ZiG

Just wondering what observations have been made. If someone with an OBDII reader and a new car could read the operating temperature that'd be awesome. Looking specifically for new cat temps if possible.

My cat has 60k miles, looked clear visually, from the front anyway (nothing obvious st least), and runs around 800 C. That seems in love with others.. I know people say a sign of a clogged cat is that it glows red, but would like to know what a fresh one runs at, specifically on a rotary motor.

delhi

IIRC during my last spirited drive, my Torque BT OBD-2 registered a range from 750C to low 900C. At idle, it usually hovers low 800C.

Steve Dallas

This is a chart of my cat temp at the track in June in Texas.

ZiG

Ah, very cool. Thanks. Steve, was this with the cat in your sig? Is that a high flow deal or what?

Nisaja

Mine is around 1050F when idling, and 1600F when flooring it. I have a gutted cat though.

Steve Dallas

That was with my OEM cat. Temps with no cat and with the HJS cat are very similar to what I was seeing with OEM.

Here is a chart showing temps with my BHR midpipe before I had the HJS welded in.

ZiG

Huh, very interesting. Thanks! Can't believe how hot these get, no wonder they say not to park on grass!

40w8

This is the first time I've found the real temps for our cats.

You might be interested to know they are almost exactly mine which is a 07 6speed auto GT with only 34k miles and BHR coils.

I had scanguage II in before coils and I think temps were about the same.

It reads 604 C mostly at idle anytime after warmed up which is 1119 Fahrenheit.

Highest temps I see driving hard up to 7k rpm is about yours of 1746 f or 952 C.

If we see a change we might conclude the CAT is dieing.

Nisaja

Seeing the same temps over here, except my CAT is gutted and I live in 95F weather.

40w8

Maybe this temp isn't exactly CAT temp, but I'm surprised you don't have CAT, and exhaust is still same temps.

So both panes of CAT are gutted?

Now what we need is for some RX8 owner with CAT going bad to give us his OBDII CAT temp to see if it's higher, and can be caught before overheating engine, too.

Nisaja

That is a good question. I'm not sure if both panes are gutted. The previous owner in Japan did it. I will drop the CAT and check.

I hear it's around 2000F with a clogged CAT.

ZiG

Careful how you're reading these, too. Since posting the OP I have realized that Torque or the car or the ODBII reader or some combination of the three, like to infer information and don't always get it right. There is no cat temp sensor in these cars and I am unsure if the O2 sensor is somehow reading the temp (internal sensor?).

What clued me in to this is when I was looking at available data channels and found 'intake manifold boost/vac'. It would read a slight vac at idle/cruise but as soon as I got on it, it was reading like 7psi of boost on a stock engine. Now I know the rotors have a slight supercharing effect etc but it's nowhere near 7 psi. Then I realized the engine has no MAP sensor and it was just guessing at these values, probably based on MAF reading and average VE for a piston engine or something like that.

Anyway, my point is I wouldn't trust the OBDII cat temp data. Measure it some other way IMO.

Steve Dallas

In case it isn't clear, one of the charts I posted above is with a factory cat, and one is with a catless BHR midipe. There is really no significant difference.

The EGT is measured by the O2 sensor. That is the major secondary function of an O2 sensor.

40w8

Thanks for info.

That's a serious EGT.

E.Murray

I gutted my cat last night and expected to see a drop in temps. But this morning on the highway, I was still at almost 1700F.
If this is an "inferred" thing (i.e. calculated from rear O2), it could be that my rear O2 isn't working properly since I'm getting P0037 and P0138. Is that possible?
1700 degrees just seems hot, even though I was (admittedly) accelerating pretty hard.

Loki

iTrader: (1)

1600-1700 is roughly normal for EGT around 14.7 AFR?
It is inferred from the O2, yes.

E.Murray

Yep, AFR was 14.6 - 14.7. Good deal.
It looks like I'm going to end up going with a VersaTuner in the next few days. I can lean out a bit, right? What AFR will I be shooting for (in equivalent conditions) and how much will that raise my EGT?
Thanks!

Loki

iTrader: (1)

I don't recommend tuning it just like that unless you're OK with shopping for a new engine :/

E.Murray

E.Murray

One more quick question. With no cat, the rear O2 sensor serves no useful purpose, correct?

Loki

iTrader: (1)

Correct. Except to tell the computer that the cat is missing.