Flow vs power question

[davesax36]

How would a too-open exhaust burn a valve?

If a 4-1 pipe went from 2-> 2.25 inches to a huge, open chamber, would that cause any weird problems?

Any thoughts on whether it could cause a dip in power when the vboost comes in?

Just thinking about things and my frankenpipe.

 

[blaxmax]

How would a too-open exhaust burn a valve?

If a 4-1 pipe went from 2-> 2.25 inches to a huge, open chamber, would that cause any weird problems?

Any thoughts on whether it could cause a dip in power when the vboost comes in?

Just thinking about things and my frankenpipe.

Lots of old drag racers used to run open headers believing restricted airflow was slowing them down. Some said no restriction on the exhaust would burn valves but highly unlikely.
It has never happened to me or anyone I know personally.

 

[davesax36]

That's what I thought. I just saw it mentioned in an old post and started wondering.

 

[DMAN999]

I'd think it would cause you bike to run a bit richer and a LOT louder.
Due to the design of our intake and exhaust system when you open up the exhaust more gas is pulled into the carbs causing a rich condition which is the exact opposite of most vehicles.
From what I know going too lean would burn up your valves, etc.
Running a bit rich, shouldn't hurt the motor, but it may lose you a few HP.

 

[davesax36]

That, too. I have a dip in power right at 7k. I just noticed it yesterday. I'm not sure if it's a needle springs issue, or a shimming issue, or what. I'll start fiddling with it. I do know that nothing went wonky until I put this pipe onto my Hindle header. We'll see what actually happened. Maybe I need to go all the way to 147.5s. I could also need to reset my float levels. We'll see how much work I'm willing to do. It's not like it's bad, it's just not quite the same. And my mileage went way down into the low-mid 30s from consistently 40+.

 

[DMAN999]

That, too. I have a dip in power right at 7k. I just noticed it yesterday. I'm not sure if it's a needle springs issue, or a shimming issue, or what. I'll start fiddling with it. I do know that nothing went wonky until I put this pipe onto my Hindle header. We'll see what actually happened. Maybe I need to go all the way to 147.5s. I could also need to reset my float levels. We'll see how much work I'm willing to do. It's not like it's bad, it's just not quite the same. And my mileage went way down into the low-mid 30s from consistently 40+.

I would think one size smaller mains will help if your feeling the loss/stumble up around 7k.
You might want to consider adding or re-packing your baffles too, that may help a bit.
I run Supertrapps on my stock jetted 2000 and when I run open caps (equal to around 10 discs) it definitely runs quite a bit rich compared to when I run 8 discs and closed caps.
I'm actually going to drop my mains down to Mikuni 150's because even with 7 or 8 discs and closed caps it runs a bit rich compared to when I had the stock exhaust.

 

[davesax36]

The exhaust comes out with pretty good force at idle. I'm not sure if that's even a thing, though. I guess that just means it's getting pumped out.

 

[blaxmax]

On the headers of my dragster I put a spark plug in each one towards the end of the openings to burn off any excess fuel.

 

[DMAN999]

Dave do your current Cans even have baffles or they just empty cans (basically straight pipes) ?
What cans are they ?
Do you have pictures you can post ?

 

[davesax36]

It's an FZ1 pipe. Lemme find a pic. There's a guy on Facebook who did the same thing with his, but he has the Hindle big tube pipe, so it fit right on. Mine is the other one that's 4-1 with a 2" pipe. The FZ1 can has no packing, but is the indirect flow style where the exhaust goes into a couple different chambers indirectly before exiting.

I'm building another one that's basically a big open chamber, but I'm working on figuring a way to make a 2.25" baffle in there with a ton of packing around it that flows out the 1.5" outlet after traveling through another void (See my awesome MSPaint skills). That might not work at all, but it seems like it would be cool, so I'm gonna try it since I have two identical pipes here.