Ceramic coating exhaust manifolds -- anyone done this? (500E) - PeachParts Mercedes-Benz Forum

seacoast_benz · #1 07-18-2002, 11:25 PM

Consider this in the long-term-planning area. Right now I'm still wincing from paying the taxes and fees on the 500E, and have to line up wheels and tires -- so the discretionary spending will have to wait for a year or so.

But I can at least do homework in advance. One of the obvious ideas on a 500E is to apply a sprayed ceramic coating like Jet-Hot or Cermachrome (see www.jet-hot.com and www.performancecoatings.com).

Given that the M119 engine is strongly sensitive to ambient temperature, it seems likely that there would be both a performance enhancement from a cooler intake charge, and improved life for heat-sensitive components in the engine compartment, such as motor mounts.

One thing that gives me pause is that I have heard a lot of anecdotal accounts of lower underhood temps from coating the exhaust system. But I'm enough of a scientist that I don't do anecdotes. Hard data! Clinical detachment!

OK, let's search the Web. Doing that produced a bunch of studies which show big drops in underhood temps, on the order of 100F or more. Very impressive! But I then noticed that the -same- study appears over and over again on various coaters' Web sites.

They must have been cribbing from one another, or from the original (described as having been done by Competition Cams in 1991, and shown here: http://www.ram-pro.com/PAGE5.HTM).

Drat! Back to anecdote. Has anyone done this on a hot high-performance mill? Were the results worth the price?

s/b

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Michael · #2 07-19-2002, 08:00 AM

One thing assuredly to consider here is the amount of labor getting those manifolds out of the car. I just replaced every single coolant hose in my entire 500E, so I've just recently spent the better part of 8-9 hours crawling all around that motor-in all that time I don't recall even SEEING the exhaust manifolds! (I hope you realize I'm kidding; the engine drains are tucked up under them, towards the rear of the engine)

I don't think coating the manifolds will cut intake temps much, IMHO. The ambient intake air is coming in thru the grille area, gets directed next through insulated runners then into the air filter housing-is the air in the filter housing long enough to be affected by the temp of that housing, which in turn has been impacted by underhood temp? I'm assuredly no scientist, but I simply don't think there's much to be gained here.

However, I'll be the first to admit that if I ever have the manifolds off my engine, I'll likely coat them but primarily for appearances

Good luck in getting together some hard data on this

Wolfton · #3 07-19-2002, 10:33 AM

I have a long pipe headder in my Jeep Cherokee that I Jet hot coated. I would recommend it without a doubt. The underhood temps are lower than they were with the stock manifold. Plus they keep their nice looks for a lot longer than without any coating. Having the Temps under the hood cooler also helped the Coolant temp stay down as well, and if you know of the Cooling problems of Jeeps, that was a big improvement. Its not a 500E but I'm sure the results would be the same for you. And one more thing the power difference in a well designed headder and exhaust are huge....

placo1 · #4 07-19-2002, 11:56 AM

I've been pondering this question in my mind since I originally saw someone talk about this topic months ago.

My question is this. By coating/insulating the headers on lets say the 500E your effectively reducing the heat in the engine bay by retaining it in your headers. From the headers it will pass into your catalytic converters. Well the question is are the catalytic converters designed to operated at these higher temperatures. Which also makes me wonder if the O2 Sensors can handle these temperatures. And what about downstream in the resonator and muffler. These items will surely operate at higher temperatures. Is the insulation around these items designed to handle the temperatures or will the heat seep into the passenger compartment.

I guess I wonder if taking the heat from point A and pushing into point B will cause more problems downstream.

Anyone have any thoughts on this? By the way I work with a catalytic converter manufacturer and I will ask them if this item is affected by high temperatures. I'll keep everyone posted.

royaiii · #5 07-19-2002, 12:50 PM

The problem of the heat is beacause of the small engine comparment. The 500E has an M119 that is tucked into a hole used to a inline 6. I think the exhaust manifold is sodium filled like my new S600 and that is their insulation. I wouldnt reccomend doing this because the O2 sensors will think the engine is causing too much fuel to burn thus overheating then the engine will start running lean. Also, the increased temps could cause the sodium to burn away. I think the best upgrade would be a custom radiator or a smaller pulley for the water pump. Underhood temps really dont matter, it is mostly your intake temperature and EGT that really count. Also the header is not a snakey m3 header, it bulbs out a little bit and then is sent to the Exhaust system. Thus most heat is not dissipated in the compartment.

seacoast_benz · #6 07-19-2002, 03:29 PM

Batching replies from multiple posters here, for brevity:

>I don't think coating the manifolds will cut intake temps much, IMHO. The ambient intake air is coming in thru the grille area, gets directed next through insulated runners then into the air filter housing-is the air in the filter housing long enough to be affected by the temp of that housing, which in turn has been impacted by underhood temp? I'm assuredly no scientist, but I simply don't think there's much to be gained here.

Yeah, it's tough to quantify how much heat gets recycled back into the intake charge from underhood temp, but I assume from the fact that the engineers took the time/cost to insulate the intake runners that cooling the underhood must be of some merit.

Another issue here is not heat-in-the-intake-charge, but heat-retained-in-the-engine-assembly-and-coolant. The M119 ECU reportedly is very heat-sensitive, and starts to pull back sharply on output once the coolant temp hits a critical level.

Most owners here of M119-engined vehicles report that their cars get doggy when the ambient air goes over about 90F, and sprint hard when ambient is down in the 60F range or lower. I think the restraint on output by the ECU correlates to coolant temp at or above 90C.

This particular vehicle is (I'm lucky) very well behaved temperaturewise, and less prone to overheat than others. I've had it in 108F ambient without any apparent distress from the cooling system, and only minimal performance reduction.

>Good luck in getting together some hard data on this.

Agreed. I really want to do detailed tests with thermometers and pyrometers and a dyno. Those old Competition Cams figures are enticingly good, but *one* study is a bit thin.

>Having the Temps under the hood cooler also helped the Coolant temp stay down as well, and if you know of the Cooling problems of Jeeps, that was a big improvement.

Yes! That is what I had been thinking about re the above.

>My question is this. By coating/insulating the headers on lets say the 500E your effectively reducing the heat in the engine bay by retaining it in your headers. From the headers it will pass into your catalytic converters. Well the question is are the catalytic converters designed to operated at these higher temperatures.

Excellent question! As far as I know, up to a point, catalysts like it hotter. Note that a big part of ULEV certification in new vehicles is managing to get the cats warmed up fast so that emissions don't spike on cold startup.

Whether there would be so much retained heat from manifold coating as to take the cats past this happy point and damage them or impair their conversion efficiency, I can't say.

>Which also makes me wonder if the O2 Sensors can handle these temperatures. And what about downstream in the resonator and muffler. These items will surely operate at higher temperatures. Is the insulation around these items designed to handle the temperatures or will the heat seep into the passenger compartment.

O2 sensors are an issue. But I assume that those are routine-wear items anyway. If they burn out in 30K instead of 50K, well, it's an easy part to get to and I'll just carry a spare on long road trips. Money saved on temp-sensitive underhood stuff might offset this outlay.

Resonator, I'd probably replace with a stainless Y-pipe anyway if I had the manifolds off. Muffler, well, it's usually pretty cheap to adapt a close dimensional match from the stock at a muffler shop.

Passenger compartment heat might be an issue in the back seat.

>By the way I work with a catalytic converter manufacturer and I will ask them if this item is affected by high temperatures. I'll keep everyone posted.

That would be amazingly valuable. Thanks!

>I think the exhaust manifold is sodium filled like my new S600 and that is their insulation.

Sodium filled manifold?!?!? My consternation is high. I had never heard of any manufacturer going to that length. If the new S600 has that, my hat is off to the Daimler engineers. I am reasonably sure that the M119 has sodium-filled exhaust valves, but that's all.

>I wouldnt reccomend doing this because the O2 sensors will think the engine is causing too much fuel to burn thus overheating then the engine will start running lean.

Do the sensors look at anything other than oxygen? I wasn't aware that they sensed temperature as well.

>Also the header is not a snakey m3 header, it bulbs out a little bit and then is sent to the Exhaust system. Thus most heat is not dissipated in the compartment.

Yeah, the win from coating will definitely not be as large as it is on other engines with more complex and serpentine header routing.

Thanks, guys, for your feedback! Very informative, and is helping to catalyze my own thoughts (as it were).

s/b

royaiii · #7 07-19-2002, 08:26 PM

"Combustion heat in each single exhaust valve is dissipated through a sodium-filled stem."
Sorry only the valve stems are sodium filled.

royaiii · #8 07-19-2002, 08:43 PM

I really am not 100% sure but the service advisor told me the engine computer monitors EGTs somehow. Perhaps one of the techs can confirm this. I dont think the rest of the exhaust will have any troubles because they are all tested to extreme conditions. Interior temp will increase but that is a problem of the W124 chasis heat insulation

ATATEXAN · #9 07-23-2002, 08:52 AM

Another thought on engine temperature. Has anyone else noted thought nice louvres on the back part of the SLK32 AMG's hood? A heat dissapation device, I am sure. I am going to measure surface as well as under hoo dtems on my E420+ and see where the hot spots are. I put an 85 degree C resistor in my car which really helps.

Subman · #10 07-23-2002, 03:25 PM

The manifolds on the m119 are a 3 piece configuration. This was done because it would be virtually impossible to remove a single piece manifold with the motor in the 124.
I have looked into getting a set of custom headers made for my car.
I emailed renntech and they told me 6 grand (WOW!!!!!) the reason the price was so high was because the motor had to be removed to install the headers.
I then went to a local shop that is know for there custom headers. I opened the hood and the workers had confused looks on there faces, thinking how hard it would be to do the job. After a long conversation with them we came to the conclusion that it would cost to much to do the job ($2500) and that the best solution would be to have the stock units "hone bored" (a process that basically sands down the inside of a cylinder to make for a bigger inside diameter). The shop could not do the job themselves but the pointed me in the correct direction to have it done. Since then I have looked at taking the headers off and I have come to the conclusion that I dont have the time (working and losing my car to have the headers sent away to be worked on) to do the job.
If I did have the work performed I would do all the labor myself, and then send the manifolds out to be worked on. If you look at the manifolds you will see that they are not the easiest to take off, I bet it would take 1+ to take one side off, and I dont know how you could fit a torque wrench in space to tighten the bolts for installation. If I chose to do this job in the future I will have them coated after they are hone bored.
I believe that if the exhaust system in the M119 was "opened up" a bit that a tremendous gain in power could be attained.
I believe this is an option to look at if one is trying to get more power out of there exhaust.
Subman

ATATEXAN · #11 07-23-2002, 04:22 PM

A Benz shop in Dallas told me that without a doubt the bigest power gains for the buck on an M119 lie in a new, larger diameter exhaust system. He claimed 100 more HP from an E420. He also stated that the biggest contributor to acceleraton gains of the 500 over the 420 lie not in 275 vs. 325 HP but in the higher gearing of the 500's. M-B rationalized the resultant fuel consumption hit by the limited sales of the 500. Not an overall big hit to their CAFE.

omegabenz · #12 07-23-2002, 06:00 PM

500E has a 2.82:1 differential, the 400E has 2.24:1 gear ratio.

I highly doubt that opening up a 400E will get 100 horsepower.

When you jet hot, keep in mind that it is the inside and the oustide making the inside surfaces smoother, so the heat doesnt heat up the exhaust manafold as much. Example: take a torch and hold it perpendicular to a peice of metal, it will heat up, but if you turn the torch so its smoother, going with the metal, it doesnt heat up the metal as much. Same thing goes for jet hotting.

I think headers would take a lot of money to make, if you are going through the trouble to make headers, I think you should make forward ones which would lead to biturbos. Yeah, thats what Id do.

The heat would go to the cat and the o2 sensor hotter than usual though, but it shoulnt affect it much because the heat is usually there, but its absorbed by the exhaust manafolds. o2 is o2 you know, temperature I wouldnt think would affect it. Any first hand thoughts?

Austin

#13 07-23-2002, 08:40 PM

Seacoast_Benz: I like your approach to :
: Hard Data, facts, proven results.
Too many people are too easily influenced by publicity, hear-say, promotions, looks good approach and spend considerable sums of hard earned cash on frizbees with no real value.
My opinion on ceramic coating: ceramic is a very good insulator (the shuttle is a good exemple). But, IMHO, the thickness of an exhaust coating is so thin that it would ahve a very limited insulating factor.
I wold think that in order to reduce the temperature under the hood, efforts (read: money) would be better spent at dissipating the heat, like adding loovers (see the front fenders of 300- diesels), remove/cutting the underbelly cover, or finding ways of increasing the air circulation under the hood.
JackD

Michael · #14 07-24-2002, 12:33 PM

Jack/all:

The slots on the front fender of a 300D are for cold air intake; feeds directly to the airbox.

I think electric fans could improve the volume of airflow-don't know about louvers, 'cuz when you start punching holes in panels you're disrupting the airflow as was designed by those pesky German MBZ engineers.

Y'know, I bet they gave all of this some thought, no?

seacoast_benz · #15 07-25-2002, 03:42 AM

Combining my replies again:

Charley said:

>I am going to measure surface as well as under hoo dtems on my E420+ and see where the hot spots are.

Yes! Measurement! Instrumentation! Data! This is the sort of thing I'd really like to do as a before-and-after test with ceramic coatings. Jeez, at this point I may just do it as a service to the community -- get a pyrometer and generate some new data other than this overused 1991 study that's everywhere.

subman said:

>the best solution would be to have the stock units "hone bored"

That sounds familiar. Extrude hone? Where they force polymer clay with an abrasive in it under super pressure through the passages? Elegant technical approach. Costs something like $500 to do an exhaust manifold, unless my memory is blown.

>If you look at the manifolds you will see that they are not the easiest to take off, I bet it would take 1+ to take one side off, and I dont know how you could fit a torque wrench in space to tighten the bolts for installation.

Hmmmmm, that's a really good point. Has anyone actually pulled an exhaust manifold off of one of these and lived to tell about it?

Charley said again:

>A Benz shop in Dallas told me that without a doubt the bigest power gains for the buck on an M119 lie in a new, larger diameter exhaust system.

Most likely. (But that's the $6K to RENNtech option. Ugh.)

JackD said:

>Seacoast_Benz: I like your approach to :
>: Hard Data, facts, proven results.
>Too many people are too easily influenced by publicity, hear-say, promotions, looks good approach and spend considerable sums of hard earned cash on frizbees with no real value.

Roger wilco, Jack.

That's why I felt sketchy after seeing the *identical* magic study on half a dozen ceramic coating shops' Web pages.

>My opinion on ceramic coating: ceramic is a very good insulator (the shuttle is a good exemple). But, IMHO, the thickness of an exhaust coating is so thin that it would ahve a very limited insulating factor.

We should dig up a specialist in ceramics and ask.

>I wold think that in order to reduce the temperature under the hood, efforts (read: money) would be better spent at dissipating the heat, like adding loovers (see the front fenders of 300- diesels), remove/cutting the underbelly cover, or finding ways of increasing the air circulation under the hood.

Nervous about tinkering with the belly pan. I understand that interrupting the airflow from the NACA ducts on the underside can lead to rapidly overheated engine mounts, with the subsequent hassle and cost of changing those out.

Louvers could be a good thing. Some downside in terms of cost and of making the car less obviously close to factory new.

Apropos of louvers, there are some odd flexible flaps on the back of the radiator housing on this car that I can't figure out the function of. (But I'm not about to touch them until I know what and how!)

And as far as augmenting circulation under the hood, hey, we're on the same page -- see the thread I just began, about using
axial flow fans in the intake path...

s/b