What will come after the 2.4 V8?

[xpensive]

A rather heavy contraption really, 170 kg för a 1.5 I4, wonder what the reasoning for sticking with the stock cast-iron block was?

Marketing perhaps?

[marcush.]

the engine blocks were indeed greycast iron ,BMW standard engine blocks but fully machined and polished inside..

It is no myth that the oldest blocks give best hp and anyways grey car iron blocks are stored to settle in the backyard ,exposed to the elements.. I would not be surprised if Rosches boys were really urinating on the blocks waiting for machining back then.. you know bavarians drink a lot of beer ...and at these times it was surely normal to have a beer or two or three during working hours..i know a guy who worked in the engine preparation in munich during these years of turbo crazy ,maybe i just ask next time I bump into him..

[xpensive]

I wonder what a modern-day 1.5 I4T, mildly boosted with 1 Bar, would be like?

Kinda neat, 650 Hp at 12000 Rpm perhaps, 100 kg with a wide powerband?

[agip]

Do you think just 1 bar of boost will be allowed?

[xpensive]

Do you think just 1 bar of boost will be allowed?

I have no idea, but I needed some even number input data to get a power-figure down.

If a 2.4 produces 760 Hp at 18000 rpm, then a 1.5 should proportionally mean 320 Hp at 12 000 Rpm.

Add a 1 Bar boost and you are at 640 Hp, 2 Bar and you get 960 Hp.

[WhiteBlue]

I think expensiv's figures could be very close to the real thing except for weight. This thing is supposed to have integrated KERS and HERS and is likely to have more than one turbo or an elaborate movable geometry. Generally bi-turbo gives you better chance at a nice and smooth torque curve. If you figure the naked engine at 65-70 kg and you add turbos, HERS and KERS you could come out at 100-110 kg which would be a nice figure. Then you immediately save 40 kg of fuel weight for the better engine efficiency and you look at cars that can be run at a much reduced weight compared to today.

[xpensive]

An important note on the above drafted calculations is to distinguish "boost" from absolute pressure, the 1 Bar boost I used equals of course 2 Bar absolute.

But anyway, in theory, by playing with boost allowance from 1 to 2 Bar, engines could be power-adjusted between 640 and 960 Hp.

[agip]

Just a question... do you think the 2013 turbo cars will sound something like this or im saying something stupid?

[youtube]http://www.youtube.com/watch?v=TwbqRcKFyL4[/youtube]

[xpensive]

In principle yes, depending on a few details, though the muffled note on full song was a little more brutish of course!

[ringo]

Do you think just 1 bar of boost will be allowed?

I have no idea, but I needed some even number input data to get a power-figure down.

If a 2.4 produces 760 Hp at 18000 rpm, then a 1.5 should proportionally mean 320 Hp at 12 000 Rpm.

Add a 1 Bar boost and you are at 640 Hp, 2 Bar and you get 960 Hp.

Why stop at 12,000 rpm for the new engines?
It would be interesting if we see 1800prm turbo engines. 1.5lt with appropriate boost pressures put the power to around 800 to 900.
The 750hp is a bit too slow for me. The V10 days were a real spectacle, you could really sense the speed. Now, the cars seem slouchy through the high speed corners.

[xpensive]

I did not pick 12000 rpm arbitrarily, the BMW I4T of the 80s stopped at 11500 even without an FIA rev-limitation,
why I think it has something to do with the increasaed fuel burning-time of a turbo?

Besides, I guess the higher loads itself puts a natural limitation on speed.

Anyone?

[WhiteBlue]

In general higher engine speed increases the efficiency of an engine but you have to take that with a caveat. The engines also has to achieve a certain life.

The old BMW engine had perhaps 20 km life at 5.5 bar boost pressure and 400 km at 3.5. A modern engine has to achieve 3,000 or 4,000 km. So the comparable boost pressure would have to be more at 2 or 2.5 bar.

The question would also be where the harmonics or eigenfrequencies of the engine would be found in the rev band. You obviously want to run the engine either below or above the eigenfrequency. If we assume that a 1.5L I-4 resonates somewhere at 12,000 rpm you want to make sure you stay below it or you add balance shafts and go to 13,000-16,000 as a usable rev band.

Staying below may have additional advantages. You may be able to run without balance shafts that reduce efficiency and cost weight. You may also have less problems with valves.

NA engines do not have the option to increase the pressure and so their design limit is reached by inertial forces on the con rods and pistons. In turbo engines you have additional stresses from the higher compression and so you have to strike a balance between boost pressure and rpm. This usually means you have lower revs than NA engines.

The new turbos will increase efficiency big time because they will almost certainly have massively lower pumping and throttling losses. I think the engineers will aim at throttle less operation where the power modulation is mainly done by fuel injector, ignition and valve timing with direct, stratified injection and highly variable valves.

[xpensive]

The relation between Rpm and natural frequencies and balancing/harmonics are obviously no different for a turbo- or NA-engine, question was rather if it is possible to run the former at the same xtreme rpm as the latter.

I think not, but my knowledge on the matter is limited, I do have something in the back of my head on fuel-burning though.

[ringo]

I think it can run higher. So much has changed since the 80's in terms of analysis, materials etc.
I see no reason that the 4 cylinder engines can't run at 18,000. The harmonics are an issue, but I'm sure a reasonable engine speed can be targeted where the power is made.
The boost pressure is a concern, but remember most of the stress experienced on a con rod is at the end of the exhaust stroke where the rod is pulled down after tdc.

We also have pneumatic valve trains now, were these around in the peak of the high boost the turbo era?

[alelanza]

If you avoid the throttle all together (for efficiency reasons) you get the full gas flow going through the engine. This is what people want for the blown diffusors.

Hmmm... i definitely have no clue what you're talking about, do you have a link to the source you got this idea from? that may help me.
You can't avoid the throttle, whether you use a plate or valve lift and timing to throttle an engine, you still need to throttle it, otherwise the partial load term wouldn't even exist, you'd be at WOT all the time. Saying you get full gas flow through the engine makes it sound as if you have some magically produced mass flow and that the only thing standing in line between intake and exhaust is the throttle plate, but there's more things, ie the engine itself which after all is the one producing the flow, so i don't see how getting rid of the throttle plate would give you 'full gas flow through the engine'. Care to explain or link?

For other readers. This also makes me think about the vacuum a race engine produces, perhaps someone with engine knowledge may be able to answer this. Given the aggressive cams/huge valve overlap of a racing engine, your vacuum signal is always extremely low, i can only imagine that on an 18k optimized setup it will be minimal. So with this in mind, would you gain anything by using valvetrain as a throttle device on an engine that spends most of its time at full throttle? could you really offset the increased mass and friction (which again BMW hasn't gotten to make sense past 6k rpms) on an F1 application?

Regarding turbo and rpm have a look at the diesels. They make the power from torque which is an option for petrol engines as well. The engineers and the rule makers will have an option if they get the target power of 600 bhp from revs or turbo pressure.

Well all engines make power from torque and rpms, can't have one without the other really.
I'm at a loss as to what you're saying.
In the spirit of finding any results from a topic with the word 'sensible' in its title, you stated 'If you generate 600 bhp with 2/3 of the actual displacement you have turbo pressure reserve to lower rpm'. This was my question, what do you mean by that? or at least, what do you mean by 'turbo pressure reserve'?
Worst case scenario, do you have a link to where you got that idea from?
Are you talking about exhaust gas flow minus wastegate flow?