oddsaabs
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| posted on 25/2/07 at 01:49 AM |
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Kawi fuel plumbing
So I’ve been fitting a Kawi ZX14 motor into a vintage Saab racer. It’s coming together nicely (abet slowly), but I’ve hit a snag. Perhaps the BEC
brain trust can help point me in the right direction.
The zx14 fuel system (EFI) doesn’t use a return line system like the zx12, but instead uses a deadhead system where there is no return line after the
fuel rail. The stock pump feeds into a chamber that has a small regulator attached which dumps extra fuel directly back into the tank. The fuel
chamber then has a line which runs directly to the fuel rail delivering 43 psi to the injectors.
Now I could retrofit the stock system somehow, but the way it’s constructed isn’t particularly contusive to being taken apart and reassembled in an
alternative configuration. What I’d rather do is install a quality aftermarket pump and regulator that will stand up to abuse and also be adaptable
to turbo-charging in the future. The only problem with this is that every high pressure fuel regulator I find is designed to fit in the return line,
and the zx14 doesn’t have one.
Regulators seem to be designed to keep the pressure correct in the incoming fuel line, and what I need is a regulator that keeps the correct pressure
in the outgoing line, sending the extra back to the tank via a return line. Simply stated, I need a fuel pressure regulator that fits between the
pump and the fuel rail instead of the more common design which fits in the return line after the fuel rail.
Confused yet? So am I. Any suggestions?
Thanks for your help.
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PAUL FISHER
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| posted on 25/2/07 at 05:03 AM |
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The sounds like my zx10 2006 engine has the same type of fuel system as the zx14,one line in from the pump,due to me turbocharging my engine I have
had to run a fuel pressure regulator and a return fuel line,along with a high pressure fuel pump,it sounds like up may need something like it, I will
try to explain how it works,although it maybe best to take a photo and post it,but hear goes,Ive run a fuel return from the tank to the return on the
pressure regulator,I have a feed to the new fuel pump,then a pressure line from the pump to the inlet on the regulator,I then have two T joins in this
pressure feed line,one goes to the fuel rail,and the other to a pressure gauge,so in operation,when the pump is run the pressure line is fed with a 5
bar pump,on tick over the regulator allows 3 bar pressure,returning the rest down the return pipe to the tank,but on boost this then goes up to just
over 4 bar,still returning an amount of fuel to the tank,thus ensuring pressure to the fuel rail is kept within safe limits,and not droping off on
boost,yours would use the same principle,although yours is not turbocharged yet 
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Hellfire
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| posted on 25/2/07 at 08:50 AM |
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For your info, ZX12R engines from 2002 onwards do not have a return line from the fuel rail. It has a single line from the pump in the fuel tank
delivering 43 psi to the injectors. The pump itself is easily accommodated within a custom built fuel tank and keeps the whole fuel system as
stock.
I guess if you intend turbocharging at a later date, then you'll need a system setup like Pauls but until you decide to turbocharge it, why not
keep things simple?
Phil
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oddsaabs
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| posted on 25/2/07 at 02:21 PM |
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I guess if you intend turbocharging at a later date, then you'll need a system setup like Pauls but until you decide to turbocharge it, why not
keep things simple?
Thanks for the suggestions.
Simple is good. Always choose the simple mouse trap over the one which is more complicated. While it is counterintuitive, in this instance the
simple solution would be to not use the stock pump unit. The native gas tank isn’t set-up for an internal pump and retrofitting it would be a major
hassle. The stock system has one line out of the side of the tank near the base that draws fuel via a mechanical pump on the mighty V4 motor.
Fitting the Kawi pump would mean drilling a large hole in the tank for the pump unit and having in run on it’s side. Do-able, but not preferred.
The good news is that Paul has a regulator that adjust the outgoing pressure to the rail. Any idea of the make and model?
The other good news is that Kawi uses the same deadhead system on other bikes! That explains why the part # for the ‘14’ fuel pump unit is the same
for the ’12’ and ‘10’. There have been plenty of turbo units to these motors, and they all required upgrades in the fuel delivery system. This
shouldn’t be as hard as I’m thinking it is.
In a separate note, I really appreciate the help and the resources this forum provides. What did we do before we could share information on the web
like this? You cats are a really great bunch, I only wish I had the experience and knowledge base to add to the discussion more often.
Thanks again.
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