Mvvs 77 + Pipe
10-02-2002 | 03:39 PM
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From: weston-super-mare, UNITED KINGDOM
Mvvs 77 + Pipe
I am having trouble setting up an MVVS 77 rear exhaust plus pipe
(purple pipe - Just Engines).
Prop 12X11 APC
Fuel - 16%synth-4%castor-5%Nitro
Plug OS 8
The recommended length from the supplier was 560mm to the first baffle plate. The motor was not happy with this.
I reduced to 550mm and got 9600 rpm-motor still not happy.
According to an experts article I have on tuned pipes the following calc can be used to give a starting length for pipes.
Length = Exhaust timing X 1200 / RPM (expected)
In my case this is:-
Length = 145 x 1200 / 9600
= 18.125 inches (460mm)
A lot less than suggested.
I reduced to 490mm - revs up to 10300 motor not quite happy yet.
If I now use the new revs (10300) on the calc then the result is a length of 430mm - shorter again and 130mm less than I was recommended to use!
This is as far as I have got. I would like someone who knows what they are doing (I don't) to make some suggestions.
The pipe length now does look too short although the revs have gone up.
Motor is also throwing out a lot of very black residue.
Franny (fed up & oily)
(purple pipe - Just Engines).
Prop 12X11 APC
Fuel - 16%synth-4%castor-5%Nitro
Plug OS 8
The recommended length from the supplier was 560mm to the first baffle plate. The motor was not happy with this.
I reduced to 550mm and got 9600 rpm-motor still not happy.
According to an experts article I have on tuned pipes the following calc can be used to give a starting length for pipes.
Length = Exhaust timing X 1200 / RPM (expected)
In my case this is:-
Length = 145 x 1200 / 9600
= 18.125 inches (460mm)
A lot less than suggested.
I reduced to 490mm - revs up to 10300 motor not quite happy yet.
If I now use the new revs (10300) on the calc then the result is a length of 430mm - shorter again and 130mm less than I was recommended to use!
This is as far as I have got. I would like someone who knows what they are doing (I don't) to make some suggestions.
The pipe length now does look too short although the revs have gone up.
Motor is also throwing out a lot of very black residue.
Franny (fed up & oily)
10-02-2002 | 07:22 PM
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From: sydney, AUSTRALIA
MVVS Pipe
Fran,
Just pulled the original equipment MVVS pipe and rear exhaust manifold (for MVVS 61-77) out of the boxes. Manifold is 130mm long and pipe is 310mm to the middle of the convergent cone. Total 440mm. I believe this way of measuring is the correct way to compare a pipe with baffles.
I have the 61 as rear exhaust but have not run this set up yet.
What do you mean by "not happy"? There are symptoms for incorrect length! Needle hard to set would indicate pipe to short, for instance.
Black oil in a fuel with castor is fine. FAI fuel makes a fantastic mess!
Oily by choice!
Just pulled the original equipment MVVS pipe and rear exhaust manifold (for MVVS 61-77) out of the boxes. Manifold is 130mm long and pipe is 310mm to the middle of the convergent cone. Total 440mm. I believe this way of measuring is the correct way to compare a pipe with baffles.
I have the 61 as rear exhaust but have not run this set up yet.
What do you mean by "not happy"? There are symptoms for incorrect length! Needle hard to set would indicate pipe to short, for instance.
Black oil in a fuel with castor is fine. FAI fuel makes a fantastic mess!
Oily by choice!
10-03-2002 | 07:57 AM
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From: weston-super-mare, UNITED KINGDOM
Mvvs 77 + Pipe
Not happy - not getting a consistent run - mid range pickup poor.
Motor in Tai Ji 60.
About to try a larger prop -12.5X11 before reducing length more.
Motor in Tai Ji 60.
About to try a larger prop -12.5X11 before reducing length more.
