Simon
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| posted on 12/3/07 at 09:55 PM |
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Fuel pressure reg - fixed or rising rate?
Chaps,
What do you think? I'm thinking rising rate, as it'll allow for linear increases in injector opening times under boost, rather than
increasing times for boost, and drop in fuel pressure.
Do you agree? Or not
Also, any suggestions on how to make a vac advance distributor function properly under boost; ie no vacuum.
Thanks
ATB
Simon
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PAUL FISHER
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| posted on 12/3/07 at 11:10 PM |
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Rising rate is the one to go for,conected to your inlet plenum,Ive got a begi unit fitted,45psi fuel pressure on tickover,65psi on boost,your settings
may not be the same,but turbo engines use rising rate regulators..jpg)
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BenB
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| posted on 12/3/07 at 11:26 PM |
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Personally for boosted engines I'd want the flexibility and control of a non-dizzy (ie EFI) setup....
Aren't rising rate regulators a way of avoiding further complications when adding a turbo to a stock setup? ie a way of getting round problems
with the fuel metering?? I might be wrong though
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Simon
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| posted on 13/3/07 at 01:04 AM |
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Paul,
OK, next q. Where from and how much and alternative suggestions? I found the US site, but no UK suppiers, apart from an MX5 site.
Cheers
Simon
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bartonp
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| posted on 13/3/07 at 09:18 AM |
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Fixed rate - this way your ECU has control of the fuelling as fuel delivered is proportional to injector opening time (always assuming your injectors
are sized sufficiently). The only variables are then the ones YOU dial in when mapping.
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Simon
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| posted on 13/3/07 at 08:37 PM |
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bartonp,
Yeah, but as I'm turboing, does the effective pressure not decrease with boost ie without boost I'll get (say) an injector pressure of
45psi. Running 14psi boost my injector pressure will be reduced to 31psi, requiring longer injector openings (taking them closer to "always
open", whereas rising rate reg will compensate for this, and I'll not need to extend injector open time.
Thoughts please
ATB
Simon
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NS Dev
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| posted on 13/3/07 at 09:27 PM |
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no no no no no!! (as in your thinking is right but you've missed a critical detail! )
You pipe the inlet manifold to the pressure pipe on the back of the regulator. All the decent ones have these, and on a N/A setup its just left open
to atmosphere (or that's what I do anyway) but on a turbo setup it is piped to the inlet and exactly offsets the boost pressure, i.e. 50psi fuel
plus 20psi boost will give you 70psi fuel measured on a guage on the line.
A rising rate reg will give you 1.7 times approx the press change i.e. it just complicates things.
Any pressure reg with a port that feeds pressure to the back of the diaphragm, that can work with your intended boost press plus your baseline fuel
pressure will be fine.
FSE ones are common but not very reliable and can suffer fuel press fluctuations.
[Edited on 13/3/07 by NS Dev]
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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Dale
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| posted on 13/3/07 at 09:35 PM |
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My understanging is exactly as ns dev says.1 lbs increase for 1 lb boost. The drag guys that use my lima engine run it that way and the factory runs
it the exact same way. The common way is to use an adjustable regulater that is set to increase at a 1/1 to the boost level.
Dale
Thanks
Dale
my 14 and11 year old boys 22
and 19 now want to drive but have to be 25 before insurance will allow. Finally on the road
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