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chompy
Samba Member
Joined: August 12, 2014
Posts: 400
Location: Cascade Locks
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 Posted: Mon Oct 13, 2014 4:17 pm Post subject: Aircooled compression numbers - suggestions? |
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Hey everyone, recently took a 1600+ mile trip down the coast and back in our 81 aircooled westy. It seemed to drive fine but has it's interesting quirks. I checked my compression when I got back. Here's the numbers I got:
#1 - 105#
#2 - 109#
#3 - 109#
#4 - 115#
The specs in the bentley say it could be lower, but I was hoping to get some opinions from the community whether this engine needs to be dropped and checked out. Thanks! |
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the joker
Samba Member
Joined: October 12, 2006
Posts: 1287
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| Posted: Mon Oct 13, 2014 5:23 pm Post subject: |
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81 with original eng?
That's looks normal for a tired 81 eng
Change the oil Lucas treatment
Drive it easy , and start thinking rebuild
If your handy with a wrench, not a hard rebuild
Good luck |
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?Waldo?
Samba Member
Joined: February 22, 2006
Posts: 10155
Location: Where?
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| Posted: Mon Oct 13, 2014 6:12 pm Post subject: |
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| That's totally within spec for the air-cooleds. Spec is 87-131 with a minimum of 73. Max difference between cylinders is 44. Your max difference is 10. Your numbers are right in the middle of spec with close numbers and you know this because you said in your initial post you know the Bentley specs. What more do you want? It seems like you're trying to invent an issue when there isn't one. |
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chompy
Samba Member
Joined: August 12, 2014
Posts: 400
Location: Cascade Locks
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| Posted: Mon Oct 13, 2014 6:20 pm Post subject: |
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| That's totally within spec for the air-cooleds. Spec is 87-131 with a minimum of 73. Max difference between cylinders is 44. Your max difference is 10. Your numbers are right in the middle of spec with close numbers and you know this because you said in your initial post you know the Bentley specs. What more do you want? It seems like you're trying to invent an issue when there isn't one. |
Truth be told I am having trouble passing DEQ. I have a center mounted progress carb that the PO put on. Although I know this is the center of my problems, I was wondering if the compression being so low might be adding to my high CO levels. In my current situation I'm looking into finding an affordable EFI system or last case scenario getting some weber 40 IDFs.
If I'm going to go to the trouble of working out the EFI system I wanted to be sure it was worth it so I did a compression test. |
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?Waldo?
Samba Member
Joined: February 22, 2006
Posts: 10155
Location: Where?
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| Posted: Mon Oct 13, 2014 6:46 pm Post subject: |
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| chompy wrote: |
| I was wondering if the compression being so low might be adding to my high CO levels. |
The compression is not low. It is solidly within spec. Carbs were eliminated from production vehicles in the US specifically because of emissions requirements. I doubt that you will be able to pass DEQ with either your progressive or any replacement carbs without running lean enough to drop a valve seat. Increasing the compression ratio would likely assist in both reducing emissions and dropping valve seats... |
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Wasted youth
Samba Member
Joined: July 06, 2012
Posts: 5175
Location: California's Hot and Smoggy Central Valley
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| Posted: Mon Oct 13, 2014 7:16 pm Post subject: |
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I assume you performed a valve adjustment with the engine cold before you did the compression check, and you had the intake held wide open.
I also assume the DEQ inspection is an emissions test. Here in California a dynamic treadmill two-stage test is used, and I would have serious doubts that an engine factory delivered with fuel injection would pass with anything other than what it left the factory with, so I would recommend you go back to stock if you want your van to pass... Assuming again that the DEQ is equally stringent to California.
I think the important thing about your readings is that they are nearly uniform, and not off by a huge difference from one another. I do not feel your compression readings are seriously low. Did you do the rest wet or dry?
Are you able to perform a leak down test?
I like stock fuel injection so far. I had a nice running 1977 bay window that I passed the California smog check with, and currently have a 1981 Vanagon that I am gearing up to get it passed and registered. I prefer stock over mods, anyway. People shitcan fuel injected stuff all the time, the trick is to get the correct ECU, the right wiring harness and the right distributor.
Last edited by Wasted youth on Mon Oct 13, 2014 7:24 pm; edited 2 times in total |
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Wildthings
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Joined: March 13, 2005
Posts: 52742
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| Posted: Mon Oct 13, 2014 7:32 pm Post subject: |
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| I was able to get a 1600 with a progressive to meet the proposed specs for the late 80's way back around 1981. Not sure that with today's pollution causing gasahell I could do the same no matter the condition of the engine. |
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chompy
Samba Member
Joined: August 12, 2014
Posts: 400
Location: Cascade Locks
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| Posted: Tue Oct 14, 2014 6:24 am Post subject: |
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| Wasted youth wrote: |
I assume you performed a valve adjustment with the engine cold before you did the compression check, and you had the intake held wide open.
I also assume the DEQ inspection is an emissions test. Here in California a dynamic treadmill two-stage test is used, and I would have serious doubts that an engine factory delivered with fuel injection would pass with anything other than what it left the factory with, so I would recommend you go back to stock if you want your van to pass... Assuming again that the DEQ is equally stringent to California.
I think the important thing about your readings is that they are nearly uniform, and not off by a huge difference from one another. I do not feel your compression readings are seriously low. Did you do the rest wet or dry?
Are you able to perform a leak down test?
I like stock fuel injection so far. I had a nice running 1977 bay window that I passed the California smog check with, and currently have a 1981 Vanagon that I am gearing up to get it passed and registered. I prefer stock over mods, anyway. People shitcan fuel injected stuff all the time, the trick is to get the correct ECU, the right wiring harness and the right distributor. |
Ya, I did adjust the valves shortly after I bought the car, a couple months ago. I did have the intake wide open when I had the engine cranked over. Unfortunately I don't have a leak down tester. I wasn't sure about the values I got so that's why I was double checking on here.
I've gone through the deq so many times. I just have to find stock fuel injection parts to bring it back to square one.
Thanks for the tips and help everyone. |
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MarkWard
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Joined: February 09, 2005
Posts: 19134
Location: Retired South Florida
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| Posted: Tue Oct 14, 2014 7:26 am Post subject: |
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| I would think that with a good catalytic convertor and someone that can tune the weber progressive, you should be able to get it clean enough to pass emissions. When I say tune, it might require different fuel and air jets. The progressive gets no love for many reasons, but will get you down the road in a pinch. |
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chompy
Samba Member
Joined: August 12, 2014
Posts: 400
Location: Cascade Locks
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| Posted: Tue Oct 14, 2014 3:56 pm Post subject: |
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| rsxsr wrote: |
| I would think that with a good catalytic convertor and someone that can tune the weber progressive, you should be able to get it clean enough to pass emissions. When I say tune, it might require different fuel and air jets. The progressive gets no love for many reasons, but will get you down the road in a pinch. |
Ya, I've had a weber on an old subaru and it was very efficient and easy to tune. I'm not sure if it's solely the long runners but it's much harder to tune on this engine. |
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