7 replies to this topic

[awill4x4]

I am new here, and I wonder if anyone can answer a few questions for me?
Do all current F1 engines use pneumatic valve operation as pioneered by Renault?
If so, what are the maximum revs available?
Is 800 bhp an accurate figure bandied about by race commentators?
Does anyone know which engines are the lightest in modern F1 cars?
With Honda re-entering F1 with BAR will their engine be different to the current Mugen/Honda?
Thanks for any help you are able to give me.
Regards awill.

[DangerMouse]

F1 engines use Pneumatic pressure to suck the valve onto the cam lobe ensuring there is no valve bounce at high revs, this also eliminates the need for valve springs if done well enough.

Engine manufacturers have been experimenting with camshaft-less engines for years relying on pneumatics or magnetic fields to open and close the valve, I don't know if any of these engines have made it through to F1 though I doubt it, I'd have thought magnetic valve actuation would be the way to go as this would be easier to control electronically.

800BHP seems feasible.

Some F1 engines in Grenade trim (Qualifying) probably run at around 18-18,5000 RPM. 20,000 RPM reliably isn't a problem with today's technology, it's just that with the format that is F1 these days (Normally aspirated V10 3 Litre) power drops off markedly at high RPM due to the relatively large cylinders not filling quickly enough for the engine to make power at higher revs. ( the valvea are only open for a fraction of a second at high RPM - without forced induction this time becomes too little to fill and scavenge the cylinder efficiently - hence the interest in V12s again.) Also I believe Ferrari, Stewart and Prosts top exit exhaust system are to alleviate this restriction by causing forced scavenging (negative pressure in the exhaust system.) Everybody keep mentioning the aerodynamic advantage these exhausts allow, I think that's a red herring, to distract the FIA as forced extraction would be a grey area and possibly illegal.

The Ford CR-1 is reputed to be the lightest engine in F1, which could weigh as little as 100KGs

The New Bar Honda is a completely new unit - technology destine for the new unit is being tested on the current Mugan.

[Martin]

DM - are the valves under constant pneumatic pressure or are they merely closed by pneumatics? The latter would surely save some energy being wasted fighting against the pressure although you would have to ensure that the downward valve travel was mechanically limited.
I've been having the same thoughts about the thread on re-located exhausts: that they might be there to suck out the exhaust (sort of reverse turbo charging) thus saving energy wasted on the exhaust stroke and even as you say creating a partial vacuum in the cylinder head thus improving induction. Would this really make a difference do you think? Two things spring to mind: 1) a vacuum is an absolute measure and once achieved further sucking is a waste of time and with the high compression ratios the volume inside the cyclinder head at TDC is miniscule and 2) balancing the exhaust back pressure - something that remains a mystery to me and I understand it to be something of a black art. From what I understand the amount of fuel mixture going into the engine is specifically tuned with reference to the amount of back pressure and the balancing of exhaust pipes (where they meet - wasn't there another thread about flat-plane cranks about this or was I dreaming) is of paramount importance. If you're sucking out the exhaust, this balance will be interfered with since the faster the car is going the more depression created. 15,000 rpm in 2nd will create less of a vacuum than 15,000 in 6th.

On a completely (sort of) different point - how is the displacement of engines verified by the scrutineers? Does Charlie Whiting get the teams to take the heads off and get his tape measure out each race? or are they somehow sealed under the watch of an FIA scrutineer when they're built?

Cheers

Martin

PS Christiaan - always go first to this forum - always much more interesting, enlightening and well thought out posts than in the zoo.

[Christiaan]

Of course Martin, this forum is more interesting, and its always to the point!

With regard to Ferrari's exhaust and FIA I don't see it being a problem if the exhaust is responsible for the "forced induction" because FIA effectively banned only blowers.

If you look at the second genration BMW M5 and the Mclaren F1 engine (also made by BMW) you will see that they have weird shaped exhausts, especially the Mclaren. They have all sorts of lobes and stuff and apparently this is so that the exhaust gases set up an acoustic pressure wave which travels coherently with the engine speed. The wave sucks out exhuast and at a very narrow rev band sucks in air. The band is quite narrow so some highly advanced supercars have variable exhaust length to keep the wave cycle coherent with the engine

[Yelnats]

I suppose there is some advantage to the slight negative pressure assisting in extraction of exhaust gases but this has always been available on rear facing exhasts, to a certain extent, as it is (or was) with forward facing intakes.

I've always though the main reason for the upper surface exhaust introduced by Ferrari was to integrate the exhast with the areodynamics and clean the whole rear airflow up a bit. This would produce just a little more downforce and remove one more design variable of the uncontrolled exhast gases interfering with other areodynymic elements.

[PDA]

martin - the valves are under constant pressure from the pneumatic "spring". In effect, a compressed air filled chamber surrounds the stem of the valve. It is charged with compressed gas (probably nitrogen) before each race. Usually it needs no maintainance diring a race, but Irvines Ferrari was pulled in to recompress the system when the pressure was dropping at the Brazil race this year. The compresssed air acts as a spring, but does not suffer the mechanical problems that wire valve springs have. This allows much higher revs than would be possible with metal wire valve springs.

DM - electromagnetic valve actuation is still in an early stage of development. The systems now being tested are rather heavy - much heavier than camshaft/spring type systems. I expect that eventually they will be light enough and reliable enough for racing use. As you say, they would (potentially) give great control over variable valve timing and lift, which should be beneficial.

Martin - cylinder size is measured by inserting measuring devices into the cylinder via the spark plug hole. I don't know for sure, but I wouldn't be surprised if the FIA have the right to ask for the engine to be stripped for inspection after a race. After all, they are going to be stripped for rebuilding anyway. I know that in NASCAR the winners engine is stripped so that amongst other things, the compression ratio can be measured, because that is a limited characteristic in NASCAR engines.

[SlowDrivr]

I've read that due to the speed at which the valves can be moved up and down using electromagnetics, that the maximum speed they would currently be usable at would be like 5-6krpm. I think it was Mercedes that is planning on using this system in one of their upcoming street cars (like a 2002 model or so).

[Yelnats]

A big problem with a camless valve systems is controlling the speed at which the valve hits the seats. A cam is designed to gently lower the valve to the seat whereas camless hydraulic/pneumatic/electodynamic systems have great difficulty controling the valve motion. Rapid opening and closing is the easy part of designing these systems. The hard part is designing some form of sensor and control system to limit seat impacts and accuratly profile the valve movement.

The big advantage of Pneumatic Valve Springs is that are fatigue free and inertionless but are not practical on road cars yet due to the recharging problem. But just wait, the Japanese will probably have them on their luxury cars in the next few years with some form of auto-recharging built, perhaps from a carbon fire wrapped bottle with 20k psi of nitrogen in it (and a big Do Not Drop" sign on it I hope). [;->