Ignition timing and piston ring seal - The Technical Forum Archive (2024)

ScottNC

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Two totally different topics but at the same time sharing a common concern? At the engine speed F1 engines see now, and with the anticipation of them going even higher with the V8's. The time window would seem quite small to effect complete combustion and have an active and timely top ring seal. What amount of ignition lead is required? What method of triggering? How many compression rings are used and of what type and composition? Are "gas ports" or some other means used to energize the top ring?

desmo

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I was told a few years back that F1 engines typically run 50-55 degrees ignition advance, and that while combustion time is always a concern, it wasn't the limiting factor in increasing rpm. Chamber geometry is a bigger concern than available time, though the two are of course interrelated. Valve reliefs in the piston head define the functional chamber shapes and each cylinder has essentially two seperate combustion chambers, one for each intake/exhaust valve pair with a distinct squish area between the intake reliefs.

Here's a piston from the Ferrari 049 engine. I can't see any gas ports. There are only one compression and one oil control ring.

shaun979

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Hi Desmo, saw those pics of the 049 piston and rod you posted quite a while back. Later on in the Peter Wright Tipo 049 book, I noticed that the rod cap looked slightly different from your pics. Do you know possible reasons for the difference? Different stage of evolution of the component? Thank you

ScottNC

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Desmo, I did a search and found your other 049 pictures. As best as I could tell from looking for visable wear, might I conclude that the connecting rod is piston guided? Also, an interesting feature of the oil ring was visable; the lower rail was slotted. Are there more oil return holes in the oil ring groove as well as the ones you can see intersecting the bottom of the groove? It is suprising to me that concidering the extreme RPM the engines are operated at, that some form of gas ports are not used so as to allow for tighter vertical clearances on the top ring?

ScottNC

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Another thought. Is it possible that the second land or a portion of it (below the accumlulator groove?) is large enough in diameter to be used as a pseudo second ring?

desmo

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Does that look piston-guided? I had assumed we were looking at the wrist/gudgeon pin between the rod and the piston here, but perhaps not. A piston-guided design at first blush would seem ideally suited for an F1 engine with its emphasis in reducing rod weights and fMEPs.

Who came up with the idea, Carillo?

ScottNC

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Nope. It doesn't appear to be piston guided. I would expect something in the order of .005 inch or so rod pin end to piston boss clearance, this obviously has more than that. I had been looking for but not seeing wear indicators on the side of the big end. Sorry.

No less than the drag racer Bill Jenkins told me about piston guided rods around 1996 while attending the P.R.I. show, he was half in the bag in the hotel bar at the time. I called Jack Sparks at Carrillo who as it turned out was already quite aware of it and made two sets of rods for me to give it a try. I have talked to people who swear there is something there (ie; power) but for the life of me, I've not been able to find anything to it. Looking back, at that time I was not very concious of keeping the rod beam and rod bearing well centered in the bore....

J. Edlund

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In a SAE paper by Lamborghini it's mentioned that piston guided con rods reduce friction because of the smaller diameter which gives a lower axial bearing velocity. This was the early nineties and I assume that it wasn't new even then.

As for the gas pressure it doesn't need any gas ports to work on the rings. Different types of rings have been tested and they seem to get thinner and thinner.

ScottNC

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[As for the gas pressure it doesn't need any gas ports to work on the rings. Different types of rings have been tested and they seem to get thinner and thinner. [/B][/QUOTE]

Something has to activate the rings. When concidering the engine speed F1 is seeing and indeed the the speed the V8's will see, it would seem the vertical clearance necessary in lue of a gas-port equiped piston would in itself be a problem. Prehaps ring control at high speed is less of a problem in the bore sizes used in F1 compared to the bore sizes I'm accustomed to (4 to 4.700 inches)?

Stefan_VTi

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My guess is just that they they found that the increased friction due to the extra ring pressure at high rpm was larger than the power increase from the increased compression. Nothing special, high speed 2-strokes have been fooling with different ring (L-style, keystone, flat, gas ported, etc..) setups for years...

zac510

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desmo, after reading your post yesterday I checked the 2003 season Piola technical review because I remembered reading about gas sealing of rings.

Do you think that the teams (or maybe just Ferrari) introduced the gas ring sealing sometime after the 049 engine, or do you consider the story (not written by Piola) in Piola's book to be outdated and incorrect?

J. Edlund

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[QUOTE]Originally posted by ScottNC
[As for the gas pressure it doesn't need any gas ports to work on the rings. Different types of rings have been tested and they seem to get thinner and thinner. [/QUOTE]

Something has to activate the rings. When concidering the engine speed F1 is seeing and indeed the the speed the V8's will see, it would seem the vertical clearance necessary in lue of a gas-port equiped piston would in itself be a problem. Prehaps ring control at high speed is less of a problem in the bore sizes used in F1 compared to the bore sizes I'm accustomed to (4 to 4.700 inches)? [/B][/QUOTE]

The rings are "activated" by the side clearence. The clearence should be enough to allow the gas to pass by but not so large that the ring will "hammer" which can destroy at least aluminum pistons.

On the compression stroke the ring is initially pressed down by the interia of the ring making it seal against the lower surface of the ring grove. The friction also holds the ring down. As pressure build up it will press the piston down and outwards. This pressure must be high enough so that the ring doesn't move upwards when the piston deaccelerates. Problem will rise when the ring due to inertia will close the side clearence. But a F1 piston ring is quite thin which means a very low inertia and a high critical speed, while the coatings most likely solve any wear issues. Since a thin ring also decrease the volume behind it, pressure will also build up faster.

rgsuspsa

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Originally posted by J. Edlund
In a SAE paper by Lamborghini it's mentioned that piston guided con rods reduce friction because of the smaller diameter which gives a lower axial bearing velocity. This was the early nineties and I assume that it wasn't new even then.

As for the gas pressure it doesn't need any gas ports to work on the rings. Different types of rings have been tested and they seem to get thinner and thinner.

Piston guided connecting rods have been in use since the mid 1960's, if not before.
My first encounter with piston guided rods was in 1966 when I began racing two-stroke Kart engines.

rgsuspsa.

desmo

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I'm curious if that was original spec or aftermarket, and whether it was an Italian or American kart engine.

rgsuspsa

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Desmo: McCulloch Kart engine, MC-9 & later, were American. Original piston & aftermarket used piston guided rod.

Ron Sparks

McGuire

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Don't know much about kart engines, but in the big two-stroke outboards the piston-guided rod has been around for awhile. These engines were also among the first to employ "cracked" rods. For four-strokes, I am not a fan of the piston-guided rod... as I see it the piston has enough on its plate.

desmo

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I'm curious why you specify four strokes there. They at least have a bore to help locate things that isn't swiss cheesed with ports.

ScottNC

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What was the rational for it (piston guided rod) way back when it was first tried?

McGuire

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Originally posted by desmo
I'm curious why you specify four strokes there. They at least have a bore to help locate things that isn't swiss cheesed with ports.

A two-stroke is a windbag anyway.

McGuire

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Originally posted by ScottNC
What was the rational for it (piston guided rod) way back when it was first tried?

The idea is a thinner (across the rod bearing) and lighter rod and reduced friction (at the expense of greater specific loadings). It has been used in NASCAR (when they still ran qualifying engines) and in claimer-type engines on the short tracks. It has also been used on some Volvo and (I think) Nissan production engines.

McGuire

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I would expect that with the current engine life regs, we would find fewer two-ring setups and more of the conventional three ring packs.

Halfwitt

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Originally posted by McGuire
I would expect that with the current engine life regs, we would find fewer two-ring setups and more of the conventional three ring packs.

I wouldn't think 1200 - 1500km would present much problem for a two-ring piston. I know a lot of Le Mans engines use three-rings, but I don't know if it is the case for all of them.

ScottNC

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Originally posted by McGuire

The idea is a thinner (across the rod bearing) and lighter rod and reduced friction (at the expense of greater specific loadings). It has been used in NASCAR (when they still ran qualifying engines) and in claimer-type engines on the short tracks. It has also been used on some Volvo and (I think) Nissan production engines.

It's still being used as are narrowed rod bearings. I know of .650" wide bearings on a 1.880" rod pins working well at Michigan. But...not piston guided.

It still seems it would be an uphill battle to run the engine speeds used in F1 with that ity-bity stroke and no gas ports and get the top ring to work effectively. Are current F1 engines cylinders still dry sleeved and coated with nikasil? What kind of piston to wall clearance do they use?

rocketdoc7

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"No less than the drag racer Bill Jenkins told me about piston guided rods around 1996 while attending the P.R.I. show, he was half in the bag in the hotel bar at the time. I called Jack Sparks at Carrillo who as it turned out was already quite aware of it and made two sets of rods for me to give it a try. I have talked to people who swear there is something there (ie; power) but for the life of me, I've not been able to find anything to it. Looking back, at that time I was not very concious of keeping the rod beam and rod bearing well centered in the bore...."

I'm new to this forum, and if you could, please explain what you mean by "piston guided".

I think that what you're referring to is that the rod is constrained by the piston boss side clearance rather than the gaps between rods and the crank's bearing "cheeks".

BTW, I almost used Bill Jenkins to supply engines for my Trans Am effort in the late eighties (I ended up using Fisher Chevrolet V6's), but the owner/driver never heard of him. Tough to belive that anyone in Motorsports didn't know of "Grumpy Jenkins".

soubriquet

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Why not discard the little end entirely, and run the rod directly in a socket in the base of the piston crown?

Engineguy

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Originally posted by soubriquet
Why not discard the little end entirely, and run the rod directly in a socket in the base of the piston crown?

Back in the mid-1960s I had a red 1963 Corvette split-window coupe that had a socket (in the piston) and ball (on the rod small end) arrangement. The piston was a ringless deep-drawn thin steel shell... I don't recall how the socket was formed/fastened into the piston shell. It ran like a scalded dog at about 20,000 RPM on a methanol/nitromethane mix. I don't think the emissions were very good though as it only burnt about half the fuel and left the chassis bathed in the rest, which it spewed from its single unpiped open exhaust port. After a crash busted up the body I shortened the wheelbase and put a scaled-down short-bed Chevy pickup truck body on it... looked real badass with the massive rear slicks. Probably still have it somewhere in my parents garage, if it didn't parish in the great fire of 1984.

So it can be done... but socket joints are weak in tension, especially with the socket being formed in aluminum, ignoring for a moment the question of how you would manufacture it. To make the socket's tension-side lip stronger, the ratio of ball size to rod beam cross-section must be increased greatly... and a giant steel ball form is not something we want at the top of the rod.

soubriquet

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Originally posted by Engineguy
..d a giant steel ball form is not something we want at the top of the rod.

I'm not describing a giant steel ball. Rather a knukle to deal with the forces which apply, and not to waste mass.

rgsuspsa

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Originally posted by soubriquet
Why not discard the little end entirely, and run the rod directly in a socket in the base of the piston crown?

This approach will not prevent the piston from rotating in the bore, unless otherwise restrained.
A piston which has a non spherical dome, and/or valve relief cuts requires orientation
within the bore.

Alluded to in a previous post is the effect of centering the rod in the engine's fore-aft direction within the cylinder bore when a piston guided rod is used. Manufacturing tolerances due to relative alignment between crankshaft rod journals and cylinder bores becomes less critical, as the crankshaft is not required to center the rod in the cylinder bore. Also, crankshaft end play/clearances are not important to rod location. Conceptual benefits achieved by centering the rod in the bore are:

1) Avoids/minimizes lateral bending moments & consequential bending stresses imposed
on the rod due to being offset from the center of gas pressure on the piston during the
expansion stroke.

2) A rod which is offset from the cylinder bore center will cause the piston to co*ck(lean)
in the engine's fore-aft direction during every stroke of the engine's cycle.
This will be most pronounced during the expansion stroke due to gas pressure
loading of the rod via the piston pin.

What the magnitudes of benefits 1 & 2 are in a given engine is open to discussion, and they
may, or may not be significant, depending upon the engine's intended usage.

Ron Sparks

rgsuspsa

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Originally posted by Engineguy
Back in the mid-1960s I had a red 1963 Corvette split-window coupe that had a socket (in the piston) and ball (on the rod small end) arrangement. The piston was a ringless deep-drawn thin steel shell... I don't recall how the socket was formed/fastened into the piston shell. It ran like a scalded dog at about 20,000 RPM on a methanol/nitromethane mix. I don't think the emissions were very good though as it only burnt about half the fuel and left the chassis bathed in the rest, which it spewed from its single unpiped open exhaust port. After a crash busted up the body I shortened the wheelbase and put a scaled-down short-bed Chevy pickup truck body on it... looked real badass with the massive rear slicks. Probably still have it somewhere in my parents garage, if it didn't parish in the great fire of 1984.

So it can be done... but socket joints are weak in tension, especially with the socket being formed in aluminum, ignoring for a moment the question of how you would manufacture it. To make the socket's tension-side lip stronger, the ratio of ball size to rod beam cross-section must be increased greatly... and a giant steel ball form is not something we want at the top of the rod.

A Chevrolet, pushrod V-8 running at about 20,000 RPM? Is this a typo, or are you serious?

Ron Sparks

Canuck

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it spewed from its single unpiped open exhaust port.

A single port - meaning a single cylinder engine or a manifold with no exhaust system? Or?

NTSOS

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Just curious.....if the piston guided rod typically uses .005 clearance on the small end, are not the big end rod side clearances increased?

And if so, what does that do to oil control?

.....or maybe they are not increased!

John

Engineguy

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Originally posted by rgsuspsa A Chevrolet, pushrod V-8 running at about 20,000 RPM? Is this a typo, or are you serious?

Originally posted by Canuck A single port - meaning a single cylinder engine or a manifold with no exhaust system? Or?

Mine was red.

soubriquet

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Thanks engineguy. I appreciate the technical problems, but I was intrigued by the thought of being able to reduce the little end mass.

ScottNC

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Originally posted by NTSOS
Just curious.....if the piston guided rod typically uses .005 clearance on the small end, are not the big end rod side clearances increased?

And if so, what does that do to oil control?

.....or maybe they are not increased!

John

The following pertains to NASCAR type engines as well as some drag race stuff.

I've seen big-end side clearance done one of two ways: Open it WAY up to about .100" or run about .015" per side, that is .015" between the crank cheek and rod side as well as between the two rods themselves (assuming a two rod oer pin arrangement). Kind of a pseudo piston guided arrangement.

Currently because of increased oil flow due to valve spring and piston cooling squirters it has been desirable to cut vertical bearing clearances to about .001"/inch of journal diameter. Nothing earth shaking there but it is tighter than in the past. Also the delta in the bearing wall has been reduced conciderably to reduce cavitation problems with the bearings.

NTSOS

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Open it WAY up to about .100" or run about .015" per side, that is .015" between the crank cheek and rod side as well as between the two rods themselves

Hi Scott,

Thanks for the response. Jeeze, either config above seems to be excessive as it relates to possible oil control problems and the vertical clearance that was mentioned does not seem to be much of a reduction. I guess I'm still confused........what exactly prevents oil from pouring out of the rod side clearances?

John

Engineguy

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Originally posted by NTSOS
Thanks for the response. Jeeze, either config above seems to be excessive as it relates to possible oil control problems and the vertical clearance that was mentioned does not seem to be much of a reduction. I guess I'm still confused........what exactly prevents oil from pouring out of the rod side clearances? John

Side clearances are traditionally many times (i.e. 5x to 20x) the vertical clearance... so I'd think oil flow quantity is metered by, and solely a function of, the cross sectional area created by the difference between the journal OD and the bearing ID.

NTSOS

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so I'd think oil flow quantity is metered by, and solely a function of, the cross sectional area created by the difference between the journal OD and the bearing ID.

Hi Engineguy,

Well....that's interesting. Most every book I've read on building a SBC, warns against excessive total rod side clearances that allow oil ring control and windage containment problems.

Generally speaking with STEEL rods, the recommendations are .002 - .0025 vertical and a minumum of .010 - .012 total rod side clearance. I would think that Smokey U. would consider .030 in the relm of excessive clearance as it relates to oil control.

OTOH.....maybe time has passed ole Smokey and me by.

OTOH2....I bought a recent book on how to build a big inch SBC and the total rod side clearance recommendations were pretty much the same.

John

Engineguy

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John,

I have paid close attention to every word uttered by people like Smokey and Grumpy for the last 40 years and have great respect, but I don't let that stop me from thinking things through for myself and questioning the "common wisdom." We tend to think that everything guys like that say is gospel backed up by endless subject-specific testing... but it may just as likely be an assumption they've lived with since they built their first engine and looked up the spec in a GM service manual.

My thinking is that at some point you're flowing as much oil from the small vertical clearance opening as possible and increasing the side clearance won't increase the oil flow, because it's already a few multiples of the vertical clearance cross sectional area. Obviously 10" of side clearance wouldn't flow any more oil than 5" of side clearance. Just as obvious, I assume, 0.020" of side clearance will flow more than 0.010"... but will 0.030" flow more than 0.020" or has the side clearance ceased to be a restriction? I don't know.

Interestingly, Bill Jenkins suggests, in his book, "We also check side clearance in the normal manner... For drag or circle racing we use 0.015" to 0.020" (actually says 0.015" to 0.20" but let's assume that's a typo). The latter figure is preferred to prevent oil trapping."

By the way, on the same page that Smokey suggests in his Power Secrets book that more than 0.015" side clearance will give you an excess oil problem, he says he would cross-drill the main bearing journals for better high-RPM oil supply. So he wasn't always right PCT.

McGuire

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Originally posted by soubriquet
Why not discard the little end entirely, and run the rod directly in a socket in the base of the piston crown?

An entirely reasonable idea for some applications, employed not only on very tiny engines as shown here but on the very largest ones as well. Giant marine and stationary engines like the Sulzer use a "trunk piston." The trunk piston conists of two components, the piston and a trunk rod, which are combined via a spherical joint. This trunk rod then communicates with a conventional connecting rod on the other end.

Of course the purpose of the trunk piston is to reduce geometric side loading and stablilize the piston vertically for less cylinder wear. Sometimes the trunk rod join contains a pawl and ratchet mechanism, which rotates the piston in the bore for more uniform wear. And often the trunk rod is a bundle of smaller rods to dampen the pressure loadings and vibration. These engines are designed to operate for years on end without stopping.

McGuire

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Maintaining a side clearance on the connecting rod pair can only help control windage. To whatever extent the big ends are free to move from side to side on their pin, they will push the oil around with them. Or at least try as they attempt to maintain a hydrodynamic pressure structure between the bearing and the journal.

Frictional losses are arguably slightly lower with the piston-guided rod. However, the wear patterns on the rod bearing inserts scare me to death.

NTSOS

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Maintaining a side clearance on the connecting rod pair can only help control windage.

Mac,

This all may have been a dream....but I seem to recall reading consistently over the years that it also cuts down on the amount of oil that is slung onto the cylinder walls therefore a lower tension oil ring may be implemented.

Also, controlling leakage, thus windage as you indicated, obviously requires less supply and scavenge pump action combined with the lower drag oil ring to reduce overall parasitic loses. No es verdad?

However, the wear patterns on the rod bearing inserts scare me to death.

In that case, I think I'll pass on this whole piston guided deal.

Thanks.

John

NTSOS

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Just as obvious, I assume, 0.020" of side clearance will flow more than 0.010"... but will 0.030" flow more than 0.020" or has the side clearance ceased to be a restriction? I don't know.

EG,

I don't know either......I just assumed these guys tried it at least once over the years and ran into problems. They do seem to be somewhat consistent, but your thinking also makes sense.

he says he would cross-drill the main bearing journals for better high-RPM oil supply. So he wasn't always right PCT.

Ah hah....so he did say it! I think it was McGuire that mentioned the problems associated with cross-drilling the mains and I scrambled to find my Smokey book to get the exact quote....only problem, I can't find my Smokey or my Bill books anymore. :

Jeeze, Smokey, how embarrassing!

For drag or circle racing we use 0.015" to 0.020" (actually says 0.015" to 0.20" but let's assume that's a typo). The latter figure is preferred to prevent oil trapping."

So much for being consistent!

Thanks!

John

NTSOS

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Which reminds me.....about 40 years ago I read a magazine article (maybe Car Craft) about a guy who was having rod bearing problems with his racing SBC and decided to fix it.

His approach was to remove the soft bearing material from the bottom steel bearing shell but only from the 8 and 4 clock positions up to the cap parting line. He did the same for the top bearing shell.....the 10 and 2 position down to the rod parting line. This left a top and bottom bearing pad and then amazingly reduced the vertical bearing clearances to .0005.

He claimed it solved his rod bearing problems forever and the bearing surfaces always looked brand new when he tore down his racing engines for inspection. I do not remember how he addressed his rod side clearances and I think he called his mod "precision bearings" because of the small clearances. He was going into production and that was the last I ever heard about it.

Anyone remember it or possibly the bearing mod?

John

Engineguy

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Originally posted by NTSOS
Which reminds me.....about 40 years ago...Anyone remember it or possibly the bearing mod?

Just another way of pre-compensating for the big end bore distortion that occurred at high RPM with the rods of that time (much less so today). At high RPM his rod bore elongated vertically, pinched in across the parting line, and voila! he's back to a "normal" bearing situation of a somewhat average gap all the way around, give or take a few slight stairsteps.

The other way to do this is to shim the parting line a couple thou' while you finish the big end bore to make it intentionally out of round after the shims are removed. You then have .001 to .002 vertcal clearance and .003 to .004 clearance across the parting line static, but .002 to .003 all the way around at high RPM.

This was what prompted the Big Foot parting line touted by Crower when they started making rods... a bigger contact area at the parting line kept the sides of the bore from pinching in, keeping the bore round. Round is good.

Fortunately good custom aftermarket rods are available today (and some pretty good OEM rods too) so you don't have to play bearing games.

Engineguy

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A timely post from another forum (speedtalk.com >engines) :

k-star wrote:
I know this has been discussed before. But not in this exact application..

I am building a 427 sbc. The oil clearance on the rods are all .002 the main oil clearance is .0025 to .0027 The rod side clearance is .022 to .025. it is a hyd roller engine. motown block..

Is there any reason i would need a high volume pump on this engine??? I ask because i have been using standard oil pumps in the last 20 small blocks i built with zero issues. I had a oil pan made just for this application and the manufacturer sent a hv pump along with the pan....

I am thinking about using a standard pump... Any reasons not to??? Keith

REPLY:

We have always used the standard volume pump with high pressue spring with no issues for years and plenty of oil pressure.

Side clearance does not really factor into the equation as the the bearing clearances dictate oil flow or resistance. If this was true the piston guided rod engines we have worked on with over .090 side clearance would be running zero pressure.
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NTSOS

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Side clearance does not really factor into the equation as the the bearing clearances dictate oil flow or resistance. If this was true the piston guided rod engines we have worked on with over .090 side clearance would be running zero pressure.

Engineguy, I like this......maybe the old boys got locked into using relatively small rod side clearances in an attempt to control oil leakage because of the "racing clearances" they used..... .003 - .004. When better rod/bearing design allowed much closer tolerances, the need for tight rod side clearances diminished, but the practice continued and it was simply perpetuated throughout the years.

Kind of like what I've been doing..........it's OK, I can update my old magazines!

Thanks!

John

ScottNC

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Regarding side clearance, vertical clearance and oil throw-off: I can only speak from my own obsevations and experiences. The last five years or so there has been a trend towards higher crankcase vacuum (depressions), smaller diameter drillings in the crankshaft, reduced delta, that is taper in the bearing inserts, smaller journal sizes and less vertical bearing clearance. Also compartmentalized, very shallow, intricate oil pans that hug the rotating assembly and dedicated piston cooling oil jets. Currently NASCAR engines are seeing two to three times as much oil flow as they used to in the mid '90's. Like most things in life, it's done as part of a balancing act; increasing the rod side clearance as done with a piston guided rod set-up is done as one of a plethera of changes the net result of which we hope ends up as an improvement. I might note too, that bearing wear from loading hasn't shown to be an issue IF the rod and bearing are well centered with the bore. You would be suprised at how narrow rod bearing have become. As power output per unit of displacement goes up, centering the load becomes even more important, both for reliability AND ring seal (believe it or not). What a NASCAR engine might get by just fine with an NHRA pro stocker wouldn't get off the dyno with.

NTSOS

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ScottNC,

Yes, I sincerely appreciate the patience and the concepts that you all are presenting here and apparently my knowledge base is in serious need of an update.....and this is all good!

I know NASCAR is fairly secretive about the current hot setup....would you all care to recommend good recent reading material that would help me get up to speed? I'm especially interested in oil jet piston cooling and the rotating assembly.

I guess it's a safe bet that it's time to toss my old reference library!

Actually this is really good timing as I am preparing to research pieces and parts/technology for the motor that I will build for my '56 Post......the last motor, an FI twin turbo!

Thanks!

John

http://home.pacbell....lair/index.html

ScottNC

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NTSOS,

I know of no definative reading source. Sorry. Most teams have arrived at the hardware they are using as a result of finding out the hard way what didn't work. Hence, team "A's" oil pan and squirter size and location may not work for team "B". It might be worth noting that piston squirters and the like weren't really necessary until the trend toward lighter and lighter pistons. Time was that a heavy piston with a full skirt acted like a heat sink, giving a larger time window before heat had a detrimental effect. It's larger contact patch allowed greater opportunity for heat to transfer out of it through physical contact with the wall. The current strutted "X" style pistons will not live without supplemental cooling at present power levels (NASCAR). Most post race inspections reveal an annealed part.

NTSOS

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• 692 posts
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I know of no definative reading source. Sorry.

Scott,

Yes, I suspected as much. Car magazines usually dribble out good information over a prolonged period, although it's usually not the latest and greatest stuff. :

The reason I am interesting in piston cooling is to help with detonation control with the turbo motor, especially with pump gas. I have noticed several OEM's use oil piston cooling from the factory with their stock turbo motors. Do not the oil jets contribute to a large percentage of the increased NASCAR motor oil flow requirement?

John