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Question regarding HP loss in pipes
To the experts (EXPERTS!!!):
Doesn't it stand to reason that if you have a set of pipes (no matter the brand, let's just keep them constant in this example), and you have 20-25% HP loss on average (expert opined), wouldn't you get a higher percentage of HP LOSS on a 800 HP engine vs a 400 HP engine? Remember, the headers and pipes are the same for both engines in this case. It would seem to me that the same headers/pipes would do more choking on a higher powered car. Or is the difference negligible? |
Yes, you're correct....
If you start at 500 fwhp and lose 20%, you've lost 100 and you're down to 400. If you start with 700 and lose 20%, you've lost 140 and you're down to 560. And I believe that if a certain size exhaust system is restrictive to a 500hp 400ci engine, it's going to be even more restrictive to a 700hp 500ci engine. |
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I'm not ready to believe that there's a linear relationship like that without some dyno testing using all the same equipment, but for the engine.
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Yep.
Take a 302....you can run a 1-5/8" header tube on that one....try running 1-5/8" headers on a 557 ;) |
Yep, Rod... I'm going to have to start drawing you graphs. I am just loving this thread.:LOL:
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Couldn't you design, let's say, and 850 HP SOHC engine, employing concepts of quench, piston/chamber design, cam and EFI technology, etc., etc., that would lose less HP through the sidepipes, as a %, than other 850HP FE engines? Are all 850 HP FE engines created equal.
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When I upgraded from my original PoS Classic Roadsters sidepipes to a custom set of stainles pipes, I picked up a ton of power. I did not dyno it but seat of the pants was day and night. Anyway, . . . I now have 4" oustide diameter stainless glasspack sidepipe mufflers with 3" inside diameter. We keep talking about hp losses of sidepipes, but it is hard for me to imagine that I am losing a lot with a straight thru 3" ID glasspack. The case is about 30" long, it is not a shortie. It sounds very good to me :o
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In my mind you cant do the math correctly based on percentages. If you have a motor that builds 500 hp and you put it on a chassis dyno and say that it looses 100 hp through the drivetrain. Now if you swap motors to more hp then the drivetrain still only takes 100 hp to turn. It doesnt take more hp to turn with a bigger motor...the tranny and dif dont know the difference. So with the 500 hp motor you lost 20% or 100 hp. With the 700 hp motor you lost 14.3% or a 100 hp....again the drivetrain doesnt know the difference. It takes X amount of force to turn X amount of weight...right? Now if you go trying to make that 700hp motor breathe through them 500hp headers and pipes....then the drivetrain is no longer a consideration. Im confused....lol Gene |
So, it all boils down to:
Performance, Reliability, or Cost. Pick any two. __________________ Thomas L. Kirkham, Jr., Vice President Kirkham Motorsports When designing any new parts, if you do not consider all three above, it is like designing a "three legged stool with only two legs". This is one of my "old" sayings. Lee |
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all I want(ed) to know is can I have a 427 FE motor (stock displacement) that can reliably hit the red line as often I choose and still have enough reliability to drive across the country w/o undue worry. Or do I need to limit my fun to low & midrange torque-type excitement? Z. |
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If you can fix anything at anytime, you know a McGruber type, then you da man. |
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Long story short the more hp you want to make the bigger the fire you gonna have to build. A 427 will make more hp and tq then you will ever be able to hook up anyway. Put it toggether with some good rod bolts, good head bolts and gaskets, a mild cam and let it go. Just my thoughts |
... and to think how much we've spent on our FEs and now most of us would just be happy if they went an entire summer driving season without breaking down. My car *might* make it coast-to-coast, but if I was going to place a heavy bet, I'd put my money on a break-down. Nothing terribly serious, but something requiring a garage and time. And it would be out in the middle of a cornfield somewhere, too....%/
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so the consensus is, consistently hitting a 6000 rpm redline in a 427 FE will put cross country reliability at risk.
Z. |
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