I was there for tear down,... I saw the suspect rod and crank, no detonation,....I have, and have had from the beginning a Zeitronix wideband for fail safe /data log/ and general monitoring of systems....... My engine wasn't destroyed,...it was one bearing in one rod.

That's great that you looked and also were running a wideband sensor AFRs/knock. I was just asking the question so we are sure the engine wasn't seeing det. Possibly it was an oil issue then.

Thanks for not taking my post the wrong way and as always for your information!

Also remember E85 is more stable... you dont see det as often. That doesn't mean the car wasn't tuned past MBT. And @cf6mech I am not in way shape or form saying that your tuner tuned it past MBT. But as far as I know it still possible to bend a rod via firing before MBT during compression stroke and have no detonation signs. At least thats what I have been told in the past... Someone correct me if I am wrong. I was just under the assumption that you could slowly bend that rod (or quickly) form being just past MBT and causing too much stress.

You see other users on E85 pushing 400+WHP on their car and they are still running. I would love to see a comparison of some cars that are and aren't running to see the ignition vs fuel at certain loads.

From my point of view for all i know cf6mech's new motor may just be stronger (or more flexible depending on how you look at it) than the previous one due to the bearing setup and more resistant to the shock of being close to MBT on E85.

Will do. I may just "gamble" on a set of bearings and just tune the car my self at this point so I can actually say what I did or did not do and show my actual tune in public unlike what other vendors would do. I am not the best at tuning in the world but then at least there would be "open" information. I am just trying to decide if I really want to jump in and throw money into a burning barrel at this point. So far I'm leaning towards yes... I'm having lunch with a friend who builds motors for a living to ask his opinion on the build and see if he wants to toss me a hand with my teardown. I plan on spending a lot of time on the dyno and actually checking my tune against MBT as I don't think my last tune was actually tested for MBT... (but that is a whole different discussion).

Hell if anyone wants to contribute to me doing a mid-build with OEM bearings I would gladly do lengthy tests on the dyno and post results of where i find MBT and report back testing. I put 25k miles on my car in 6-7 months. If anyone is going to find out how long term OEM bearings will last under conditions it would likely be me, especially considering my climate in my region. I'll obviously be trying to do this anyway but parts are pricey since the car is so new. So it will take me a while to piece everything together. ;) At this point I am looking towards buying an OEM long block. I am half tempted to test an OEM long block on the dyno for a bit and then tear it down and swap the internals. I wish more shops would post information on this. But then again this is how they make money, by having their reputable builds that they can sell by doing their own testing.

I also fully agree about this not being anything new. I am not new to the car scene. I remember when a number of motors were being seen as "weak" and little to no hope. Hell I remember the K series... that one was great. Everyone was complaining that they didn't accept any after market parts and were just horrible. And now look where the "threshold" is. I have a friend with a K20 that is practically stock that was putting close to the power of my first vortech setup.

Yeah, very possibly could have been what you state or oil like cf6mech thinks. I'm glad we can rule out detonation since nobody really learns anything there except for bad tune and everybody already knows that can destroy any engine no matter how robust. The whole cylinder pressure without det is very interesting topic though (especially with how E85 allows the tune to be so much more aggressive either NA or FI) as I had not thought of that until it was posted up, I just assumed it was det or oil.

If you want to tune it yourself, get help from the community, and also a little help from reputable tuners a solution like this probably would be the way to go:
http://www.ft86club.com/forums/showthread.php?t=46468

That is worthless to me personally. Remember OFT is just a "cable". Not a tuning platform or software suite. OFT is actually locked down extensively. I may however start contributing more to the open source guys and start working on a flex fuel setup for that. If you look in the ecuflash thread I have posted in there with trying to contribute with data logging ability. (i have built my own hardware data logger for this car that accepts ECUTek extended parameters). If you are not fully familiar with OFT please go find the OFT thread that was bashing on ecutek (whom im not a fan of either by any means, so dont think im on anyones side). Find my posts in there talking about what OFT really is. At least I think it was in that thread... As there is a number of people confused thinking OFT is a full blown suite for tuning. The developers of OFT use another companies software and literally just make hardware for reading / writing to the ecu. The owners were just kind enough to make some "optimized" base maps as well as an incentive to purchase their hardware. So i can't really "Contribute" to OFT as it is their project and their hardware and it is closed source. OFT is a device similar to the tactrix cable but slightly more advanced, and afaik doesn't follow the J2534 protocol which makes it a "closed" and propriety cable. Although this is of little use to know the difference to most end users since they are just using the OTS tunes provided anyway and aren't actually going to be tuning their cars them selves. However if I do testing on MBT thresholds on different setups that could be used on any platform may it be OFT + TunerPRO, the opensource guys, ecutek, whatever.

Sorry, didn't realize you want to actually change your tuning software via a community driven project. Thought you were just interested in tuning your car's tune/parameters which OFT does allow you to do I think (or whatever software it runs that is) versus something like Ecutek in which you cannot even change your car's parameters.

I didn't say what i wanted to do... I do however want control to edit my own tune in which ECUTek currently does not provide. OFT does not "allow" but if you use OFT to pull a ROM file you can use a number of software programs to edit the ROM just like a tactrix cable + ecuflash. (which is actually significantly cheaper but does not have ability to store roms or have a graphical display, and requires a laptop for flashing). OFT is not a platform, it is only a cable for datalogging & flashing an ecu.

But lets keep this on topic if you have questions regarding any of this please feel free to PM me and we can talk via there, or phone and ill gladly make sure everything is clear. :)

It doesn't necessarily have to be tuned past MBT to raise the cylinder pressure too high once you throw boost into the equation. Without cylinder pressure indication you can't be sure. There are limited options for that, but TFX engine technology does offer a system for this kind of performance use. It's going to cost a lot still. R&D is expensive no matter how you do it.

so @arghx7 do you have any charts showing the effect of increased mass vs the point of MBT? As in increasing air in the chamber which would result in increased fuel changing the density or mass of the atmosphere int he chamber which would change the burn rate and time it takes until the pressure reaches the piston? As well as different compression or deck height showing how it alters where MBT is obtained? Ive always wondered this.

You're talking about three different things: ignition delay (0-10% burn time), combustion speed (10-90% burn time), and combustion phasing for MBT.

In the ECU you set the spark timing. That's only when the secondary coil in the ignition system activates. There's a delay until the mixture really starts to burn--the most common way to represent this is the burn delay/ignition delay. That's the number of crank angle degrees from 0-10% burn. That's dependent on all sorts of things, but one of the big things is the amount of residual gas in the combustion chamber as a result of valve timing. Speed and engine load affect it, and once you talk about lean burn engines you have that playing into it.

The second thing is the combustion speed, which is often represented as the "bulk burn." It's the number of crank angle degrees from 10-90% burn. It's greatly affected by the design of the intake port (tumble and swirl flow) and also the geometric compression ratio. There's tons of other factors related to the fuel for example.

The last thing is combustion phasing. On a spark ignited, homogenous charge engine it's generally accepted that MBT is achieved when 50% burn occurs between 6-10 degrees ATDC firing. Usually the rule of thumb is 8. That doesn't really depend on a lot of factors: it's not that sensitive to engine load, engine speed, number of cylinders. I think a lot of it just the basic physics of reciprocating piston engines. The combustion phasing is not the spark timing. The spark timing required to get a 50% burn at 8 degrees ATDC varies according to changes in burn delay (0-10%) and combustion speed (10-90%).

Here are some charts from an experimental GM LNF engine (found in Pontiac Solstice GXP) showing peak cylinder pressure on E85 vs E0, running at MBT (50% burn between 6 and 9 degrees ATDC) on E85 and whatever combustion phasing was needed at borderline knock condition on E0.

http://www.ft86club.com/forums/attac...1&d=1385329362

http://www.ft86club.com/forums/attac...1&d=1385329362


But you'll never know what your combustion phasing, burn delay, combustion speed, or peak pressure is without a combustion analysis system. And without that info, it will be difficult to make a link between spark timing, peak cylinder pressure, and the bearing durability question. You need a cylinder pressure sensor installed, and then you need to run different spark timing under WOT pulls and see how that affects peak pressure with E85 or race fuel. That's going to cost money--a lot more than a set of aftermarket bearings.

Unfortunately it still comes back to trial and error... run a certain setup, see if it breaks, and speculate as to why it broke and what needs to be changed to prevent it from breaking again.

I'm attaching two papers. One has some discussion about combustion phasing/speed and engine efficiency. It's at part load condition though. The other is the study on an E85 version of the GM LNF engine that was in the Pontiac Solstice GXP.

You are an incredible resource, thank you for sharing with the forum.

I remember reading, it think it was in Crorky Bell's Maximum Boost but I could be wrong, that FI creates lower peak cylinder pressures then NA for the same power. As I recall it, the reason was that with FI more of the ignition stroke is used to provide power or something to that effect. Is there any truth to this, if so, would you mind expanding on the subject?

Thanks again @arghx7, this thread went a bit off topic but somewhat related. That GM document actually had most of the stuff i was specifically looking for such as turbine speed vs ethanol content to produce the same combustion pressure. After reading all of this and looking at the documents it just shows more and more that tuning E85 with the concept of knock feedback and detonation is more of a blind attempt at tuning. I remember when E85 tuning started I was told that a dyno was really required to get accurate MBT readings as with high powered pump gas cars you would hit a measurable knock feedback wall that you could tune with. But what i was under the impression was that with E85 this technique really doesn't work any more as you can easily push timing beyond MBT and from what you have posted shows a severe combustion pressure increase with no increase in power. Causing severe wear on internal parts. This just confirms the fact that I tell people that E85 isn't just a simple "plop it in" and use the ecu to auto tune out knock. You really need to use some sort of method to find MBT to tune correctly.

And you were spot on with me asking 3 things. I am also still quite curious on combustion time based off density. So regardless of internal strength take the same setup and theoretically fill the chamber to 1Bar with Lambada @1.0, then take the same scenario but at 2Bar and Lambada @ 1.0, In these two scenarios how much is MBT affected?

Well I'd have to see the exact text here. NA engines simply can't get more than maybe 16-17 bar IMEP (work before pumping and friction is subtracted). Boost can do a lot more than that, but has knock issues on pump gas so how do you compare? The same relationship I described earlier still exists. If the combustion is significantly retarded for knock relief, the peak pressure will be lower and display the "double hump" characteristic shown here:


http://www.ft86club.com/forums/attac...1&d=1385344300

while an MBT pressure trace at the same given torque looks more like this:

http://www.ft86club.com/forums/attac...1&d=1385344300


Are you asking how combustion speed is affected by charge air/load at a fixed rpm? Generally speaking I'll say that the burn delay (0-10%) is longer in the low speed low load range, which requires earlier spark timing for a given combustion phasing (location of 50% burn and peak pressure). Otherwise it's too complicated of a question and depends on too many things like valve timing, mixture motion, spray pattern.