High flow cat...worth the cost?

ozz

ozz

New Member
Just wondering if a High flow cat is worth the cost or not?
Have had shocking economy for yonks now, got a new(ish) throttle body on the way & Got a working o2 sensor off brett on the weekend that i'm hoping will help a bit but i'm still running the stock(original) cat with headers & a 2" exhaust. A lot of my economy problem started around the time I had the cat back done so don't really know if it might help or not but am thinking it might be a restrictive piece of the system...for that matter I don't really know much about the cat itself & what a replacement will do either. Could it maybe help with fuel economy & is there any gains to be had by replacing it?
Sorry if this seems like a silly question but theres only one way to find out so cheers for any help/advice.
 
:lol: Exactly what I want to know....

With a high flow cat I think you should seem some mid-high end power increase, but more than likely you will sacrifice some of your lower end torque, so if anything I think around town (where you arent normally pushing the revs up too high to see that extra power) you would probably increase your fuel economy.

Have you also checked the condition of your plugs and leads? other thing that can increase fuel economy can be a blocked/old fuel filter...

Also the MAF sensor will play an important part in the air:fuel ratios, perhaps its dirty and not reading properly? You can get a MAF cleaner spray or use electronics cleaner, but I cant personally vouch for how safe it is to do...

Perhaps a 2" exhaust is simply too large for the 1.5L? 2L CJs come stock with a 2" exhaust.... (or is yours a 1.8L?)
 
Yeah have 15's on it but this fuel prob was there while the stock 14's were still on it.

Have replaced the plugs & leads & fuel filter & that did help a bit.
Also put back in the old stock air box & it made no diff at all, am now running a 3A racing pod filter & that did make a fair bit of difference & luckily mine doesn't have a MAF sensor so there's nothing to fiddle with there & yeah it's a 1.5.
Have been keeping a log of petrol & K's & it's running 12-15l/100k which is wayyyy too much, am getting up to 300k's to a tank if i'm lucky where it should be 4-500/tank.
I really don't know what the cause of the economy prob is or whether it's exhaust related or not cause this just developed somewhere around the time & had the cat back & pod done.
I'm also carring a bit of extra weight with sound deadener & audio gear but I don't think that it's the sole cause of this prob.
Thanks for your input guys
 
CJs are are 1.36T stock, then I have a Kicker L7 and a pack of dynamat in the car and I get around town on 8-9L/100km or absolutely floggin the guts out of it up say Mac Pass I get 12L/100km. Sure the CJ is a more efficient motor buts it's also got 50% more metal in it than a CE, so yeah those figures you're getting are whacked. I would have expected around the 7-8L/100km mark for a CE giving it the occassional hard pull off from the lights, etc.

Another thing to look at is trying a decent synthetic oil like a 15W-50 (I wouldn't go any thinner in a engine that old) that can increase mileage a little bit, but it wont be too dramatic.

If you've got no MAF you're gonna have a MAP sensor (manifold pressure) aren't you? (sorry I no very little of the 4G15)

It will be interesting to see what you get after changing the O2 sensor over, as really the MAP/MAF sensors and the O2 sensor are what plays the most important part in determining how much fuel the ECU injects. I don't think a pod or exhaust would be the root cause for such a massive drop in economy, they may just have co-incided with something in the car going kaput.

If the O2 sensor doesnt change things maybe try getting a compression test done and get the valve timing checked/adjusted. Failing that the only other things I can thing of is measuring the resistance of the wires going from the ECU to the MAP/O2 sensors to see if they have gone high resistance or maybe a cap inside the ECU has popped or something :?
 
knk said:
how does teh size of the wheels make a difference on whether its worth it or not?
Click to expand...

i think what myles meant was if ozz has big wheels that will make the fuel consumption worse & belive me it does with 18's on my old lancer the fuel consumption was terrible i struggled to get 300k's to a tank :? gone are those days thank f*ck lol
 
Has nothing to do with size of the rim, it's the weight (and weight distribution) of the rim and rolling resistance of and whether its the right sized tyre. Cheap *poo* rims (aka Tempe Tyre specials) weigh a heap, but I had 19s on my CJ and noticed no difference in fuel economy, it was less responsive though due to the higher inertia in the wheels. Rims I don't believe increase fuel economy by over 50% alone.

Nonetheless rims are near insignificant to a question on high flow cats... :?
 
Before spending money on adding to your current setup, maybe trace your steps backwards to find where the problem lies and then go from there to rectify it. No point throwing money at the problem when you don't know what the problem is.

Revert back to the stock exhaust if you kept it. If not, maybe see if anyone else with a CE has one lying around who has upgraded.
 
Well after talking to a couple of exhaust joints this morning it looks like it would just be a waste of $$$. From what they said, if my cat was stuffed I wouldn't be getting any revs & it would be bogging down badly. As it is if I want to give it a flogging, can do easy 5-6k revs so that pretty much knock out a cat problem from what they were telling me.
Thanks guys for your help anyhow.
 
knk said:
how does teh size of the wheels make a difference on whether its worth it or not?
Click to expand...

Larger wheels = larger rotational intertia = crappy fuel economy I.E using more power to turn the wheels, and as we all know air/fuel = power so your using more fuel.
:roll:
 
iv got a 2inch exhaust from the catback. i have a cannon though.

my fuel economy is terrible. 300-400ks a tank. i use 1 maybe 2/12th's of a tank PER DAY going to n from work. i fill up 1.5times a week.
 
i get an easy 500+kms a week from my tank and thats with alot of thrashing, 17" rims, poddy, oversized TB and stock zuast

if ur intake sucks hot air it'll chew more fuel as i found b4 i went cai, rims use a lil more petrol but i didnt notice more than 10km's a tank less wen i went to 17's from stock 14's
i gues stock zaust must keep my fuel consuption in the good zone :D
 
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