Flat Spot Porblem

[TUF250]

Hi all,

I have a flat spot problem, I have searched so much and nothing quite matches mine, particually because mine is still on the standard boost (confirmed by an aftermarket boost gauge!)

Need the help of the pros on this one as I have run out of ideas.

So; My car is an R33 GTS-T manual, only 90,000ks and in immaculate condition. Serviced thoroughly inc timing belt, tensioners etc, timing set professionally.

Mods include:

- 3inch turbo back (bellmouth type dump pipe with an xforce cat, the cat could be old im not sure)

- K&N pod filter (also have the airbox which I have experimented with, amde no difference to this problem)

- R34 GT-T intercooler

Now the car developed a flat spot one day, not just in the midrange but the whole powerband seemed to go a bit flat, just didnt have that pull it used to. In saying that it did not pop, stutter, spit, nothing, runs smooth as silk just seemed a bit flat.

So I started to experiment. I cleaned the AFM, changed oxy sensor and nothing.

I checked the plugs at night for cross fire and nothing.

Then I bought new plugs bcrp6rs-11s and gapped them down to .9. this made it feel a touch better on boost but not like it did before.

Then I thought I would reset the ECU, left the batt disconnected all day and it was great! back the way it was before and more!

I was thrilled but that night I took my cousing out for a little drive to show him the car and it went back to being flat again (it was a cold night, 5-6 degrees)

So this sounds like R&R from what I have read which is fine, but here is the catch, not only am I only running the r34 smic but the car is only on standard boost (5psi then 7 after 5000rpm) Everyone who hits r&r seems to be on 10psi or more?

everyone who has this problem seems to have upped the boost. Now another issue here is that I am only getting 7 as confirmed by an aftermarket gauge, everythign I ahve read says that with these mods I should be getting more like 8-9?

So I am confused here and happy to hear peoples thoughts?

Regards

Jason

[jjman]

Nah mine was like this bog standard too. Is yours series 1 or 2?

where abouts you located? Toshis is in Sydney and can sort this stuff really well.

Hi all,

I have a flat spot problem, I have searched so much and nothing quite matches mine, particually because mine is still on the standard boost (confirmed by an aftermarket boost gauge!)

Need the help of the pros on this one as I have run out of ideas.

So; My car is an R33 GTS-T manual, only 90,000ks and in immaculate condition. Serviced thoroughly inc timing belt, tensioners etc, timing set professionally.

Mods include:

- 3inch turbo back (bellmouth type dump pipe with an xforce cat, the cat could be old im not sure)

- K&N pod filter (also have the airbox which I have experimented with, amde no difference to this problem)

- R34 GT-T intercooler

Now the car developed a flat spot one day, not just in the midrange but the whole powerband seemed to go a bit flat, just didnt have that pull it used to. In saying that it did not pop, stutter, spit, nothing, runs smooth as silk just seemed a bit flat.

So I started to experiment. I cleaned the AFM, changed oxy sensor and nothing.

I checked the plugs at night for cross fire and nothing.

Then I bought new plugs bcrp6rs-11s and gapped them down to .9. this made it feel a touch better on boost but not like it did before.

Then I thought I would reset the ECU, left the batt disconnected all day and it was great! back the way it was before and more!

I was thrilled but that night I took my cousing out for a little drive to show him the car and it went back to being flat again (it was a cold night, 5-6 degrees)

So this sounds like R&R from what I have read which is fine, but here is the catch, not only am I only running the r34 smic but the car is only on standard boost (5psi then 7 after 5000rpm) Everyone who hits r&r seems to be on 10psi or more?

everyone who has this problem seems to have upped the boost. Now another issue here is that I am only getting 7 as confirmed by an aftermarket gauge, everythign I ahve read says that with these mods I should be getting more like 8-9?

So I am confused here and happy to hear peoples thoughts?

Regards

Jason

[ClutchBurndout-:(]

Hi all,

I have a flat spot problem, I have searched so much and nothing quite matches mine, particually because mine is still on the standard boost (confirmed by an aftermarket boost gauge!)

Need the help of the pros on this one as I have run out of ideas.

So; My car is an R33 GTS-T manual, only 90,000ks and in immaculate condition. Serviced thoroughly inc timing belt, tensioners etc, timing set professionally.

Mods include:

- 3inch turbo back (bellmouth type dump pipe with an xforce cat, the cat could be old im not sure)

- K&N pod filter (also have the airbox which I have experimented with, amde no difference to this problem)

- R34 GT-T intercooler

Now the car developed a flat spot one day, not just in the midrange but the whole powerband seemed to go a bit flat, just didnt have that pull it used to. In saying that it did not pop, stutter, spit, nothing, runs smooth as silk just seemed a bit flat.

So I started to experiment. I cleaned the AFM, changed oxy sensor and nothing.

I checked the plugs at night for cross fire and nothing.

Then I bought new plugs bcrp6rs-11s and gapped them down to .9. this made it feel a touch better on boost but not like it did before.

Then I thought I would reset the ECU, left the batt disconnected all day and it was great! back the way it was before and more!

I was thrilled but that night I took my cousing out for a little drive to show him the car and it went back to being flat again (it was a cold night, 5-6 degrees)

So this sounds like R&R from what I have read which is fine, but here is the catch, not only am I only running the r34 smic but the car is only on standard boost (5psi then 7 after 5000rpm) Everyone who hits r&r seems to be on 10psi or more?

everyone who has this problem seems to have upped the boost. Now another issue here is that I am only getting 7 as confirmed by an aftermarket gauge, everythign I ahve read says that with these mods I should be getting more like 8-9?

So I am confused here and happy to hear peoples thoughts?

Regards

Jason

i was about to say boost leak, then you said, reconnecting the battery fixed it temporarily, which is odd, so ur ecu must be relearning its environment over again which is why it seems fixed temporarily, if u disconnect the battery again over night, does it feel good again afterwords? then go back to flat?

[lachlanw]

your car is hitting r&r . do you have a boost gauge ? id be verry surprised if it is 5/7 psi with those mods

what fuel do you run ?

you could try advancing your timing a bit or making sure its correct

[TUF250]

thanks for the replies guys, you can see why Im so confused???

ok in answer to your questions:

- it is a series 2 and I am in vic unfortuanately

- checked for obvious boost leaks, intercooler piping etc and nothing that I could find, idles normally too so it couldnt have a huge leak

- I do have an aftermarket gauge, digital too, max 7 which is a suprise from what I have read. Maybe the solenoid has failed? and due mods 5 has actually become 7??

- fuel is strictly mobil 98, was using BP but seemed to get less milage for the same performance that was the 98 stuff too

keep the replies comming

[TUF250]

any other thoughts or similar experiences and solutions to this?

[paulr33]

stock ECU picking up detonation via knock sensor and dropping to penis fuel map

this is a std protection behaviour and it will fire this when it picks up detonation

i would have expected the ECU to clear this mode when you power IGN off

somehow perhaps it is saving this state in your car and keep the IGN retard perm

there is also something else that is done when you DATA INIT the stock ECU, it does a check to see and advances timing 2deg at boot up

ill check the service manual for the conditions on this

[paulr33]

stock ECR33 boost after 4500rpm with std solenoid is 7PSI, before 4500rpm it is 5psi

you might bleed a touch higher with your exhaust setup, but that's the actuator specs from factory

[ClutchBurndout-:(]

stock ECR33 boost after 4500rpm with std solenoid is 7PSI, before 4500rpm it is 5psi

you might bleed a touch higher with your exhaust setup, but that's the actuator specs from factory

i reckon youve posted that about 5 times in different threads lol, when will people learn! i cant talk you had to tell me

[hr31gts]

Although you said you have tried changing the o2 sensor, I would tripple check it and the circut. Sounds like the fuel maps are changing over time, due to incorrect o2 readings..

[TUF250]

would buying another second hand ecu be worth a try?

I dont understand why it would be detonating. heat range 6 plugs, r34 cooler, freezing in melb at the moment, stock boost? what would cause detonation?

frustrating problem

[paulr33]

poor fuel? poor fuel flow? blocked fuel filter? poor injector control? dirty injectors? dirty fuel rail? poor spark? poor coilpack? poor compression? poor / damaged air intake?

it could be a million things and it really requires basic diagnostics, troubleshooting and some general mechanic knowledge

has it always had this issue? when did it last work ok? what's changed recently etc

[paulr33]

here is the extract that i think is relevant to your issue, read away and good luck

std_diag.pdf

[TUF250]

poor fuel? poor fuel flow? blocked fuel filter? poor injector control? dirty injectors? dirty fuel rail? poor spark? poor coilpack? poor compression? poor / damaged air intake?

it could be a million things and it really requires basic diagnostics, troubleshooting and some general mechanic knowledge

has it always had this issue? when did it last work ok? what's changed recently etc

thanks for the doc, interesting read.

Its a tough one because there are no problems as such, no misfire, no stutter, no surge etc, if anyone else jumped in the car they would think it was perfectly normal.

Question, if the car goes into one of these R&R modes due excessive airflow (eg. cold night) or due detonation will it stay in that mode indefinately unless the ECU is reset or does it return to normal once the car is restarted?

I have done fuel filter, quality injector cleaner, cleaned afm, new airfilter (K&N), new plugs bcpr6es-11 gapped to 0.9, checked coils for missfire (none at all), new oxy sensor.

whats the next logical step? fuel pump? what would be a sign that was failing?

happy to spend the money just want to be heading in the right direction with it. Keen to get it tuned for my 10psi actuator soon so I want it to be all runing right before it goes in.

Cheers

Jason

[DVS JEZ]

put it on the dyno and see if they can see the flat spot, this will tell you where and what it is. ( might be a lean spot or a rich spot etc)

[TUF250]

yeah might be the way to go, would it be worth trying another ECU? do they tend to vary from one to another as to how sensitive they are?

might get a new fuel pump too. anyone have the part number for the bolt in, no modification required walbro or bosch item?