m42racer

My Gosh, Kibort, you are in need of an attitude adjustment.

If your station in life is racing an old 928 tuned on a chassis dyno I'd get off your high horse and maybe look and listen to how this engine was mapped. Often when this is done we learn something we did not know.

It is my understanding this engine was mapped on an engine dyno with a very good EFI system. The engine was held in each "cell" for some time to produce the best safe torque. This does not always result in "so called" perfect AFR numbers. You tune for best """SAFE""" torque not an AFR number. If the engine likes it rich at a particular cell, and makes its best torque there, would you lean it out just to have a perfect AFR number. I guess not.

I am sure this engine is like almost all others. They do not always map the way we think they should. Maybe this is why real engine builders use an engine dyno to map engines and not chassis dyno's.

BTW, I have some engines that show similar AFR curves to Greg's, when a sweep test was done. They also showed less observed Torque at each of the recorded RPM's. But when the engine was held in one cell, the AFR number was different and the engine made its peak torque. I guess that is why the real engine tuners hold the engine in one cell and let the engine settle and record only the setlled Torque, while cowboys want only the number that often results in a sudden RPM change.

Now go feed your horse.

mark kibort

Hey, i was only debating the natural response time of the o2 sensors. since there is some settingling time if you old an rpm with all the other things that happen in steady state, I understand.

my point was only to the responsiveness of the 02 sensors

Plus, there is a chance that when going through the rpm, that it is leaner than it should be, as greg pointed out, for steady state, so my way just builds in the safety margin. If my tests and others were a full point off, there would be a lot of cars running at 14.7 (stoich) and burning holes in pistons.

I think it is you that needs to get off the high horse. I state EXACTLY what you do below. I have the safe shotgun tune and Greg is surgical in his tune.

we were just having a discussion about the lag time. could be a lot of reasons he has seen these kind of things. I was just interested in why, because the system seems to support almost instantaneous response

Again, i agreed to go to the chassis dyno and hold a constant rpm and match against the sweeping RPM acceleration. are we all that closed minded to not find that kind of verification confirmation or test, interesting?

now , feed this to your horse. If you do the test one way, and the dynamic test shows results that are different. If you use the engine in a dynamic fashion, (as long as the sensors are right) wouldnt you be curious to see if there was any differnce. maybe dynamically, one tune is better than statically. maybe the temps held statically raise the combustion chamber temps to a higher temp vs passing through them in an rpm sweep. Just a thought. (I dont know, thats why im bringing it up)

m42racer

My horse gets feed all too often, unfortuntely. My bank balance shows this.

I guess I would always error on the side of data that I knew was correct based upon good sound engineering, and not the data that often comes into play all too easy to accept as been real.

GregBBRD

So, do you think the quart or two gets pushed into the intake system, from the heads...or do you think it is slipping past the rings/etc. and getting burned?

cold_beer839

I know this is off topic, but why is Greg Brown not a Lifetime Rennlist Member?

Who is more qualified for that recognition than him?

S4ordie

Because he's too busy to watch another repeat of the Burning Bed with Farrah Fawcett.

BC

There is a huge lag in response when you are actually paying attention to what the wide bands are reading - which is quickly cooling gases at what seems to be over three feet from the exhaust valve.

There is a way to do this, as Greg has shown, where you are not going to the edge, but also not trying to kludge something from a much too gross-measurement and application standpoint.

I know this engine is not seeing and will never see boost, but when Todd was tuning, because of the parameters, he was technically at the edge of a hypothetical envelope. So he thought - "I should get the 02 reading from the port, not the exhaust primary" (or in most cases, the collector). When he did this, he found some very interesting info that would NEVER have been found with a collector based sensor, not only because of time lag, but also cylinder differences.

This engine is individually throttled, so I would assume (possibly wrongly) that there is not so much of the latter. But obviously the former.


I was taught a way of thinking that removes certain forms of bias when I was learning early in my career. It may seem obvious, but it removes a characteristic, or an "issue" and then posits the question again. Like this one:

If the difficulty/cost/complexity of USING an engine dyno as opposed to a chassis dyno was REMOVED - what would the outcome be? Sounds ridiculous, but give it a moment....

I would suggest that everyone would use an engine dyno. When money is no (or less of an) object, what do people use? An engine dyno. What do manufacturers use? An engine dyno. F1 goes so far as to map an engine TO THE TRACK, through dyno simulation.

Its a much more finite analysis and measurement of what an engine is doing. We can Kabitz about what else works "well enough", but the right answer is already there.

soupcan

Curious how and or if the 4" of extra header primary length is factored into the final tune.

GregBBRD

Not factored. Ignored like it never happened....

We have no way to figure that out, without removing those pipes....and it will not fit on the dyno without them. I've talked to several exhaust people about this problem. Their thoughts were all very similar, in that they felt that with and without the pipes, the torque curve might move around a few hundred rpms, maximum.

blown 87

Twelve hour days will do that to a fellow.

Ra928

Am I the only one interested in hearing what the oiling fix is? Let's hear it.

GregBBRD

Like everything, it is a "work in progress". We will be testing Beta Version 2, very shortly.

Beta Version 1 works great, but is a bit....complex. Although this problem has been around for 20 years, I felt like I had one shot to fix it.

Andy has been very patient, about this engine....but I felt we really needed to solve the problem and get his car done.

andy-gts

He surely doesn't advertise or sell on rennlist because to took me forever to figure out how to contact him 4 yrs ago...... But his shop is sure cool!!!!!

928mac

I would not have guessed that Greg.
Maybe I didn't read the thread close enough but I have seen worse and wouldn't think either of you deserved warnings.
I have, rightly so been warned, for . . . well ILL leave it at that.

I like to read the banter back and forth from the racers and builders as it keeps the show honest.

I am learning a lot from all of you guys and have just discovered another issue with my injectors and fuel rail
that I will have to give some thought to.

Hilton pointed me to a thread where there was some concern with Carls fuel-rails.
I think it will be ok, after reading the thread, but I have to do some more test fits and right now I am not quite at that point.

I"M glad the stroker dyno tested out ok Mark, with no valve float or any other issues.
Andy should be very happy.

IMHO, Racing has always been competitive. I know that at the track when I raced there were some major scraps.
In here it can get kind of tense but I think if the language is kept decent, then you guys should be able to hash it out. IMHO.

blown 87

"This is America, where you can get all the justice you can afford."

That is a quote from Larry Melnick, who is my friend and a Yankee Jew lawyer, he said that to me 20 something years ago, I did not understand how true it was at the time, but he did understand it, and he was 178% correct.