74 replies to this topic

[DOHCPower]

Originally posted by Fat Boy


--At the risk of starting a holy war--

Torque is essentially a measure of engine efficiency. My guess is that the torque numbers that all of the engines produce are very similar. They are all very, very efficient

I would venture to say that in the current V10's most used operating range (13k-18.5k) they are actually very inefficient engines. When i say inefficient i am assuming we are speaking volumetrically here. But you are dealing with 18,500rpm, TQ becomes an afterthought.

[desmo]

F1 engines, I'd believe you'd find, have VEs above 100% for most of their useful rev range.

And on the torque thing... don't start. Dont

[Halfwitt]

Originally posted by desmo
F1 engines, I'd believe you'd find, have VEs above 100% for most of their useful rev range.

Quite right.

BMW's own statistics for their P83 engine (see http://forums.atlasf...3&highlight=p83), say that at 19000rpm, the engine uses 1995 cubic metres of air per hour, this works out at 117% volumetric efficiency. This is likely not to be absolutely correct, but is in the right ballpark. This may not be the speed of peak volumetric efficiency for this engine.

I wouldn't be surprised to hear of volumetric efficiencies of over 120% for F1 engines at some speeds.

[DOHCPower]

I understand what youre showing me, but i just dont buy it. I looked at the BMW engine page and it states the airflow, but it doesnt say WHEN that peak airflow is acheived. I have no doubts in my mind modern F1 engines reach VE's above 100%, i just dont beleieve this happens in the 13k-19k range.
My guess is theyre running somewhere around a 49mm stroke. I would expect peak tq to occur somewhere in the neighborhood of 12k. But since HP wins races, every effort is made to keep the TQ from falling off to drastically and for the HP #'s to climb towards oblivion, putting the declining TQ to faster and faster, *ahem* work.

[shaun979]

If I recall correctly, Ferrari 049 engine made peak torque at around 15,500 RPM.

[DOHCPower]

Which means that from 15,501 and up, VE would be below 100%.

[shaun979]

You are assuming peak VE to be 100%, when it is considerably above 100%. Nearly all race engines exceed 100% VE at peak.

[DOHCPower]

Good point.

I still stand by my theory however. Im guessing the TQ dropoff is pretty steep as RPM rises past peak TQ however, just as the horsepower climb is steep.

[desmo]

Max torque and power in F1 engines will have a difference of around 3000rpm.

Here's a plot generated in Ricardo WAVE, intended to show the effect of rod ratio on VEs. You can see the VE curves plotted against rpm.

http://members.atlas...om/desmo/VE.bmp

These are calculated not measured values, bit are from a source who'd know if they were well out of bounds. I should add that for simplicity's sake fixed intake lengths were assumed for this simulation, if variable length intakes were assumed the VEs would naturally have been higher.

I've got some torque/power curves a few years old for an F1 engine somewhere...

[desmo]

Originally posted by DOHCPower
Good point.

I still stand by my theory however. Im guessing the TQ dropoff is pretty steep as RPM rises past peak TQ however, just as the horsepower climb is steep.

You do realize that is somewhat self-contradictory don't you?

[DOHCPower]

No it isnt.

The TQ dropoff after peak tq is the inverse of the HP climb. Does that make sense?

[Greg Locock]

not mathematically, no.

[DOHCPower]

[shaun979]

?!!

[Ursus]

Perhaps an actual torque/power plot would be more useful....

Power=torque * rpms so you can't have a steep HP climb if you've got a sharp torque drop off.

[shaun979]

Originally posted by desmo
I've got some torque/power curves a few years old for an F1 engine somewhere...

If you could find and post them...

[12.9:1]

2000 Ferrari F1 engine

[desmo]

Thanks, 12.9:1, that's the one.

[Halfwitt]

Originally posted by DOHCPower
I understand what youre showing me, but i just dont buy it. I looked at the BMW engine page and it states the airflow, but it doesnt say WHEN that peak airflow is acheived. I have no doubts in my mind modern F1 engines reach VE's above 100%, i just dont beleieve this happens in the 13k-19k range.
My guess is theyre running somewhere around a 49mm stroke. I would expect peak tq to occur somewhere in the neighborhood of 12k. But since HP wins races, every effort is made to keep the TQ from falling off to drastically and for the HP #'s to climb towards oblivion, putting the declining TQ to faster and faster, *ahem* work.

OK, lets consider you AND BMW are correct, and we consider that the engine uses 1995 cubic metres per hour at just below 13000rpm. This gives a volumetric efficiency of 170%. I imagine this to be highly improbable. Peak torque occurs somethere around 15000 - 17000rpm depending on whose engine it is.

I don't think anyone has run a stroke around 49mm in an F1 V10 for a long time (possibly not since the 3 litre capacity limit was introduced). I'd say 25m/s would be a sensible piston speed for peak power. Lets imagine peak power at 18500rpm. This would give a stroke of 40.5mm

97mm bore x 40.59mm stroke for a V10 gives the correct displacement and is in the region most publications put current F1 bore sizes at.

The graph was very nice to illustrate your point. I don't know what your point is though, other than your assertion that the faster the torque drops off, the faster power climbs. Could you explain to me the portion just before peak torque where, with increasing engine speed, power is falling? These parts of the graph would seem to contradict my (albeit basic) understanding of engines and some of the laws of physics (and the Ferrari graph).

[DOHCPower]

The graph was exaggerated to illustrate my point, it didnt even include numbers, for petes sake. And yes, Peak torque can drop off while HP rises after peak VE. So if peak TQ on the ferrarri is 15500, and you peak power is 18,500, thats 3 thousand whole RPM with VE under 100%.

[Fat Boy]

Originally posted by DOHCPower
And yes, Peak torque can drop off while HP rises after peak VE.

Of course it can, that's not the weird part. The weird part is where you have torque rising and HP dropping. I suppose since neither axis is labeled, it might be w.r.t. how many beers we've had over the course of the evening. However, if the X-axis is RPM, then you're on crack.

Anyhow, bang your head against the floor until forgiven!

P.S. You can completely redeem yourself by naming the movie I just quoted.

[Halfwitt]

Originally posted by DOHCPower
The graph was exaggerated to illustrate my point, it didnt even include numbers, for petes sake. And yes, Peak torque can drop off while HP rises after peak VE. So if peak TQ on the ferrarri is 15500, and you peak power is 18,500, thats 3 thousand whole RPM with VE under 100%.

I'm sorry, but your assertion that VE is under 100% after peak torque is just wrong. Very wrong. In a good racing engine it will be above 100% way before peak torque and carries on above 100% until after peak power. I don't argue with your point about power rising with torque dropping, only with your idea that "The TQ dropoff after peak tq is the inverse of the HP climb", which is clearly wrong. I'm going to bed before I get stressed....;)

[Halfwitt]

Originally posted by Halfwitt


I'm sorry, but your assertion that VE is under 100% after peak torque is just wrong. Very wrong. In a good racing engine it will be above 100% way before peak torque and carries on above 100% until after peak power. I don't argue with your point about power rising with torque dropping, only with your idea that "The TQ dropoff after peak tq is the inverse of the HP climb", which is clearly wrong. I'm going to bed before I get stressed....;)

Got some figures for you (don't ask where, I'm not telling, but they are correct):

For both a recent F1 V10 (don't know how recent, but not too old) and a 2v Pushrod 5l Ford (production based) race engine, VE at peak torque AND peak power is OVER 120%.

[DOHCPower]

Im sorry i just finished a history paper, and i am by NO means doing any more researching tonite! As far as the movie quote, im sorry i have absolutely no idea where thats from. But how bout this one...

"I said he'll flip ya.... flip ya for real..."

Now on to more important matters, i was always under the assumption that peak TQ was always where VE was 100%, and i guess this started the chain of illogical thinking in my twisted little mind. Im sorry if i stressed any of the half witts here, but i think they may have needed a little excercise. Ok, im gonna go have some guiness before heading off to sleep.

P.S. doesnt my sig reveal how much i really know?

[Fat Boy]

"The greatest trick the Devil ever pulled was convincing the world he didn't exist."
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The torque peak of an engine may or may not be at the peak volumetric efficiency. The torque peak is the point of highest BMEP. Volumetric efficiency is part of it, but it ain't the whole enchilada. There are several 'efficiencies' of an engine. You have to add up the pluses and minuses and to see where everything shakes out.

As several have pointed out, VE is often over 100%, even in a good street engine. Remember, we are dealing with mostly air here. It's compressible. You can get more than 100% VE because the 'column' of air charging into the cylinder has inertia. When the piston hits BDC, the inertia of the air going into the cylinder allows it to 'over-pack' the cylinder to some extent. Engine builders spend an absurd amount of time trying to figure out how to make this happen over a wide range of RPM. The closer they can come to keeping the VE close to it's peak (regardless of the value of that peak), the more broad the torque curve is and the higher the HP peak will be.