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> CHT temps, individual cylinder differences?
jd74914
post Apr 16 2018, 05:35 AM
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Good point. Totally forgot about that.
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falcor75
post Apr 16 2018, 09:22 AM
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Target lambda is around 0,92 (8% more fuel than lambda 1.0) But at the moment I'm not using the lambda control function since thats not been fully mapped. Running off the VE and Ignition tables only. Screen shots below. This is only the map from the dyno. We still need to get some street fine tuning done especially when cruising.

Attached Image

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My injectors were flowchecked and the results were at 3 bar of static pressure:
369, 369, 369 and 377 cc/minute. I'm not sure which injector is on what cylinder
but if the 377 one has ended up on cylinder 2 that could contribute to the lower temp but
its still a mystery why it would flow less air. I did set all the valves during the winter when I had the engine out.

I can try and swap the #1 and #2 cylinder injectors and see if that affects anything.
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barefoot
post Apr 16 2018, 02:12 PM
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QUOTE(falcor75 @ Apr 15 2018, 07:28 AM) *

Just spend the last 3 hours fiddling with the thottles.



The odd one out is still #2, when the others draw just below the 6 mark, #2 draws like 4,5-4,8, about a full scale marker lower and the temp is around 95 C or 205F.

What could cause #2 to draw that much less air? air leak between head and manifold, airleak between manifold and throttle body are the only things I can come up with....


I've just been playing with carb idle air flow issues with one carb. The exact opening at the butterfly's at idle was very difficult to get even on one carb. At idle, there is VERY little open area at each butterfly. The stock injection system avoids this by using a single butterfly for all 4 cylinders, so much larger open area at idle. use some very thin feeler gages to measure butterfly opening on adjacent cylinders.
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falcor75
post Apr 17 2018, 03:42 AM
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I cant get a 0,05 mm feeler gauge in so both butterflies are pretty much closed...
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falcor75
post Apr 18 2018, 01:37 PM
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I spent 20 minutes this afternoon swapping the #1 and #2 injectors around, didnt have time to start up the engine and let it warm up tho, hopefully before the weekend.
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falcor75
post Apr 20 2018, 08:08 AM
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Had a 40 minute drive today, starting with slower traffic and then a bit of 55 mph freeway in 4th gear before refueling after the winter and then a few minutes of 3200 rpm in fifth gear. CHT temps were around 285-290 for all cylinders except #2 that still reads in the 245-250 range.

Adjusting the throttle linkage and idle air seems to have smoothed out the temps over cylinders 1, 3 and 4 so at least a partial success. Hopefully I'll get some cruising tuning done in the next weeks and then enjoy a summer of more driving and less wrenching.

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On the way home we stopped at a local landmark over some 17th century field marshal and snapped a few photos. Its been so cold this spring that the grass has barlely turned green yet. First day this year with temps above 70 F.
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jcd914
post Apr 20 2018, 11:25 AM
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After reading through this and your struggles to get the air flow balanced for each cylinder.

Do your throttle bodies not have an air bypass screw for each cylinder?
This is benn the standard on carbs for years and I have not seen a throttle body that did not have balance screws. I can't say that I have seen a lot of throttle bodies up close but I have seen and adjusted a few.

What brand and model of throttle bodies do you have?

At least the cylinder that is different is running cooler and not hotter that the others.

Jim
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falcor75
post Apr 20 2018, 12:01 PM
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No they only have one air bleed screw for each pair, I didnt know this when I bought them or I might have gotten something else.

https://vwspeedshop.com/product.php?product...=395&page=1
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jcd914
post Apr 20 2018, 05:29 PM
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Too bad.

Their description says there is a vacuum balance tube between the cylinders, if there is and it is open there should not be any flow difference at idle.

But then I am not sure what they are describing r what its function is.


Jim
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falcor75
post Apr 20 2018, 11:42 PM
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Yes I'm not sure there's any fault with the throttle body.
Might be the cylinder or valve train, guess I need to make a compression check or leakdown test. Its just such a bother since the space is sooooo tight I'll have to take the throttle bodies and manifolds out.
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