My very stock '74 CS hesitates over 85 MPH but revs freely in the garage and in lower gears on the road, so I'm thinking fuel delivery problem more likely than insufficient advance problem. It has a big FI canister style filter mounted on the firewall before the mechanical fuel pump, so I just changed it and cut the old one open. Yes there was some grit but not a lot, and my goodness there's a lot of dense folded filter material in there, isn't it hard for a mechanical pump to suck through all that?
Is a FI filter too restrictive for a mechanical pump and carbs?
- Thread starter Eric V
- Start date
That should not be an issue. I use the Tii metal filter on all my BMWs.
OK good to know. Just got back out there with an engine analyzer and timing gun and verified a rock solid 22 DBTDC at 1700 RPM with vacuum advance and retard disconnected. And the rotor is not the rev-limiting kind. Will keep investigating.
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Oh HBChris are you running the fuel filters before or after the fuel pump?
Before the pump next to the firewall.
Always nice when the solution actually works!
mechanical pump for carbed, gives 0,21 bar
electric pump for FI gives 10 times more
i would not use the big filter, there is no need
I’ve been using them for years, they work great with mechanical pumps.
That was my thought; FI high pressure pump pushes through small pore filter, low pressure mechanical pump may struggle to suck through that resistance, may do better pushing through a larger pore filter between pump and carb.
Honolulu
Well-Known Member
The other principle of physics to consider in all pumping situations is the rate of flow. In this case the FI engine receives enough flow even though the filter is fine, because the pump "pushes" enough volume past the resistance. The carbed engine might struggle because the piston-driven pump doesn't have the pressure to move the fuel through. This could be worse when the filter is between the pump and fuel tank.
Unless the whole situation is balanced such that the flow and pressure will always be sufficient to feed either engine, using either filter, before or after the pump. A good mechanical designer would in that way "idiot-proof" his product and prevent problems which might result from well-intentioned owners, 50 years down the road.
Unless the whole situation is balanced such that the flow and pressure will always be sufficient to feed either engine, using either filter, before or after the pump. A good mechanical designer would in that way "idiot-proof" his product and prevent problems which might result from well-intentioned owners, 50 years down the road.
Here is a new one, pretty compact. You can breathe through it if you wish, very little to no resistance.
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means nothing, air is a different animal...and your lungs are not TÜV tested
on the other hand alu filter looks out of place in a carbed car, bigger is not better
IMHO
Well yes, then there’s that: as I understand it the only fuel filters as built were a metal screen in the tank sender and another in the fuel pump.
We have differing opinions, no need too beat a dead horse.
Mhhh... I don't know. I'd call it an interesting discussion...
Too much drama for me