Engine how much BHP bullsh!t???

Anan1

ned78 wrote:

Actually, a lot of modern Turbos are twin scroll Turbos, which have virtually no lag.

I think any turbo will have lag, it's just in the nature of the system. Some are much better than others, but none will have the immediacy of a big NA.

davidclayton

here's the records for bhp per litre on production cars according to WIKI:

* Naturally-aspirated pistonless rotary engine - 140.5 kW (191.1 PS/188.8 hp) /litre - Mazda RX-8 Renesis (184 kW (250 PS/247 hp) JIS 1.3 L)

* Petrol/Gasoline (naturally-aspirated) piston engine - 92.1 kW (125.2 PS/123.7 hp)/litre - 2000 JDM Honda S2000 F20C (184 kW (250 PS/247 hp) JIS 2.0 L I4)

nastysimon

Anan1 wrote:

I think any turbo will have lag, it's just in the nature of the system. Some are much better than others, but none will have the immediacy of a big NA.

Yes, and I wasn't just talking about turbo lag.
Turbo engines have less imediate throttle response than a NA engine. When you jab the throttle, the time between the jab and the engine responding is greater on a Turbo engine than a properly sorted NA one. Similarly, a turbo engine usually takes longer to get to the revs you want when you blip the throttle (for down shifts, etc.).

Of course, some turbo engines are great, it's just that there is no substitute for CCs.

As for NA car engines with the highest specific output there are two better than the S2000 (from Wikipedia):
125hp/Litre - Caterham Seven Superlight R500 VHPD Rover K-Series engine (253.5PS/250bhp 2.0L I4)
168 hp/litre - 2002 Radical Sportscars SR3 (252 hp (184 kW) 1.5 L I4 engine)

Rovi

nastysimon wrote:

Of course, some turbo engines are great, it's just that there is no substitute for CCs.

Of course, plenty of CCs + turbos = a good thing

JHMEG

nastysimon wrote:

Not exactly. A petrol engine can have just as long a stroke as a diesel engine, but must have a larger combustion chamber (roughly 1.8 times) to keep the compression ratio down.

ie increasing displacement!

JHMEG

Rovi wrote:

Of course, plenty of CCs + turbos = a good thing

But only if you own your own oil well. And a refinery to go with it. And you don't mind killing the planet...

nastysimon

JHMEG wrote:

ie increasing displacement!

I'm not sure I understand what you mean. Displacement=PI x (bore/2)^2 x stroke x number of cylinders. So for a Rover 1.4 K series, that is 3.1416*(7.5*2)^2*7.9 which equals 1396, the displacement of that engine (measurements in cm and cc). The size and shape of the combustion chamber has nothing to do with displacement (but hugely effects compression ratio and performance). It could be the size of my ego and it wouldn't increase the displacement.
Only increasing the stroke, bore or number of cylinders on a diesel or petrol engine will result in a larger displacement. Therefore, a petrol engine with the same bore, stroke and number of cylinders as a diesel engine, but with a 1.8 times larger combustion chamber, has the same displacement, but about .556 times the compression ratio (and usually about 60% more power, all other things being equal).

But only if you own your own oil well. And a refinery to go with it. And you don't mind killing the planet...

Ok, increasing the engine size and adding a turbo is unlikely to reduce the carbon footprint of an engine, but it might not make it as bad as you think. You'll probably find that trying to get the same level of power out of a much smaller engine would result in even greater footprint.
If you drive, you are killing the planet, so obviously you don't mind doing so anyway. As someone who drives mostly for pleasure (public transport will suffice for most other purposes), I believe that driving a car which maximises that pleasure for a shorter distance is much better than driving a lesser car for a significantly greater distance to get the same enjoyment. Since I have never found a diesel which is anywhere near as much fun as a nice small lightweight petrol engined sports car, I think I'll stick to one of them. And my 3L V6 engine sounds oh so very sweet when it's sucking down those dead dinosaurs

gerbo

So you lost the bet.....

Owen

Anan1 wrote:

I think any turbo will have lag, it's just in the nature of the system. Some are much better than others, but none will have the immediacy of a big NA.

Me b*llicks. The Cooper S I had in Jan-June had zero lag. Foot down, it went. No build up, none of that nonsense. That's what a twin scroll turbo does for you. Also, the 535d has 2 turbos, a little one feeding the big one, and that also has practically zero lag. Turbos have come on significantly in the last 3 years.

jonny24ie

jonny24ie wrote:

Levin is 165BHP out of the factory on Jap fuel. You will loose power on our fuel unless you get a remap.

No.. you will lose power anyway. The remap is done to prevent damage to the engine. Although I'm fairly sure a remap is pointless on these cars anyway as the engine management system should retard the timing.

Idleater

ned78 wrote:

Me b*llicks. The Cooper S I had in Jan-June had zero lag. Foot down, it went. No build up, none of that nonsense.

isn't the mini cooper S a supercharged engine rather than a turbo?

JHMEG

nastysimon wrote:

with a 1.8 times larger combustion chamber, has the same displacement,

I don't understand how you can increase the size of the combustion chamber without increasing bore or stroke, or both, and thereby increasing displacement? Are you talking about increasing the size of the combustion chamber when the piston is at the top (fully compressed) by not going as close to the top, and therefore really talking about reducing compression? My understanding is combustion chamber size = volume when piston is at the bottom. Multiply by number of cylinders and you get cc.

nastysimon wrote:

Ok, increasing the engine size and adding a turbo is unlikely to reduce the carbon footprint of an engine, but it might not make it as bad as you think. You'll probably find that trying to get the same level of power out of a much smaller engine would result in even greater footprint.

You're right in that the rate at which fuel burns is directly proportional to the CO2 output. A 1.6 normally aspirated engine spinning at 8,000rpm would probably put out the same CO2 as a 2.0 spinning slower.

nastysimon wrote:

If you drive, you are killing the planet, so obviously you don't mind doing so anyway.

My comment was a bit tongue-in-cheek. What I really mean is the more fuel you burn the more you're helping things on their way. The train I get to work every day has 8 dirty diesel engines, so I'm doing my bit even by using public transport!

nastysimon

JHMEG wrote:

I don't understand how you can increase the size of the combustion chamber without increasing bore or stroke, or both, and thereby increasing displacement? Are you talking about increasing the size of the combustion chamber when the piston is at the top (fully compressed) by not going as close to the top, and therefore really talking about reducing compression? My understanding is combustion chamber size = volume when piston is at the bottom. Multiply by number of cylinders and you get cc.

AFAIK, the combustion chamber is that volume which is left when the piston is at top dead centre. And I was talking about reducing the compression (for a petrol over a diesel).
Engine displacement is accepted as the swept volume of the engine for one full revolution, so that all that matters when calculating displacement is the volume through which the pistons sweep. This might seem to favour engines with large combustion chambers, but in fact it doesn't really as despite having a larger volume charge, it has still sucked in the same amount but compressed it less. In fact, if anything it favours those with the smaller combustion chamber as they are (IIRC) potentially more efficient (for a given fuel).
Superchargers (which turbos are) screw with this as they effectively increase the size of the charge, giving you an effect somewhat equivalent to a larger displacement. But to do so, they reduce the efficiency of the exhaust and inlet systems and as the charge is generally considerably hotter, they reduce its effectiveness too. Additionally, they reduce the responsiveness of the engine, add weight, complexity, cost, reduce reliability, and make the engine less predictable (for a given revs with a NA car, opening the throttle the same amount on two different occasions will have the same results, with a turbo, you have to factor in the amount of pressure being created at that time). All that said and to the best of my knowledge, in some cases, a turbo can give greater efficiency than a non-turbo, particularly a low pressure turbo which is used to reduce the work that the engine has to do to compress the charge, something which really helps in diesels.

Idleater

nastysimon wrote:

Superchargers (which turbos are) screw with this as they effectively increase the size of the charge, giving you an effect somewhat equivalent to a larger displacement.

yes, but superchargers are cam driven (take a feed direct from the engine itself) whereas turbos are gas driven (take a feed from the exhaust gasses).

Superchargers therefore do not have lag because they are directly connected to the engine where as turbos require _some_ pressure in order to make the compressor spin.

Hence my comment about your comment about the cooper S having *no* lag, compared to the 525 with "virtually no lag".

Owen

nereid wrote:

isn't the mini cooper S a supercharged engine rather than a turbo?

2002-2006 it was Supercharged, the Cabrio still is, but the new 2007 R56 hatchback is Turbocharged.

Owen

nereid wrote:

Superchargers therefore do not have lag because they are directly connected to the engine where as turbos require _some_ pressure in order to make the compressor spin. Hence my comment about your comment about the cooper S having *no* lag, compared to the 525 with "virtually no lag".

Actually, it was my comment about the S, and a 535. And your assumption is correct, with older designed turbos, there was a spool up time, and that spool up time was dependent on exhaust pressure, but in the case of both the S, and the 535d, they're using very new types of turbo which exhibit no lag to the observer (To a dyno machine, perhaps there is a fraction of a second lag, but this is unperceiveable by a person). As explained, the turbo on the S is twin scroll, and the 535d has 2 turbos, a little one which is on constantly, and in turn, feeds the big one. Both very new technologies, and not based on the principles you have above.

nastysimon

nereid wrote:

yes, but superchargers are cam driven (take a feed direct from the engine itself) whereas turbos are gas driven (take a feed from the exhaust gasses).

Superchargers therefore do not have lag because they are directly connected to the engine where as turbos require _some_ pressure in order to make the compressor spin.

Hence my comment about your comment about the cooper S having *no* lag, compared to the 525 with "virtually no lag".

Sorry, you did not understand. The full and proper name for a turbo is a turbo-supercharger. Turbo-superchargers do have slightly different drawbacks to ordinary superchargers, but are more efficient and can operate through a wider range. Ordinary superchargers have no lag, and turbo-superchargers have lag. Lag is not the same thing as throttle responsiveness and does not affect it at all.

BTW, I never commented on either the MINI or BMW.

Anan1

nastysimon wrote:

Lag is not the same thing as throttle responsiveness and does not affect it at all.

??

nastysimon

Anan1 wrote:

??

Lag, as in turbo-lag is the time it takes the turbo to spool up. During this the throttle is still as responsive as ever. Throttle response is how quickly the engine responds to opening the throttle but does not include lag (which is nearly always an order of magnitude worse). Many cars have no turbo and really bad throttle response, even worse than many turbo cars. If the turbo engine responds quickly to the throttle opening (even if it is still spooling up), it has good throttle response even though it will soon give a slightly different response to the throttle.
A simple test is to blip the throttle while the engine is idling (jab it and release very quickly) and see what difference in time there is between you hitting th throttle and the engine responding. Now do the same starting with the engine at a constant revs (say at every 1000 rpm) and see if there is any difference. Of course, this leaves out one very significant factor, engine load, which requires you to be driving. Good throttle response will have a tiny delay between you hitting the throttle and the engine responding to it and will do so all the way through the revs and at every load.

Anan1

nastysimon wrote:

Lag, as in turbo-lag is the time it takes the turbo to spool up. During this the throttle is still as responsive as ever. Throttle response is how quickly the engine responds to opening the throttle but does not include lag (which is nearly always an order of magnitude worse)

I don't think so. An off-boost turbocharged engine is basically a low-compression NA until the turbo spools up. Any immediate throttle response will therefore be weak. No turbo = no shove.

Idleater

nastysimon wrote:

Sorry, you did not understand. The full and proper name for a turbo is a turbo-supercharger.

Nah, I understand the differences all right.

nastysimon wrote:

BTW, I never commented on either the MINI or BMW.

sorry, I mixed you up with Ned.

L.

nastysimon

Anan1 wrote:

I don't think so. An off-boost turbocharged engine is basically a low-compression NA until the turbo spools up. Any immediate throttle response will therefore be weak. No turbo = no shove.

It might give a comparatively weak response, but the delay between depressing the throttle and the engine deciding to go is what I was discussing, not the strength of the response, which is a function of the power delivery and engine power. Otherwise, a large engine would be more responsive as it gives a stronger response than a smaller one. Anyway, it's terminology and not really important.

Anan1

Fair enough. When I think of throttle response, I mean meaningful response, ie the best the engine can give under the conditions.:)

JHMEG

Throttle response is also greatly affected by the mass of the flywheel.

optiplexgx270

http://en.wikipedia.org/wiki/Toyota_A_engine#4A

Scroll down to the 4A-GE (20-valve). That be the block your mate and yourself be talking about.