Heat wrap on cat convertor?

On my 2003 Prius Sedan I have a aftermarket cat system that does not have the HCVC contraption on it.

Everything has been working fine and code free in relation to that so far.
Until cold winter temps have hit.

DTC p1436 popped up while driving after the car had warmed up.

Since the gasses can no longer recirculate, and I believe that since the cat is cooling down when the gas engine doesn't run, that in this 18f temps on wet snowy road, I was wondering if exhaust heat wrap on the convertor might help prevent this?

Any ideas?

 

Sam. I hear and understand what you are saying and, to a point, you are correct.
However, I have been using this trick for some time now and have no signs of any such problems. I do, and I recommend, header heat wrap of at least 1400F temperature range be purchased and used.

I should also add that a 2" x 15' roll of 1400F heat wrap only covers about 2/3s of the first Cat, so the excessive heat still has some free opening to dissipate, but it allows that Cat to preheat just enough for the O2 sensor to sense that the catalyst is working properly.

Now, I am only using this trick for very cold winter driving since it is only in that kind of climate that code p0421 pops up (never happens in spring/summer/fall), and it goes away with this trick. When hot summer driving conditions come I might remove the wrap if catalyst overheating seems to be arising.

But up here in NH I really don't believe that such troubles will come up. So unless I go cross-country through the hot summertime south or southwest desert (or excessively hot rod or excessively cruise hard at upper illegal speeds) I don't believe that the heat wrap characteristics will be a problem.

At the same time, your points are good, and it's good for people to give it some consideration and think about what kind of "hot" driving conditions or driving style is typical for them.

Also, whenever any "non-typical" modification is ever made the driver should (as I do) monitor the modification for issues, especially safety issues.

In the case of my experience with using the heat wrap, I have experience and observed nothing more than a slight hot fabric kind of smell when I made my first drive with it. Since then, there has been no sign of excessive heat issues.

 

Hi Larry. I did solve the emissions/inspection issue.

It did involve installing a very inexpensive vacuum advance cannister on the vacuum line (bought an '84 ford escort advance vacuum cannister from ebay really cheap).
It fixed all the Catalyst, O2, and Evap codes that I was getting. However now, with cold winter temps, code p0421 popped up during cold startup and in the first cold 5 miles driven.

It is due to the missing HCVC valve also, due to a cold Cat warmup.

I found that, for me, wrapping the cat in a layer of 1400F header heat wrap solved this issue.

Now my 2003 Gen1 runs fantastically, like a new car, and with absolutely no codes.

 

Over 2 years now with the heat wrap on the pipe front of the cat and partially on the cat, and with the vacuum pot installed in the HCAC vacuum line.
It has made a huge difference in cold starts and warmup, and in cold weather driving, and gives no troubles over the summer months and on long interstate drives.
There has also been a noticeable improvement in the average MPG during the cold weather months up here in northern NH.
Not only did this help to trick the diagnostics system from giving me DTCs in regard to the missing HCAC on my aftermarket cats, but it has actually caused good efficient readings in the catalyst and O2 systems.