The V8 Owners Forum -

Hi,

I have a quad downdraught dell'orto setup to be fitted to my V8 (when i finally finish it!) on John Eales manifolds.

Now has anyone connected up all the runners with small diamater piping to run vac systems such as servo brakes?????

I am considering a megajolt system which usually uses a MAP sensor. however one runner would be too pulsey, and I am worried I might loose some of the strong carb signal and mid torque by connecting up all the runners.

Any ideas guys???

There are various options here, on the megasquirt web site they recommended an acumilator set up, basically a hollow can with a small diamiter pipe (same size as the pipe for the MAP sensor) in either end the size of he can needs to be at least 1/4 the volume of 1 cylinder though it is doesn't matter too much provided it is big enough to dampen the pulses. You can put a further restriction in the in the pipe feeding from the venturi to fine tune the set up. If you want to refine it further you could add a feed from another venturi, I would make it one 180 deg away from the first, you would definatly need a restriction in the feeds to the can then, but the can could be a bit smaller. The trouble with joining them all up is you have a huge potential for leaks and it would not be easy to trace them.
You could lake a totaly different aproach and use 2 or even 4 MAP sensors and then sum the outputs with an op amp and stick a low pass filter across it and feed that into the megajolt.
Best regards
Mike
Best regards
Mike

Sounds like theres no simple solution! surely even an acumilator that was 1/4 of one cylinder would still see pulses?

or does it rely on the very narrow tube to restrict the mass flow rate so that the pressure change in the acumilator is less transient? I would imagine a 1mm2 area of tube or something would be needed...

2 or more MAP sensors and an op-amp would be a good solution, however the sensors are like 30 quid so it would start to get expensive...

the other option is the throttle position sensor, however they are flimsy and prone to damage in my experience and prob not suited for an off road vehicle...

I have John Eales manifolds (albeit with injection throttle bodies) and have them drilled for a vacuum line, I get a reasonable map signal for the megasquirt and also use it for my brake servo, you can see the pipes in the picture below and the accumulator on the right hand side, in the middle just in front of the battery.

Wow that looks like a nice setup mate. Havent I seen that photo on the 'Rover V8 inlet manifold archive?'

So ou've had no problems linking up all the runners? What ID tubing do you use?