Mechanical fuel pump flow rate

[AK260]

Does anyone know the actual flow rate of the mechanical pump?

 

I am tempted to support mine with an electric pump. - a facet silver top as it’s not too juicy on pressure for my SUs (with a regulator of course) but their literature says it’s good for up to 200bhp - mine makes anywhere from 230-245 depending on whose dyno it’s on! ;)

 

But the difference between a silver top and a red top is only 10% more flow for the red top. Yet the red top is quoted as 200+ applications. But what does the “+” mean if it’s only 10% more flow? 10% more power or infinity!? ;)

 

But foremost I’m interested to know the flow of the mech pump - can’t seem to find it in the FSM I have.

[Patcon]

Might be able to calculate it based on the FSM test

[AK260]

Might be able to calculate it based on the FSM test

Thanks sir, I will look into it! [emoji106]

Interestingly, the online fuel flow calculators all converge on around 18-20 gph (imperial) for 240bhp, so the silver top at 30 should be OK I think. [emoji848]

[Patcon]

I would think in a support role the electric pump would flow even more because the mechanical is helping pull somewhat

[AK260]

I would think in a support role the electric pump would flow even more because the mechanical is helping pull somewhat

I have to agree with you there! [emoji106]

I like keeping the mech pump - i may also look into a bypass set up on the elec pump in case it ever fails.

The problem is never fitting these things, it’s the stuff we put around them like not using the wiring loom supply and adding inertia cut off relays etc ;)

[Zed Head]

On 10/6/2021 at 12:15 AM, AK260 said:

Does anyone know the actual flow rate of the mechanical pump?

Doesn't it depend on engine RPM?  It's eccentric actuated.

 

[AK260]

22 minutes ago, Zed Head said:

Doesn't it depend on engine RPM?  It's eccentric actuated.

 

Fair point, I guess I was looking for max flow at 6K RPM where the engine "should" be thirstiest.

[Zed Head]

I can't think of a single time where I've read about the need for a higher capacity mechanical pump.  Never read of any engine running lean because the mechanical pump couldn't keep the float bowls full.  It might be a thing but I've never heard of it happening.  A mechanical pump delivers a certain volume of fuel with each pump, and the pumps are tied to each engine revolution which also pumps about the same amount of air.

Doesn't really help your quest but I don't think that you can make a direct comparison between the two types of pump.  One's capacity increases automatically, the other's is constant.