Superpolishing / Superfinishing

[Superdunc]

Big yes to Smokey Yunick's books, and also a big yes to Gordon Blair's 'Design and Simulation of 4 stroke Engines' [Kinda like a bible this one, bit maths heavy in places but defo worth the read]. Don't think I've ever read any of bell's so ill take a look now.

Ive spoken a bit with Rudiger Kamna (ducati dealer/tuner as well as aprilias etc. in germany), and he recommends a squish clearance of 1.00mm for Ducati engines. [As you have run many Ducatis, what do you use Superdunc?]

I've only done the one Ducati motor. The Ducati Corse manual for the 996rs motor specs 0.97mm -1.05mm, my engine runs 1.12mm from memory, i chickened out of machining the barrels as the compression ratio is already at 14/1, but I am running bp valves and cams which restrict volumemetric efficiency.

[Annaz]

Very interesting thread this.

Surely a polished surface is going to generate less drag/friction than a rough surface. This will make any operation of movement more efficient leading to better fuel economy and less frictional loss would mean less stresses during operation. I've no idea what likely performance gains there would be but it seems to me the reliability of the motor would be better, which would be ideal for endurance situations. Probably

[Marb]

Problem with superfinished inlet tracts is that the fuel in the mixture tends to "condens" onto the sides of the inlet tract. Therefore buggering up you mixture. Leaving a a bit of a rough surface will cause the fuel and air to keep mixing due to the turbulence crreated. However, have a surface that is too rough and indeed you create drag.

[speedy sie]

the xro9 engine i have has the removable inlet trakets ,but the finish is almost a very fine sand blast finish,and im sure they still use this finish on the uptodate suzuki race engines.

[Superdunc]

Problem with superfinished inlet tracts is that the fuel in the mixture tends to "condens" onto the sides of the inlet tract. Therefore buggering up you mixture. Leaving a a bit of a rough surface will cause the fuel and air to keep mixing due to the turbulence crreated. However, have a surface that is too rough and indeed you create drag.

Certainly true on Carbed engines, not quite so big an issue on Fuel injected ones as the fuel is much better atomized, still a consideration though.

[speedy sie]

can you keep the words to two sinables........................

[kaighn80]

dont forget with regards to inlets that turbulent air moves faster than non turbulent, same as airplane wings, its not the air being forced under that gives lift its the speed of the air over the wing that effectively sucks the wing upwards, like how an airbrush (the cheap ones with the little glass jar at the bottom) gets the paint out.

[thefatman]

Think golf balls!

Smooth ones don't fly very fast, dimples send them further. Its been a long time since i've done boundary layer effect, the bernoulli equation so you can work out unknown factors without knowing them, makes your brain hurt.

[theo]

Although golf balls do fly further due to their dimples (which causes flow seperation to occur later, further back, and hence a smaller wake being produced), this is not the case for pipes, as the frictional effects due to surface area dominate.

I had to do something on this during 2nd year thermodynamics which ill dig out....

[blow_away]

Check out the big brains on the PB forum

So the short answer is that the benefits of superfinishing is still to be proven?

A couple of asides;

I can't remember who was saying it, but a well respected bike tuner back in the 1980's (I think it was Pip Higham) wrote that inlet tracts should be left rough and not polished smooth. This was to create a "disturbance" in the gas flow, and stop the air and fuel from "separating" <apologies if "these" are not technically correct terms in this context>

Superdunc, what you are saying about oil sticking to the crank reminded me of the drag racing days. After a few crank failures when we were using Z1/GPz1100 engines, we (Tim Blakemore) switched to using the Kendall oil that the car guys were using. This stopped the crank failures, and it was obvious why when you stripped the engine - the oil was quite "thick" and would be stuck so well to the crank surface that it was hard to wipe away with a rag. Gawd only knows what that did to the crank weight, but as we were revving much lower than modern engines I guess it would be too serious an issue. Be grateful for modern oils.

[theo]

I'm also a lover of thermodynamics (doesnt sound right....) but 5th year thermo is getting killer.

When I find the thing about flow over a golf ball and how it compares to internal flow ill post it up.

[kaighn80]

thermodynamics? dont that explain why red cars/bikes are faster than other colours due to the way they dissapate heat? same as black computers being faster than white ones!

[theo]

Ok so, Im going to write this down before I forget it.

I briefly went and quizzed head of engine development at uni, a guy with a massive amount of both empirical and theoretical knowledge. Any errors are mine, and my misinterpretation.

Carbon Deposits:

During operation it is desirable to have absolutely no carbon build up in the combustion chamber. Carbon is a very good heat conductor (counter intuitive?) , and petrol companies deliberately include addatives to the fuel to prevent carbon build up.

Port Finishing.

There is a trade off to be made between volumetric efficiency (how well a cylinder is filled) and turbulence generated. High turbulence is desirable as the higher this is, the higher the speed of combustion. Therefore although a polished port would create a higher volumetric efficiency (mass flow rate etc.), some of this is sacrificed in the quest for high charge turbulence, and also to ensure a homogenous fuel/air mixture (as to start with there is pire fuel at the injector nossel, and pure air being inhaled which must be mixed together).

This is why some F1 ports are not mirror finished but instead are left very finely machined. The patterns/surface finish is dependant on many factors, and will change for different injector/trumpet configurations.

[theo]

Just an addition to what we were talking about, found in November 2010 Race Engine Technology.

'We noted in our Toyota profile how porting and combustion chamber design have moved away from the classic concept of tumble swirl. At 18,000 RPM there is enough turbulence generated to dispense with tumble, which saps energy from the flow. Even at 18,000PRM, however, it has been found that the superior air-fuel mixing that tumble promotes can enhance fuel consumption, albeit at some cost to top end power'

[Marb]

So if i understand correctly, they are saying the the corse finish on the inlet tracts will cause the engine to run too rich at really high rpms, (enhance fuel consumption without power gains)?

[cagimaha]

As I understand it the "mixture" as such remains the same. That is to say the intake charge has the same amount of fuel and air in it in both cases. The higher turbulence example (with "rough" ports) has the fuel mixed better with the air resulting in a more even distribution throughout the combustion chamber meaning that for x amount of fuel consumption more energy is released. The downside is that there is higher pumping losses due to the extra friction generated.

[theo]

So if i understand correctly, they are saying the the corse finish on the inlet tracts will cause the engine to run too rich at really high rpms, (enhance fuel consumption without power gains)?

I dont think that an F1 engine will ever be running 'too' much of anything. With the money they can throw at the development, Im sure they wont be overfueling the engine, and the engine management will be contolling and updating this constantly.

It seems it might be feasible that they are sacrificing some top end grunt to gain some fuel consumption advantage given by the increased turbulence generated by the rough(ish) port finish).

With an advantage given by being able to run longer on a set amount of fuel (or running less fuel mass at the start of the race).

It would be interesting to try two identical engines (one with mirror porting and one with this slightly rough finish) at speeds that are not F1 level, say up to 14,000RPM. It would be my guess that the volumetric efficiency advantage of the mirror port would override the advantages given by the rougher port, especially as most everyone here wont be chasing fuel economy over power production.

[Marb]

I dont think that an F1 engine will ever be running 'too' much of anything. With the money they can throw at the development, Im sure they wont be overfueling the engine, and the engine management will be contolling and updating this constantly.

It seems it might be feasible that they are sacrificing some top end grunt to gain some fuel consumption advantage given by the increased turbulence generated by the rough(ish) port finish).

With an advantage given by being able to run longer on a set amount of fuel (or running less fuel mass at the start of the race).

It would be interesting to try two identical engines (one with mirror porting and one with this slightly rough finish) at speeds that are not F1 level, say up to 14,000RPM. It would be my guess that the volumetric efficiency advantage of the mirror port would override the advantages given by the rougher port, especially as most everyone here wont be chasing fuel economy over power production.

I find it a little hard to believe that F1 are sacrificing power (which at F1 they spend 100's of thousands for 3 extra bhp) just to gain some fuel consumption? Why would they sacrifice power? I doubt that they mind if they use 1ltr a lap or 1.1 ltr a lap if they can increase the power by a couple of BHP.

But then again, it could be very possible. If the powergains are in the area of 0.something BHP as opposed to using 100ml more fuel a lap. Which means that they can start a couple of kilo's lighter at the start of a race.

[theo]

I find it a little hard to believe that F1 are sacrificing power (which at F1 they spend 100's of thousands for 3 extra bhp) just to gain some fuel consumption? Why would they sacrifice power? I doubt that they mind if they use 1ltr a lap or 1.1 ltr a lap if they can increase the power by a couple of BHP.

But then again, it could be very possible. If the powergains are in the area of 0.something BHP as opposed to using 100ml more fuel a lap. Which means that they can start a couple of kilo's lighter at the start of a race.

How about the Red Bulls running out of fuel as they complete the warm down laps (or even hearing on the radio to conserve fuel if the lead is sufficient) or even rossi running out and having to return on the back of a truck.

Im sure that fuel consumption (and the weight they carry at the start) is every bit as important as the peak power output.