GR Yaris Balance of tuning and durability limits

[sixtentouge]

Not sure if something is lost in translation, but this makes no sense to me, as usually pressure ratio has nothing to do with the exhaust side, only the compressor side. Even if it did, I don't understand where the 18psi comes from as 0,5 bar x 2 = 1 bar = 14psi.

I believe I said "psi," but meant pounds... Like 18 pounds pushing the valve off the seat. Sorry for the confusion.

There are many pressure ratios. Compressor PR, turbine PR, or engine PR, which is intake to exhaust. If we're boosting 1.7 bar intake pressure, and assuming an engine pressure ratio of 2:1, because the factory turbine is small and requires twice the drive pressure, that means 3.4 bar EP at 7,000 rpm. 1.7 bar at 7,000 rpm is .5 bar higher than stock. You are correct that that is a 14.5 psi increase. 14.5 psi on a 1.21 square inch valve area is almost 18 pounds.

Hope that makes more sense.

Normally, we get the engine through peak torque, and then pile in the boost to maintain that torque number as the rpm climbs and VE falls. Toyota's strategy on this engine is to retard the boost as the rpm climbs. I haven't measured exhaust pressure for the G16E, and likely never will, but it's a safe bet that this strategy is to keep the EPR (engine pressure ratio) in check. I'll bet it skyrockets as the rpm climbs. At 1.7 bar at 7,000 rpm, I'd put money on it nearing 3:1.

 

[sixtentouge]

but do you think they're garbage for all applications?

No. Used in the right application, they work fine. Problem is, a lot of hybrids just increase compressor wheel size and bore the housing to fit, then just "clip" the exhaust wheel in an attempt to keep the EPR in check, but inevitably, it's a lot worse. Turbine a/r is unchanged, turbine inducer and exducer are unchanged.

For an inexpensive bump in power, there's nothing wrong with it, as long as you know what you're in for. It's choking the crap out of the engine to force that gain in HP. Up against a properly sized turbo...you get the picture.

I don't know what's done to the hybrid coming out of Japan, but pretty sure (80%) I know who does the mod... They sent me all of their build-up and modification welding for decades, until I just couldn't live with being associated with that level of hackery...

 

[micsub]

Minus the valve stem, the stock exhaust valve has an area of roughly 1.21 square inches.

Logging the stock boost curve, it seems to mostly go to around 1.7 bar by 4,000 rpm and then the ECU pulls it back to about 1.2 bar by 7,000 rpm. Changing the target to maintain 1.7 out to 7,000 rpm will (just rough calculations) decrease valve seat pressure by 18psi if we assume a 2:1 turbo pressure ratio. If a "tuner" is taking the boost up to 2 bar, that's a .8 bar increase in boost. Again, assuming a 2:1 PR, that's 1.6 bar increase in EP, or 28psi less valve seat pressure. This is why, IMO, so-called hybrid turbos are garbage. On an efficient race engine, I look for absolutely no higher than a 1.5 PR. Using teh stock exhaust housing and just putting bigger wheels in it can send the PR to the moon. I've been building engines professionally since the 1990s. SAE member...yadda-yadda.

The Kelford standard springs are 87lb. on the seat, and I assume the stock springs are quite a bit less. While boost won't affect separation over the nose of the cam, it will certainly affect valve bounce on the seat when closing (float).

Exhaust pressure on the valve is an issue in turbo engines. With bucket followers, it's just a loss in power. With non-shaft-mounted followers, it can have disastrous effects, as the follower can "jump" off the valve or pivot. Any kind of misfire that lights in the exhaust (like when "tuning") and it's game over.

This here seems to be the answer to avoid disaster due to valve float :

 

[Onehp]

I believe I said "psi," but meant pounds... Like 18 pounds pushing the valve off the seat. Sorry for the confusion.

There are many pressure ratios. Compressor PR, turbine PR, or engine PR, which is intake to exhaust. If we're boosting 1.7 bar intake pressure, and assuming an engine pressure ratio of 2:1, because the factory turbine is small and requires twice the drive pressure, that means 3.4 bar EP at 7,000 rpm. 1.7 bar at 7,000 rpm is .5 bar higher than stock. You are correct that that is a 14.5 psi increase. 14.5 psi on a 1.21 square inch valve area is almost 18 pounds.

Hope that makes more sense.

Normally, we get the engine through peak torque, and then pile in the boost to maintain that torque number as the rpm climbs and VE falls. Toyota's strategy on this engine is to retard the boost as the rpm climbs. I haven't measured exhaust pressure for the G16E, and likely never will, but it's a safe bet that this strategy is to keep the EPR (engine pressure ratio) in check. I'll bet it skyrockets as the rpm climbs. At 1.7 bar at 7,000 rpm, I'd put money on it nearing 3:1.

You are right, this is what I meant with backpressure from exhaust side should play a role in when float happens. Better data needed or be safe and upgrade...

 

[Gazooracingyaris]

I had a post on the other place called "my tuning odyssey" but as I am mostly just on here I'll continue my journey here.

My car currently has the following performance related mods...
Kelford Valve Springs
Kelford Camshafts (EZP)
Turbo back Exhaust with 100CEL Cat
Forge Intake duct guide (standard intake box)
Pumaspeed Intercooler with larger diameter pipes
Mishimoto 10 row oil cooler
OEM ECU tune on Dimsport Software.

I use the car for the local Time Attack series and for Sprint/Hillclimb mostly and the occasional thrash with my friends.

One thing I've struggled with has been the car not achieving better speeds on the straights despite showing more power on the dyno so it is something we are continuing to look at this. Part of the issue is we get hot temperatures (30C air temps and 70% humidity) so it's important to factor that in to consideration of lap times and performance between events.

Since the first tune I installed the Forge intake which saw a significant improvement on my speeds down the straights.

I recently negotiated support from Kelford and got the cams and springs sent over to me from Kelford and then installed them with a view to getting the car re-tuned.

Below you can see the impact of the cams and springs.

We did basically worked with the car to max the turbo out then tailored everything else around that. We made about 15 runs as the day progressed and consistently got 185-190kw at the wheels (all 4, not in front wheel drive). Some of the limits were lifted based on the tuner working with the GR Corolla and looking at where the safeties are set way higher than even the tune on my GR Yaris.

One thing we noticed was after the turbo (and of course power) was dropping off was that the GR Corolla runs way more ignition timing than the GR Yaris but without knowing more we were reluctant to match the mapping until we know more..., we've also been discussing options with how to have the power sustain after peak which we know from these conversations behind closed doors is possible.

Anyway here's the result of the cams and valve springs (plus appropriate retune). The peak number is irrelevant, what is important is the gained area under the graph. My tuner did tell me I'd be better aligning the torque and power graph "upslope" ontop of each other for a true comparison as the likely reason for there being a difference is down to how hard the car is strapped down, temperature in the booth, tire pressures and even wheel alignment (toe out etc). For the purpose of sharing the info though I think you can see the gain without me manipulating the lines as they're pretty close anyway.

 

[Michael Knight]

one build GRC engine gone, 3rd piston exploded?

 

[Onehp]

Upgrading to GRC/mk2 pistons doesn't make them bomb proof then (of course not)...

 

[Michael Knight]

Upgrading to GRC/mk2 pistons doesn't make them bomb proof then (of course not)...

Apparently there is gaps still what is safe and what is not in terms of component fatigue, tuning and maintenance.

 

[Greenthumb]

Upgrading to GRC/mk2 pistons doesn't make them bomb proof then (of course not)...

Now that it has been found out that the "upgrade valve springs" from the GRC are more likely to be classified as marketing blah blah. If you're going to install reinforced material to make the engine bulletproof, then do it with aftermarket products.

 

[Florens]

I think it was pretty obvious from the get go that an OEM upgraded engine wouldn't be as strong / durable as high end aftermarket parts.
However there doesn't seem to be a real consensus yet as to how far you can exactly push the new internals "safely".
I feel like there is no sense in upgrading your internals with stuff that isn't "the best".

 

[Onehp]

Now that it has been found out that the "upgrade valve springs" from the GRC are more likely to be classified as marketing blah blah. If you're going to install reinforced material to make the engine bulletproof, then do it with aftermarket products.

That's the main point really, see some writing they gonna upgrade with mk2 pistons and springs, but really if you're going to open the engine, throw in all the best aftermarket parts you can afford...

 

[MRA3]

I think raising the rpm limit over stock form you’re risking a lot of vibrations, harmonics and all related stuff happening and multiplying the changes of destroying the engine…

 

[Sam]

One should only ever expect OEM hardware to support OEM use cases for OEM warranty lengths.

 

[Michael Knight]

FYI people, Toyota launched 2 TSBs (Technical Service Bulletins) a couple of days ago. Attaching the PDFs.
One is for the AWD ECU - to address the overheating issues a lot of people have been experiencing, another one is to replace an engine mount due to people reporting excessive vibrations between 2000-2400 rpm (there will be a temporary fix, and the new engine mount will be released in late 2023/early 2024)

Anyone have these fixed? Getting the engine mount fixed in mid May during service visit.

 

[Onehp]

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Gearbox input shaft failing. Worse for sure with higher torque, revised is 24mm vs 20mm making it at least 50% stronger...

 

[Onehp]

Just saw this, 8 month old on yt, not sure when recorded.
- Transfer box failure on Boss. I've locally heard from new rally car with restrictor to do the same
- Revolution brake failure, no cause given
- On engine comments, it appears they ran the 58.1 on 2 bar ish and stock valve springs, as he comments they opened the engine to change springs and it looked fine? These comments keep confusing me... Wondering if there are more insights on valve float, when it happens (what boost and rpm) and importantly, with what bolt-on hardware...

 

[Michael Knight]

Just saw this, 8 month old on yt, not sure when recorded.
- Transfer box failure on Boss. I've locally heard from new rally car with restrictor to do the same
- Revolution brake failure, no cause given
- On engine comments, it appears they ran the 58.1 on 2 bar ish and stock valve springs, as he comments they opened the engine to change springs and it looked fine? These comments keep confusing me... Wondering if there are more insights on valve float, when it happens (what boost and rpm) and importantly, with what bolt-on hardware...

note that rally car have heaps of mid torque even they have the restrictor. so they can have 500Nm or so even with less top end hp.

 

[MarkoS]

Just saw this, 8 month old on yt, not sure when recorded.
- Transfer box failure on Boss. I've locally heard from new rally car with restrictor to do the same
- Revolution brake failure, no cause given
- On engine comments, it appears they ran the 58.1 on 2 bar ish and stock valve springs, as he comments they opened the engine to change springs and it looked fine? These comments keep confusing me... Wondering if there are more insights on valve float, when it happens (what boost and rpm) and importantly, with what bolt-on hardware...

Think @AdrianoJamesPiras speaks about brake failure in this video

 

[tonic]

one build GRC engine gone, 3rd piston exploded?

They mentioned using Royal Purple HPS 5W-30. The calcium content in this oil is in 3000s, but ideally, you'd want it to be less than 1500 to prevent LSPI from occurring. Not saying that's the main reason, but it could have played a role.

 

[Sekred]

Oh Dear, not again,