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Area under the graph comparing real world performance of engines
sars said:MACK said:Silverstar said:Whilst that might be true (although what I am getting is pretty much BMW say this engine should give) the point I was getting at is that the difference in running costs between the two isn't huge! It isn't like say the difference between running a 118d and M3 V8. In this case the difference for most people in monetary terms will be so small it will be insignificant to most people. Only if you do mega miles a year may you see any significant savings if that.
I do agree the difference isn't going to be huge but it's there. 20% up on the older i6 engines they replaced is what BMW claim and I think that's probably pretty accurate. Not a game changer for most granted, but if it's your only transport and you do significant annual miles, say 12k a year it works out at circa £5-600pa. Enough to influence some no doubt
As the saying goes, you don’t get something for nothing, to produce the same amount of power you have to burn a similar amount of fuel, regardless of configuration excepting the improvement in efficiency. Whilst turbocharging improves efficiency this is not going to be a 20% improvement, the purpose of downsizing from a six cylinder naturally aspirated to a four cylinder turbocharged engine was in BMW’s drive to lower average co2 levels across the range and nothing more.
Its BMW themselves that claim 20% efficiency gains and from my experience I'm inclined to agree with them on this, after all they should know.
Its worth mention turbocharging alone isn't the only new tech they use on the N20 over the N52. There's a few other features such as Direct Injection and variable valve timing etc all driving efficiency gains. I do agree though that if your driving both flat out, full load/WOT producing max power etc there's not going to be much in it. Its at lower revs, part load/throttle etc you will see an improvement and after all this is where these engines will spend the vast majority of their working life
ronk said:Smartbear said:They should be fine Ron, don’t forget the 28i has an identical engine that’s sold with over 240bhp. Remapping a 20i only adds to that figure by a relatively small amount of around 30bhp or so.
Rob
If the 28i engine with 240bhp is identical, can that be remapped or has the limit of that configuration very reached?
Are 28i owners stuck with the output they’ve got plus the 30bhp or so?
Manufacturers as a general rule always leave a bit of head room with an engine. They do this for a few reasons. Firstly it allow them to offer a power increase on say an LCI model or special edition etc. Secondly it allows for poor fuel quality and servicing. Remappers dont have the same constraints and some of the gains can come from a simple change of fuel grade.
BMW were quite clever with the N20 engine, why design/build three when you can just do one and save a small fortune along the way. Don't get me wrong, they weren't pioneering in this approach, far from it, they and others had been doing it for years. What they did do that was fairly rare was to employ one turbocharger across the range. Its more typical that you might see 3-4 models in a manufacturers lineup but at least the top of tree model would have a bigger turbo or employ two and maybe a few internal tweeks to the engine.
Again as a general rule a remap of stage 1 (no hardware changes) or stage 2 (induction/exhaust/intercooler changes) are deemed pretty safe for road use. It's when you start going beyond this with the likes of turbo changes, new injectors and fuel pumps etc that you usually need to think about engine longevity and uprated internals.
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MACK said:ronk said:Smartbear said:They should be fine Ron, don’t forget the 28i has an identical engine that’s sold with over 240bhp. Remapping a 20i only adds to that figure by a relatively small amount of around 30bhp or so.
Rob
If the 28i engine with 240bhp is identical, can that be remapped or has the limit of that configuration very reached?
Are 28i owners stuck with the output they’ve got plus the 30bhp or so?
Manufacturers as a general rule always leave a bit of head room with an engine. They do this for a few reasons. Firstly it allow them to offer a power increase on say an LCI model or special edition etc. Secondly it allows for poor fuel quality and servicing. Remappers dont have the same constraints and some of the gains can come from a simple change of fuel grade.
BMW were quite clever with the N20 engine, why design/build three when you can just do one and save a small fortune along the way. Don't get me wrong, they weren't pioneering in this approach, far from it, they and others had been doing it for years. What they did do that was fairly rare was to employ one turbocharger across the range. Its more typical that you might see 3-4 models in a manufacturers lineup but at least the top of tree model would have a bigger turbo or employ two and maybe a few internal tweeks to the engine.
Again as a general rule a remap of stage 1 (no hardware changes) or stage 2 (induction/exhaust/intercooler changes) are deemed pretty safe for road use. It's when you start going beyond this with the likes of turbo changes, new injectors and fuel pumps etc that you usually need to think about engine longevity and uprated internals.
I did contemplate going for the bigger turbo..Mitsubsishi do a much higher flow bolt on variant for the N20...but..the advice aggregated was:
1) Get forged rods..Carillo etc about £1000
2) Get forged pistons..again Carillo and others £1000
So with Mr Vanos quoting £3,500 to take the car/strip the engine/put the goodies in/rebuild/refit you're at £6,500 plus a day on the dyno..around £7,500..
Even though I like my car /engine combo..getting another 40-50bhp for £7,500 compared to the first 100bhp for £450 doesn't seem like good value. Its the normal law of diminishing returns.
Although the N20 was very cleverly designed to replace all the engines upto the N54..it wasn't designed to be a tuner's dream, unlike the N54 which enjoyed so much tuner related development.
The open desk cylinder /block design whilst great for cooling is a fundamental architectural limit if you want to push really big numbers on a bhp/litre basis..
Pbondar said:MACK said:ronk said:If the 28i engine with 240bhp is identical, can that be remapped or has the limit of that configuration very reached?
Are 28i owners stuck with the output they’ve got plus the 30bhp or so?
Manufacturers as a general rule always leave a bit of head room with an engine. They do this for a few reasons. Firstly it allow them to offer a power increase on say an LCI model or special edition etc. Secondly it allows for poor fuel quality and servicing. Remappers dont have the same constraints and some of the gains can come from a simple change of fuel grade.
BMW were quite clever with the N20 engine, why design/build three when you can just do one and save a small fortune along the way. Don't get me wrong, they weren't pioneering in this approach, far from it, they and others had been doing it for years. What they did do that was fairly rare was to employ one turbocharger across the range. Its more typical that you might see 3-4 models in a manufacturers lineup but at least the top of tree model would have a bigger turbo or employ two and maybe a few internal tweeks to the engine.
Again as a general rule a remap of stage 1 (no hardware changes) or stage 2 (induction/exhaust/intercooler changes) are deemed pretty safe for road use. It's when you start going beyond this with the likes of turbo changes, new injectors and fuel pumps etc that you usually need to think about engine longevity and uprated internals.
I did contemplate going for the bigger turbo..Mitsubsishi do a much higher flow bolt on variant for the N20...but..the advice aggregated was:
1) Get forged rods..Carillo etc about £1000
2) Get forged pistons..again Carillo and others £1000
So with Mr Vanos quoting £3,500 to take the car/strip the engine/put the goodies in/rebuild/refit you're at £6,500 plus a day on the dyno..around £7,500..
Even though I like my car /engine combo..getting another 40-50bhp for £7,500 compared to the first 100bhp for £450 doesn't seem like good value. Its the normal law of diminishing returns.
Although the N20 was very cleverly designed to replace all the engines upto the N54..it wasn't designed to be a tuner's dream, unlike the N54 which enjoyed so much tuner related development.
The open desk cylinder /block design whilst great for cooling is a fundamental architectural limit if you want to push really big numbers on a bhp/litre basis..
Your right it simply isn't worth the cost/risk. I think the sort of power/performance levels our cars now have with circa 5.x 0-60s is honestly good enough for UK roads. Yes more is always nice and if its a must the obvious and sensible route is the 35i/is.
As you already know, the failures associated with big power N20 cars centre around sustained track use and oil starvation etc. So in reality bolting on the bigger turbo on a road car and you would probably be fine, but I would want to chance it. I'm not sure I buy into their claim that the bigger turbo doesn't create any extra lag either. Personally I'd rather keep the low down response than risk it for an extra 40/50 BHP.