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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Sat Aug 22, 2020 11:51 am Post subject: California Smog test, NOX and Compression Ratio on 2L |
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Question for California smog bus owners with late 2L bay engines
What compression ratio are you running, what deck if you know, what are your NOX numbers on tests, and what head temps on the freeway? I am trying to determine how much bumping the C/R from 7:1 to 7.5:1 will affect NOX on the smog tests, and head temps.
For example - my bus engine has run with both 7.3:1 and 7.0:1 pistons.
7.3:1 deck .100" NOX was 621/545 and head temps were 410 F - 425 F
7.0:1 deck .100" NOX was 652/554 and head temps were 395 F - 410 F
I might add - Colin has a stock 1977 and 1978. According to his posts, he typically got an average of 410 F - to a max of 444 F head temps up a hot desert grade. The engines were stock at that time, original which would be 7.3:1 and it can be assumed that the NOX would have been within factory specs to pass smog. That kind of agrees with the 7.3:1 engine I built but his deck would have been .60" with a stock chamber volume. _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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tommu Samba Member
Joined: November 15, 2011 Posts: 616 Location: L.A.
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Posted: Sun Aug 23, 2020 8:04 pm Post subject: Re: California Smog test, NOX and Compression Ratio on 2L |
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I'm running 7.3.1 with a .074 deck.
After break in I was getting head temps between 390 and 415f. This was with a very lean tune to pass SMOG. 98/33 nox. This tune was so lean I was getting some stumbling when pulling away and a little bit of a lean miss at idle.
I'm running maybe a little too rich now, but it seems to be what the motor wants. it's driving very nicely. I'm peaking at 405f in the recent heatwave on long steep inclines and hanging around 485f on the flats.
I'm wondering if that 7.0.1 compression ratio was a nice way to lose some grief from owners of aging buses! _________________ |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Sun Aug 23, 2020 8:55 pm Post subject: Re: California Smog test, NOX and Compression Ratio on 2L |
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tommu wrote: |
I'm running 7.3.1 with a .074 deck.
After break in I was getting head temps between 390 and 415f. This was with a very lean tune to pass SMOG. 98/33 nox. This tune was so lean I was getting some stumbling when pulling away and a little bit of a lean miss at idle.
I'm running maybe a little too rich now, but it seems to be what the motor wants. it's driving very nicely. I'm peaking at 405f in the recent heatwave on long steep inclines and hanging around 485f on the flats.
I'm wondering if that 7.0.1 compression ratio was a nice way to lose some grief from owners of aging buses! |
maybe - your numbers are really nice but I think you meant 385F not 485F Nicer than mine at 7:1. _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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tommu Samba Member
Joined: November 15, 2011 Posts: 616 Location: L.A.
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Posted: Mon Aug 24, 2020 2:35 pm Post subject: Re: California Smog test, NOX and Compression Ratio on 2L |
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SGKent wrote: |
tommu wrote: |
I'm running 7.3.1 with a .074 deck.
After break in I was getting head temps between 390 and 415f. This was with a very lean tune to pass SMOG. 98/33 nox. This tune was so lean I was getting some stumbling when pulling away and a little bit of a lean miss at idle.
I'm running maybe a little too rich now, but it seems to be what the motor wants. it's driving very nicely. I'm peaking at 405f in the recent heatwave on long steep inclines and hanging around 485f on the flats.
I'm wondering if that 7.0.1 compression ratio was a nice way to lose some grief from owners of aging buses! |
maybe - your numbers are really nice but I think you meant 385F not 485F Nicer than mine at 7:1. |
Ah yes would be a bit too much _________________ |
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