New exhaust, need to retune?

[betts]

My stroker has been tuned my Alan Gibbs with his kalmaker software, and I have just put a new better flowing exhaust on. Do I need him to re-tune it to get the best out of the new setup?

Cheers

 

[Not_An_Abba_Fan]

Ideally yes, but it depends on what he did with the tune to start with, whether or not he allowed for future upgrades.

 

[spirto]

It's all about back-pressure, if you've upgraded from 2inch to 3 inch exhaust, then the TUNE, won't be effected.

 

[Not_An_Abba_Fan]

It's got **** all to do with back pressure. People and their obsession with back pressure.

If the tuner has tuned it to suit a better flowing exhaust, you won't get the full benefit of the tune until you put the better exhaust on. It's got more to do with AFR's and fuel delivery than back pressure.

 

[greenfoam]

It wont have changed the ratios much and I'm sure he added a bit of fuel for safety and future small changes anyway, So I'd say it will be fine

 

[betts]

I went from a twin 2.5 going into a single 2.5, to a single 3. The car has problems with pinging anyway so I might upgrade the fuel pump while I'm at it and then get it tuned to see if it fixes the problem.

 

[Not_An_Abba_Fan]

So you downgraded the exhaust then? A twin 2 1/2" will out flow a single 2 1/2" unless it had really restrictive mufflers.

 

[QldKev]

Reading it; I think he went from a
Twin 2.5 into Single 2.5 exhaust system
to a 3 inch system
So that would be about a 40% improvement in potential flow; allowing same style of mufflers etc. Not sure why with a stroker 355ci you would even go a single 3inch. Still waay too restrictive. Even the stock LS1 exhaust is 2 x 2.25inch


QldKev

 

[Not_An_Abba_Fan]

I read it wrong....

A 3" will outflow the original, but I would recommend a twin 2 1/2" on a stroker.

 

[spirto]

Each to their own re: Backpressure. As greenfoam said, they would have added a bit to the fuel mixture to enable future mods, if it's pinging then it sounds like a timing issue, it sounds like it will need a re-curve of the ignition. One of my car runs a 3 inch and doesn't ping, the other has twin 2.5 inch and pings, if I swapped exhausts would make no difference, on mine it's the ignition curve, as I upgraded the cam, now the computer isn't following it, making it lean top end, rich bottom end. Best of luck.