I ran a post last week called a new exhaust trick. Come to find out it was an old trick. It was new to me. Well as I told you, I installed two bolts in my baffles about the size of my thumb. I as shocked at the torque I gained, but I felt like i gave up some top end. Well I have three sets of baffles thanks to the Harley shop in the collision department. So I drilled another baffle out and put one bolt rather than two. Again the size of my thumb. It still gave me torque but I had a little more top end. Then I took the baffle out all together and ran it. I had plenty of top end but lost the torque.
Im trying to understand this engine. If you restrict the exhaust, it seems you get better gas millage and torque but you give up top end. Take away the restriction and you get top end hp and less gas millage. And finding a happy medium after a engine build can be a tuff one to say the least.
All that I’ve said is in laymen’s terms, I would love to hear a more professional translation of what happens with the harley engine and why when you restrict the exhaust you get torque and good gas millage. And how in the hell do you find the happy medium ofr optimum hp & torque.

 

Get any book by D. William Dennish and read them, If you can get all four, read and absorb them you will have earned a PHD with a Harley V-Twin major.

 

If you want to get even fancier with that old trick, make you some lollipop baffles. They are just 1" washers welded on the stem of a 1/4" bolt. You can turn them to make a tuneable restriction. I have them just in front of the mufflers on my RKC.



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What a brilliant idea. Truly brilliant. Now for the second question. Tuning. What are you looking for in the tuning department. More torque or power ? It seems to me that if you restrict the engine to a moderate degree you get a large amount of low end torque and good gas millage. Who would of figured that ? And how do you know when you have to much restrection ?

 

When you open up the exhaust and let the exhaust out faster it creates more scavaging which pulls more freshair through the combustion chamber. If youdon't add more fuel it goes lean taking away torque.It's not the good old days befoe E.P.A.


Ride on !!!

 

I've been doing that trick for about 20 years. Easy way to be able to run straight pipes but not loose all the torque!! Works well to tune mufflers as you've shown.

Rev

 

It also has a lot to do with the pulsation through out the entire system, all the way to the intake. Allowing more back pressure will make for a more even, dampened flow into the cylinder as well.Less flow, more velocity.Same reason you keep intakes smooth and small for low end torque and smooth and large for high end gains.

 

To be honest. I was fasinated that you could restrict the exhaust and get such torque out of the engine. The gas millage was great. You can make a harley engine pretty quick, but i believe its a torque cruising engine. Not really made to drag with.

 

Check this site out http://www.bigcitythunder.com/pages/product-fit.html these guys have figured this stuff out. I ran some of their baffles on my 1600 Vulcan and it really made a difference. Their stuff is so simple it's incredible, but it works. Let me know what you think.

Best,
J

 

Very informative postings. I went to the V&H 2-1 Pro Pipes from SE-ll's when I changed out the carb and noticed a large increase in torque throughout the entire band. Not into speeds over 80 and don't race. Thanks for the explanations.