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Risking Grand Master

Risking

Posted
Posted (edited)

Im curious to see of any one else has had or has this issue with their R32 GTR

When cruising my front tourqe guage bounces around the 6-10 mark and the vehicle has a pronounced surge as the front tourqe goes up and down, more so when its warm. The funny part is the problem is not there at first, then it comes in at cruise speeds only and on partial throttle, more driving and it becomes an evident surge on acceleration. Flick into 2wd and the problem is gone immediatly no matter what the conditions. So its 100% assosiated with the attessa contol not an engine misfire etc.

Under hard acceleration the transfer delivers front tourqe and works perfectly.

I have checked the diagnostics and aparrently everything is fine according to the control unit. So I pulled the mannual out and started working through the problem.

Firstly I have bleed the Attessa hydrolic control and used genuine matic D fluid.

I have changed the transfer case oil and again used genuine matic D fluid, also worth noting is the trasfer opperates normally when front tourqe is required under hard acceleration/ cornering.

I have checked all the speed sensors for continuity back to the control unit and sensor resistance. I have also checked the air gaps between the pick up rings and the sensor tips.

Ive checked the power and ground supplies to the control unit they are all fine.

I have checked the TPS and RPM inputs from the ECM to the contol unit, again they are all fine.

Now this brings me to 2 items. The G sensor OR the control unit.

My thoughts on the G sensor, is it possible for the G sensor to be getting "stuck" in the acceleratinn or deceleration position and be feeding the control unit false information??

A simple check with the mulitmeter will confirm or dispel this and ill be doing it tommorrow.

I know at rest I should have a 2.5 volt referance from the sensor. accelleration it goes up, decel it goes down. I may have that arse about but its late!

So this quick check should rule out the G sensor and point my last resort towards the conrtol unit itself.

Is there anything im missing in this diagnosis that people have come accross before??

And finally split conrollers, most of the ones I have seen simply bend the G sensor referances. Are there any different versions that actually control the pump directly??

If it turns out to be a control unit I think something along these lines would work out to be a more cost effective solution to replacing the control unit.

Also on this particular vehicle all the wheel dimensions are the same 17 by 10's with 40 series rubber.

Brad

Edited by Risking
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ebola Proficient

ebola

Posted
Posted

does it sit at its minimum value when cruising, and flicks under acceleration?

what size are you tyres / rims ? I had that issue when I had to run around for a week with a space saver on. different rolling radius...

Though from your diagnosis, I guess you know that your tyres are all equal. But the next step after rolling radius would have to be abs sensors (the reason rolling radius matters).

rolling radius

rolling radius

I just wanna say rolling radius.. rolling radius rolls off the tongue. radius. rolling radius.

Er.. um... The attesa cpu is very dererministic on how it treats the voltage values. I'm (eventually) going to wire up a semi - fixed option (much lower teck than duncans controller)... eventually... I still have to sand an ugly fibergalss patch... still....

The surging like you describe shouldn't be because of the G sensors, it wouldn't manifest itself that way. Rolling radius (ha - said it again) and abs sensors.

And then hopefully someone who has actually tinkered with it (instead of reading alot) might have an answer.

I'd get to it quick though. How much are new clutch packs? On the plus, when its wet, it absolutley rocks...

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blind_elk Grand Master

blind_elk

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Posted

Are the tyres all the same size, in terms of wear. If not, then you have a different rolling radius - you're right ebola, it's really smooth off the tongue! - front and rear.

If you have replaced only one pair, try swapping them to the other end of the car.

One other possibility is a localised wear pattern on the TPS which may send a variable voltage signal back to the ECU.

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Risking Grand Master

Risking

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Rolling diameters are the same and I have tried 3 different sets of wheels all with matching tires.

Brand new rubber all round so it NOT tires.

Read the post I have checked the ABS sensors and air gaps. Im a certified nissan mastertech so I know what im doing when it comes to diagnosis, ABS sensors were the first thing looked at.

TPS voltages are fine right from closed throttle to full throttle. I have confirmed this via the power FC and also substituting a OEM ECM and using genuine nissan consult II.

I have narrowed the problem down to the G sensor, After driving it hard tonight I have noted that once the G sensor is loaded upon turn in the attessa opperates normally and the guage goes back to 0 untill the vehicle trajectory is straight again.

Turning the sensor 90 degrees it opperates fine in a straight line but surges when cornering.

Ill substitute a sensor out of another one of the GTR's tommorrow and hopefully it will rectify the problem.

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sigsputnik Mentor

sigsputnik

Posted
Posted

>aparrently everything is fine according to the control unit

what does this mean? no flashes? could the control unit be stuffed?

have you tested the resistance and voltage across the control unit/harness/g sensors? could it be that somewhere something is firing the g-sensor with greater voltage?

hope you sort it out mate - my attesa is also stuffed so i do understand :(

btw if you find a spare g sensor, let me know :D

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ebola Proficient

ebola

Posted
Posted

Hey - since I am guessing you will have the multimeter out, do you reckon you could get a mA reading from a G-sensor? I want to know what the minimum current required to consistently detect as an input is... and I don't want to fry the computer or cook the G-sensor voltage regulator

Eventually, to override the lateral sensor at 1-4V by hand... and perhaps to figure out how to put on a little preload. Short spurts only (or when its really wet... I live in Melbourne)

Thanks

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T04GTR Grand Master

T04GTR

Posted
Posted

it is bieing NORMAL it sends torque to the front on aceleration not just wheel spin. this is it anticipating wheel slip.

bare in mind it takes a throttle position input as a main input. not just wheelspin as what most people think.

so driving along in say 3rd gear at around 3k. you floor it and evan befor it comes up on boost the front wheels are already being fed power.

if you think about it. the system has a degree of "lag" in its operation, in the form of relays,pumps,solinoids,actual moving of the fluid and also the slack in the transfercase and front drivelines.

this is the main diferance between 32's and 33/34gtr's the 32's dont run any "preload" on the transfer case clutch. where as the latter is preloaded. to give a quicker responce time.

i know its not very smart,but its job is to asume your about to get up it as soon as you put your foot down.

so dont stess its perfectly normal.

hope that helps ;)

ps... make sure the diagnostic plug is not pluged in. ie bleed mode.

to evan up the rolling diameter

i had a similar problem when i put new tyres on the front and had bald ones on the back. it was fixxed with new tyres on the back.

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Risking Grand Master

Risking

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I know what your saying and im very familair with how the attessa opperates and anticipates however this opperation is not normal. I own 2 R32 GTR's and only one of them has this issue.

Im aware under acceleration there is front tourqe being applied however when cruising there is not meant to be anything and what I am getting is fluctuating to the point of causeing a surge through the vehicle.

I had a line pressure guage on the pump today and its 100% getting front drive and fluctuations in the pressure while cruising. Not little fluctuations either, rather significant ones. When being driven hard the attessa pump works perfectly which tells me the actuator (pump) is okay its a control issue.

I have been over the loom front to back.

Ebola I can do that sometime tomorrow.

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