Questions re: Estimating when a turbo will build boost

[rchalmers3]

Well, as some of you know I'm anxious to perform a DIY turbo install on my HJ60. I have a few projects ahead of the install, so I'm using the evenings learning about turbo theory and how to evaluate a turbo based on turbo mapping and engine air consumption characteristics.

Recently I found a simulation tool for modeling your favorite intake tract configuration: Not2Fast: Turbo Calculator

The simulator has a variety of uses I am utilizing, including testing different assumptions. Especially useful to me is the small library of maps which can be used for selecting a turbo for my proposed retrofit.

The place where I am now is that I need your opinions on estimating the volumetric efficiency of the 2H at different points in the operating RPM range. This particular assumption makes a huge difference in choosing an appropriate turbo! If there are published emperical measurements, please direct me.

I also need for someone to explain to me how to deduce (using my engines estimated air consumption laid over a turbo map) when the turbo will start to build boost and when it will reach maximum boost.

With what I've read thus far, estimating where and how fast boost is created has not been discussed. Again, if there is published discussions or calculations to peruse, I thank you in advance for sharing.

I won't obscure the above questions with my own speculations, and I look forward to learing your opinions.

Here are some maps (1000, 2000 and 3500 rpm) using the online tool referenced above and assuming 80% VE flat over all rpms and over a T3 turbo map.
Thanks, Rick

[rchalmers3]

Same assumptions on T3 with smaller turbine A/R

[Dougal]

You need a turbine map or the turbo fitted to another engine and the result scaled to pick when it's going to spool.

Garrett in their new catalogue produce turbine maps which show the mass flow required to get the turbine working.

The compressor maps are only useful for knowing what rpm the turbo has to do generate that boost and the efficiency at that point.

[Tapage]

Maybe this thread would be interesting for you ..

http://forum.ih8mud.com/diesel-tech-...urbo-maps.html

[rchalmers3]

Originally Posted by Dougal

You need a turbine map or the turbo fitted to another engine and the result scaled to pick when it's going to spool.

Do you know of any data published that I can use? I've asked for this before but nobody has replied to this specific request.

Originally Posted by Dougal

Garrett in their new catalogue produce turbine maps which show the mass flow required to get the turbine working.

Does their catalog cover the older models, like the used ones I'm likely to source, or just their current product line?

Originally Posted by Dougal

The compressor maps are only useful for knowing what rpm the turbo has to do generate that boost and the efficiency at that point.

Ok, but to be specific, and I think you are best trusted to know this, there is data available (flow rate, turbine speed, absolute pressure, turbo efficiency) that could be used for extrapolating the spooling chacteristics of a given turbo. I presume the intake geometry, intake tract volume and other variables would have to be estimated, but isn't there valuable published data like the moment of inertia for some turbos published to estimate responsiveness and spooling given certain assumptions?

I'm pressing in on this area of selecting a turbo for the exact same reason as Tapage: I wish to install a DIY that does not dissapoint. Dougal, I don't intend to badger anyone. Please read this post as an inquiry. If you say it's a black science in this area and there's no emperical data, that's fine. I'm just looking for the limits of what's known.

Cheers,

Rick

[rchalmers3]

Heres an example of a turbine map. It appears to be informative on the compressor effiiciency and max flow rate. The area from atmospheric (1bar) to the start of the map (1.25 bar) is not shown.

My question is: Given the rise in flow from ambient to where it's first indicated at about 8lb/min and 1.25 bar, what elase is needed to estimate how the turbo is spooling? Can the inertia specs be used to determine what the turbo will spin to given the map data?

Rick

[Dougal]

Originally Posted by rchalmers3

Heres an example of a turbine map. It appears to be informative on the compressor effiiciency and max flow rate. The area from atmospheric (1bar) to the start of the map (1.25 bar) is not shown.

My question is: Given the rise in flow from ambient to where it's first indicated at about 8lb/min and 1.25 bar, what elase is needed to estimate how the turbo is spooling? Can the inertia specs be used to determine what the turbo will spin to given the map data?

Rick

Yes, I interpret the start of the curve as the minimum pressure/flow required to drive that turbine.
Taking that same mass flow and applying it to the compressor map will give you a rough idea. Remember that your fuel will be adding up to 5% to your exhaust mass flow that isn't present in the intake mass flow.

Unfortunately the catalogs do not cover their older turbos, only the current GT range.

Transient response (intake volume etc) is far too complicated to model easily. I think these graphs are all produced at steady state, so imagine the engine heavily loaded but slowly accelerating and you'd get the closest results to the model.
Fast acceleration of the engine brings in a whole lot of other effects like the inertial weight of the turbo rotating parts, cooling effect of cold intake and exhaust components etc.

[rchalmers3]

Originally Posted by Dougal

Transient response (intake volume etc) is far too complicated to model easily. I think these graphs are all produced at steady state, so imagine the engine heavily loaded but slowly accelerating and you'd get the closest results to the model.
Fast acceleration of the engine brings in a whole lot of other effects like the inertial weight of the turbo rotating parts, cooling effect of cold intake and exhaust components etc.

I realize I'm speaking almost entirely to you, and there is still a world of info out there to canvass. My experience at this moment is that there's not much info to go by when it comes to making an informed DIY turbo selection. Without accurate modeling of the intake system, how can you know that the turbo you are installing is going to perform as desired?

I guess that's why so many just follow the herd......

Dougie, you catch some heat for your opinions. Dosen't mean anything. I want to acknowledge you for contribution and civil responses to those who become frustrated with your opinions.

Rick

[Dougal]

Originally Posted by rchalmers3

I realize I'm speaking almost entirely to you, and there is still a world of info out there to canvass. My experience at this moment is that there's not much info to go by when it comes to making an informed DIY turbo selection. Without accurate modeling of the intake system, how can you know that the turbo you are installing is going to perform as desired?

I guess that's why so many just follow the herd......

Dougie, you catch some heat for your opinions. Dosen't mean anything. I want to acknowledge you for contribution and civil responses to those who become frustrated with your opinions.

Rick

In transient conditions, yes it's a very complicated situation. But in steady state the effect of most of those complications simply disappears.
No matter what the volume of your intake system, once it's been fed a set boost for a few seconds, it's simply passing the compressed air through. There will be some temp loss (a lot of temp lost if you've got an intercooler) and there will be some pressure loss. But the mass flow is the main concern and that can't change unless you've got a leak.

Like anything serious, you gather all the data you can, then take your best shot.
The more information you have (and higher quality information) the better your result will be. But no matter how far off you are, you'll find improvements.

There are a few who continue to spout nothing but hot air and insults, maybe one day they'll realise how that affects their reputations. But I wouldn't hold my breath.

[rchalmers3]

Originally Posted by Dougal

Remember that your fuel will be adding up to 5% to your exhaust mass flow that isn't present in the intake mass flow.


Where do you get that percentage estimate from? Are you saying I could be making a 5% correction to total calculated mass flow? My guess is there's 5% or greater error in mass flow due to design, construction and other losses, off setting a possible positive correction for added mass flow. Who knows.


Transient response (intake volume etc) is far too complicated to model easily. I think these graphs are all produced at steady state, so imagine the engine heavily loaded but slowly accelerating and you'd get the closest results to the model.
Fast acceleration of the engine brings in a whole lot of other effects like the inertial weight of the turbo rotating parts, cooling effect of cold intake and exhaust components etc.

That's kinda where I'm at. Heck, I oughta build a test motor to measure all the possible configurations. It would be fun for me and I'd prolly get something valuable out of it....

The business man in me says no! Even if I was using a 3B for a test platform and producing valuable information I don't think there would be a line of clients....

Rick

[Dougal]

Originally Posted by rchalmers3

That's kinda where I'm at. Heck, I oughta build a test motor to measure all the possible configurations. It would be fun for me and I'd prolly get something valuable out of it....

The business man in me says no! Even if I was using a 3B for a test platform and producing valuable information I don't think there would be a line of clients....

Rick

The 5% comes from the air-fuel ratio. For a diesel the smoke limit is around 18:1, so a typical maximum power air/fuel ratio is in the region of 20:1.
My isuzu is currently running around 28:1 at max power, but that'd due to high boost and no intercooler, I'm pushing excess air to keep the EGT's under control.

Isn't the world full of interesting projects requiring time and money that can't be spared?

[rchalmers3]

In case anyone has any interest, there is developing technology in small engine turbos. Companies are testing and fitting turbos with electric motors to create available boost at idle. This boost can eliminate lag, allowing smaller engines perform the work of bigger engines.

Turbodyne: Global Solutions to a Global Problem ... - The TurboPac™ Air Injection System

Link to 304k .pdf document: Information Bridge: DOE Scientific and Technical Information - Sponsored by OSTI

Of course there's no free ride..... the power consumption of these electric motors are measured in kilo watts....

Just spent the last hour looking at all the performance "magic bullets" on E-bay. Apparently people will put anything that creates a breeze on their intake tract. You know those plastic squrill cage blowers that come with your blow up doll? It's being sold on E-bay as a hop up kit for your car!

Rick

[Dougal]

Originally Posted by rchalmers3

In case anyone has any interest, there is developing technology in small engine turbos. Companies are testing and fitting turbos with electric motors to create available boost at idle. This boost can eliminate lag, allowing smaller engines perform the work of bigger engines.

Turbodyne: Global Solutions to a Global Problem ... - The TurboPac™ Air Injection System

Link to 304k .pdf document: Information Bridge: DOE Scientific and Technical Information - Sponsored by OSTI

Of course there's no free ride..... the power consumption of these electric motors are measured in kilo watts....

Just spent the last hour looking at all the performance "magic bullets" on E-bay. Apparently people will put anything that creates a breeze on their intake tract. You know those plastic squrill cage blowers that come with your blow up doll? It's being sold on E-bay as a hop up kit for your car!

Rick

Search for the Garrett E-booster, similar thing. Small electric supercharger to get the turbo out of bed early.
There're some absolute jokes on Ebay.