100 series petrol- Fuel saving advice

Submitted: Tuesday, May 02, 2006 at 20:07
ThreadID: 33469 Views:2248 Replies:9 FollowUps:3
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G'day All,
I am considering extractors and a 2.5inch exhaust for my 100 series petrol, I have been told that it helps with fuel economy.

If any of you can inform me if this is somewhat correct and have had a 100 series with this exhaust fitted I would be keen to know your toughts.

Any other feul saving tips would be apprecitaed, please no smart comments just facts would be nice.

For your help I will tow you out of a bog one day.........

Take care
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Reply By: Exploder - Tuesday, May 02, 2006 at 20:23

Tuesday, May 02, 2006 at 20:23
How much fuel are you expecting to save with them, I don’t think it would be anything to jump up and down over remembering they were designed to increases Pro-Formance and not economy.

When doing this stuff it isn’t just a matter of exhaust and extractors, you need a set of tuned length extractors for you Stock engine, exhaust size is good, a Hi-flow Cat centre straight throe muffler and resonator is probably the way to go, you will see gains in engine Pro-Formance but how much better consumption i don't know

I am no exhaust Expert and nether are half the guy’s in the shops probably, but it’s fairly complex stuff to make a good exhaust system for an engine.
AnswerID: 170292

Follow Up By: Brendan14 - Tuesday, May 02, 2006 at 20:29

Tuesday, May 02, 2006 at 20:29
thanks for your reply, I know its pretty hard to get a definative answer.
I had a 2.5 on my Pajero and that made no friggin difference to economy, just sounded nice.

I'd rather not hear it from a salesman at the exhaust joint, he just wants a sale.
I'm more interested in hearing it from people that have them fitted.

FollowupID: 425678

Reply By: V8Diesel - Tuesday, May 02, 2006 at 21:41

Tuesday, May 02, 2006 at 21:41
Don't think they're that bad from the factory if it's the 4.5 your talking about. The only bit that would concern is the bend over the rear axle housing which is flattened from the factory.

Don't know about the V8.
AnswerID: 170307

Reply By: Off-track - Tuesday, May 02, 2006 at 22:47

Tuesday, May 02, 2006 at 22:47
That flattened bit is there to increase torque which in itself should provide better economy.
AnswerID: 170325

Reply By: Robin - Tuesday, May 02, 2006 at 22:51

Tuesday, May 02, 2006 at 22:51
Hi Brendan

Thanks for the offer of a tow out of a bog , but I'm afraid I drive a petrol Nissan and hence am unlikely to require assitance - but perhaps I can be of help to you one day.

As for the 2.5 in exhaust it is unlikely to provide you any fuel savings and is more likely to cause an increased use of fuel.
This should not be confused with the fact that 2.5 will provide more power at high rev's and under load in which the volumne of gas expelled is much greater than cruising and hence pipe size can be more relevant if done correctly.

To provide better fuel economy (I assume your cruising) you need to optimize the torque at the cruising rev's maybe around 2500 rpm and not at 5000 rpm.

Depending on engine design it is often appropriate to in fact fit a smaller/longer exhaust/inlet to ensure torque efficentcy occurs around cruising speed.
My Patrol does this via a vaccum operated flap but it still drinks a lot.
In some other fields like long haul diesels, such smaller pipes are available as aftermarket acessories as opposed to larger exhaust which tend to deliver power.

Cat convertors are these days also designed to offer little real resistance to flow.

Leaving out driving styles the best thing to do is to first run high tyre pressures and minimze rolling resistance. I do this by running narrower road tyres unless 4wheeling , not having bull bars , roof racks etc.

For a more technical walk in walk out solution a unichip is the way to go as it is programmed individually to optimize timing and fuel delivery on your specific vehicle.

Don't know your specific car, but in the petrol patrols its easy to drop the voltage out of the cars MAF sensor with a couple of resistors by about 5% which causes the car to think it has less air and hence delivers less fuel. Works well but has its dangers and not reccomended if your not technically into playing around yourself as it leans out the mixture and can cause stalling and do nasty things to your engine if you get it wrong.

Robin Miller

AnswerID: 170329

Reply By: OMN - Wednesday, May 03, 2006 at 10:31

Wednesday, May 03, 2006 at 10:31

Don't kow whether you ahve the 4.7V8 or the 6 cylinder petrol version so the follwign form my car may or may not berelevant.

I drive the 4.7V8 and have had both the exhaust modifed from the engine all the way back so include HFC headers or extractors or whatever. As you can a salesmens dream come true.

I also had a Uni Chip put in at the same time so can't separate out the two.

As for fuel economy, pardon what was that, seriously around town in Melbourne pretty much lineball the same as i probably tend to take off from the lights a bit quicker and drive it a bit harder because it jsut goes better.

On trips away on the highway definitely an improvement but nothign i would write home about, margianl at best.

Downside i have it tuned to run 98 Octane but get further than i did with the standard so it balances out the same in tems of dollar sepnt.

Where i have had a real improvemtn is on engine braking down hill offraod due to the increased power, even in the automatic i am using my brakes far less on the same tracks in low low than i was.

Other major area was whn pulling the camper trailer, i use less fuel than previoulsy with it hooked up adn can get past other vehciles far more efficently and safely.

When we went to South Coast NSW over Summer we were easily able to get past cravans and the like and keep up the 100 or 110kmh speed espically up the hills where previously fully loaded it was labourign much harder and took a lot longer to get past often amking it unsafe to pass.

All in all very happy i did it but my fuel bill has not latered greatly, still excessive, but the car sounds great and goes a lot better from point to point.

Also i had it Dynoed both before and after and it went from abut 75 at the wheels to 120 at the wheels accordign to the company that did it. If you look up APS, who supply Unichip, search Google, they have a power and torque graph on there and mine was pretty close to theirs.

Hope this helps.

AnswerID: 170388

Reply By: Moose - Wednesday, May 03, 2006 at 13:43

Wednesday, May 03, 2006 at 13:43
G'day Brendan
I don't own a 100 so I can't specifically answer your question however when I've looked into this sort of thing I've always found that it would take a long time to recover the cost due to the marginal consumption difference they make. So do the numbers before parting with the dollars.
AnswerID: 170428

Reply By: Don from Fitch Fuel Catalyst Australia Pty Ltd - Wednesday, May 03, 2006 at 18:58

Wednesday, May 03, 2006 at 18:58
HI Brendan, Give Darren Hardy a ring on 0246471277 Narrellan 4x4 he will advise you of how to save up to two litres of fuel every 100klms you drive, he drives a V/8 cruiser,nice guy.

Regards BILLS
AnswerID: 170506

Follow Up By: Leroy - Wednesday, May 03, 2006 at 20:11

Wednesday, May 03, 2006 at 20:11
of course he will........just like the VT commodore...over 600km difference between the worst before and best after fitting figures.....yeh right!

FollowupID: 425935

Follow Up By: Leroy - Wednesday, May 03, 2006 at 20:15

Wednesday, May 03, 2006 at 20:15
oh and billdon a quote from another thread

ExplorOz Team - David posted this followup


David @ Engine Saver Low Water Alarms is an advertiser as per the text link (Visit this ExplorOz Advertiser). You may or may not be able to see that link if you use that Norton Internet Security thing. We have a policy that advertisers are most welcome to post replies to questions or topics, they are not to advertise their products directly however answers and input on topics is welcome.

I hope this clarifies any issues.
FollowupID: 425937

Reply By: FZJ 80 - Wednesday, May 03, 2006 at 19:27

Wednesday, May 03, 2006 at 19:27

LPG is the answer. Allow $2500 if you want it in cargo area (Convert to 5 seater) or prob $700 more if you want tank under rear. I put mine in rear to retain the off road clearance and retain both petrol tanks. I love it. $45.00 fills the tank and gives me 400 km on highway cycle.

When you hand over the $45 at the cashier you will be sold.


AnswerID: 170514

Reply By: Member - DOZER- Wednesday, May 03, 2006 at 19:43

Wednesday, May 03, 2006 at 19:43
Mate...a Unichip electronic tuning chip will give you better economy...but an outlay of 1400 dollars will take a while to get back.
The extracters will make the car more efficient, but again, 1000 dollars for a few % is not good ecoomy....Value for money, replace the large round muffler and you will get gasses out faster....downside is the exhaust will be noisier...
U get nothing for nothing....
AnswerID: 170519

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