Exhaust manifold wraps

[oil pan 4]

If you want to just paint them even then it seems difficult to get paint to stick to new headers.
Once the headers have been installed and gotten some oil and rust on them you can forget about repainting them and getting the paint to stick around for a long time, unless you sand blast them. If you do sand blast the paint will stick to them and stay there like chewing gum on a cat.

For my diesel I am going to sand blast my turbo manifolds and ceramic coat them inside and out, I dont think the manifolds will be wraped.
The cross over pipe will be wraped with header wrap and covered with my salvaged "silicone sock".

[kah]

I've done some digging around for more info on manifold and exhaust wrap. It seems very popular with performance modders, and should be very beneficial on turbo engines, adding low rpm torque, while not doing very much for high rpm horsepower.

What is generally advised is to use e special silicone sealant, on the manifold before you apply the wrap, and on the wrap once fitted. This should greatly reduce wear on the manifold.

Other than reducing the temperature under the bonnet, the extra low rev torque would likely increase FE. I might check it out in a couple of months, but it seems like quite a comprehensive mod if you have to take out the manifold to fit the wrap.

[Ladogaboy]

kah, a lot of that is anecdotal. I've heard just as many tuners recommend against heat wrap/coatings because it can increase the likelihood of exhaust manifold failure. The primary (really, the only proven) reason to use heat coating is to reduce engine bay temperatures. Doing so prevents the turbo from heating up and passing that extra heat on to the intake air. If anything, according to a lot of people who have been trying to heat their intake air (WAI) for fuel economy, heat wraps might actually HURT fuel economy.

[kah]

Yes, and no. Reducing engine bay temperatures was a side effect to what powertuners wanted to achieve in the first place, the primary reason for heat wrapping manifolds and exhaust, was to reduce back pressure from the exhaust system for increase in power.
I'm not an expert on motor engineering, but from what I know of warm air intake, the purpose is to decrease the resistance of air when flowing through the throttle, only making it suitable for (non-turbo?) petrol engines.
For turbo diesels, a manifold and exhaust wrap would (theoretically) increase the energy transferred to the turbo, increase scavenging, lead to higher torque figures and improve fuel economy, however i have not been able to find any dyno test that confirm (nor any that refute) this claim, apart from one done by a manufacturer (of wrap)..
As for fatigue and wear on the wrapped parts, I'm pretty convinced that it's true, but a thing to consider is that most people who wrap their manifolds do it for power increase and drive their cars hard, and usually drive petrol engines, and the temperature of exhaust gas of diesel engines is lower than the exhaust gas of petrol engines. How big a difference that makes is impossible to know, but manifold fatigue is definitely a risk to consider.

[skyking]

I'm looking into it for my diesel truck, because anything I can do to lower underhood temps will also reduce the need for cooling air. The factory put so much excess air through there. They designed for a worst-case scenario. When I calibrate the grill louver system, one of the temps I will watch is the area right over the manifold and turbo. A blanket should help greatly.

[Ladogaboy]

Yes, I've heard of all of those purposes, but what I was saying is that the only thing that I've seen proven is the decrease in engine bay temperatures. Everything else, including increased exhaust velocity, increased turbo efficiency, etc. is, as you said, unproven. I'm just not sure if it would affect mileage in any way.

[skyking]

Originally Posted by kah

Yes, and no. Reducing engine bay temperatures was a side effect to what powertuners wanted to achieve in the first place, the primary reason for heat wrapping manifolds and exhaust, was to reduce back pressure from the exhaust system for increase in power.
I'm not an expert on motor engineering, but from what I know of warm air intake, the purpose is to decrease the resistance of air when flowing through the throttle, only making it suitable for (non-turbo?) petrol engines.
For turbo diesels, a manifold and exhaust wrap would (theoretically) increase the energy transferred to the turbo, increase scavenging, lead to higher torque figures and improve fuel economy, however i have not been able to find any dyno test that confirm (nor any that refute) this claim, apart from one done by a manufacturer (of wrap)..
As for fatigue and wear on the wrapped parts, I'm pretty convinced that it's true, but a thing to consider is that most people who wrap their manifolds do it for power increase and drive their cars hard, and usually drive petrol engines, and the temperature of exhaust gas of diesel engines is lower than the exhaust gas of petrol engines. How big a difference that makes is impossible to know, but manifold fatigue is definitely a risk to consider.

The cast iron manifold on my truck has 240,000 miles on it and has grown and warped over the years. I think a blanket my help that problem, since it will normalize the inside and outside temperatures quite a bit.
I do give the engine cool down time before shutdown, if I have been making significant power.
I have a fresh manifold that we are going to port and polish and install soon.
One of the things I have planned is to add pre- and post-aftercooler temperature gauges, and a drive pressure gauge. This will give me information on how tightly I can close down my cooling before it starts affecting inlet temps.

[TOOSTUBBORN2FAIL]

My engine will need a rebuild at some point in the coming years. When I do that, I plan on doing several things.

Friction reducing coatings from Swain tech to reduce frictional losses.

Oil shedding coatings on things like the rods and rockers.

Real 3mil thick ceramic coatings on the piston tops, combustion chambers, valve faces, and exhaust ports. Real 15mil thick ceramic coatings on the header, pipes leading up to the cat, and the entire rest of the exhaust. All from swain tech. They will probably then get wrapped in header wrap, and sealed completely.

Whether or not the increased flow thing makes a difference, i'll be giving it the best chance to work. On top of that, the coolant temp reductions and engine compartment temp reductions are proven, which will allow a smaller radiator and less grill area. Plus, header wrap will also slightly quiet the exhaust note even further.

[some_other_dave]

I have heard from some old-school racers that all of those coatings do help to make power in full-tilt-boogie race motors. Oil shed on the inside of the block (gets oil back to the pan faster), knife-edged crank throws, boat-tailed mains (help with air flow management inside the engine), teflon wrist pin buttons, and so on.

Many of them are only intended to work at high RPMs, which is not where fuel economy is found. It would be interesting to see what good any of them would do for MPGs.

-soD

[TOOSTUBBORN2FAIL]

Yep^, I figure they are in the realm of diminishing returns, but my goal isnt savings, so I figured I would try it.