Any way to test that?

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There's supposed to be a fairly large temperature difference between the front and back of the cat. There's  also supposed to be minimal pressure difference. Any MR2 experts know the normal ranges for these? I don't have a lot of experience with engines, most is just reading I've done, and I read that a blocked cat was a common cause for poor fuel economy in MR2s.

mr2y
There's supposed to be a fairly large temperature difference between the front and back of the cat. There's  also supposed to be minimal pressure difference. Any MR2 experts know the normal ranges for these? I don't have a lot of experience with engines, most is just reading I've done, and I read that a blocked cat was a common cause for poor fuel economy in MR2s.

Not entirely sure how I'd test any of that apart from just holding the exhaust pipe on one side of the cat, then the other and see if the burns match up.

Jokes aside, can't I take the cat off and visually inspect it also?

I'm actually not sure how the temperature difference theory works, but some cars have two O2 sensors, one before the cat and one after. Don't go burning your hands just yet, I think the differential would be quite small if I was to guess. I've also seen a youtube video where the mechanic drills a hole (lol) before the cat and one after it, and sticks a pressure probe in each hole to get pressure measurements. Interesting stuff, but again, I have no practical experience, I was hoping there is an exhaust expert on this forum to offer some actual sane advice.

Might I add I think this is a case where the instruments, expertise and time needed for testing the cat exceed the cost of just replacing the thing, but it's interesting to learn anyway.

mr2y
I'm actually not sure how the temperature difference theory works, but some cars have two O2 sensors, one before the cat and one after. Don't go burning your hands just yet, I think the differential would be quite small if I was to guess. I've also seen a youtube video where the mechanic drills a hole (lol) before the cat and one after it, and sticks a pressure probe in each hole to get pressure measurements. Interesting stuff, but again, I have no practical experience, I was hoping there is an exhaust expert on this forum to offer some actual sane advice.

What are you talking about, using my bare hands to measure the heat of both pipes around the cat while the car is running is perfectly sane!

I feel like you might be on to something here though - as stupid as it sounds, sometimes when you mash the go-fast pedal, you feel that hesitation. As if gases were getting stuck in the exhaust. Ergo, blocked cat. Especially considering swapping out the spark plugs, dizzy cap and rotor did nothing. If only there were a way to test it simply.. I may have to take a trip into an exhaust shop.

Does anyone know the dimensions of the cat? Might ask for a quote for a new one. Oh and would I see much of a benefit from a hi-flow cat on an NA? I can't imagine I would

Only if you want to change the sound of it I guess. I put a high flow cat on a Pulsar once and it totally changed the sound. Went from a bassy hum to a sharp crackle. I preferred the factory one but the high flow was louder and flowed better. Did you get the new O2 sensor on?
 
Edit: oh and you'll probably get +2 HP...

Not yet, no. I don't even know where the O2 sensor on this car is (Eric tried helping me but mine apparently isn't in the same location). I'm guessing it's further up the exhaust system under the engine but I haven't bothered finding it yet

That plus the fact that I bought a Denso universal one - so I'll have to crimp the factory plug onto this new O2 Sensor, but I also don't know if it's going to mount properly either. I've seen a few O2 sensors have that a plate on the 3SGE, whereas mine doesn't.. I found some pictures to explain what I mean
 


One I bought



Plated one

What sort of kilometerage are you getting? According to:
 
http://www.mr2australia.com/mr2play/tm.aspx?m=1762
 
it should be about 10L per 100k with moderate driving. Actually I noticed when I had a Paseo with a 1.5L engine I could use more fuel than my 1.8L Corolla mainly because it was a manual. But on the highway the Paseo would use like 5.5L/100k.

According to that I should be getting 550kms to a tank. Realistically, it's more like 415-430 kms if I'm lucky to the point where it's running dry

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