It's About Time!

[TigerDan]

Interesting you should mention that, as it's something I'm working on. I just wanted to get the new engine in first with everything still pretty much the same to get a baseline.I'll drive it like this for a while and take a little more time to work out a few details, but I've got it mostly figured out how I want to do it.

[DHappel]

Keep us posted.  I have a few various intakes sitting around that might just come in handy after all.  

 

I feel like my 4.6 is strangled at higher revs and load.  The exhaust sounds very 'weezy' with a 'rushing' sort of noise when pulling up a hill over 3000 rpm, so I suspect that the cats may be partially clogged or perhaps even the muffler, though it's a flowmaster so I don't really expect it to be a restriction.

[TigerDan]

I've had plugged cats make a whooshing sound at higher revs like you describe (not on a Rover, but on other vehicles) accompanied by loss of power, so you might be on the right track. And no, I wouldn't expect a Flowmaster to become plugged like that.

[TigerDan]

UPDATE:

 

Still running great, in fact, it's now even better than when I first got it going. I had needed to bump up to mid-grade gas with my timing set back to 8º which I figured was due to the increase in compression with the new engine. Even so, it would still ping on hard acceleration and I felt it didn't have quite as much power as I'd expected. And fuel consumption was turning out to be about the same as I'd been getting with the old engine.

 

Back in October I began to notice a rattling sound from underneath at low RPM, in fact, I was on my way to play a gig at the Winchester Mystery House when I first noticed it after I got off the freeway in San Jose. Sounded like tranny or transfer case, bit I checked it out and it was actually coming from one of the Cats. I had heard this once before, a couple years previously but then it stopped and I pretty much forgot about it. I figured that the broken-up cat substrate had all blown out the exhaust by now. But this time the rattling didn't go away, and it seemed to be a little down on power. I pulled the Y-pipe and swapped in another one I had with larger aftermarket cats, and what a difference! The power is now up to where I felt it should be, and I've been able to go back to regular gas with only the slightest pinging on heavy acceleration. And the mileage has come up by 1-2 MPG on average.

 

So that bad cat was partly plugged and restricting the exhaust, causing several interesting symptoms. 

 

Of course, now my heater core has gone out, just in time for winter!

[GraemeWare]

Dan,

 

My exhaust guy was surprised that my cats were apparently hollow ....

 

Graeme

[DHappel]

Dan,

 

My exhaust guy was surprised that my cats were apparently hollow ....

 

Graeme

You should complain about that to somebody.  Clearly you've been short-changed!

[astateofmike]

Yeah, hollow better than plugged.

[TigerDan]

I actually thought my old ones were hollow. I had to replace them when I bought the truck in '06 in order to pass smog, because the originals were hollow. I just installed cheap aftermarket Magnaflow cats, I think they were less than 30 bucks each new. On the the first Shaver Lake trip they got really hot climbing the hill up to Shaver, and they got pretty warm a few times on other Sierra trips when making the climb out of the Valley. After that they stopped getting warm, so I pretty much figured they had melted down and blown out.