Re-tune after catback upgrade?

[HamaTime™]

I'm getting the " I own the forum, I'm the best person to ask about exhausts because I engineered the ve exhaust system and I'm a real big ### wit" vibe off this bloke

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Ok if you want to get a professional opinion. PM Not_An_Abba_Fan who is a resident JC exhaust guru/professional.

http://forums.justcommodores.com.au/member.php?u=28347

PM him to see what he says about this subject.

 

[Diesel_junkie]

Hmmm... true.

Timmo666, feel free to PM me if you want me to clean ou this thread for you.

Apologies for getting it off track. I have a pet hate of people with no idea posting baseless comments.

Cheers.

Just clean it why do you need his request? You own the forum right? no wonder people say don't read forums and believe what you read cause its full of know all's like you. And you cant call me a know all because your no better.

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[Diesel_junkie]

Found it. Wasnt hard.

That's not the full quote.

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[Diesel_junkie]

And at no point have I said my system is better than any other system never have I said that.

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[timmo666]

Wow, i didnt expect this sort of response from my question lol.

however, my original question has been answered.
re tune after swapping the 2.5" for a 3"

required = no
beneficial = depends on what else has been done to the car.

in reference to what has been done to the car ill fill you in,

Manual VE SSV
Orssomm OTR
Hurricane 1" 7/8 4into 1 Extractors
200cpi Hi flow cats

currently 2.5inch perry/HM catback
looking at swapping to a VCM/KPM 3inch.

so my new question, just to clarify
with the other mods listed, do you think that a retune would be really that beneficial?

leaning towards just keeping the 2.5" the want for the 3" is mostly for the extra noise.

cheers,
Timmo

 

[Jesterarts]

Wow, i didnt expect this sort of response from my question lol.

however, my original question has been answered.
re tune after swapping the 2.5" for a 3"

required = no
beneficial = depends on what else has been done to the car.

in reference to what has been done to the car ill fill you in,

Manual VE SSV
Orssomm OTR
Hurricane 1" 7/8 4into 1 Extractors
200cpi Hi flow cats

currently 2.5inch perry/HM catback
looking at swapping to a VCM/KPM 3inch.

so my new question
with the other mods listed, do you think that a retune would be really that beneficial?

cheers,
Timmo

Nah, wouldn't worry about it. You could probably have whoever did the original tune touch it up a bit but really the gains would not justify the investment.

Wait till you slip a cam in or something, then get it retuned

 

[timmo666]

thanks for the advice, if i did go to a 3 inch, id probably be inclined to do the cam a bit down the track aswell.
probably gonna stick with the 2.5 inch for now.

thanks again,
Timmo

 

[PSI_KING]

Mate, there is no tune required by changing the diameter piping from 2.5" to 3".

If you were going to a less or more restrictive cat or a less or more restrictive set of headers/extractors, then a retune would be required.

Just to elaborate a little bit more, it is not just the overall pipe diameter that is a factor for the engine torque level and characteristics. You need to also take into account the exhaust muffler/resonator/hotdog setup and the type of pipe bending used.

Also the E38 ECU whilst operating in open loop reads from the o2 sensor, knock sensor, manifold absolute pressure sensor and mass air flow sensor (if applicable) to control spark advance and air/fuel ratio. It will compensate for minor changes in intake and exhaust and adjust accordingly to their maximum values. If a retune would be required, it would only be for the closed loop table and be in regards to cold start and fuel enrichment.

Regards,

PSI KING.

 

[Not_An_Abba_Fan]

At last someone giving correct information in regards to the ECU compensating and not "learning" or "re-learning". The ECU, whetner is has been tuned or not, has parameters built in to timing and fuel maps to reference under different operating conditions. It uses these references to compensate for the different driving conditions.

I am with the "no need to retune" camp. Unless you change the intake considerably, IE cam and head work, then don't touch the tune.

Even just fitting extractors, cats and an exhaust, the factory tune will still handle the changed dynamics. Built in emissions parameters are the only thing that needs changing as the change in exhaust changes the O2 levels in the exhaust flow to outside the limits set by the factory.

A tune changes performance only because the fuel and timing maps have been changed.

Exhaust flow and dynamics are a whole different kettle of fish and is not really relevant to this thread, but I will say that some of you have it right

 

[vxcp]

I dont think desiel has anything to say now