123quattro

Get me up to speed here. What turbos are you running again?

ptuomov

Still the old turbos: gt3071r-wg. 90 Trim .86 A/r turbine with an internal wastegate. 71mm 56 Trim .60 A/r compressor. The compressor is the same as in some gt2871r's.

Compressor map:
https://picasaweb.google.com/lh/phot...eat=directlink

Turbine map:
https://picasaweb.google.com/lh/phot...eat=directlink

BC

Why are you even continuing if its knocking? Its possible to tune out knocks almost completely. You may need to use methanol or ethanol spray to bring the octane to a more reasonable level - but the idea here is to create as much power as possible and find the limits of the block structure correct?

Making the power with knocks allowed will prove ****-in-shinola. All it will prove is that you detonate an engine that is operating in anger, you will blow it up. We already know that.

Find out what is causing the knock within the tune that you have, and eradicate it. We know its possible - that is - with the correct tools.

To be frank, you are essentially on a fools errand, and it irks me that when you blow this up, it will be written in the tides of rennlist that "the block can only handle x" when in reality you have shown nothing of the kind other than you can make a bunch of dirty, detonating power with the LH system on pump gas and you can blow it up when it detonates hard enough.

Use the very good hardware parts of the engine you have built and GET different software. WORK on the software to not allow detonation.

Fabio421

It's very clear that you don't understand what is being done and you're being rude in the process. Chill out and maybe ask a few questions.

BC

I understand very clearly what is being done. And what I wrote is in no way rude as long as we are men here and can stand some straight talk that doesn't involve hurty feelers. Why can't those statements I made be discussed instead of suggesting some issue with how it was said?

What is being done:

Sticking turbos on a motor that is not being controlled in a fashion to eradicate detonation.

End Result: Detonation and eventual issues related to same.

What does that show? Nothing about turbos, airflow, or tuning.

How is the OP going to tune out knock?
What features of the software he has available on the car will allow him to do so?
What are the combustion temps?
What are the A/F ratios? (now, this most recent runs)
What are the temps before and after the I/C units?
What duty cycle are the injectors at during different parts of the range?
What do the spark plugs look like after a run where there are "too many knocks"?

Again - in this thread "knocks" are some dark corner issue that no one wishes top speak of other than mentioning they are there. These knocks will kill the motor and then everything will start over and all these pages will be written with nothing new being learned, other than the falsity (mark my words) that the motor can take "X" amount and no more because OP tried.

Hilton

My understanding is that primarily what is being done is a massive data-gathering exercise - but thats just how I read this thread.

Question tho' - for those who know more than I.

If you're tuning on a repeatable dyno, to make the maximum possible power out of an engine, how do you know when you've got the maximum possible knock-free ignition advance for a given load/fuel/air pressure combination?

I'd have guessed that you know because any further ignition advance registers knocks, at which point you know where the boundary lies, and step back.

From what Brendan's saying, its possible to tune without seeing a knock ever? Presumably its based on theoretical models of combustion temps? (I'm not trying to be rude - I'm trying to understand.. I've only just started using my ST2 so more knowledge would be good).

BC

What data are we taking from this?

Depending on the tools, and who is doing the work, you can go right up to the edge before a machine set to hear the knock ever even does. Combustion in a given engine sounds and acts in a certain way. When it starts to act in a way that you understand to represent what happens JUST before it detonates, you can back off. This is done many times over at separate loads. People talk about "ragged combustion" and "temp spikes", or "anomalies" that start before it actually detonates.

When it does detonate, the cylinder is now attempting to "create" a bomb, not a combustion event. Numbers show that a detonating cylinder is seeing 10 times its normal "hp" or pressure. So you make 800hp. 800/8 = 100 each. 100 x 10. 1000 hp. 1000hp x 8 = 8000hp. Is the motor made to create 8000hp? Is it going to survive for even a split second? No.

If you clearly here any detonation when dynoing, or your sensors pick it up, you are already beating the engine up. Anything that happens after than only proves that you can blow something up. It proves nothing about tuning, power production, air flow possibility, or the strength of a system.

BC

Here is some light reading:

http://docsdrive.com/pdfs/medwelljou...07/349-356.pdf

There is an even better article testing engines with different fuels, I can't find it right now.

Fabio421

Dude, the knocks you are so worried about were only present at this dyno session. The last dyno session was ended because the waste gates were cracking open. New, stronger, waste gate actuators were installed which allowed John to reach slightly higher boost levels than before. at that point, according to Tuomo, there was knock. There was also a boost leak or some other anomaly that occurred that caused them to end the testing and tuning once again. John is taking TONS of data during all of these runs but I doubt he will make 100% of it public. You are only getting this much information because Tuomo chose to share it with you. Quit acting like you are an expert here. And while you're at it, please remind everyone of all the 928 projects that you have finished.

BC

I'm honestly confused by your response, specifically. What does a dyno run prove or any of the data collected if there is detonation? He has stated quite a few times before that he wants to blow this thing up. But that is a perceived power limit that is a false premise. I can't ask any of the questions above because I don't have a twin turbo?

Very strange.

ptuomov

I have been admittedly terse with my explanations of the recent experiments. Please allow me make a couple of clarifying comments in general and specifically about this most recent test:

John is a pro and I am an amateur. However, despite being an amateur, I enjoy theory and John's happy to try out some of my theories. Not everything I suggest pans out the way I expect it to.

We don't have anything like the data acquisition machinery that Jim Morton probably has or the multi-sensor wbo2 system that Todd Tremel has shown. That said, we log data and take notes. Furthermore, we run computer simulations that we try to calibrate to match the data.

The computer simulations are cheap. We run a lot of those. Actual dyno experiment sessions are expensive. When the car goes on a dyno, there's a specific experimental objective. We are trying to learn something. We don't go on a dyno without a question. We usually come back with an answer or with another question.

Not every experiment is about how strong the motor is. Some experiments are about that. Most are not. For example, the most recent set of experiments today were about figuring out how much boost we can generate at which rpms. The objective was not to find out how strong the motor was, instead it was to figure out whether the new wastegate springs solved the boost control problem we had. The answer is it didn't, but we have some leads where to look next.

Those experiments today were run on pump gas. The main reason is that it's cheaper to run them that way, rather than retune the ignition map for a race gas, and because we run them on Dynojet. Was this safe? I argue it was safe enough. It's really hard to break a 700 hp engine because of detonation on an intertia chassis dyno. This is not a load-holding Dynopack where you can burn an engine easily by holding it at a specific rpm. Instead, it's a quick sweep over a broad rpm range. Furthermore, this was run with the knock retard.

We learned enough today to say for sure that the next set of experiments is not going be run on a dyno or on a computer. Instead, it's an experiment on a test bench.

We're not a bunch of meth head tweakers randomly disassembling mechanical devices.

Hope this explanation helps.

Fabio421

I didn't say turbo project. ANY completed project would do.

BC

Plenty, with a fundamental, intensive, intricate knowledge of the mechanics at work. Do I need all that to ask the questions I am asking? What's with the gate keeper act?

Hilton

WE are taking whatever Tuomo shares with us.

I have my own theories about what he's modelling, and what variables he's anticipating changing, but they're based purely on conjecture and inference, so they're not worth posting, as I'd say I have maybe a 30% chance of being right.

Interesting - is there any electronic/electromechanical way of detecting these pre-detonation events? Thanks for the info, I'll have to do some research, although I suspect that any equipment to measure/detect knock precursors will be outside of my price bracket.

If its "judgement" or "experience" based, then that could be an interesting thesis for a Mech Eng. - using machine learning and suitable inputs (sensors, microphone, etc.). If it could be packaged, you could do some crazy stuff with ECU's.

dr bob

We tune pretty good-sized gas turbines with microphones on combustor cans, and do software analysis of the various sound patterns that combustion generates along with the combustion products. No such thing as knocks so no mechanical knock sensors. Fun stuff! There really is a difference between IC and EC engines though, so no direct correlation between what we listen for vs what you might listen for in the IC engine as a 'precursor' of real detonation. Something to think about for IC engines?