Honda CBR 1000RR Forums banner
Status
Not open for further replies.

Coolant / Fuel catch tank question

3K views 9 replies 3 participants last post by  itguru77 
#1 ·
Need some help with catch tanks. Can anyone provide a detailed explanation on the purpose of using a catch tank for the fuel (i.e. routing the air breather from the fuel tank to the catch tank). I understand the use for the radiator overflow to a catch tank, but confused on fuel. The HRC manual says "Route the fuel tank breather hose properly and connect it to the fuel tank", but what about the overflow? Also the image shows 2 hoses routing into the fuel catch tank. Can someone please elaborate on the second hose, and also what happens with the overflow hose from the fuel tank.
 

Attachments

See less See more
1
#2 ·
I've never set one up on my track bikes, but my understanding is if there is any issue with the tank pressure where it needs to vent or relief, or even just the small amount of vapor that leaks out of the hose occasionally, it's better to have the breather hose routed to a catch can rather than underneath the bike where the hot engine and exhaust manifold are located. It's not exactly a common occurrence, but cheap insurance. I think it's more prominent if you run high octane race fuel that is more susceptible to heat. It also looks like there is a check valve to prevent any backflow (underneath the brake reservoir)? Someone might be able to chime in and give more info but that's what I've heard.

That actually happened to a senior superbike racer at IoM TT this year: he noticed fuel dumping through the clear line routed over the tank, was able to see it, pulled off immediately and shut the bike off. If it was routed underneath to the atmosphere, then it would have gone unnoticed and could have been much worse...

EDIT: some extra info I found...

http://www.tanksinc.com/index.cfm/page/ptype=results/category_id=160/mode=cat/cat160.htm
 
#4 ·
Was that a requirement for the organization you were in or just recommended? Obviously that makes sense as well, but I only ask because most don't seem to care so long as you have a proper belly pan to catch the fluids. I've only heard of people using one out of paranoia for a fire rather than a requirement now-a-days. Still, it's definitely a safer idea than just letting it drain into the pan or all over the pavement.
 
#6 ·
There is no requirement I am trying to meet specifically, as when I was racing I just ran them to the belly pan as well, and they inspected those heavily. Just a journeyman mechanic, trying to learn the tricks of the trade, and the most professional way (from a race mechanic's perspective) to setup for racing. But thank you all for providing this information.
@MotoMott and all, so I certainly understand your point concerning fuel overflow to the belly pan close to the exhaust as opposed to a catch can. You are also correct as HRC manual mentions the optional 1-way valve preventing potential backflow. Having said that the diagram shows the line being ran from the tank being the air breather. So I read the link you posted (thanks for that), and clarifies why you would want to run the air breather in such as way. So I would run the fuel and coolant via their own separate lines to catch cans, but what could be the purpose of running the air breather to the catch can as well as shown in the image? I am wondering if they actually mean the fuel overflow and not the air breather line. Your thoughts anyone? I will also reach out to the race shop where I order my parts from to see if they can provide some clarity. Thanks again everyone.
 
#7 ·
@itguru77 I was actually taking a look at this on my bike last night and thought the same thing when I looked back at the diagram - sorry, I didn't catch what you originally meant. I did notice that on the Honda parts diagram they list all the hoses as a "breather", so it might just be a general classification. If I remember correctly (see the attached photos, found them from a 600RR website but it's a similar design), the vent/breather line is actually lower than the overflow is at the top of the tank. So in the event pressurization, it would first flow out of the vent tube and the overflow would be a secondary discharge. Unfortunately I am not certain though; it would be nice to get some clarification.



 
#8 ·
@MotoMott that's an interesting point. That could very well be why?, the 2 overflow outlets on the bottom of the tank are connected to the air breather line with the T-Joint. This was perplexing and the only thing I could figure was that the plastic T-Joint had a 1-way check valve. But now that you mention the breather being primary before overflow hose I am really not sure. Here are some pics the race shop sent me. They build WSB bikes, and don't speak English but at least they sent me something. One thing I also noticed is they do not route the outbound hose to the belly pan as some videos show (that never made sense to me, why you would route to the same place as the stock reservoir anyways). They just run the second hose right out of the catch can and zip tie to the sides. If you notice the last 2 picture focus on fuel, and it appears that the yellow fuel tygon terminates right before the air box. Now they also sell a air breather hose for fuel that is custom. So I am guessing that this custom hose may have the 1-way check valve at the end towards the catch can. The last picture shows what looks like this custom cable being routed around the bottom of the air box. Having said that you noticed again for fuel, the outbound hose is simply zip tied to the can; hence only 1 run is being made. So back to what you were saying I wonder 'if the air breather can continuously provide a path for the fuel' is this why we don't see a second line running out for the fuel overflow hose itself? Also when you mentioned the TT racer who pulled over immediately when seeing fuel; wondering if he abruptly pulled over because there is no guarantee that the primary overflow (air breather) will 100% remain primary, and only pass fuel to the overflow in the absence of a working air breather. It is still perplexing because, when looking at the hose configuration at the T-Joint, there doesn't appear to be a mechanism by which the this behavior can be controlled; unless according to your drawing this behavior is being controlled inside the tank.
 

Attachments

Status
Not open for further replies.
You have insufficient privileges to reply here.
Top