Discussion
Surely it will be running an extremely non optimum ignition angle as the std ecu presumably doesn't have a MAP sensor that can read positive manifold pressures? So whilst the MAF and closed loop controller will add extra fuel, there is no mechanism to correct the ignition timing is there? (or do people rely on the knock control to prevent damage, and just run with non optimised ignition outside of BLD areas)
seeing as this is the only place interested in IVA's and if i eventually have to have one - what is the consensus on using a mustang fuel tank which forms part of the boot floor?
considering the IVA stuff says this...
11. A Fuel Tank must not be located in, or form part of the passenger
compartment, or other compartment integral with it and the bulkhead that
separate the passengers from the fuel tank must be free from holes
through which any escaped fuel could travel.
and the top of the mustang fuel tank is built to be the boot floor of a mustang
are they incompatible?
note: I wont be filling it up from the standard mustang spot through the bootlid but will block the hole and put a new pipe in the side for regular filling from the fuel flap
If this is not compatible then I would seriously appreciate any input from anyone that can identify an "off the shelf" fuel tank that will fit under the car or in this space that is available in the boot behind the subframe.
bare in mind im not willing to have a fuel cell sat in the boot as the whole car needs to stay as standard as possible on the inside, and i don't particularly want to make my own fuel tank. its something ive managed so far and its only really the fuel tank that is getting in my way now
im sure the hive mind can come up with a random car that has a fuel tank that will fit in the hole at some point
considering the IVA stuff says this...
11. A Fuel Tank must not be located in, or form part of the passenger
compartment, or other compartment integral with it and the bulkhead that
separate the passengers from the fuel tank must be free from holes
through which any escaped fuel could travel.
and the top of the mustang fuel tank is built to be the boot floor of a mustang
are they incompatible?
note: I wont be filling it up from the standard mustang spot through the bootlid but will block the hole and put a new pipe in the side for regular filling from the fuel flap
If this is not compatible then I would seriously appreciate any input from anyone that can identify an "off the shelf" fuel tank that will fit under the car or in this space that is available in the boot behind the subframe.
bare in mind im not willing to have a fuel cell sat in the boot as the whole car needs to stay as standard as possible on the inside, and i don't particularly want to make my own fuel tank. its something ive managed so far and its only really the fuel tank that is getting in my way now
im sure the hive mind can come up with a random car that has a fuel tank that will fit in the hole at some point
Generally i don't like to have a fuel tank outside of the wheelbase of the car, wherever possible.
Now in certain circumstances, such as yours, there simply may not be any other viable or practicable alternative, especially if you cannot stretch to the cost of a custom bag tank or similar.
The IVA rules (sensibly) require a separate, sealed, non-flammable, non-porous bulkhead between the cabin and the fuel tank. ie the tank itself, even if made of metal, cannot be used as part of, or all of, that bulkhead. Realistically, this means that you will need to construct a metallic bulkhead/floor to "cover" any fuel tank you fit below that bulkhead/floor. This isn't actually very hard to do, with some basic sheet metal work and you clearly have the fabrication / welding skills to do that.
What i would say is that looking at the layout of your car, the "Boot" zone of a typical production fwd car is in fact part of the crumple zone, ie it is expressly designed with low longitudinal stiffness to crumple if hit. In fact, often the spare wheel well and the spare wheel in it can also play a part in achieving that controlled deformation during a significant accident. The zone where the rear suspension starts is typically maintained as the start of the "stiff, non intrusion" cabin zone, because this typically coincides with the backsides of any rear seat passengers. Here, you have a problem, because in a rear impact, the rear bumper, rear cross bar (under the bumper skin) and slam panel behind it are very likely to be pushed forwards and towards in your case, a very solidly mounted and very stiff rear subframe containing a very large solid rear diff. Anything in that zone represents a crush hazard, and that includes any tank mounted there.....
You options probably are:
Safest: Install a "hump over" tank in the remaining space in front of the rear seats. This is very likely to require the complete loss of the rear seat footwells, or otherwise a very small fuel tank that makes the car a PITA to use practically. The "Hump over" tank is needed because you have to pass a prop shaft right though the middle of it, a tank from something like a BMW 1 series is probably what you are after here. This could end up effectively negating the use of the rear seats (due to lo leg room) but is likely to be the safest option, and means you can use a cheap, second hand plastic OEM fuel tank
More Hazardous: Install a broadly rectilinear tank (ideally plastic if you can find a suitable sized OE one, or afford to buy a motorsport plastic tank ie https://www.cactusnav.com/plastic-fuel-tank-high-p... ), ABOVE the original rear boot floor line, but behind the rear subframe, then cover with a secondary metallic bulkhead (could be a lightweight aluminium panel, sealed over the top with suitable fuel proof semi-adhesive sealant (sikaflex etc). In this case, the tank mountings should deliberately allow the tank a limited movement forwards should a significant rear impact occur, and the tank will be pushed up and forwards, and not get squashed in the gap 'twixt rear subframe and rear slam panel. The advantage of this approach is that your rear seats can probably remain as standard, and your boot will be still mostly available for use.
Compromise: Fit a custom tank into a semi -recessed space partially below the rear boot floor line. Design that sheet metal partial recess to include a sloping lead out to the higher floor zone above the rear subframe. Fit additional longitudinal load carrying members (box section steel) into the sides of that recessed zone to prevent / reduce crumpling in that tank well. Mount tank with straps that allow the tank to slide forwards, up the ramp, and up over the rear subframe should i get impacted by a collapse of the zone behind the tank. Ideally, try to leave 50 to 100mm of std chassis rails and cushable boot floor between the rear of the tank well and the standard rear slam panel, to absorb some energy in the event of a rear impact. That tank will have to be covered by a suitable metalic fabricated cover (ally panel) and that should be fixed in a way as to yield and if necessary let the tank slide up and through it (pop rivets are ideal here, as they can simply be allowed to pull through the thin ally panel as the tank punches up and away.
In all cases, i really would try to avoid having to use a metallic tank, simply because plastic tanks are so much more forgiving. I guess you really need a miniumum of around 45 litres (10 gallons) to give the car sensible range, If you can't stretch to a pukka motorsport plastic tank, then iirc, the land rover discovery 2 and later Landrover 110 had a broadly rectangular tank that is tough and cheap, and might be worth a google (think it might be too big, 95l rings a bell??)
Now in certain circumstances, such as yours, there simply may not be any other viable or practicable alternative, especially if you cannot stretch to the cost of a custom bag tank or similar.
The IVA rules (sensibly) require a separate, sealed, non-flammable, non-porous bulkhead between the cabin and the fuel tank. ie the tank itself, even if made of metal, cannot be used as part of, or all of, that bulkhead. Realistically, this means that you will need to construct a metallic bulkhead/floor to "cover" any fuel tank you fit below that bulkhead/floor. This isn't actually very hard to do, with some basic sheet metal work and you clearly have the fabrication / welding skills to do that.
What i would say is that looking at the layout of your car, the "Boot" zone of a typical production fwd car is in fact part of the crumple zone, ie it is expressly designed with low longitudinal stiffness to crumple if hit. In fact, often the spare wheel well and the spare wheel in it can also play a part in achieving that controlled deformation during a significant accident. The zone where the rear suspension starts is typically maintained as the start of the "stiff, non intrusion" cabin zone, because this typically coincides with the backsides of any rear seat passengers. Here, you have a problem, because in a rear impact, the rear bumper, rear cross bar (under the bumper skin) and slam panel behind it are very likely to be pushed forwards and towards in your case, a very solidly mounted and very stiff rear subframe containing a very large solid rear diff. Anything in that zone represents a crush hazard, and that includes any tank mounted there.....
You options probably are:
Safest: Install a "hump over" tank in the remaining space in front of the rear seats. This is very likely to require the complete loss of the rear seat footwells, or otherwise a very small fuel tank that makes the car a PITA to use practically. The "Hump over" tank is needed because you have to pass a prop shaft right though the middle of it, a tank from something like a BMW 1 series is probably what you are after here. This could end up effectively negating the use of the rear seats (due to lo leg room) but is likely to be the safest option, and means you can use a cheap, second hand plastic OEM fuel tank
More Hazardous: Install a broadly rectilinear tank (ideally plastic if you can find a suitable sized OE one, or afford to buy a motorsport plastic tank ie https://www.cactusnav.com/plastic-fuel-tank-high-p... ), ABOVE the original rear boot floor line, but behind the rear subframe, then cover with a secondary metallic bulkhead (could be a lightweight aluminium panel, sealed over the top with suitable fuel proof semi-adhesive sealant (sikaflex etc). In this case, the tank mountings should deliberately allow the tank a limited movement forwards should a significant rear impact occur, and the tank will be pushed up and forwards, and not get squashed in the gap 'twixt rear subframe and rear slam panel. The advantage of this approach is that your rear seats can probably remain as standard, and your boot will be still mostly available for use.
Compromise: Fit a custom tank into a semi -recessed space partially below the rear boot floor line. Design that sheet metal partial recess to include a sloping lead out to the higher floor zone above the rear subframe. Fit additional longitudinal load carrying members (box section steel) into the sides of that recessed zone to prevent / reduce crumpling in that tank well. Mount tank with straps that allow the tank to slide forwards, up the ramp, and up over the rear subframe should i get impacted by a collapse of the zone behind the tank. Ideally, try to leave 50 to 100mm of std chassis rails and cushable boot floor between the rear of the tank well and the standard rear slam panel, to absorb some energy in the event of a rear impact. That tank will have to be covered by a suitable metalic fabricated cover (ally panel) and that should be fixed in a way as to yield and if necessary let the tank slide up and through it (pop rivets are ideal here, as they can simply be allowed to pull through the thin ally panel as the tank punches up and away.
In all cases, i really would try to avoid having to use a metallic tank, simply because plastic tanks are so much more forgiving. I guess you really need a miniumum of around 45 litres (10 gallons) to give the car sensible range, If you can't stretch to a pukka motorsport plastic tank, then iirc, the land rover discovery 2 and later Landrover 110 had a broadly rectangular tank that is tough and cheap, and might be worth a google (think it might be too big, 95l rings a bell??)
Hump over BMW tank for reference:
https://www.ebay.co.uk/itm/2011-BMW-1-SERIES-Petro...
actually quite small, so may package in front of rear subframe with some mods to rear foot wells?
https://www.ebay.co.uk/itm/2011-BMW-1-SERIES-Petro...
actually quite small, so may package in front of rear subframe with some mods to rear foot wells?
Hump over tank won’t work they’re all too big. The only one that may work is one of the brz cousins but try finding tank dimensions anywhere. Almost impossible.
I also only have ~10cm between the car and propshaft under the seat
Total width is only 85cm between chassis rails and 40cm between diff and back seat footwell.
I’m almost certainly ruling out hump tanks because of space. What I haven’t ruled out yet is 2 separate tanks either side of the prop but that’s difficult and double the expense. I’m not cutting into the rear footwell as there’s a structural member there and I’ve had enough of working with the complex bits.
That leaves the rear as my only other option. I’m happy to make a false floor at boot level height, that was the plan with the mustang tank anyway if you consider the tank to be the floor. That leaves 2 “rectangles” of space that can realistically be filled with fuel tank.
Those rectangles are 80x65x10 which would sit above the subframe and 55x40x25 which would sit behind the subframe
I also only have ~10cm between the car and propshaft under the seat
Total width is only 85cm between chassis rails and 40cm between diff and back seat footwell.
I’m almost certainly ruling out hump tanks because of space. What I haven’t ruled out yet is 2 separate tanks either side of the prop but that’s difficult and double the expense. I’m not cutting into the rear footwell as there’s a structural member there and I’ve had enough of working with the complex bits.
That leaves the rear as my only other option. I’m happy to make a false floor at boot level height, that was the plan with the mustang tank anyway if you consider the tank to be the floor. That leaves 2 “rectangles” of space that can realistically be filled with fuel tank.
Those rectangles are 80x65x10 which would sit above the subframe and 55x40x25 which would sit behind the subframe
Jaffman said:
Hump over tank won’t work they’re all too big. The only one that may work is one of the brz cousins but try finding tank dimensions anywhere. Almost impossible.
I also only have ~10cm between the car and propshaft under the seat
Total width is only 85cm between chassis rails and 40cm between diff and back seat footwell.
I’m almost certainly ruling out hump tanks because of space. What I haven’t ruled out yet is 2 separate tanks either side of the prop but that’s difficult and double the expense. I’m not cutting into the rear footwell as there’s a structural member there and I’ve had enough of working with the complex bits.
That leaves the rear as my only other option. I’m happy to make a false floor at boot level height, that was the plan with the mustang tank anyway if you consider the tank to be the floor. That leaves 2 “rectangles” of space that can realistically be filled with fuel tank.
Those rectangles are 80x65x10 which would sit above the subframe and 55x40x25 which would sit behind the subframe
ok cool, that rules out some of the more complex options!I also only have ~10cm between the car and propshaft under the seat
Total width is only 85cm between chassis rails and 40cm between diff and back seat footwell.
I’m almost certainly ruling out hump tanks because of space. What I haven’t ruled out yet is 2 separate tanks either side of the prop but that’s difficult and double the expense. I’m not cutting into the rear footwell as there’s a structural member there and I’ve had enough of working with the complex bits.
That leaves the rear as my only other option. I’m happy to make a false floor at boot level height, that was the plan with the mustang tank anyway if you consider the tank to be the floor. That leaves 2 “rectangles” of space that can realistically be filled with fuel tank.
Those rectangles are 80x65x10 which would sit above the subframe and 55x40x25 which would sit behind the subframe
So if you are going to use the space to the immediate rear of the subframe, the space the old spare wheel well used to occupy, it's simply a matter of finding a rectangular tank that will fit, and ensuring that space cannot become compromised in a rear impact. A basic square tube steel frame could be used to both support the tank, and to provide longitudinal anti-crush strength and also to provide a conveniently level and square base over which you can install a thin steel or alluminium cover plate to seal the tank from the cabin.
Off the shelf "Motorsport" plastic tanks are not that expensive, and would simplify the fuel system layout, and being rectangular, would make that frame and packaging significantly easier. Most of those tanks have a filler neck that is upwards facing, that may eat into the boot space and make connecting the filler neck more difficult. I've been trying to google plastic tanks with end/side on filler necks, but it's difficult to find such a unit!
I can't remember on the C170 unibody how the rear bumper bar attaches to the rear slam panel? It may be possible to bring forwards those mounting points and use them as the basis for you additional longitudunal stiffeners etc?
I think a mid 2000s Fiat Panda plastic tank might fit in the cavity between your rear suspension and the rear bumper.
I agree with Max that it's not great having your fuel tank in the crumple zone, if you can't avoid it, particularly when a small rwd Ford hatchback represents the most famous case of that going very badly!
Though there's a lot of cars running around with LPG tanks in the spare wheel well etc that are probably similarly at risk of being damaged in an impact, even if they are quite a bit tougher than a normal fuel tank.
I agree with Max that it's not great having your fuel tank in the crumple zone, if you can't avoid it, particularly when a small rwd Ford hatchback represents the most famous case of that going very badly!
Though there's a lot of cars running around with LPG tanks in the spare wheel well etc that are probably similarly at risk of being damaged in an impact, even if they are quite a bit tougher than a normal fuel tank.
A couple of small, broadly rectangular OE tanks that might fit are, from some googling, those from the Ford KA, and Mx5. Both are metal tanks, but of OE quality obviously. I'd prefer a plastic OE tank, but i'd accept an OE metal one if it can be suitably mounted and supported.
KA tank:
MX-5 tank
KA tank:
MX-5 tank
Jaffman said:
I have access to a KA that is dead... lol
35 litres though - that’s a bitter pill.
I also recon a rectangular one isn’t the answer, I need a rectangular topped one with a sort of sump off to the side
year, 35 litres at 15 mpg means lots of fuel station visits ;-) That may have to be one of the compromises of the build i guess? My car, that was build as a single venue rally car has just 20 litres fuel capacity, because that small size enabled the tank to sit inside the wheelbase. You can pretty much watch the gauge fall as you floor it....... However, my car is in no way any kind of practical for road use.35 litres though - that’s a bitter pill.
I also recon a rectangular one isn’t the answer, I need a rectangular topped one with a sort of sump off to the side
One problem with "flat" style tanks is that it can cause fuel pick up issues when the fuel level drops below about half way, due to excessive "slosh". Obviously if you are building a tank from scratch, then internal baffling /trap doors, and suitable pickups can be used to try to keep a pool of useable fuel around the pickup to avoid sucking air. People also use an additional external surge tank, but that needs mounting and plumbing etc, so adds complication and leak risks etc
You may be able to modify a flat style tank to include a low "sump" area, welded to the steel tank to help this issue?
I basically have this much room to play with.
not convinced im going to find anything tbh
just another hurdle in the race to see if this will actually work or not
custom aluminium tank wont pass IVA even though i could conceivably make one, i have the abilities and machinery.
modified steel fuel tank wont pass IVA even though this is something i could do much easier
standard steel fuel tank is an option if i can find one that fits, but i suggest the compromises i'm making in the size wont allow it to be a reasonable road worthy car
standard plastic tank is my best bet but finding one in the right size and shape is likely impossible.
also id like to point out that i've been searching for a fuel tank for about 2 years now so its not through lack of trying.
not convinced im going to find anything tbh
just another hurdle in the race to see if this will actually work or not
custom aluminium tank wont pass IVA even though i could conceivably make one, i have the abilities and machinery.
modified steel fuel tank wont pass IVA even though this is something i could do much easier
standard steel fuel tank is an option if i can find one that fits, but i suggest the compromises i'm making in the size wont allow it to be a reasonable road worthy car
standard plastic tank is my best bet but finding one in the right size and shape is likely impossible.
also id like to point out that i've been searching for a fuel tank for about 2 years now so its not through lack of trying.
Why won't a custom or modified steel/aluminium tank pass IVA?
A plastic fuel tank, or a tank for LPG, has to be unmodified and documented as suitable, but a normal petrol/diesel tank should just need to not leak, and meet the other requirements for location, fitting, and earthing etc.
I don't recall anything saying they can't be DIY.
A plastic fuel tank, or a tank for LPG, has to be unmodified and documented as suitable, but a normal petrol/diesel tank should just need to not leak, and meet the other requirements for location, fitting, and earthing etc.
I don't recall anything saying they can't be DIY.
InitialDave said:
Why won't a custom or modified steel/aluminium tank pass IVA?
A plastic fuel tank, or a tank for LPG, has to be unmodified and documented as suitable, but a normal petrol/diesel tank should just need to not leak, and meet the other requirements for location, fitting, and earthing etc.
I don't recall anything saying they can't be DIY.
Perhaps I misread then. Or assumed that any fuel tank has to have documentation claiming it being fit for automotive application. A plastic fuel tank, or a tank for LPG, has to be unmodified and documented as suitable, but a normal petrol/diesel tank should just need to not leak, and meet the other requirements for location, fitting, and earthing etc.
I don't recall anything saying they can't be DIY.
If I’m making my own it’s not going to have any cert, and if I modify one it’s going to be fairly clear it’s been modified.
Pulled up the IVA manual and had a look.
Under fuel tanks, section 03A, they have sections for "gaseous fuels" (i.e. LPG), plastic petrol tanks, and hydrogen tanks, in addition to "normal" tanks under "Fuel Tanks for Liquid fuels at Ambient Temperature".
Can't see anything saying the latter must be documented as being suitable/OEM, or that they can't be modified/fabricated from scratch.
Under fuel tanks, section 03A, they have sections for "gaseous fuels" (i.e. LPG), plastic petrol tanks, and hydrogen tanks, in addition to "normal" tanks under "Fuel Tanks for Liquid fuels at Ambient Temperature".
Can't see anything saying the latter must be documented as being suitable/OEM, or that they can't be modified/fabricated from scratch.
IVA Manual said:
Fuel Tanks for Gaseous Fuels
1.The vehicle as presented must be accompanied by satisfactory documentary evidence with the required standard for fuel tanks for gaseous fuels (See Note 1)
Plastic Fuel Tanks
2.The vehicle must be accompanied by satisfactory evidence that the tank is designed for road use or the tank is an original fitment to a mass produced vehicle, or has been previously and is un-modified. (See Note 2).
Fuel Tanks for Liquid fuels at Ambient Temperature
3.A Fuel tank and associated equipment must not leak.
4.All fuel related components must be securely mounted.
5.All metal fuel tanks must have an earth path to prevent the build up of static electricity. (this may be a separate bonding or the mounting arrangement where it does not isolate the tank)
6.A Fuel Tank must be constructed to withstand the environment, forces and vibration it is likely to be subjected to during normal use.
7.A Fuel Tank must not be fouled by moving parts of the vehicle, or mounted so that it is likely to be subject to abrasion by adjacent parts.
8.Fuel Tanks must not be positioned near a heat source(similar in installation to that of a type approved vehicle), so that a leak could cause a fire hazard.
9.Fuel Tanks must be positioned so as not tobe vulnerable to damage from protruding parts or sharp edges in the event of a front or rear impact.
10.The fuel tank must be positioned so that in the event of a leak the fuel could not accumulate or find a path to the passenger compartment. (if fitted ina compartment there must be a drain which does not exit onto a heat source)
11.A Fuel Tank must not be located in, or form part of the passenger compartment, or other compartment integral with it and the bulkhead that separate the passengers from the fuel tank must be free from holes through which any escaped fuel could travel.
12.The fuel tank must be fitted with a vent (to permit release of a pressure build up) which does not exit on to the exhaust or into the vehicle or be situated at such a height that fuel would be likely to leak when the vehicle is driven.
13.Any fuel filler neck or vent must not allow spilt fuel to be able to fall onto the exhaust system.
14.Fuel tank filling points must not be located in the passenger compartment, luggage compartment or within an engine compartment.
15.A fuel filler cap must positively locate to the filler neck and incorporate an adequate sealing arrangement so that a fuel leak is not possible.
16.The fuel filler cap must either be tethered to the vehicle or be of a lockable type where the key can only be removed when the cap is locked or an automatically opening and closing, non-removable fuel filler cap (Post 0 5 / 2009 vehicles only)
1.The vehicle as presented must be accompanied by satisfactory documentary evidence with the required standard for fuel tanks for gaseous fuels (See Note 1)
Plastic Fuel Tanks
2.The vehicle must be accompanied by satisfactory evidence that the tank is designed for road use or the tank is an original fitment to a mass produced vehicle, or has been previously and is un-modified. (See Note 2).
Fuel Tanks for Liquid fuels at Ambient Temperature
3.A Fuel tank and associated equipment must not leak.
4.All fuel related components must be securely mounted.
5.All metal fuel tanks must have an earth path to prevent the build up of static electricity. (this may be a separate bonding or the mounting arrangement where it does not isolate the tank)
6.A Fuel Tank must be constructed to withstand the environment, forces and vibration it is likely to be subjected to during normal use.
7.A Fuel Tank must not be fouled by moving parts of the vehicle, or mounted so that it is likely to be subject to abrasion by adjacent parts.
8.Fuel Tanks must not be positioned near a heat source(similar in installation to that of a type approved vehicle), so that a leak could cause a fire hazard.
9.Fuel Tanks must be positioned so as not tobe vulnerable to damage from protruding parts or sharp edges in the event of a front or rear impact.
10.The fuel tank must be positioned so that in the event of a leak the fuel could not accumulate or find a path to the passenger compartment. (if fitted ina compartment there must be a drain which does not exit onto a heat source)
11.A Fuel Tank must not be located in, or form part of the passenger compartment, or other compartment integral with it and the bulkhead that separate the passengers from the fuel tank must be free from holes through which any escaped fuel could travel.
12.The fuel tank must be fitted with a vent (to permit release of a pressure build up) which does not exit on to the exhaust or into the vehicle or be situated at such a height that fuel would be likely to leak when the vehicle is driven.
13.Any fuel filler neck or vent must not allow spilt fuel to be able to fall onto the exhaust system.
14.Fuel tank filling points must not be located in the passenger compartment, luggage compartment or within an engine compartment.
15.A fuel filler cap must positively locate to the filler neck and incorporate an adequate sealing arrangement so that a fuel leak is not possible.
16.The fuel filler cap must either be tethered to the vehicle or be of a lockable type where the key can only be removed when the cap is locked or an automatically opening and closing, non-removable fuel filler cap (Post 0 5 / 2009 vehicles only)
Jaffman said:
Perhaps I misread then. Or assumed that any fuel tank has to have documentation claiming it being fit for automotive application.
If I’m making my own it’s not going to have any cert, and if I modify one it’s going to be fairly clear it’s been modified.
AUIU that is only for plastic tanks.If I’m making my own it’s not going to have any cert, and if I modify one it’s going to be fairly clear it’s been modified.
Otherwise I'm screwed!
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