Starting a new thread related to sizing of a turbo blanket earlier. It lead me to ask "the Google" some questions but I had trouble finding much scientific data on the matter, mostly anecdotal experiences from truckers.
Edit: Found the paper referenced in the video, it's from a 6.5L cummins Diesel.
https://repositories.lib.utexas.edu/handle/2152/43718
Direct Link https://repositories.lib.utexas.edu/bitstream/handle/2152/43718/BICKLE-MASTERSREPORT-2016.pdf?sequence=1&isAllowed=y
I did find this video on the topic using a smaller engine as the test bed. https://www.youtube.com/watch?v=FrFeaNGDnOk I'm wondering if the findings would hold true on larger engine.
In short, they found heat stayed where it should be, that seems intuitive, but they also found 2-3 more PSI at most RPM ranges which lead to more torque sooner, something I think we all care about very much. Now it appears it does not increase overall numbers, it just shifts where the torque bands starts.
Edit: I listened closer and from the paper i says during spool up it has the affect of an additional liter of displacement!.. wow. Look around page 21 for the nice charts and graphs.
I had not even considered a blanket, but now I'm thinking a few C Notes is cheap insurance on this.
Last Edit: Adding some graphs from the paper
Most interesting article. Thanks for posting it. Jack
If I was considering wrapping the exhaust on my big turbo charged engine...
Fire suppression would be my motivator, any performance improvements would be a bonus.
They burn down when some line bursts, and sprays an oil or fuel around, and it gets onto the hot exhaust, directly or by the fan blowing it there.
Burning Buses became far more common, with the arrival of turbos and their heat...
Either motivation, it is good to wrap your exhaust if there's a turbo in there.
Happy coaching!
Buswarrior
I did not know that, but it makes sense. Fire has been a concern of mine, I love this board, the more ya know.
I can't rest asking. Why, physically speaking, does increasing the interior temp of the blanketed turbo make it spin faster? Could it have something to do with the fluidity of hot air??? Any physicists out there? Jack
@oltrunt In the study and in the video they mentioned it being about keeping heat in the hot side of the exhaust system, heat increases pressure, more pressure spins the turbo faster. I think it's that simple. If I'm honest, intuitively this don't seem like it would be as evident as they show it, but you can't argue with the data.
Found this little calculator from deflate-gate http://physics.bu.edu/~schmaltz/deflate.html The principal is the same.
The temp numbers I'm using are just even round numbers to show an example.
I put in 400F as an initial temperature, then a final temperature of 450 (simulating adding a Turbo Blanket and wrapping headers). Initial pressure I set to 14.5 (1 bar) , the final pressure was 16.20 . Seems the math checks out, that's an extra 2 PSI spinning the turbo, to suck in just a little more air.
Just covering the hot housing with the cover dosen't make any difference on the 2 stroke you need the complete that covers the manifolds,pipes and the housing and they are pricey I paid 2000 bucks for my set on 8v92 in 2000 lol I don't think I gained much for the bucks spent in the way of performance,but they did keep the bed room floor cooler
Wrapping the exhaust increases the draft like an overheated chimney. I did this a few years back on a 6.2 diesel that I installed a Banks turbo kit on it. It was designed to max boost between 9 and 11 psi. I match ported and polished the heads, did same to turbo. Wrapped exhaust with that woven fiberglass wrap from turbo to muffler using 3 1/2 inch pipe. Used Flowmastermuffler with 4 inch outlet. It then started producing 18 pounds boost when wound up. Called Banks and explained all I did. He said no wonder boost went so high. He said I would need to install a wastegate. I did and set it to 13lbs max. Btw, the truck was pretty powerful for what it was.
Even wrapping the exhaust on a non turbo engine will result in some power boost. Two things to keep in mind. One is the wrapping can retain road salt in winter and hasten pipe rust through. Second is the wrapping can absorb dripping oil and fuel and keep a potential fire going if it gets hot enough to ignite.
2 strokes don't generate the EGT that a 4 stroke will blankets are more for safety on a 2 stroke,my 6.5 turbo the brother to a 6.2 will get up to a 1000F under a load
You would get more benefit from reduced heat in the engine compartment and the bedroom above than an increase in power. 1 or 2 psi of additional boost will not make a noticeable difference with a big old 2 stroke.
JC
My recent investigation into military 8V-71T's found a version that was 440 hp, with completely insulated manifolds, turbo and exhaust ports (inside the head). Point was to maximize heat at the turbo for more power, it also had a bypassed blower with a big bypass. What really works well is to take a brand new manifold and piping (you can blast a cast iron manifold) and ceramic coat it inside and out. We did this on race engines where we didn't want to wrap, and it did a significant job of keeping the heat in. So did stainless steel headers.
Somebody explain to me how you can get so much HP from a marine 8v71T with water cooled manifolds to take the heat out instead of keeping it in ?
Can't help with that but I do know the Ideal gas law shows that volume, temperature and pressure are direct multipliers of each other. Meaning, double the temperature and you double the volume or else you double the pressure. Meaning with the blanket you get more gas blowing through at higher pressure. How much depends on how much heat you keep in there.
Jim
The marine versions can afford to have bigger injectors and more boost because they have greater cooling capacity. The same level of power in a bus would require multiple large radiators to prevent overheating. Wrapping the exhaust retains the heat to increase the gas flow efficiency to spin the turbo a little faster. The ultimate engine would be a military/marine engine setup with multiple turbos. Brian had dug into military specs to help me out when I was considering a military 8V71T. One of the sources indicated that one of the reasons they wrapped everything when the engines were installed in Howitzer Carriers, was to increase the exhaust flow to the outside air to reduce the cooling requirements (a little). That may have been an experiment to be able to boost the power of the engine in a confined space. It probably helped a little, just like the flow of fuel through the injectors to the tank, but then, the military has the big bucks to do things like that. ::)
Quote from: DoubleEagle on September 25, 2018, 02:03:19 PM
The marine versions can afford to have bigger injectors and more boost because they have greater cooling capacity. The same level of power in a bus would require multiple large radiators to prevent overheating. Wrapping the exhaust retains the heat to increase the gas flow efficiency to spin the turbo a little faster. The ultimate engine would be a military/marine engine setup with multiple turbos. Brian had dug into military specs to help me out when I was considering a military 8V71T. One of the sources indicated that one of the reasons they wrapped everything when the engines were installed in Howitzer Carriers, was to increase the exhaust flow to the outside air to reduce the cooling requirements (a little). That may have been an experiment to be able to boost the power of the engine in a confined space. It probably helped a little, just like the flow of fuel through the injectors to the tank, but then, the military has the big bucks to do things like that. ::)
LOL some of the things the military experiment with on the 2 strokes made absolutely no rhyme or reason.Walter those marine engine have almost the same PSI of boost as the highway engines
There are outfits that coat piston tops to reflect heat.
oltrunt,
I was a thermodynamisist in a former life, and to answer your question you need to look at the ideal gas law, which says PV=nrT. If V, n, and r remain constant, then if you increase the temp T then the pressure in the system must also increase.
Matt
Quote from: luvrbus on September 25, 2018, 02:24:51 PM
LOL some of the things the military experiment with on the 2 strokes made absolutely no rhyme or reason.Walter those marine engine have almost the same PSI of boost as the highway engines
Is there greater volume involved? Something sure accounts for all the extra horsepower in the marine versions. The military 8V71T had 440 hp, and the marine versions were 600+ hp.
Double Eagle
A marine 8v71 has the same volume as any 8v71. If boost psi is the same, the difference in horsepower would come from at what rpm the peak torque is measured. Using the formula HP= (RPM X T) / 5252 if you raise where the peak torque is measured from 1600 rpm to 2400 rpm you would also raise the horsepower by 50%.
Matt
Just like pickup truck diesel. Pour in more fuel, more horsepower, more heat. With unlimited ocean cool water, just pull out the heat.
Quote from: Beluga Bus on September 25, 2018, 03:37:38 PM
Double Eagle
A marine 8v71 has the same volume as any 8v71. If boost psi is the same, the difference in horsepower would come from at what rpm the peak torque is measured. Using the formula HP= (RPM X T) / 5252 if you raise where the peak torque is measured from 1600 rpm to 2400 rpm you would also raise the horsepower by 50%.
Matt
True, but what about the injector size differences, and timing? What about the effect of twin turbo's, would the pressures be higher, or would the volume of air flow be increased at the same pressures as single turbo's? The military 8V71T's were rated at 440 hp @ 2300 rpm (or 405 hp @ 2300 rpm), that is still a bit shy of marine specs. There must be other differences such as cam profiles.
If you look, at least in the DDA tune up section for 8V-71's, depending on application, the boost specs and injector size are all over the map. Seems max speed is up to 2300. I recall one engine with boost pressure in the 40's. Clifford probably has more info than I have on this. Don't know if he has any on marine.
I would think injector size and timing along with unlimited cooling capacity would be how they got those numbers. Loosing 20% of your fuel economy in a boat makes little difference, it would be like going from 0.5 mpg to 0.4 mpg.
Matt