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-   -   Straight Pipe Myths (http://www.hotrodders.com/forum/straight-pipe-myths-49513.html)

Mollard 10-10-2004 09:26 PM

Straight Pipe Myths
 
Does running striaght pipes ruin your engine?

If so, what causes the premature engine faluire?

Jmark 10-10-2004 09:48 PM

Running straight pipes does not harm the engine. Running open headers does not hurt the engine either.

Thinking years ago was that cold air hitting the exhaust valves could damage or warp them, but when A.I.R. pumps came into use to curb emissions, that "thinking" went away too.

Straight pipes may be a little loud and a few neighbors (like me!) might be a little hostile if you run them, but the choice is yours.

Mark

bonuts 10-11-2004 12:35 AM

Wouldn't lack of any back pressure be bad for performance? Or is that a myth too?


bonuts

Steve-0321 10-11-2004 12:43 AM

If you have a stock cam in a all stock engine then you will probably be in trouble............i was running straight pipes on my 351C 2V motor and there was no torque at all because of the cam i was told..........if you got the cam......then you should be ok....but its noisy as heck....i wouldnt suggest it

DoubleVision 10-11-2004 06:38 AM

There is some truth to this, and that is, a stock engine or one modified, either way, stock exhaust changed to true duals with straight pipes, no other changes, the valves get cooked, due to the mixture being too lean, any time that back pressure is reduced, the mixture must be richened to compensate, since back pressure was reduced the engine can now pull in more air/fuel and when it`s not richened more air is added but fuel is not, hence it being too lean which results in excessive cylinder heat and the exhaust valves get burned or a piston gets hollowed.

Mollard 10-11-2004 07:51 AM

So if the air fuel mixture is richened should be alright? I am thinking about doing this on my '83 Mazda B2000 becasue I want to run some flame thowers on it. I was thinking about running a straight pipe al the way out back and dumping it just behing the paasenger side tire.

How will I know when I get the right air/fuel mixture?

bowtieorbust 10-11-2004 03:28 PM

(IMO) if i were to run an open exhaust right out the back, instead of a (2 1/4) or a (2 1/2) in. pipe, i would problebly go down to a 2'' exhaust to give some velocity to it, but i believe the straight pipe ordeal will get old quick. :rolleyes:

BstMech 10-11-2004 04:41 PM

You will blow your motor with any kind of exhaust modification.

I had a guy tell me this one time and it's believable to an extent.

He told me that those great sounding pipes will have you revving your motor all the time to get that........great sound. :P

Old School Nut 10-11-2004 07:16 PM

that warping the valves myth i think started in WWII with fighter planes, and their realy short headers. suposidly an airplane (like a P-51, spitfire...) could do a manuver that could introduce enough of a cold air blast to warp the valves... i dont know if this is true.

trees 10-11-2004 07:55 PM

The old fighter planes had an entirely different set of problems to work with. The P 51 was liquid cooled where as most of the others were air cooled. The air cooled engines had cowl flaps to maintain cylinder heat temps in the "green" to prevent detonation (hot) or excessive fuel consumption (cold) These flaps were open for take off and landing and were mostly fully closed when at high altitude cruise. Opening the cowl vents too early or going full open at too high an altitude could cause rapid cooling and a bunch of warped heads, jugs etc. The P 51 radiator cooling air could be regulated also, but usually was not required. The unique way the aircraft was flown for the long range, high altitude bomber escort missions was developed by Charles Lindberg. Upon reaching cruise altitude and airspeed, they would lean the engine back until it quit, then slowly increased enrichment until it fired and then they set the throttle and mixture there. As fuel burned off, they would slowly climb, maintaing air speed and throttle/ mixture settings. Lindberg had to prove to all the old time aircraft engine mechanics that this procedure and super lean fuel mixtures did not damage the engines. His procedure increased the range of the aircraft by about 50% and were the only aircraft that could escort the bombers to Berlin and beyond.

Trees

Mollard 12-06-2004 09:52 AM

So what about these "rat rods" that run a 2 foot peice of pipe of of each cylinder? If the air/fuel mixture is richened, you should be ok?

BTW, this isn't on a high preformance engine, just a stock 350.

Siggy_Freud 12-06-2004 10:02 AM

You dont have to run straight pipes to run flamethrowers.

First off before even attempting to do flamethrowers, research research research. And then go buy yourself a fire extinguisher.

A few companies make full flame kits while others just make a spark box that provides a "feed" to the coils you mount back there causing the sparkplugs to rapid fire. You then have to design a fuel or propane feed system. When my vehicle was carbed I ran a 3way filter to two fuel solenoids, one closer to the filter, and the other back closer to the fogger nozzle.

The fogger nozzles were a good two feet from the sparkplugs in the tail pipes.

Just remember to keep safety in mind as much as you can if doing this sort of project. The results can be very cool but also very hazardess. If an officer of the law sees you doing this . . . you'll be talking about the cool car you USED to have lol.'

Research on google and you'll find some good starting info.

Stickman 12-06-2004 02:02 PM

Quoted from "Trees" :"The old fighter planes had an entirely different set of problems to work with. The P 51 was liquid cooled where as most of the others were air cooled. The air cooled engines had cowl flaps to maintain cylinder heat temps in the "green" to prevent detonation (hot) or excessive fuel consumption (cold) These flaps were open for take off and landing and were mostly fully closed when at high altitude cruise. Opening the cowl vents too early or going full open at too high an altitude could cause rapid cooling and a bunch of warped heads, jugs etc. The P 51 radiator cooling air could be regulated also, but usually was not required. The unique way the aircraft was flown for the long range, high altitude bomber escort missions was developed by Charles Lindberg. Upon reaching cruise altitude and airspeed, they would lean the engine back until it quit, then slowly increased enrichment until it fired and then they set the throttle and mixture there. As fuel burned off, they would slowly climb, maintaing air speed and throttle/ mixture settings. Lindberg had to prove to all the old time aircraft engine mechanics that this procedure and super lean fuel mixtures did not damage the engines. His procedure increased the range of the aircraft by about 50% and were the only aircraft that could escort the bombers to Berlin and beyond."

You know, I knew that, someday, my being an extreme WWII fighter aircraft freak would come in useful (sort of). :D

Ok, some mis-information in the above...not intentionally incorrect, certainly, just not quite on-the-mark in some areas.

First:
Most WWII fighters were liquid cooled, rather than the other way 'round. All USN fighters flown from CV's (aircraft carriers) were air cooled, of course (the Navy refused to use liquid cooled fighters aboard ship), but most Allied USAAF, RAF, etc. were water cooled, with some notable exceptions such as the Jug (P-47), and the Hawker Typhoon (RAF ship).



Secondly, Lindberg's foray into the South Pacific and his work done with a fighter group down there did, indeed, greatly benefit the US as far as fuel economy goes, but his ideas to lean out throttle mixtures (and other things) were met with resistance because of the lean mixtures themselves, which, as we all know, can cause an engine to run hotter, and allow detonation at a far lower power loading. This was the primary concern...that the lean mixtures, even at cruise settings, would be certain death to an engine (most of his testing was done on P38's, twin-Allison engined turbo-supercharged fighters) because the turbo boost would cause detonation at those leaner settings, burning holes in pistons and cooking valves. He proved this wasn't the case by flying his ship "leaned out" while others in his flight flew theirs in the conventional manner (not sure how many sorties he flew this way..I could probably look it up, but I'm too lazy...it was more than just a few, I'm certain) and afterwards, the engine was torn down and inspected, and found to be in perfect condition. This simple adjustment doubled the range of the P38, and did much toward helping us win the war in the Pacific....With so little land, and most sorties, by necessity, lasting as much as 8 hours or more, it was a miracle for those fighter pilots who fought in that theatre.

Finally:
Cowling flaps on those ships that had them ( the P47, F4U Corsair) were generally opened only during METO power setting, or WEP, when the extra cooling ability was absolutely needed. A P47, for example, could increase turbo/supercharger boost enough to gain over a 33% horsepower increase, using water injection, and understandably it generated enormous amounts of heat. Also, the P51's cold air induction was often used, in the heat of combat when high power (boost) settings were used. I've never read (or been told...I've inverviewed a number of WWII fighter pilots) about jugs being cracked because of overcooling, though that doesn't necessarily mean it isn't true...

P.S.
If any of you guys want to know anything about WWII fighters, just ask...I probably know the answer, whether it's concerning combat tactics and maneuvers generally used by specific aircraft pilots, powerloading differences between aircraft, or even loadouts and ordnance capabilities for specific aircraft....or historical facts about engagements, fighters, etc. Alot of this information is extremely tough to find these days, and I'd be happy to pass it on if I know it :D

packratwrecker 12-06-2004 04:52 PM

If you decide to run straights, keep in kind that the bigger pipe you use, the more mellow the tone will me.
2" sounds nasty on a small block chev, a 6.2 diesel, a v-6 Explorer, or a 230 straight 6, with split manifolds.
If you are going to do flamethrowers with mufflers, I'd use glasspacks, or steelpacks. If you try it with trash cans, and make a mistake, you'll end up with mufflers that look like pregnant puppies.
I ran straights on my 49 Chev, out 4" stacks, until I couldn't stand it anymore.
I took the stacks off at the elbows, and welded in blocker plates, with glasspacks on them. Most people don't even know I have mufflers, until I tell them.
The 4" stacks above the glasspacks gives a pretty effective expasion chamber, so you get nice orange rolling fire, instead of blue jets.

FYI I am a redneck. I built my own flamethrower setup, so that it would be safe, and easy to use.

Dubz 12-06-2004 05:00 PM

the p51 also used water injection did it not to supress detonation and increase milage?


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