Chuck Apperantely gone but not forgotten.

 

What would be the advantages, if any, in coating pistoms in a na engine?
If you do coat them what else do you have to take into acount, as in valves, heads, plugs,ect?

 

Same principals ( as previously noted apply, whether NA or FI. It is still and internal combustion engine with liquid cooling.

• Coating of combustion chamber just as critical, (maybe more seeing more exposure to coolant on other side of chamber roof) as piston dome. And why not, piston dome/crown is actually the floor of the combustion chamber.
  
• Valves, especially exhaust, though mainly for durability.
  
• Exhaust ports.....although from torque stand point, not worth the cost, in my opinion. More of a factor if turbocharged.
  
• With a coated spark plug, how would you expect to fire them?

 

No mystery there... a point that was clearly made in my initial response.

So, from your response I gather that it has everything to do with intake swirl, tumble and flame front speed right? Nothing to due with the temperature in the combustion chamber.
So if I change none of these variables I shouldn't get any detonation??? Hmm, try leaning your air/fuel ratio and that kinda doesn't hold true anymore does it?
Seems I've had some detonation problems with that exact same scenario before. Don't think it had anything to do with the flame front(s), which seemed to be in some sort of harmony just a day before either.

Sorry but I'm not convinced.



I don't know your age but you may know of Nick Arias either way. Been around quite a few years, builds blocks, heads and some really fast Bonneville lakester sleds. Anyhow, there was an article here some time back in one of the rags kinda detailing his engine. Of particular note, and to my point, Nick Jr. uses a Mickey Williams built tunnel ram intake which extends beyond the roofline in the nice clean air.... attached at the end is a 3-hole bugcatcher. A direct quote from that article states that the intake produces "1 psig of boost at 270 mph".
And yeah I understand that things vary with air temp, barometric pressure and a plethora of other variables but "2-5lbs" from 120 mph winds?? Ok, but you'll have to excuse me if I don't simply accept that because someone says it's so.

I understand what they are...... the product you're looking at adds weight to the rotating assembly. What I'm describing doesn't. Two different aproaches.

-Mindgame

 

So, from your response I gather that it has everything to do with intake swirl, tumble and flame front speed right? Nothing to due with the temperature in the combustion chamber.
So if I change none of these variables I shouldn't get any detonation??? Hmm, try leaning your air/fuel ratio and that kinda doesn't hold true anymore does it?
Seems I've had some detonation problems with that exact same scenario before. Don't think it had anything to do with the flame front(s), which seemed to be in some sort of harmony just a day before either.

Sorry but I'm not convinced.



well, the the temp gets high enough in the combustion chamber(IE, lean) you can get parts of the chamber hot enough that it will cause detonation. usually sharp edges first.


And yeah I understand that things vary with air temp, barometric pressure and a plethora of other variables but "2-5lbs" from 120 mph winds?? Ok, but you'll have to excuse me if I don't simply accept that because someone says it's so.

this I am not an expert on the actually air speed vs boost, but boost pressure has nothing really to do with anything. Sure, if the motor is a 6000hp motor, will 125mph air make any boost.. prolly not, but its a 100hp motor, it will have a much greater effect.. CFM, not boost pressure.. "boost presure" is what rice boys used to brag about at the local hang out.



I understand what they are...... the product you're looking at adds weight to the rotating assembly. What I'm describing doesn't. Two different aproaches.


uh.. no. its actually exactly what you are talking about, its a oil sprayer for the back of the piston.. not sure what you think it is.. go check out the link... there are pics of the jig.

 

Thanks arnie. On the plugs I was wondering if this would require a colder range because of the increased heat retained. Would there be any bad effects of just coating the pistons, like detonatio caused from increased heat on other parts ?

 

Could possibly require altering several tuning factors. Colder plugs, and ignition advance changes among them. It is what separates the few from the many. To 'wring' out the best, of any components that are changed or added. Much easier (with less time spent) to say than do.

From my POV, 'picking and choosing' which parts you coat, will be a benefical move, without negatives.

 

I'm following you on the tuning, but what in you opion would be the most benificial parts to start with? Kind of a greatest to least important list. thanks

 

just to throw in.. I am coating my piston tops and exhaust valves(turbo)

 

Hey guys, I've been reading this thread with some interest. Very good info! A few questions, though. Would you use these coatings in a street car? I'm building a really stout engine for my Lightning which is a weekend/sunny day driver. Thanks!

-Spencer

 

If you don't mind me asking how much did that run you?

 

Mindgame,

The added weight of a coating is minimal and it can be acurately accounted for, extra oil from a bug sprayer aimed at the bottom of the piston cannot.

On the extra PSI front, funny thing is with the right intake tuning you can get 5-6-7 extra PSI cramming air/fuel into the combustion chamber, it's not caused by outside "ram air" alot of wind tunnel time needs to go into that to get the added benefit, which can be there if done right. (think F1 intake systems)

JordanMusser is exacly right about the detonation issue. Being lean, or having oil in the chamber is going to cause the detonation on the "sharp" spots way faster than the added heat from the coatings. (lean causes things to get hot quick and oil lowes the octane rating in a hurry) In fact the funny thing is that the coatings will actually help the detonation issue since they keep the heat where it's needed and not in the rest of the engine. Coat the **** out of everything on an engine and then throw it on a dyno and check oil temp, coolant temp, it's really hard to get them to go up because the coating keeps it all the heat in.

Not picking on you, in fact there are alot of guys who understand engines alot better than most engineers do that are far removed from that profession as possible. I am one of them. Being a engineer is good in engines building because they can make parts strong enough to take the **** that engine designers make the engines do.


96ltz, As far as the parts to coat in what order...........

Piston tops & combustion chambers (equally important), valves, exhaust runners, intake runners, intake manifold, piston skirts, rotating assembly. That would be my most important to least important list. If you did all of them it would probably help the most.

Bret

 

Spencer,

Yes, it costs some. I would check out the Pop Hot Rodding Engine Masters results. It's a new kind of contest, basically dyno racing, but coatings are what will win it. (seriously!)

Figure for a full setup $2500, but you'll never have to worry about heat soak, in fact running a lighter weight oil will help since you can barely get any heat in the stuff.

Bret

 

As for my comment on lower the tension on the rings, I'm receding on that now, not actually sure why I put that in there--long letter, going off on a tangent. I definitely see that that was a wrong assesment, but you can still tighten the tolerances between the cylinder and piston.
To explain the fixture that DOES provide this positive displacement effect. It is an industrial sized/reinforced air conditionding duct going from the roof of the facility, where the is a very strong electric blower down to the motor, which is met w/ a rubber bellow that is SEALED to the carb/throttle body/airfilter, depending on what is being tested. This "blower" provides 125-150+mph winds (computer regulated) w/ more than enough volume to feed the motor as much as it can handle. Indeed this does not exactly simulate what the conditions are under the hood which is why it is only one of a barrage of items we use in testing.
Now, I NEVER said I was against coating, I love thermal coating, but it's only x% efficient. Using both in conjunction is what I was getting at. I'm also aware of the "keep the heat in" theory; but what is misunderstood is that you want to "keep the heat in" to push out the exhaust. If while the piston goes to TDC to exhaust the fumes the cylinder walls are cooled by oil, they don't transfer that heat to the incoming charge, therefore helping the charge density situation by a nominal amount unless you're going all out (read: racing) by keeping the air somewhat cooler until the intake valve closes and the piston heads north.
Ah, Mindgame, scrolled to see who I was partially responding to. Even in the Tuned Port Injection setups on the old L98s the engineers claimed up to a 1.2lb "supercharging" effect @ certain RPMs due to resonant properties. Now, if they can see that in mass production, tuning for a wide rpm range, don't you think the 6-figure per year Nascar engineers might think to tune for the effects and resonances of ~125mph winds and use them for an even higher supercharging effect. (EDIT) You can attribute appx 1-2lbs of my claimed 2-5 on the blown air and the rest probably on the intake design to respond to this air.

 

Ok, got me on that one..... I didn't look at the kit, just read through some of the responses and figured that this was something new..... a departure from the old oil-sprayer approach if you will. Guess it's not.

When I look at things like this I kinda use the grading system approach to make a final decision.

1) You spray the piston, increasing the windage (absolutely agree on that point). That's a minus.

2) Although "spraying" would lower the piston temp, I wouldn't think it could do it uniformly. So the question would be... where do you aim the sprayer? Which side of the piston needs the extra cooling? Lotsa variables, and while that's a good thing in complex object-oriented programming languages like C++, it's no good for the non-engineer looking for ways to make more power.

3) Guys like Mike Moran use coatings. Big plus. They also use gas ported pistons, no good on the street. So not all things 'race' are necessarily practical for stop and go driving.

4) You could probably get a set of eight done for less than $300. The fixture will cost you 4 bills and alot of extra time. Your time is worth something too is it not? The '+' again goes to the coatings.

That's how I'd come to a decision. In the back of my mind there are still lots of unanswered questions though (as there always are). Like.... since we're changing the expansion characteristics of the piston (cause they're designed to 'round out' at a given temperature which they may never reach now that they're coated) do we also need a special piston design for a coated application? Maybe something with less taper? What about ring end gaps?? Hmmm...

On to other matters......
Let's not get off on a tangent in my response to the 125 mph = 2-5lbs statement please. I'm just as aware of the theory behind inertial effects, ram-charging and all that jazz as any other Hot Rod magazine subscriber. I don't feel that Brutus' initial statement was about inertial tuning effects, just 125 mph "winds". I've been wrong before though.

And Brutus, I wasn't attacking you, just picking in my own little defunct way. Resumes aren't necessarily warranted here. It always becomes obvious who's in the know and who isn't on these message boards... time has a way of sorting that stuff out. Engineering student, practicing engineer, whatever... it's all good with me.
My thought on the matter has always been that yeah, an engine builder can bolt stuff onto an engine and make the most of it. I'd hardly compare that to someone who can bolt stuff on that he designed himself using his engineering skills. That to me is the difference in the builder and the engineer. So on that point, and sitting on the 'bolt-it-on-and-go" fence as I am in my limited capacity, I'd have to emphatically disagree with Stroker Ace. Take an excellent engine builder and program into him 5-6 years of mechanical engineering and he becomes an even better builder. The reasons are too obvious.

-Mindgame