Wedge fuel pumps
Discussion
by the look of my engine bay the other day, it pumps more than 0.5 gallons a minute 
.
I need to change the Swirl pot once the filter comes in the post.
when it does, I use the pump to empty the tank. and I'll time how long it takes to fill-up a 1 gallon petrol can.
I know steve heath has to use two pumps but he's over 500BHP.
I sould be ariving this week.
.I need to change the Swirl pot once the filter comes in the post.
when it does, I use the pump to empty the tank. and I'll time how long it takes to fill-up a 1 gallon petrol can.
I know steve heath has to use two pumps but he's over 500BHP.
I sould be ariving this week.
maybe better to take off the pipe from the filter and drain it that way, only a thought. 
Right.....
If your engine is getting beyond the 300+ bhp level then the standard fuel pump is marginal in that if the pump starts to fail, the risk of pre-detonation and piston melting or worse is increased. The more the engine's power is increased without improving the fuel delivery, the higher the risk.
When I had the first incarnation of the 520SE's big engine (350 ish bhp with a single ACT throttle) John Eales warned me then about ensuring the right pressure of fuel and more importantly the lack of it and the effect on the engine. A drop in pressure at high revs/load can cause pre-detonation and melt a piston and potentially shrapnel an engine. Put another way, it is worth spending a few more pounds to insure that the thousands of pounds investment in the engine doesn't go bang.
So the alternatives are one big pump or two slightly smaller pumps. I went the two smaller pumps on the grounds that if one pump failed the other would maintain pressure rather than have a complete lack of it. I also have two billet fuel filters so if one gets blocked, it is not a complete disaster. I also have seperate fuel pump switches so I can run either or both or most usefully neither (makes clearing flooded engines very easy).
It is virtually impossible to measure a pump's ability simply with a bucket. Several reasons. You need to know the flow rate at the required fuel pressure which means testing in situ. Secondly, the pump supply voltage has a big effect as well and running a pump at 14.4 v will give a very different reading at 12 or even 11. The bigger pumps will also take a lot of current - 20-30Amps per pump is not uncommon in my experience. Seperate fuses so that a fuse failure doesn't take but both pumps BTW.
I use FSE pumps and these have pressure/flow charts. You need at least 20% more capacity to maintain the fuel pressure especially when flooring the throttle and a big gush of fuel is needed. I could hear the pumps go into overdrive when I floored the throttle. The regulator works better with consistent excess pressure. So rather than say I need such and such for 320 bhp work back from the max injector rates, multiply by 8, and then see how that flow compares at the required pressure rate. Then make sure each pump can provide that. Alternatively get the biggest and fit two ready for when the engine gets more upgrades. I got the biggest FSE pumps around at the time.
Budget around the £500 mark for a couple of race spec pumps and filters. If the engine is staying around the 350 bhp mark then a second standard pump would do fine as the overall capacity of the two pumps combined is more than needed and gives a big safety margin. I still suggest using a couple of billet filters though.
I also have a digital fuel pressure guage with low pressure alarms that indicate problems. This is is also hooked up into the car's data logging so I can see if a misfire is caused by a fuel pressure variation. Might be paranoid but the costs are peanuts compared to the time and money that has gone into the engine over the years.
If your engine is getting beyond the 300+ bhp level then the standard fuel pump is marginal in that if the pump starts to fail, the risk of pre-detonation and piston melting or worse is increased. The more the engine's power is increased without improving the fuel delivery, the higher the risk.
When I had the first incarnation of the 520SE's big engine (350 ish bhp with a single ACT throttle) John Eales warned me then about ensuring the right pressure of fuel and more importantly the lack of it and the effect on the engine. A drop in pressure at high revs/load can cause pre-detonation and melt a piston and potentially shrapnel an engine. Put another way, it is worth spending a few more pounds to insure that the thousands of pounds investment in the engine doesn't go bang.
So the alternatives are one big pump or two slightly smaller pumps. I went the two smaller pumps on the grounds that if one pump failed the other would maintain pressure rather than have a complete lack of it. I also have two billet fuel filters so if one gets blocked, it is not a complete disaster. I also have seperate fuel pump switches so I can run either or both or most usefully neither (makes clearing flooded engines very easy).
It is virtually impossible to measure a pump's ability simply with a bucket. Several reasons. You need to know the flow rate at the required fuel pressure which means testing in situ. Secondly, the pump supply voltage has a big effect as well and running a pump at 14.4 v will give a very different reading at 12 or even 11. The bigger pumps will also take a lot of current - 20-30Amps per pump is not uncommon in my experience. Seperate fuses so that a fuse failure doesn't take but both pumps BTW.
I use FSE pumps and these have pressure/flow charts. You need at least 20% more capacity to maintain the fuel pressure especially when flooring the throttle and a big gush of fuel is needed. I could hear the pumps go into overdrive when I floored the throttle. The regulator works better with consistent excess pressure. So rather than say I need such and such for 320 bhp work back from the max injector rates, multiply by 8, and then see how that flow compares at the required pressure rate. Then make sure each pump can provide that. Alternatively get the biggest and fit two ready for when the engine gets more upgrades. I got the biggest FSE pumps around at the time.
Budget around the £500 mark for a couple of race spec pumps and filters. If the engine is staying around the 350 bhp mark then a second standard pump would do fine as the overall capacity of the two pumps combined is more than needed and gives a big safety margin. I still suggest using a couple of billet filters though.
I also have a digital fuel pressure guage with low pressure alarms that indicate problems. This is is also hooked up into the car's data logging so I can see if a misfire is caused by a fuel pressure variation. Might be paranoid but the costs are peanuts compared to the time and money that has gone into the engine over the years.
Steve & Dw - thanks for your replies..
My thoughts were that the existing pump is probably good for 300 bhp and if it's old and it is then it might even be shy of this..
I have an adjustable regulator - with an gauge that can be fitted (not permanent) - so armed with this I presume that if the 'set' fuel pressure drops at
high revs then this could be an indication that
it does not have enough in reserve.
I'm looking seriously for a bigger pump because as Steve points out - the prospect of running lean at high revs can have bad results..
Guess - I'll know soon when I fit the wide band lambda and digital display..
My thoughts were that the existing pump is probably good for 300 bhp and if it's old and it is then it might even be shy of this..
I have an adjustable regulator - with an gauge that can be fitted (not permanent) - so armed with this I presume that if the 'set' fuel pressure drops at
high revs then this could be an indication that
it does not have enough in reserve.
I'm looking seriously for a bigger pump because as Steve points out - the prospect of running lean at high revs can have bad results..
Guess - I'll know soon when I fit the wide band lambda and digital display..
dwgriffith said:
You need to know the flow at working pressure otherwise it means nothing at all.
I know it will not be exact, but if you took it from the FPR return then you would get flow at running presure. would give you some idea on how your pump was running.but as Steve said not a good idea to be cutting costs in that area.
Steve have you got any pic's or diagrams to how to connect the two pumps into one fuel line, do you need any one-way valves to stop the fuel just going up the other punmp if you are only using one.
Thanks
Leigh
The pumps are simply paralleled up. No need for valves etc. Measuring pressure from the return is pretty meaningless as it does not indicate the actual pressure in the injector rails. The way the regulator works is that the fuel is fed straight to the rails. The pump will try and increase the pressure and this excess pressure will open a valve that diverts some fuel to the retun pipe. This lowers the fuel pressure. This adjustment is continually happenning so that the pumps provide a consistent pressure in the rail. I measure the pressure going into the regulator from the pumps which is the same as the pressure inside the injector rail.
So maybe the best way of measuring flow rate is to run the engine on idle and let the return run into a bucket, and time that. For the amount of fuel to keep the engine ticking over will be fairly negligible (maybe Steve's excepted) so everything that ends up in the bucket is what the pump can flow at the rail pressure.
I would also have thought that timing the flow from the pump into atmospheric would be not entirely pointless, you should see a _healthy_ excess over the engine's requirements, say a factor of two?
It might be prudent for me to check my fuel pressure at full power, min and max, I see another guage coming up....
I would also have thought that timing the flow from the pump into atmospheric would be not entirely pointless, you should see a _healthy_ excess over the engine's requirements, say a factor of two?
It might be prudent for me to check my fuel pressure at full power, min and max, I see another guage coming up....
Edited by adam quantrill on Friday 7th September 10:33
What you could do for a quick fuel pressure test. is to take the oil pressure sender. and connect that to the cold start fuel line, then you can measure the fuel pressure from inside the car.
or get a 2nd sender, and fit a switch to swap. what sender goes to the gauge, then you don't need a 2nd gauge.
or get a 2nd sender, and fit a switch to swap. what sender goes to the gauge, then you don't need a 2nd gauge.
Wouldn't put fuel through a oil pressure sensor unless I know it was designed to do so.
Fuel can perish seals etc and either wreck the sensor or cause leaks.
Fuel pressure guages only cost a few pounds - peanuts in the grand scheme of things. Alright I use a SPA digital unit which was around the £200 mark but to do basic checks etc a mechanical one would be fine and they are not expensive. On my LS1 powered Cerbie I have a regulator with a built in mechanical pressure guage which is ideal for setup and testing. Reg with guage was around the £35 mark.
Fuel can perish seals etc and either wreck the sensor or cause leaks.
Fuel pressure guages only cost a few pounds - peanuts in the grand scheme of things. Alright I use a SPA digital unit which was around the £200 mark but to do basic checks etc a mechanical one would be fine and they are not expensive. On my LS1 powered Cerbie I have a regulator with a built in mechanical pressure guage which is ideal for setup and testing. Reg with guage was around the £35 mark.
Yes I was thinking unleaded would attack the sender and it'd probably spurt out of the back - not good. In any case I dunno what the sender is on a 400SE/X, as the gauge isn't a VDO one.
I've seen mechanical ones on fleabay for between 8 and 15 quid, but then I remembered my mate Jim probably has a nice digital one I can borrow, which might be better because I was wondering how to read the gauge under the bonnet when on full throttle at 4,500 rpm in third.... ;^)
I've seen mechanical ones on fleabay for between 8 and 15 quid, but then I remembered my mate Jim probably has a nice digital one I can borrow, which might be better because I was wondering how to read the gauge under the bonnet when on full throttle at 4,500 rpm in third.... ;^)
A ha that's were you use my method for fuel / oil pressure testing 
Replace the cold start hose with one that's long enough to reach the windscreen / edge of bonnet, attach guage to end of hose and tape down in such a position that you can still see gauge whilst driving
Then drive around at said rev / speed and you can see the needle moving.
This worked very well for my extra capillery oil pressure guage when I was trying to find a low pressure fault that my interior guage was displaying.(bought a cheap TIM guage that had a t piece with it so you could split the oil pressure light and run both the guage and light in the dash)
And was working on the fuel guage, but now no pressure on guage, but maybe duff guage, but still not running
Replace the cold start hose with one that's long enough to reach the windscreen / edge of bonnet, attach guage to end of hose and tape down in such a position that you can still see gauge whilst driving
Then drive around at said rev / speed and you can see the needle moving.
This worked very well for my extra capillery oil pressure guage when I was trying to find a low pressure fault that my interior guage was displaying.(bought a cheap TIM guage that had a t piece with it so you could split the oil pressure light and run both the guage and light in the dash)
And was working on the fuel guage, but now no pressure on guage, but maybe duff guage, but still not running
Yeah I spose the worst thing that's going to happen is that fuel pisses all over the screen, but what the hey!
In the long run I'd probably try and get an electronical sender with a comparator and an audible warning, in case the fuel pump starts to lose it and/or the filter is getting clogged, although the piston crown thing is probably nothing to worry about really. In real life, if I were flooring it enough to eat a piston, I'd have run out of road a few minutes earlier....
In the long run I'd probably try and get an electronical sender with a comparator and an audible warning, in case the fuel pump starts to lose it and/or the filter is getting clogged, although the piston crown thing is probably nothing to worry about really. In real life, if I were flooring it enough to eat a piston, I'd have run out of road a few minutes earlier....
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