Natural Aspiration... a crazy idea?

[NeuroBeaker]

You know, there's something to be said for a naturally aspirated engine - it sounds great and has terrific driving characteristics.

Lohen obviously have their tuned ONE/Cooper package delivering quite a bit of horsepower - but many ONEs and Coopers start to run into the limitations of the car (i.e. gearbox to name but one) when compared to the MCS and trying to seriously up the power. To quote one example of reasons to simply buy the higher-end model:

Quote: Originally Posted by brainycheddar (original)

Not to mention a 5 speed instead of 6, the lack of oil squirters, no inconel exhaust valves, no dished pistons, cast con-rods, etc.etc. etc.

Kinda of like buying a mitsubishi mirage, and trying to make the power of an evo.

No dice

Although, I wonder if anyone has ever thought to take a 163bhp MINI Cooper S and convert it into a Naturally Aspirated engine of similar power? Hypothetically, how might it be done and would the end result be spectacular to drive or spectacular for all the wrong reasons?

All the best,
Andrew.

[Goonery]

4 DCOE Webers on a water cooled manifold would work, but I did that with my Osellli 1.4 Clubman years ago and it was sweet when it ran, but needed a retune every 500 miles tp get the balance right across all 4 cylinders. Fuel injection is the way to go unless you want a home tuneable engine.

[MarkW]

throttle bodies should about do it with a cam

[MINIMANIAUK]

The internals of the S engine are uprated to cope with the extra torque and the extra temp -all provided by the charger -
The extra torque gives the extra bhp (torque x rpm)
Once you remove the charger ,there goes the torque - given both engines are the same size its the quantity of air through the engine that gives the torque
no charger then you have to increase the air by another means -hence cylinder heads,valves,intake manifolds ,throttle bodies,exhaust manifolds , even then the air is not the same as a charger so the torque is always down -this means that the rpm must be raised to provide the same power as the charged car (torque x rpm)
This proves to be an expensive exercise as so many components need uprating and adding ,so yes you have a strong enough block and internals but it still costs to add all the other bits and will end up more expensive that simply buying an S in the first place
However if there is a reason that the car must be NA like the class of racing or rules dictate then using the s block and internals is the cheapest way to go

[NeuroBeaker]

Quote: Originally Posted by Goonery (original)

4 DCOE Webers on a water cooled manifold would work, but I did that with my Osellli 1.4 Clubman years ago and it was sweet when it ran, but needed a retune every 500 miles tp get the balance right across all 4 cylinders. Fuel injection is the way to go unless you want a home tuneable engine.

So, perhaps the reliability of the engine would be impacted going down this route?

Quote: Originally Posted by MarkW (original)

throttle bodies should about do it with a cam

Throttle bodies... plural? Like, one for every cylinder? I can only imagine how that'd sound...

Quote: Originally Posted by MINIMANIAUK (original)

The internals of the S engine are uprated to cope with the extra torque and the extra temp -all provided by the charger -
The extra torque gives the extra bhp (torque x rpm)
Once you remove the charger ,there goes the torque - given both engines are the same size its the quantity of air through the engine that gives the torque
no charger then you have to increase the air by another means -hence cylinder heads,valves,intake manifolds ,throttle bodies,exhaust manifolds , even then the air is not the same as a charger so the torque is always down -this means that the rpm must be raised to provide the same power as the charged car (torque x rpm)

Do you think an S engine without a supercharger could be raised to higher RPM to achieve this? If you sorted out all the air going in (throttle bodies, etc) and the air going out (exhausts, etc) then what else would need to be done to ensure the engine runs reliably at a greatly increased RPM?

I note at this point that Ferrari engines (like the naturally aspirated 355) sound great above 9,000 RPM.

Quote: Originally Posted by MINIMANIAUK (original)

This proves to be an expensive exercise as so many components need uprating and adding ,so yes you have a strong enough block and internals but it still costs to add all the other bits and will end up more expensive that simply buying an S in the first place

Well... in our hypothetical scenario, we're starting with an S and then removing the supercharger. So presumably there would be heavy-duty internals in the engine to start with, right? As it's not at such a high compression ratio anymore, surely there's less of a problem at higher RPMs than were intended when the supercharger was present?

Quote: Originally Posted by MINIMANIAUK (original)

However if there is a reason that the car must be NA like the class of racing or rules dictate then using the s block and internals is the cheapest way to go

More as a flight of fancy in thinking about a very responsive engine that won't suffer the surges of a supercharger, or lag of a turbo. Plus, naturally aspirated engines sound great - forced induction noises are nice too but they cover up the sound of combustion to some extent.

[MarkW]

I use suzuki gsxr throttle bodies, 1 per cylinder, on my track car and yes they sound awesome

instead of down tuning a s would tuning the cooper lump be better? just thinking compression ratios need to be higher for n/a.

[Goonery]

The beauty of a supercharger is that it does not surge like a turbo. The charger runs pretty much at a constant boost pressure even at lowish revs and power delivery is linear right up the rev range.

No reason why a supercharger would not work with a carburated fuel/air delivery system either, its just that injection systems are metered and deliver just the right charge for the load, temperature and atmospheric conditions compared to a carburated system which wont constantly adjust dependent on the ambient conditions etc.

[MINIMANIAUK]

The ONE/COOPER engine came out first and in order to increased the power output BMW elected to go with the charger and strengthen and cool things to produce the S

Given the base ONE/COOPER engine in order to cost effectively increase the power you would end up with .....................a COOPER S !!

You can always work against the simple logic and create an NA cooper with more power ,but it will always cost far more to do -possible but expensive, and will have to run at far higher RPMs thus costing even more
A 50 % uplift in power from an NA engine is always going to be dear ,and in reality there is no market for it

[MarkW]

big expense would only come if your changing c/r surely

Lohen reckon 150bhp+ on their one but still on single tb and a bluefin map, imho itb's and a mappable ecu would easily see mcs power levels. The sound would be awesome but economy may not be

[NeuroBeaker]

Quote: Originally Posted by MarkW (original)

I use suzuki gsxr throttle bodies, 1 per cylinder, on my track car and yes they sound awesome

instead of down tuning a s would tuning the cooper lump be better? just thinking compression ratios need to be higher for n/a.

Any videos or sound clips of that track car?

Well, the thinking was that the R53 engine has uprated components in comparison to the R50 engine. So I assumed that it would be a better starting point and cheaper to get to a reliable, high HP, high torque NA engine in comparison to starting with the base R50 engine.

Quote: Originally Posted by Goonery (original)

The beauty of a supercharger is that it does not surge like a turbo. The charger runs pretty much at a constant boost pressure even at lowish revs and power delivery is linear right up the rev range.

I've heard some S owners say that at low speeds the supercharger can make it a little difficult to drive smoothly without a sudden delivery of power in say... a car park or similar scenario. Though, I've not driven an R53 myself.

Quote: Originally Posted by Goonery (original)

No reason why a supercharger would not work with a carburated fuel/air delivery system either, its just that injection systems are metered and deliver just the right charge for the load, temperature and atmospheric conditions compared to a carburated system which wont constantly adjust dependent on the ambient conditions etc.

I'm afraid I don't really know what a carburettor fuel/air delivery system is... Help?

Quote: Originally Posted by MINIMANIAUK (original)

The ONE/COOPER engine came out first and in order to increased the power output BMW elected to go with the charger and strengthen and cool things to produce the S

Given the base ONE/COOPER engine in order to cost effectively increase the power you would end up with .....................a COOPER S !!

You can always work against the simple logic and create an NA cooper with more power ,but it will always cost far more to do -possible but expensive, and will have to run at far higher RPMs thus costing even more
A 50 % uplift in power from an NA engine is always going to be dear ,and in reality there is no market for it

We're not discussing tuning an R50 engine to the levels of R53 output.

We're musing ways (independent throttle bodies, raised rev limit, etc...) that an R53 engine could retain its performance once the supercharger is removed. It's still an R53 engine, but now without forced induction.

The difference here is that when starting with the R53 engine, it contains some uprated components that you won't have to purchase aftermarket for the R50 engine. Thus, even though its more expensive to buy in the long-run, it might be cheaper to tune as a high-performance naturally aspirated engine.

Quote: Originally Posted by MarkW (original)

big expense would only come if your changing c/r surely

Lohen reckon 150bhp+ on their one but still on single tb and a bluefin map, imho itb's and a mappable ecu would easily see mcs power levels. The sound would be awesome but economy may not be

What does "c/r" stand for?

Hehehe... I don't think economy would be a major consideration if anyone should undertake a problem like this.

[MarkW]

c/r = compression ratio, forced induction generally runs a lower cr than NA so if you were using a mcs engine you'd need to raise it with different pistons afaik.

best vid I've got when the itbs were first fitted, it's since been blown up and rebuilt
TBs 49 - Putfile.com

[NeuroBeaker]

Quote: Originally Posted by MarkW (original)

c/r = compression ratio, forced induction generally runs a lower cr than NA so if you were using a mcs engine you'd need to raise it with different pistons afaik.

Ooh , that surprises me - I had assumed a forced induction engine ran a higher compression ratio.

[MINI-Morgan]

oh god why would you want to??? its a load of money to get less performance....

[MINI-Morgan]

Quote: Originally Posted by NeuroBeaker (original)

Ooh , that surprises me - I had assumed a forced induction engine ran a higher compression ratio.

lower compression pistons but higher final compression due to the charge pressure. NA you'd have to put in high compression pistons or it will be rubbish.

[brainycheddar]

at high rpm things might start to rattle, remember the design is loosely based off a dodge neon, not the honda s2000. even then the s2000 barely breaks the 1hp/10cc border. and that revs to 8000+ rpm!!