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R33 Gts-t Boost Cutting

syfon

By syfon,
in Western Australia

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syfon Veteran

syfon

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Hey guys,

I acquired my r33 gts-t almost 2 weeks ago now.

This past sunday the 22nd Feb i serviced it. Changed the oil, oil filter, fuel filter and spark plugs.

With regards to the spark plugs, i replaced them with brand new standard nissan plugs. Just before u did the service the car was well running quite smooth and fast. Just after i completed the service and put everything back in the engine bay as i took it out, it started to boost-cut? My brother did reset the computer by d/c the battery and holding the brake.

Mods-wise, the car has an FMIC, turbo-back exh, dump pipe, and greddy profec b spec 2 boost controller.

The other thing that has been done (by my brother also lol) is the gasket for the stock nissan blow-off valve was taken out and a solid gasket was put in, so the blow-off valve effectively does not work and i get the turbo-flutter effect.

Any ideas why it is boost-cutting? (i'm running 10psi)

Cheers fo your help guys

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FLN75S Mentor

FLN75S

Posted
Posted

It could also be the coils breaking down i had the same problem in my R33 GTST after i serviced it and put new plugs etc and tried turning the boost up to 10psi. it sounds almost the like the car is pinging badly when it does it.

I used to run around 9.6psi once the coils where replaced in my 33 and it was fine much more than that and it would hit boost cut.

Try turning down the boost to see if the problem goes away.

syfon Veteran

syfon

Posted
  • Author
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Are you sure it's boost cut, and not plug break-down ?

I am pretty sure it's boost-cutting. Foot flat in 3rd, 4th gears erc and by about 4000rpm the boost just drops and the car just lurches forward becuase there is no acceleration for a split second then it comes back on...

FLN75S Mentor

FLN75S

Posted
Posted
I am pretty sure it's boost-cutting. Foot flat in 3rd, 4th gears erc and by about 4000rpm the boost just drops and the car just lurches forward becuase there is no acceleration for a split second then it comes back on...

That does sound like boost cut you sure by disconecting the battery you havnt reset the boost controller i have the same controller in my 34 just out of curiosity what percentage of boost do you have set on the controller and what is the set/gain level?

syfon Veteran

syfon

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Ok, first of all i'll wind down the boost to about 5-7psi and give that a shot.

If that has no effect, i'll take out the coils, check them and put them back in. The coil packs are factory.

Do you guys think that blocking off the stock blow-off valve would be effecting it at all?

FLN75S Mentor

FLN75S

Posted
Posted
Ok, first of all i'll wind down the boost to about 5-7psi and give that a shot.

If that has no effect, i'll take out the coils, check them and put them back in. The coil packs are factory.

Do you guys think that blocking off the stock blow-off valve would be effecting it at all?

No this should have no effect under acceleration boost is controlled by the wastegate which is controlled by the boost controller. you could also check you dont have a leak in one of the intercooler pipe joins or in the boost controller pipeing.

syfon Veteran

syfon

Posted
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No this should have no effect under acceleration boost is controlled by the wastegate which is controlled by the boost controller. you could also check you dont have a leak in one of the intercooler pipe joins or in the boost controller pipeing.

Yeah i have already played around with the boost controller settings as to how fast the wastegate opens and closes, and it didnt seem to have an effect on the boost-cutting.

I will double check all vacuum lines/piping/etc tonight to make sure it is on properly. Although just before i changed the plugs it was all fine.

Would resetting the stock computer have anything to do with this?

GTS-t VSPEC Grand Master

GTS-t VSPEC

Posted
Posted

Boost cut occurs when the AFM's max's out, normally this occurs if you wind extra boost into the car, which equates to more air flow. But it can obviously also occur if you have a boost leak, as to get your 10psi with a leak the turbo will be pushing alot more air through. Shouldn't have anything to do with the ECU.

FLN75S Mentor

FLN75S

Posted
Posted
Yeah i have already played around with the boost controller settings as to how fast the wastegate opens and closes, and it didnt seem to have an effect on the boost-cutting.

I will double check all vacuum lines/piping/etc tonight to make sure it is on properly. Although just before i changed the plugs it was all fine.

Would resetting the stock computer have anything to do with this?

Not 100% sure about if it would effect it but it may of because the computer does self learn a little bit i believe so it gets used to the higher boost resetting it might of confused the computer but i doubt that would be the problem.

So do you know the settings you have on you Greddy boost controller ive only just got mine and am trying to set it to 10psi?

syfon Veteran

syfon

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Off the top of my head i'm not sure, but i will check my settings and post what i have them set too.

Ok well i'll wind the boost down to 7psi, check all the intercooler piping and the coil packs and then see if it still does it.

Thank you very much for all of your help guys! Much appreciated :(

FLN75S Mentor

FLN75S

Posted
Posted
Off the top of my head i'm not sure, but i will check my settings and post what i have them set too.

Ok well i'll wind the boost down to 7psi, check all the intercooler piping and the coil packs and then see if it still does it.

Thank you very much for all of your help guys! Much appreciated :(

Cool would be good to see if i have mine set anything like yours.

syfon Veteran

syfon

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I played around with the boost settings on my boost controller last night and it seemed to stop boost cutting once i had turned it down....then i was driving to work this morning and it boost-cut :) I also checked the coil packs last night and all piping and everything seemed to be on properly/fine.....

My brother recommended sending the car to Hyperdrive/Ovaboost/etc to have the boost controller tuned properly for 10-12psi....

Any other suggestions before i book it in for a dyno tune?

FLN75S Mentor

FLN75S

Posted
Posted
I played around with the boost settings on my boost controller last night and it seemed to stop boost cutting once i had turned it down....then i was driving to work this morning and it boost-cut :) I also checked the coil packs last night and all piping and everything seemed to be on properly/fine.....

My brother recommended sending the car to Hyperdrive/Ovaboost/etc to have the boost controller tuned properly for 10-12psi....

Any other suggestions before i book it in for a dyno tune?

Cant really think of anything else that you can do sorry, be interesting to see what they come up with i def want to know what settings they put your boost controller on im thinking of taking mine somewhere to get checked.

GTS-t VSPEC Grand Master

GTS-t VSPEC

Posted
Posted
Any other suggestions before i book it in for a dyno tune?

What do you have for them to tune ? If you had an SAFC then that would modify the AFM signal going to the ECU. It's the AFM signal maxing out that causes the boost cut issue.

syfon Veteran

syfon

Posted
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What do you have for them to tune ? If you had an SAFC then that would modify the AFM signal going to the ECU. It's the AFM signal maxing out that causes the boost cut issue.

When i brought the car almost 2weeks back it had an SAFC2 in it, but i have since taken it out and sold it....

GTS-t VSPEC Grand Master

GTS-t VSPEC

Posted
Posted
When i brought the car almost 2weeks back it had an SAFC2 in it, but i have since taken it out and sold it....

Umm, why ? You'll need the SAFC if your planning on making more mods etc. Any more than 10-11psi will see you hitting boost cut otherwise.

syfon Veteran

syfon

Posted
  • Author
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Umm, why ? You'll need the SAFC if your planning on making more mods etc. Any more than 10-11psi will see you hitting boost cut otherwise.

My brother recommended to take it out to improve fuel economy as modifications to the vehicle are currently limited to an FMIC, air pod and turbo-back exh.

After i took out the SAFC2 the car was running perfectly normal, no boost cuts, smooth as silk; it was only once i had changed the plugs that i got the boost-cuts.....

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