snobdds

No, not exhaust size...eliminating the converter all together. I thought I was pretty clear.

jalopytech

Just remember, you learned it here first and its the internet so its gotta be true!!

j2the-e

So, no cat converter = valves not closing all the way? I still don't understand. You mean like the valves are floating? I think it would take 10k rpm for that to happen. Not going to see 10k by eliminating the cat

snobdds

Yes. The valves float...and not anywhere near the 10K rpm mark. It's more like anything off idle. 22re's need a certain amount of back pressure to keep them closed. If not then your burning up your valves.

Now, larger valve springs help with this...but were talking stock here. So yes, no cat means the valves float and after a while you burn up the exhaust valves...

j2the-e

Huh? I guess the laws of physics do not apply to the magical 22r. Guess I got really lucky then.... My 87 had no cat for 2 years and I beat the heck out of it. Had it another 50k after I fixed it and never a problem.
I think that's an old wive's tale. And I think it goes more like if you run an open header, the valve face can burn. Something about the valves cooling off too quickly after you shut the engine off. At least that's what I have heard. Never actually seen it though. But its got nothing to do with the valves not closing all the way. The springs close the valves regardless of "back pressure." Now valves can float when the rpms are so high that the valve springs do not close the valves fast enough. You were right about one thing though, stiffer springs can help. As well as lighter weight keepers and rockers. But again, nothing to do with back pressure. And not ever going to happen on a stock rpm 22r

jalopytech

I'd like to interject and possibly rectify the statements made, you are confusing the valve in the EGR with the valves in the head. The EGR returns a measured amount of exhaust gas to the combustion chamber. The purpose of this is to cool the combustion flame and prevent NOX (Smog). The same thing high octane gas used to do back when it had lead in it. Something to think about the next time those of you that have do the sniff test, fill up with higher octane fuel and pump it thru your system before you go in. The EGR must occur at specific times to incur the least detriment to engine performance (so they want you to believe), EGR is, therefore applied to an engine at normal operating temperature at off idle conditions. This is why, when a EGR fails (EGR valve burns or sticks open do to carbon) the engine will not idle or idles badly. Cat defects on the other hand appear in two ways they can clog or overheat and are usually the result of other engine defects Clogging can be checked with a backpressure measurement. Maximum allowable restriction on most engines is 1PSI or less at full rated speed. The converter is a chemical reaction and that chemical reaction gives off heat, as an engine defect increases the converter will work harder and give off more heat. oil getting into the system and intake vacuum leaks are the most common cause of Cat failures.

dawa88

Wow, thanks for all the input!

As per usual though, any issue with this truck is never simple or cheap. Took it into the shop and they spent a couple hours trying to set the timing, but could not. They managed to get it into base timing mode, but no further. So looks like the previous owner on top of all the other issues didnt instal the timing chain correctly... ˟˟˟˟ing lemons are expensive! Anyways, once timing is tuned, then its onto everything else.

thefishguy77

iTrader: (1)

When I got my 93 w/22re. I had to do a new cat back to pass smog. I went 2 1/4 and was very happy with the power gains. After reading what I have read here I am excited to put my 83 afm on that just shipped for Xlaxx here. I say he posted it for sale and I jumped all over that one. Now all I have to do is the plenum and have it blared out a little and I eliminate all the easy choke points. Sorry off topic a little but good info inspires thanks again.

jalopytech

What? I thunk the magical, mystery 22r book was about physics law, now I'm finding out its luck. Hmmm!

dawa88

Alright, just had two guys look at it, first guy said the timing chain was ˟˟˟˟ed and needed replacing hence why the timing cant be set accurately. Second mechanic said the timing was set fine and the reason for my poor fuel economy is my exhaust system.

I knew I had an aftermarket exhaust with no cat in it obviously, but I didnt realize it had a header as well. Ive now been told that because this modification can cause havoc with the O2 sensor and will throw on the check engine light that there is a riser beneath the o2 sensor which pulls it out of the flow and stops the engine light from coming on, but also prevents the 02 sensor from functioning properly. His suggestion is that my economy isnt actually that bad and I shouldnt worry about it, but if I really wanted to try I could put on the stock header and exhaust and go from there. Thoughts?

jalopytech

Pick up a weld-in o2 sensor bung, have it welded in and replace the sensor.

dawa88

will that drop the 02 sensor into the flow?

jalopytech

That's what they are for, any auto parts store or muffler shop should have them. Install it were the original was.

dawa88

ok awesome Ill look into that. There was some concern that the o2 sensor may not work as normal given the aftermarket exhaust, does that make sense?

to me the o2 sensor should measure the gas/oxygen concentration independant of the system, hence why a universal sensor functions on varying systems. But as I said, not super knowledgable about this stuff.

jalopytech

If I were in your situation, I would also disconnect the battery overnight and let the ECM relearn the new fuel parameters (cold start), instead of plug and play.

dawa88

Ive definitely done that since Ive owned the car, so after the exhaust was installed, but Ill try that again tonight. Ill hopefully get it in early next week to get the bung/new o2 sensor next week and ill make sure I reset the ECM then as well.

highonpottery

iTrader: (1)

what brand o2 sensor is in there? these trucks really only like stock replacements - so get a Denso because that could be the issue as well regarding check light. since exhaust pipe is somewhat pressurized, i'd think the sensor would still be able to read correctly the way you have it set up. regardless, you could still replace the bung with the correct depth if it's truly the issue. btw, where is you sensor at? do you have 1 or 2? mine has 2 - one just before the CAT and the other just after.

dawa88

Well I was underneath the truck last night installing my tcase ebrake and noticed that the previous owner had literally twist and tape installed the previous o2 sesnsor, obviously it no longer is even connected. Also its isnt sealed correctly so that wont help with the pressurization. And given all this the sensor is also a bosch... I only have 1 o2 sensor in but no cat.

highonpottery

iTrader: (1)

Sounds like you found your problem. Look up Bosch o2 sensors here on YT and you'll see several complaints and problems with them. Denso is what you want - just bought some on amazon for less than $60/ea.
wiring install should only be a plastic clip connection, no splicing involved unless someone clipped the pigtail from your wiring harness.

dawa88

yeah I wish it was that simple, pigtail was most definitely clipped. Ill look into picking a denso up. Any chance you could send me a link for the amazon page, so I dont get the wrong part number?

Just wanting to confirm, whats everyone thoughts on the functionality of an o2 sensor in an aftermarket exhaust (my opinion is it should still work well enough)? Also do we think the riser beneath the o2 sensor needs to be removed to drop the sensor down, or will a pressurized system (even though i have no cat) be enough to allow for functionality?