Exhaust & Catalytic Converter Temps

[Shipkiller]

This is a speculative question.

Many race teams and weekend racers have some of their engine/exhaust components coated with the Swain Ceramic Coating. They (Swain) claim that up to a 400' temperature drop can be seen on just the headers. I have seen some tests that after an exhaust header was coated, it did flow better (scavenging effects).

Because some of us drivers do track our cars and occasionally the engine oil temps start to get up relatively high, I was wondering if this was a viable option to reduce under-hood temperatures and maybe pull a little more power out of the engine?

I also wonder if keeping more heat internal to the catalytic converter if the cat will be damaged by this extra heat?

Thought???
Comments???

Edit: One other thought: Maybe a thermal rap..............

[3002 tii]

+1

curious as well

[mfanatic325]

I ceramic-coated my JVT headers with VHT header ceramic paint (spray can) prior to header swap. I'm sure there was a dramatic decrease in temperature due to the lack of catalytic converters, but overall, I really don't think coatings matter in terms of underhood temps since--and correct me if I'm wrong--the cooling system is programmed to really do its work once a specific temp is reached. Therefore, it doesn't matter if there was a decrease in temps from lack of cats, because the cooling system will just wait it out until the overall temp hits the programmed marker before it really starts kicking in.

I'm using my MR2 as a comparison. It's the only benchmark I have in terms of personal related experience. I had "upgraded" that car's stock radiator for supposed increased flow and cooling. Only to find out that it really was just a waste of money. Efficiency might've been improved, but that really doesn't matter considering the old unit was still functioning perfectly well, and it was still programmed to keep the car at a certain temp anyhow. End result: I wasn't really running any cooler, just supposedly more efficient.

On that note, ceramic coatings for headers and such do have better benefits than say, a more efficient radiator since they'll provide better flow characteristics; which mean potentially more power. So it's safe to say that coatings are really only for improving flow/power? And not really for overall cooling

[Shipkiller]

Doing some more research, I have read some really amazing stories on just how good the Swain Coating works. Some of the tests indicate that on average the underhood temps are reduced by approx. 50' or more.

I would not even think that it would correlate to a 50' oil temp drop on the engine but it should allow the cooling system to work more efficiently and you might see (my estimation) a 10' to 20' drop, but that is a guess.

I even saw some threads that after getting the headers up to temps and heat soaked it only took 10min before you could touch the header without burning your fingers after turning the engine off...

I was also looking for info on potential cracking. Info off of the web site and reading forum threads indicate that it (Swain) is a three layer coating. It seems that the only time the coating might crack if the area is continuously subjected to wild temperature swings and the cracking only happens on the outer coating.

I also read some threads that there are approx. three major players in this area and the other two players (not Swain) are more for looks than temperature control.

More research is required....

I also wonder if rapping the headers would help also....

[O-cha]

Yes the coating makes a huge difference. I've never heard of swain, but any ceramic coating will have the same effect. They are usually rated in 1600 and 2k degrees.

You can run the car shut it off and by the time you can touch the coated part, if you touch just after it where it's not coated your finger will burn instantly. It also really does reduce the amount of heat radiated from the headers.

A lot of the more wild claims of drops in under hood temps or oil temps are likely attributed to the removal of the cats, not the coating. Removing the cats hugely decreases engine heat and under hood temps.

[Shipkiller]

Swain is supposedly the oldest of all the manufactures. Don't know though.

The real thing is, I am wondering if keeping the heat internal to the header, will overheat the cat and cause damage. That would be a COSTLY issue.

I am not an expert in this area so I have to ask questions and do research.

[O-cha]

Originally Posted by Shipkiller

Swain is supposedly the oldest of all the manufactures. Don't know though.

The real thing is, I am wondering if keeping the heat internal to the header, will overheat the cat and cause damage. That would be a COSTLY issue.

I am not an expert in this area so I have to ask questions and do research.

Do not coat a catted header.

[Diokaef]

Originally Posted by O-cha

Yes the coating makes a huge difference. I've never heard of swain, but any ceramic coating will have the same effect. They are usually rated in 1600 and 2k degrees.

You can run the car shut it off and by the time you can touch the coated part, if you touch just after it where it's not coated your finger will burn instantly. It also really does reduce the amount of heat radiated from the headers.

A lot of the more wild claims of drops in under hood temps or oil temps are likely attributed to the removal of the cats, not the coating. Removing the cats hugely decreases engine heat and under hood temps.

WHS^^^

[Diokaef]

Originally Posted by O-cha

Do not coat a catted header.

+1

[mfanatic325]

Doesn't the ECU control the temps via cooling system anyway though?
Like...it doesn't matter if you're somehow able to drop 500 degrees from one component in the engine bay, cause the cooling system won't start working 100% anyway until a certain overall temp?
But I don't disagree that the coatings work. Just trying to get some final closure in the temperature category =P

[O-cha]

Originally Posted by mfanatic325

Doesn't the ECU control the temps via cooling system anyway though?
Like...it doesn't matter if you're somehow able to drop 500 degrees from one component in the engine bay, cause the cooling system won't start working 100% anyway until a certain overall temp?
But I don't disagree that the coatings work. Just trying to get some final closure in the temperature category =P

The coolant its controlled by a mechanical thermostat. But dropping underhood temps can indirectly lower coolant and oil temps.

The cats are prevented from overheating by the ECU monitoring EGTs.

[Shipkiller]

As far as I know, the ECU does not control the thermostat or waterpump. The ECU uses coolant temperature and radiator outlet temperature to increase the engine RPM slightly for faster warmup and to monitor total system temperature for fuel mixture control (supposition on my part) and for overtemp limp mode.

From what I know, the cooling system (radiator/oil cooler) works at 100% (max delta T) at max airflow. The thermostat will start to open up at 180' (I think) so when the thermostat is fully open and with max air flow (based on air temp) you have a finite amount of heat removal that the system is capable providing, also depending on air temperature.

The engine also produces a maximum amount of heat and I assume that the cooling system has been designed to be a balanced system, eg. removing as much heat as is generated with some overhead, up to a point for MOST circumstances. The exhaust system also removes heat from the engine and as stated above, this has been factored in by BMW engineers.

Once the engine and associated local components have reach a temperature equilibrium (heat soak) there probably has been engineered into the cooling system some extra headroom, again for MOST circumstances.

The reason I say MOST circumstances is the design engineers, builders (construction designers), marketing and bean counters must reach a consensus on just what operating environments the car will most likely be driven in. I bet that the cooling system is not a good as it could be. This could be a cost function or a construction limitation or both.

Since there is limited cold air flow through the engine compartment, removing more of the heat that is attempting to leave through the exhaust can only lower the engine temperature equilibrium point. It may be only 10 degrees but that helps. Remember, there is a lot of hot air from the radiator/oil coolers attempting to escape from the compartment also. This will also bring some of the latent heat from the block but the delta T' is not great.

Some of us track people who drive there cars in very hot weather, are probably at the upper end of the MOST circumstances. If you F/I your car, then that just adds more heat that must be removed.


Now with all that gobble gook said that is my reasoning.

edit: I forgot about the EGT's. Thank O-Cha.

[mfanatic325]

Originally Posted by O-cha

The coolant its controlled by a mechanical thermostat. But dropping underhood temps can indirectly lower coolant and oil temps.

The cats are prevented from overheating by the ECU monitoring EGTs.

Yeah, so all in all, the decrease in header temps really doesn't make a difference overall unless you get a different thermostat and tune the ECU so that it keeps the car's overall running temps lower. Right?

So pretty much the coating is for improving flow


I retract my statement after the previous ^ loll

[Shipkiller]

I don't think a lower temp thermostat will reduce engine temps. It will just open up earlier delaying the point at which the engine get to heat soak. The cooling system can only remove a finite amount of heat, no matter what temperature thermostat you use.

I may be wrong.

[O-cha]

Originally Posted by mfanatic325

Yeah, so all in all, the decrease in header temps really doesn't make a difference overall unless you get a different thermostat and tune the ECU so that it keeps the car's overall running temps lower. Right?

So pretty much the coating is for improving flow


I retract my statement after the previous ^ loll

No, re read what I said since I would just type it again.

[mfanatic325]

Wouldn't lowering the set temp in which the cooling system starts working 100% lower the overall running temp though?

[Shipkiller]

I do agree that coating will improve flow but if you reprogram the ECU for reduced temps, then I would think you would loose performance.

With your JVT headers, I would think a coating would improve performance without the drawbacks of trying this on OEM headers, with an added benefit of slightly reduced temps.

This is a good discussion.

Got to go to bed. Driving to CT tomorrow for work...

[O-cha]

Originally Posted by mfanatic325

Wouldn't lowering the set temp in which the cooling system starts working 100% lower the overall running temp though?

That depends on if the system is running at a temperature higher then the thermostat when operating where you're looking to lower temps or not.

Most cars run at higher temperatures when you are pushing it and the thermostat is actually the cooling system capacity itself.

You shouldn't care about the temperature while cruising around town or in a blizzard.

[Diokaef]

People O-cha is being right all along, just listen what he said, nothing else can really be added to his comments.

[mfanatic325]

Originally Posted by Diokaef

People O-cha is being right all along, just listen what he said, nothing else can really be added to his comments.

Wasn't doubting, just trying to find closure and learn more at the same time

[O-cha]

Originally Posted by mfanatic325

Wasn't doubting, just trying to find closure and learn more at the same time

Originally Posted by mfanatic325

Yeah, so all in all, the decrease in header temps really doesn't make a difference overall unless you get a different thermostat and tune the ECU so that it keeps the car's overall running temps lower. Right?

So pretty much the coating is for improving flow


I retract my statement after the previous ^ loll

But you came to the opposite from accurate conclusion to what I said.



Let me restate I guess.

The biggest benefit of coating headers is to prevent radiant heat from leaving the headers and heating up parts and air next to it. It results in a reduction of under hood temps. Don't forget one of the closest and biggest parts to the headers is the block. There is considerable amount of heat uptake here and the result of coating can lower oil and coolant temps some.

Now that I've restated that though I have to restate that while there is an indirect lowering of temps, most of the wild claims are more to do with removing the cats themselves then actually coating the headers, since most people remove the cats and add coated headers at the same time rather then move from a header to coated header of the same design. The increase in efficiency by itself creates a reduction in temps.

The "better scavenging" argument by keeping "exhaust velocity up" is a weak one IMO and increases of horsepower are more likely to come from the above. Though in theory keeping EGTs higher through the header will cause a change.


So no, no tunes or thermostat changes are needed for the coating to help keep thing cooler, although from the efficiency standpoint it could.