What happens if added smaller main jets ?

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Dumindu
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My tercel:: 1987 Toyota tercle 4wd DX Wagon 1452CC
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What happens if added smaller main jets ?

Post by Dumindu » Mon Aug 12, 2019 6:29 am

My car is a 1987 Toyota Tercel DX Wagon RHD 1452cc manual driven car. It has a Aisen 2 barrel carburetor.

It is told that the main jets sizes should be 99 and 156.

Does it affect the function if the they are replaced with size 85 and 105 respectively.

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Petros
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My tercel:: '84 Tercel4wd w/extensive mods
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Re: What happens if added smaller main jets ?

Post by Petros » Mon Aug 12, 2019 10:32 pm

I can not answer that, I have not tested different size jets in the factory carb.

but I know I have driven different year Tercel4wd with noticeably different power out put on hard acceleration, and I have heard of some getting better than average fuel economy. All with the factory emissions and fuel system.

if that was due to two different main jet sizes, than that might explain it. But I did not get to verify which one has which fuel jets in the carbs.

However, just going smaller jet many not improve economy, but it could lower max power output. There is not a large range of air/fuel ratios that will run properly, too lean and the fuel economy drops as well as total power output being reduced, it just becomes very inefficient.

of course too rich will also reduce fuel economy, without an attendant increase in power out put.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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Dumindu
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Re: What happens if added smaller main jets ?

Post by Dumindu » Tue Aug 13, 2019 12:12 pm

Thank you for your advice.

xirdneh
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Re: What happens if added smaller main jets ?

Post by xirdneh » Wed Aug 14, 2019 10:00 pm

I have never seen a 99 jet on stock carb. I have messed with a lot of these carbs. 101 is the smallest and most common i have seen. 102 and 103 show up once in a while. 106 was the largest (1 carb). 106 makes for a noticeable increase in power but only got around 24-26 mpg. 101 gets me in the 28-32 mpg range.
Love those Tercell 4x4 wagons but they sure suffer from road noise.

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