Fitted a pair of RT cats last night.
Besides suspension mods, my car is stock. I thought it would be interesting to first fit the cats and see the results before any other mods are done .
This should also give other owners an idea as to whether its a worth while mod.

No issues with fit they are made really well. A little smelly for the first couple of hours till they burn in a little.
There is definitely a noticeable gain in this mod. Accelaration has improved and it pulls alot harder after 4000rpm. Thats mostly where the gains seem to be.
No doubt in my mind its quicker than stock

I decided it was best to dyno and see if the A/F changes at all. You can see my stock results below. (5th gear)
This Friday I have another dyno booked to compare any changes.

Q. Is the A/F measurment from the exhaust accurate enough?

 

Inside the Rt cats .......

 

Nice work!

Do you have the raspy noise at WOT during some rpm levels?

And you have no other exhaust mods?

(I think these cats combined with Y-Pipe plus stock US muffler(theory) would make good gains for low cost with little noise. 8hp + 5hp + ~10hp = 23hp@wheels)

Cant wait for the dyno!

 

I did notice a very slight raspy sound. Nothing annoying tho.
No other exhaust mods at all.
The sound hasn't changed much, just a little deeper.

 

Nothing annoying tho.

Thats good news.

How many KMs did you have when you did that dyno?

 

11,500 km

25deg C

Optimax

 

Looking forward to the after dyno.

 

Here are my results.....

 

Nice little gain considering the rest of the exhuast is stock but look at that AFR.

 

Not chasing power so 6 kw was expected.
I was told that its still in a "good" range and not lean enough to worry about. Can anyone confirm otherwise?

 

I think the AFR is OK but I'd keep an eye on it if you plan any further mods. Your base AFR has more range than most I've seen anyway which may explain a lot of it. Mine is basically 12.5 throughout the entire range for example.

 

Can someone explain me what is "raspy" sounds like?

So what if i add the R/T cats with Hi-tech exhaust. Would my AFR lowered as well?

 

apsilon - I see your point about the A/F ratio after looking at the others in the dyno list you compiled.
They seem very linear compared to mine.

ypwpat - I'd say that yes your AFR would get a little leaner, but your gains would be more than just 6kw (in theory)

Raspy is kind of a light metalic rattle sound.

 

I wouldn't be too worried. It's probably a result of that particular dyno and/or the way they fitted the sniffer. Perhaps pull a couple of the spark plugs after you've got a few more km on the cats and see if they look OK just to be on the safe side.

Did you reset the ECU after fitting the cats? How many km on them so far?

 

I've never reset my ECU. Often wondered if there is a benefit at all.
Only clocked up around 200 km so far with the cats.
I'm not an expert on the subject of AFR so all opinions are welcome.
Thats pretty much why I dyno'd before and after.
Has anyone found a change in AFR after fitting a cat back system like HiTech or the Amuse ? (next mod)

 

I Don't know, but don't you think it's a Good idea to Install a APEXi S-AFC II? with your RT cats?

 

yeah... with the s-afcII, you can be able to balance the AFR. i once spoke to Peter about that and he said that's workable too. I think I will go for the s-afcII if I have the cats installed.

btw, thank you for all the info, that is really helpful to me in the near future!

cheers,

richie

 

FWIW mine barely changed with the Amuse. You can see the AFR on the second chart here: https://my350z.com/forum/showthread....threadid=41671

I should be dynoing next weekend and will check the AFR again. Nothing has changed on my car since the last dyno except about another 5000km and the US duct which should be insignificant. Should also have an answer as to why the results have changed at Croydon.

 

What is the lowest AFR to be consider your car running lean?

 

Someone correct me if I get this wrong. I tend to get AFRs backwards sometimes.

It really varies depending on rpm and load (and probably between types of engines). At idle 14.7 is generally considered to be around ideal but you don't want that at peak revs. You'd like it to come down to about 12.5 under WOT.

Flashers' graph is interesting because it starts out so lean and becomes overly rich compared to the other 350Z charts I've looked at (not that I've looked at that many). If you look at my AFR chart for example it starts off about 13 and comes down to about 12 which is a fairly flat chart.