Pipe issues????

[Anders_Martinelle]

I have a question about pipe "funktion".

On one of my 45 boats i have a qiute bad sling shot effect.

It goes very rich in low and medium rpm but when the pipe start to "pump" it just accelerate untill it runns lean and burn the plug.

I know that there was a topic along time ago that the descussion were about stingers and people that had problem that their boats whent lean and rich after a couple of laps.

Terry keely i think it was that wrote something about drill a hole to release or regulate the pressure.

Never mind, what can i do to get more pressure to the engine so it dosen`t run lean??

It takes 50-100m to come back hard if i make a short throttle down .....

Anders

 

[HendricX]

What brand of pipe on what engine ?

And how long is it set ?

What carburator is on it , and how many needles ?

 

[Terry Keeley]

I have a question about pipe "funktion".On one of my 45 boats i have a qiute bad sling shot effect.

It goes very rich in low and medium rpm but when the pipe start to "pump" it just accelerate untill it runns lean and burn the plug.

I know that there was a topic along time ago that the descussion were about stingers and people that had problem that their boats whent lean and rich after a couple of laps.

Terry keely i think it was that wrote something about drill a hole to release or regulate the pressure.

Never mind, what can i do to get more pressure to the engine so it dosen`t run lean??

It takes 50-100m to come back hard if i make a short throttle down .....

Anders

Hey Anders:

I had that problem with my Green Head CMB .67, I had to flow a lot of fuel to keep it rich enough at full throttle to not burn a plug, but when I slowed down it went very rich and took 1/2 a lap to get going again. I tried leaning the low end needle on the 9B, messed with the cooling, tried different plugs, pipes, props, all to no avail.

Finally tried one of the newer "hemi" heads with a smaller volume and fixed it, I can mill around now at part throttle and hit it and it takes right off. Might be something to look at...

What motor, pipe, prop, boat, plug, nitro...

 

[Anders_Martinelle]

What motor, pipe, prop, boat, plug, nitro...

I left all that out of this because of the tendensy of slide of to something totaly different topic.....

I know that the pipe is making this problem because i tested another pipe and the problem goes away but also the very good performance it gives.......

That`s why i wonder how i can control the "pressure" or if its possible or not????

Anders

 

[Ian Inverarity]

Anders,

I'm not sure this is your problem, but if the stinger is too small or muffler too restrictive the back pressure in the pipe can be too high resulting in too much heat in the combustion chamber and detonation taking the plug. This can happen despite a rich mixture, so it may seem as if the engine went lean and took the plug even tho that isnt what happened.

Ian.

 

[Anders_Martinelle]

Good point Ian............

Because when i opend the engine both head and piston is starting to melt (head and piston completly dull) and of course it`s not long before the plug goes then.

And yes it can have some backpressure bue to the DB level we need to run at .

Anders

 

[Terry Keeley]

PM sent, I'll repeat it here and maybe someone else can help.

Sounds like the AB "parabolic" at 9" might be a little short if it's getting warm there. I run OPS 6280's on a similar setup (CMB HR45, 60%, HP's) but find 9" a little "pipey" in the heat, 9 1/2" is much more "raceable".

Really don't think it's a stinger issue...

 

[Anders_Martinelle]

Hmmm........

Strange sometimes, yesterday i mounted a OPS 6280 pipe on it to test this weekend.......

Also i set it at 235mm which is 9,25", not long from what you have.

You run std stinger??

I will test it Terry and i post the result.

Anders

 

[Terry Keeley]

The stock stinger diameter is way too big, I reduce mine to 3/8" (9.5mm) by using an internal stinger. Is the volume (cone diameters) similar to the AB parabolic? What's the stinger diameter?

 

[Anders_Martinelle]

Terry, i don`t have the stinger size here.

Going to mod the OPS alittle then.

Volume is quite similar so i willl make some tests.

Also going to test some other pipes to see what will work with that engine.

Anders

 

[Terry Keeley]

Sounds good, let us know how it goes...

 

[Anders_Martinelle]

Terry, i was at the lake today and tested some pipes.

The OPS 6280 i have i have mounted a stinger that is 60mm long and 9,5mm in the hole.

It goes around 35mm inside the pipe now.

What length are you useing???

After some runns i found that 242mm was the shortest w/o starting to have problem.

Still with some lag but np to get going hard within 10-20m.

Next time i will make the engine alittle more "user frendly" in the timing <_< .

BUT!!! in the end of my pipe test session there was another pipe that i will use at the worlds.

Little lag but good power :lol: :lol: .....

But thank`s for the tip of the 6280 pipe with the mods Terry.

Will continue to work on that.

Anders