Aftermarket exhausts/fuel economy

[doommachine]

Hey,
My dad always complains about the fuel economy in his HSGR. It is pretty crap, mine is manual and has more power and he still gets worse economy.

So.. my way of thinking about it was that the stock exhaust is a big restriction and doesn't help at all with the fuel economy. Would this be a fair call?

Does anyone have an exhaust in their RVR and can comment as to the difference it made?

 

[Jonson]

No, not really a fair call. Remember, the exhaust is only going to flow as much as the engine is exhausting. Engineers spend hours and hours doing R&D to create an exhaust that is well flowing, creates enough back pressure, passes Db testing and of course is the right amount in bulk. I would be looking to other options like Air filter, oxygen sensor, spark plugs, timing....

 

[Rockabilly]

The rear muffler is the most restriction in the RVR exhaust. Your Dad mightn't like a whole exh job. As above, it isn't gonna make much diff in ecconomy.
If you manualy select 2nd in an auto for speed humps, corners etc, you only need a light pedal (throttle pos sensor swing) to accell.
Pushing the pedal in Drive to get the box to change back to 2nd is a lot more throttle pos than you use in your manual car.
Less pedal = less fuel in manuals & autos, but yeah, autos are thirsty as a rule if just left in Drive.
Cheers !

 

[D3bb4]

Exhaust design is easy maths... then tune for specific power band... then db testing; make a straight through muffler which is fat on sides, so exhaust gas pulses have to travel through more material/suppresses noise better. easy

Choking a car is gonna put more load on the engine and reduce performance and economy. Putting an excessively large exhaust will do the same thing though. Anything after the turbo won't make as much of a difference as it would in an NA car, so a 2.5-3" system will be sweet.

Does he have extra weight? normal servicing thigns like jon said? is the engine more worn? same oil? same tune/computer?

 

[JayRome]

does he have a heavy foot????

 

[MattL]

My Auto gives me 380km/45L and sometimes worse.

I'm running a 3" Turbo back.

I dislike it as much as you do, but Rockabilly is right, the Auto's are pain to down shift at times...

 

[mattrat]

380 off 45, isnt bad at all for a turbo car?
use dreaming, thats like a 11.5 per 100 which is pretty damn good dude for an old car

 

[Astron Boy]

Try having only 300k/tank

 

[bazeng]

You probably just need a slight tune.

Most cars from the factory run rich anyway (safety).

Driving style / tune / condition of the engine play a big part of the economy.
So does weight.

 

[syco_rvr]

make a straight through muffler which is fat on sides, so exhaust gas pulses have to travel through more material/suppresses noise better. easy

when you say fat on sides do you just mean a thick sidewall pipe??

as i have run a 2.5 straight through and thinking of moving up to 3 as is very noisy,

would i be right in saying that with the bigger 3inch there is more room for the same amount of gases to escape therefore less pressure and less noise??

 

[MattL]

My old RVR used to get the same economy with a softer driving style, so in many ways I feel good.

However I've seen other RVR's do 9L/100 with hard driving... so it bugs me from time to time!