MATH+Logic: An engineering approach in search for a perfect TURBO. (2 Viewers)

[Dougal]

I swapped the bung but realized I was confused and my EGT probe was already in cylinders 4-5-6 but swapped to 1-2-3 just to get values and I could not notice any difference in EGT values vs front and rear bank. I cant for the life of me find any data about what AFR is safe on spool up. Again I understand full load safe AFR to be 18:1 or above.

Let me paint a scenario to further describe what I'm stuck on. Lets say I tune to hit 15:1 AFR full pedal at 1600rpm in 4th gear. Then as boost and rpm rise I lean out almost instantly 20:1+ AFR. Does this scenario sound dangerous? I have while playing with spring tension and pin profile hit 14:1 and obviously the response feels great EGT is still a non issue as its so brief and once the turbo is making anything above 5 psi EGT is stable. BUT what might cylinder pressures be doing in this moment? With that rich of a AFR briefly am I even concerned of cylinder pressure or only EGT?

I'm guessing since not much info about this specific scenario during tuning is being talked about or discussed it may be a non issue and I'm asking silly questions.

One observation here is currently I have spring tension set to not allow anything lower than 17:1 if I floor it from 1600rpm in 4th gear with minimal smoke until boost rises. This setup produces AFR to be max 22:1 on a 3rd to 4th gear shift and leaning out rapidly to above 30:1 and maybe an EGT of 600-700F (normal street driving) and these values aren't exact but close. So I'm overly curious about how far I can go with AFR to raise EGT a bit on cruise conditions. I have played with multiple pin profiles, many different spring tensions but mostly I feel under fueled on the bottom end.

My logic with tuning the compensator could be flawed here so appreciate any advice and experience from the salt dogs

Before spool you want to keep AFR about 17:1 max to avoid smoke. I had a diesel car that dipped to around 14:1 and it was rough and horrible to drive at lower rpm. It was electronic so I could lean it back out to ~17:1 and it smoothed right out and never smoked again.

Smoke is not only external. But it puts carbon straight into your oil too.

Your cruise EGT is set mainly by injection timing and turbo size. More advanced timing will reduce boost a fraction through cooler exhaust.

 

[Mcreight911]

If your pump is standard you will have to make somewhat of a compromise when tuning . Your pump hasn’t got enough adjustment in it to fuel ideally at low rpm and match the capability of the turbo as well . A “built” pump with more aggressive delivery, more overall capability and a revised timing map will complement that turbo .

As for combustion pressures, if your injectors are good you wont hurt the engine from high combustion pressure. Possibly with low afr high egt lugging .

Re tuning , Look at afrs but dont focus on them. If it smokes more than u want pull fuel in that area. Many say 18:1 afr on boost is the smoke point but that is dependent on a few other factors. Heat helps turbine drive, getting moderate egt quick helps but it needs to stabilise. Afrs Dipping under 16:1 in any rpm zone you want to lug or tow will put you at high egt . As Dougal said with your direct injection engine around 17:1 off boost you start to get some smoke .

I have tuned a winch race truck with a 1hdt 18g tdo5 based turbo and trick pump to 16:1 off boost 15.5:1 as you punch it under spoolup instantly rising 18:1, dipping to 15.5 around 3000rpm .
running full throttle max boost for a couple of mins in deep sand on the beach will see 850oC egt +. This is not how id tune one for touring or towing . Keep in mind the ambient temp and grade you are tuning on and leave some safety factor if you plan to tow heavy or at altitude.

Personally i dont like to see any smoke on a tune aimed at safety e.g towing heavy with some safety for high ambient temps . In Australia we don’t have the elevation change other countries do so thats not really factored into a tune or turbo sizing .

The timing curve and the capacity of a standard pump wont get close to maxing that turbo .
There are a few other things to do to a pump that aid drivability too but thats best left to a competent pump shop.

 

[KiwiDingo]

Timing is something most people don't even think about. I'm not just talking about that silly static timing number people think is so important. The timing curve aka the auto advance timing piston plays a huge role in how the vehicle performs. I found it wasn't such a big issue with some of the little turbos I've run but once I started stepping up it was really evident the timing needed to change. There's quite a bit you can do with piston travel, spring rates and preload on the timing piston not to mention the case pressure regulator which alters the timing curve and how it matches your setup like turbo, injectors and overall fueling etc. I found it fun and enjoyed the process but it took months and months of tinkering and testing to track and record changes for each small change made to find the optimum setting for the desired driveability and performance I was after.

 

[Magic Spool Bus]

If your pump is standard you will have to make somewhat of a compromise when tuning . Your pump hasn’t got enough adjustment in it to fuel ideally at low rpm and match the capability of the turbo as well . A “built” pump with more aggressive delivery, more overall capability and a revised timing map will complement that turbo .

As for combustion pressures, if your injectors are good you wont hurt the engine from high combustion pressure. Possibly with low afr high egt lugging .

Re tuning , Look at afrs but dont focus on them. If it smokes more than u want pull fuel in that area. Many say 18:1 afr on boost is the smoke point but that is dependent on a few other factors. Heat helps turbine drive, getting moderate egt quick helps but it needs to stabilise. Afrs Dipping under 16:1 in any rpm zone you want to lug or tow will put you at high egt . As Dougal said with your direct injection engine around 17:1 off boost you start to get some smoke .

I have tuned a winch race truck with a 1hdt 18g tdo5 based turbo and trick pump to 16:1 off boost 15.5:1 as you punch it under spoolup instantly rising 18:1, dipping to 15.5 around 3000rpm .
running full throttle max boost for a couple of mins in deep sand on the beach will see 850oC egt +. This is not how id tune one for touring or towing . Keep in mind the ambient temp and grade you are tuning on and leave some safety factor if you plan to tow heavy or at altitude.

Personally i dont like to see any smoke on a tune aimed at safety e.g towing heavy with some safety for high ambient temps . In Australia we don’t have the elevation change other countries do so thats not really factored into a tune or turbo sizing .

The timing curve and the capacity of a standard pump wont get close to maxing that turbo .
There are a few other things to do to a pump that aid drivability too but thats best left to a competent pump shop.

Solid info fellas and its much appreciated. I was on the fence about injection work or I would say I was trying to put it off longer. I was fairly sure the tuning issues I have been experiencing were due to the stock limits of the pump. I found a really good shop out here local to me with much experience with the YANMAR pumps so it looks like that's up next.

 

[Magic Spool Bus]

Back again... so initially I thought I was experiencing a bouncing wastegate at higher rpm 2500+ and high load 80%+ throttle. After trying multiple spring loads in the wastegate, multiple configurations from single port to two port on the wastegate can as well as 3 port solenoids and 4 port solenoids the surging remains the same. What I am experiencing is a surge of sorts and its audible through the exhaust mainly as mine dumps right in front of driver side rear tire and also felt in the seat. However I have noticed boost pressure is holding at 22 psi ish, backpressure around 27psi ish but my afr gauge during this event is shifting from 19:1 to 21:1 before I end up letting out around 3000rpm and also puffs of black smoke consistent with the surge feeling. Now I can take rpm up gradually and and none of this happens, I can also hit max boost under moderate load and have no issues. Other than this I have no other known symptoms like oil loss, hard starting, poor fuel consumption, low power... I just cant complete a wide open pull to redline.

Injection work is in the future but I'm beginning to wonder if my injection system is not up to the task under wide open throttle with this turbo or if something is a miss in the head. The engine truly runs great unless I try to do a hard pull past 2500rpm. This is completely unique to this new setup as it never happened with the green wheel G Turbo. My fuel screw is wound as much as possible leaving no more adjustment in the linkage for the pedal to drop the idle back down. I suppose I could pull some fuel out and see if this solves the issue but is this consistent with running out of my pumps capabilities or the injectors? These have been rebuilt as of about 25k miles ago.

EDIT: after combing the wide internet knowledge I do not believe it its compressor surge however it could be. Mapping it on matchbot would show at these RPMs I am no where near the surge line at this Pressure Ratio.

 

[Dougal]

Back again... so initially I thought I was experiencing a bouncing wastegate at higher rpm 2500+ and high load 80%+ throttle. After trying multiple spring loads in the wastegate, multiple configurations from single port to two port on the wastegate can as well as 3 port solenoids and 4 port solenoids the surging remains the same. What I am experiencing is a surge of sorts and its audible through the exhaust mainly as mine dumps right in front of driver side rear tire and also felt in the seat. However I have noticed boost pressure is holding at 22 psi ish, backpressure around 27psi ish but my afr gauge during this event is shifting from 19:1 to 21:1 before I end up letting out around 3000rpm and also puffs of black smoke consistent with the surge feeling. Now I can take rpm up gradually and and none of this happens, I can also hit max boost under moderate load and have no issues. Other than this I have no other known symptoms like oil loss, hard starting, poor fuel consumption, low power... I just cant complete a wide open pull to redline.

Injection work is in the future but I'm beginning to wonder if my injection system is not up to the task under wide open throttle with this turbo or if something is a miss in the head. The engine truly runs great unless I try to do a hard pull past 2500rpm. This is completely unique to this new setup as it never happened with the green wheel G Turbo. My fuel screw is wound as much as possible leaving no more adjustment in the linkage for the pedal to drop the idle back down. I suppose I could pull some fuel out and see if this solves the issue but is this consistent with running out of my pumps capabilities or the injectors? These have been rebuilt as of about 25k miles ago.

EDIT: after combing the wide internet knowledge I do not believe it its compressor surge however it could be. Mapping it on matchbot would show at these RPMs I am no where near the surge line at this Pressure Ratio.

Do you have an intake restriction that is pushing the compressor closer to surge? I run a Donaldson Informer on the intake to show max vacuum at the exit from the air-cleaner.

 

[Magic Spool Bus]

Do you have an intake restriction that is pushing the compressor closer to surge? I run a Donaldson Informer on the intake to show max vacuum at the exit from the air-cleaner.

I have a airbox fitted that uses a duramax panel air filter 4in inlet and outlet. I wouldn’t imagine it’s the box… however my intake tube from box to turbo inlet is 2 silicon elbows with a tiny 45 degree angle metal 4in tube in the middle. This could be sucking shut but I don’t see why it would “pulse” because the surge im feeling is a pulse like surge with about .5 seconds in between pulses hence why I thought it may be the wastegate bouncing. It’s on and off power in distinct evenly spaced pulses.

 

[Dougal]

I have a airbox fitted that uses a duramax panel air filter 4in inlet and outlet. I wouldn’t imagine it’s the box… however my intake tube from box to turbo inlet is 2 silicon elbows with a tiny 45 degree angle metal 4in tube in the middle. This could be sucking shut but I don’t see why it would “pulse” because the surge im feeling is a pulse like surge with about .5 seconds in between pulses hence why I thought it may be the wastegate bouncing. It’s on and off power in distinct evenly spaced pulses.

Weird resonance somewhere? If it's close to target boost level and it could be wastegate flutter, then putting a restriction in the wastegate line will damp it out.

 

[macca1590]

Hows the Borgwarner going? if im feeling fancy id like to upgrade in the new year and this looks like a very interesting option

 

[Magic Spool Bus]

Hows the Borgwarner going? if im feeling fancy id like to upgrade in the new year and this looks like a very interesting option

Its still going strong. Just know its an expensive option. If you end up wanting to get a rear housing that's twin scroll you also need to get a manifold made to fit it. Sometimes I wish I would have went the EFR 6758 which is a little smaller than the 7163. The 7163 really doesn't do much unless your at or above 2000 rpm. Makes highway driving a breeze though and overall my fuel consumption is around 20MPG now with 35s and stock gearing.

 

[macca1590]

Its still going strong. Just know its an expensive option. If you end up wanting to get a rear housing that's twin scroll you also need to get a manifold made to fit it. Sometimes I wish I would have went the EFR 6758 which is a little smaller than the 7163. The 7163 really doesn't do much unless your at or above 2000 rpm. Makes highway driving a breeze though and overall my fuel consumption is around 20MPG now with 35s and stock gearing.

Sounds like the Twin scroll is the go, being a larger unit would help with spool up too I suppose, not that im a guru by any means but looks like the 6758 isnt very far behind in flow going buy the compressor maps. That is unreal economy, yours is a manual correct? is that corrected for the larger tyres?

 

[Magic Spool Bus]

Sounds like the Twin scroll is the go, being a larger unit would help with spool up too I suppose, not that im a guru by any means but looks like the 6758 isnt very far behind in flow going buy the compressor maps. That is unreal economy, yours is a manual correct? is that corrected for the larger tyres?

The 6758 is very similar it would be a better match for someone wanting more response lower in the rev range. I'm really not sure how much it was worth going twin scroll. On paper of course it has some benefits. The main issue I have with the 7163 is I just don't have the fuel to match it yet. I think the main benefit I got out of twin scroll is that when I switched to a divided style manifold the NA power of the engine increased a bit so off boost its more peppy than it was before. Overall I'm happy with it and drivability but I wouldn't say it was worth the money spent to fit it. I think around 5-6k for turbo and getting a manifold made. At least now I have a manifold that can fit a larger category of turbos with t3 and t4 flanges. Also check out the s252sxe turbo from borgwarner. Its much cheaper and has like 10 different exhaust housings to choose from. It isn't ball bearing like the EFR turbos and you would need to have an external gate. The neat thing about the SXE line is you can over spin that turbo to 70psi and it wouldn't detonate like the efr would. Max boost on the efr is around 27psi I believe. The sxe of course wouldn't be efficient out that far but you could get away with not running a wastegate if you wanted to.

Gas mileage is corrected by me with a standard deviation of about +.7 miles traveled over per mile of what I see on the dash.

 

[IanB]

Are there any benefits to a twin scroll turbo on a non-twin scroll manifold? Or did I miss something and you're using a custom manifold?

 

[Magic Spool Bus]

Yea I am using a custom divided manifold so that I can gain the benefits of the twin scroll housing. I don't believe there would be any benefits to running a twin scroll housing and not using a true divided manifold.

I think its more acceptable the other way around though... i.e. there would be no issues running a single scroll turbine housing with a divided manifold.

 

[macca1590]

NIce, might have to sus the other options, and as you mentioned at least if i were to build a t4 twin scroll manifold it opens up heaps of other options. Interesting on the sxe being able to run silly boost and not fall apart, makes it easier to not have to worry about a wastegate haha.

I also see some people having good success with hx35s which also come in heaps of different sizes too

 

[KiwiDingo]

The neat thing about the SXE line is you can over spin that turbo to 70psi and it wouldn't detonate like the efr would. Max boost on the efr is around 27psi I believe. The sxe of course wouldn't be efficient out that far but you could get away with not running a wastegate if you wanted to.

Interesting on the sxe being able to run silly boost and not fall apart, makes it easier to not have to worry about a wastegate haha.

Yep and it's all to do with the turbine wheel material. The Inconel turbine wheel in the SXE series can handle much greater shaft speeds than the much lighter and fragile Gamma-Ti Turbine Wheel in the EFR series. BorgWarner recommendeds people running EFR turbos to have speed sensors to make sure they stay below the max recommended shaft speed whereas the SXE turbos couldn't care less.

 

[Dougal]

NIce, might have to sus the other options, and as you mentioned at least if i were to build a t4 twin scroll manifold it opens up heaps of other options. Interesting on the sxe being able to run silly boost and not fall apart, makes it easier to not have to worry about a wastegate haha.

I also see some people having good success with hx35s which also come in heaps of different sizes too

Those are very big turbos that are only really good for throwing mud and dyno queens. The HX35 is designed to run on 5.7+ litre engines. They are ~50% too big to run as a single on ~4 litre engines.

 

[macca1590]

Those are very big turbos that are only really good for throwing mud and dyno queens. The HX35 is designed to run on 5.7+ litre engines. They are ~50% too big to run as a single on ~4 litre engines.

I did sort of think that, they mention they make heaps of power but yeah the driveability down low could be a very different story haha

 

[Nz Nath]

If you wanted to go holset, there's a twinscroll turbine housing that fits the he221. Runs very well on my 13bt, lowered the full load egt by 100c vs the single scroll setup on the same fueling. I've built a manifold for my 15bf motor, but that project's on hold for the moment so can't tell you how well it goes on the 4.1l. The turbine flange is almost unique though, so if you built a manifold for it you're putting all your eggs in one basket.

 

[macca1590]

If you wanted to go holset, there's a twinscroll turbine housing that fits the he221. Runs very well on my 13bt, lowered the full load egt by 100c vs the single scroll setup on the same fueling. I've built a manifold for my 15bf motor, but that project's on hold for the moment so can't tell you how well it goes on the 4.1l. The turbine flange is almost unique though, so if you built a manifold for it you're putting all your eggs in one basket.

hmm Interesting, So was the single and twin scroll both the same a/r or cm2 however holset measure it