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Discussion Starter #1
hi guys,

my skyline, a r33 gtst, has been dynoed at approx 370bhp, the car is quick to 100mph but after that it struggles and starts jerking and making blow back noises. im not sure what the problem could be. pls adivse.

thanks in advance.
 

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Super Maude
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156 Posts
Sounds like you're breaking up under the intense load on the motor. Either your ignition system is on the way out (does it have an ignitor I can't remember?.. Those are the signs on those is surging under high load) or it could be an issue with the fuel not reaching pressure. Does it have an aftermarket fuel pump? Do you have a fuel rail psi guage? And does it blow any smoke when it's jerking (black smoke means it's usually a coil issue rather then fuel because you're getting to much fuel).

There's a few options for you mate :)
 

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Super Moderator
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Whats the full spec? we cant diagnose whats wrong when we don't have all the info. there could be so many causes.
 

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Discussion Starter #7
Spec level

Whats the full spec? we cant diagnose whats wrong when we don't have all the info. there could be so many causes.
Its a 2.5 single turbo, 1993, its got fully forged engine block, hks mushroom induction kit, hks dump valve, 555cc injectors, uprated ecu and thats all im aware of. I'v just bought the car so am still learning but i'v got a budget of £2000 to spend on the car, its due a full major service - timing belt kit as well. I'd like to purchase a fmic as a mod and any money left over from repairing it want to spend on mods. Also when you red line the rev meter the car spits flames from the exhaust even though it has NOT got a flame kit. I don't know if thats an issue but i don't mind lol. With the money I have what kind of mods u guys think are best? And is the problem defo the coilpacks? Anyone had the same problem?
 

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Super Moderator
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If you have an mapped ECU then I would expect the limiters has also been removed, do you know the spec of the ECU any stickers on the case?
Is it spitting flames when you lift off the throttle? has it got a vent to air BOV?
 

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Discussion Starter #10
Im not sure i'll have a look and get back to you on the ecu. It spits flames when foots fully on the throttle and u red line it. And im not sure if the bov is vent to air. It just days hks on it. Im thinkong because i'v got £2k to play with i'll change the coilpacks anyway because they should be done at a major service right? The cars done 115k km and I don't think its been serviced for a while it was in dry storage for 2 years
 

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Super Moderator
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Im not sure i'll have a look and get back to you on the ecu. It spits flames when foots fully on the throttle and u red line it. And im not sure if the bov is vent to air. It just days hks on it. Im thinkong because i'v got £2k to play with i'll change the coilpacks anyway because they should be done at a major service right? The cars done 115k km and I don't think its been serviced for a while it was in dry storage for 2 years
Coil packs are not part of a major service, sounds like you have a a vent to air BOV which will usually cause the engine to flame on lift off/dump when on boost, however the fact that its doing it at WOT indicates that its missing at high load, so it could be down to coil packs or over fueling, but it still could be down to the limiter still being in place, is there a definite misfire that you can feel?
 

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it is possible to run 550cc injectors on a bone stock ECU.

I know someone who tried it and the car drove sort of OK at part throttle.

I am not recommending it at all, but I can't see why 550cc's would be fitted before a FMIC?

the poor fuelling may be the result of 550's and no engine management??
 
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