What Is the Ideal Cylinder Head Material for Maximum Horsepower?

[J.A.W.]

Funnily enough, re: T-C's mention of the still interesting Napier Lion design of nearly a century ago..
..featuring such current standard tech as DOHC 4V.. tapered ports.. hollow valve stems.. slipper pistons..
.. 'billet' cylinder liner, that at the top, also formed the combustion-chamber, through which the valves seated..
.. & on to which - the liquid-cooled.. enclosed lube.. gear-driven.. DOHC 4V.. Al head - was fixed.

See here: http://collections.museumvictoria.com.au/items/1720829

& drawings here: http://archives.imeche.org/archive/engi ... tyPhoto10/

The Lion was successfully developed from an N/A ~400hp bomber mill turning ~1,500rpm.. for ~100mph..
..to a supercharged race engine reliably pumping out an additional ~1,000hp @ ~3,500rpm.. for ~400mph..
..& good enough to hold the piston engine/wheel driven/outright LSR up 'til the 60's.. so, not too shabby..

[Tommy Cookers]

Slightly off-topic. Can anyone confirm whether all teams use a bolt-on cylinder head? The high cylinder pressures and near-detonation operating point may benefit from an integrated head/cylinder design.

for some reason I have the idea that integrated construction was banned via the N/A engine freeze and is still banned
(BMW used it to make a shorter, lighter F1 engine, ie having closer bore centres than possible with seperate construction)
the current F1 mandated bore centres (relative to the mandated bore) are notably conservative

[riff_raff]

I remember 15 or 20 years ago when ceramic thermal barrier coatings were first tried on the combustion chamber surfaces of race engines. I recall reading about the results of testing an Indy engine that had its cylinder head chamber/deck surfaces, piston crowns, and valve faces sprayed with a thin layer of ceramic TBC. There was no appreciable increase in power noted, but there was a measurable increase in EGT. So the conclusion was that the reduced amount of heat being transferred to the oil and coolant was mostly going out the exhaust rather than contributing to the work performed by the pistons. To make efficient use of the extra energy in the exhaust gas would have require turbocharger modifications that were not allowed in Indycar racing. However, the TERS used in F1 would be perfect for this task. Unfortunately, ceramic materials like TBC's are not currently permitted in F1 engines.

[trinidefender]

I remember 15 or 20 years ago when ceramic thermal barrier coatings were first tried on the combustion chamber surfaces of race engines. I recall reading about the results of testing an Indy engine that had its cylinder head chamber/deck surfaces, piston crowns, and valve faces sprayed with a thin layer of ceramic TBC. There was no appreciable increase in power noted, but there was a measurable increase in EGT. So the conclusion was that the reduced amount of heat being transferred to the oil and coolant was mostly going out the exhaust rather than contributing to the work performed by the pistons. To make efficient use of the extra energy in the exhaust gas would have require turbocharger modifications that were not allowed in Indycar racing. However, the TERS used in F1 would be perfect for this task. Unfortunately, ceramic materials like TBC's are not currently permitted in F1 engines.

Were they not allowed to use a larger turbine for reduced back pressure? More heat in the exhaust would mean that a higher flowing turbine can still have the response of a smaller turbine running with cooler (lower energy) exhaust gas.

Secondly the TBC coatings should allow the team to use smaller radiators as less heat is required to be removed from the block and heads.

n.b. the use of the words "large turbine" and "small turbine" are in the most general terms here. I am aware that there is a lot more to it than just the physical size.

[riff_raff]

Turbo response was not a concern with Champ car engines. They ran very modest boost levels that was limited by an intake manifold pop-off valve. No intercoolers were allowed. And the single turbocharger used on the 2.65L methanol V8 engines had a titanium turbine and magnesium compressor wheel.

[Vortex347]

Hi,
In my opinion you'd want to stray away from both aluminium and steel heads.
As correctly said:

Mike Downs of Trick Flow Specialties, Tallmadge, Ohio, pointed out that the thermal conductivity of aluminum is “four or five times that of iron. This means an iron head will usually operate hotter. On the positive side, this means the fuel is pre-heated in the intake runner and easier to ignite in the cylinder.

The heat containing abilities of iron might be good if your operating a low octane fuel but anything above 90 octane shouldn't need to be hot to compress and also the heat would lead to air expansion in the chamber (due to it being a gas) which would defeat the point of turbocharging the current f1 engines (compressing the air with the turbo then uncompressing it in chamber- no way).

Heat is the enemy of a lot of things on engines (just look at what they did to the turbochargers on the v6's to avoid heat build up and hence eliminate the need for an intercooler).

Aluminium hmm yeah durability has never been a strong point, though heat venting properties are good (mainly due to it's lower density).

http://www.gizmag.com/stainless-magnesi ... ash/28856/

^This would be more along the lines of a better material for cylinder heads and the block too

reasons being: light, durable and possesses an even better thermal expansion coefficient than aluminium to dissipate heat faster.

Ultimately I think the cooler you can operate an engine the better

[gruntguru]

That makes me to think a little further on the topic. You need to define "Maximum Horsepower". Under the current F1 rules, "Maximum Horsepower" means "Maximum Efficiency". Heat loss to the cylinder walls is bad for TE so cast iron might make more power than aluminium.

Vortex. Some problems in your post.
"just look at what they did to the turbochargers on the v6's to avoid heat build up and hence eliminate the need for an intercooler"
(Unless you are referring to some other V6) all the current engines run intercoolers.

"Ultimately I think the cooler you can operate an engine the better"
Under the "fuel efficiency" formula, running too cool will cost horsepower.

[J.A.W.]

An 'economy run' for maximum efficiency on strictly rationed fuel dosage.. is not about "maximum horsepower" is it though, gg..

By G.P. racing contrast, the final iterations of simple & powerful ( if 'inefficient' fuel-wise) N/A 2T bike race mills
did run very cool indeed, for comparison.. @ ~ 1/2 way to the boiling point of their coolant ( straight water)..

[gruntguru]

Jaw - (disregarding the 100Litre race limit) the 100 L/hr flow limit is not an "economy" measure - it is a power limiting measure. The engine with the best fuel efficiency will make the most power.

Most other formulae limit power by limiting airflow, either directly with a restrictor or indirectly with limits on capacity, rpm, boost pressure etc etc. The engine with the best air efficiency and/or breathing will make the most power.

The technical challenge is similar.

Back on topic. Perhaps aluminium is the better material for an airflow limited formula and cast iron is superior under a fuel flow limited formula?

[J.A.W.]

Sure gg, since air is effectively free, & conservation of a strictly limited fuel ration by means of heat efficiency..
(the current F1 slant) by crowding the parameters, does tend to indicate just such a material continuum view..

Albeit use of the 'neolithic' Fe/stove material - as an F1 G.P. racer's cylinder head..
..would surely be a glaring anathema - to any forward thinking race engineer..
..with a decent development budget.. even if under the currently cruel constraints of real tight technical reg's..

[strad]

Ultimately I think the cooler you can operate an engine the better

Hmmmmmmmmm I think that is wrong.

[trinidefender]

Jaw - (disregarding the 100Litre race limit) the 100 L/hr flow limit is not an "economy" measure - it is a power limiting measure. The engine with the best fuel efficiency will make the most power.

Most other formulae limit power by limiting airflow, either directly with a restrictor or indirectly with limits on capacity, rpm, boost pressure etc etc. The engine with the best air efficiency and/or breathing will make the most power.

The technical challenge is similar.

Back on topic. Perhaps aluminium is the better material for an airflow limited formula and cast iron is superior under a fuel flow limited formula?

Then maybe cast iron liners and a cast iron "crown" in the combustion chamber to keep as much of the heat in the combustion chamber.

I have 2 questions then.
1. Considering that it has been hypothesised that these PU's run on the the edge of detonation with a certain limit allowable depending on engine life required, would this not be beneficial to run aluminium in this case to reduce detonation. I.e. There must be a trade off somewhere.

2. What can PU manufacturers do as far as thermal barrier coatings when it comes to combustion. What Is allowed? What parts can be coated? Pistons? Cylinders? Combustion chambers? Valves?

[J.A.W.]

Ultimately I think the cooler you can operate an engine the better

Hmmmmmmmmm I think that is wrong.

Certainly not regarding the exemplary posted tq/hp values of N/A 2T G.P. bikes, strad..

The ( ok, 'inefficient' fuel-wise) usage of fuel-based latent heat of evaporation for crankcase cooling..
..along with 'reverse' cooling loops - cool liquid from radiator exit - went to cooler components 1st, & then to hotter spots..
(conceptually a bit like the cool-cycle for sea-food, if you are familiar with that)..

The loss of this inherently advantageous characteristic was a factor that had to be addressed with ambient air temp DI 2T's..
.. which had to substitute that 'free' internal coolant system..
..with extra external liquid coolant - circulating in dedicated crankcase galleries..
.. & this is needful, to keep the fuel-air charge as cool as.. yeah.. for best/most - power output..

[gruntguru]

Ultimately I think the cooler you can operate an engine the better

Hmmmmmmmmm I think that is wrong.

Certainly not regarding the exemplary posted tq/hp values of N/A 2T G.P. bikes, strad..

The ( ok, 'inefficient' fuel-wise) usage of fuel-based latent heat of evaporation for crankcase cooling..
..along with 'reverse' cooling loops - cool liquid from radiator exit - went to cooler components 1st, & then to hotter spots..
(conceptually a bit like the cool-cycle for sea-food, if you are familiar with that)..

The loss of this inherently advantageous characteristic was a factor that had to be addressed with ambient air temp DI 2T's..
.. which had to substitute that 'free' internal coolant system..
..with extra external liquid coolant - circulating in dedicated crankcase galleries..
.. & this is needful, to keep the fuel-air charge as cool as.. yeah.. for best/most - power output..

I am sure all engines have a lower temperature limit where running "cooler" will cost power. In the efficiency based current F1, the best temperature for power is probably higher than typical for other race engines.

[godlameroso]

The heads are not virgin aluminum, that's for sure, the alloys are limited, but the proportions of what's allowed is not.

5.17.8 Static components :
a) Other than inserts within them, engine crankcases including sump and cylinder heads must be manufactured from cast or wrought aluminium or iron alloys.
No composite materials or metal matrix composites are permitted either for the whole component or locally.

Furthermore:
5.15.1 X Based Alloy (e.g. Ni based alloy) – X must be the most abundant element in the alloy on a %w/w basis. The minimum possible weight percent of the element X must always be greater than the maximum possible of each of the other individual elements present in the alloy.

So it has to be an Iron alloy, or aluminum alloy, you can have something be 51% aluminum, and 49% whatever else, luckily you don't really need such drastic percentages to alter the properties of aluminum or iron for that matter.

The final bit of restriction is this:
5.16.1 Unless explicitly permitted for a specific application, the following materials may not be used anywhere on the power unit :
a) Magnesium based alloys.
b) Metal Matrix Composites (MMC’s).
c) Intermetallic materials.
d) Alloys containing more than 5% by weight of Iridium or Rhenium.
e) Copper based alloys containing more than 2.75% Beryllium.
f) Any other alloy class containing more than 0.25% Beryllium.
g) Tungsten base alloys.
h) Ceramics and ceramic matrix composites.
5.16.2 The restrictions in Article 5.16.1 do not apply to coatings provided the total coating thickness does not exceed 25% of the section thickness of the underlying base material in all axes. In all cases, other than under Article 5.16.3(b), the relevant coating must not exceed 0.8mm.

Finally there's this:
5.16.3 The restrictions in Article 5.16.1(h) do not apply to the following applications :
a) Any component whose primary purpose is for electrical or thermal insulation.

It could be argued that a specific coating on the head is actually for the purpose of thermal insulation.