Does "squish" pipe add back pressure

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Does "squish" pipe add back pressure


Post by 57pan » Tue Nov 07, 2006 2:59 pm

Description: Does "squish" pipe add back pressure?

I've always been curious about this and my other post about the rear cylinder running way leaner than the front got me to wondering about it again. I don't think that it would make as much difference as I am seeing but I've got to believe that it makes some difference.
What say ye experts?

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Re: Does "squish" pipe add back pressure


Post by Pantony » Tue Nov 07, 2006 9:40 pm

well using basic flow bench principals yes, when you take a round tube and crush some of it you will restrict flow so the answer is yes it will cause some back pressure; but I don't think thats your problem, still think you have a hairline crack somewhere

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Re: Does "squish" pipe add back pressure


Post by fourthgear » Wed Nov 08, 2006 10:05 am

Well that flat pipe would restrict flow if it was just flattened ,but its really not and thats not saying that its better than a round any thing as far as flow is concerned . Round any kind of pipe or duct will have better flow characteristics , but when the shape is changed , they are made larger to make up for the distortion of the round pipe, wider , longer etc. I'm sure they new that when the designed that flat pipe and compensated as much as they could to get a some what close flow characteristic of round. Ya need to look at the total inside surface area compared to a round pipe inside surface area, there are formulas for this stuff that dates back real far. When we start changing carbs., cams , valves , that were not designed back then and raising the performance levels of these motors with mod. technology , things may have to be adj. for them.
It is not uncommon to run two diff. plugs for HDs , one cooler ,one hotter to adj. for some conditions ,but that does not mean there is not something else going on .

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Re: Does "squish" pipe add back pressure


Post by 64DUOGLIDE » Wed Nov 08, 2006 9:07 pm

Maybe a dumb question, but, will the squish pipe come out without removing the engine? It doesn't look like it and I couldn't find anything in the manuals


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Re: Does "squish" pipe add back pressure


Post by 03Roadking » Wed Nov 08, 2006 9:17 pm

mine comes out real easy if I take the brake rod and the tab that bolts to the cross over shaft off but I don't have floor boards

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Re: Does "squish" pipe add back pressure


Post by fourthgear » Thu Nov 09, 2006 6:31 am

I have an S&S oil pump and it will not get past it, I had to install it in the frame before motor install , I've tried moving the lift with no help. Just one of those things that happen when you change from OEM. and I like the pump. I'm just glad it will not have be removed for anything any time soon. I really don't see a problem with it at all.

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Re: Does "squish" pipe add back pressure


Post by caschnd1 » Thu Nov 09, 2006 8:13 am

I also have the S&S oil pump but I have no trouble removing the S-pipe. I know the S&S pumps offer different locations for hooking up your oil lines so maybe it has something to do with which ports you select to connect your oil lins to.


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Re: Does "squish" pipe add back pressure


Post by Sidecar » Thu Nov 09, 2006 8:36 am

I'm also running an S&S pump. No problem getting the squish pipe out/off.

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Re: Does "squish" pipe add back pressure


Post by fourthgear » Thu Nov 09, 2006 9:16 am

Well then, I will have to check it out further ,but I have no reason to remove it unless I have to , I'm working on a packing or sealing system for that pipe and might remove it for fitting solutions( when I can't ride any more for the year , down here its a short winter ,if at all ). It still could be my lift getting in the way.

I'm in a 58 frame and I measured between the pump and frame and at most I have 1 1/2 inches ( not enough to squeeze that pipe Thu )any of you running a swing arm frame ,my frame is stock? Is my pump diff. ? Maybe I should try another angle next time ?

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Re: Does "squish" pipe add back pressure


Post by harpo55 » Sun Nov 12, 2006 9:04 pm

fourthgear-If I understand your post are you trying to fit the pipe underneath the oil pump? 03Roadking is right. Fit the pipe by removing the front brake assembly, this worked for me, you may have to take the floorboard off also. I had this problem and posted asking for advice some time back. As Billy said in his reply, "it's a wiggle jiggle fit" Dan

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Re: Does "squish" pipe add back pressure


Post by kell » Tue Nov 21, 2006 5:01 pm

Hey 57pan

I doubt if the squish makes much difference. People have been running squish pipes for longer than I've been alive. But for what it's worth you can calculate how much the squish reduces the cross section, relative to the round part of the pipe, very easy.

I'll illustrate with some madeup numbers. Say you measure the O.D. of the round section with a caliper and it's 2", and the squish part measures 1.25" by 2.75".
The proportion of the areas will be (1.25 X 2.75)/(2 squared). So for a pipe with the above numbers, the cross section of the squish would be 3.44 / 4 or 86% of the cross-section area of the round. If you do the calculations on your bike's exhaust it may give you a rough indication of the ability of squish exhaust pipe to flow gases relative to the other pipe... or it may not tell you very much at all

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