Anthony
Sharing an interesting piece of journalism with a few engine facts.
At the local Canberra hillclimb track we have a guy with a AMG GLA45 but he struggles against a 242GT T, but he dosen't want to bin it either.
From a Road and Track web review - 'Five door Fury' by Jason Camisa: extracts
since the AMG engine is but a pip-squeak in a parking lot of giants. At 1991 cc, the GLA45's four-cylinder is only 193 cc larger than the engine in a Toyota Prius, yet it makes 1 hp more than Audi's quad-cam, direct-injected, supercharged V6 masterpiece.
To produce that much power, the Mercedes mill is, of course, turbocharged to pressures typically reserved for radial tires. The GLA's intake manifold is stuffed with 26.1 psi of boost, one and a half times as much as the Porsche engine.
To keep it all together, AMG engineers had to lower the compression ratio to a scant 8.6:1, a recipe for massive turbo lag. Indeed, there's a whole lot of nothing happening under the GLA's hood when the turbo's asleep. What's more, the Mercedes seven-speed dual-clutch automatic often naps on the job. Stab the gas pedal at rolling-through-a-stop-sign speed, and you'll be met with nothing. Zero. Zilch.
For several seconds, as you crawl through an intersection with your foot on the floor, your 355-hp, AMG-powered, fire-breathing hot hatch will be stone-cold dead to the world. Sigh.
But watch out when the little AMG engine wakes up, because the Mercedes acts like it's got a Taser to the groin. With commensurate anger spewing from the tailpipe, the GLA45 barks and spits and sounds like it's in the World Rally Championship.
Sudden throttle lifts result in endlessly satisfying wizza-wizza-wizzy noises as the twin-scroll turbo blows off steam, and after full-throttle upshifts, the exhaust explosion so accurately replicates a .22 gunshot, someone might call 9-1-1 on you.
"The GLA is a riot—one of the most agile cars I've ever driven," says Webster, "but I couldn't live with it. It's too juvenile." We loved it anyway. Juvenile might not be what you expect from a Mercedes, but having fun is the whole point of driving a hot hatch, ...
Chris
Hmmm but it's only fun if you get up it otherwise it's a slug. Sounds like the old school 80s turbos that behaved very much like this. There was a reason things changed - because the on/off switch school of motoring is too hard to live with. That's something I gave kudos to my old Astra Turbo for - smooth, linear. flexible, muscular. Shame about the torque steer though.
VolvoMike
Click on the Technical tab for the new Polestar 4 cylinder at
https://www.polestar.com/intl/products/engineered/ 2.0 Bar boost.
Regards,
Michael
Vee_Que
Gla is the raised pseudo SUV thing, not exactly the best of the range, that's the a45. Vw run similar boost pressures on the golf r, but with much more compression. I've not read about the turbo lag on them before either.
cubic25
I've always wondered about the longevity of those Merc engines. I'm sure, being a Merc, they are engineered to cop all the boost that the turbo can pump out, but 300kw seems nuts on a 2L road car.
deleted_user_160
Moved to non Volvo
Oh and this.
From my Passat tdi.
Vee_Que
But that includes base pressure of wherever you are, so if you are at sea level, 14.8 is the base.
deleted_user_160
We think. I'm yet to have that confirmed. Even by vw tech.
Vee_Que
Vw techs will only know if given paperwork in training on a new motor.
The fact is, at idle it is at 14.7, it's not making that boost. It's the map sensor. It's why you need a 2 bar or 3 bar unit for a turbo car. The first bar is atmosphere.
deleted_user_160
Yes it's likely boost pressure is read via the map. Even 25psi. Indecent from a factory new car.
Though I dare say we will see this become common place. With the ability of the ecm to control ignition and cam timing, fueling etc so well. We can now run higher static compression and more boost that we formally couldn't.
Vee_Que
Diesels run lower compression than they used to actually.
deleted_user_160
I was referring to the whole thread.
Higher comp more boost
sucksqueezebangblow
If only new cars were all flex fuel though!
deleted_user_160
Some are. Holden did it there for a while.
I'm not a huge fan, until the consistency and more readily available e85 option is there.
Forg
Yeah our Redline is flex, but I've never actually pulled into a servo with E85 (and you need a few fills to clear out the tank anyway) so my curiosity has never been sated.
Ignoring the performance of the A45, GLA45 (erk!) and CLA45 ... they sound like arse. They really do. The first time I heard an A250 (which sound much the same) I thought it must've been a diesel or something, sounded shocking ... and the higher-performance version sounds the same while dribbling around and like a stock 1.5L SOHC Lancer/Mirage with a 5" exhaust when being pushed.
cubic25
Forg;106337 wrotethey sound like arse.
Couldn't agree more. They sound like a wet fart.
Anthony
cubic25;106339 wroteForg;106337 wrotethey sound like arse.
Couldn't agree more. They sound like a wet fart.
And to the jerk in my neighbourhood in the VW Golf who somehow disconnected a muffler (or amplified) the sound of the farts as it changes gear with the DSG - its worse that a wet fart and total noise pollution.
Chris
+ 1 I can't believe how rubbish they sound. What were they thinking? Like an old Excel with a fart cannon on the back. And yeah, the Golf owners who still think the DSG fart is cool - not really, half the cars on the planet have been tuned or modded to do it so now it's just noise pollution.
God I miss the days of a nice system, like the old Alphas
Vee_Que
BMW's don't sound that great.. .
They all run the same firing order, same as an sr20, that's what they sound like. Lucky Anthony doesn't live near a uni in Melbourne, plenty of golf r's and such around... .
Philia_Bear
Vee_Que;106345 wroteBMW's don't sound that great.. .
They all run the same firing order, same as an sr20, that's what they sound like. Lucky Anthony doesn't live near a uni in Melbourne, plenty of golf r's and such around... .
My i6 with strait pipe off the turbo sounds fantastic
Its just the new 4's that sound blech
