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Discussion Starter #1
I bought my R33 GTS25T totally stock ... but added HKS actuator (as the standard was boosting only at 0.5bar) and an HKS panel a/Filter ... by the way, the boost was set at 0.7bar and heat range 8 Iridium NGK plugs were used.

I noticed that during colder weather there was a slight mis-fire at between 5,500 Rpm and 6,000 Rpm ... so I VERY CAREFULLY re-gapped the plugs to 0.8 and the problem was cured ... although I did still notice that she still perhaps didn't quite pull as hard in this little 'band' of the rev range, but this was hardly noticeable - so I never really paid it any more mind

I then fitted recently an RSR-Invidia straight thru Cat-Back 3" Exhaust System ... and once again the symptoms have returned slightly ... the mis-fire during colder spells (mainly at night) is slightly there and in the day time the hesitancy is there in the 5,500 to 6,000 rev range .... with what seems a bit like a 'surge' in power between 6,000 right up to the 7,000 red line ... it's therefore a bit like driving an S2000 cos you really notice the increase in pick-up right at the high end of the rev range, near the red line Hahahah!!

But, jokes apart, I think it isn't the plugs as they are '8' heat range so they are nice and 'cold' and the coil packs were all cleaned and refitted ... could it be that there is a little too much boost which is making the car over fuel at this point in the rev-range??

I have a buddy who is a bit of an ECU expert and ( I ashamedly know very little about this stuff or anything really to do with mechanics) he says that it could be a 'blip' in the "Throttle Switch" mechanism ... and I may therefore need to replace that ... rather than getting an after-market SAFC to regulate the fuel flow ...

I, myself am not sure .... I also wondered if any of you in your better experience and knowledge than me would honestly think that the mods I had made to an otherwise 'stock' car would necessarily warrant having an uprated SAFC fitted???
 

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hi bud, yr find a common problem with fitting the few mods you have is over fuelling, to be honest yr pal is right, either a piggy back or stand alone ecu is required to even out yr power curve.....also the sudden surge is a 2 stage boost, to which is why you notice that power increase, we have a mod to diffuse it and just run the second stage and its simple to do here is a link to it....http://www.skylineowners.com/forum/showthread.php?t=62994
 

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also before you go and buy anything you need to see what power you will want in the future so as when you do more mods, you only replace it all once....also the iridium 8s are probably a bit too cold for yr stage of mods....a warmer plug will help
 

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Discussion Starter #4
also the sudden surge is a 2 stage boost, to which is why you notice that power increasehttp://www.skylineowners.com/forum/showthread.php?t=62994
Thanks for the confirmation re the overfuelling thing ... but I apologise that I did not also advise that I did also have the 2-Stage Boost thing removed so it spools up to Hi-Boost (on Standard Turbo though...) straightaway ...

My mate was thinking that something in the throttle switch was perhaps 'worn' ... but as you have indeed confirmed for my prior thoughts ... it IS an overfuelling problem ... and I will be looking into an ECU upgrade or 'Piggy-Back' upgrade ...

I take it that the latter is a cheaper option??

Anyways, thanks so much for your help ... I am still so 'green' when it comes to this stuff ... but willing always to learn!!

Much Appreciated!!!
 

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Discussion Starter #5
also before you go and buy anything you need to see what power you will want in the future so as when you do more mods, you only replace it all once....also the iridium 8s are probably a bit too cold for yr stage of mods....a warmer plug will help
Thanks re that too ... I used to have '6' heat range ... maybe '8' was a jump too much ... so I'll look into 7's ....

I have to say that there must be some 'mileage' in what you say here ... because after the car has been driven hard for a while and the engine is nice 'n' hot etc. etc .... there is slightly less of a flat spot!!!

So ... maybe the '7's will be a better bet??

Thanks again!!
 

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yes indeed piggy back (like Apexi SAFC2) is cheaper than ecu
Thanks for the confirmation of that ... Any ideas how much I can pick one up for and also what sort of labour is required to get it 'into effect'??
 

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Thanks re that too ... I used to have '6' heat range ... maybe '8' was a jump too much ... so I'll look into 7's ....

I have to say that there must be some 'mileage' in what you say here ... because after the car has been driven hard for a while and the engine is nice 'n' hot etc. etc .... there is slightly less of a flat spot!!!

So ... maybe the '7's will be a better bet??

Thanks again!!
yea, wen u said it was pretty much stock and u had '8's on, i immediately pointed that out to myself. too cold. the way i figure is... 1 step colder for every +100 hp gain u have over stock. so '7's should be sufice.

as for safc2, i got mine for about 125 quid on ebay. but they are hard to come by.
 
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