GR Yaris Inconsistent Boost

Onehp said:
Boost isn't very stable on this car, varies 1psi easily between subsequent pulls, and up to 3 psi possible as temperatures vary during a drive (2psi temp + 1 psi general variance). I log almost every performance drive as it's dead easy with JB4.
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What peak boost pressure are you targeting with the JB4?. Are you reducing boost towards the reline, 7200rpm?.
 
Onehp said:
If it feels slower and boost gauge is lower, it is slower.

This fault we talk about in this thread is intermittent. You could try a ecu reset by taking off the negative from the battery and let it sit for 20min then reconnect. Then ECU will relearn and maybe accept the new AFR readings which the Forge top box changes with a new diameter at thr sensor as documented on their site - too bad you didn't ask before as I was sceptical as soon as I read about that as it causes a mismatch in AFR control strategy between AFR and Lamnda sensor inputs.

If the fault is there all the time, I would run down all the grey vaccum tubing and make sure it doesn't leak anywhere, maybe it got pinched or punctured somewhere during install. If outside air can finds it way into the system just a bit, the wastegate will be fysically impossible to fully close and thus not be able to create full boost. As said if this is the case, this issue will be there all the time.

Hope you can solve it!
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How could they sell this though if it reduces boost (power).

I’ll try the ECU thing
 
Sturesmyg said:
How could they sell this though if it reduces boost (power).

I’ll try the ECU thing
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Try it, hopefully it works. Also try to give some throttle just before full boost comes at higher oil temps, so that the cold oil mapping also works.

PS: wrote wrong in my previous reply to you, tired me, should have been MAF sensor not AFR (not a sensor lol) on two occasions.
 
So from what I’m gathering the solutions are the following:

• Potential TC problem - try driving in expert mode or completely off
• Redline the car/give plenty of throttle a few times
• Reset battery by disconnecting negative for 20min+
• Different 98ron fuel


I’ll be trying all these things in the next few days as I’ve definitely noticed issues with my 1st and 2nd gear. Use to see orange around the boost gauge and now I’m only getting 0.8 bar and not seeing any orange ring.

The weird thing is I felt this initially and because my MST intake was installed incorrectly, while on boost the coupling bursted. Took it to the dealership and they retightened it for me. Car felt amazing and was really pulling (meaning the time from installing the intake to taking it into the dealership, I was having this issue). However after not touching anything in the engine bay since, I’ve gotten this problem. I refuse to accept this is ‘normal’, maybe the mechanic at Toyota didn’t tighten it enough and a clamp is becoming loose again?


I’m taking my car into the dealership in 2 weeks. I’ll see if they’re willing to work on the car with the intake ( I doubt they will) and what diagnosis they come up with. If anyone’s have a permanent fix or king term solution fix please share 🙏
 
I have experienced the same in my 2021 MY Car in South Africa.

Also only 1st and 2nd.

If I have been pottering along in town/city traffic, it appears the first 1 or 2 times I try WOT acceleration in 2nd gear from low revs.

However, if I stay on it for a couple of shifts the problem disappears.

For me, I wonder if it is temperature related , either Coolant or Oil temp. It is more noticeable when the oil temperature is below 100°C.

Alternative I have thought about is that the ecu thinks it knows when you are in a relaxed mood and do not want a hooligan response from the car in low gears, and the aggressive driving switches it over into full hooligan mode.

I would love to know the scientific answer someday.

Sent from my SM-S911B using Tapatalk
 
When you say stay on it for a few shifts, do you mean WOT 1st, 2nd and 3rd, then downshift and do it over again?

Temperature could be a possibility, I’ve noticed the car gets up to temperature within 20 minutes or so and I never do anything until the cars at operating temps. In saying that, I use to be able to go WOT in 2nd gear and would see the orange circle if I’m trying to overtake someone. Boost was there and felt safe knowing I could overtake someone. Now just feels so slow

The ecu shouldn’t ‘cap’ low gears that much though, again if you have to overtake someone, and you’re WOT then the car should respond as such
 
I have also experienced this inconsistent boost, felt it and noticed on boost display gauge.

*it could be fuel related as here in Australia two reputable Toyota GR dealers mentioned the GR being very fussy about fuel quality and have recommended BP 98 only, mind you i only use this fuel and hasn't solved the problem.
*In my case, i don't believe it is traction related as i have experienced different levels of boost on completely dry roads on a warm day with warm tyres, can't be traction with AWD and sticky pilot sport 4S tyres.
*Tried disconnecting battery for 20 mins, made no difference.
*Tried full throttle bursts, help sometimes but not repeatable or consistent.

Interestingly i have owned two GR Yaris's for over 2 years and one of them always feels quick with strong boost, the other one feels as quick about 30-40% of the time, other times it feels noticeably slower and almost like a NA engine. I can take either car out on the same day, so same weather, same roads, same fuel etc one always feel quick the other only sometimes. ???

I believe it must be something the ECU is doing, they seem to be very fussy and might be limiting boost timing etc God knows why?

PS. both cars a completely stock.
 
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rob said:
I have also experienced this inconsistent boost, felt it and noticed on boost display gauge.

*it could be fuel related as here in Australia two reputable Toyota GR dealers mentioned the GR being very fussy about fuel quality and have recommended BP 98 only, mind you i only use this fuel and hasn't solved the problem.
*In my case, i don't believe it is traction related as i have experienced different levels of boost on completely dry roads on a warm day with warm tyres, can't be traction with AWD and sticky pilot sport 4S tyres.
*Tried disconnecting battery for 20 mins, made no difference.
*Tried full throttle bursts, help sometimes but not repeatable or consistent.

Interestingly i have owned two GR Yaris's for over 2 years and one of them always feels quick with strong boost, the other one feels as quick about 30-40% of the time, other times it feels noticeably slower and almost like a NA engine. I can take either car out on the same day, so same weather, same roads, same fuel etc one always feel quick the other only sometimes. ???

I believe it must be something the ECU is doing, they seem to be very fussy and might be limiting boost timing etc God knows why?

PS. both cars a completely stock.
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That is very interesting, like scientific research! Definitely something going on then.

I think the inaccurate pneumatic wastegate control is a bit hit and miss and might be the source of our woes. I haven't had any problems since slightly* ramping down boost demand mid range with my programmable box, obviously not an option for a stock car....
What if everybody with issues files a formal complaint with their dealer, maybe something happens eventually, it's part of Toyotas product improvement strategy to count complaints when prioritizing what to fix (I used to work in automotive applying their system)

Too bad it doesn't have imho modern electronic/servoed WG control...

* very sensitive, talking about ballpark 0,01bar adjustments
 
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rob said:
I have also experienced this inconsistent boost, felt it and noticed on boost display gauge.

*it could be fuel related as here in Australia two reputable Toyota GR dealers mentioned the GR being very fussy about fuel quality and have recommended BP 98 only, mind you i only use this fuel and hasn't solved the problem.
*In my case, i don't believe it is traction related as i have experienced different levels of boost on completely dry roads on a warm day with warm tyres, can't be traction with AWD and sticky pilot sport 4S tyres.
*Tried disconnecting battery for 20 mins, made no difference.
*Tried full throttle bursts, help sometimes but not repeatable or consistent.

Interestingly i have owned two GR Yaris's for over 2 years and one of them always feels quick with strong boost, the other one feels as quick about 30-40% of the time, other times it feels noticeably slower and almost like a NA engine. I can take either car out on the same day, so same weather, same roads, same fuel etc one always feel quick the other only sometimes. ???

I believe it must be something the ECU is doing, they seem to be very fussy and might be limiting boost timing etc God knows why?

PS. both cars a completely stock.
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Interesting… have you been to the dealership within your 2 years of ownership? Have Toyota done or said anything about fixing the issue or even just resolving what the issue might be? Surely you haven’t just accepted this and been dealing with it?

Super frustrating I can imagine and I’d hate to waste my time going to the dealership just for them to know no better than I do… which is fvck all!!

Plus I’m worried if I get another mechanic to look at the car it’ll void warranty - Toyota seem to be very picky with their requirements
 
Onehp said:
That is very interesting, like scientific research! Definitely something going on then.

I think the inaccurate pneumatic wastegate control is a bit hit and miss and might be the source of our woes. I haven't had any problems since slightly* ramping down boost demand mid range with my programmable box, obviously not an option for a stock car....
What if everybody with issues files a formal complaint with their dealer, maybe something happens eventually, it's part of Toyotas product improvement strategy to count complaints when prioritizing what to fix (I used to work in automotive applying their system)

Too bad it doesn't have imho modern electronic/servoed WG control...

* very sensitive, talking about ballpark 0,01bar adjustments
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New car and they’re putting in an ancient piece into the car… my 2012 had a pneumatic WG and it never had this issue. I guess they’re trying to cut costs but man this is bloody annoying.

Once I see the dealership in 2 weeks I’ll report everything they’ve told me. I have a feeling they’ll either say I need to put stock air box back in before they can proceed with anything OR they’ll tell me they have no idea what’s going on and charge me an arm and a leg to “investigate”
 
When I brought the issue under my dealers attention, they said they had 1 previous complaint - that turned out to be fuel quality.

I only fill with 1 brand, at 2 stations of which the 1 is at my dealer... So I am not convinced.



Sent from my SM-S911B using Tapatalk
 
Francois Kriel said:
When I brought the issue under my dealers attention, they said they had 1 previous complaint - that turned out to be fuel quality.

I only fill with 1 brand, at 2 stations of which the 1 is at my dealer... So I am not convinced.



Sent from my SM-S911B using Tapatalk
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Interesting, I have read that fuel might affect the car, have you tried to put any octane booster in the car?
 
“Fuel quality” is just a bullshit excuse to get you off their property. I wouldn’t waste any time on exploring it.

Unless the fuel is obviously and seriously aged/tainted (surprisingly rare) then the car should handle it just fine, as almost every other car on the road does.

If there’s something up and it’s intermittent then the wastegate, a sensor, or something ECU-related is the most likely culprit. As it only seems to affect certain cars then we can probably rule out the ECU though.
 
Duke said:
As it only seems to affect certain cars then we can probably rule out the ECU though.
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Or, the ECU programming is not capable to deal with the real world variations in how the hardware responds - that, or said harfware has too large variations. Something like that.
 
Would a remap sort the boost issue?

I realise that's a last resort for most people due to warranty etc.

Other people have mentioned a forge inlet.
 
Took the car to a well trusted mechanic and one of two thing could be happening,
1. Fuel quality genuinely might just be shit and I got a bad batch of 98. If I refuel next time and I still have an issue then it’s;

2. Wastegste that’s gone bad. Car should still be under warranty unless Toyota have already flagged my car as voided warranty due to intake when I took it in for a service.


I’ll keep everyone’s here posted to see how the visit to the dealership goes in 2 weeks time. I have a feeling it’s the latter
 
Get the VIM and GTS and check the "Knock Correction Learning Value". If everything is normal, the number should be 24.
If the number is less than 18, boost is limited.
As the knock signal accumulates, the number will drop.
Possible causes include "low octane gasoline," "poorly drained muffler," "carbon buildup in the combustion chamber," "noise in the electrical system," etc.

If the "Knock Correction Learning Value" is 24, but boost is still limited, another cause could be the various temperature corrections.
The surge tank needs to be cooled before launch because higher intake air temperatures will limit boost.

Or, if the various sensor readings are inconsistent, the system may misdiagnose a malfunction and limit boost.
Disturbed airflow signals due to a low-quality intake kit,
or disturbed pressure sensors due to a high quality intercooler.

Disconnecting the battery may not be sufficient to relearn the ECU; a reset by GTS is required.
 
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