Theoretically, the honeycomb is a better cat then the pellet system, as the exhaust passes through the honeycomb which exposes more surface area to the exhaust. Exhaust gas only passes over the pellet style. At any rate, even the new GM's now have the honeycomb style. More efficient in a smaller size. The manufactures like to put multi cats on everything these days, and I wonder if that's even necessary.
Question about Magnaflow High Flow cat on otherwise stock truck
- Thread starter sneakingfart
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
The pellet-style converter is so restrictive because the exhaust is forced "through" the pellet bed--around the perimeter of the individual pellets.
You learn something everyday! This whole time I though they simply went over the top of a bed of pellets, Ha! Here is a pic/diag:
You must be registered for see images attach
Pellet converters are crazy restrictive compared to honeycomb converters, and they also use a crapload more rare metals. If you're scrapping out an older vehicle the pellet converter will get you a whole lot more money than a later honeycomb.
The only downside I can imagine to replacing a pellet converter with a honeycomb, is that the EGR valve on TBI trucks (and others) is backpressure-sensitive. Screw with the back pressure in the exhaust system, you'd potentially screw with the EGR tuning. The TBI EGR valve is a "Negative backpressure" device. Some are "Positive backpressure" valves. And there's the original non-backpressure sensing style.
I believe the electronics-controlled solenoid EGR valves did away with all that, but I haven't studied them.
Is this actually important in real life? I didn't notice any problems on my '88 when the pellet converter went away in favor of a honeycomb style, and Flowmaster "cat-back" exhaust system.
I believe the electronics-controlled solenoid EGR valves did away with all that, but I haven't studied them.
Is this actually important in real life? I didn't notice any problems on my '88 when the pellet converter went away in favor of a honeycomb style, and Flowmaster "cat-back" exhaust system.
L31MaxExpress
I'm Awesome
I put a TBI 350 in my G20 van that had an OEM catless dual exhaust that I had added headers to already. EGR seemed to work as it was meant to work. On the other hand I added headers, Y-pipe, high flow cat and a magnaflow to a 90 RS with a 305 TBI and it threw an EGR code nearly every drive as well as spark knocked at part-throttle. I put a truck/van valve on it and it quit throwing codes and the pinging went away. So YMMV.
The switch would have been in the late '80s or early '90s. Your Suburban has a honeycomb catalyst. I don't know if early GMT400s had pellets because both my trucks had them cut off by previous owners.
Thanks. And, just as I was reading your reply - I remembered seeing the honeycomb when I changed the exhaust (cat back) last month!
