Topic: CB750 Wet Sump Conversion - Sumpthing

[voxonda]

Only downside of the oem tubing is the rather small diameter of 35mm. But I do love the curve of them.
A preferred 4-2-1 on one side of sump would kill ground clearance so had to opt for two individual 2 into 1 and join behind sump. Rather have the #1 and #4 coupled and #2 and #3 due to firing order  but cant have them all. Maybe in a later stage.

[gschuld]

Gotcha.  I was wondering how you were going to fit it all on the right side.  It’s going to be an interesting transition with 2 singles coming back together, joining together with a Y and out one side well clear of both the rear of the Sumpthing and the rear tire without having a small radius turn on one of the pipes.  I’m digging your creativity regardless.

George

[simon#42]

Yes one and four , two and three will give the best power .

[voxonda]

Gotcha.  I was wondering how you were going to fit it all on the right side.  It’s going to be an interesting transition with 2 singles coming back together, joining together with a Y and out one side well clear of both the rear of the Sumpthing and the rear tire without having a small radius turn on one of the pipes.  I’m digging your creativity regardless.

George

There is enough room behind the sump to join without too small radius tunes. Buit still working on some idea's. We will see.

[scottly]

Rob, you may want to consider merging the head-pipes together in front of the sump, so there is only a single pipe on each side running past the sump? As far as effect on performance with shorter primaries, only the dyno will tell.

[voxonda]

Scott, it is something I also consider. But it does effect the power output. It would make the routing of a single pipe next to the sump easier.

[gschuld]

FWIW, Carpy’s Yoshimura copy pipes have gone through several suppliers and versions.  Some hang quite low under the engine.  In fact, for a visual example, the one pictured below looks to clear an oil pan lowered 2”

Might it be worth considering for a road racer simply going under the Sumpthing along the centerline assuming the ground clearance isn’t an issue.🧐

George

[bwaller]

What about a flat (4 in a row) collector directly under the pan? I don't know the results in such a case, but have seen them before. It would take your special touch to fab a cool piece.

[gschuld]

What about a flat (4 in a row) collector directly under the pan? I don't know the results in such a case, but have seen them before. It would take your special touch to fab a cool piece.

Right, like the early Murray pipe, similar to the later Monty Campbell X-pipe

George

[simon#42]

thats not a great pipe , for max power you need to find a way to pair the pipes together 1 and 4 , 2 and three the lengths of the headers is also crucial .
looking at your first design you are not only going to loose power you also have reduced ground clearance considerably .
i think the only way to make it work is to go under the sump some how

[754]

I am betting smaller primary   make more torque..

[simon#42]

you went to school cal ?

[voxonda]

I am betting smaller primary   make more torque..

Diameter, length of primaries make torgue up or down scale. Form and length of the collectors too.

[Tintop]

Rob given this going to be a chop and fit exhaust, why not try and incorporate Captain's (Brent H) 360 degree design.  The NASCAR boys use very flat collectors for ground clearance, maybe some packaging ideas there?

[gschuld]

Rob,

You are going for something like this right, squeezing around the sump?

George

[scottly]

I am betting smaller primary   make more torque..

Smaller primary diameter made less torque on the FT 500, AKA Ditch Pump.

[voxonda]

Rob,

You are going for something like this right, squeezing around the sump?

George

 

Thuis could be, but still thinking of other options too.

[voxonda]

thats not a great pipe , for max power you need to find a way to pair the pipes together 1 and 4 , 2 and three the lengths of the headers is also crucial .
looking at your first design you are not only going to loose power you also have reduced ground clearance considerably .
i think the only way to make it work is to go under the sump some how

That "loosing" power is something we will see at the Dyno. In my experience it is fractional but the reduced ground clearance is my main concern too. Agree that coupling 1&4, 2&3 is favorit but in this stage need to come up with a usable system to test the wet sump. Now looking into having the both collector side by side under the oilpan. Looks promising.

[gschuld]

thats not a great pipe , for max power you need to find a way to pair the pipes together 1 and 4 , 2 and three the lengths of the headers is also crucial .
looking at your first design you are not only going to loose power you also have reduced ground clearance considerably .
i think the only way to make it work is to go under the sump some how

That "loosing" power is something we will see at the Dyno. In my experience it is fractional but the reduced ground clearance is my main concern too. Agree that coupling 1&4, 2&3 is favorit but in this stage need to come up with a usable system to test the wet sump. Now looking into having the both collector side by side under the oilpan. Looks promising.

Rob, perhaps something like this would be ideal.  1/4 and 2/3 pipes together, and coming together tight side by side under the pan, then merge to 1 and out.  It’s a more difficult fabrication challenge getting those primaries shaped like that though😒

George

[voxonda]

Hi George,

Thanks for sharing your thoughts! Yes this is also a possibility, but since the main goal is to be able to test the wet sump and not trying to find the perfect exhaust (yet), I decided to go my first route, but by replacing the collectors side by side under the pan to still have decent lean angle. Advantage is that the oil plug is free. So now I have to do some welding and painting the primaries. Now have to place the silencer and secubdary collector and then create the connection pipes. But I am getting there......

Rob

[gschuld]

Looks great Rob.  It’s easy for me to suggest difficult to create design ideas when I’m not the one who needs to actually create them😏 🙄

George

[dragracer]

I had an 1-5/8" sidewinder on my kz dragbike for years. I scrapped the pipe on the return road at some point and put a small hole in the collector where all the tubes joined. Screwy spot to reweld so I went out and bought myself a brand new, big tube V&H prostock replica pipe. I put the pipe on the bike thinking it would help since I had a 1425cc engine. Well, much to my surprise and total disappointment, the bike lost numbers from one end of the track to the other. The 70' time went up, the ET went up and I lost mph. Needless to say, I found a competent welder to repair my smaller diameter pipe and the bike picked up performance again. Moral of the story; bigger is not always better.

[dragracer]

I had an 1-5/8" sidewinder on my kz dragbike for years. I scrapped the pipe on the return road at some point and put a small hole in the collector where all the tubes joined. Screwy spot to reweld so I went out and bought myself a brand new, big tube V&H prostock replica pipe. I put the pipe on the bike thinking it would help since I had a 1425cc engine. Well, much to my surprise and total disappointment, the bike lost numbers from one end of the track to the other. The 60' time went up, the ET went up and I lost mph. Needless to say, I found a competent welder to repair my smaller diameter pipe and the bike picked up performance again. Moral of the story; bigger is not always better.

[voxonda]

Wether a pipe works, or not, depends on so many factors. You are right, bigger is surely not always better.

[voxonda]

Little by little the exhaust is getting its (rough) shape.