing qualities at high RPMs. Sure, you can keep the engine on the boil to get the best performance, but it'll be obvious that the engine is stronger at low to mid-band and pulls strongly like a bigger displacement engine. Personally, I think the M139 will feel "larger" than the V6 in the Emira in terms of low to mid-end torque. The two engines will have similar qualities at higher RPMs and any difference you sense will be more due to the different programming of the IPS auto vs DCT-8G transmissions. The M139 has a 7200rpm redline, which is not really that much higher than that of the V6.

Sound-wise, I would be really surprised if the M139 sounds better than the V6. It's just easier to get good sound without the turbo piping.
I went to the Mercedes dealer some time ago and test drove a A35. My daily at that time was a BMW M140i xDrive and I was shocked at how bad the Merc engine was in comparison to the B58 engine. In fact comparison isn‘t even the right word. However with more power it should be a decent powertrain. Lag wasn‘t too bad.
The engine in the A35 isn't really the same thing as what you'll get with an M139 from the 45's... the M260 is (AFAIK) a mass-produced engine with some bolt-ons rather than a hand-built-by-one-person monster.

I'll admit I'm in the same camp of not knowing what the M139 is like to actually live with, but reviews of the A45/s make it seem really appealing in terms of urgency and response, and as Nova says, I'm hoping it feels somewhat like a bigger capacity engine under your foot. I think my only real concerns are a) will it cost me an arm and a leg (or a 6 month wait!) if something goes pop, and b) can they make it sound Better Than a Farting Bees Nest :)
Is a test drive going to give you a reasonable impression of what it'll be like in the Emira? I’m not sure.

The A45S is 4WD and front-engined. In the Emira it's RWD and mid-engined, plus Lotus have modified the intake and exhaust, detuned the power and re-mapped it to give a different torque profile.

If I test drove a Camry I wouldn’t get much idea of what the V6 is like in the Evora or Emira.
I've run an A45S as my daily for the past two-and-a-half years and @Nova has summed up the M139 engine characteristics very well. I came from a fettled 400bhp Golf R and the Merc sure did feel NA by comparison, big-engined and well in excess of it's 2.0 displacement. It actually took me a little while to get used to but I've really come to appreciate the engineering and, mated with the DCT and its quick, rapid fire, gear changes, it's a brilliant combination and quite a unique experience.

How that stands up in its de-tuned state, in a mid-engined, RWD car remains to be seen, but knowing and living with the engine and DCT as I do, I'm in absolutely no doubt that it'll work an absolute treat in the Emira chassis. Indeed I actually think that it's a really, really wise move to offer it with less horses than in the A45S because the AMG sure is reliant upon its 4WD and clutch pack wizardry, plus some sophisticated cooling, to keep the thing planted and under control on MP4S, and reliable when things get hot under the bonnet. The AMG also weighs around 90kg - 100kg more than the Lotus, if manufacturer and internet stats are to be believed, so that'll help balance up any performance deficit. A case of 'less is more' maybe and if, 'more' is required, then the tuning possibilities, on standard internals, are there, assuming that the key OEM ancilleries will be able to support it.

What will be interesting is how the various drive modes, available in the Merc, (comfort, sports/S+, race and individual), will be handled in the Lotus, because they do make a big difference to engine and gearbox characteristics, sound, performance and, indeed, how you want to drive the thing, depending on whether you're commuting in traffic, and want something a little less edgy, or the planets align, the road opens up and you feel like 'turning up the wick.' Obviously the adaptive-suspension options that the A45S offers, won't be present on the Lotus.

IMO, once a finished I4 car gets in to the hands of journalists, the reaction will be palpably more enthusiastic and excitable than has been the case with the 'old-school,' manual V6. Ironically though, it's not for me as I still prefer the engagement of a stick and using my left foot, where my 'weekender' is concerned. If it were my daily, it would be a no-brainer.
Useful insights and I agree it's going to be interesting to see the i4/Emira combination. Lotus staff working on it have been positive about what they've been able to achieve and the "Lotus-ness" they've introduced.

I believe the Drive Modes for the i4 will be the same as the modes Lotus has developed for the V6. It's not just a factor of controlling the engine and gearbox but also integrating that with the dynamic performance management system. The product document for DPM mentions launch control only being available for V6 Auto and i4, so I'm pretty sure this is going to apply to all engine/transmission versions.

Lotus developed their own software for the V6 Auto (IPS) and have been working with AMG on the DCT controller (as well as many other aspects of the i4 Emira implementation).

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