STX550 V9X Boost loss going up hill at 20psi

[Belly65]

Hi I'm lost with this one.
When I drive up a steep hill at 80 kph as soon as boost reaches 20 psi the boost flutters sounding like a blow off valve of boost hose leak.
New parts fitted
All new plazmaman turbo pipes in and out of inter cooler.
New oring seals on OEM connections
New clamps
Reasonable new intercooler.
Catch can
No oil leaks on boost lines or intercooler.
All vacuum lines replaced.
Turbo checked by turbo tech as ok,
Suction control valve replaced 2 years ago genuine.
Boost controller new genuine.
Vacuum operated valve on turbo moves freely.

Only happens under load either towing or going up a hill at 20psi.

Can anyone suggest any that might be worth checking please

 

[Old.Tony]

It sounds like the ECU is tripping up on the high boost level (mine does it if I set my Tillix valve too high, my ECU doesn't control the turbo any more).

Thing is - with mine, and possibly with yours - my boost levels were once higher, the ECU is getting upset at lower levels. I used to see peaks of 23psi and now if my boost passes 21psi for some reason the engine falters, drops power and shows vacuum instead. I can't decide if it's a bad boost sensor or something else (perhaps an electrical glitch?). I've back my Tillix valve off to reduce my peak boost levels to 19psi and the car seems happy enough, but I've got a new BCS and some new vac hose which I want to throw at it and see if it improves things.

I have no time to do look at this before Friday at least, and I've got an alternator rebuild on my motorcycle to do too (I can take it for short rides, but the rotor has a broken wire in it).

 

[Belly65]

It sounds like the ECU is tripping up on the high boost level (mine does it if I set my Tillix valve too high, my ECU doesn't control the turbo any more).

Thing is - with mine, and possibly with yours - my boost levels were once higher, the ECU is getting upset at lower levels. I used to see peaks of 23psi and now if my boost passes 21psi for some reason the engine falters, drops power and shows vacuum instead. I can't decide if it's a bad boost sensor or something else (perhaps an electrical glitch?). I've back my Tillix valve off to reduce my peak boost levels to 19psi and the car seems happy enough, but I've got a new BCS and some new vac hose which I want to throw at it and see if it improves things.

I have no time to do look at this before Friday at least, and I've got an alternator rebuild on my motorcycle to do too (I can take it for short rides, but the rotor has a broken wire in it).

I'd Rather fix the bike, I tried a boost controller of another V9X that runs perfectly, problem was still on mine.
Could the suction control valve have anything to do with this ?

 

[Old.Tony]

I'd Rather fix the bike, I tried a boost controller of another V9X that runs perfectly, problem was still on mine.
Could the suction control valve have anything to do with this ?

Yes I would rather fix the bike but since shops are 50km from home, I need a car that can carry my fridges so I can bring food home.

The SCV doesn't have any reliance on the boost pressure, except that when your boost pressure is high, your fuel flow rate is usually high and so (coincidentally) the SCV may be involved and affecting the engine. Sometimes injector cleaner will fix this, sometimes the SCV is damaged and needs to be replaced but since the injector cleaner is never BAD for the engine, I always recommend giving that a go first (I might grab some myself tomorrow while I'm in town).

My usual go-to seems to have changed, it used to be a "Fuel System Treatment" and is now a "Fuel System Cleaner/Conditioner" at double the price. Tough, I'll throw it in and see how it goes, it's not like I do this every tankful.

https://www.supercheapauto.com.au/p...conditioner-500ml/325542.html?cgid=SCA8004635

 

[Belly65]

Yep I agree, I've tried the fuel treatment,

 

[landmannnn]

One thought that may or may not help... 80kph is exactly when the first stage of the torque converter locks up.
It is possible that you are at exactly the point where the transmission can't decide whether to lock up or not.

The fluttering might be the TC lockup cutting in and out. Note the transmission also controls the turbo to supposedly smooth out gearchanges, so it might be a double whammy!

 

[Belly65]

One thought that may or may not help... 80kph is exactly when the first stage of the torque converter locks up.
It is possible that you are at exactly the point where the transmission can't decide whether to lock up or not.

The fluttering might be the TC lockup cutting in and out. Note the transmission also controls the turbo to supposedly smooth out gearchanges, so it might be a double whammy!

That's very interesting, it is around 80kph at 20 psi, if I move the shifter across and go down a gear it doesn't appear to be a problem, if I leave it in drive and go over 80kph the fault isn't a problem, no codes come up at all. Definitely worse towing even a empty trailer.
Transmission is serviced every 100000 klm so twice now.

How would I test this theory?

 

[Old.Tony]

^ If the TCC isn't locking up smoothly an experienced auto transmission mechanic with his workshop tool plugged into your car while driving will be able to tell.

 

[landmannnn]

That's very interesting, it is around 80kph at 20 psi, if I move the shifter across and go down a gear it doesn't appear to be a problem, if I leave it in drive and go over 80kph the fault isn't a problem, no codes come up at all. Definitely worse towing even a empty trailer.
Transmission is serviced every 100000 klm so twice now.

How would I test this theory?

In some ways you have just tested the theory... You are not the first to have noticed the weird goings on at dead on 80kph as the TC locks up.

Yes, it appears to be more noticeable when under load, next time you are out driving normally, deliberately hover at 80 and you will probably see the rev counter dropping 300rpm and raising again if you lift off very slightly.

So nothing to worry about. Put it down to bad coding by Nissan and their mates at Jatco. Anecdotally they might have tweaked the code in about 2013 to reduce the effect.

 

[landmannnn]

Have a read...a lot of work from Nissan and Jatco went into this tranny.

(As well as Navara, I have had 2 Infinitis with this transmission, a V6 diesel and a V6 petrol, these both seemed much smoother and more responsive than the Navara. I guess the Infiniti techs get paid more than the Nissan ones)


RE7R01A Transmission / JR710E / RE7R01B Transmission Overview
First introduced for the 2009 model year in the Nissan 370Z, InfinitI FX and Infiniti G series, the RE7R01A transmission is a 7-speed automatic manufactured by Nissan’s transmission subsidiary Jatco. Also known as the Jatco JR710E transmission, this gearbox features 4 planetary gear sets, 3 multi-plate clutch packs, 4 multi-plate brakes, and 2 sets of one-way clutches.

Unlike many transmissions, the Nissan / Infiniti RE7R01A transmission uses partial torque converter lockup between gear changes to reduce harshness. To achieve this, the RE7R01A / JR710E modulates the applying pressure with the torque converter clutch control valve and torque converter clutch solenoid (they refer to this as Smooth Lockup Control). To further enhance the smooth operation, the line pressure behind each clutch is adjusted to match the engine force and vehicle speed.

RE7R01A Transmission Features
RE7R01A Adaptive Shift Control – The TCM can automatically change the shift program from Standard, Power, Uphill and Downhill depending on the gas pedal position, engine RPM, braking and other parameters. In the Uphill shift program, the transmission will stay in 4th, 5th or 6th to prevent it from “hunting for a gear”. In the Downhill program, the TCM will automatically downshift to provide engine braking.

Nissan Rev Matching – Jatco calls this feature Synchronized Revolution Control, and it reads the various vehicle speed, braking and RPM parameters to determine whether a downshift is about to occur. It can then tell the ECU to briefly increase the engine RPM to provide a smooth heel-and-toe like downshift.

 

[Belly65]

Have a read...a lot of work from Nissan and Jatco went into this tranny.

(As well as Navara, I have had 2 Infinitis with this transmission, a V6 diesel and a V6 petrol, these both seemed much smoother and more responsive than the Navara. I guess the Infiniti techs get paid more than the Nissan ones)


RE7R01A Transmission / JR710E / RE7R01B Transmission Overview
First introduced for the 2009 model year in the Nissan 370Z, InfinitI FX and Infiniti G series, the RE7R01A transmission is a 7-speed automatic manufactured by Nissan’s transmission subsidiary Jatco. Also known as the Jatco JR710E transmission, this gearbox features 4 planetary gear sets, 3 multi-plate clutch packs, 4 multi-plate brakes, and 2 sets of one-way clutches.

Unlike many transmissions, the Nissan / Infiniti RE7R01A transmission uses partial torque converter lockup between gear changes to reduce harshness. To achieve this, the RE7R01A / JR710E modulates the applying pressure with the torque converter clutch control valve and torque converter clutch solenoid (they refer to this as Smooth Lockup Control). To further enhance the smooth operation, the line pressure behind each clutch is adjusted to match the engine force and vehicle speed.

RE7R01A Transmission Features
RE7R01A Adaptive Shift Control – The TCM can automatically change the shift program from Standard, Power, Uphill and Downhill depending on the gas pedal position, engine RPM, braking and other parameters. In the Uphill shift program, the transmission will stay in 4th, 5th or 6th to prevent it from “hunting for a gear”. In the Downhill program, the TCM will automatically downshift to provide engine braking.

Nissan Rev Matching – Jatco calls this feature Synchronized Revolution Control, and it reads the various vehicle speed, braking and RPM parameters to determine whether a downshift is about to occur. It can then tell the ECU to briefly increase the engine RPM to provide a smooth heel-and-toe like downshift.

Ok , I've tried shifting the trans to 5th gear going 80kph up same hill and the problem doesn't appear. So unless I can work out a way to adjust this I'll just manually shift to reduce the lugging feel on the trans, problem gone. For now

 

[landmannnn]

I guess a fair amount of 80kph speed limits where you are? 80kph/50mph is not a common speed limit in most countries.

 

[Belly65]

Yes I would rather fix the bike but since shops are 50km from home, I need a car that can carry my fridges so I can bring food home.

The SCV doesn't have any reliance on the boost pressure, except that when your boost pressure is high, your fuel flow rate is usually high and so (coincidentally) the SCV may be involved and affecting the engine. Sometimes injector cleaner will fix this, sometimes the SCV is damaged and needs to be replaced but since the injector cleaner is never BAD for the engine, I always recommend giving that a go first (I might grab some myself tomorrow while I'm in town).

My usual go-to seems to have changed, it used to be a "Fuel System Treatment" and is now a "Fuel System Cleaner/Conditioner" at double the price. Tough, I'll throw it in and see how it goes, it's not like I do this every tankful.

https://www.supercheapauto.com.au/p...conditioner-500ml/325542.html?cgid=SCA8004635

Hi Old Tony, still fighting the boost issue, I've found something interesting. When going up the hill where I encounter the boost problem I have found that if I shift the auto selection to sports and select 5 gear I do not have the boost problem at all.
I've turned around and gone up the same hill in D and I have the boost loss at 20 psi. It seems that the transmission isn't dropping down gears and it's lugging the engine that causes the boost fluctuations at 20 psi. Both tests were performed at 80 kph. Any suggestions?. Transmission has been serviced, this problem appeared way before 100000 klm and was still there after the service.

 

[Old.Tony]

Could the load sensor in the gearbox be causing the issue? Perhaps. Needs to have an auto trans specialist doing it with their workshop tool connected to the car. They can tell what the gearbox thinks it's doing, the tool can dig all sorts of info out that we mere mortals don't have access to.