How do I make my engine Better? Racing Engines 101 . . . . .

[Interested Observer]

One has to weigh the supposed heat transfer benefits versus the cost and worry of possible ceramic chips flying around in the engine.   While the notion of ceramic coating to resist heat transfer is attractive intuitively, when one does a heat transfer calculation with and without a necessarily very thin ceramic coating, it turns out that the transfer rate is only minimally affected. 

Has anyone ever seen documented test results that show the heat transfer rates are, in fact, significantly reduced?

[RichFox]

In the late 70s I was running a twin turbo 270 GMC in my '32. I had Jahans cast pistons and a poorly designed intake. Which was tough on pistons. I was also working in the tool room in the plasma spray Dept. of a large airline overhaul facility. I sprayed my piston tops with the same ceramic as they were using on the burner cans. Worked well for me. Good forged pistons worked better. But as observed, the ceramic worked well in that circumstance.

[manta22]

IntObs;

I was under the impression that a significant portion of the ceramic coating advantage was its reflecting of the radiant heat of combustion.

Regards, Neil  Tucson, AZ

[wobblywalrus]

What Neil says may have some implications.  Will  the ceramic coating raise the combustion temps enough to require adjustments to the tune, like higher octane fuel or a couple of degrees of retard on the timing?.

[Milwaukee Midget]

Hey, Wobbly -

Part of the last iteration of the Grenade included coating the pistons. 

Because we notched the piston to accept an exhaust valve that extended deeper into the combustion chamber, and the original piston head thickness was getting a tad thin in that area, my chief concern was to protect the piston from additional heat build up.  There were enough other changes made that I can't reasonably say that the piston coating was a contributing factor toward power production, but it did provide some additional peace of mind for me.

In addition to an ever-so-slight increase in CR, and the same fuel for the dyno work in both sets of tests, the total advance timing remained the same, although as I recall, I was able to kick in an additional bit of advance in the midrange.

Granted, we were using 118 octane, and we were not running any boost.

Total timing was 36 degrees advance.

Your mileage may vary, but I'm one of those heretics who believe that durability is a performance factor. 

[tauruck]

Well it is Christmas time again.   Time to share some development information as my Christmas gift to everyone.

WARNING:   You supply your own brain cooling . . . . . .             I recommend a chilled and fermented beverage . . . . . . .

This is a real world example/sample of why:   "It's Complicated"     AND, why:    You need to Test, Test, Test.

This is some development data collected from some sample Subaru EJ25, DOHC, 4 valve per cylinder heads.    Some of the data was collected from differing samples, some data was collected from samples modified as described below.   I'm going to post the data, graphs and comments, in order sequentially, so you can use the screen zoom feature to examine the data more closely.     Try using a zoom % of 200/250% to be able to clearly read the data on the individual pages.    I might have to add a second posting to complete all the pages and data, but here goes.

The premise was to document the data, starting with the baseline of a stock cylinder head with stock valves, so that differing performance modifications could be evaluated.   Some data sets have varying numbers of samples, as shown below.    My own opinion is that more data samples equates to better data averaging, but I ended up using what the client was able to provide.    Some data is withheld.    Valves were tested to .55" lift to determine the "port limit".    The cams used have only .46"/.48" gross lift.


Test 101: Stock head with stock valves.  Notice the flow difference on exhaust between the 2 cylinders.   On Subarus, one exhaust port is centered between the valves of the cylinder, one is offset, inline with one valve and the other valve's port has a "dogleg".



Test 102: Different Stock head with 1mm oversize valves, both intake and exhaust.   Re-worked valve seat angles.   Note the pronounced difference in flow for the "dogleg" port.



Comparison data for Test 101 Vs Test 102 with flow differences in cfm and %.  The client was disappointed with the results, but it was pretty much what I expected.    Some decent gains @ low/mid lifts, peak flow unchanged.    Well, the ports were not enlarged, so no improvement in peak flow.



Test 103:  CNC ported head with stock valves.   This combination was tested because the client thought that CNC porting would improve the flow without the valve size change.



The flow data for Test 103.



Comparison data for Test 101 Vs Test 103 with flow differences in cfm and %.  The client was disappointed with the results again, because the flow gains were only small/modest through most of the lift curve.   My conclusion was that the stock valves are too small to be effective in the CNC ported head.



Test 104:  CNC ported heads with 1mm oversize aftermarket valves.   Re-worked valve seat angles.   Note that there are still differences in exhaust flow in the "dogleg" exhaust ports.



The flow data for Test 104.



Comparison data for Test 101 Vs Test 104 with flow differences in cfm and %.  The client was now happy with the results, because the flow gains were substantial pretty much throughout the lift curve.   My conclusion was that this combination had further potential, particularly on the exhaust side of the CNC ported head.



Test 105:  As for Test 104, BUT, minimum throat diameter increased .014" on intakes, .015" on exhausts.   No other changes to CNC ported heads with 1mm oversize aftermarket valves.   Note that there are still differences in exhaust flow in the "dogleg" exhaust ports.



The flow data for Test 105.



Comparison data for Test 101 Vs Test 105 with flow differences in cfm and %.  The client was now very happy with the results, because the flow gains were substantial throughout the lift curve.   At this point I was pretty satisfied as well, although I still think that the intake might be "slightly" too large on throat diameter.   Significant double digit gains on exhaust, throughout the lift curve.



Averaged flow comparison graph between Test 104 and Test 105.



The averaged flow data for the comparison between Test 104 and Test 105.



Averaged flow comparison graph between Tests 101, 104 and 105.   So from start to finish.



Balance of the averaged flow data for the comparison between Tests 101, 104 and 105.

Conclusions:
A)  4 valve cylinder heads flow pretty well at low lifts, but there are some modest increases that can be gained with careful work.
2)  "Dogleg" ports are not the ideal.   But you probably don't get to fix that.
d)  Small increases of size and % of valve throat diameter can dramatically alter the flow.
z)  Concentrate your efforts on the lift range that gives the best gains.

So, once again, work carefully, thoroughly AND, Test, Test, Test.

Chris and Bo, once I get some more time, I will modify this post and add some numbers and %'s for valve throat diameters for the various tests.   These numbers might be of interest to others as well.

 
Fordboy

While we hang onto every word, Chilled and fermented ain't a world wide phenomena. Some LSR wannabeees like the Scotch, Mexican and other concoctions. Forgive me for being "partly' raised by Canadians who termed beer "Beaver Piss". I swear the Hard Tack runs better that the 4.3% fermented stuff. Whoever won a race on Miller Lite. Alky, that's the stuff.

[Milwaukee Midget]

While we hang onto every word, Chilled and fermented ain't a world wide phenomena. Some LSR wannabeees like the Scotch, Mexican and other concoctions. Forgive me for being "partly' raised by Canadians who termed beer "Beaver Plymouth". I swear the Hard Tack runs better that the 4.3% fermented stuff. Whoever won a race on Miller Lite. Alky, that's the stuff.

There is a universal sentiment which I embrace -

Stay hydrated. 
 

[wobblywalrus]

Oh, a basic question.  Was the engine named "Grenade" after it was run with the ceramic coatings?

[Milwaukee Midget]

Oh, a basic question.  Was the engine named "Grenade" after it was run with the ceramic coatings?

I named it that long before the first bolt was turned.  Gratefully, it never lived up to its namesake! 

[jimmy six]

My thoughts were build what ever it was to go just a little bit farther than a 1/4 mile  . So I looked to what was needed to be competitive in off shore boat racing and used those parts... Worked pretty good so far.

[manta22]

Oh, a basic question.  Was the engine named "Grenade" after it was run with the ceramic coatings?

I named it that long before the first bolt was turned.  Gratefully, it never lived up to its namesake! 

Wasn't there an old drag racing car called  "The Jade Grenade"?

Regards, Neil  Tucson, AZ

[wobblywalrus]

That name "Calico Coatings"has been mentioned several times when discussing coatings.  I will get their advice and send the parts there.

[Buickguy3]

     Neil,  It still shows up at the "Cackle Fest" at the California Hot Rod Reunion. They fired it up under the check in area at one of the big motels as a promotion one evening on 100% Nitro. A few of the un-initiated were standing, albeit momentarily, over the headers. You've never seen so many people scatter so fast. Beautiful car and worth seeing.
     Doug   

[manta22]

Thanks, Doug. I had not heard of it in years.

Regards, Neil  Tucson, AZ

[Interested Observer]

Wobbly,
I think you would be well served to do a bit more research and fact-finding before just hauling off and sending your parts for coating.  In perusing the Calico web site, it appears they only have one application suitable for the combustion chamber, and it is a “metal-ceramic” material.  That is, it is aluminum with some ceramic mixed in.  Not a whole lot different than your existing aluminum parts and it is dubious that it would restrict heat transfer to any extent. 

They show no physical properties for the material nor heat transfer performance.  They seem to be a coating shop that deals mostly with anti-friction and anti-corrosion coatings which probably do about what they claim, but insulating coatings don’t seem to be in their repertoire.