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Turbo LS Combustion Project

Old 01-25-2019, 10:43 PM
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Default Turbo LS Combustion Project

Hey All,

I'm new here but I wanted to share a project that I'm putting together in my free time to help myself further understand what's going on inside the cylinder of an IC engine. I intend to share much, if not all, of the information that I am able to gather from this build along with some of the theory behind it if I'm able to understand it well enough. I'm a firm believer that explaining new information to someone else in a way that makes sense to them is the best way to strengthen and improve my own knowledge, so if there's anything you'd like explained I will do my best to answer questions.

Here's the Cliffnotes for what's to come:

What's different about this build?
I will be installing an in-cylinder pressure transducer in cylinder #7, based on feedback from a prior thread on which cylinder is generally the most sensitive.
I will have Wideband O2, exhaust gas temperature, intake port pressure, and exhaust port pressure on each cylinder to make sure every cylinder is running at close to the same conditions. I will make modifications to each cylinder to correct issues that I see to maximize power from a relatively mild build. There will also be a pressure and temperature sensor on either side of the compressor and turbine to characterize the actual efficiency of the turbocharger, since it doesn't appear that there's much available data out there on the Chinese GT45.

What are you going to use it for?
I intend to use the pressure transducer, coupled with a rotary encoder to measure crank position very precisely, to measure how much work a cylinder is doing per cycle. By paying attention to this, I won't have to guess on an optimal spark value or fuel value when I begin to work on the calibration - I can choose the right values based on what will maximize the amount of work done per cycle or what will be the most stable. I should be able to have a smooth idle with factory level fuel economy and drivability given enough time. I can also use it to measure heat release rates and pressure rise rates to protect components. If the encoder resolution is high enough, I may also be able to use it to diagnose how well each individual cylinder is running based on the predicted vs actual accelerations between segments (tertiary goal, will likely get put on the backburner for a while)

1) Understand the combustion process and apply some of the information that I learned in school to maximize power output in a relatively mild build.
2) Understand he effects of specific (and common) modifications, such as different fuels, nitrous, water-meth, etc on combustion
3) Develop a data acquisition system that I can carry over between projects
4) Have a kick *** daily driven truck that I can put another 30k miles on without worrying too much about it. 600 whp should be the ticket for now.
5) Help people understand why things happen the way that they do.

Build Details:
Budget build, aside from the majority of the data acquisition. This is more of a research project for me, so I'm not going to be too torn up if I nuke a turbo or puke a rod through the block.
Truck: 2000 Silverado 2500 with 165k. LQ4, 4L80E, 3.73 Posi rear end, 4WD through an NP246 transfer case
Engine: Still have to build, but...LS9 head gaskets, ARP rod bolts and head studs, new gapped rings,new bearings in bottom end, LS6 cam, stock truck intake (instrumented), Deka 80's (will go smaller if I don't have good control of idle fueling)
Turbo system: eBay GT45, eBay forward headers with crossover built by myself, 2X Tial 38mm wastegates, 50mm eBay BOV, 3" down pipe w/exhaust cutout (eventually). For those concerned, I'm going to do some durability improvements on most of the chinese components to help them live a bit longer (ex: VSR balance the CHRA of the GT45, support the turbo on something other than the headers)

The build really isn't anything special, which is why I won't focus too heavily on it in this thread unless requested.

I'm sure I'll think of a few more details by morning, but I'm tired as hell and need some sleep. I'll try and update this thread fairly regularly as it is currently -27 F outside and I will be working only on the data acquisition and measurements until it gets to the point where my hands stop freezing to the tools.

Let me know if you have any questions!

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Old 01-26-2019, 11:29 AM
I have a gauge for that
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As an engineer this sounds like a great project! Are you planning to do this on a test stand engine or installed driving around? You are talking about a ton of instrumentation that is not going to be easy to fit.

Another thing to consider is also actual cam position relative to crank and also cooling system pressure. It is common to put s pressure transducer in the cooling circuit now to see when you start to lift the heads, it would be interesting to see more scientific data from that if it's actually useful or not.
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Old 01-26-2019, 03:54 PM
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Originally Posted by Atomic View Post
Are you planning to do this on a test stand engine or installed driving around?
Another thing to consider is also actual cam position relative to crank and also cooling system pressure.
I'm setting this up to be all done onboard - I doubt I'll have much of a passenger seat left after I'm done with this, haha. I think the wiring is going to be the most painful part, but as of now I'll only have modest amount of space taken up by the data acquisition. I'll have to package the charge amp for the pressure transducer, an NI MyDaq or myRIO for the high speed stuff (haven't decided yet), an Arduino or Raspberry Pi for the low speed stuff, and all of the power supplies.

Good thoughts on the coolant pressure though. It looks like the sensor I would use is rated for about 1kHz sampling - at 4 combustion events per revolution, that leaves me a little (but a very small margin) headroom to sample fast enough to catch a pressure pulse at max engine speed. It would be super cool to sample fast enough to be able to tell which cylinder is lifting, but chances are pretty good that I'd just end up averaging the signal to see a pressure rise over the expected value. If there's any other ideas that you've got, definitely let me know!

Today I'm working on the fuse box for the data acq, so I'll see if I can post up some pics of it a bit later.

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