Knock, pulled timing and the low octane maps
Originally Posted by nj1266
Don't wrap your dp. Here is why:
Hi,
Wrapping the downpipe is NEVER advisable. You want to have as little heat and back-pressure behind the turbo. Otherwise you lower its efficiency. Meaning it's harder on the turbo and the engine and you make less power, but create more knock probability.
Regards,
Klaus
and:
Hi,
When you wrap the downpipe (behind turbo) you keep heat in the exhaust gas. Heat equals pressure because the exhaust behind the turbo has to flow a higher volume. This increases exhaust speed, that's true, but the flow resistance (and therefore back pressure) goes up with the square of the gas speed.
A turbo (turbine side) runs best and most efficient with as little back-pressure as possible. Remember, the turbine in a turbo runs off the mass-flow of gases, which is dependent on the pressure difference between in and out of a turbine. You want to maximize that pressure difference.
Therefore it is advisable to wrap the headers BEFORE the turbo. This keeps the energy in the gas that the turbo uses to function. I'm too busy to calculate the % right now, but wrapping the downpipe is equivalent to reducing it's diameter.
Heat in the engine compartment would much more likely come from the turbo housing itself and the primaries (which can be wrapped). The downpipe will not contribute as much as it is quite a lot cooler. The high pressure exhaust gas expands in the turbo and thereby cools down.
Regards,
Klaus
http://www.innovatemotorsports.com/f...ead.php?t=4000
Hi,
Wrapping the downpipe is NEVER advisable. You want to have as little heat and back-pressure behind the turbo. Otherwise you lower its efficiency. Meaning it's harder on the turbo and the engine and you make less power, but create more knock probability.
Regards,
Klaus
and:
Hi,
When you wrap the downpipe (behind turbo) you keep heat in the exhaust gas. Heat equals pressure because the exhaust behind the turbo has to flow a higher volume. This increases exhaust speed, that's true, but the flow resistance (and therefore back pressure) goes up with the square of the gas speed.
A turbo (turbine side) runs best and most efficient with as little back-pressure as possible. Remember, the turbine in a turbo runs off the mass-flow of gases, which is dependent on the pressure difference between in and out of a turbine. You want to maximize that pressure difference.
Therefore it is advisable to wrap the headers BEFORE the turbo. This keeps the energy in the gas that the turbo uses to function. I'm too busy to calculate the % right now, but wrapping the downpipe is equivalent to reducing it's diameter.
Heat in the engine compartment would much more likely come from the turbo housing itself and the primaries (which can be wrapped). The downpipe will not contribute as much as it is quite a lot cooler. The high pressure exhaust gas expands in the turbo and thereby cools down.
Regards,
Klaus
http://www.innovatemotorsports.com/f...ead.php?t=4000
I would never wrap a downpipe or a header, but I do ceramic coat them. With 05+ EVOs, the ACD & oil pan should be protected from heat, which make the coating a great idea. Also, faster exhaust gases is good, but like Klaus said, you want less back pressure (I dont know/think that coating increases backpressure)
I know you love Klaus and that he is the super engineer, but I dont think he works on EVOs. WORKS recommend coating their DP and O2 housings. Also Buschur coats the manifold and their O2 housing.
If Klaus is right, then why do top EVO tuners coat exhaust parts after turbo??
EDIT: Exhaust wrap usually lead to cracked exhaust pieces. Ceramic coating is the way to go and the only method I endorse.
Last edited by Evo_Jay; Jul 28, 2006 at 02:38 PM.
Originally Posted by Evo_Kid
If Klaus is right, then why do top EVO tuners coat exhaust parts after turbo??
The wrapping tends to trap moisture which accelerates the decay and fatigue of the parts.. Thermal coating has mostly superceded the wrapping these days..
Most of us don't wrap the downpipe or coat the downpipe because we want to let the heat escape after the turbo.. I did make some heat shields for some other parts, but the only time real wrap is used these days is to prevent extreme heat from damaging a part adjacent to the hot part.. I've been using adheasive heat shield material on my lower intercooler pipe to protect it from the heat of the downpipe and dump tube.
Most of us don't wrap the downpipe or coat the downpipe because we want to let the heat escape after the turbo.. I did make some heat shields for some other parts, but the only time real wrap is used these days is to prevent extreme heat from damaging a part adjacent to the hot part.. I've been using adheasive heat shield material on my lower intercooler pipe to protect it from the heat of the downpipe and dump tube.
Originally Posted by Evo_Kid
I would never wrap a downpipe or a header, but I do ceramic coat them. With 05+ EVOs, the ACD & oil pan should be protected from heat, which make the coating a great idea. Also, faster exhaust gases is good, but like Klaus said, you want less back pressure (I dont know/think that coating increases backpressure)
I know you love Klaus and that he is the super engineer, but I dont think he works on EVOs. WORKS recommend coating their DP and O2 housings. Also Buschur coats the manifold and their O2 housing.
If Klaus is right, then why do top EVO tuners coat exhaust parts after turbo??
EDIT: Exhaust wrap usually lead to cracked exhaust pieces. Ceramic coating is the way to go and the only method I endorse.
I know you love Klaus and that he is the super engineer, but I dont think he works on EVOs. WORKS recommend coating their DP and O2 housings. Also Buschur coats the manifold and their O2 housing.
If Klaus is right, then why do top EVO tuners coat exhaust parts after turbo??
EDIT: Exhaust wrap usually lead to cracked exhaust pieces. Ceramic coating is the way to go and the only method I endorse.
Originally Posted by AlwaysinBoost
On every turbo car I've owned I wrapped/coated exhaust parts and didn't notice any loss in performance. I mostly did it to keep engine bay temps down which worked excellently. I'm not disagreeing with what Klaus is saying, just giving my real world input.
Originally Posted by nj1266
RMR sells a heat shield that you can glue to the oil pan where the dp passes. I believe SCC did a review of the part and said that it works.
Also I was think bout it, if the exhaust gases in a coated/wraped DP go faster, wouldn't there be less backpressure???
if less backpressure = faster exhaust gases
wouldn't faster exhaust gases = less backpressure
sorry to the OP for going off topic
Originally Posted by nj1266
Did you do a before and after dyno testing or 1/4 mile testing to see the impact of wrapping?
this isn't an EVO but you get the idea...
Originally Posted by razorlab
Did you?
Originally Posted by nj1266
Don't shoot the messenger. If you want to wrap your dp, then have at it. I am just relating to you what a knowledgeable automotive engineer said about this. Do whatever the heck you want.
Originally Posted by nj1266
Wrapping the downpipe is NEVER advisable. You want to have as little heat and back-pressure behind the turbo. Otherwise you lower its efficiency. Meaning it's harder on the turbo and the engine and you make less power, but create more knock probability.
Regards,
Klaus
and:
Regards,
Klaus
and:
It does keep heat off the oil pan, also transfer area
Last edited by C6C6CH3vo; Jul 29, 2006 at 05:28 AM.
Originally Posted by razorlab
Any other engineers you can copy paste in here?
Last edited by nj1266; Jul 29, 2006 at 07:05 AM.
Originally Posted by C6C6CH3vo
I thought heating the gases behind the turbo will only increase the energy accross it from the higher velocity of gas evacuation
It does keep heat off the oil pan, also transfer area
It does keep heat off the oil pan, also transfer area
Nah, it offers very little value after the turbo, in fact the expanding gases exiting are supposed to help reduce backpressure, while before the turbo and at the header, keeping the heat in keeps up the velocity.. I suppose it doesnt really make "sense", but my theory is that as the heat is shed in the exhaust system, and the gases expand, it draws additional waste gases with it.. A high pressure/temp area to lower pressure/temp area.. Some sort of thermodynamics going on.. Turbo cars obviously dont benefit from exhaust scavenging in the same way as a Normally aspirated car would, so I think the benefit of wrapping the downpipe may only be heat control and not gain you much at that point.
The common theory on wrapping/thermal coating is..
If you need to protect other components from the heat, you heat wrap, if you need to retain the heat inside the component, you thermal coat.. Some do both, especially if you have a hot part, next to a part that needs to remain cooler...
If you want to do it, its not going to hurt anything except the lifespan of the downpipe.. If your doing it to eliminate some sort of rattling on the downpipe to the crossmember or some other component, then I would use some sort of insulator instead to keep it from rattling.
The common theory on wrapping/thermal coating is..
If you need to protect other components from the heat, you heat wrap, if you need to retain the heat inside the component, you thermal coat.. Some do both, especially if you have a hot part, next to a part that needs to remain cooler...
If you want to do it, its not going to hurt anything except the lifespan of the downpipe.. If your doing it to eliminate some sort of rattling on the downpipe to the crossmember or some other component, then I would use some sort of insulator instead to keep it from rattling.
Take the same amount of heat energy going into two seperate but identical ducts of somewhat restrictive diameter. The one that is insulated and retains more temperature will evacuate the gas better, right?
I do see the point about heat differential accross the turbo, but were talking DP wrap and not on the O2 housing
I do see the point about heat differential accross the turbo, but were talking DP wrap and not on the O2 housing