333pg333

Getting an exhaust made up with a removable Cat and just wondering on how much difference it will make to the tune re the a/f's and egts and anything else you can think of?? What do we need to look out for here?
thx

TRP951

dont you have the vitesse MAF kit?

333pg333

This is on another build.

333pg333

Nobody with anything??

Rock

I cant say much, but my car certainly did run better after we deleted the cat.

If you think about it though, I think the exhaust temps would be lower because there is nothing blocking the exhaust or insulating it of any sort.

If the engine is cooler, then the A/F might be a little bit richer becasue of the car running cooler!


That might be a far stupid guess but hey, its worth something.

Fishey

EGT's is always lower without.

333pg333

What about a/f's? Surely someone has done this before and datalogged?

Keithr726

When I deleted my cat I noticed lower EGTs. A cat is a high flow burning filter that is restrictive. Restricted air is hot air. Your AFRs should show rich I'm pretty sure.

333pg333

Ok so we think it should show lower EGTs and run richer depending on the size and quality of the Cat I guess?

Geneqco

I can understand egt's being lower without the cat, assuming that improves flow and assuming afr's stay the same... but I cannot quite understand how you would be richer without the cat.

With the improved airflow, i would expect that your afr's would either remain unchanged or be leaner, depending on what system was being used... ie, for a system that truly measures air mass, I'd expect afr's to remain unchanged.

If the mixture is leaner, I'd expect that egt's would be affected by the interplay between the leaner burn and the freer flow.

goldminer

Whose exhaust are you using and how much are you paying (if you don't mind me asking)? It's looking like I'll be getting one in from the USA rather than have one made locally due to cost.

333pg333

At this stage I'm looking to SFR for the exhaust. Not sure on costs yet. Contact Tim or check out the site. Plenty of options.

lleroyb

Give me a couple of weeks, next Sat. I am changing to a cat-less system and shortly thereafter going back to the dyno.

Results will be posted for true and for certain.

I might install Nize's used water pump too.

Lou

evil 944t

What if the used WP makes the motor run cooler than normal? Maybe that will effect the A/F's? How can this be a true and certain dyno run when you pulling out all the stops, like Nize;s used water pump. Its not fair, its just not fair...

Geneqco

On a more serious note... you'd expect some difference if comparing to a 19 year old used cat. A hew high flow metal cat with your HP, you would hope for not much difference... however, as you went up the HP scale, you'd expect that to change a bit.

As for all this picking on Nize... I think you should watch this and substitute Nize for Britney:

http://www.youtube.com/watch?v=LWSjUe0FyxQ