# Fuel economy after Y-pipe and ECU upgrade



## redlimo (Mar 25, 2011)

I have owned a GTR for nearly two years now, and never been tempted to upgrade the power - the car just doesn't seem to have a problem in this area! However it does seem to be quite easy / inexpensive to do, and I'm now thinking - why not?

I would be interested to know what kind of difference in fuel economy anyone who has upgraded the exhaust and ECU has seen. I'm tempted by one of the milder Litchfield options.

Any other drawbacks anyone has noted, for example driving in stop/start city traffic?

Thanks in advance.


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## alloy (Apr 29, 2005)

mods are in my sig, but i have done 335 since i filled up last week both gauges on the dash and mfd indicate there is no fuel left but the range still says 44miles :nervous:


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## GTRSTAR (Nov 26, 2009)

redlimo said:


> I have owned a GTR for nearly two years now, and never been tempted to upgrade the power - the car just doesn't seem to have a problem in this area! However it does seem to be quite easy / inexpensive to do, and I'm now thinking - why not?
> 
> I would be interested to know what kind of difference in fuel economy anyone who has upgraded the exhaust and ECU has seen. I'm tempted by one of the milder Litchfield options.
> 
> ...


Dear O Dear, What has happened to this forum since they moved the projects?!!:runaway:

Is there any difference in fuel economy after upgrading the y pipe and ecu?!!! lol :repost:

Of course there is! your making something go faster which requires more energy which generally requires more fuel?! Hello?! :chairshot

Will you notice the difference?! not unless you drive dangerously slow or dangerously fast which is against the highway code in any case.. :banned:

You may as well have asked; does winding the window down make the cabin more noisy or does turning the aircon on reduce the BHP?! Stop procrastinating and just do it! :thumbsup:


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## Adamantium (Jun 24, 2002)

Actually if you have a custom map you can improve the cruise area which notoriously over fuels. Yes the higher power costs more fuel but given the proportion of time you use it you may find range per tank will increase.

Once mapped if you intentionally drive for economy you will see an improvement.


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## thistle (Oct 27, 2007)

The cruise area is stoichiometric at uk cruising speeds.


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## ROG350Z (Jun 15, 2008)

thistle said:


> The cruise area is stoichiometric at uk cruising speeds.


Explain.....?


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## Adamantium (Jun 24, 2002)

It means I'm wrong!

The fuelling isn't improved off boost in the cruise zones but remains at lambda of 1.

John, if you are here now perhaps you can explain where the benefits are to fuel consumption.


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## Adamantium (Jun 24, 2002)

I said cruise is rich, John says cruise is at stoich which means ideal ratio for combustion. Ie, it's not cruise that soots up your exhaust pipes!

Personally I think a car with an emissions reduction system should run lean on cruise but that's another issue.


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## thistle (Oct 27, 2007)

Air-fuel ratio - Wikipedia, the free encyclopedia

Some reading here ROG.

Without direct injection, EGR or NOx cats then it wouldn't be possible to keep the NOx down with lean cruise, except for other expensive or experimental tech that Adam will know more about than I, but with the hardware on the GTR it runs richer than necessary for emissions. You could tweak the ignition timing during cruise to help economy perhaps, but more advance would also increase NOx.

So on the VR38 there really isn't a free lunch in terms of economy tuning at cruise without removing the cats and increasing NOx.

I do believe mapping helps economy in the performance areas if you drive at the same speed because you need lower engine speed and leaner AFRs.


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## ROG350Z (Jun 15, 2008)

thistle said:


> Air-fuel ratio - Wikipedia, the free encyclopedia
> 
> Some reading here ROG.
> 
> ...


Brilliant thank you I shall read up - always good to learn new things! Going to send my map to Ben after doing some more test runs now ECU settled down. Be great if you could look at it too as always good to have two sets of eyes!


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## thistle (Oct 27, 2007)

Ben is so good at this, I would happily let him tune my own car and not check it, he has mapped more R35 than anyone I know, and as intended from the start he now does it without my assistance which lets me get on with development. In fact my highest performance map is one that he did for John H last year.


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## ROG350Z (Jun 15, 2008)

thistle said:


> Ben is so good at this, I would happily let him tune my own car and not check it, he has mapped more R35 than anyone I know, and as intended from the start he now does it without my assistance which lets me get on with development. In fact my highest performance map is one that he did for John H last year.


Always good to know - obviously trust him as I let him tune my pride and joy.

Big praise though coming from you.


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## paulcoop007 (Oct 31, 2009)

I get around 23.5 with a y pipe fitted, mixed driving.


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