Ducati.org forum banner
1 - 5 of 5 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
Hi. I am in the midst of making some engine mods such as 800 heads, altered 900 cams, new larger valves necked and swirled, porting and polishing. Probably not a lot new to any one but I have found the engines at full noise seem to have a lot of reversion with big cams. I am wanting to know if anybody has tried using anti-reversion headers???? I will be making them myself and was keen to hear from anyone who had tried them. What size was used, weather it was dynode and the end result. Any help is appreciated.
 

·
Registered
Joined
·
342 Posts
I did much research on this when I was into Harleys , and they need every bit of help. Cones and crap dont work , thousands of dollars and hours do . I ended up going with a proven brand and reapedthe gains.
RB Racing LSR 2-1 Exhaust Technology
Read through this , entertaining , and a twin after all said and done
 

·
Registered
Joined
·
2,996 Posts
A good read.

I also spent ten years doing this exact work. Length of the header pipe is as critical as tube diameter and is dictated by the valve timing/peak engine RPM. Many hundreds of hours of real world engine dyno time proved to us that a properly designed merge collector (much like a miniature megaphone) will produce SIGNIFICANT gains. The entry and exit angles of a merge collector are also critical and each engine wants something just a bit different. To quote one example we gained SIXTY HP on a 400ci sprint car engine purely by changing the merge collector angles and merge diameter without changing the pipes or the final collector diameter.

While there are mathematical calculation formulae to help achieve 'ideal' length and diameter, in truth this only gets you close to that magical/perfect combo. Small adjustments in either direction can sometimes find that bit extra. After a decade doing nothing else..... knowing what direction to go can become 'instinctive' based on past experiences and how the engine sounds under load. When everything is exactly what the engine wants the gains are huge. I have seen drag race engines spike dramatically in power by shortening or lengthening the header pipes by as little as 2 inches!

The custom made collectors I made for my Hyper (I tried 3 different variants of merge collector and secondary collector length) found me an extra 8hp at the wheel and 6ft/lb of torque through the mid range. This was proven by back to back comparison power runs about 15 minutes apart on the dyno.

Simplified....... A perfect collector/megaphone/etc won't work if the header pipes are the wrong length and /or diameter (or both) and vice versa...... however when you get BOTH of them right and working WITH each other the smile on your face is very, VERY wide!!!

Over the years I also noted the longer the valve duration and greater the valve overlap the louder and more noticeable the reversion becomes, especially under high load at lower RPM. Matching the correct length velocity stacks with headers also finds a few extra ponies.
 

·
Registered
Joined
·
342 Posts
I have a custom Harley from years ago running a 124ci motor. It had the must have 2 into 1 exhaust from some manufacturer That I cant remember , Then I put on an exhaust from these guys(RB) that was specifically made for the 124 S&S motor and wow what a difference .
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #5 ·
Anti-reversion headers

Thanks Tassie.
I have read that article on exhaust tuning and found it to be good reading. It is more a general discussion rather than an in depth report but still good reading. I have dealt with that company many years ago when I turbo charged a BMW for a fellow. A good group of people to work with.
I think I will do some more research and calcs and wait a little longer to do anything by then I should have my dyno up and running.
 
1 - 5 of 5 Posts
Top