Exactly, so low and behold the driver be ignorant that the car is knocking on poor fuel. "everything seems fine!"..

Well yeah, you can modify the code, add some jumps, edit some of the table data with a hex editor, etc. Remember I said: "I don't want to get into the whole CFI war again, but this is part of why I don't understand why folks modify CFI setups - you can't tune those ECMs. I guess there is a few things you can do with a hex editor, but nobody does."

Well I guess nobody is not true, you do. In 'stock' form with no additional tables or code added, do you have a ecu/tdf file ?

That is what I said - when it detects knock it will retard, then decay. When it detects more knock, it will retard then decay again.. Over and over and over again.

I then said newer ECMs (such as the '727) have 'low octane' routines, that when a knock threshold is met will permanently reduce advance until the vehicle is restarted.

What newer ECM's? I've seen some late model vortec stuff with the knock sensor in the lifter valley, but I have not seen an example of code that will do this. AFAIK even the early LT1 stuff has no idea which cyl is being fired next.

Regardless of that, by 'newer' ECM's I was referring to the later L98 cars, 90-91. I believe the early LT1 cars have the same octane routines. I cant vouch for the later LT1 stuff, nor the LS1 stuff.

-- Joe

 

I have 1989 and using regular for years, with no complaints.

 

Ignorance is bliss.

-- Joe

 

Isn't the CR only 9.5 to 1?

I run 89 octane 90% of the time, and the odd tank I put in the good chit.

 

I retired from doing ESC calibration in '95 (got tired of living out of a suitcase), so the LT4 and LS1 stuff is not anything I dealt with (LT1 and LT5 were the latest I was involved with). When working on prototype/development vehicles, each base ECM had its own code and algorthms. It was a learning process each time I worked on a different vehicle platform/ECM.

 

If it isn't knocking and if the timing isn't being retarded because of "knock counts" being sensed, more octane will gain you nothing.

RACE ON!!!

 

Absolutely.

Most of them knock though, at least on the 87 fuel around here.

-- Joe

 

I think you might be a bit harsh here. Several factors determine the probability of knock occuring. Low limit on the production compression ratio, high humidity, modest coolant temps, aluminum heads, driving style, etc, all can reduce the likelihood of knock.

 

I don't think I'm disagreeing with you here. The driver isn't responsible for 'hearing' the knock true, but if the vehicle was suggested to run on a certain octane OR if the fuel quality over the years has gone down (which it has) the owner should put the proper fuel in. This will differ with location and where people buy fuel.

This does not seem to differ from what we're doing, but I'm still confused on one aspect and I spent some good time searching on this (again). The calmap for the CFI stuff has not been publicly hacked. How do you know where the calibration is, the table sizes, etc? Did you develop your own definition file based on prior employment experience?

See, I'm talking about the average Joe. The average Joe can't download a Bin, the calmap definition file, and start tuning because it's not available. Everyone I've talked to with a CFI has either replaced the ECM, or does mechanical changes to fuel pressure or distributor advance.


I understand the technology is available, but do you have any examples of where this is used in production, and is it on any C4 Corvettes? I've yet to see it, but again I've not played with the later LT1 stuff so I didn't want to discredit the info.

Sounds like you have a wealth of experience with this stuff. I'm glad you chimed in.

-- Joe

 

I know, and for some vehicles 87 might be the recommended octane. I'm not trying to be harsh, but say you have a late model C4 for example that says "premium fuel recommended" and you run the cheapest gas on the block and then go post saying "its fine" well, I ask that poster, how the heck would you know?

And that is the whole point for the thread here. Blinding saying 'this octane will work fine for everyone' is a defective statement, because it may not work for everyone, and it might not even work for you and you might not even know it!

-- Joe

 

Which is why, back in post #2 of this thread, I recommended that the OP run a TEST to see if a lower octane suits his needs under HIS operating conditions.

My car doesn't knock with 85 octane, even when racing. Yours may.

Octane isn't a "If somes good, Mores better" proposition. Any more octane than needed is a waste of resources.

RACE ON!!!

 

WOW!! [says the Rock?] This sure got complicated?

Knock aside, and not trying to change the subject, but how does one cylinder get retarded in an 1989 model???

I could believe it with OptiSpark but I am still picking up little bits of my brains, after it exploded trying to figure out how that happens in a distributor?


TJM

 

You should take up space on the Mastercraft Forums. You''d fit right in over there. (there's only one way to do "it")
http://www.mastercraft.com/teamtalk/index.php?


So is blindly saying that it won't...which is what you're doing, or implying.

 

Well, it's no different than modifying the breaker cam on a points distibutor to get eight different advances. (Modern distributors just doing it electronically instead of mechanically.) I believe Smokey Yunick did a similar thing with his distributors back in the sixties.

 

Don't know about a "wealth of experience", but it was an interesting job for several years. Drove a lot of neat cars, and met a lot of very smart people along the way, and I suppose I learned a few things that came in handy on occasion.

 

I met Smokey in 1969, while serving at NAS Jacksonville. Quite a character.

I was a Small Block fanatic and fascinated by the 302 Z28 motor, so I just went down one day. He just treated me like I was some country cousin.

We ended up talking for about an hour [ actually I talked about 3-1/2 minutes and listened a lot ].

Saw some really neat stuff. Learned a few things that stuck.

I still can’t see the mechanics for a varying the timing for one cylinder of a mechanical distributor?

But don’t kill yourself trying, pretty esoteric!!

TJM

 

I envy you for getting to talk with him. He was on my list of people I would like to sit down and BS with over a beer or coffee.
Regarding timing, a key thing to remember. A sbc can be thought of as eight single cylinder engines all tied to the same crankshaft. Each cylinder sees a slightly different A/F mixture, VE, and coolant/cylinderwall temp. They all theoretically need a different advance curve or timing at any particular RPM. In a points system, all the breaker cam lobes are 90 crank degrees apart. If you machine the lobes so that some are 88 degrees apart (or two degrees moved from the ninety degree point), the points will open sooner, causing the timing to change on that lobe, and its corresponding cylinder. It's my understanding that Smokey did that on some of his engines.
With EST distributors it's just a matter of software.

 

Are you sure? It seems the EST (and any HEI) distributor simply substitutes the reluctor or pole piece and pick up coil for the cam and points. I would think you would need a special pole piece like Smokey's special cam to duplicate his results with an electronic distributor. The HEI Corvettes (EST equipped or not) don't utilize a crank shaft positioning reluctor to tell a computer what cylinder is firing. Are you sure software is all that is needed?

RACE ON!!!

 

Well, yes and no. I tried to make some reasonably light reading on the previous comments, but the following might make for some dry reading. A crank sensor won't tell you any more information than a distributor will. The crank sensor has the benefit of no chain slop error, but theoretically you can put the same resolution sensors on each setup, giving you crank position (or piston position, obviously). The downside of the crank sensor, versus a cam or distributor sensor, is that while the crank sensor can tell you when the piston is at TDC, it can't tell you if it is TDC compression or TDC exhaust. A distributor or cam sensor signal is needed to tell which part of the stroke that particular piston is at. Once you know which stroke that piston is at, then you know when and where every other piston is moving, and you can modify the timing for each cylinder individually, if you wish, and if the software is set up for that. Modifying the timing is simple, and is done just like it's been done for several years. If you know engine speed (easy to do by measuring the time between tooth pulses to the ECM), and knowing that there is 90 crank degrees between tooth pulses you can calculate the time it takes for the engine to rotate each of those 90 degrees, and then add or subtract a couple degrees onto the normal setting.
The HEI setup is a bit different. Easier in some ways (no software to deal with), but harder to do because of the way the pole pieces are made. In the HEI setup, all eight points of the reluctor wheel line up with the eight points on the magnet. This just gums up the works. A Chrysler type pickup coil (like I put in my Corvette distributor in 1973) has a single pole magnet piece, along with eight points on the reluctor wheel. It would be simple to modify that type of setup to move the location of any of the reluctor teeth. Some of the other aftermarket distributors that use a Hall sensor or infrared LED shutterwheel setup could also be modified if desired.