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How did the plugs look? Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Fri, 15 Aug 2008 09:13:57
In Reply to: boost / fuel issue .....Help..., kirk94aero, Thu, 14 Aug 2008 14:38:38 Members do not see ads below this line. - Help Keep This Site Online - Signup |
When the old plugs came out, how did they look? Signs of lean (or rich?) running? How do the new plugs look, now that they've been in for a bit. Of course, I'm assuming they're the proper NGKs gapped to a hair under 1 mm (.040)
Do the plugs all look the same? Any one look like it's running richer or leaner?
You can get decent boost at 2500-3000 rpm, and I assume it runs rough there (under boost). If you're coasting downhill at that RPM but at low throttle (no boost, lots of vacuum), does it still run rough?
As you know, boost related roughness can be ignition or fuel delivery. Swapping the DI and the right gap on the plugs covers most ignition issues. The CPS is either working or it isn't. So that leaves fuel - either too much or too little.
If the engine is running out of fuel under boost, it could be a clogged fuel filter, kinked fuel line, or bad FPR. If the FPR doesn't increase the fuel pressure with boost, the pressure drop across the injectors is less, and you get less fuel with more boost - a bad combination. The 'coast down the hill at 3000 rpm' test is there to see if it is boost related or just rpm related.
If the plugs are looking lean, I'd lean (pun intended) towards a fuel flow problem. The ideal test is to check both fuel pressure and fuel flow. It's easy to get pressure at low flow, but if the filter is clogged, the pressure will drop as the flow increases. It could also be a FPR that isn't R'ing (regulating). If the plugs are looking rich, I'd wonder if the the FPR is a little too enthusiastic.
posted by 192.249....
, Fri, 15 Aug 2008 09:13:57 <-- Viewing This Message, Sat, 16 Aug 2008 17:24:12
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