Thats more like what I'm thinking and seeing. The engine is 8.5:1 I've been told by the builder and the cam is 235/245 on 116. I did have Iridiums in it but am now using NGK TR plugs. Were you reading rich or lean? It seems to me like its very inefficient at that point
I could not give you an AFR as I did not have the gear to measure at the time however definitely very very rich. Idle dropped from 750 - 800 down to maybe 400. Engine would only barely idle black smoke billowing from it (with an inspector and cop asking me questions). I think the VL's standard compression was 7.8:1 (which mine was). NGK rep said he had never heard of it before however spoke to a tuner and they had the issue often and said that if you use the iridium's you needed to go 1 or 2 heat ranges hotter (depending on engine) as they would foul at low loads every time. He said standard compression they were fine however lower compression turbo applications he said to avoid them. After a lot of searching through the VL's fuel and ignition circuits and finding nothing of value (in tank lift pump U/S but fitting new one did not help) I gave up and fitted $12 worth of new spark plugs (only ones I could get on a Sunday arvo. Was running NGK-R's) and problem was forever solved (did this before I spoke to people). The plugs were all fouled to the same degree and it was like they had been painted mat black.
I'm not running Iridium plugs now and still have the issue, shame you didn't see the mixture. I think it may be somehow related to the largish cam and lower compression, I have customers with VL's that run 9's on ETs with low comp and big cams that don't have this issue though so still confused. The mixture is definitely not rich by AFR's but is visibly smokey and fouls plugs. I believe it is an efficiency thing.
Yeah only got my hands on that sort of stuff recently. To ask the silly questions the fuel pressure is ok and the injectors are not leaking? Maybe try hotter plugs? Hope you figure it out soon.
Fuel Pressure is good, you'd. I did go from 7-6 in the NGK, catch 22 too cold when part throttle too hot under full load
I don't claim to be a guru on the matter however I see it best to at least try the original heat range with a plain jane plug (my issue was fixed with a cheap set of champion plugs) and see if it fixes the low load fueling issue. If it does then attention can be turned to the issue that they may be too hot under load however I have found that usually these issues are best restarted from a known point. In this case the standard heat range. Wind up slowly and see how hotter plugs hold up which likely means pulling them after a run or two.
For boost you shouldn't really be running platinum/iridium plugs (the tip is very fine and does not shed heat very well)...
try something like NGK TR6.
Not running Iridium.
I had a coil go bad that would work fine under full throttle but idle and part throttle coil didn't work correctly. I took a temp gun and checked each header temp and found #8 was 180 * cooler than the rest. Replaced coil and been good ever since.
Might it be worth running a lower octane fuel (and staying out of boost) to see what effects it has on this issue? Just for reference, have you checked compression to see what this engine cranks at with such a large cam/low static comp? Also if you're still concerned about the exhaust being restrictive, check the pressure, if you don't have the tools a local exhaust shop should have (for the purpose of checking for a plugged catalyst). With all the issues so far, this hasn't "made oil" has it? If it were running rich enough to get significant fuel passed the rings the cylinders could be getting washed down. Simple to check the oil and make sure it isn't overfull nor smells like fuel. Don't overlook the basic mechanical stuff just because it's a hipo setup. ...Just some ideas that may give insight as to if this really is a tuning issue or something else.
Last edited by FirstGenThree; September 21st, 2013 at 03:26 PM.
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