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A diesel expert can wind up the injector pump to increase the fuel that gets injected, and increase the boost to compensate the extra fuel. A 3" exhaust will get rid off the extra gases quicker. Same as a chip does on efi.
You will defiantly feel the result.
3" exhaust is certainly worth it it will help with your response and will lower your egts slightly and sounds sick as well :). As for the dyno if you are going there to improve they are the best way of netting gains out of your donk they have all the correct tools to make sure your air/fuel ratio is correct so you dont go doing any damage to the engine. If you get to a good tuner tell them what you want say 12 psi and i want it to tow reliably all day everyday for eg and they should be able to get it singing for you just the way you like :)
tesa, can you tell us what year your GU 4.2 is? As the other guys have said, yes a dyno is the best way to determine the current performance level of your GU, ie current boost, current exhaust gas temp (EGT) & current power output at the rear wheels (kw & torque). Have a look at the link to see an example of what info a dyno will give you. http://www.youtube.com/watch?v=ZijIm...eature=relatedQuote:
Originally Posted by teza04
The 285/75/16 (32.83") tyres you are running are non-standard size, so that will cause your GU to perform slower (for want of a better word) than if you were running standard tyres (31"). Also, unless you've replaced the speed cog, your speedo reading will be inaccurate. When your speedo is reading 100kph you'll probably be doing about 105kph or thereabouts.
The standard Nissan exhaust meets ADR but doesn't provide the best level of engine performance, hence you can gain power, torque, fuel & EGT efficiencies by fitting an aftermarket performance exhaust, normally 3" for a 4.2, either with or without a dump pipe off the turbo, but a dump pipe will improve engine efficiency. Not sure in what context the guy at opposite lock's advice was that ' a dyno would do very little'. He may have been suggesting that a dyno without then fitting a 3" exhaust would not give you any increased performance, but at least by putting your GU on a dyno you'll be able to see what boost it is currently running & what kw it's producing at the wheels. Even without fitting a 3" exhaust, a good tuner should be able to tune your GU for best fuel efficiency for towing, taking into consideration your lager than standard tyres.
Also, don't know what type of air filter you are currently using, or how clean it is, but a dirty/old air filter will inhibit air intake & will reduce engine performance/efficiency. In the link you'll see they fit a K&N air filter. They are a quality filter that will last the lifetime of your GU, but because they are an oil based filter they will clog more quickly off-road. For on-road use I think they are the ducks guts, but that's a personal opinion. To overcome off-road clogging, you can carry a standard filter & swap out the K&N before you hit the dirt/dust.
Is your fuel filter due for a change? How many k's since your injectors were last serviced?
cheers
had the dynotune done and went from 59kw at 3000rpm to 78kw at 3000r,apparently it was still on standard nissan settings so has been boosted , they didnt find anything wrong which is a relief, next job on the list will be a 3'' exhaust at a later date, thanks for all the feeback excellent site to get knowledge from
Good result
thanks dingo that helped me out heaps