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Discussion Starter #1
Hello,

I'm hoping to get some information/advice from those of you running a CT27 turbo, or other similar hybrid with a T04E 46 trim compressor wheel.

I'm currently running one and have started tuning it this week on a Megasquirt ECU.

On Monday I had it boosting up to 22PSI, and the car felt good, however reviewing the datalogs shows that at 22PSI once the engine got above 6000RPM the intake air temps start to rocket up.

The general IAT temperature on the drive was around 100degF, which holds steady at 22PSI up to 6000RPM, but after that point boost drops to 20PSI and the intake temps rocket up to 129degF at 7600RPM. Ambient temp was around 50degF
I expect that I found the limit of the compressor efficiency, but I'd like to confirm:

1. What is the general accepted max PSI a CT27 or similar T04E 46 trim hybrid can run safely?
2. What intake air temp level would be considered too high to be safe?
2. What is a normal intake air temp for an MR2 running an upgraded SMIC?

Any help from experience greatly appreciated.

Thanks
Dan
Screenshot 2020-11-18 235106.png
 

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MAT isnt really a concern... how high is too high depends on a lot of different things.
High MAT, and a tune that cant handle it will cause pre-detonation which is what you really need to be worried about.

I wouldn't call 129degF high though.
On a hot day here in Aus, i'll see 170+. But the tune and fuel can handle it.

Watching waste gate position is a good way to know if you're pushing a turbo too hard.
If its not opening much (or at all), then it'll be stressed.
You can also watch for boost dropping off at the top end.
 

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22 psi is a lot of heat to deal with. But 50ish C isn’t that concerning. I’ve seen 150 F on both my TD06 and EFR 6758 running 17-19 psi. The real factor is how long I’m on boost really, as it seems like once you’ve heat soaked the SMIC, it’s just a question of how much time you spend getting closer to your actual compressor outlet temps. I have wanted to toss an IAT sensor in the hot pipe to check it out. Maybe I’ll do that with a type K TC once I get that all setup.
 

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As other indicate the IAT temp is not really a concern as long as other factors remain in check. I’d review the knock readings when on boost and if you have MS retarding timing enough in the 5k rpm range.

As a precaution I also run sequential fueling by adding 2-4% more fuel to centre cylinders above 18psi.Cylinders 2&3 run hotter than others so best to ensure it’s not lean.

you do not mention internal mods or fuel being run. I do think 22psi is quite high on the 3sgte unless precautions are taken. High octane fuel and conservative ignition are two of those factors. Should be aiming for more air volume rather than high boost pressure. This is difficult to quantify or measure in practice.
Jim
 

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Discussion Starter #5
Thanks for the responses, is anybody running a CT27 and making good power at 22PSI?

Thanks for the tip on adding fuel trim to cylinders 2 and 3 at high boost, I'm running sequential so should be able to do that.

I can give some more info on my specific build.
Fuel: 99-Octane premium pump fuel (UK) (I think this is 95RON in US numbers)
Ignition timing currently is set conservatively as I am planning to set this on Dyno once I have my fuel map fully sorted, currently it's around 10 degrees when up at 22PSI and high RPM
Supporting engine mods: forged rods forged Pistons, 8.7:1 compression ratio, headwork, 264 cams, other mods to support 8kRPM


To be honest I was looking more for the general accepted running range for the CT27 on a 3SGTE as I know in the past they were a well used and known turbo. Is 22PSI generally seen as working them too high and more comfortable 19-20PSI? Any examples of where people have had problems at high boost or good results in a certain boost range etc.
 

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The problem with turbo efficiency is it’s not “good” at one boost level, then “bad” when adding 1-2 psi more. It’s a trend, where I imagine 18-19 psi is already pushing the compressor and turbine fairly hard. You’re probably low on turbine efficiency towards redline, and dropping off compressor efficiency a decent amount of this is a cast T04e 46 trim wheel.

Adding 3-4 psi on top of this is going to push you to lower efficiency for both.

Is this bad? No, if the engine can tolerate it and doesn’t knock its fine. 99% of factory turbo cars made today run very low compressor and turbine efficiency towards redline in an effort to get better low end response. They have enough sensors and safeguards in the ECU to reliably do this.

Be careful with Megasquirt knock sensing. I never got mine to give me realistic/reliable readings.
 

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Discussion Starter #7
Yeah I know, that's precisely why I was asking for actual examples from peoples experience of running CT27's at that peak boost level, to understand real world if there is any concern/tradeoff/benefit of running at this level. Rather than discussing theory.

There's a trade off to be considered, running lower boost with cooler charge temp can allow for more advanced timing and could produce more power than flogging the turbo to max boost with high charge temps and having to back off ignition because of it. Or having to upgrade cooling/adding WI etc. if problems were encountered at this boost on this turbo. I was interested to hear if other people running a CT27 had had similar results and what route they had taken at the dyno and any problems encountered.

Theoretically, this boost level at that RPM on our engine is outside of the efficiency map. I've calculated it and plotted it on the compressor map and can see clearly that 22PSI at 8000RPM on a 3SGTE is beyond the choke point of the T04e compressor, it matches with what can be seen on the datalogs, but I'm hoping to discuss real world examples rather than the theory.

Yeah knock detection isn't working brilliantly with the OEM knock sensor, too many false alarms, need to tune it. But I have a separate Bosch sensor on the block connected to another knock listening device as a safeguard

Thanks
Dan
 

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Why don’t you collect data on your own setup? Someone else’s setup isn’t necessarily that representative of what you’d see. On modified engines it’s likely to differ a lot due to the VE of the engine and other thermodynamic effects like flow/heat losses.
 

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Discussion Starter #9
Why don’t you collect data on your own setup? Someone else’s setup isn’t necessarily that representative of what you’d see. On modified engines it’s likely to differ a lot due to the VE of the engine and other thermodynamic effects like flow/heat losses.
I am collecting data on my setup, I've just posted some of it, I'm currently road tuning my VE table and boost control tables and logging every run, but I can't get a good idea of peak power vs boost vs ignition timing without a dyno. Dyno time is expensive and limited, so that's why I was specifically asking for information from people who are actually running a CT27 turbo, to hopefully understand better what they found out at the dyno in terms of peak boost vs AIT vs ignition timing and power. Surely that is the point of having a forum, so we can share information.

I am very aware that not everybody's engine/setup is the same etc. etc. and clearly I was not going to take one persons information and simply apply it to my car, I was hoping to spark a conversation where information can be shared to build up a general picture of this turbos performance with some technical data behind it.

Probably I should have phrased the question better, but I expect that now the thread won't get any fresh attention or replies.


1. Do you own a CT27 and have you mapped it for peak power on a Dyno?
If Yes,
1.a: Would you mind sharing your Engine/Charge cooling spec and let me know what kind of peak boost pressure you found to be optimal at the dyno considering AIT, Knock, ignition timing and importantly power. Of course I will also share my results once tuning is complete.

If No, then there is really no need to keep responding.....

Thanks
Dan
 
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