combustion analysis

[tadd]

72RSR:
That's a really awesome looking piece!

I do agree start up costs are not to be trivial, however I would guess you could sneak it in such that the data aq equipment would only double the cost of a dyno install? I had a buddy buy a new dynojet in the 2002ish time frame and that was 30-40k so another 30 to add CAS? Regardless, that's the service providers problem .

For us customers it's what is the 'rent' cost vs what we learn. Those pesky utils.

So on the DIY front... When I go blasting I got a pelican box with a NI Vixy box, a laptop, a signal conditioner, the transducer, and coax to string it all together. This sounds ALOT like what you describe. A recient project utilized this transducer from PCB:

Model 105C12 Spec Sheet

We get these in the $350-450 range. It's a 10-32 mounting thread, so pretty small. I haven't drawn up a part, but given our airheads use a M14-1.25 plug (if I'm remembering this right), it seems like one could fit a 10 mm plug along with the 10-32 transducer in a M14 'bung'. I bet it will be really tight, and things would need some serious placement love. One saving grace would be the fire port which would push the transducer further into the wrench section which is wider. An M10 plug is the smallest I see on the Bosch plug translation chart.

That particular transducer typically has a 1.7-1.9 micro second rise time. Plenty fast i should think given that an 8k motor is around 20 micro seconds per crank degree of rotation if I did my dimensional analysis right. I go bang only once , so I don't know if the decay time is fast enough, but typical rule of thumb seems to be 2-3x rise time. So that leaves us still less than 10 micro sec... Starting to get too close, but not undoable I would think. The fire port will add a functional delay depending on th length, but that's just a label correction in the data set since the pulse getting to the transducer is the previous or 2nd previous. Heck, that's recording every degree. Move to data every 2 or three degrees and there is a really comfortable margin.

I'm not sure what's in the signal conditioner box but for the 9V batteries they eat. Can't be much, but they aren't that expensive to buy outright. I'm not an EE jock. I leave that to others more twisted than I . Especially the good RF guys .

That leaves data aq.... Which makes me wonder about using n of these. Amazon sells them. Open source. $99. I haven't dug into it, so I don't know if it will output to a computer realtime.

Amazon.com: DSO Nano V2 - Pocket-Sized Digital Oscilloscope: Electronics

Some software via lab view and instant Combustion analysis . Easy peasy .

I'll think I'll rent time for now, I'd rather be driving .... Or wim the lotto so I can play for a living.

PFM: Well, iSystems has this stuff on their dyno. Hence I'm trying to get at if this would be worth it to me personally. May be, may not. That's why I'm asking. It might also be useful to someone else so I posted to inform myself as well as others.


t

[72rsr]

PFM,
You are on the right track with your questions. Starting with a well tuned engine, you are looking at very small gains Maybe on the order of 1 to 3%. You can optimize individual cylinders via fuel and spark with these tools, but it may be easier (read cheaper) to use such things as EGTs for fuel. I am working with old school stuff (carbs and distributor) so it is a bit tougher. I am looking to try to optimize timing by evaluating 50% mass fraction burns on individual cylinders, but I will only have one timing adjustment. High dollar NASCAR teams have been known to spend the time and money to have individual cylinders offset timing with the distributor not being equidistant between cylinders. High tech development on low tech devices.

The idea of using this as a tuning device is certainly possible, but it is more intended for combustion chamber development, alternative fuels, and major component development such as port designs affecting flow tumble and swirl.

With current digital EMS systems, we have more control of the individual cylinder events, controls and timing. So here you have more flexibility, but starting with a well tuned engine, I wouldn't look for major gains. This is like the kids with tuner cars and their laptops like you see on TV. Usually they are not starting with a well sorted system, so they can make larger gains to a point. Then they need this type of more sophisticated data and feedback else they are spinning their wheels.

I'd also like to compliment Levon, as he is one of the few to attempt this with our Porsche air cooled stuff, and it isn't easy! I encourage all of you to keep studying and moving toward this level of work. It can be rewarding.

Peter
72 RSR clone vintage racing in the Midwest and Northeast

[72rsr]

Tadd,
You certainly have the right ideas. I am a sensor snob as that is my specialty, so I only regard two companies as genuine players...AVL and Kistler. That said, others do make sensors. You can make adapters and such, we do it all the time. You must be careful of two factors: the indicating passages must be designed so as to not introduce Helmholtz resonances (think organ-pipe) into the data. This is often an issue and particularly with the older designs of equipment. The other is thermo shock the diaphragm of the sensor causing cyclic drift, which may or may not recover by the next firing event. This is why we use flame arrestors on the tips of the sensors to protect the diaphragms.

The lab view solutions are very possible. Many universities use it because it is cheap and they have slave labor (students) to spend months writing the code. I'd rather be playing with my car!

I have uploaded two more photos for you. One is our 10mm spark plug solution with integrated sensor as the body is too small to offset and install a separate probe. Note the diaphragm on the side of the body. The other is the finest sensor in the world bar none...and note it is only a 5mm sensor (photos are way different scales). So maybe size doesn't matter?? ;>)

Great discussions and I'm headed to the garage for the afternoon. I'll check in again tonight.

Peter

[bmep]

After much coercion, threats and pleading I respond. First one comment; "a well tuned and sorted out" engine would have to be one open to much interpretation. Remember, one mans junk is another mans treasure; nothing implied. How much can be gained with combustion analysis? A very good question; if I could answer that in one sentence I could fix our economy and I know no one else that could answer it either. But, give the individual peak cylinder psi at crank angle, individual cylinder cyclical pressure variation, individual cylinder psi rate of rise, mass burn per cylinder crank angle and the p/v loop per cylinder and some of us may take a stab at answering. The thermodynamics that generate cylinder pressure is not a given and all engines do not read the books we do so making a blanket statement is most difficult. I would like to thank everyone for their interest and comments.

[304065]

Levon (I assume it's you)

Thanks for joining us here and for elevating the level of discussion. Just a couple questions if you don't mind.

I see you used a crank trigger on the 2,0 liter engine with the green fan. What did you discover about spark timing or spark scatter? Did your ignition control somehow compensate for timing differences among the different cylinders?

I see you used PMO tall manifolds and what appear to be 40 webers. What pressure differences did you observe in Cylinders 1, 3, 4 and 6, vs. 2 and 5, the cylinders affected by the curved intake runners? The original Solex carbs, and certain ITB setups, have a straight shot into the intake port.

Were there any other glaring issues with the baseline configuration of the 2,0 that would be a good starting point to look for improvement?

Thanks for joining us and for whatever knowledge you'd be willing to share with us.