F1 Piston Analyzation

[kradicke]

http://members.atlasf1.com/desmo/pistoncrown.jpg

Any idea what the mushroom shaped "pad" in the center of the piston i for? My first guess would be for a Saab style Spark-to-Piston setup, but it seems awful wide for this purpose. Any better guesses would be appreciated.

More pics:

http://members.atlasf1.com/desmo/pistone.jpg

http://members.atlasf1.com/desmo/pistone2.jpg

Thanks! Kai

 

[kradicke]

Also, I'll add, that the piston i out of a 049 Ferrari V10... which makes about 4-5 years old I believe.

 

[Retracnic]

Without knowing the shape of the corresponding combustion chamber, any comment I have should be filed under the category of 'speculation'.

First, I agree that this is most likely not a spark-to-piston setup. As the contact pad is far too low and wide. Also I do not believe a spark-to-piston ignition system could provide the spark advance required to generate 18,000+ RPM operation.

As a guess, I'd say it's for either piston face cooling or structural reasons. It could be used for better flame kernel propagation during combustion, but I can't say for sure without looking at the CC. Be interesting to hear something from a Ferrari aficionado.

The only semi-recent* F1 engines I've seen the inside of were the Benetton 'Playlife' FB02 (long block and internals, no manifold or induction) and the Mugen-Honda MF 301HE (complete engine minus electronics). I do believe these engines were run during the same time frame as the Ferrari 049. Which would be around the 1999-2000 era. Though these engines ran pistons of similar overall proportions to the Ferrari pics you provided, each was doing it's own thing when it came to piston faces.

BTW – if you have any more pics of F1 internals, I'd absolutely LOVE to seem them.

*In Formula 1, the word 'recent' means you saw it at the Friday practice session before the race. Otherwise it's old news.

Regards,
Bryan Carter

 

[Marquis]

I've seen the internals of a few fairly current Formula 1 engines.
I thought I’d share my thoughts-substantiated educated speculation.
Looking at the Ferrari piston shown I'd simply say that the engine is over square-savagely so by modern production road car standards. Now anyone who has tried to develop an oversquare engine and tried to get the compression ratio high, will sympathise with how difficult this can be while trying to use as flat a piston as possible.

Shallow combustion chamber valve angles help, but due to the constraints this puts upon valve area and/or port flow/bore shrouding this isn't always ideal.

I would say that on a formula 1 engine the priority for good breathing is an extremely high priority-so valve area and good port low are of the utmost priority.

So to put this all into perspective, we’re left with a very oversquare engine with quite a deep combustion chamber valve angle (substantiated educated speculation).
Add to that the need for this engine to rev to phenomenal speeds-making valve timing criticial.
This would mean a late IVC point and decent overlap (goes hand in hand with the tuned exhaust for good scavenging). So now we’re left with big valves with quite a large included angle, open for a big duration-especially when the piston is a TDC.

Hence the need for HUGE piston cut outs-to avoid piston to valve cut outs. Which means the only option to get the compression ratio is up is to make protrusions as shown in the piston crown.

 

[Retracnic]

Marquis wrote:

Hence the need for HUGE piston cut outs-to avoid piston to valve cut outs. Which means the only option to get the compression ratio is up is to make protrusions as shown in the piston crown.

I had thought along similar lines, and it is a very valid point. The thing that troubles me is that other F1 pistons I have seen appeared to be relatively flat, save for the valve cutouts, there were no surface protrusions.

From looking at the piston crown we can get an idea of the depth of the chamber and make estimates about the included angle, but other than that I won't speculate further. It's sort of like looking at the quench pad of a specific piston; it doesn't make a lot of sense until you see the combustion chamber that it's mated to.

All-in-all, I'd probably say Marquis is correct.

Regards,
Bryan Carter

 

[PhxDesLtd]

The "pad" that you see on the crown is simply there to fill space. In engines in which the archetecture is extremely oversquare such as Formula One (~2.3:1 bore-stroke ratio), it is VERY difficult to achieve the necessary compression ratio (which is rumored to be in the regions of >13.0:1) so the crown reflects that in its sculpted nature.

Ryan

 

[EngJW]

Could this just be left over metal from machining? Sometimes pistons have a knob in this area where a center is put in for holding the piston in a lathe. After the turning operations, the knob is cut off flush with the top of the piston. In this case there are deep valve pockets so only a part of the piston top is flat.

John Woodward

 

[Marquis]

PhxDes ltd

I believe I said that

 

[zimbali]

Let me share my opinion as well,
I think besides all the issues went so far, it could also help to have more turbulant charge. If you think how the charge(air fuel mixture, or just fuel in DI tech) faces the piston and reflects back, you will get this idea that this piston shape gives the charge more turbulance which help better fuel ionization and it finally leads to more efficient combustion.


Cheers


You can live in your car, but you can't drive your House!

 

[ZoRG]

It could also be to speed up flame travel on combustion, this is essential for good power at incredible rpm's.

 

[htwls]

If my opinion/experiences account for anything, I am leaning towards a design that gives a controlled amount of turbulance and increased burn rate. Part of the problem with F1 engines and their extremely high piston speeds is flame travel. F1 engines and their amazing piston speeds have been known to actually out accelerate the flame front in the cylinder. Since the high octane levels of the spec fuel (gasoline) must be used the engines are designed around extremely turbulent yet controlled states of combustion. One of the reasons for this is to get the engine to fire and actually idle. These engines idle at a significantly high rpm and still relatively low amounts of manifold vacuum. F1 engines still have to get the car around the track with the broadest powerband possible, not just infinite horsepower at extreme rpm levels. If you talk to engineers they work harder on tractability and longevity rather than maximum horsepower!!!

 

I agree with HTWLS,

If you look at the piston it's pretty clear from the burn pattern that the combustion is happening in the two valve relief "troughs" on either side of the flat area in the middle.

 

[Andy330hp]

I thought it was shown in other posts that, with thier miniscule strokes, piston speeds were only barely outside the realm of high performance street cars even at 18000 RPM?

 

[ZoRG]

Andy, those are average piston speeds, however if you look at piston acceleration it is a different story.

 

[Andy330hp]

Okay, so which really influences flame front speed? I thought (again, from this board) that flame front speed was affected by piston speed, not piston acceleration. htwls' post is confusing for that very reason: he refers to each, as if they were the same. THey're RELATED, but not the SAME. You could have high speed but low acceleration in a long stroke truck motor, but low speed and high acceleration in an S2000. It also possible, by running them at (drastically?) different points, to make their piston speeds or accelerations equal.

IF you built two engines with identical combustion chambers, bores, etc, but different rotating assemblies for different strokes (crank, rods and pistons with same crowns but diff wristpin locations), at which intersection (same mean speed, or same mean acceleration), would thier flame speeds be approximately the same?

I know it's complex problem, so make the appropriate assumptions...