Switching to four cylinders

[proditto]

The GM Northstar production engine has cylinder deactivation as a get you home if the engine overheats. As the GP engine is not under load when idling and little load during a safety car cylinder deactivation would be easy (if legal during safety car).
The use of engine acceleration as the trigger for traction control is certainly used on rally cars. My ECU from a supplier of race/rally equipment uses this system

[DaveKillens]

Problem: to combat heat build-up while idling in pit lane (during qualifying).

Solution: use the air pumping qualities of an internal combustion engine to pump cooling (ambient temp) air through the cylinders to assist cooling.

As mistareno pointed out: It is currently done completely electronically. The ECU cuts both the fuel and spark to four rotating cylinders per cycle. For example, if the firing order was - 1-8-7-2-6-5-4-3.

Then the first cycle would result in 1-7-6-4 and the next would be 8-2-5-3

It basically runs as 2 alternating 4 cylinder engines, there are pumping loses associated with the valves closing and the compression for the unused cylinders, but these also help balance the engine out.

So what ahppens that on every second cycle, cooling air is pumped through each cylinder, and this keeps the engine cooler while it is waiting for release from the pit lane.

[CMSMJ1]

Problem: to combat heat build-up while idling in pit lane (during qualifying).

Solution: use the air pumping qualities of an internal combustion engine to pump cooling (ambient temp) air through the cylinders to assist cooling.

As mistareno pointed out: It is currently done completely electronically. The ECU cuts both the fuel and spark to four rotating cylinders per cycle. For example, if the firing order was - 1-8-7-2-6-5-4-3.

Then the first cycle would result in 1-7-6-4 and the next would be 8-2-5-3

It basically runs as 2 alternating 4 cylinder engines, there are pumping loses associated with the valves closing and the compression for the unused cylinders, but these also help balance the engine out.

So what ahppens that on every second cycle, cooling air is pumped through each cylinder, and this keeps the engine cooler while it is waiting for release from the pit lane.

I am not convinced on that one mate - the air would be compressed still and the internals of the motor would be bloody hot.

The lack of heat by firing the pistons is where they are gaining cooling efficiency.

It is a bit chicken<>egg<>chicken but you cannot really imagin "cooling" air being ingested into a hot airbox, a hot inlet tract and a bloody hot motor and that it will do much good when it is compressed and heated up by compression before being exhausted?

Not setting off the explosion in the first place keeps it cooler..

Thats my tuppence anyways

EDIT>>>>You need to run coolant faster or colder to cool it down..or make it heat up less to start with - there you go..an easier way of putting it..lol

[DaveKillens]

It's all good, CMSMJ1. That's what this forum is all about, people discussing different opinions and conclusions. I thank you and appreciate the civilised and polite manner of your difference of opinion.

I hope some other forum members can witness this and come away with the understanding that you can disagree with another without getting personal or nasty.

[bazanaius]

to continue the mutual appreciation, I'd imagine that every little helps and the air passing through would remove heat (it has to come from somewhere). I'd imagine the lack of ignition contributes a great deal more however.

[pitlaneimmigrant]

The software allows cylinders to be switch off to conserve fuel and keep the engine cooler. This can be either be alternating sets of 4 cylinders, as mentioned above, or one bank can be shut off completely (I believe a 6 cylinder mode is also possible)
The engine can be set to switch to 4 cylinder mode at a predetermined RPM level and does not necessarily require an engine map change, although I suppose teams could have a very lean map for running under safety car.
With the standard MES software it is no longer a case of teams 'having the technology' or not, it is just a question of whether they are happy running their engines in 4 cylinder mode for long periods of time, as the heat distribution in the engine is not normal.

[Belatti]

It is a bit chicken<>egg<>chicken but you cannot really imagin "cooling" air being ingested into a hot airbox, a hot inlet tract and a bloody hot motor and that it will do much good when it is compressed and heated up by compression before being exhausted?

I think you are talking about hot and cold depending on what your skin can feel. The "hot" airbox and the "hot" inlet tract do not increase the air temp that much. As you rightly point out, the compression does.

Still, that compressed air, if hotter than when its "admited" by the airbox is still cold enough for the cylinder walls and piston heads.

In aircooled 2 strokes go-karts engines, excess fuel its used to cool down the engine. In F1 fuel consumption matters so that its not posible.

In 1/4 mile tunned carburated street cars (I´m not talking dragsters, top fuels or funny cars here) it is common to see a coper tube arround the inlet tract that carries "hot" water from the cooling system, to help warming the mixture before entering the cylinder. The vacuum created to suck the mixture is what cools down inlet air.

[donskar]

It is a bit chicken<>egg<>chicken but you cannot really imagin "cooling" air being ingested into a hot airbox, a hot inlet tract and a bloody hot motor and that it will do much good when it is compressed and heated up by compression before being exhausted?

I think you are talking about hot and cold depending on what your skin can feel. The "hot" airbox and the "hot" inlet tract do not increase the air temp that much. As you rightly point out, the compression does.

Still, that compressed air, if hotter than when its "admited" by the airbox is still cold enough for the cylinder walls and piston heads.

In aircooled 2 strokes go-karts engines, excess fuel its used to cool down the engine. In F1 fuel consumption matters so that its not posible.

In 1/4 mile tunned carburated street cars (I´m not talking dragsters, top fuels or funny cars here) it is common to see a coper tube arround the inlet tract that carries "hot" water from the cooling system, to help warming the mixture before entering the cylinder. The vacuum created to suck the mixture is what cools down inlet air.

Belatti, perhaps I muisunderstand, but I think you are referring to a "cool can." Many drag racers pass their fuel line through a can filled with ice. The fuel line is coiled inside the can filled with ice. The gasoline is cooled and the intake charge is therefore denser -- making for more power.

[riff_raff]

I find it hard to believe that "skip firing" cylinders on an F1 engine while running slow behind the pace car or during a pit stop would provide any real benefits with regards to fuel consumption or cooling.

As for cooling, the liquid cooling system is always functional whenever the engine is running, and is fully capable of cooling the engine at max power. So cooling at low power or idle should present no problem. Having said that, F1 engine coolant jackets are normally kept away from the inlet port area of the head in order to prevent heating of the intake charge. At race pace, there is enough intake air flow and latent heat cooling from the fuel to keep cylinder head temps within reason around the intake ports. The piston crown is also somewhat air cooled by the intake charge, especially with the huge amounts of valve timing overlap and reversion effects going on. Piston cooling would be compromised in a cylinder that is not firing or fueled.

Lastly, a highly strung F1 engine will barely run at speeds below about 8000 rpm under the best of conditions, firing on all cylinders. Getting it to run at that speed/load on half of its cylinders would seem impossible.

Of course, I may be wrong.

[ISLAMATRON]

rif raff, you are forgetting that the F1 cooling systems are not forced induction, they have no fans, so the air thru the radiators only moves as fast as the car, so at low to no speed the air becomes stagnant and super heated and loses its cooling ability. That is why the teams reveted to skip firing the engines.

Within the SECU the teams program a setting for cooling/fuel saving behind the safety car, running in top gear and 4 cylinders, the cars dont run under 8000 rpm under racing conditions but they do behind the safety car. The incoming air into the engine cools quite a bit and has a net cooling effect evan after being compressed.

It may be hard to believe for you but it been a feature for f1 cars for at least 2 years now.

[riff_raff]

ISLAMATRON,

If you say that F1 engines employ skip-firing during pace laps or when pitting, I'll have to take your word for it since I don't know any different. But as I said, I honestly can't believe it really makes much difference for cooling on pace laps, and I know for a fact that skip-firing is very difficult to do, especially with an F1 engine.

As for cooling on pace laps, the heat exchangers need to reject a fixed heat load, whether it comes from 4 cylinders firing or eight. The cooling circuit can't tell the difference of how many many cylinders are firing, since all the coolant gets mixed together in the end. All the heat exchangers know is that they need to reject a certain proportion of the total heat energy generated by the engine's combustion. I would also propose that the heat exchanger system designed to reject the heat load of an 800hp engine at an average speed of about 150mph, is probably overcooling for an engine producing about 150hp during an 80mph pace lap.

As for skip-firing, the ECU architecture for race engines is actually less demanding than for a production engine. The F1 engine ECU is more of an open-loop system than the typical road car, since it is required to operate under much more limited conditions. And getting a road car engine to operate properly while skip-firing is still incredibly difficult, even with its sophisticated ECU mapping, software and algorithms, closed-loop feedback, and multi year development. So I can only imagine how hard it would be to do successfully with an alpha-N type ECU like those used for F1.

Like I said, I don't know any different. I just find it hard to believe.

Best regards,
Terry

[xpensive]

Just like riff_raff, this info on skip-firing is something completely new to me.
Obviously, I have heard the reports of teams having overheating problems in the pits or on the grid when standing still for too long, hence those funny little fans in the sidepods I guess. But at 80 mph behind the pace-car?

As for saving fuel, I guess every little bit counts.