highflow cat and egr problems

[DDCxj]

I dont know if this is in the right forum so feel free to move it if it isn't. I have a 91 XJ with a 4.0 in desperate need of a new cat and muffler. I was wandering how many people have had problems with their EGR Valve due to a high-flow cat as opposed to something more close to stock.

thanks
dean

 

[Heep]

How would your cat affect your EGR valve? Ive never heard of anyone having a problem like that.

 

[rsalemi]

And considering a 91 is a HO and doesn't have an EGR valve it shouldn't be a problem.

 

[DDCxj]

Thats my fault, sorry. I have heard of people using highflow cats and having to replace egr valves all the time because of it for some reason and I was naware that 4.0's did not have them, I guess thats why I havent had that problem yet.

thanks
dean

 

[Heep]

4.0's have them but its just 87-90 Renix 4.0's

 

[5-90]

It is possible that a high-flow cat will cause EGR volume to drop off slightly, but the EGR is as much "push" from exhaust pressure as it is "pull" from the slight intake vacuum. Either way, it's a minimal effect, and I've not run across it actually causing a problem (but there may be a small increase in throttle response or power from the less polluted fuel mix.)

As already mentioned, tho, you don't have an EGR to worry about - ChryCo modified the cam grind for the 1991MY to accomplish much the same thing while doing away with a failure-prone emissions subsystem and potential for vacuum leaks in several locations, giving credence to my stating often that the damn thing just isn't, strictly speaking, necessary...

5-90

 

[crjeeper]

I dont know if this is in the right forum so feel free to move it if it isn't. I have a 91 XJ with a 4.0 in desperate need of a new cat and muffler. I was wandering how many people have had problems with their EGR Valve due to a high-flow cat as opposed to something more close to stock.

thanks
dean

Maybe a thread hijack, sorry if it is...I just put a Magnaflow hi-flow cat and Magnaflow muffler on, very very happy. Noticable difference in performance , sounds fine, not too loud. Passed smog last week no problems and no EGR issues.