Mods that richen the engine - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 10-04-2000, 11:05 PM
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Mods that richen the engine

I put in the Holley TBI and the Hypertech Thermomaster chip and have noticed a slight change [img]/wwwthreads_images/icons/crazy.gif[/img] in the exhaust. I have yet to receive a code though, warning that it is too rich. Should I leave it alone? I know that I can adjust the TPS switch or the fuel pressure regulator to lean out the engine, if need be. What is the best air/fuel ratio to run?

Al [img]/wwwthreads_images/icons/smile.gif[/img]

'87 Jimmy 4X4 2.8L [img]/wwwthreads_images/icons/crazy.gif[/img]
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post #2 of (permalink) Old 10-05-2000, 01:04 PM
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Re: Mods that richen the engine

Hi Al,
I have talked to the programmers at super chips and they told me that on the GM vehicles, they tend to lean them out a bit and change the timing curve if it is a mostly stock motor. This gives a boost in power and better gas milage. As far as the air/fuel ratio, the optimum ratio is 14.7:1. this is what your oxygen sensor is for, to tell the computer to richen or lean the motor to keep the mixture as close as possible to 14.7:1. I wouldn't change anything if your truck is running well and you are satisfied with the power gained. If you want to go farther, TBI spacer, intake and exhaust will really make a noticable increase in power. You can get a custom chip to enhance your performance when you have made major mods such as bigger cam and higher fuel pressure and larger cubic inches. Hope this helps. [img]/wwwthreads_images/icons/smile.gif[/img]
David G.

'91 S15 Jimmy 5.7L 4X4
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