23i vs 30i.. or 4 pot?
- Thread starter mr.tourette
- Start date
North West Surrey
I think when people say they prefer the torque of a larger engine they often mean they prefer the response at low RPM.
Turbo engines produce way more torque but only once the turbos are spinning. Modern turbo engine spool up fast but still have a noticeable transition at lower revs. A 20i might have a higher torque figure on paper than a 30i but the 30i is going to pull away at low revs more effortlessly.
There's no escaping the fact that turbocharging comes at the cost of drivability especially in small engined vehicles. The 35i does a good job of masking it with the extra displacement but it's still there.
Turbo engines produce way more torque but only once the turbos are spinning. Modern turbo engine spool up fast but still have a noticeable transition at lower revs. A 20i might have a higher torque figure on paper than a 30i but the 30i is going to pull away at low revs more effortlessly.
There's no escaping the fact that turbocharging comes at the cost of drivability especially in small engined vehicles. The 35i does a good job of masking it with the extra displacement but it's still there.
Maybe that is why I like them so much.
Wasn't there a TV advert for the E36 320i where they stood a 50p coin on it's side on top of a running engine to make that point? At a time when all their competitors' 2 litre cars had 4 cylinder engines!
Wasn't there a TV advert for the E36 320i where they stood a 50p coin on it's side on top of a running engine to make that point? At a time when all their competitors' 2 litre cars had 4 cylinder engines!
Pbondar makes some great points for the 4 pot. It's lighter, it makes more low end power, it more efficient. All those stupid things :evil:
I got the N52 powered E89 because I wanted a classic BMW roadster with modern comfort and reliability. BMW has made 6 pots for 100 years. And that was the engine they were famous for. So I chose that one for better or worse......actually it sounds and drives lovely.
I got the N52 powered E89 because I wanted a classic BMW roadster with modern comfort and reliability. BMW has made 6 pots for 100 years. And that was the engine they were famous for. So I chose that one for better or worse......actually it sounds and drives lovely.
Pbondar said:
In the lower - mid-range that assumes the turbo has spun up.
Economy and emissions are the priority.
Little 1.0 litre buzzy turbo engines exist mainly for that reason in hatches and saloons.
And then the manufacturers like to play games with the same basic engine and provide a different mapping and turbo to create the different models in the range.
Dryce said:
Twin scroll turbo on the n20, there's virtually no lag when you put your foot down.
Manufacturers have played similar games with na engines for decades, creating different models with bigger carbs & hotter cams etc to bump up the power from the same basic engine, nothing new there.
Rob
Smartbear said:
There's two parts to any delay with turbos, there's the initial lag between pushing the accelerator and getting a response then there's the spool time. You might feel the car start to move after a small delay when pressing the accelerator but it takes time for the turbos to build full boost pressure and that delay is much longer at low RPM.
It's just one of the few disadvantages of a turbo charged engine. Some manufacturers have compressed air systems that reduce the spool time and others use a small electric turbo to fill this torque gap but these are not utilised on either the N20 or N54.
I think the upsides of turbo chargers more than outweigh the few disadvantages but you can't pretend they don't exist.
Purity
/\
|..................6cyl NA
|
|....................................V8 NA
|.........................................6cyl Turbo
|
|...............................................................V8 Turbo
|......4cyl NA
|
|.......................4cyl turbo
|____________________________________________ > Performance
Thats my take on it! :lol:
i'll admit, a 4cyl turbo has more performance than a 6 cyl NA, but i value purity (/smoothness, sound) quite highly for a roadster/sportscar, so i'd go 6cyl NA every time.
ask me to choose between a V8 NA and a 6cyl (twin) turbo though, thats a far harder decision!
/\
|..................6cyl NA
|
|....................................V8 NA
|.........................................6cyl Turbo
|
|...............................................................V8 Turbo
|......4cyl NA
|
|.......................4cyl turbo
|____________________________________________ > Performance
Thats my take on it! :lol:
i'll admit, a 4cyl turbo has more performance than a 6 cyl NA, but i value purity (/smoothness, sound) quite highly for a roadster/sportscar, so i'd go 6cyl NA every time.
ask me to choose between a V8 NA and a 6cyl (twin) turbo though, thats a far harder decision!
A
Anonymous
Guest
brillomaster said:
That's a good articulation..one may debate the length of the lines and your sort order..are you a management consultant?
ha, not quite, project analyst! but we do love a graph!
Attleborough, Norfolk
brillomaster said:
I see you include smoothness in your 'purity' requirement. Would a V8 therefore not be better, given every pulse is balanced by another, and on a shorter crank?
But then I guess we'd need to build a Flat 8 to make it even better.
Or maybe the final solution..............the flat 16 1500cc F1 engine they have on display at Donington. (Can't remember the make, but pistons the size of egg cups!)
So this argument about 4 pot turbo or 6 pot NA continues and probably forever will LOL 
My F20 was a twin scroll turbo motor and I could definitely feel a bit of lag before the turbo spooled up. I don't have anything against turbos, my WRX and Supra were both turbos and they were great even with a bit of lag. But when you have the option of having a glorious BMW 6 cylinder under the bonnet / hood of an open top sports car why would you have a 4 pot?
For me if it wasn't for being concerned about the future repair costs on the 35i / 35is I would bought one of those but since I wanted a hassle free ownership experience I got the N52 3.0, either way it had to be a 6 pot. The 6 pot just sounds fantastic and befitting this type of car, even more so with the hood down!
BMW were forced to ditch the NA 6 pots purely to appease the EU / US legislators demanding ever stricter emissions standards and on paper the N20 also shows way better fuel consumption than the N52 but in reality I bet the difference in fuel consumption between them isn't huge. Quite often these new small capacity turbos fail to come anywhere close to published MPG figures, I know my F20 didn't come anywhere near what BMW said it will do. Anyway we don't buy a sport car for economy now do we? If the bureaucrats didn't interfere I bet BMW would still be churning out NA 6 pots to accompany their turbo sixes.
Not saying I would never choose a N20, it has it's place perhaps in a 1 series or 3 series runaround but in an open top sports car even a 5 or 7 series no thanks!
It is a shame BMW didn't fit the N55 which known to be more reliable in the later years of the E89, if they did I would probably have got that. Now I wonder if I could transplant a B58 into my E89.
All of the above is just my 2 cents mind!
My F20 was a twin scroll turbo motor and I could definitely feel a bit of lag before the turbo spooled up. I don't have anything against turbos, my WRX and Supra were both turbos and they were great even with a bit of lag. But when you have the option of having a glorious BMW 6 cylinder under the bonnet / hood of an open top sports car why would you have a 4 pot?
For me if it wasn't for being concerned about the future repair costs on the 35i / 35is I would bought one of those but since I wanted a hassle free ownership experience I got the N52 3.0, either way it had to be a 6 pot. The 6 pot just sounds fantastic and befitting this type of car, even more so with the hood down!
BMW were forced to ditch the NA 6 pots purely to appease the EU / US legislators demanding ever stricter emissions standards and on paper the N20 also shows way better fuel consumption than the N52 but in reality I bet the difference in fuel consumption between them isn't huge. Quite often these new small capacity turbos fail to come anywhere close to published MPG figures, I know my F20 didn't come anywhere near what BMW said it will do. Anyway we don't buy a sport car for economy now do we? If the bureaucrats didn't interfere I bet BMW would still be churning out NA 6 pots to accompany their turbo sixes.
Not saying I would never choose a N20, it has it's place perhaps in a 1 series or 3 series runaround but in an open top sports car even a 5 or 7 series no thanks!
It is a shame BMW didn't fit the N55 which known to be more reliable in the later years of the E89, if they did I would probably have got that. Now I wonder if I could transplant a B58 into my E89.
All of the above is just my 2 cents mind!
A
Anonymous
Guest
Germans have a long track record on purity.. aka brewing and the Nazi Party... 
I think the purity logic was based on the primary and secondary balance of a straight six engine vs other configurations..
So a V10 or V12 is not as pure as an inline 6
I think the purity logic was based on the primary and secondary balance of a straight six engine vs other configurations..
So a V10 or V12 is not as pure as an inline 6
montymoore
Member
I think the main advantage of these twin-turbo smaller engines is economy around town as long as you keep the revs down. My 3.0i is pretty poor at low speeds but surprisingly good at around 80mph ( I am getting over 40mpg). I must admit I was keen on the 2.8i but the 3.0i popped up when looking and so went for that at the time. I guess I will never know unless I get to drive a 2.8i for a while.
montymoore said:
The 18/20 & 28i range all use a single turbo (twin scroll), it’s not really revs per se that knacker the fuel economy but rather the load on the engine, they can be more economical by using a lower gear & spinning the engine revs up as opposed to using a higher gear/lower rpm and bringing more turbo boost into play
Rob