V4 Exhaust layout...

I am thinking about fabbing up my own stainless exhaust for my VF1000R, seeing how they are next to impossible to get pipes for... I have access to the bender and am a competent welder, but seeing how this bike is my 1st V-4 I am curious as to the layout of the exhaust. I would appreciate any feedback or ideas! It seems like all 4 cyl. dump into a common catalytic convertor and then get expelled. I am not sure about the exhaust pulses or cycles? Does it matter that much? Do I go side to side or front to back as far as tying the pipes together or shall I say, do I tie them 2 into 1, side to side or take the front and rear cylinders of the left side and vice-versa? I would like to use the cans that I had on my '98 VTR1000, I had a complete stainless Two Brothers system and they sounded awesome, I used to get alot of compliments on the sound of that bike... Any ideas? Thanks!

 

The VF1000R motor is closer to a pair of V2's, with the front pair on one system and the back pair on another. So, if it was me, and it will be this summer, I would pair the front (2-1) and pair the back, before and if I mate the front secondary with the back secondary, if you want a 4-2-1. Otherwise, try to get the front and back primaries and secondaries as close to the same length as possible. Thats why you end up with the bundle of snakes under the engine. Personally, I like front pair out the right, back pair out the left, into twin carbon cans, I like Yoshi.

Ask Jamie Daugherty, he knows everything.

Larry

 

Designing a V4 system is extremely difficult to do. Many people think an equal length header is the way to go - in fact that only works for an inline engine. Since the two cylinder banks are 90 degrees apart so are the pulse phases in the exhaust. The only thing you can do is to design the header such that it pulse-matches at a particular rpm and suffer to penalty everywhere else. Have you ever seen a dyno chart of a V4 with a Hindle header? They have a huge dip in the midrange - that is why.

This is a really big topic with lots of theory and science behind it. The bottom line is that you probably won't get it right the first time so be prepared for lots of trial and error.

 

I was looking at the exhaust chamber testerday and am wondering.... Is the chamber a type of catalytic convertor or no??? As I live in an area where we have to go thru emmissions testing, I was curious if I'm going to have to reuse this when I build the exhaust system or can I delete the chamber. Any ideas??? Thanks!

 

No, catalytic converters didn't show up on motorcycles until 20 years later. It's actually a mixing box, kind of like a collector but different. It takes the flows from the four cylinders and merges them in a way that balances out the flow over a broad range of rpm. It actually does a pretty good job. It's this chamber that is the reason why slip-ons cause a decrease in power on these bikes. Going to a collector design would help the flow but only over a narrow rpm range. If you look at a dyno chart for a V4 with a Hindle or similar 4-1 header you'll see a huge (and I mean huge) dip in power in the midrange - it's because the primary lengths are not tuned to that range but rather only the upper end. Once again, throw the concept of "equal length primaries" out the window because it does not apply here. The 90 degree phase angle shift of the cylinder bank makes that not applicable.

In theory, the best design header would be a 4-2 where you tie the two fronts together and the two rears together. In that scenario you could make the pair of tubes equal length because for each bank of two cylinders you have an even firing sequence. Just don't tie them together and it would be ok. I've never seen an aftermarket header done this way which makes me wonder if there is something else going on there.

 

I was thinking of trying to design a header system for my 83. When I had the exhaust off this winter I tried to see how the collector chamber was made. It looks like they have 2&3 paired and 1&4 paired sort of speak. The #2 pipe comes straight back in to the collector and exits straight out. While the #3 pipe comes in to the collector and is wrapped,inside, to exit the left side of the collector where #2 does. The #4&1 does the same and exits out the right pipe.

That being said. My thoughts were to either tie the pairs together with their own collector each. Then tie the 2 collectors together with a tube like a crossover pipe.
Or build a single collector similar to the OEM. As far as equal length I don't think you need both banks equal to each other. Just make each bank 2&4, 1&3 equal to themselves. One bank would work better at higher rpms and the other in the mid range. This hopefully would give a wider overall power band. That's what it looks like Honda did. But without solid numbers I'm just guessing.

If you'd like help playing around with this I'd be interested in helping some way.

 

That would be ok, prodviding that you maintain 1-3 and 2-4 tied together. A crossover would be ok, but that doesn't really provide much of a benefit. In fact, it would probably hurt you more than it would help. Also, trying to tie the two sets together would cause some hassles with phase timing.

 

Just to toss this idea out there... What about running individual pipes for each cylinder to individual mufflers, kind of like the old hondas had? I don't mean actually using the "chrome" megaphones but using 4 small individual mufflers kind of like what you might see on two stroke GP bikes... I thought I vaquely remember seeing somewhere, an exhaust system that used small cans like those and had it on a 4 stroke engine?... Is this a feasible possibility or will it just "kill" the powerband? If I could find some small cans and keep them kind of "tight" together, maybe that might not look too bad... I don't want to have a "hack" looking job on this restoration but wouldn't mind it lookin' a little like a GP bike.... Ideas?

 

Individual pipes do not take advantage of the scavaging effects of the other cylinder(s). It would not have the midrange dip issue, but the power would likely be a bit lower across the board. Not a bad idea though!

 

yea bro i wanted to do the samething but when i started it was a bitch to find anyone that can bend that small of a pipe..good luck with :thumbsup:

 

You would have to get pre-bent pipes from a header maker or possibly have them custom bend a few pieces. Just like making any other header. It's cut,fit, tack, refit, recut, then finally weld.

Jamie got any info on the design physics of Honda's V4 exhaust? It would be a interesting read. The phase timing can't be that big of a deal. The stock collector is still open to all cylinders. All the pipes enter the collector, stop inside and don't really go straight thru. The exhaust pressure is pointed in a certain direction. I think that's were the mid range comes in, in the scavenging of the exhaust from the collector volume and the two exits. Then the higher rpms the exhaust pressure is pointed to basically exit one side or the other. With help from it's pair cylinder pulse. Of coarse this is just a guess. I haven't read or even looked for info about Honda exhaust design.

 

Oh my, it's extremely complicated. The physics involved are far beyond what I can type here. It involves flow theory, frictional losses as well as temperature/density factors. Pretty much there is a way to calculate it, but it's not a single formula but rather a large matrix filled with lots of variables. For those variables, you need to have data to plug in, of which there is nowhere to find this data - you have to generate it yourself via testing. There is a scientific method but it requires a lot of R&D and expensive data acquisition equipment.

Phase timing is the complication here, so it's a very big deal.

 

in other words find a hindle! good luck on finding one to

 

Hi Jamie , I need your experience, I would like to put bigger tyres on my vf 500 without changing the wheels and I have two options : 130/70 rear and 110 / 70 front or 130/80 and 110/90. Pirelli sport demon is the tyre. Can you give me a suggestion?

 

Honestly, just keep with the stock sizes. Putting on different tires on the same wheels doesn't really offer anything. In fact, the rear would just get taller and distorted but wouldn't really be any wider. The only way to get more/better tires is by changing the wheels unfortunately.

 

Here is a cutaway view of a VF500F collector box:

(photos: GAZVF500, VFRD)





This is an interesting topic,,,I'm wondering which system is better: 4-1s or 4-2s (paired on cylinders 1|3 and 2|4 w/ staggered mufflers, as show in the photos below).

(photos:Captain 80s, VFRworld)

 

on the 7th gen, Honda paired the front ( 2 -1 ) and the rear seperate from the front ( 2 -1 )
they are not = so 2 cyln work for top end and the other for low end.
I'm interested to see the engine specs on the cross runner? headers to see if the design give any more low end vs the 6th gen set up.
too bad they will not be selling them in the states.

 

info from the press release I was invited to in NY last year.
I will see if I can find the info and scan it in.

they all do go into one muffler at the end but the header tubes are not equal front and back.