STFC frequency seems high?

immortality
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Re: STFC frequency seems high?

Post by immortality »

Our 251,xxxkm VX Calais L67 is getting about 12.6/100 with average speed just under 40km/h. Still got more tuning to do since fitting 3.73 gears though, it seems to like a little more timing now in the cruise areas of the map so I've slowly been sneaking more spark advance in.
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Re: STFC frequency seems high?

Post by JohnDee68 »

antus wrote:If its got poor economy due to bad fueling for any reason it'd be too rich, and your O2 sensors which look like they're working would be showing off the scale rich as they are not widebands so will easily pass their limits. But your screen shot doesnt show that. So Im leaning toward the timing theory, that if its running a bit retarded power is lost in the stroke so you have to drive it harder.
Thanks antus. I am glad i am apparently reading the graphs correct also. I cant understand myself why the economy is out so much either. My vacuum gauge results also don't seem to point towards timing issues either at this stage. which leads me to fuels as a likely cause obviously.
vlad01 wrote:That's what I found with my old motors as well, good AFRs, fuel trim and cross counts were normal but still using some 3L/100 more than a fresh motor.
Thanks vlad01. Do you think running E10 give different results on economy while also seeing good graph activity? In years gone by, running between 91 & E10 would give me nearly 300Km better distance on E10 than 91. So now I try to always get E10.
The1 wrote:log looks fine to me. For reference our VX Wagon usually got on average about 13L/100km with mix of town and highway, with 330,000km on it. What figures are you getting?
Thanks The1, it is good to have a reference of near identical vehicles. I struggle to settle with less than 10L/100km from my car as it has and I have always been good with fuel usage in all my vehicles.

Here is some recent fuel usage readings for record. Keep in mind that previously (on other two engines as well) I would unlikely go below 30 mpg(uk) regardless of city or hwy. Hence why I feel strongly something is a miss with this one at the moment. The last record is after the trip in the country to test for any improvements the other day after injectors were (basic) cleaned.
Fuel recordings.png
Fuel recordings.png (18.56 KiB) Viewed 3629 times
Thanks again everyone, I appreciate your thoughts and feedback. I still wont give up on confirming that I can't get better economy from this motor until I have confirmed everything possible is right. including timing. :)
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Re: STFC frequency seems high?

Post by vlad01 »

Personally I have never noticed any difference from all the fuels available, E10, 91 or 98. There is only a 3% reduction in energy density in E10 over non blended fuels. 3% is less than margin of error stuff.
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Re: STFC frequency seems high?

Post by vlad01 »

I forgot I actually had a video demonstrating how much timing is affected by chain stretch.

This is on a high k engine I salvaged for parts and it's chain was quite sloppy. You can really see how many degrees of slop in the balance shaft at the start of the video, as well as lifter lift variation.


[youtube]https://www.youtube.com/watch?v=2oHX0t6hVDc[/youtube]
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Re: STFC frequency seems high?

Post by immortality »

vlad01 wrote:Personally I have never noticed any difference from all the fuels available, E10, 91 or 98. There is only a 3% reduction in energy density in E10 over non blended fuels. 3% is less than margin of error stuff.
In my experience I lost economy when running E10 from Gull here in NZ when I would normally run 91, easily 50-60km less per tank of gas. No tuning changes between fuels so a direct comparison.
vlad01 wrote:I forgot I actually had a video demonstrating how much timing is affected by chain stretch.

This is on a high k engine I salvaged for parts and it's chain was quite sloppy. You can really see how many degrees of slop in the balance shaft at the start of the video, as well as lifter lift variation.


[youtube]https://www.youtube.com/watch?v=2oHX0t6hVDc[/youtube]
Fuck me, that is terrible.

I did once drive a VN that had a missing timing chain tensioner. IIRC it had a propensity to stall at idle although it still did a great burnout.
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Re: STFC frequency seems high?

Post by vlad01 »

I'm sure most people have heard the "death rattle" these make when they have high Ks, the video shows what that is. It's the balance shaft gears lashing back and forth when the chain is flogged out and allows a lot of slop.

My old vacationer one (pic on the previous page or 2) was much worse than on this video.
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Re: STFC frequency seems high?

Post by immortality »

vlad01 wrote:I'm sure most people have heard the "death rattle" these make when they have high Ks, the video shows what that is. It's the balance shaft gears lashing back and forth when the chain is flogged out and allows a lot of slop.

My old vacationer one (pic on the previous page or 2) was much worse than on this video.
I'm definitely going to do some exploratory surgery during the xmas break.
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Re: STFC frequency seems high?

Post by vlad01 »

Another thing that might contribute is lifter bleed down, as they wear out they no longer can effectively take up the lash and make a ticking sound, especially at low rpms where the oil pressure is lower. I had this exact issue on my vacationer, the lifters had lots of lash at low rpms and sounded like a tin of marbles, much like poorly adjusted mech lifters.
This would reduce total lift and duration.
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Re: STFC frequency seems high?

Post by immortality »

I'm seriously contemplating a set of LS7 lifters. I'm going with LS6 valve springs so a better lifter and timing chain are really requirements for the upgrade.
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Re: STFC frequency seems high?

Post by vlad01 »

Yeah the "LS7" lifters are a good upgrade over stock.
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