RB30S, Tune after extractors?

[Throbbinhood]

I've got a set of extractors and a 2.5" exhaust I'm thinking of strapping on the old girl - an rb30 carby motor with the heater/base plate mod.

Just wondering if afterwards the carby will need to be retuned? Do these carb's run rich from factory?

She runs mint at the moment, no misses, no issues with going up hill, and 16-18L/100km on 35's.

Also, will having extractors increase fuel economy?

Thanks in advance

[nicksamaniac]

In my experience, that setup will see a slight increase in mid range and top end power, (realistically about 5-8hp) little to no difference in economy, you will probably see a gain in economy if you do alot of hwy driving, as in sitting in the mid power band (2500-3000rpm) this where the system will start working and showing its worth.
but bush and town/city you wont see much difference.

[nicksamaniac]

Also, I doubt it would need a tune with just an exhaust, the slight increase in ve the carb will/should have enough headroom with the stock jetting.

[Throbbinhood]

Awesome, thanks mate!

Is there any way to tell if it's running too lean or anything? Will it backfire or something? Just don't want to damage anything :)

[nicksamaniac]

Only way to be 100% is with a wide band o2 sensor, a simple dyno run can check this.
most shops with a dyno will charge about $75 and take about half hr to do.
its the hands down best way, plus you get to find out how much power and torque it makes!
but from a back yard mechanic old skool way, check your plugs.
if its not getting hot and your plugs are consistently a nice dark greyish clean color, your pretty good.
if they are white and burnt tips its lean, if they're dark sooty color its too rich.
(Very rough guide there, Google will explain that better )

[Throbbinhood]

Thanks nicksamaniac. Might get it thrown on the dyno after I put it on, wont be for a while anyway!