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HOW MUCH BOOST CAN I RUN IN MY GTR?
A BASIC GTR MODDING GUIDE....by MAZGTR
Well how long do you want your cars engine to last?...
Any increase in boost level over the standard PSI is going to add load and wear and tear to your GTR's engine and components. It will also show up any weaknesses or faults in things like your fuel system and other components that will inevitably be working harder.
Fortunately the GTR was blessed with a very strong internal engine straight from factory... consisting of things like shotpeened conrods, forged pistons and careful port matching of the head and manifolds. The GTR also scored a very large IHI Turbo. The turbocharger was specifically developed for the GT-R application by IHI. The RHF6CB turbocharger has a 62.0mm turbine and a large 65.0mm compressor. With a front mounted intercooler standard from factory and an excellent designed exhaust manifold.,. the components are there for a much higher level of power than what the GTR came with from the factory. These components were necessary as the GTR was built for 1992 WRC
Homologation, and so the rally versions of the car were going to making in the area of 300-350BHP. This all spells well for the owner of a stock GTR that is interested in raising the cars performance level, as the car has plenty of potential. From factory the GTR's air-intake and exhaust are its biggest restrictions on power levels and breathing abilities...The factory air-box can be replaced with a modern pod style filter that can be made to fit an adapted plate bolted onto the cars AFM. For people really serious about performance they can extend their cars induction pipe down into the right side spotlight hole in the front bumper.
With this alone the GTR's performance is greatly increased..more so than with most Turbo charged cars. The GTR exhibits a nasty flat spot with the standard air-box at about 6000rpm.. The exhaust system is next on the list like
most other Turbo cars. With the fitting of a 3inch exhaust system, hi-flow CAT and straight thru muffler..the cars mid-range performance will greatly improve... At the this stage a custom dump-pipe can also be fitted..this will not increase maximum power out-put by much, but what it will do is prevent the power dropping off in the top-end as dramatically as it does with the stock pipe fitted..With these few mods installed on your car, your GTR will be transformed!!!.. it will now be making around about 210kw/280bhp... and in a small 4WD hatchback that makes for a very fast car!!!... At this level of performance your GTR will be able to run low 13sec quarter mile times.. with high 12sec passes a possibility with a hi-rpm launch off the start...(not
recommended though)..
Once at this level of performance though...i cant stress enough the importance of spending a little money and time MAKING SURE YOUR CARE IS TUNNED PROPERLY.... the air-fuel ratios must be adjusted to prevent the chance of detonation occurring thru leaning out of the engine under load. Half an hour on a rolling road/dyno want cost the earth..but it will lessen the chances of your GTR's engine suffering from potentially disastrous faults in your cars setup. With just these 2 mods my GTR was showing signs of detonation in the upper rev range..YOU HAVE BEEN WARNED!!!
At this stage of the cars development a manual bleed valve can be employed to enable the setting of boost level your GTR is running. At this stage of modification, and after having the cars state of tune checked, boost can usually be set at about 17PSI / 1.1BAR. This is not the same for every car though.. in order to run this level of boost, all of the cars auxiliary systems and components MUST BE UP TO SCRATCH, the fuel system especially.
Further modifications to your GTR are then really limited by your budget and ambitions..and what the cars intended purpose is. The fitting of an aftermarket larger intercooler to a GTR will work very well, the cars maximum power output will increase by very little or nothing at all. But the car will no longer suffer from heat soak and the engine will also benefit from lower temperature levels. With the fitment of an aftermarket ECU or CHIP..the cars air-fuel ratios can then be adjusted to safely take advantage of the cars new level of performance potential. With the right tuning the car can now most likely be able to run up to 19PSI / 1.3BAR. Beyond these boost levels the GTR's fuel system is unable to keep up fuel supply and your GTR will suffer from leaning/ detonation... and your GTR's engine will fail.. With the fitting of larger fuel injectors and an uprated fuel pump.. the car could now be tuned to run up to about 24PSI / 1.6 BAR.. although the car may be able to run this level of boost..IT IS AT A VERY LARGE LOAD AND STRAIN ON THE CARS ENGINE... and reliability is going to be very short.
For me the best level of performance for a GTR, is with an air-intake and exhaust fitted. An uprated larger intercooler and some form of aftermarket engine management fitted. With these mods your GTR will be making over 300BHP and be able to run the quarter-mile consistently in the 12sec bracket, and that kind of performance coupled with the cars superb handling will mean that only a select few cars would be able to keep up with you on a twisty piece of road..
Basic Tuning Rule #1
Always make sure the car is running 100% as the factory intended before you start tuning. everything should be serviced properly and in tip top shape, otherwise, you'll just have bigger problems further down the line...
Basic Tuning Rule #2
More Performance = Less Reliability
These cars left the factory with the engine very restricted, so engine wise they do have a lot in hand, and sensible mods won't hurt engine life. BUT if you increase the performance, you should also increase the serice intervals to make sure the car is running 100% all the time, and you should plan to replace items such as plugs, fuel filters, leads etc at regular intervals to avoid the chances of something failing and killing your car. Also, go easy on the gearbox, or expect a big bill...
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