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Will higher volume injectors damage catalytic converter? 
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TO92 - Vaguely active

Joined: Thu Feb 16, 2012 6:07 pm
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I hope it is okay to ask an OEM related question here, I figured you guys would know the most about theory involving injectors a non-stock setup.

I recently had a low mileage engine installed in my 1999 Toyota Camry. The "new" engine was from a 2001, and while the internals and most peripherals are identical, the injectors are different. It is possible that the injectors from the 2001 engine are higher volume than my original engine (see below for detailed discussion about this*)

Anyhow, I wanted to use the "newer" injectors if possible for two reasons: 1) the old injectors have 300k miles on them, 2) the new injectors (from what I have researched) are a superior design giving much better atomization. (They are both Denso injectors)

I observed more power after the engine swap (though possibly due to factors other than injectors) and no apparent decrease in fuel economy.

After the installation and running the car about 500 miles, I got a P0420 code indicating the converter is running less than optimal. I was able to clear the code by fixing an exhaust leak (which appeared after disturbing the old exhaust system during the engine swap). However, this brought my focus on catalytic converter operation and I started doing some research into them.

My question:

If the "new" injectors are indeed larger volume, will running them (while still using the stock ECU/programming) damage my catalytic converter? And, if so, might I have damaged it already after 500 miles?


*The only information I could get on the difference in volume on the injectors is:

1999: 225cm
2001: 265cm

I do not know how accurate those specs are; after scouring the internet and calling several injector refurbishing shops, finding actual specs on these particular Denso injectors was impossible to find. The only exception was just what someone had posted on a Toyota forum based on the Toyota part numbers. When asking the poster what the source was, they were not able to give it to me; just some figures they had "lying around from somewhere". So whether those values are correct I cannot confirm.

Thu Mar 15, 2018 2:30 am
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Joined: Tue Jan 15, 2008 2:31 pm
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Some good questions. I'll give you some info, others can chime in if they want to.

1) cm is not a measurement of injector flow or behaviour, it's a small distance. cc/min is likely what your contact meant.
2) That difference, while not insignificant, wouldn't be crazy extreme rich, either. In particular, the ECU has learning capability and closed loop operation in certain areas. Likely just fine.
3) Not sure on longevity of cats with rich mixtures. They rely on rich/lean swings around stoich to achieve happiness. Oxygen sensors allow the ECU to achieve that.

Probably the wrong section, but I'll let it slide for now, far too late at night.

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Thu Mar 15, 2018 11:25 am
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TO92 - Vaguely active

Joined: Thu Feb 16, 2012 6:07 pm
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Thanks for that information, Fred.

1) cm is not a measurement of injector flow or behaviour, it's a small distance. cc/min is likely what your contact meant.

Yes, I understood it to be cc/min. I have largely seen injector flow rates referred to as "volume" and "cc"s on forums and stuff when referring to upgrading injectors for performance, with the time unit of min implied. So I thought I was following that convention. But yes, cc/min and "flow" is the correct designation.

Thu Mar 15, 2018 3:30 pm
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Joined: Sun Jul 18, 2010 2:35 pm
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The only time you will run richer is when you are in open loop conditions, by now in closed loop the ecu has done long term fuel trims to bring the fueling where it should be.
The size is around a 15% difference, which LTFT should handle, generally they will pop a to lean or to rich around +-25% LTFT.
When at WOT also the richer condition will cool the cat, provided all the fuel is being burned correctly and you don't have a missfire.
Extra fuel won't kill a cat, missfires will.

Subarus with cats pre turbo iirc run down to 9 or 8 AFR, very rich to keep the cats alive.

Thu Mar 29, 2018 7:53 pm
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