header on backwards
06-21-2011 | 08:36 PM
#1
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From: Frederick,
MD
header on backwards
hey so im thinking about relocating my exhaust to behind the rear wheels, i have an rx8 body for my rs4 and i know the exhaust will fit behind the rear wheels. couple reasons for wanting to do this.
1) it will keep the car cleaner, the exhaust gases get all over the right side of the car anytime i drive it
2) it will be a fun little project
3) i dont want to cut a hole in the side of my rx8 body... i know its sad but i love the way it looks so the only way ill allow myself to drive the car with the rx8 body on is if it is rear exit exhaust. i havent driven it yet with the body on because of the side exhaust.
anyway, thats my plan, and the way i was going to go about doing this was screwing the exhaust header on upside down, and then soldering a copper pipe together that holds the exhaust pipe.
my only question, and im pretty sure this will be okay, but i like to run a bit rich, and if there is leftover nitro that sits in the header, after i turn the engine off, that nitro will flow back to the engine, and im wondering if that will be bad for it.... its not a lot of nitro but its a little bit sometimes
thanks<br type="_moz" />
1) it will keep the car cleaner, the exhaust gases get all over the right side of the car anytime i drive it
2) it will be a fun little project
3) i dont want to cut a hole in the side of my rx8 body... i know its sad but i love the way it looks so the only way ill allow myself to drive the car with the rx8 body on is if it is rear exit exhaust. i havent driven it yet with the body on because of the side exhaust.
anyway, thats my plan, and the way i was going to go about doing this was screwing the exhaust header on upside down, and then soldering a copper pipe together that holds the exhaust pipe.
my only question, and im pretty sure this will be okay, but i like to run a bit rich, and if there is leftover nitro that sits in the header, after i turn the engine off, that nitro will flow back to the engine, and im wondering if that will be bad for it.... its not a lot of nitro but its a little bit sometimes
thanks<br type="_moz" />
06-22-2011 | 05:02 AM
#3
Senior Member
RE: header on backwards
Two things;
1 - If you are running so rich that you have unburnt fuel, as opposed to unburnt oil, then you're not "a little" rich, you're way rich. Being too rich is as bad for one of these engines as too lean. If you wanna run rich, fine, but raw fuel in the exhaust means you are more than a little lean.
And, yes, allowing raw fuel to sit in the engine can be bad for the engine.
2 - If you add length to the exhaust you will alter the back pressure in the pipe and, at a minimum, alter the power band and could seriously affect the power the engine produces.
1 - If you are running so rich that you have unburnt fuel, as opposed to unburnt oil, then you're not "a little" rich, you're way rich. Being too rich is as bad for one of these engines as too lean. If you wanna run rich, fine, but raw fuel in the exhaust means you are more than a little lean.
And, yes, allowing raw fuel to sit in the engine can be bad for the engine.
2 - If you add length to the exhaust you will alter the back pressure in the pipe and, at a minimum, alter the power band and could seriously affect the power the engine produces.
06-22-2011 | 06:15 AM
#4
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RE: header on backwards
ORIGINAL: DaveG55
Two things;
1 - If you are running so rich that you have unburnt fuel, as opposed to unburnt oil, then you're not ''a little'' rich, you're way rich. Being too rich is as bad for one of these engines as too lean. If you wanna run rich, fine, but raw fuel in the exhaust means you are more than a little lean.
And, yes, allowing raw fuel to sit in the engine can be bad for the engine.
2 - If you add length to the exhaust you will alter the back pressure in the pipe and, at a minimum, alter the power band and could seriously affect the power the engine produces.
Two things;
1 - If you are running so rich that you have unburnt fuel, as opposed to unburnt oil, then you're not ''a little'' rich, you're way rich. Being too rich is as bad for one of these engines as too lean. If you wanna run rich, fine, but raw fuel in the exhaust means you are more than a little lean.
And, yes, allowing raw fuel to sit in the engine can be bad for the engine.
2 - If you add length to the exhaust you will alter the back pressure in the pipe and, at a minimum, alter the power band and could seriously affect the power the engine produces.
He is probably running the stock HPI motor with the stock pipe, and if that is the case, the powerband is probably not all that great to begin with. Adding a little header length will not effect it that much, it may take a little off the bottom end... but barely enough to notice.
06-22-2011 | 06:48 AM
#5
Senior Member
RE: header on backwards
No, I don't think I misunderstood at all.
If there is unburnt FUEL, not just oil, it's too rich. The only time I have signifigant amounts of unburnt fuel in the exhaust is during the first two or three tanks of break-in. If there is fuel in the exhaust that can get back inside the engine it can cause harm.
As for the header, adding, or removing, as little as 1/4" can make a difference in power band and performance. If he's thinking of adding copper pipe then he's thinking about adding, what, an inch or more? That will absolutely change the powerband and performance. Will he be able to tell? With that engine, his tuning and his unknown experience level, I cannot say, but change it, it most certainly will.
And I do understand the frustration with the oil on the side but it's really just the nature of the beast. Changing where the pipe exits will only change the part of the body that gets oily.
And lastly, I was not discouraging him from trying, simply telling him some things he may not know.
If there is unburnt FUEL, not just oil, it's too rich. The only time I have signifigant amounts of unburnt fuel in the exhaust is during the first two or three tanks of break-in. If there is fuel in the exhaust that can get back inside the engine it can cause harm.
As for the header, adding, or removing, as little as 1/4" can make a difference in power band and performance. If he's thinking of adding copper pipe then he's thinking about adding, what, an inch or more? That will absolutely change the powerband and performance. Will he be able to tell? With that engine, his tuning and his unknown experience level, I cannot say, but change it, it most certainly will.
And I do understand the frustration with the oil on the side but it's really just the nature of the beast. Changing where the pipe exits will only change the part of the body that gets oily.
And lastly, I was not discouraging him from trying, simply telling him some things he may not know.
06-22-2011 | 07:38 AM
#6
Senior Member
My Feedback: (2)
RE: header on backwards
Well, to be fair, he said "gasses"... which I read as being the exhaust that ends up all over every car.
Even a lean running engine will blow fuel through the exhaust. Pass your finger over the stinger and let some of the moisture accumulate, then blow on your finger a little. That cold feeling is the left over nitro methanol evaporating. These engines do not (and cannot) completely burn the fuel, as there is no true ignition inside the engine like there would be a gasoline powered engine. The fuel mix compresses, then a chemical reaction occurs between the compressed fuel and the platinum on the plug, causing a rapid expansion. Because there is no "explosion" taking place, the fuel does not completely burn. If you have ever flown rc planes, you would know about what the methanol in the exhaust does to crappy coverings.
Even a lean running engine will blow fuel through the exhaust. Pass your finger over the stinger and let some of the moisture accumulate, then blow on your finger a little. That cold feeling is the left over nitro methanol evaporating. These engines do not (and cannot) completely burn the fuel, as there is no true ignition inside the engine like there would be a gasoline powered engine. The fuel mix compresses, then a chemical reaction occurs between the compressed fuel and the platinum on the plug, causing a rapid expansion. Because there is no "explosion" taking place, the fuel does not completely burn. If you have ever flown rc planes, you would know about what the methanol in the exhaust does to crappy coverings.
06-22-2011 | 06:43 PM
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From: Frederick,
MD
RE: header on backwards
ORIGINAL: proanti1
Well, to be fair, he said "gasses"... which I read as being the exhaust that ends up all over every car.
Even a lean running engine will blow fuel through the exhaust. Pass your finger over the stinger and let some of the moisture accumulate, then blow on your finger a little. That cold feeling is the left over nitro methanol evaporating. These engines do not (and cannot) completely burn the fuel, as there is no true ignition inside the engine like there would be a gasoline powered engine. The fuel mix compresses, then a chemical reaction occurs between the compressed fuel and the platinum on the plug, causing a rapid expansion. Because there is no "explosion" taking place, the fuel does not completely burn. If you have ever flown rc planes, you would know about what the methanol in the exhaust does to crappy coverings.
Well, to be fair, he said "gasses"... which I read as being the exhaust that ends up all over every car.
Even a lean running engine will blow fuel through the exhaust. Pass your finger over the stinger and let some of the moisture accumulate, then blow on your finger a little. That cold feeling is the left over nitro methanol evaporating. These engines do not (and cannot) completely burn the fuel, as there is no true ignition inside the engine like there would be a gasoline powered engine. The fuel mix compresses, then a chemical reaction occurs between the compressed fuel and the platinum on the plug, causing a rapid expansion. Because there is no "explosion" taking place, the fuel does not completely burn. If you have ever flown rc planes, you would know about what the methanol in the exhaust does to crappy coverings.
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