006
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Posts posted by 006
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Any single or combination of factors arising from restricted fuel flow, high ambient temperature and/or low fuel level can create problems as the volatile compounds start to boil .
true.
In any event, air that comes out of solution for pressure/temperature reasons will return to its previous dissolved state rather than permanently hang around as air bubbles in fuel lines.
not quite true,but nearly there. all depends on speed of pump,volume of pump,and return volumes from PRV,and MU. and if system is running. it soon comes out when all things are not working.
If air content in fuel was as significant as you suggest, the PI system wouldn’t work most of the time.
Also not quite true, as alot of PI cars always have had, seem to have air in the injectors. this is as said by some on here.
As well as above observations / findings, another problem arises due to the use of a 26 pump unit.
these pumps deliver alot more fuel than what is required. Alot of the fuel goes through the pumps reduced outlet sized one way valve, causing fuel to be a pure froth. it then goes to the PRV and then out of the valve to the tank, full of dissolved air, its literally shimmering with them, then there is the fuel that is coming back from the MU, this can with the 26 pump, be more that what goes to the MU with one of the smaller pumps.
this fuel is also frothed up alot too. which makes its way to the tank, adding to what was already put there by the PRV valve.
if tank is lowish,then this gets sucked into th pump,so pump does not work as well. as its compressing air as well as fuel out of the end. this is why some times it just screams .
also a combination of to hot a fue,l evaporating and bubbles in fuel.
this is the need for filters,to allow the bubbles to re saturate into the fuel,or come out of it in big bubbles.
which can be clearly seen,when using clear filters,or looking into tank, as every now and then a big bubble will appear, which has come from the filtered returns.
one really has to look into a tank,with a flash light to light up all the fothed up fuel, when engine has been running for a while to see just what state the fuel is in there.
the fuel in the tank is literally all frothed up when the pump /prv/ MU returns are feeding it.
the smaller pumps dont create the same problems as the bigger pump,thats why they maybe seem to work ok on standard engines,but they will and do not produce much hp, on a modded engine, as they cannot suply enough fuel ,at the pressure they set at, to run the MU and to open the injectors,which need to have their spring pressures over come, before any fuel will flow.
if the pressure is set higher, then the Bosch small pumps over heat due to cavitation and fuel getting hot.
this is main reason why small pumps,or Lucas pumps worn out / not up to it cannot give good HP
as the fuel is just not getting into the engine. this is seen by no fuel returning from MU return,or by pulling excess fuel lever out,and seeing no diff in CO ,or HP readings, as there just is not the fuel there to make difference.
you may get a short duration burst,but not a sustained fuel delivery.
with a 26 pump even on full power/revs there is a really good return flow back to tank,or pull the excess lever out at full power,and it will flood the engine with fuel.
Smaller pumps will,and do give very good power,but not with Lucas injection,but electronic injectors,which dont rely on fuel pressure to open them.or also loosing pressure in the MU itself.
Also electronic injectors work at alot less prssure at anything from 30 to 45 psi dependant on type /usage
one has to realise that the mechanical bosch / kuglefischer injection works on alot lower PSI than the Lucas system does.
so a pump used as standard for one of those cars will not work as good on a Lucas set up. which is what is being sold by most after market set ups. and unless you get the correct pump it will not perform as good as it should.
R
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Well 006 pleased that you agree with the returning fuel point but to get air in the system it must come via a leak in the pipe work/fittings . Those who's se tup works well don't suffer from this.
ROY
As Roy said 006 if you have air, you put it in,incorrect plumbing or tank. I do not know if any of you had a chance to to look at the late Mike Bingley's car for sale at Malvern a few years back , if so you would have learned a lot
why cant some folk just accept that air in fuel lines comes from the fuel.
good lord,its not rocket science
look at this, and then tell me, and others where you think the air bubbles are coming from.
a little pointer in the right direction, its not coming from the plumbing system, and I did not, nor did the owners put the air in there.
Nylen, your pump is most likely not up to the job of running 105 psi continuously,as it is most likely one designed to run at 60-70 PSI continuously
R
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I seem to recall on my set up, there always being air in it , as if the pump was moving the fuel faster than it could refill.
You said JR
This is what I trying to say , its the pump and filters putting air in to system
Early 5,s had the return inot the filter, caused nothing but problems.
also the idea of putting the PRV return into the swirl,is also a bad idea.
the stuff that comes from the PRV is just pure froth. this will soon make the pump sing.
when you look into a tank, and its low on fuel, the contents are shimmering with bubbles,
these bubbles get into feed and cause loss of power, and low down hiccups.
Also why alot of injectors are always full of air.
really need a bigger inlet feed,whether bosch or Lucas, and need a pre filter,and after filter, with both too.
and I also put one in the returns from the Injectors / MU and the PRV valve
reason, air in suspension in the petrol can,and dose go from a froth to a couple of big bubbles, which if you got a clear filter, can be seen.
And if you can, take out the non return valve in the end of the pump, that is resposible for alot of frothed petrol.
If you really want a good demonstration, easy to do too. If your taps are the combined type, or fed of a combi system, and are the small bore pipe fed taps, [not the 13 / 22 mm type ] then go and turn your tap on, either hot or cold and have a look at the water that goes into the glass, its not clear,its full of air,thats why its white / opaque
and watch it in the glass, the water slowly becomes clear as the bubbles dissolve
this is what goes on in your system on the car.
this is why you get air in your injectors. and why they wont work right all the time.
Rev tuned,!!! Nah.
selling pumps , that are not good enough for Lucas injection
filters, and not enough filters in the system as well that really are not up to the job of ridding system of air from the fuel
Pumps ok for EFI and low powered 5/6s, but no good for Lucas injection needing alot of fuel pressure to make the MU / injectors work right. at high revs for sustained time.
R
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Really cant be arsed to respond to this..
you stick with lots of show and not much go then
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8 mm will be ok for standard low HP engines, but will not only starve the engine of fuel at top end, high revs/high load.
but will also cause pump to cavitate, as its sucking fuel too fast thru too small a pipe.
which leads to bubbles forming in the fuel, which then leads to even less flow.
that why you need a pree filter, and also an after filter, these stop the minute frothed up fuel going down the line, into the pump first,
the the pump its elf makes bubbles, so these then go into after filter, and dissapear thru the filter material, and come out as good fuel.
not the frothed up stuff that most of you lot with inadequate supply / filters will be getting.
Any one of you actually had a look at the stuff coming direct from the pump, its not a pretty sight.
then put it into a big filter, and then see what comes out, much better.
I honestly think this is why folk dont get the HP they think they have got, because the fuel is full of air.
how many folk keep saying, my injectors are playing up, got air in them,
where the air come from,!!!!!!
some one said , look at the German cars set up, a good bit of advice .
You really need a big outlet / feed if you wanting good HP,
R
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ditch the cam, youve put in a cam that was not designed for that engine,
lousey tick over, poor fuel consumption. noisey
it will soon need changing any way. followers wearing out soon. cam lobes following.
you can get more hp out of a late type cam than most of the after market cams upto 280 degrees
with no massive great big hole in the T curve as well.
and alot better fuel consumtion too. better idle quieter
then spend some time, getting the fueling and ign right on a RR,
whose operator knows what he doing.
Racing Swallow Doretti
in General TR Technical
Posted
Wot yer classing as ..racing, !!
Alan Gibbs Swallow Dorretti has taken part in a few Hillclimbs last few yers
here he is at one, and there a few others just further down
https://www.google.com/search?q=Alan+Gibbs+Swallow+Doretti&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjB5Yu7m-DkAhWSasAKHWuIBp4Q_AUIESgB&biw=1698&bih=1029#imgrc=OFHWpD8WWjmK2M: