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Rb25Det Misfire/ Surge At 3K

Robbieirving

By Robbieirving,
in Engines & Forced Induction

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Robbieirving Explorer

Robbieirving

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Hi I'm having some problems with my r34 gtt, only bought it afew wks ago, I brought it to insight Motorsport in Sydney for a tune because it is running high boost, he said he can't tune it when it's like that.... It has a high flowed gcg turbo, z32 afm, split fire coil packs, fmic, greddy boost controller which is working as a boost gauge only... Highflow fuel pump andHas 550 injectors.. I changed the standard bov valve to a turbosmart plumb back, cleaned out the highflow cat, swapped over all vac lines, made no difference... 1st gear is fine and second, it only shits itself at 3k revs in 3rd, 4th and 5th! I am changing plugs today anybody have any suggestions???

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wolverine Grand Master

wolverine

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Sort out your boost control issues then he can tune it. If it is the boost controller then that is the best place to start.

Meanwhile get your car sorted of all other potential issues like boost leaks, make sure you have new spark plugs, new fuel filter etc etc.

Robbieirving Explorer

Robbieirving

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He can't tune it when the turbo is surging, afew people have had trouble with gcg turbos surging, the mechanic at insight and Scott said they thought it was a problem with the turbo... Might try a standard turbo and see if that solves it

skylinecouple Experienced

skylinecouple

Posted
Posted

GCG Hiflows are just that, Hiflowed. If the previous owner asked them for it that's what he got. It will flow a little more than stock but that's it. I would expect 230kws at best. However, if the compressor has been changed to a more efficient wheel then more air flow will certainly cause the issues described. There is some porting of the wastegate that needs to be done as GCG usually keep the standard wastegate flap and port size.

I had one years ago and this was the case. Get a porting tool and grind out the wastegate a couple of millimetres. Leave 2mm for the flap to seal against. Try this with new plugs, air filter etc. Get that boost controller working ! Why is it just reading boost ? Is there a problem ? Electronic boost controller is a must have item.

Also, the fact it revs clean in 1st & 2nd makes me think of exhaust blockage. Why did you clean out the cat ? was it blocked ? you can't clean them out. If you could see daylight through it then it was fine. Cleaning it in petrol is probably not the way to do it. Is the exhaust 3" all the way through ? The cat isn't a compliance cat is it ? They are usually less than 3". So many things to look at because we don't know the car.

Anyway, do the simplest things first and work from there. Oh, and you wouldn't be the 1st person to believe you had a hi-flow and it was just a standard rebuild. Get the number off your turbo and ring GCG and ask what they did to it.

Robbieirving Explorer

Robbieirving

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Cheers for that bud, I changed plugs made no difference... There is a full custom exhaust on it, high flow cat, just cleaned the afm there, think it does have some thing to do with the wastegate... I don't know why boost control isn't working.... Trying to fix it now... I just noticed there that there are no pipes connected to vacuum switch... One is broken and not sure where they go anyway....

hypergear Grand Master

hypergear

Posted
Posted

There is one thing I'm not 100% sure. you've mentioned surging / misfiring. They are two separate issues. LIke is the turbocharger surging under load and car is also misfiring on same time? or just engine misfires.

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