Toluene has a lower calorific heating value than gasoline, regardless of which factory it came out of - but then again a know-it-all like yourself should have known that already

Toluene was up to 83% of the fuel, what was the rest?

One problem with vertical gas ports is soot build up over longer durations. Eventually soot from the combustion will clog the ports significantly reducing the ring sealing. Yet we see those putting pistons with vertical gas ports in their street engines...



The calorific value of the racing fuels used in F1 during the eighties wasn't that high (Honda did publish the specs of their Elf fuel).

Basically the fuel needed to do two things; to decrease knock as much as possible while fulfilling the RON 102 requirement and to provide as much energy per volume of fuel. The toluene/n-heptane fuel provided the latter not by a high calorific value but by a high density. The race fuel was significantly denser than ordinary pump gas.

Pro Stock engines don't need much ring sealing, they also get away using very soft valve spring (some even use titanium springs) and thin motor oils, all for reducing friction. F1 and NASCAR engines run longer so they need a better sealing, but not that much. All F1 engines these days use one ring + oil scraper. Le Mans engines needs a good seal, I doubt that anyone is using less than two rings + scraper. Le Mans engines also use thicker motor oils, more wear resistant high Si piston alloys and many even prefer steel valves over lightweight titanium items.

Engine builders will run the lightest/thinnest weight oil they can get away without having metal parts come in direct contact with each other. Less drag on parts, less work for the oil pump, etc. Completely agree on that point.
But low valve spring pressures? Well in excess of 1000Lbs over the nose (for cams that far exceed 1in valve travel with ridiculous rise rates) seems a little high to call low pressure. And titanium springs just last longer with reasonably similar pressures.
And pro stock motors run very high cylinder pressures, requiring more pressure on the rings for sealing. I have seen some pistons with top and lateral gas ports in an effort to seal better.

When it comes to oils the tricky part is that while a lower viscosity oil usually result in a lower bottom end friction loss, valvetrain friction tend to increase. It gets even more complicated when fuel can dillute the oil and breakdown of VI improvers reduce the viscosity of the oil over time.

The harder the valve springs are, the greater the valvetrain friction loss will be. So in order to reduce losses the softest spring possible should be chosen, obviously with regard to the mass of the valve and the engine speed, and Pro Stock valves aren't exactly small.

Titanium valve springs have a few problems related to wear and quality control if I remember correctly. I have an article about this somewhere. In any case, they are generally limited to drag and sprint use.

Ring tension isn't what makes piston rings ring seal, pressure is what makes them seal. The ring tension is mainly used to force the rings in place; for instance, during the compression stroke friction caused by the ring tension working against the cylinder wall and the inertia of the ring force the ring to the bottom of the grove in the piston, allowing gas from the cylinder to pass over the ring due to the side clearence to the back of the ring. Well in place behind the ring the gas pressure forces the ring outward against the cylinder wall aswell as downward. In pro stock (which is by the way not using that high cylinder pressures; probably not much beyond 100 bar), since the engines doesn't need to last that long low tension rings can be used with gas ports instead. With vertical gas ports we can reduce the side clearence as the gas simply can reach the back of the ring through the vertical ports. As pressure build up in the cylinder the rings will be forced against the cylinderwalls, but when the pressure in the cylinder is low the seal aswell as friction is low.

I may very well be wrong on this point, but I was under the assumption that Pro Stock motorcycle and car engines were running the highest cylinder pressures of any normally aspirated gasoline engine. If I am wrong, then please let me know what engines run more cylinder/combustion pressures.

As for ring seal, a bit of light reading http://www.vtt.fi/inf/pdf/tiedotteet/2002/T2178.pdf

I am just sitting back and waiting for the propellor to start spinning.

Sorry if you took this for a snide remark, I sincerely want to know.

F1 engines run cylinder pressures of about 100 bar, but due to large cycle-to-cycle variations certain cycles may reach as much as 120 bar. Pro Stock cylinder pressures may be somewhat higher due to slightly higher compression ratios, but probaby not that much.

NA engines in roadcar applications see as much as 90 bar, and among turbo engines pressures as high as 120 bar are seen. Among common rail diesels pressures up to 170 bar are common and with commercial diesel engines high output versions may see up to 200 bar.

What would your estimate be for peak cylinder pressure in the Audi & Peugeot LMP1 diesels?

A few years ago I studied the NA gasoline vs. turbodiesel equivalencies using an assumption of 200bar peak pressure for the diesel. The current rumoured performance of the Audi & Peugeot suggests I underestimated somewhat...

Regards, Ian

140-160 bar probably. They are rumored to run rather low compression ratios and peak pressures to keep the engine as light as possible.

Production V engines with peak pressures around 170 bar tend to use compacted graphite iron cylinder blocks with aluminum heads and commercial engines with 200 bar peak pressures are all iron engines with steel pistons.

The stress put on a V-block by combustion pressures are higher compared to inline blocks.

Interesting. I modelled the textbook diesel cycle and had to push up the P2/P3 pressure to the 200bar range to get the kind of work levels I expected.

So then, any idea what rpm the LMP1 diesels run to?

Regards, Ian

Torque at the wheels is nothing more than horsepower times a constant for a given speed. If you have more torque at the wheels at a given speed, then you have more horsepower, that's a mathematical tautology.

That was a while back. These days open pressure is in the range of 1420-1450 lbs. These are triple-element, damperless springs.

The valvetrain on these engines is sort of interesting... cam lobe lift is in the neighborhood of .575 to .590 inches with a 1.80/1.85 rocker arm. So on paper the net valve lift is over an inch. However, if you put a dial indicator on the retainer and roll the engine over by hand, you will see less than an inch of net lift at the valve. That's because the mammoth valve spring is bending the valvetrain components and cylinder head deck. But when the engine is running (9200-9500 rpm peak hp) the net valve lift is restored to something over one inch due to valve toss aka lofting.

Obviously, if the valve is no longer following the rocker arm, then the rocker is no longer following the pushrod, the pushrod is not following the cam follower, etc. It's a series of controlled collisions. If you take this whole glorious mess and run it up on the Spintron, after around 90 seconds or so at 9500 rpm an entire symphony of resonances set in and it machine-guns itself to death.

Two years ago I was told that valve spring pressures were in the 1250-1350lbs range and valve lifts in the 1.1-1.15in range were beeing tried. Since my info was two years old and hearsay, I did not want to give hard numbers. But I guess it has not changed much and the info I was given was pretty accurate. But I think you will find that the difference in theoretical to practical lift is caused by poor rocker arm geometry at these extreme lifts and not by material deflection. Two years ago these engines were turning 10200-10400rpm(supposedly) through the traps. If there were close to .100in in deflection caused by the valvetrain at no rpm, could you imagine what it would be at 10000rpm? And if the valves lost control over the nose(valve loft), then chances are you would not be able to regain control until it bounced off the seat a few times. Therefore either the valve springs are too weak, or the cam profile is bad.
Did the spintron info say what temperatures the valve springs got to after 90 seconds? I bet that part of the reason for the loss of control after extended run time at 9500rpm was extreme spring temperatures causing loss of pressure.

Someone on this BB mentioned that float in some engines was by design. A cheap kind of VVT.

Ferrari for one worked on a ballistic VVT for a while. Desmo is our point man on that story I believe.

Conventional lobe profiles may incorporate valve lofting but it is not so much by design. If you can't eliminate it, might as well accommodate it.

No.

Yes....a circle with centre 42nd St, 5th Ave consists of all points that can be reached exactly one block from there....41st St, 4th Ave is 2 blocks away, so outside your circle.



No, because half way from one point to the next point you are at a point that is further than one block away from the centre, hence outside your circle. That's like saying that I can measure the 'circumference/perimeter' of the M25 between the M11 and M1 junctions by driving up the M11, across the the M1 and then back down to the M25 again.



Again, the streets and avenues that connect them are not part of the circle, as they are more than one block away from the centre.



No it doesn't actually. A square is not rotationally symmetrical about every angle - think about it, if you rotate a square 5deg, it does not overlay the original square anymore. A sqare is also not reflectionally symmetrical about a line through its centre from a third of the way along one side to two thirds of the way along the opposite side.

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I think they run to 4500 rpm or something like that.

An ideal cycle result in much higher peak pressures than a real cycle. The cycle you link to is also a constant pressure cycle, usually the seiliger cycle is refered to as the ideal diesel cycle. Seiliger is a constant volume (premixed) and constant pressure (diffusion) cycle during heat addition.

At high load though, the real diesel cycle behaves much like the real otto cycle. But unlike the otto cycle the heat addition phase becomes longer and longer with increased engine speed and there are no cycle-to-cycle variations.

At low load there is a pressure peak early during combustion, after which a second pressure peak will follow. This early peak is due to premixed combusion. During the premixed combustion there is a rapid pressure rise in the cylinder (this part is generally considered to be heat addition during constant volume). With higher loads the ignition delay goes down, leading to less premixed combustion.

Through the diffision flame period the combuston is ideally considered to be heat addition during constant pressure, but the pressure in a real diesel engine is hardly constant. Generally a diesel reaches pmax quite early, at 5-10 degrees after TDC after which the pressure decrease. Fuel injection generally start within TDC and about 10 degrees before and the injection duration increase with load up to about 30-40 degrees during normal operation.

We're back at the BBQ.

Hey, your photo has a fnord in it. You have been brainwashed by the Pythagorean Conspiracy.

Fucking commies.

Not really relevant to the topic as it doesn't involve a 2008 F1 car, but I have some official speed trap times from Adelaide at the end of Brabham Straight.

1986
326 km/hr Nigel Mansell - Williams Honda

1993
296 km/hr Damon Hill - Williams Renault


Despite the 7 years of technology advancement and the barn door rear wings of the 1980's cars, they still were a good deal quicker at the end of the straight.


But surely a no brainer, a 2008 car would blitz any 1980's car.

The point is that a circle is NOT defined as "rotationally symmetric." (Circles are not rotationally symmetric except in Euclidean geometry.) Instead, a circle is defined as consisting of all points at a constant distance from its center. Therefore a circle depends on how distance is measured. And in the "taxi metric" a circle indeed has the shape of a square.

In an x-y coordinate system, the distance from the origin 0 to a point with coordinates (x,y) can be measured by

d = |x|+|y|

This is a valid distance notion (the "taxi metric"), as it is non-negative, homogeneous, and satisfies the triangle inequality. That's all that is required.

And in this distance, a circle of radius 1 looks like a diamond (a 45 degree angled square). Note that the point (1,0) is on that circle, so is (0,1) and (0.5, 0.5). All have distance 1 to the origin. Plot those points. They're not located on that Euclidean rotational symmetric circle, right?

Fascinating stuff. My take on the restoration of lift as the RPM's increase is - increasing valve inertia at peak lift accounts for an increasing proportion of the spring force - therefore there is less spring force available to deflect/bend the valve-train components - therefore lift increases towards the theoretical value. It doesn't necessarily follow that there is a gap somewhere in the valve-train (lofting, float...) until actual lift exceeds theoretical lift. I did say "necessarily" because the system is very complex with inertias and springs everywhere so only Spintron testing will show when and where lofting actually begins to occur.

After reading this for 20 min it all boils down to one thing.So called dyno figures really mean diddly squat. A 1400 hp F1 engine [on a 1000hp dyno?] really is theoretical numbers and the engine life is about 2 minutes of power.
A Top Fuel engine is god knows how many [lots!] and is lucky to last 5 seconds of power.
A Nascar engine is supposedly around 800 hp [with a 4bbl carby] and a good 410 Sprintcar engine is maybe a little more both based on a similar engine. One lasts 500 miles, the other lasts a 100 but is about 5 times as driveable.
These numbers mean nothing except for bullshitting at the pub.
In my circuit racing my 530hp Chev engine would drive by the 600hp 2 litre Turbos normally in cars of similar weight and mine was less aerodynamic.
Even when they would come up behind me, baulk them off a slow corner and you would not see them again for ages as they lost so much momentum.
That is why the normally aspirated F1 cars with lots less horsepower were always competitive on race lap times. It is just that they did not have the power for 1 banzia qualifier to grid well.
Plus the turbos were bloody unreliable and very thirsty. And with all the ancillarys quite heavy too.

The dynomometer is by far the most valuable tool in engine development. However, the putative dyno figures thrown around on message boards like this are mainly baloney. Also the way they are commonly interpreted. We could start with what is a dyno, how does it work, and what do these numbers mean. It would make a good thread.

I agree, and the power band needs to be mapped as a lot of these huge numbers are on lightswitch, handgrenade engines which are so hard to drive as to be raceworthy.
Ofcourse it helps if you have 7 speed gearboxes with 500-1000 rpm drops on upchanges.
Less gears, more torque and driveability required.

How much has transmission technology improved since the turbo era? I wonder whether current transmission technology in a turbo era car would help much with the driveability problem?

OK - you post your definition and I'll dispute it. Or would you prefer I start it?

(Tongue firmly lodged in cheek)

MEGABUMP!!!

Here's something I like to know, how much faster would modern F1 cars be with turbos?

Depends on how much extra hp it gave them.

I think the difference between NA and Turbo would be similar to what it was back then - assuming 2:1 capacity penalty ie 1.2 litre turbo. That is to say - quite a big power difference in qualifying trim and not much in race trim.

Considering the current F1 are traction limited to fairly high speeds, putting a lot more power in would not help much by itself. The big advantage would be the possibility of increasing downforce (at the expense of increased drag) although I am not sure how much would be possible given current aero rules.

With a 1.2 litre turbo built to the same general specifications, a 98 mm maximum bore, 18,000 rpm maximum speed, four poppet valves per cylinder the naturally aspiranted engines of twice the displacement wouldn't have a chance to compete in terms of lap times.

The cars run almost maximum downforce at all tracks these days due to the reduction in downforce but the cars are only traction limited to 150 km/h or perhaps even less these days. We can see what the 80 hp from KERS do in terms of performance.

There never was the slightest logical basis for the 2:1 displacement equivalency formula. It seems to assume that if a normally-aspirated engine can pump one atmosphere of air, a boosted engine of identical displacement can pump two -- at best, a loose empirical formulation based on relative performance potential when the rule was written. In fact the boosted engine can pump three, four, or more atmospheres. If the FIA ever did an F1 equivalency formula again, which is a weak idea to begin with, it should be based on potential air consumption rather than physical displacement alone. For example, 3:1 equivalence for 3 atmospheres of manifold pressure, etc. That's the only rational scheme. Otherwise the turbo engine is simply handed an absurd advantage.

LOl I'd love to see a .8 or .6L formula!

The turbo engines would be more driveable today also. Wider power bands courtesy of VTG and better electronic management - no more light-switch engines.

There never can be a logical basis for NA/FI equivalency. It will always depend on the prevailing technology. Before Renault came along the 2:1 formula favoured NA. During the early Renault days it was about right and from then on favoured the turbos. You can probably say the same for Four Stroke/Two Stroke and Piston/Wankel equivalencies.

IIRC the Grand Prix equivalency was 3:1 (4.5 litre/1.5 litre) for some time.

A manifold pressure based formula would always favour NA unless the equivalence ratio was less than the manifold pressure ratio.

I favour restricting fuel rather than air. Efficiency suddenly gets a much higher priority and capacity/RPM/boost restrictions all become irrelevant.

Fuel flow.

Yes thats correct.

There will always be those who complain regardless. Even in spec series there are classes.
There was in the 50s I believe a 2.5 NA vs. 0.750 SC.