New splitfie coil packs and

[RTED]

Platinum plugs fitted 100 klm ago

Car definately runs better.

Have not had the car long and still learning. Still has a bit of a surging feeling coming onto boost, just doesn't power on cleanly. The exhaust temp sensor was not fitted after the previous owner fitted a 3" system, so i reinstalled into exhaust on Saturday. Drove Saturday arvo no noticeable difference. Drove sunday and power was down and hesitation was worse and it also felt like is was surging on cruise like it was way lean?

No detonation anywhere, Exhaust colour appears lighter, Definately less C0

so what gives?

[Abo Bob]

More info required:

What boost are you running?

Have a FMIC?

Stock turbo?

Is it hesitating or stuttering at all?

Where in the rev range does this surging happen?

[RTED]

More info required:

 

What boost are you running?

Have a FMIC?

Stock turbo?

Is it hesitating or stuttering at all?

Where in the rev range does this surging happen?

Setup is as follows:

unichip piggyback / stock ecu

large fmic / std intake and T/B

apexi pod filter enclosed

3" exhaust from dump pipe

stock turbo/ afm

electronic dual stage variable boost control ( unknown brand ) hyper something.

I assume std injectors and fuel pump?

More recently ( say the last 6 weeks) the hesitation is apparent at low boost setting when the engine is not up to full operating temp/ :at the same temp it seems to run better with a bit more boost. Boost variance on the guage is .5 STD

up to 1.0/1.1 bar at full boost.

The hesitation is mainly apparent at around 3750 rpm, either progressive throttle or mashing the pedal makes no difference. The hesitation appears as you go through the revs from low to higher revs as it spools up. Probably is a bit more severe as you wind up the boost. Sorry to sound vague but I haven't driven the car a hell of a lot since purchase only 3 months ago.

Thanks for your help.

Have done a basic check of most ancilleries and all seems good!

[Blitz]

Dead O2 sensor?

[RTED]

Dead O2 sensor?

Could be? But will it create these symptoms?

[Oosh]

Speaking of O2 sensors what are their normal voltage characteristics?

I have a Impakt DigiDash and the voltage seems to jump about a fair bit at idle but not know what's normal i can't draw any conclusions from it. I do have a quite bad miss @ idle, I've swapped coils for known good ones, igniter box too, I also get some surge under load too but i think that'll be fixed by gapping the plugs down to 0.7m (0.8m atm).

Cheers.

[Abo Bob]

Ok you are running 1 bar and over on a stock turbo. I think you are experiencing compressor surge and you are going to blow your turbo any day now.

Solution - turn the boost down.

[Wazz]

"the hesitation is apparent at low boost setting when the engine is not up to full operating temp/ :at the same temp it seems to run better with a bit more boost. Boost variance on the guage is .5 STD

up to 1.0/1.1 bar at full boost."

let the car get to operating temp first... i dont even think about spooling 2psi of boost up when its not warmed up fully

[RTED]

"the hesitation is apparent at low boost setting when the engine is not up to full operating temp/ :at the same temp it seems to run better with a bit more boost. Boost variance on the guage is .5 STD

up to 1.0/1.1 bar at full boost."

let the car get to operating temp first...  i dont even think about spooling 2psi of boost up when its not warmed up fully

I said that is wasn't at full operating temp NOT dead cold. I agree with your dead cold scenario.this example is after warming the car up stationary for at least 5 mins. Only di#$%^eads give it heaps cold.

The scenario I gave was to enlighten everyone that the problem is not temperature sensative only. There are a few variables to consider

The surge is primarily low to mid boost not high! Doesn't feel like compressor surge as i can manipulate the car into showing compressor surge . was heaps worse before replacing the coilpack and plugs so this seems to be a step in the right direction. I work with a well educated turbo technician whose call is not the turbo.

[Trust33]

I think that if you have a look at 1 of the older threads posted late last year,RB25 DYNO RESULTS here,that most if not all rb25's have a dip in the power,more like a flat spot,in the rpm range that you are talking about.

This mainly happens i think when there is no adj exh cam gear on the car,with stock turbo,boosted.imo.

[NickR33]

at 1 bar your ecu will be freaking out, retarding the timing and fuel etc to protect the motor from overboost... this may feel like 'surging' and will be worse on cold nights etc... just turn the boost down to about .8bar and this should help... if the problem persists see your mechanic

[NickR33]

sorry just read your last post, if it is happening on low boost as well its probably not overboost protection... I still would point the finger at your unichip, sounds like a possible tuning issue... I am no expert, but have had similar problems in the past... good luck:)

[morlock]

My bet would be a faulty airflow meter or maybe on the way out.

Have you hooked up the unichip to a dyno yet to check all the signals. I would do that first to make sure it isn't sensor related. I have a unichip on my R33 and was experiencing similar issues to you. turned out that my airflow metre was dropping voltage occasionally and throwing off the ecu.

Also if an after market exhaust has been fitted with dump pipe then I would check that the O2 sensor has been installed correctly and is in good working order as I have also had this go on me and causes all sorts of fueling issues.

IMO i wouldn't be running anymore than 0.8 bar of boost on the stock turbo (12psi) as you will start snapping fins of the turbine wheel due to them being ceramic.

[RTED]

My bet would be a faulty airflow meter or maybe on the way out.

Have you hooked up the unichip to a dyno yet to check all the signals. I would do that first to make sure it isn't sensor related. I have a unichip on my R33 and was experiencing similar issues to you. turned out that my airflow metre was dropping voltage occasionally and throwing off the ecu.

Also if an after market exhaust has been fitted with dump pipe then I would check that the O2 sensor has been installed correctly and is in good working order as I have also had this go on me and causes all sorts of fueling issues.

IMO i wouldn't be running anymore than 0.8 bar of boost on the stock turbo (12psi) as you will start snapping fins of the turbine wheel due to them being ceramic.

Thanks for the information.

No I haven't had it on a dyno or anyone tune the car according to the "mods" as firstly i haven't had it that long and the chap I bought it from had supposedly had it "tuned" not long before i got it. So I am still going through the process of elimination at the moment. All the information is helpfull for a better understanding of this particular setup as there are lot of similar examples. Have ordered an 02 sensor will try that.

Biggest problem is no-one able to tune car where I am, No dyno or alternate technology. Have to make a trip to ACT I'm guessin.

My next step maybee to fit the M24 Garrett and have tuned to this configuration.What do you think?

Garrett A/R .53

.64

From Diesel Navara. ( factory Nissan )