Rob55
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| posted on 13/1/13 at 12:03 PM |
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Fuel System 101
Hi guys, just preparing to build my fuel system for my fuel injected 929cc blade engine, was hoping to get some opinions on the following. First time
build so go easy on me if any of these seem blindingly obvious.....
1. Tank Capacity - what is the norm here? I was thinking around 30L as my car will see a few road miles too. Or would this be considered
unnecessarily large?
2. Fuel Pressure Regulator - do I need one?
3. Fuel Pump - in tank or external? High pressure? How does my engine tell the fuel pump how much fuel to deliver?
4. Surge - I have seen various options including baffles, sumps, swirl pots both in-tank and external. If the tank itself has sufficient baffling,
will this negate the need to run an external swirl pot?
5. Filter - where is the normal position to mount an in-line filter? I was thinking at the engine end on the flexible pipe between the engine and the
hardpipes running back down the car.
6. Flexible Hoses - I assume it is worth spending the extra dollars on braided/aeroquip?
7. Vent System - just a simple screw in valve and a 6mm pipe to a catch tank. Job done?
That's all I can think of for now!! 
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blakep82
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| posted on 13/1/13 at 01:12 PM |
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Imo...
1, 30 will be fine, might seem a bit small for long road runs, but fine for track. Production cars usually seem to be about 60litre
2, yes, definitely
3, much the same, internal keeps everything as one package, and neatly packed away, external needs somewhere to be fitted, how does the engine
know?fuel pressure regulator
4, I have baffles in my tank, but the outlet was at the same level as the bottom of the tank. Swirl pot would sort that, I went for a 2 inch deep
sump, 4inch diameter, with a 2inch hole in the tank so fuel gets in, but not back out
5, ive got 2, each end of the fuel line. The one out the tank protects the pump (external pump) and one at the engine to protect the carbs in my
case
6, no, not really. The iva man wont be able to see any approval markings, and you wont see if they start to crack over the years.
7, so many ways, has to be done, but ive not actually seen a pic of how anyones done it. No catch tank needed though
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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coyoteboy
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| posted on 13/1/13 at 01:35 PM |
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1. Don't know, depends on your car, your space and your use - others may know!
2. Yes, vital.
3. Internal or external, doesn't matter providing you know how to mount it. Needs to be capable of 3 bar (high pressure).Engine doesn't
tell the fuel pump anything, the pump and regulator work autonomously, the injectors are what controls fuel flow.
4. No need for extras if you have sufficient baffling IMO.
5. There's options. Personally I'd put the filter pre-pump and not worry about after pump, obviously this needs to be an external pump for
this. Internal pumps need inline high pressure filters.
6. I would, but there's no need so long as the fuel lines are the required grade for IVA if you're going to IVA it.
7. Could do, there's some nice 1 way valves available that won't let fuel out but will let air in to the tank, they're about £40 but
I prefer that solution as it doesn't mean carrying another tank and it doesn't spill if inverted!
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Rob55
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| posted on 14/1/13 at 07:39 PM |
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Ok great, thanks for clarifying those few points! 
Does the FPR need setting up or anything? How do it and the pump work autonomously?
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Proby
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| posted on 14/1/13 at 10:03 PM |
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Have you not got the original Honda fuel regulator? It's all quite simple, the fuel pump pushes the fuel down to the fuel rail constantly,
the fuel regulator bleeds off Fuel back to tank 'regulating' the stable pressure on the fuel rail.
Visit GraphicMonster
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coyoteboy
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| posted on 15/1/13 at 12:00 AM |
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If you turn the injectors off, the pressure coming in from the bottom pushes right on the diaphragm/spring/seal and all the fuel goes out left. If you
open the injectors full the pressure on the spring reduces, reducing the bleed to the left, maintaining pressure.
The screw at the far right adjusts preload on the spring and thus the regulating pressure.
Meanwhile your injectors open for a duration determined by the ECU and deliver an exact amount of fuel because the pressure behind them (at the input
to the FPR) is held constant regardless of their flow.
[Edited on 15/1/13 by coyoteboy]
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Rob55
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| posted on 16/1/13 at 07:33 AM |
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Excellent lads thanks!
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BobM
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| posted on 16/1/13 at 04:05 PM |
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Most of the injected bike in-tank pumps have an in-built pressure regulator so no need for an external one.
One other issue not mentioned is that on a bike the hose from pump to throttle bodies is extremely short whereas in a car you often have the pump at
the back of the car and the engine up front. Bike pumps aren't really intended to supply fuel at pressure over this length of run with an
increase in resistance to flow.
So other options include:
1. Use a bike pump in a swirl pot up front in the engine bay (with low pressure pump feeding swirl pot)
2. Use a bigger pump at the back with a pressure regulator.
On my 'Busa engined Fury I used a swirl pot up front. On my current car I've got an Audi in tank pump with a separate regulator. Both have
worked well.
Not very Locost but very BEC 
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Rob55
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| posted on 16/1/13 at 05:43 PM |
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I no longer have the bike pump so I will probably just go with a separate pump and regulator!
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Rob55
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| posted on 6/2/13 at 12:23 PM |
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Just to follow up on this thread - I now want to plan where to put my fuel tank. The passenger compartment is not an option as I want to be able to
carry passengers too.
The only other two options are either above the diff or behind the diff. Above the diff is raising the centre of gravity, however behind the diff is
placing the weight behind the wheelbase of the car. Neither are particularly ideal for the handling of the car. I am just wondering if people have
any strong reasons why one would be any better or worse than the other?
Pics:
or
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loggyboy
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| posted on 6/2/13 at 01:10 PM |
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Personally I would go with lower CG over inboard weight.
Ratio wise, the higher option is pretty much as high as any major weight on the car, where as the moving it rearwood is a smaller percentage of
overall and outboard weight.... if that makes sense?!
Mistral Motorsport
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adithorp
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| posted on 6/2/13 at 01:59 PM |
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quote:
Originally posted by loggyboy
Personally I would go with lower CG over inboard weight.
Ratio wise, the higher option is pretty much as high as any major weight on the car, where as the moving it rearwood is a smaller percentage of
overall and outboard weight.... if that makes sense?!
As above. It also gives you the option of making a decent/usable boot box. I'd go with a filler on the top panel though, rather than the back or
side panels. Not seen a back panel filer yet that the owner didn't complain about difficulty using.
ps. Is that your car in the second picture? Directional tyres are on the wrong sides.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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Rob55
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| posted on 6/2/13 at 02:17 PM |
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Nope that's just a pic off the internet. My car looks a lot less further on than that lol
What's the complaint with the filler on the back panel?
[Edited on 6/2/13 by Rob55]
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loggyboy
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| posted on 6/2/13 at 02:54 PM |
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quote:
Originally posted by Rob55
What's the complaint with the filler on the back panel?
[Edited on 6/2/13 by Rob55]
I would imagine the doubling over to fill it, these cars are alot lower than tintops.
Mistral Motorsport
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adithorp
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| posted on 6/2/13 at 04:03 PM |
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quote:
Originally posted by Rob55
What's the complaint with the filler on the back panel?
[Edited on 6/2/13 by Rob55]
They take forever to fill due to splash-back/air locks causing the pumps to cut off. So you end up trying loads of different nozel angles before
resorting to just trickling it in.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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