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 608 Posts Member #: 1106 Post Whore Hungerford, Berks |
2nd Jun, 2011 at 09:17:25am
Up until now, I’ve not used the manifold pressure signal on the FPR. The injection setup I have on the 998NA has been fine. But as I cannot stop fiddling, I thought I would see what impact connecting the vacuum would have on the fuel pressure and resulting changes in the mega squirt tune, especially at tick over.
’77 Clubman build thread
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 (2)[/url] by [url=https://www.flickr.com/photos/150672766@N03/]Rod Sugden[/url], on Fli) 5988 Posts Member #: 2024 Formally Retired Rural Suffolk |
2nd Jun, 2011 at 09:39:11am
If it is a "normal" linear FPR then the actual fuel pressure should follow manifold pressure, ie, the fuel pressure should allways be the set figure above manifold pressure so the injector characteristics are constant.
Schrödinger's cat - so which one am I ??? |
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608 Posts Member #: 1106 Post Whore Hungerford, Berks |
2nd Jun, 2011 at 10:28:06am
Rod,
’77 Clubman build thread
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5988 Posts Member #: 2024 Formally Retired Rural Suffolk |
2nd Jun, 2011 at 10:38:35am
On 2nd Jun, 2011 Graham T said:
Am I right in my assumption that I should be seeing a reduction in fuel pressure of 10Psi? Essentially, yes, as 32kPa is approx 5psi(a) or minus 10psi(g). The important thing on a linear regulator is the fuel pressure should allways be a constant figure above the manifold/plenum pressure (so the pressure drop across the injector pintle is allways constant). Particularly important once you finish your turbo'd engine. BTW, 32kPa is quite a good manifold vacuum, I only see 55-60kPa at idle (but mine is a very low compression engine which also means it can't "suck" as hard as a high compression engine). Schrödinger's cat - so which one am I ??? |
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608 Posts Member #: 1106 Post Whore Hungerford, Berks |
2nd Jun, 2011 at 11:32:54am
On 2nd Jun, 2011 Rod S said:
On 2nd Jun, 2011 Graham T said:
Am I right in my assumption that I should be seeing a reduction in fuel pressure of 10Psi? Essentially, yes, as 32kPa is approx 5psi(a) or minus 10psi(g). Ah, good. - The absolute or Gauge was why I was not sure of what pressure drop I should see. Bad - I'm not seeing that pressure drop... On 2nd Jun, 2011 Rod S said:
Particularly important once you finish your turbo'd engine. Exactly why I'm still fiddling with the setup on the 998NA. I want to get the inlet manifold that I have created bolted onto the 998 so that I at least test and have a bench mark for when it is on the turbo engine, but I'm not going to do that until I have the FPR working as I expected it would. On 2nd Jun, 2011 Rod S said:
BTW, 32kPa is quite a good manifold vacuum, I only see 55-60kPa at idle (but mine is a very low compression engine which also means it can't "suck" as hard as a high compression engine). Thats a good point I had never thought of. The Turbo build is 8.2:1 CR. That will save me the trouble of posting in the future, asking why MAP at tick over is so high on the turbo engine. Just a thought- if the lower compression engine sucks less, presumably the effect that the Servo will have on assisting the braking will be less than with a higher CR engine? ’77 Clubman build thread
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608 Posts Member #: 1106 Post Whore Hungerford, Berks |
3rd Jun, 2011 at 08:00:05am
Problem solved.
’77 Clubman build thread
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