34 replies to this topic

[mrman_3k]

I would like to know what the typical F1 engine idle and stall speeds are. If I am not mistaken, isn't the engine idle around 6000rpm? Also I heard the stall speed is around 4000rpm, is this true? If so, why do they have such a high stall speed compared to road cars that can put around under 1,000rpm? I have a feeling it has to do with the inertia of the flywheel, and engine parts but would like to hear the expert's opinions.

Thanks in advance!

[Greg Locock]

What do you mean by a stall speed?

[mrman_3k]

From a standstill, at what RPM would a typical F1 engine stall? For example, on my road car, the idle engine speed is 800rpm. The stall speed is 300-400rpm.

[Greg Locock]

Is it really? My Toyota 2 litre will pull cleanly from 300 rpm in 3rd gear. I'm surprised yours won't run below that, given that the starter motor can only turn it at 120 -150 rpm typically.

What physical process is it that you think stops the engine going round below some arbitrary speed?

I've known engines that will run at zero rpm. Drop fuel into the cylinder, replace spark plug. switch ignition on. flick the contact breaker.

[mrman_3k]

I have an Infiniti G35 Sedan 6MT. It has the famous Nissan VQ engine making 260bhp+.

The part about my car stalling at 300rpm is besides the point (it might be lower but I'm not in a rush to go test it).

What is the idle RPM of a Formula 1 engine? What is the stall RPM of an F1 engine?

[Wuzak]

I would think that the stall speed is dependant on the engine's torque curve and the load on the engine.

[mrman_3k]

Yes I know what it is dependent on, but typically - what is the RPM at which an F1 engine idles?

[rodlamas]

BMW V10 P83 has a 4,000 rpm idle speed

[mrman_3k]

Thank you rodlamas!

Why do F1 engines have such a high idle speed?

Anyone know the stall speed?

[indigoid]

guessing, but they might need to spin an alternator at a certain speed to power all the gadgets... and there are many! very probably they have an under-driven alternator (to conserve power), so at lower rpm it would not be spinning fast enough

[jondoe955]

Just guessing, but these low inertia engines would need rpm's to replace a heavy flywheel/clutch. Also the slim power band would need a high idle speed to stay in range.
My brother was in Japan in the early 60's and mentioned seeing 50cc racing bikes that idled at 5000 rpm.

[wayneamartin]

possible reasons for high idle/stall rpm

1) Friction, not likely, friction must be pretty low to run at 19000 rpm

2) Electric Power, possible, but clever power supply design should solve this

3) Lubrication, not likely pumps should be able to pull with any rpm

which leads to

4) Induction, high rpm engines typically have a high degree of intake/exhaust valve lift overlap. At low rpms this overlap would reduce the efficiency of cylinder filling and compression to the point at which the engine stalls. And I am pretty sure that f1 does not allow variable valve timing. The old hot cam street rod would never idle and I would guess f1 cams are fairly hot.

Wayne

[Chevy II Nova]

It's the nature of a high performance engine to idle higher, mostly because the engine makes it's power at the high RPM's.

The Hemi you find in a Baracuda probably idles at 800, a Top Fuel Hemi spins at a few grand.

[MRC]

I imagine that it's a combination of some of the previous poster's reasons, such as high overlap, and having enough power to auxilary systems. I've heard Matchett or one of the other guys on Speedvision mentioning idle or a suggested minimum revs to keep the car at, in the pits, either due to electrics or keeping the pneumatics/hydraulics pressurized. Can't remember which it was.

I would add one more reason that an engine like this will have a relatively high idle speed. The fuel injectors can only cycle so slowly. While the injectors are peak & hold, with likely coil pre-charging, the injectors still will have a minimum pulse width. The injectors must be sized for the maximum rpm, too, not just idle. Performance at the high range of the rpm band will be far more important then minimizing idle speed.

Don't know what rpm stall speed would be at. I guess from other cars, maybe you could make a rule of thumb that it's about half or less of the idle speed????????

[Monstrobolaxa]

F1 engines have relativly high idle due to electric and hydraulic reasons.

Usually each engine has its own idle, dropping below that rpm number the battery will start to loose current and simply won't have enough to continue to give energy to the ignition system and to all the other controllers in the car.

The hydraulics of a F1 car are due to the reviing of the engine and the gear selection system works with hydraulic pressure (electro-hydraulic actuator). Usually when you see a car having dificulty in selecting a gear when it has stopped for a pit stop, is due to low hydraulic pressure.

[JollyRoger]

From memory the reason is to do with valve sizes/how long they are open etc.

Race engines like these are designed to breath well at high rpms - which usually translates into terrible breathing at low rpms - thus the need for a much higher idle speed.

[WPT]

Another possible reason for high idle speeds in f-1 engines is the contact stress between the cam profile and the finger rocker arm. WPT

[marion5drsn]

mrman_3k Quote about high idle speeds?

If one draws a graph showing the overlap of the intake and exhaust between various camshafts one cannot help but notice the effect of the over lap on the idle speeds. A quick perusal of a book or catalog on camshafts shows this up very quickly.

Statements such as, “Rough idle 2800 stall or rough idle 3000 rpm stall or rough idle 3500 stall all speak for themselves. Remember these are on big engines up to 454 cubic inches 7.4 liters.

There are other things that affect the idle but these are things that are at the top of the list. Next comes big bore openings in the carburetor section of any engine along with big valves, big intake and exhaust passages. Bore/stroke ratios of 1/.5 make for big rpms but also high idle and stall speeds. If one makes the bore twice the stroke you are going to have some very large valves etc, etc.

Add to all the above and visualize just how large the valves are in a F1 engine. I don’t know if this is what you are after but that is the start of idle problems. M.L. Anderson

[J. Edlund]

My guess is that the idle is so high because of alternator power and the flow from the hydraulic pump. Since the battery of a F1 car is only about 2Ah it cannot run on that for long and the hydraulics are on the limits in slow corners.

The figures I've seen on valve timing doesn't seem that extreme, the possibility may in the engine timing case be the slow piston velocity at low speeds due to the short stroke. But usually this is more a fuel system problem than an induction problem (drag racing engines with cams around 330 degrees can usually idle quite well, if they are fuel injected that will say), even if it causes a poor low end.

Minimum engine speed during a race is about 6000 rpm in first gear in slow corners. At that speed the hydraulic pump cannot supply the hydralic system with enough flow for maximum capacity for any longer time.

The hydraulic pump supplies the throttles, variable inlets, clutch, fuel tank lid, power steering, gear selector and differential (did I forget anything?) so there are a few things.

[marion5drsn]

Many of the hydraulics don't need a large amount of continuous pumping action, as I believe that would be better covered by a small, hydraulic accumulator/pulsation dampeners. If F1 cars don't have one of these I would be very much surprised. For the pressures used in the applications stated they would not have to be very large or very heavy, probably not over 250 p.s.i.g. With the pressures needed they could be made of spun glass or many other light materials. It wouldn’t need to be over one liter at the very most.
M.L. Anderson

[mrman_3k]

So if the reason for such a high idle RPM is to supply power to the hydraulics system, why do road cars have an idle RPM that is over 10 times slower when they usually have even more systems to supply power to?

[marion5drsn]

Most of the hydraulic systems in passenger cars aren't use very often, example;. Brakes are Vacuum/hydraulic, power steering are belt driven, windows are electrical as are seats.

Many of these systems are separate from one another altho just why I don't know as I think about it. One might figure out the Citroen and see how that one works.

Also cars have very large batteries, F1 cars can't afford this.

I believe that F1 cars are a very special case as opposed to passenger cars. M. L. Anderson

[Greg Locock]

Most of the ancillaries on a road car are sized to supply sufficient output at idle (alternator and A/C and PS pump being the big three). This means they are oversized for much of the rest of the time.

They could be made a lot smaller if the idle speed were higher, but idle has a disproportionate contribution to the city cycle fuel and emissions scores.

The slower the idle speed is for a given power output, the more the throttle is opened, and so the efficiency improves.

The lower limit of idle speed in a road car is set by NVH and drivability concerns, the engine itself will obviously run at speeds right down to the cranking speed, which is typically 120-150 rpm. My Corona will pull third gear from 300 rpm, at which speed the engine is quite happy, the exhaust and engine mounts are not.

[marion5drsn]

wayneamartin

4) Induction, high rpm engines typically have a high degree of intake/exhaust valve lift overlap . At low rpms this overlap would reduce the efficiency of cylinder filling and compression to the point at which the engine stalls. And I am pretty sure that f1 does not allow variable valve timing. The old hot cam street rod would never idle and I would guess f1 cams are fairly hot.

You hit this right on the head for sure.

Also after what Greg said it's isn't any wonder that Air Conditioning eats up so much fuel, but power steering surprises me? M.L. Anderson

[desmo]

I am aware of nothing in the regs prohibiting variable valve timing in F1.

[Greg Locock]

The PS pump has to be sized to supply full authority when parking, which is at idle +100 rpm in a typical auto. I'd guess this is around 300W (from the size of electric PAS). The output of a pump varies in some well defined way with speed - I don't know what that is, but anyway since the redline is 10 times idle speed it is obviously going to be a lot of wasted energy at higher engine speeds. Most of this energy goes into the fluid, which causes problems in its own right, and obviously represents a huge waste of power and fuel. Hence the attractiveness of variable valving or variable speed on the PS pump.

[turby]

A question to all:

In this thread very often the big overlap in valve lift of a F1 engine was mentioned. In another thread "Ferrari F1-2000 Pictures" somebody posted these wonderful drawings from the new book of Peter Wright. One of these pictures shows a cutaway drawing of the engine.

In this drawing the left piston is in the uppermost position. From the position of the cam lobes, the next stroke must be the inlet stroke. This is because both cams rotate in the same direction (can be seen from the gear arrangement in the other engine picture). It could not be the power stroke because in either rotating direction of the cams one valve would open.

In this position of the piston between exhaust stroke and inlet stroke we would expect the mentioned valve overlap. But it seems that both valves are fully closed. What happens here?

Either the 049 engine has no overlap (I doubt that) or the drawings have been "falsified" prior to publishing. Or - third possibility - I overlooked something. Your comments?

[McGuire]

Originally posted by turby
Either the 049 engine has no overlap (I doubt that) or the drawings have been "falsified" prior to publishing. Or - third possibility - I overlooked something. Your comments?

You see this all the time. Such illustrations are not working drawings and not intended to show that degree of detail. In most examples of technical art, cutaways especially, you will often see such incongruities. Sometimes it is intentional, in order to highlight some feature more clearly, or sometimes it may be artist's convenience or simply an oversight. But in any case, a realistic depiction of valve timing ( ! ) is probably a bit too much to ask. Look at it this way: if the illustration does not show the cam gears, there is no reason to believe they are installed and properly timed, eh?

[marion5drsn]

I doubt that even if the drawing were perfect the valves at that point aren't open to a large extent, just enough to let sound waves pass thru. The passing of the gases is just enough to mess up the gas flow in case the engines gets down to that rpm where the gas flow wants to reverse.
Even if the drawing tried to show it .030 to .040" isn't very much on a small drawing.
I have an old book of the old M.B. M165 camshaft drawing of the raise and fall of the lobe. The drawing is about 5.315 to 1 so the overlap area is easily seen, the overlap height would be .071".
This would be difficult to see even if drawn perfectly to scale. This is one of the reasons that an old statement in the old shops was, "Don't scale the print." Being especially true when dealing with true B.P's. made using ammonia.

Yours, M.L. Anderson

[J. Edlund]

The hydraulic pump used by Ferrari in 2000 was an Abex variable-displacement swash plate pump, it has a displacement of maximum 2.5cc/rev running at 71.5% of engine speed (originally developed for military aircraft). At 6000 rpm the pump can deliver 10.7 litres per minute and at maximum rpm the pump can deliver 32.2 litres/minute. The system pressure is 3120 psi (about 210 bar), the reservoir is pressurised to 3.5 bar.

Oil flow is a maximum 27.3 l/min + tare flow of the MOOG series 30 valves which is between .25 and .35 l/min per valve, eight valves are used which means that the tare flow is about 2.5 l/min so the maximum flow is 29.8 l/min.

This means that the pump will not be able to deliver full flow at low engine speeds.

The battery was 2 Ah, and the permanent magnet alternator delivered 41.2 amps at 9000 rpm, alternator speed I assume. The question is what the kick in speed is?

Fuel injected drag racing engines often use more extreme cams than F1 engines, and still they can idle at low engine speeds. This was however not the case with carbureted engines where the pressure loss over the carburetor caused idle problems.

[crono33]

Dont forget that most cars have idle valves which keep the engine running even when alternator, AC and PS pump are in use, therefore even at idle rpm the engine is delivering some power used by these ancillaries


gm

Originally posted by Greg Locock
The PS pump has to be sized to supply full authority when parking, which is at idle +100 rpm in a typical auto. I'd guess this is around 300W (from the size of electric PAS). The output of a pump varies in some well defined way with speed - I don't know what that is, but anyway since the redline is 10 times idle speed it is obviously going to be a lot of wasted energy at higher engine speeds. Most of this energy goes into the fluid, which causes problems in its own right, and obviously represents a huge waste of power and fuel. Hence the attractiveness of variable valving or variable speed on the PS pump.

[J. Edlund]

Originally posted by crono33
Dont forget that most cars have idle valves which keep the engine running even when alternator, AC and PS pump are in use, therefore even at idle rpm the engine is delivering some power used by these ancillaries


gm

Modern car engines, just like F1 engines have throttles that are controlled by the ECU, it can therefore control idle with no need of any idle air valve.

[Greg Locock]

No, that is not so in my experience. The main butterfly/stepper motor is too coarse for controlling idle speed, so a separate idle control valve is used, at least on larger engines. We typically run -60 to -70 kPA MAP at idle - about 3% of the maximum airflow the butterfly handles at full power, and we need to control that to about 3% accuracy in itself, ie 0.09% of the full power airflow. Check out the throttle body on your own car - if it has emission control on it then it will almost certainly have electronically controlled idle speed, and I am reasonably sure that every engine I've seen does not do this using the main throttle.

[wayneamartin]

Having read the follow up posts on this thread I have think I may have been wrong with my opinion. I remember watching super modified pulling tractors in the 1970s and they could not idle. I based my theory on that. As Edlund points out this was a problem with carbs that is solved by fuel injection. So, it seem likely to me the reason F1 engines can't idle is because the engine has a lower than expected power output at low rpms because of the high cam overlap and a high load from the pumps and electrical systems. Perhaps the cost of stalling is too high, can't restart and the teams just figure out the minimum rpm they need on a course and make that the min rpm to minimize the chances of stalling on a glitch or spin.

Wayne

[J. Edlund]

Originally posted by Greg Locock
No, that is not so in my experience. The main butterfly/stepper motor is too coarse for controlling idle speed, so a separate idle control valve is used, at least on larger engines. We typically run -60 to -70 kPA MAP at idle - about 3% of the maximum airflow the butterfly handles at full power, and we need to control that to about 3% accuracy in itself, ie 0.09% of the full power airflow. Check out the throttle body on your own car - if it has emission control on it then it will almost certainly have electronically controlled idle speed, and I am reasonably sure that every engine I've seen does not do this using the main throttle.

I've already checked that. The throttle alone is used to control the idle. I have technical descriptions on Boschs ME7 systems and Saabs Trionic 7 systems, on both systems the throttle is used to control the idle speed. Both systems work the same way by torque demand, on idle the torque demand depends on for example if the A/C compressor is on, the load on the generator and so on, from this a throttle angle is calculated and then controlled and adjusted if needed.

I have also come to think of another reason for the high idle speed: coolant flow. On normal cars the water pump is often geared so this is solved but I would assume that they don't want to loose high end power just so the coolant flow can be higher at low revs.