69 replies to this topic

[footprints]

I have been researching on some cylinder liner materials available in the market today.

Perfect bore offers nikasil coatings on their special steel liners. I believe they are supplying to some Winston cup teams.

Chrome plated liners. They are known to have surface hardness of beyond HV800 and are found in many diesel engines. Known to have very good wear resistance but how good are they for performance use and with forged pistons?

Boron alloy liners offers very good metallographic structure. Used in mercedes engines, again how good are they from a performance perspective?

These liners are all very strong and they are all supplied surface finished to the exact bore size requirement, ie no need to rebore or hone. Infact they cannot be rebored due to the hardness. But how well do they do in racing environments with high boost and high RPMs??

Ductile iron sleeves have very high tensil strength and are much cheaper. I would like to understand how they all compare to each other.

[J. Edlund]

Ductile iron isn't that common as a cylinder liner and cylinder block material. Most blocks/liners are made in grey cast iron, and compared to ductile iron, grey iron has a much lower tensile strength and stiffness while thermal and damping characteristics are much better.

Cylinder blocks for NASCAR seems to be made in compacted graphite iron.
http://www.competiti...no=3&issue_no=2

A coating such as nikasil provides an increase in wear resistance over uncoated liners/blocks, and is a must for aluminium liners. However, platings that contain nickel (such as nikasil) are sensitive against sulfur, so fuels with high sulfur contents is a problem.

[shaun979]

I recall seeing leading aftermarket Honda block sleeve manufacturers tout ductile iron

[dead_eye]

theres a lot of new materials coming out now aswell due to ceramic coatings making their use possible. theres been a few companys doing a lot of marketing in the last few years with coatings for exotic metals to either stop or improve heat transfer and allow hazardous or brittle metals like magnesium and aluminium alloys to be used in high performance engines. (aluminum berylium pistons for example).


Ive spoken to a few places about coating the sides of the rotors on my fd3 rx7 to try and stop some of the heat losses and the stuff that can be done when speak to the right people is phenomenal! You just dont hear a lot about it because its so expensive and banned in most forms of motorsport.

[J. Edlund]

Originally posted by shaun979
I recall seeing leading aftermarket Honda block sleeve manufacturers tout ductile iron

Ferrari F50 used a block of ductile iron, I believe the iron blocks used by Ferrari in F1 also was ductile iron. I would expect that most iron blocks used during the turbo years in F1 also was ductile iron, the Honda turbos sure used ductile iron for the blocks. These engines used wet liners though, and I have no information about what material was used in the liner.

Originally posted by dead_eye
theres a lot of new materials coming out now aswell due to ceramic coatings making their use possible. theres been a few companys doing a lot of marketing in the last few years with coatings for exotic metals to either stop or improve heat transfer and allow hazardous or brittle metals like magnesium and aluminium alloys to be used in high performance engines. (aluminum berylium pistons for example).


Ive spoken to a few places about coating the sides of the rotors on my fd3 rx7 to try and stop some of the heat losses and the stuff that can be done when speak to the right people is phenomenal! You just dont hear a lot about it because its so expensive and banned in most forms of motorsport.

Coatings are almost entirely used for tribological reasons only. Thermal barriers are very uncommon with a few uses on exhaust manifolds and in exhaust ports.

Thermal barriers are in general very sensitive and most of them are developed to be applied on superalloys, as they are in gas turbines. The gain given by a thermal barrier coating is small, in a gas turbine running at temperatures above 1000 degC you can perhaps gain up to 50 degC. In gasoline engines they aren't a good idea as the end gases are cooled by the piston and cylinder head during combustion, add a thermal barrier and what you end up with is detonation problems and a higher exhaust gas temperature. Diesels doesn't have that problem, but its use is only experimental.

As for most coatings they aren't especially new, most are just not the widely known. For example nikasil was introduced in 1967. Initially it was developed for rotary engines which needed to run the rotors directly against the aluminium housing. Nikasil isn't a ceramic though but a cermet. When Mazda ran on LeMans with a rotary they used a chrome carbide based cermet on both the rotor and side housings. This was used together with SiC whiskers reinforced silicone nitride apex seals.

Coatings also won't allow brittle materials to be used. Coatings can only allow materials with unsuitable tribological properties to be used. In all cases the substrate must have a certain minimum hardness on order to be used.

[footprints]

I know mclaren's ilmor blocks used aluminium liners coated by Perfect bore. It might be MMC materials, but they were special thin walled liners. As thin as 0.5mm thick if i'm not wrong.

How about chrome plated bores and boron liners? Are they good for performance engines?

[Greg Locock]

This being the technical forum and all, I wonder if we can make sense of a cylinder liner that is 20 thousandths of an inch thick?

I wouldn't like to have to push them in, if they were a press fit, and they'd yield under cylinder pressure, if they were a clearance fit.

So, they could have been a shrink fit I supose, or else a split block is an alternative, although the only split block I ever saw had wet liners.


say 4 inch diameter, say 500 psi for grins, that's a hoop stress of 4*500/2/.02, =50 ksi, or 345 N/mm^2

OK, that surprises me I thought it would be more. Is 500 psi reasonable?

[saudoso]

I may be saying some big BS, but I have been to a lecture at the company linked beloow where they presented the qualities of physical vapour depositon coatings for cutting tools and plastic injection moulds. Basically very hard and low friction.

See:
PVD

Would this be of benefit for engines?

Ricardo

[McGuire]

I have been to that party. A .5mm dry liner (as opposed to wet sleeve, to delve into the nomenclature) is possible, tho .70mm is more reasonable. To give everyone an idea, .5mm or .020" is about the thickness of an aluminum beer can. You have to heat the block and chill the liner. But with the platings and depositions now available I wouldn't think there is a reason to do it anymore.

[J. Edlund]

Originally posted by saudoso
I may be saying some big BS, but I have been to a lecture at the company linked beloow where they presented the qualities of physical vapour depositon coatings for cutting tools and plastic injection moulds. Basically very hard and low friction.

See:
PVD

Would this be of benefit for engines?

Ricardo

When it comes to the bore it must be capable of retaining oil, so just any coating won't do the trick.

As for physical vapor deposition, that's only one method availible to apply coatings. For cutting tools the most common process used is chemical vapor deposion which is better suited for mass production but PVD has other advantages.

Different coatings will be required at different places. For components like piston pins and cam followers DLC seems to be the most interresting coating given it's lubricating properties. For cylinder liners cermets or aluminum oxide seem to be the most common, cermets is also used to replace valve seat inserts while WC/C seems to be a possible piston ring coating. Phosfated pistons seems to most common piston coating, aluminumoxide in the ring grooves also is quite common. For valves CrN is a possebility given that it can be used in applications up to 700 degC.

Sometimes coatings are used, other times surface conversions are used instead. The latter means that the material in the component can be converted into something harder, for example aluminum can be converted into aluminumoxide and titanium can be converted into titanium nitride.

For coatings to work the substrate material must also have a certain hardness. If you look at high quality tools they are made of high quality tool steel or hardmetal and then coated. It's not possible to use a very soft substrate and a thin hard coating since as soon the loads will be high enough the coating will fail like thin ice on water.

[dead_eye]

j.edlund-

have you got an emil addy il try and get you the spec files on some of the coatings the companys ive been to are using. Some are fairly new (lst 10 years) others are just becoming availiable. however they are all already running in high performance engines and and a lot of test engiens with some top name race teams.

I understand what you saying about not changing strngth propreties ie you can coat titanium and expect it to last forevre as a conrod but they are allowing magnesium piston crowns to be used with no abrasion/dust problems and no risk of ignition. Its also out on the grape vine that bmw and a few other companys have been testing the coatings on their all magnesium blocks to protect the water jackets form corrosion so they dont have to be made from aluminium.

As for hotter running cylinder and exhaust temperatures, hot exhaust temps (in a performance world at least) are ideal increasing exhaust pressure and speed and in turn increasing the scavenging effect and if fitted turbo spool up (in my experience at least). And although hotter cylinder temps can cause detonation problems you need to remember that the heat kept in will increase cylinder pressure and thus power availiable as mechanical force so lower compression ratios and fuelling levels can be used.

In the case of the rotary engine theoretically its only 29% thermally efficient due to the massive surface areas of the rotors and the casing. if that can be increased by even 10% youd see a theortical power increase of 1/4 and possibly less fuel used to get it. Obviously real world figures will be a lot less startling as they always are but to me its got to be worth following up on- Il post once its being done and let you know the results

I cant and wont claim to know a lot about these coatings and what they can and can't do but ive seen engines running some of the newer coatings and on the pistons and cylinders etc and seen one experimental head in which the cams, valves and followers all run on a self lubricating coating resulting in no oil supply to the head. I doubt it will be to long given the current oil situatuion before it starts appearing on top end cars.

[phantom II]

What did the Chevy Vega have on it's bores? It was the first throw away block? I understand the P928 had the same coating.

Originally posted by J. Edlund



For coatings to work the substrate material must also have a certain hardness. If you look at high quality tools they are made of high quality tool steel or hardmetal and then coated. It's not possible to use a very soft substrate and a thin hard coating since as soon the loads will be high enough the coating will fail like thin ice on water.

[Hondanisti]

Metal Matrix Composites are in between nikasil dry liners and ferrous iron liners in terms of cost and weight.

The Honda NSX, S2000, and older Preludes ran with these matrix composite liners (in this case aluminum alloy re-inforced with a carbon fiber matrix), as did Toyota for their Celica GT engines now used in the Lotus Exige.

Is engine weight an issue for you ? (i.e. the need to have more flexibility of moving around ballast weight for CG location?)

As for who sells these in the aftermarket as cylinder liners ? No idea.

How many miles are you expecting to get on this rebuild motor ? That will dictate the decision as well.

[Engineguy]

Originally posted by phantom II
What did the Chevy Vega have on it's bores? It was the first throw away block? I understand the P928 had the same coating.

There was nothing "on" the Vega or Porsche 928/944 bore. The Porsche's Alusil is the same "Reynolds 390" technology used in the sleeveless aluminum Can-Am big block Chevys and the production Vega engines. It got a undeserved bad rap in the Vega engine but has been reliably used for decades in Porsche, BMW, Audi and Mercedes engines. It's NOT a plating or coating or anodizing process. The entire block is cast in a high silicon (hypereutectic ) aluminum alloy in which the excess silicon is present in the form of free particles. The bore is honed in a series of (Sunnen-supplied) steps to leave the silicon particles standing proud of the aluminum, leaving, effectively, a silicon bore. The pistons are usually (always?) plated (iron, tin, chromium, Nikasil) for compatabity with the hard bore (and, I suspect, to prevent galling with the bore's remaining aluminum matrix, although the final lap is supposed "wipe" the bore surface aluminum free).

The high silicon aluminum alloy is a bitch to machine compared to normal alloys, so a new take on Alusil used in all (all flat?) current Porsche engines is Lokasil... in which an Alusil alloy sleeve is cast in place so the rest of the block's surfaces have aluminum's traditional ease of machining.

Although you can bore and rehone Alusil/Reynolds 390 bores, you can also get thin (.100" wall) Alusil dry sleeves to get back to the original size.

I still like this technology... block and pistons of same (base) CoE for tighter cold AND hot clearances, no coating on the non-throwaway piece (hence the block can be bored by thousands of local shops), a 30 year track record of durability, and the block is monolithic... you're not cutting thickness out of its structure for seperate liners.

[McGuire]

There was some trouble with the Vega's cylinder bores (oil consumption etc) but nothing that couldn't be fixed. The real problem was with the block design itself. It was wet deck and the free-standing, linerless bores would sink in the case, losing the head gasket seal. GM developed a really elaborate laminated head gasket but it was only a partial fix.

Also, the cast iron cylinder head casting was way complicated (maybe should have been two pieces) and extremely prone to cracking internally.

But both these failures allowed coolant into the crankcase, and permanent antifreeze is death on cylinder walls. But it was not the fault of the Reynolds 390 concept.

[Greg Locock]

I think I can see the point - an all aluminium block with integral cylinders. Is that it?

It sounds like a difficult but worthwhile path to take.

[McGuire]

It is the future, though I think the Honda-Siffal method is the one. That is one solid deal, will go 250K miles with virtually no significant wear.

[phantom II]

Did cosworth fix the problems?

Originally posted by McGuire
There was some trouble with the Vega's cylinder bores (oil consumption etc) but nothing that couldn't be fixed. The real problem was with the block design itself. It was wet deck and the free-standing, linerless bores would sink in the case, losing the head gasket seal. GM developed a really elaborate laminated head gasket but it was only a partial fix.

Also, the cast iron cylinder head casting was way complicated (maybe should have been two pieces) and extremely prone to cracking internally.

But both these failures allowed coolant into the crankcase, and permanent antifreeze is death on cylinder walls. But it was not the fault of the Reynolds 390 concept.

[cosworth bdg]

Originally posted by McGuire
There was some trouble with the Vega's cylinder bores (oil consumption etc) but nothing that couldn't be fixed. The real problem was with the block design itself. It was wet deck and the free-standing, linerless bores would sink in the case, losing the head gasket seal. GM developed a really elaborate laminated head gasket but it was only a partial fix.

Also, the cast iron cylinder head casting was way complicated (maybe should have been two pieces) and extremely prone to cracking internally.

But both these failures allowed coolant into the crankcase, and permanent antifreeze is death on cylinder walls. But it was not the fault of the Reynolds 390 concept.

Did GM realy know what they were doing? , i do not belive they did...

[desmo]

Originally posted by McGuire
It is the future, though I think the Honda-Siffal method is the one. That is one solid deal, will go 250K miles with virtually no significant wear.

Siffal? Google's never heard of it!

[jpf]

Here's an interesting article I found a few months ago on cylinder bore treatments; I guess it's taken from Ward's Auto World several years ago. It sounds like it's pretty basic for the experts, but it was a good overview for me. It only covers aluminum blocks.

http://findarticles....ril/ai_54620821

The article is from 99, and references VAG considering laser etching bore treatments in their upcoming direct injection engines. Anyone know if they ever went this way?

[McGuire]

Originally posted by desmo


Siffal? Google's never heard of it!

Sorry, that was a typo. Should have been Saffil, not Siffal. I mashed out those letters on the keyboard of my Treo.

[McGuire]

Originally posted by cosworth bdg
Did GM realy know what they were doing? , i do not belive they did...

GM virtually invented modern automotive technology. In more ways than one, the Vega was one of the early signs of the machine starting to go off the tracks.

[Barbapapa]

As far as steel liners go, it's interesting that Nikasil is being used as the motorsport coating of choice with steel. Chrome has some great qualities, it's slippery, wear resistant and should form a very strong bond to the parent metal. Why isn't anyone using chrome when they use steel liners in motorsports? A hard chrome liner would have to be done in such a way as to have lubrication retention properties (porous?) and therefore would need to be done by someone familiar with the application. The final honing could be done by the same diamond hone used in Nikasil.

I'm about to send some 4140 liners for my Porsche 928 project to the heat treater and would love to hear more about this subject as it applies to steel liners. The coating choice is hard chrome or Nikasil and I'm leaning towards Nikasil. One of the reasons is actually because there are more sources that specialize in plating AND honing Nikasil whereas with chrome I would presumebly use a general purpose industrial plater and possible even send the coated liners to a Nikasil company for honing.
Is there anyone that does chrome motorsport liners?

[McGuire]

Originally posted by phantom II
Did cosworth fix the problems?

I never saw a cracked Cosworth-Vega head, so I guess Cosworth fixed that part. The aftermarket fixed the block problem by offering replacement cylinder cases with pressed-in iron liners on exchange. But even with the engine squared away it was still a crappy little car. Prone to rust, cheap trim and horrible ride and NVH even for its class.

The Cosworth-Vega was kind of interesting hardware but the performance was nothing to talk about. The car was heavy and by the time the engine got through emissions there was nothing left. 125 hp or something.

[phantom II]

Save you a lot of fuss by just dropping a LS2 in the hole. There is a company here in S Florida making a bunde with 998,944,924 and 928 conversions. I took delivery of a 928 in Germany in 87 and blasted around Europe in it. What a heavy piece if S.H.one T. True value is realized when you try to sell the damned thing. Good value now with a LS2 though.

Originally posted by Barbapapa
I'm about to send some 4140 liners for my Porsche 928 project to the heat treater and would love to hear more about this subject as it applies to steel liners.
Is there anyone that does chrome motorsport liners? [/B]

[McGuire]

Originally posted by Barbapapa
Is there anyone that does chrome motorsport liners?

Unless you are converting that 928 to diesel LOL I would go with the nikasil and stay away from chrome. It's just not worth sorting out for a one-off project.

Among other problems, attaining the precise degree of porosity is critical. There are two methods, reverse-chroming and mechanical abrasion, and neither is especially exacting. Good chance you end up with a deal like the proverbial chrome rings that never broke in.

[McGuire]

Originally posted by phantom II
Save you a lot of fuss by just dropping a LS2 in the hole.

That is your answer for everything. Spare tire flat? Ash trays full? Stick an LS2 in it.

[McGuire]

Originally posted by phantom II
I took delivery of a 928 in Germany in 87 and blasted around Europe in it. What a heavy piece if S.H.one T. True value is realized when you try to sell the damned thing. Good value now with a LS2 though.

I don't care what you do to a 928, the resale value will remain near zero.

[phantom II]

If your buddy has marriage problems. Suggest an LS2. LS2 cures everything. If the toilet is blocked, LS2 will fix it. If your dog barks...

Originally posted by McGuire


That is your answer for everything. Spare tire flat? Ash trays full? Stick an LS2 in it.

[Barbapapa]

Geez Phantom, you bring an interesting technical discussion down to blabbering idiocy, there are plenty of other places on the net with morons making childlike insults about each others cars and offering feeble, brainless solutions, drop a Chevy in it, how freakin original you are Bubba and on a F1 technical forum no less. And thanks McGuire for chiming in to insult my car too.

[phantom II]

He started it. Get yourself a LS2.

Originally posted by Barbapapa
Geez Phantom, you bring an interesting technical discussion down to blabbering idiocy, there are plenty of other places on the net with morons making childlike insults about each others cars and offering feeble, brainless solutions, drop a Chevy in it, how freakin original you are Bubba and on a F1 technical forum no less. And thanks McGuire for chiming in to insult my car too.

[McGuire]

I'm not insulting your car at all Ace. I am simply noting that the value of a 928 on the used car market is virtually nil. If a Porshe dealer was giving away door prizes off the back row of the lot, first prize would be one 928 and second prize would be two 928's.

[Powersteer]

I am pretty sure until recently as for V8 on V8, the 1987 928 could out handle anything from the USA into the year 2000.

[phantom II]

Compare the races a 928 won to that of 87 Corvettes, Camros and Mustangs. 87 was the year of the Challenge Corvette and are each worth 3 or 4 hundred thousand dollars. When I was at the factory in Stutgardt at that time, there where a bunch of 87 Corvettes there under going testing. No production Porsche could lap their test track faster than a 87 Z51 Vette. 96 was the GS Vette. 97 was the Z51 LS1 C5 Vette. In 2000 Chevy introduces the Z06. I went from a Vette to a 928 and directly back to a Vette, you lunatic. Mustang GTs and Cobras and Camaro Z28s and SSs made quick work of that boat anchor. All those American cars I mentioned are much more valuable than any 928 in the market place. Get real.

Originally posted by Powersteer
I am pretty sure until recently as for V8 on V8, the 1987 928 could out handle anything from the USA into the year 2000.

[phantom II]

Yes and you spoilt it. The first law of Engineering is efficiency. It is totally unproductive to mess with a 928. It will never have any value. That engine is heavier than any other V8 including modern cast iron Detroit engines. You ask for guidance from the honorable members with your project but is it fair? I can understand if it was a ZL1 Chevy, or a Chrysler Hemi, or even an Alpha Montreal V8, but a 928? Give us a break. So let me ask you, what is your definition of blabbering idiocy? Waisting energy seems to be idiocy, don't you think.
My suggestion is the height of engineering efficiency and I regret that you are not grateful for my help. I am deeply hurt.

Originally posted by Barbapapa
Geez Phantom, you bring an interesting technical discussion down to blabbering idiocy, there are plenty of other places on the net with morons making childlike insults about each others cars and offering feeble, brainless solutions, drop a Chevy in it, how freakin original you are Bubba and on a F1 technical forum no less. And thanks McGuire for chiming in to insult my car too.

[imaginesix]

Originally posted by phantom II

[Halfwitt]

Originally posted by Barbapapa
Is there anyone that does chrome motorsport liners?

Yes,

Cromoduro Camisas, SA (in Spain). Not generally small volume, but they have a specially-developed chrome bore process (not a simple hard-chrome).

http://www.cromoduro.com/eng.html

[Barbapapa]

Originally posted by Halfwitt

Yes,
Cromoduro Camisas, SA (in Spain). Not generally small volume, but they have a specially-developed chrome bore process (not a simple hard-chrome).
http://www.cromoduro.com/eng.html

Thanks Half'.
Hmm...They had this on their website:

"We are manufacturers of steel and aluminium engine cylinder liners for high performance vehicles (Renault F1 engine and other competitions).We also manufacture cylinder liners for industrial vehicles engines. "

I wonder what they do on the Renaults?

[imaginesix]

Originally posted by Barbapapa


Thanks Half'.
Hmm...They had this on their website:

"We are manufacturers of steel and aluminium engine cylinder liners for high performance vehicles (Renault F1 engine and other competitions).We also manufacture cylinder liners for industrial vehicles engines. "

I wonder what they do on the Renaults?

Since they don't do low-volume applications, they must be referring to the diesel engines on the team transport vehicles!

[Powersteer]

Originally posted by phantom II
Compare the races a 928 won to that of 87 Corvettes, Camros and Mustangs. 87 was the year of the Challenge Corvette and are each worth 3 or 4 hundred thousand dollars. When I was at the factory in Stutgardt at that time, there where a bunch of 87 Corvettes there under going testing. No production Porsche could lap their test track faster than a 87 Z51 Vette. 96 was the GS Vette. 97 was the Z51 LS1 C5 Vette. In 2000 Chevy introduces the Z06. I went from a Vette to a 928 and directly back to a Vette, you lunatic. Mustang GTs and Cobras and Camaro Z28s and SSs made quick work of that boat anchor. All those American cars I mentioned are much more valuable than any 928 in the market place. Get real.

Sad.

[phantom II]

Oh yes, I forgot to mention the ZR1 Vette in production from 90 to 94 of which I had a 405 hp 93. I took it to Germany into 928 territory and blasted along the Autobahns. Same price as a 928. which would you rather have? It lives in Munich now and is kept in mint condition and worth more than a 928 even in Germany.

Originally posted by Powersteer
Sad.

[McGuire]

Originally posted by imaginesix
Since they don't do low-volume applications, they must be referring to the diesel engines on the team transport vehicles!

At the risk of boring folks by repeating myself, I wouldn't mess with chrome for a project like this, especially a one-off. It's not worth it.

[McGuire]

Originally posted by Powersteer
I am pretty sure until recently as for V8 on V8, the 1987 928 could out handle anything from the USA into the year 2000.

What does that mean? "Handling" is a very broad and subjective criterion. Do you mean faster on a race track? LOL not hardly. Do you mean better driving qualities on the highway? There we are into personal preferences and matters of opinion, but I don't think so. To me the car drives very heavy, rather like an SL.

It was a very nice high speed gentleman's GT, but it was no sports car by any means. And it cost twice the money of a Corvette when new, and isn't worth as much today. Which was my point hmm. That doesn't make it a bad car -- if you have your heart set on one you can have it for a song, which is great. But just know there is a reason they sell so cheap. They are very expensive to maintain properly, even for a Porsche.

[hydra]

Can you say $1100 per timing belt tensioner (you need 2)??

[Halfwitt]

Originally posted by Barbapapa


I wonder what they do on the Renaults?

Cylinder liners one presumes, given that this is a site concerned with cylinder liners.

[J. Edlund]

Originally posted by dead_eye
I understand what you saying about not changing strngth propreties ie you can coat titanium and expect it to last forevre as a conrod but they are allowing magnesium piston crowns to be used with no abrasion/dust problems and no risk of ignition. Its also out on the grape vine that bmw and a few other companys have been testing the coatings on their all magnesium blocks to protect the water jackets form corrosion so they dont have to be made from aluminium.

To protect magnesium parts from corrosion with coatings isn't something new, but over the years better methords of applying such coatings have been developed. As for why a complete magnesium block aren't used; that is more related to strength of the material. What block material can be used is much related to what kind of combustion pressures you are going to use. If you want to use high combustion pressures a cast iron block is a much better choice than an aluminum block. That's why most of the F1 turbos used iron blocks when modern F1 engines use aluminum blocks, it's also why most diesel engines use cast iron in the block and why heavy duty diesels use cast iron both in block and head.

Titanium has really poor tribological properties, so if it's going to be used in a sliding contact it will require some sort of coating. The coating won't make the part last forever though.

Originally posted by dead_eye
As for hotter running cylinder and exhaust temperatures, hot exhaust temps (in a performance world at least) are ideal increasing exhaust pressure and speed and in turn increasing the scavenging effect and if fitted turbo spool up (in my experience at least). And although hotter cylinder temps can cause detonation problems you need to remember that the heat kept in will increase cylinder pressure and thus power availiable as mechanical force so lower compression ratios and fuelling levels can be used.

For example Cosworth has tested "insulated pistons" which decrease the heat treasfer from the combustion chamber. The papers on the subject that I have read have found that it causes the following:

- Detonation problems
- Decreased engine output
- Increased exhaust temperatures

Increased exhaust temperatures do not indicate better exhaust scavenging.

However, most car manufacturers are trying to insulate the the exhaust manifold pre-catalyst and reduce the thermal inertia of the system in order to get a faster light off. This is mainly done by replacing thick wall cast manifolds with thin wall castings or manifolds made out of hydroformed tubes. The manifold can be insulated using double wall piping.

Originally posted by dead_eye
In the case of the rotary engine theoretically its only 29% thermally efficient due to the massive surface areas of the rotors and the casing. if that can be increased by even 10% youd see a theortical power increase of 1/4 and possibly less fuel used to get it. Obviously real world figures will be a lot less startling as they always are but to me its got to be worth following up on- Il post once its being done and let you know the results.

Rotary engines are more efficient than that, or at least they can be. NASA ran a couple of direct injected rotary engines with very good results.

Heat losses through the combustion chamber isn't such a big issue some people makes it out to be. The main reason why engines aren't as efficient in reality as they would be in theory is related to that the combustion can't be done at constant volume. Given the long narrow combustion chamber shape of the rotary that's a big reason for its inefficiency.

If you want to decrase the heat losses from the combustion chamber the most simple solution is to increase the coolant temperature

Originally posted by dead_eye
I cant and wont claim to know a lot about these coatings and what they can and can't do but ive seen engines running some of the newer coatings and on the pistons and cylinders etc and seen one experimental head in which the cams, valves and followers all run on a self lubricating coating resulting in no oil supply to the head. I doubt it will be to long given the current oil situatuion before it starts appearing on top end cars.

In the early eighties it was though that it wouldn't take long until we had engines made out of engineering ceramics. Over twenty years later we still haven't any ceramic engines. It seems very common that people overestimate ceramics, both as bulk materials and as coatings.

Ceramics do suffer from wear and self lubricating coatings (solid lubricants) only have limited lifetime. I wouldn't expect and oil free engine or even an oil free cylinder head any time soon. Except lubricating the oil in an engine serves many important purposes such as cooling and cleaning the engine engine. One of the few things that possibly could be oil free in a near future is turbochargers running on foil bearings instead of oil lubricated bearings.

[footprints]

Originally posted by Barbapapa
As far as steel liners go, it's interesting that Nikasil is being used as the motorsport coating of choice with steel. Chrome has some great qualities, it's slippery, wear resistant and should form a very strong bond to the parent metal. Why isn't anyone using chrome when they use steel liners in motorsports? A hard chrome liner would have to be done in such a way as to have lubrication retention properties (porous?) and therefore would need to be done by someone familiar with the application. The final honing could be done by the same diamond hone used in Nikasil.

I'm about to send some 4140 liners for my Porsche 928 project to the heat treater and would love to hear more about this subject as it applies to steel liners. The coating choice is hard chrome or Nikasil and I'm leaning towards Nikasil. One of the reasons is actually because there are more sources that specialize in plating AND honing Nikasil whereas with chrome I would presumebly use a general purpose industrial plater and possible even send the coated liners to a Nikasil company for honing.
Is there anyone that does chrome motorsport liners?

try this site. They produce low volume chrome liners for most applications. Depending on availability of existing stock bores, a low volume production for your specified bore size will range from 110 to 160 pounds per liner.

www.laystall.co.uk

[cosworth bdg]

Originally posted by Barbapapa



"We are manufacturers of steel and aluminium engine cylinder liners for high performance vehicles (Renault F1 engine and other competitions).We also manufacture cylinder liners for industrial vehicles engines. "

I wonder what they do on the Renaults?

You would be very supprised at what they are doing and using. I have a video done by Renault Sport of the complete machining and testing of the RENAULT F1 GP engine........................

[Stian1979]

Chrome liners was the last update on the DVF engine if I remember corectly.

It was also hard crome in the high performance cylinders I used on my motorbike as a teenager.