Help Understand GTT Boost Setup

[Kinkstaah]

Auto is at least 10% (from my real, actual experience with different torque converters and manual on the same setup)

~185rwkw at 11.6psi (peak!) is entirely what one would expect without a FMIC or anything else on the intake, it does bleed off towards the higher RPM so it's what, 9psi there?

Note: There is nothing that can be done about this with a manual boost tee. If you want to hold it steady and gain more top end, well - You will need electronic boost control.....

[DraftySquash]

On 17/2/2025 at 9:19 PM, Kinkstaah said:

Auto is at least 10% (from my real, actual experience with different torque converters and manual on the same setup)

~185rwkw at 11.6psi (peak!) is entirely what one would expect without a FMIC or anything else on the intake, it does bleed off towards the higher RPM so it's what, 9psi there?

Note: There is nothing that can be done about this with a manual boost tee. If you want to hold it steady and gain more top end, well - You will need electronic boost control.....

Yeah that was kind of the same feedback my tuner gave me. 
the boost tee is until I can sort out my plan for the electronic boost controller and what I’d get, where I’d mount the dash etc. 

I’m happy with this until I can figure it out. Not a big fan of the A-pillar gauges. I’d like to get a clean install of the boost gauge - something digital like GFB. 

Something like that might fit neatly where the ashtray is and look clean. I feel like replacing the OEM triple gauge is a bit extreme for a weekender like my skyline. And it’s not making crazy power to need all the additional sensors/gauges. 

[Milkmun]

Glad it all went smooth. How long did the tuning process take?

[DraftySquash]

On 17/2/2025 at 10:00 PM, Milkmun said:

Glad it all went smooth. How long did the tuning process take?

It was roughly 3.5 hours. 
 

car went in around 11:00 and I was done around 2:30

He did the initial runs, install the BC and then Nistune install and tune. 
The best part was sitting in the lobby and hearing the skyline on full throttle at the dyno 😂😂

[joshuaho96]

12 hours ago, DraftySquash said:

Yeah that was kind of the same feedback my tuner gave me. 
the boost tee is until I can sort out my plan for the electronic boost controller and what I’d get, where I’d mount the dash etc. 

I’m happy with this until I can figure it out. Not a big fan of the A-pillar gauges. I’d like to get a clean install of the boost gauge - something digital like GFB. 

Something like that might fit neatly where the ashtray is and look clean. I feel like replacing the OEM triple gauge is a bit extreme for a weekender like my skyline. And it’s not making crazy power to need all the additional sensors/gauges. 

I would not replace the gauges. A well setup tune should never require any of that. I'm of the opinion that if you can't safely hand over a car to your parents to drive it's not fit for purpose and more engineering work should be done. Honestly I'm not a fan of external boost controller boxes either but if you have to you can shove the controller into the glovebox or something once it's set up. Tee it off the OEM MAP sensor. Also you probably want to put a two pin plug on the new solenoid, bolting it to the OEM location works. Just separate the wastegate line and compressor outlet so it will work on a 3 port solenoid, kevboost was walked through how to do this on an RB26, same idea just different locations on an RB25. You may have to remove the restrictor in the OEM hoses if they're still in there. 

[GTSBoy]

21 minutes ago, joshuaho96 said:

I'm not a fan of external boost controller boxes

Absolutely nothing wrong with a Profec or similar. He's on a Nistune, so external boost control is a better option anyway.

 

[joshuaho96]

2 hours ago, GTSBoy said:

Absolutely nothing wrong with a Profec or similar. He's on a Nistune, so external boost control is a better option anyway.

 

Yeah, it's more a personal pet peeve. I would rather go standalone purely to avoid putting in a Profec or whatever other standalone EBC.

[MBS206]

5 hours ago, joshuaho96 said:

Yeah, it's more a personal pet peeve. I would rather go standalone purely to avoid putting in a Profec or whatever other standalone EBC.

Sometimes a piece of hardware built to do one job excellently, can be better than a piece of hardware trying to do 20 jobs "well enough".

[joshuaho96]

2 hours ago, MBS206 said:

Sometimes a piece of hardware built to do one job excellently, can be better than a piece of hardware trying to do 20 jobs "well enough".

Isn't the whole point of this integrated circuit thing to put a bunch of hardware all in one little package? Integration also brings its own benefits, at least in theory. If you were to put an electronic wastegate or do an N54-style vacuum wastegate that is normally fully open but closes under vacuum integrating everything allows you to do tricks like full wastegate bypass at cold start to warm the cats or in eco-mode under a certain torque request to reduce exhaust pumping resistance. Or full bypass as a limp mode if a certain amount of knock is detected. Or managing the compressor so it never reaches the surge point.

None of this is strictly necessary per se but standalones generally have good enough boost control. PID control isn't exactly some crazy difficult problem to solve.

[MBS206]

32 minutes ago, joshuaho96 said:

Isn't the whole point of this integrated circuit thing to put a bunch of hardware all in one little package? Integration also brings its own benefits, at least in theory. If you were to put an electronic wastegate or do an N54-style vacuum wastegate that is normally fully open but closes under vacuum integrating everything allows you to do tricks like full wastegate bypass at cold start to warm the cats or in eco-mode under a certain torque request to reduce exhaust pumping resistance. Or full bypass as a limp mode if a certain amount of knock is detected. Or managing the compressor so it never reaches the surge point.

None of this is strictly necessary per se but standalones generally have good enough boost control. PID control isn't exactly some crazy difficult problem to solve.

The issue still requires a human to get all the logic right, and each thing being done takes up processing power. Meaning less processing power for other tasks to occur too.

It also typically means a team of size 10, is working one everything, vs 5x teams of 3 working on separate products, so less man power to review and perfect it all.

 

That's the typical issue of AIO. It's also why manufacturers of cars even split tasks out into separate systems, and share data as required

[Milkmun]

On 17/02/2025 at 10:08 PM, DraftySquash said:

It was roughly 3.5 hours. 
 

car went in around 11:00 and I was done around 2:30

He did the initial runs, install the BC and then Nistune install and tune. 
The best part was sitting in the lobby and hearing the skyline on full throttle at the dyno 😂😂

So what now? Enjoy it and go cruising or more modifications?

Few meets/cruises happen in the west every now and then, should definitely take it out.

[joshuaho96]

10 hours ago, MBS206 said:

The issue still requires a human to get all the logic right, and each thing being done takes up processing power. Meaning less processing power for other tasks to occur too.

It also typically means a team of size 10, is working one everything, vs 5x teams of 3 working on separate products, so less man power to review and perfect it all.

 

That's the typical issue of AIO. It's also why manufacturers of cars even split tasks out into separate systems, and share data as required

I really find it hard to believe that boost control demands enough compute that it needs its own module. Especially if the only real logic is closed loop boost control + adjustable boost target based on a dial or ethanol content.

[DraftySquash]

On 18/2/2025 at 9:52 PM, Milkmun said:

So what now? Enjoy it and go cruising or more modifications?

Few meets/cruises happen in the west every now and then, should definitely take it out.

It’s time to take her out more on weekends!! 
First thing is a wash. I’ve got my citizenship ceremony this weekend and I’m going to roll up in her 😂😝

Next up will be getting the mechanic to look at my fuel sender O ring around mid-March. I’m saving up for a different front bar so that would be after that. But she’s running happy, so I can sleep easy and slow down. Not chasing power for now. 
 

yeah, I’d like to take her down to some meets. but when you’re not on social media anymore, it’s not easy to find those out on time 😂

[Milkmun]

On 19/02/2025 at 11:02 AM, DraftySquash said:

It’s time to take her out more on weekends!! 
First thing is a wash. I’ve got my citizenship ceremony this weekend and I’m going to roll up in her 😂😝

Next up will be getting the mechanic to look at my fuel sender O ring around mid-March. I’m saving up for a different front bar so that would be after that. But she’s running happy, so I can sleep easy and slow down. Not chasing power for now. 
 

yeah, I’d like to take her down to some meets. but when you’re not on social media anymore, it’s not easy to find those out on time 😂

Congratulations on the citizenship, that's huge. Needs to be celebrated with a skid, true Aussie style (post vid) 😂 

There's a cruise this Sunday to Lorne if you're keen, meeting at Derrimut. PM me for more details if you want to come and I'll happily meet up with you beforehand.

[DraftySquash]

On 19/02/2025 at 10:08 PM, Milkmun said:

Congratulations on the citizenship, that's huge. Needs to be celebrated with a skid, true Aussie style (post vid) 😂 

Hahaha thanks mate

 

 

On 19/02/2025 at 10:08 PM, Milkmun said:

There's a cruise this Sunday to Lorne if you're keen, meeting at Derrimut. PM me for more details if you want to come and I'll happily meet up with you beforehand.

That's very cool! But I've got a lunch booked on Sunday with the fam bam. But I might come to the first meetup at least. Will PM you

[MBS206]

On 2/19/2025 at 6:52 AM, joshuaho96 said:

I really find it hard to believe that boost control demands enough compute that it needs its own module. Especially if the only real logic is closed loop boost control + adjustable boost target based on a dial or ethanol content.

It does when you start adding everything else in. But it's not just compute.

It's the logic. Getting your timing right (I'm not meaning ignition timing for the engine). Making sure of your memory mappings, seeing your interrupts. Microcontroller devices only have so much capacity. For the most part, you want all those timers and interrupts in use on your engine control, which means you're left with less than ideal methods for timing and management of other control functions.

 

Let's put it this way, my job is all about building custom hardware, that goes into cars, and integrates with them. We're also waiting on a media confirmation from SpaceX too fora world first we've just completed with them in NZ too. It's not just the little toys I play with. But you know, you can think and believe what you want.

[joshuaho96]

11 minutes ago, MBS206 said:

It does when you start adding everything else in. But it's not just compute.

It's the logic. Getting your timing right (I'm not meaning ignition timing for the engine). Making sure of your memory mappings, seeing your interrupts. Microcontroller devices only have so much capacity. For the most part, you want all those timers and interrupts in use on your engine control, which means you're left with less than ideal methods for timing and management of other control functions.

 

Let's put it this way, my job is all about building custom hardware, that goes into cars, and integrates with them. We're also waiting on a media confirmation from SpaceX too fora world first we've just completed with them in NZ too. It's not just the little toys I play with. But you know, you can think and believe what you want.

I don't really understand because clearly it's possible. The factory ECU is running on like a 4 MHz 16-bit processor. Modern GDI ECUs have like 200 MHz superscalar cores with floating point units too. The Haltech Nexus has two 240 MHz CPU cores. The Elite 2500 is a single 80 MHz core. Surely 20x the compute means adding some PID boost control logic isn't that complicated.

I'm not saying clock speed is everything, but the requirements to add boost control to a port injection 6 cylinder ECU are really not that difficult. More I/O, more interrupt handlers, more working memory, etc isn't that crazy to figure out. SpaceX if anything shows just how far you can get arguably doing things the "wrong" way, ie x86 COTS running C++ on Linux. That is about as far away from the "correct" architecture as it gets for a real time system, but it works anyways. 

[MBS206]

7 minutes ago, joshuaho96 said:

I don't really understand because clearly it's possible. The factory ECU is running on like a 4 MHz 16-bit processor. Modern GDI ECUs have like 200 MHz superscalar cores with floating point units too. The Haltech Nexus has two 240 MHz CPU cores. The Elite 2500 is a single 80 MHz core. Surely 20x the compute means adding some PID boost control logic isn't that complicated.

I'm not saying clock speed is everything, but the requirements to add boost control to a port injection 6 cylinder ECU are really not that difficult. More I/O, more interrupt handlers, more working memory, etc isn't that crazy to figure out. SpaceX if anything shows just how far you can get arguably doing things the "wrong" way, ie x86 COTS running C++ on Linux. That is about as far away from the "correct" architecture as it gets for a real time system, but it works anyways. 

As I said, there's trade offs to jamming EVERYTHING in. Timing, resources etc, being the huge ones. Calling out the factory ECU has nothing to do with it, as it doesn't do any form of fancy boost control. It's all open loop boost control.

You mention the Haltech Nexus, that's effectively two separate devices jammed into one box. What you quote about it, is proof for that. So now you've lost flexibility as a product too...

 

A product designed to do one thing really well, will always beat other products doing multiple things. Also, I wouldn't knock COTS stuff, you'd be surprised how many things are using it, that you're probably totally in love with

As for the SpaceX comment that we're working directly with them, it's about the type of stuff we're doing. We're doing design work, and breaking world firsts. If you can't understand that I have real world hands on experience, including in very modern tech, and actually understand this stuff, then to avoid useless debates where you just won't accept fact and experience, from here on, it seems you'd be be happy I (and possibly anyone with knowledge really) not reply to your questions, or input, no matter how much help you could be given to help you, or let you learn. It seems you're happy reading your data sheets, factory service manuals, and only want people to reinforce your thoughts and points of view. 

[joshuaho96]

2 hours ago, MBS206 said:

As I said, there's trade offs to jamming EVERYTHING in. Timing, resources etc, being the huge ones. Calling out the factory ECU has nothing to do with it, as it doesn't do any form of fancy boost control. It's all open loop boost control.

You mention the Haltech Nexus, that's effectively two separate devices jammed into one box. What you quote about it, is proof for that. So now you've lost flexibility as a product too...

 

A product designed to do one thing really well, will always beat other products doing multiple things. Also, I wouldn't knock COTS stuff, you'd be surprised how many things are using it, that you're probably totally in love with

As for the SpaceX comment that we're working directly with them, it's about the type of stuff we're doing. We're doing design work, and breaking world firsts. If you can't understand that I have real world hands on experience, including in very modern tech, and actually understand this stuff, then to avoid useless debates where you just won't accept fact and experience, from here on, it seems you'd be be happy I (and possibly anyone with knowledge really) not reply to your questions, or input, no matter how much help you could be given to help you, or let you learn. It seems you're happy reading your data sheets, factory service manuals, and only want people to reinforce your thoughts and points of view. 

How complicated is PID boost control? To me it really doesn't seem that difficult. I'm not disputing the core assertion (specialization can be better than general purpose solutions), I'm just saying we're 30+ years removed from the days when transistor budgets were in the thousands and we had to hem and haw about whether there's enough ECC DRAM or enough clock cycles or the interrupt handler can respond fast enough to handle another task. I really struggle to see how a Greddy Profec or an HKS EVC7 or whatever else is somehow a far superior solution to what you get in a Haltech Nexus/Elite ECU. I don't see OEMs spending time on dedicated boost control modules in any car I've ever touched. Is there value to separating out a motor controller or engine controller vs an infotainment module? Of course, those are two completely different tasks with highly divergent requirements.

The reason why I cite data sheets, service manuals, etc is because as you have clearly suggested I don't know what I'm doing, can't learn how to do anything correctly, and have never actually done anything myself. So when I do offer advice to people I like to use sources that are not just based off of taking my word for it and can be independently verified by others so it's not just my misinterpretation of a primary source.

Edited February 20 by joshuaho96

[MBS206]

19 minutes ago, joshuaho96 said:

How complicated is PID boost control? To me it really doesn't seem that difficult. I'm not disputing the core assertion (specialization can be better than general purpose solutions), I'm just saying we're 30+ years removed from the days when transistor budgets were in the thousands and we had to hem and haw about whether there's enough ECC DRAM or enough clock cycles or the interrupt handler can respond fast enough to handle another task. I really struggle to see how a Greddy Profec or an HKS EVC7 or whatever else is somehow a far superior solution to what you get in a Haltech Nexus/Elite ECU. I don't see OEMs spending time on dedicated boost control modules in any car I've ever touched. Is there value to separating out a motor controller or engine controller vs an infotainment module? Of course, those are two completely different tasks with highly divergent requirements.

The reason why I cite data sheets, service manuals, etc is because as you have clearly suggested I don't know what I'm doing, can't learn how to do anything correctly, and have never actually done anything myself. So when I do offer advice to people I like to use sources that are not just based off of taking my word for it and can be independently verified by others so it's not just my misinterpretation of a primary source.

First up, I wouldn't use PID straight up for boost control. There's also other control techniques that can be implemented. And as I said, and you keep missing the point. It's not the ONE thing, it's the wrapping it up together with everything else in the one system that starts to unravel the problem.

It's why there are people who can work in a certain field as a generalist, IE a IT person, and then there are specialists. IE, an SQL database specialist.

Sure the IT person can build and run a database, and it'll work, however theyll likely never be as good as a specialist.

 

So, as said, it's not as simple as you're thinking. And yes, there's a limit to the number of everything's in MCUs, and they run out far to freaking fast when you're designing a complex system, which means you have to make compromises. Add to that, you'll have a limited team working on it, so fixing / tweaking some features means some features are a higher priority than others. Add to that, someone might fix a problem around a certain unrelated feature, and that change due to other complexities in the system design, can now cause a new, unforseen bug in something else.

 

The whole thing is, as said, sometimes split systems can work as good, and if not better. Plus when there's no need to spend $4k on an all in one solution, to meet the needs of a $200 system, maybe don't just spout off things others have said / you've read.

There's a lot of misinformation on the internet, including in translated service manuals, and data sheets. Going and doing, so that you know, is better than stating something you read. Stating something that has been read, is about as useful as an engineering graduate, as all they know is what they've read. And trust me, nearly every engineering graduate is useless in the real world.

And add to that, if you don't know this stuff, and just have an opinion, maybe accept what people with experience are telling you as information, and don't keep reciting the exact same thing over and over in response.