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Old 01-31-2008, 10:10 PM
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Ideal a/f ratio

hey everyone got a question everyone seems to have a differant answer to. Whats the ideal a/f fuel ratio ratio to be at under a boosted condition wot. Im not talkin 14.75:1 chemically ideal. im thinkin margin of safety fend of detonation good power daily driver blown motor.Any and all opinions welcome

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Old 01-31-2008, 10:27 PM
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10:1 is what most boosted applications look for at max.
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Old 01-31-2008, 10:31 PM
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Not sure this really helps, but they are the best at monitoring what's going on. Might have some usefullstuff.

http://www.innovatemotorsports.com/
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Old 02-01-2008, 12:25 AM
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I am curious if you are using a Blower like on the Corvette in my pictures, or what I call a Super Charger, also belt driven, but much smaller. The mother board in my other laptop took a dump (hard drive is ok), or I could give you this information right now. I have emailed customers with both types asking if it shows that information.

I don't do dyno testing, but these vehicles are everyday drivers, that run crisp and clean. I change spark plugs every 2 years as regular maintenance.
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Old 02-01-2008, 12:35 AM
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weiand 142 2.17:1 drive ratio 355 sbc afr195 8.33 speed pro dish nx268h supposed to be to about 7.5 8 lbs
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Old 02-01-2008, 12:56 AM
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Not knowing your exact BARO/ALT/TEMP it should good with that combination. The only true tell is reading the spark plugs.
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Old 02-01-2008, 08:14 PM
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Lower is safer, all the ones around here that I have seen on the dyno are usually 10:1 to 11.5 to 1. Rich tend to fend off pinging and cool things down a little . You are flirting with disaster for anything over 12:1 unless it is tuned perfectly. I have the pistons to prove it. If you are not running forged pistons you need to be extra careful
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Old 02-02-2008, 08:30 PM
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mighty 750 blower carb aem widband and autometer vacuum/boost gauge i was having a tough time with the idle circut but got it close enough to take it out on the street for the first time tomorrow (weather permitting bc rain is crazy sometimes). not that i'm going to thrash the thing just load it up pretty good to see which way i need to go
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Old 02-02-2008, 09:35 PM
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Way fat on the idle circit is a mega understatement!!

Forged pistons. Its at 17 inital and a total of 32 feels like it needs more though. Put brown cams in front and back with 35 squirts could probably pull back a size or two on the primary squirter but good to go around the block.

E Curve dizzy till i get things dialed then i'll add a 685 mallory box with boost retard. Carb # is 5402010bc dropped primary jets to 72 and 2.5 power valve for tuning idle circut . probably put 75 jets back in and 6.5 power valve it has 83 jets in the back and yes power valve is boost referanced

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Old 02-02-2008, 10:50 PM
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picked up a 1"spacer with pcv port "td2103" couple days ago i was gonna throw on tomorrow still gotta make a baffle in the valve cover for the pcv.

best i could get it to idle was about 1000 rpm 12" of vac (I think it should be higher) and 13.8 afr with the idle eze wide open and about a 1/4 turn on the front and back idle speed screws idle doesn't change much in gear pretty loose 2400 holeshot converter vacuum advance is still unhooked for now but it's pretty adjustable with the e-curve.

Good call on the pcv I was wondering about that. The power valve is run ref appropriately. I run chevron 94.
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Old 02-03-2008, 01:28 AM
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thanks for your help i'll update tomorrow
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Old 02-03-2008, 12:45 PM
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With the blower, unlike a turbo, the boost start in at pretty low rpm. If you do go to a higher stall remember you will most likely also need to increase transmission cooling capacity
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Old 02-03-2008, 12:57 PM
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really goin for streetabilty on this one thats why i went with the 2400 stall and conservative cam smallest i've ever run on a street warrior
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Old 02-10-2008, 06:34 PM
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Update

So i hooked up the pcv, put the 75, 88 jets back in with a 6.5 power valve
started it up and it went into a pretty rich roll so i dropped it down to a 4.5 power valve and it cleared up.

I also reset the the throttle plates to .020 the idle screws are out about 1 turn and it idles at about 12.5 to about 13.5 afr
with about 10hg of vac in neutral at 950rpm and about 8hg in gear at about 750 - 800 rpm the pipes smell clean and is fairly steady.

It really likes the idle eze wide open even with the throttle plates reset I haven't locked out the timing yet just kinda ran out of time. On light load the afr is in the mid 13's I didn't really get on it long enough to see what the afr was under good load
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Old 02-10-2008, 06:40 PM
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Quote:
Originally Posted by sheldonw
Update

So i hooked up the pcv, put the 75, 88 jets back in with a 6.5 power valve
started it up and it went into a pretty rich roll so i dropped it down to a 4.5 power valve and it cleared up.

I also reset the the throttle plates to .020 the idle screws are out about 1 turn and it idles at about 12.5 to about 13.5 afr
with about 10hg of vac in neutral at 950rpm and about 8hg in gear at about 750 - 800 rpm the pipes smell clean and is fairly steady.

It really likes the idle eze wide open even with the throttle plates reset I haven't locked out the timing yet just kinda ran out of time. On light load the afr is in the mid 13's I didn't really get on it long enough to see what the afr was under good load
So how are you coming up with the A/F Ratio? What are you using to come up with that?
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