bean962 Posted February 20, 2008 Share Posted February 20, 2008 Hello all. I am so angry I cant find the reason for this so I'm offering a reasonable reward for the soloutiion. I have an R33 GTS-T and a massive flat spot at 4500 rpm until 6000. I have replaced or changed:- ECU New Coil packs (for splitfires) New Iridium plugs AFM CAS Ignition amplifier Knock sensors The diagnostics say the ignition retards to about 5Deg at 4500 rpm and then goes back to normal 15/17 deg at 6000. Obviously during this period its running rich, so any ideas? Link to comment https://www.sau.com.au/forums/topic/207039-r33-gtst-flat-spot/ Share on other sites More sharing options...
l0WRB Posted February 20, 2008 Share Posted February 20, 2008 dont know how many times its been covered. buy an after market ecu and get it tuned. Link to comment https://www.sau.com.au/forums/topic/207039-r33-gtst-flat-spot/#findComment-3661962 Share on other sites More sharing options...
TTT Posted February 20, 2008 Share Posted February 20, 2008 you joined up, then 5 minutes later created this thread. so when exactly did you search for the words R33+4500rpm+flat+spot. as above, the factory ecu causes it. seems even worse when boost is increased. Link to comment https://www.sau.com.au/forums/topic/207039-r33-gtst-flat-spot/#findComment-3662018 Share on other sites More sharing options...
bean962 Posted February 20, 2008 Author Share Posted February 20, 2008 Sorry, I've only had a skyline for a week and I just thought the Aussie club would offer better advise than our UK forums. The car is completely stock except big bore front pipe and de-cat pipe. Is the problem likley to be the boost solenoid? Regards Link to comment https://www.sau.com.au/forums/topic/207039-r33-gtst-flat-spot/#findComment-3662155 Share on other sites More sharing options...
sik14 Posted February 20, 2008 Share Posted February 20, 2008 Sorry, I've only had a skyline for a week and I just thought the Aussie club would offer better advise than our UK forums.The car is completely stock except big bore front pipe and de-cat pipe. Is the problem likley to be the boost solenoid? Regards does it just sound like its missfiring then clears its throat and pulls fine through the rest of the rev range? Link to comment https://www.sau.com.au/forums/topic/207039-r33-gtst-flat-spot/#findComment-3662273 Share on other sites More sharing options...
(B1) MR_fanny Posted February 21, 2008 Share Posted February 21, 2008 you have replaced the ecu with what? mine had a masive flat spot mid range, probably due to all the minor mods i wacked in. got a light tune when i got the exhaust cam gear installed and no more flat spot. Link to comment https://www.sau.com.au/forums/topic/207039-r33-gtst-flat-spot/#findComment-3662408 Share on other sites More sharing options...
Ultimategtr Posted February 21, 2008 Share Posted February 21, 2008 what gap are ur plugs running? i had the same problem with the stock coils.. i replaced with .8mm NGK coppers and it went away.. Link to comment https://www.sau.com.au/forums/topic/207039-r33-gtst-flat-spot/#findComment-3663019 Share on other sites More sharing options...
bean962 Posted February 22, 2008 Author Share Posted February 22, 2008 Thanks for all your constructive replys Yes it stutters at 4500 and then at 6000 clears its throat and bang....BHP up to 260 I've replaced the o/e ECU with a standard unit The plugs are greddy Standard boost Ignition retards to 4 or 5 deg at 4500 and then goes back to 16/17 at 6000 The voltage on the AFM goes off scale at this RPM but the turbo pipes have been checked and no leaks found. I'm buggered...... Link to comment https://www.sau.com.au/forums/topic/207039-r33-gtst-flat-spot/#findComment-3668293 Share on other sites More sharing options...
bean962 Posted February 22, 2008 Author Share Posted February 22, 2008 I appreciate I can change the ECU to a Power FC but Nissan didn't design the car to run like this so fitting a power FC will only mask the problem and no diagnose the reason. Link to comment https://www.sau.com.au/forums/topic/207039-r33-gtst-flat-spot/#findComment-3668295 Share on other sites More sharing options...
R33silverS2 Posted February 23, 2008 Share Posted February 23, 2008 I appreciate I can change the ECU to a Power FC but Nissan didn't design the car to run like this so fitting a power FC will only mask the problem and no diagnose the reason. it won't 'mask' the problem... it will FIX the problem. The problem is your ecu - the standard nissan ecu is the problem. as covered many times it has factory protection wirtten into it which retards the timing and richens the mixtures when airflow exceedes a certain amount. you obvisoulsy have higher boost than stock to make 260hp, what boost is the car actually running? A power fc is a full replacement engine ecu not a piggy back so thier is no 'masking' so to speak. edit: do you have a boost gauge or are you just using the standard one? stock should be 7psi and therefore your airflow metre should not be maxing out at this level. Link to comment https://www.sau.com.au/forums/topic/207039-r33-gtst-flat-spot/#findComment-3668520 Share on other sites More sharing options...
mattymagoo22 Posted February 23, 2008 Share Posted February 23, 2008 Bean. Nissan designed the car to run exactly how it came off the production line. 3psi<4500 7>4500rpm, no big bore exhaust without a cat. The second you change the exhaust, boost,tubo, fuel pressure etc etc these are things that can potentially harm or in some cases destroy both the engine and the turbo. As mentioned before if boost is raised the cars ECU goes into R&R (richen up and retard timing) to prevent high cylinder temps and detonation which occur when outright power is sort after and none of the supporting systems are considered (AFRs, intake temps, injector duty cycle etc etc). So to sum up, installing an aftermarket ECU or having a tune done is not masking the problem, it is simply getting the most from what you have SAFELY! the factory tune isn't designed for outright power, its a compromise between power, economy and longevity and by running the way it does its saying something isn't right I got to save myself and so the extra fuel goes in and the timing gets pulled out of it. Cheers. Link to comment https://www.sau.com.au/forums/topic/207039-r33-gtst-flat-spot/#findComment-3668761 Share on other sites More sharing options...
SLYDA Posted February 23, 2008 Share Posted February 23, 2008 AFM should read up to 5V i believe before maxing out (correct me if wrong) it may be 5.2V - Get a Power FC and a Z32 AFM .. or set ur boost 2 10PSI and dont touch it.. my series had the same problem for about 2 years... try running 14 or 15PSI and it seems fast up to 4500RPM then just died.. Found the car was far faster on 10PSI, now i have a HKS GT3037 Pro S on it.. and at 10PSI with a POWER FC.. all i can say is.. i wish i had of done this 2 years ago.. What you are talking about is called the FACTORY BOOST CUT. Every member on this forum that has even slightly modified there skyline and upped the boost has encountered this problem Link to comment https://www.sau.com.au/forums/topic/207039-r33-gtst-flat-spot/#findComment-3669086 Share on other sites More sharing options...
Yo-Yo Posted February 23, 2008 Share Posted February 23, 2008 As others have already said, it's your factory computer protecting the car from blowing itself up. Any aftermarket replacement ECU will make full use of your modifications, piggyback air/fuel controllers will do the same thing to an extent, but nowhere near the level of a stand-alone engine management systems. Most of the guys mention Power FC because it's arguably the most user friendly ECU, other brands are HKS, Trust/Greddy Emanage, Motec etc. just to name a few... all with various costs and pros and cons. I have a Power FC in my r34 and never had a drama with it, I liked how it already had all the standard ECU maps like cold start and electrics eg. air con control, but let's you re-write the parameters of the factory ecu. Any competent tuner can install these systems and effectively fix the problems you've been experiencing. Link to comment https://www.sau.com.au/forums/topic/207039-r33-gtst-flat-spot/#findComment-3669112 Share on other sites More sharing options...
TTT Posted February 24, 2008 Share Posted February 24, 2008 I appreciate I can change the ECU to a Power FC but Nissan didn't design the car to run like this so fitting a power FC will only mask the problem and no diagnose the reason. bahahaha... but they designed the car keeping in mind that people would replace the front pipe and remove the Cat convertor all together right? Brilliant. Link to comment https://www.sau.com.au/forums/topic/207039-r33-gtst-flat-spot/#findComment-3671198 Share on other sites More sharing options...
R31Nismoid Posted February 24, 2008 Share Posted February 24, 2008 Talking about how Nissan designed the car when the car is not longer the way it was designed? interesting... Link to comment https://www.sau.com.au/forums/topic/207039-r33-gtst-flat-spot/#findComment-3671351 Share on other sites More sharing options...
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