Fuel Cavitation (Air in fuel)
Discussion
barriejames said:
Mark
Bad news on the issues you are having. My part of the build is a little way from this and I want to ensure I get it as right as I can first time. It will be interesting to hear how you resolve this, and if it is a heat related issue?
We think it could be filters being blocked and the low pressure pump struggling to keep up as a result. Stripping the system back down will hopefully reveal what is causing the blockage. That said, some heat protection on the sides of the tanks facing the exhaust seems like a sensible thing to do during the build, as well as on the fuel swirl pot if you have one. I'll be adding some heat protection to mine certainly in the most exposed areas. The tanks are duller now than when new so probably absorb more heat...Bad news on the issues you are having. My part of the build is a little way from this and I want to ensure I get it as right as I can first time. It will be interesting to hear how you resolve this, and if it is a heat related issue?
I have been watching this topic since it started, and can't quite figure it out. It must be quite a bit hotter in the UK than it used to be last time I was there.
I built my car pretty much per the factory build instructions except for the fuel selector valve and all the associated wiring, which I threw in the trash. I just plumbed my two tanks together, and use the factory supplied low pressure pump, swirl pot, and high pressure pump and filters.
Driving my car in Las Vegas,Nevada in September with the ambient air temperature around 110F, I have not had a problem with fuel vaporizing or the engine shutting down.
Global warming must be hitting you folks much harder than it is on this side of the pond
I built my car pretty much per the factory build instructions except for the fuel selector valve and all the associated wiring, which I threw in the trash. I just plumbed my two tanks together, and use the factory supplied low pressure pump, swirl pot, and high pressure pump and filters.
Driving my car in Las Vegas,Nevada in September with the ambient air temperature around 110F, I have not had a problem with fuel vaporizing or the engine shutting down.
Global warming must be hitting you folks much harder than it is on this side of the pond
Out of interest Rat. Do you have the return line from the pressure reg fed back to the swirl pot and a line from the swirl pot back to the tanks or do you feed the return directly to the tanks? If the second what is the method of releasing air/vapour from the swirl pot back to the tanks?
Guys I am with Rat on this one. I don't even use a swirl tank, I just dump the return fuel from the regulator back to the opposite tank from which I take the fuel in the first place. I don't even have low pressure pump, my high pressure Aeromotive pump inlet is lower than the tank . therefore positive flow to the pump always. Lots of days over 100F / 38C on the street in traffic at the track NEVER EVER A PROBLEM.
That said: for those of you building your cars now, put the pump in the tank with the filter connect the tanks with a 1 inch line. done
That said: for those of you building your cars now, put the pump in the tank with the filter connect the tanks with a 1 inch line. done
Rat
thats how I do it but I have had massive problems the same as Roj. The solution was to slightly pressurise the swirl pot. What LP pump do you have? I am using the std ones from when my car was carb. Carter I think. If yours pumps loads then you may have slight pressure in the swirl pot. A restriction in the line has been used by some to create pressure I use a reg set at 5 psi.
thats how I do it but I have had massive problems the same as Roj. The solution was to slightly pressurise the swirl pot. What LP pump do you have? I am using the std ones from when my car was carb. Carter I think. If yours pumps loads then you may have slight pressure in the swirl pot. A restriction in the line has been used by some to create pressure I use a reg set at 5 psi.
ROWDYRENAULT said:
......That said: for those of you building your cars now, put the pump in the tank with the filter connect the tanks with a 1 inch line. done.
That's the best advice for new builders.....if I were building again there's two things I would do, this would be the first (although I did connect my tanks by -12 and dumped the complicated and unreliable valve system). I've seen somewhere that someone has welded in one tank a Corvette pump, I think it was called a cassette. I've ended up with a low pressure pump in the passenger tank pumping to a bigger swirl pot with a Walbro Motorsport pump in it, that way my pumps are surrounded by fuel and cooled by fuel (gold wrapped). The other thing would be to dump the Getrag 996 box as it's totally the wrong box to use, G96 turbo (4WD converted to 2WD) the way to go.Rowdy
I am with you now. I am going to connect my 2 lines together(so fuel can come from either tank) with a T with -8 going to pump inlet with pump mounted low on bulkhead. I am also going to use a fuel pressure control system which varies the pump speed to control pressure. Keep tanks reasonably full when on track no problem. No LP pumps 1 fuel gauge even less problems.
I am with you now. I am going to connect my 2 lines together(so fuel can come from either tank) with a T with -8 going to pump inlet with pump mounted low on bulkhead. I am also going to use a fuel pressure control system which varies the pump speed to control pressure. Keep tanks reasonably full when on track no problem. No LP pumps 1 fuel gauge even less problems.
I was going to use this http://www.professional-products.com/secure/upload...
However FAST have brought out a new EFI ECU that has the fuel pressure control built in.
They have built this in response to so many people with big power motors in use on the road having problems.
Important to use the correct type of pump. for instance vane type do not like speed control.
However FAST have brought out a new EFI ECU that has the fuel pressure control built in.
They have built this in response to so many people with big power motors in use on the road having problems.
Important to use the correct type of pump. for instance vane type do not like speed control.
Yes, have found this too.
There are only a few standlone pressure controllers on the market.
Here are two others I found, maybe you already know them.
http://www.madhu.com/content/Main/FuelPumpControll...
http://vaporworx.com/ (look at VaporWorx Fuel System Control)
Not sure until now which one to try.
If possible I want to stay with the GM E38 ECU that came with my LS7.
The pump I use is a screw type pump, should be ok afaik.
There are only a few standlone pressure controllers on the market.
Here are two others I found, maybe you already know them.
http://www.madhu.com/content/Main/FuelPumpControll...
http://vaporworx.com/ (look at VaporWorx Fuel System Control)
Not sure until now which one to try.
If possible I want to stay with the GM E38 ECU that came with my LS7.
The pump I use is a screw type pump, should be ok afaik.
What do people think is the main reason for fuel getting hot?
e.g. does slowing down the circulation of fuel result in less heat build up? Is it due to the surge tank being too high in the engine bay? Heat from exhaust/engine? Or general amounts of heat in the clam that will end up in the fuel regardless?
Mark
e.g. does slowing down the circulation of fuel result in less heat build up? Is it due to the surge tank being too high in the engine bay? Heat from exhaust/engine? Or general amounts of heat in the clam that will end up in the fuel regardless?
Mark
Not an expert by far, but after reading the posts and suggestions posted recently on this subject, I guess you have several factors:
1. Ambient temperature (the higher it is, the greater will be the temp in the tanks)
2. Heat generated by the fuel pumps as the fuel is pumped around
3. Radiant heat from a whole lot of sources in the engine bay (engine, manifolds, oil coolers, A/C condenser, etc.)
3. Little way for the heat to flow out of the rear
Plenty more I expect, but some reflective material on the tanks, reflective material around and close to the manifolds and exhausts seem to do wonders. A way to get cool air flowing around the pumps would be nice too, or getting them immersed into the side tanks. That seems the way to go for a whole lot of vehicle manufacturers, rally and race teams.
1. Ambient temperature (the higher it is, the greater will be the temp in the tanks)
2. Heat generated by the fuel pumps as the fuel is pumped around
3. Radiant heat from a whole lot of sources in the engine bay (engine, manifolds, oil coolers, A/C condenser, etc.)
3. Little way for the heat to flow out of the rear
Plenty more I expect, but some reflective material on the tanks, reflective material around and close to the manifolds and exhausts seem to do wonders. A way to get cool air flowing around the pumps would be nice too, or getting them immersed into the side tanks. That seems the way to go for a whole lot of vehicle manufacturers, rally and race teams.
UltimaCH said:
Not an expert by far, but after reading the posts and suggestions posted recently on this subject, I guess you have several factors:
1. Ambient temperature (the higher it is, the greater will be the temp in the tanks)
2. Heat generated by the fuel pumps as the fuel is pumped around
3. Radiant heat from a whole lot of sources in the engine bay (engine, manifolds, oil coolers, A/C condenser, etc.)
3. Little way for the heat to flow out of the rear
Plenty more I expect, but some reflective material on the tanks, reflective material around and close to the manifolds and exhausts seem to do wonders. A way to get cool air flowing around the pumps would be nice too, or getting them immersed into the side tanks. That seems the way to go for a whole lot of vehicle manufacturers, rally and race teams.
Thanks1. Ambient temperature (the higher it is, the greater will be the temp in the tanks)
2. Heat generated by the fuel pumps as the fuel is pumped around
3. Radiant heat from a whole lot of sources in the engine bay (engine, manifolds, oil coolers, A/C condenser, etc.)
3. Little way for the heat to flow out of the rear
Plenty more I expect, but some reflective material on the tanks, reflective material around and close to the manifolds and exhausts seem to do wonders. A way to get cool air flowing around the pumps would be nice too, or getting them immersed into the side tanks. That seems the way to go for a whole lot of vehicle manufacturers, rally and race teams.
Another novel solution I have had proposed is using the air con to cool the fuels. I gather this has been used in both road and race cars in the past.
I will clean out my filters over the weekend, apply some insulation material to tanks and surge pot and wait for a hot day and long journey.
Mark
Trying to keep the fuel cooler is one way of perhaps solving this problem but you can waste a lot of time and money and make your previously neat under clam area look a right mess without achieving much. Or:
You can stop the problem by increasing the pressure that the HP pump feels at the point of suction. The best way is to use an in tank type of pump which has no inlet piping and hence no pressure loss caused by pipework at the point of suction.
Depending on how you use the car you can either put this pump through one of the fuel gauge ports and feed it directly to your pressure reg or you can do it the way that the guys whose company name resembles that of a v fast v strong tv personality from a while ago which is to keep the LP pumps and pipework and fit an in tank pump into a swirl pot and get the benefits thereof as well as no pump cavitation.
You can stop the problem by increasing the pressure that the HP pump feels at the point of suction. The best way is to use an in tank type of pump which has no inlet piping and hence no pressure loss caused by pipework at the point of suction.
Depending on how you use the car you can either put this pump through one of the fuel gauge ports and feed it directly to your pressure reg or you can do it the way that the guys whose company name resembles that of a v fast v strong tv personality from a while ago which is to keep the LP pumps and pipework and fit an in tank pump into a swirl pot and get the benefits thereof as well as no pump cavitation.
Very pleased to report that after cleaning out the 100 micron filter, replacing the element in the 10 micron filter (probably not necessary) and applying heat cloth to the inside edges of both tanks and the fuel swirl pot, that my issue appears to be resolved.
Given a pretty thorough test over the weekend where it sat in M25 traffic for quite some time, drove 2 hours or so on the motorway at cruising speed, then spent the day on track at Silverstone! And drove back afterwards.
Car behaved impeccably the whole time!
Given a pretty thorough test over the weekend where it sat in M25 traffic for quite some time, drove 2 hours or so on the motorway at cruising speed, then spent the day on track at Silverstone! And drove back afterwards.
Car behaved impeccably the whole time!
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