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If it's not really about tuning or wiring. Then it belongs in here.
= Resolved threads
Hi,
I am new to this forum, we have contacted Marcin and he told us to post here our case study because we have some ideas but maybe you can help us a bit more.
We have a toyota Gr Yaris (same engine as GR corolla), which has been forged, has a closed deck, balancing shaft removed (The guys at lamspeed built the engina, and removed it because they say that it introduces harmonics past 7500RPM) and ARP head studs. It has an Xshift sequential gearbox with an MME air shifter and a G30-770 .61 AR turbo and a syvecs ECU. We are using R2558E-10 spark plugs:
This turbo has been used by lamspeed to run on timeattack and drag racing sucessfully with E85 fuel and (as they said) had no issues at all with it. We need to use pump gas here since no E85 is available on pump. (we have 98 RON only here but the quality is good and the octane rating is consistent all year and country around),
We have put everything together, did 3000miles as brak in at wastegate pressure, increasing RPM each 300 miles until redline (8000RPM) wihtout issues at all.
Then we did the car mapping, we aimed for absolute 0 knock we used conservative timing and a bit rich mixture just to test it out and run it for some more miles before taking out all from it. (see log 2024-11-13 15-33-29 plus 0h00m00s S8#20403). This log is for a 4 gear run, the knock events are the shifts from the gearbox engaging without clutch.
After 100km, the turbo went out and a spark plug porcelain broke next to the electrode:
Turbo:
We took everything apart and found 2 clogged injectors after flow testing them (we have flow tested them before installation and were perfectly balanced) and thought that this is what caused the issue.
Then we installed 3 EGT probes one in each runner additionaly to the one after turbo that we already got just to catch EGT imbalance and trigger an error to the screen just to notify the driver to release throttle and check if there is any issue. And installed new turbo, new injectors and fixed two valves and valve seats that got damaged during the event.
After putting all the engine together again and recheck tune, the same thing happened again (On different cylinder), but the spark plug broke and the turbo broke the same exact way. It lasted like 100 miles. We had an issue with the oil temperature sensor and the car thought that was cold and issuing a rev limiter at 5000RPM, with this event the wastegate got stuck open with a piece of the turbo (See log 2024-11-14 18-47-54 plus 0h00m00s S8#20403) here clearly you can see the rev limiter engaging and the boost pressure dropping due to the WG stuck open.
We are seeing 950ºC EGT temperatures before turbo. They look a bit high for a "mild" tune maybe. The timing has room to advance more and the turbo has also room, now is doing 500HP and we have been able to push it to 650HP.
The Log 2024-11-13 15-34-41 plus 0h00m00s S8#20403 is another 4 gear launch before it broke again.
Now we have 2 theories:
1. The spark plugs are breaking due to vibrations and the fallen piece is impacting the turbo and breaking it
2. The .61AR is too small and everything heat soaks, the turbo gets melt and the engine is pre igniting due to a too hot spark plug and combustion chamber. This does not happen to the other guys since the are using E85 which cools everything a lot more.
We have no idea which of this 2 is true and we would like to be sure before putting it together again a thrid time to not break everything again.
Sorry for the big post but I found no other way to be able to explain everything in detail and be the most accurate possible, for sure I'm missing anything if you need more information or pictures, please ask me for them.
Thanks a lot for you time and help!
P.S.: You can download syvecs SCal software to see the logs here: https://www.syvecs.co.uk/forum/viewtopic.php?f=8&t=122&sid=ea2174f4b529c46b7779b5a0862148f7
Attached Files
Syvecs-logs.zip
Hi,
Here we have two more pics of the turbine carnage:
Thanks a lot!
I'm only on an Android device and don't have a good personal laptop accessible right now to load the Syvecs software.
Could you throw up a screen shot or list peak boost operating parameters for people to see?
Definitely not showing knock on load?
Is that running significantly above factory boost levels?
Do you have good fuel filtration? Assume you are still running the factory high pressure pump and injectors?
I would imagine if they are genuine plugs that they would only be breaking porcelain with extreme heat or knock. If it was just heat you might expect the strap to bend or the weld to fail.
That's the tightest turbine housing that comes on the G30, with a sequential box you might find you are far better off going to a G35 turbine or at least one of the larger G30 turbine housings to reduce back pressure and heat.
I think I recall a thread elsewhere with similar turbo failures, it was temperature related.
Hi,
Thanks a lot for the reply, yeah 0 knock on load.
In stock form this engine works about 1.6-1.8 bar, now is working between 2-2.5
We have installed a ID750 fuel filter inline witht the stock fuel filter and aftermarket port injectors. Direct injection is 100% stock.
They are genuine NGK bought directly from an authorized reseller.
The problem with going to a bigger turbine is that for the little 1.6 engine is too big, the powerband gets too high. We are thinking into going to a G30-660 in the next available AR (.83)
Here is the log, you can see the knock on gear shit and the boost going high due to spark retard strategy on shift to remove torque from the engine so it's able to shift smoothly:
That compressor and housing combination may work better. It appears the image is being compressed it's hard to make out. It is probably worth trying the next turbine housing or two up, I have seen feedback from others that threshold and response has actually improved in some applications going up from the smallest turbine housing so it's worth trying.
Is it possible for you to host a full resolution image of the screenshot somewhere?
Hi,
Sorry you can find the full res image here:
On the log IIRC we also have EMAP which is more or less 1:1 with MAP.
Thanks a lot!
Arnau,
It seems you've confirmed excessive EGT, which is to be expected with that engine/turbo combination and fuel at that power level.
Combustion temperature may also be excessive, which may explain other damage.
Reducing boost level so you can run more optimal ignition advance on the pump fuel will bring EGT down significantly. A larger turbine housing will help as well.
On DI + PI a mistake I've seen destroy DI injectors is combusting while DI isn't injecting, so I would verify if that's occurring.
Another common mistake is exceeding DI injection window. What's max EOI under high load conditions?
Next, how are you executing cuts? Fuel or spark cut? how much retard?
What does exhaust pressure spike to during cuts? Are you logging at sufficient rate i.e. 200 Hz to see brief events?
Hi,
Yeah, the combustion temperature is what it explains all the damage alltogether...
The DI is always injecting, here is the table:
0% is 100% DI
The window is adjusted by lamspeed instructions, here are the tables:
Note that this numbers are ATDC not BTDC, syvecs is working this way...
For the cut we do 20 deg ign retard and 50% of fuel cut severity and 50% of ign cut severity:
Regarding the exhaust pressure we had 10HZ setup on the logging, now we updated to 200HZ but here is the data. We also have a damper installed:
Can we relate all the damage to temperature? Does the cut for shift strategy look good?
Thanks a lot for your help again!
Arnau,
SOI looks ok, but EOI is the big concern, so I suggest reviewing it in logs. If EOI isn't logged, you can calculate it from SOI, RPM, IPW. For example 180 degree EOI would complete as the compression stroke starts.
Your cut strategy is concerning since this is a DI + PI engine.
Consider every time you cut DI + PI the DI isn't present on the next cycle, but the PI fuel still travels to the combustion chamber from what was injected on the prior stroke + what strips off port walls. That can result in lean combustion at high load, while the DI injector isn't fueling. That may be damaging the DI injector and engine.
Then when fuel resumes the DI injection delivers fuel straight into the chamber, but the PI injection comes from "far" away, and needs to re-wet walls as well, so your first cycle upon fuel resume may be lean as well.
This concern goes for all cuts for rev limiter, boost limit, shift, etc.
If you're sticking with DI + PI, you'll want a solution to this.
Hi Mike,
Thanks a lot for your detailed answer. We have been talking with the guys at syvecs and they have some strategies built in to avoid this issues:
They told us that it also does some calculations internally to avoid this problems.
Regarding the EOI we are still checking and doing our maths here.
In another hand, do you have any advice about a different cut strategy to avoid this problems?
Thanks again!
Hi Mike, just for those of us playing at home, surely an ecu manufacturer should implement a fuel cut on a DI/PI firmware such that a fuel cut is truly sequential accounting for the sequencing of port injected to cylinder injection over the entire cycle? That sounds like absolute amateur hour if the full intake to combustion cycle isn't considered for fuel cuts in the model?
