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08-17-2009, 05:31 PM
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#1
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Super Moderator
Join Date: Dec 2007
Posts: 6,850
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How can a carb be tuned off of an engine?
I hear about people sending their carbs off to 'pro tuners' to get it dialed in on... a flow bench? I'm guessing.
But if my carb works fine on a stock motor, then goes lean on a H&C motor, gets retuned to run right, then after adding a blower it goes lean again and needs to be retuned, how in the hell can you tell what that carb is going to do off of the motor?! It obviously can't be just a simple AFR reading with a given cfm off of some bench.
Giving ALL of my motor specs to Lars who is supposed to be the carb God he can't even tell me exactly what size bleeds and jets to run, even with a baseline AFR reading. So how the hell can ANYONE tune a carb off of the motor, without a wideband hooked up? Furthermore reading plugs is like reading an overall GPA, it's only good for an average.
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I <3 forced induction.
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08-17-2009, 06:14 PM
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#2
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Fast & Filthy
Join Date: Jun 2008
Posts: 3,840
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I don't know what other carb shops do it but I can tell you what The Carb Shop in Ontario does. First they find out as much about your combination as possible. Once they build the carb they dyno it on an engine. The engine they use is a SBC that make just over 600hp. This gets the carb in the range it needs to be but it's not exact. They rebuilt my carb years ago and it was too lean for my engine. I had to up the jets sizes and tune the cam and discharge nozzles to get it right.
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08-17-2009, 07:53 PM
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#3
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I, Vettezuki
Join Date: Feb 2006
Posts: 14,754
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I'm thinking computerized fuel injection was a truly great development. 
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08-19-2009, 09:49 PM
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#4
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Power's off.
Join Date: Dec 2008
Posts: 673
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Quote:
Originally Posted by enkeivette
I hear about people sending their carbs off to 'pro tuners' to get it dialed in on... a flow bench? I'm guessing.
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http://www.circletrack.com/techartic...ing/index.html
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Chrome don't get you home.
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08-19-2009, 09:52 PM
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#5
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Power's off.
Join Date: Dec 2008
Posts: 673
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Quote:
Originally Posted by enkeivette
Giving ALL of my motor specs to Lars who is supposed to be the carb God ......................
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Please show a little more respect. If YOU knew 10% what he did, you'd be done by now, huh? 
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Chrome don't get you home.
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08-20-2009, 01:58 PM
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#6
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Super Moderator
Join Date: Dec 2007
Posts: 6,850
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Quote:
Originally Posted by big2bird
Please show a little more respect. If YOU knew 10% what he did, you'd be done by now, huh? |
How was I disrespectful at all? I referred to him as the carb God, using him as an example saying that if he can't do it, no one can.
...I'm putting him on a pedestal. 
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I <3 forced induction.
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08-20-2009, 03:30 PM
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#7
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Neanderthal
Join Date: Mar 2008
Posts: 5,320
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__________________
64 Vette Roadster 400 ci
1990 F150 351 ci SuperCharged
48 Harley Pan Head 76 ci
2016 Nissan Altma
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08-20-2009, 09:35 PM
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#8
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Power's off.
Join Date: Dec 2008
Posts: 673
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Quote:
Originally Posted by enkeivette
How was I disrespectful at all? I referred to him as the carb God, using him as an example saying that if he can't do it, no one can.
...I'm putting him on a pedestal. |
I'm sorry Adam. I guess I just took it wrong. I apologise.
__________________
Chrome don't get you home.
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08-20-2009, 10:05 PM
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#9
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Super Moderator
Join Date: Dec 2007
Posts: 6,850
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Quote:
Originally Posted by big2bird
I'm sorry Adam. I guess I just took it wrong. I apologise.
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You are right about this taking forever. And being 100 miles South of my car during the week doesn't help. 
__________________
I <3 forced induction.
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08-22-2009, 04:10 PM
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#10
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Senior Member
Join Date: Dec 2008
Posts: 123
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Even with the carb ON the engine it's going to run with there are too many variables. Air temperature, humidity, air density, and fuel quality just off the top.
Trying to get the A/F ratio 100% perfect in all conditions is asking a lot. IMHO, it's not going to happen. Just get it close as possible for the 70-80% of the time for the conditions the engine will be run in and let it go. If you're going for all out racing, then tune for WOT, cruisng, then setup for midrange. with it fat enough it won't get too lean for that occasional WOT blast.
Digital FI is a great thing since it constantly adjusts the A/F for the best mixture, but it's still not going to keep it EXACTLY at the optimum at all times.
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