http://www.esbconsult.com.au/ogden/l...rs/phors13.htm

 

huh? where did this come from?

 

Man, this guy simplified the physic of car dynamics and brought it down to a simple big block of steel trying to change direction. The problem I see with this simplification is that 1) it takes the center of mass as a fix point, but we all know that depending on the setup of the car (suspention stiffness, rigidity of the chassis...)the CM will move during cornering, or acceleration, or braking and 2) He concludes with an exemple by saying that it is important to move the engine as close as possible to the CM to have a low PMI but he does not mention that the position of the CM in regards to the tires is a lot more important. Having a low PMI is by no mean the assurance of a good handling car. It is nice mathematic but not very usefull IMHO.


[Modified by JPP, 12:17 AM 1/11/2002]

 

Actually, his series of articles is pretty interesting. He simplifies things down a lot, but the concepts are sound. I haven't read this one, but his earlier ones were worth my time.

-Floyd

 

http://www.cosworth-technology.co.uk...ation_dyna.pdf

This is a neat presentation done at Cosworth showing the advantages of looking at engine transients on a transient dynanometer. In fact, many F1 and CART teams use transient dynanometers to simulate entire race circuits on a rolling chassis to test the relationship between demand (throttle angle), engine speed, and vehicle speed. They place high priority on the responsiveness of the engine.

Here is an old article on the Ilmor facility (scroll down to the subheading dyno detectives): check out the transient dyno for the engine.
http://www.cncmagazine.com/v4i12/v4i12c.htm

So we have 2 forms of transient response: suspension which most people here in autocrossing get as a concept. The engine transients are less intuitive. People focus on raw hp and torque numbers when the REAL racing teams focus on transients.

I recall someone was laughed at in this so called "high tech" board for bringing up the importance of engine transients. In fact, they called engine transients the equivalent of voodoo crap. The fact of the matter is anyone in automotive engineering can give you a dissertation of the importance of engine transients and at the application level, anyone in high levels of racing LIKE FORMULA ONE, can tell you the importance of measuring engine transients as the closest approximation of real world at the track performance. Steady state dyno outputs are meaningless to them.

Liar liar pants on fire.....

 

MD: dude, get over the hytech discussion already. Especially since I didn't call him a liar because of his work, merely because of what he may have told SCC.

 

hey dude, I'm just warming up....you're making it up as you're going along...If you believe he did it on purpose ...show me the money!


[Modified by Michael Delaney, 9:43 PM 1/10/2002]

 

**** man, I'll paypal you $10 for part of a stripper or hooker. Anyone else in on that?

Seriously. I'm done with the whole misunderstanding from the hytech post. And if you're that bored to hold on to it and continue to post with "i guess he's a liar too" then feel free.. that's kinda sad though.

 

whatsa matter? runnin' out of gas?

 

Post this on Super Honda's MB Mr. Delaney...hehe...

 

Not really. Just don't see the need to constantly redirect the conversation to the point I was making. Which has NOTHING to do with most of the posts in that thread later. And now we are turning this into the same thread. So I'm done here too. Later.

 

I like Yugo's.

Will

 

Me too. I'm taking the motor out of my conquest tsi and putting it in a Yugo

 

I'm amused. I looked at both of these links, and they don't really support anything you or John have said in part because they don't say much about anything at all (I'd embed a bunch of calculus notation here for effect, but wtf, I'm not trying to prove or sell anything or curry favor with anyone). You are talking Voodoo - not that I care all that much. You really can't hide inside variable output and variable load. And for what it's worth, those guys at Ilmor must be whack - John tells us that you can't learn anything on an engine room dyno - you've got to develop and tune at the drag strip to really maximize transient response and get true measurements (secret racing tip: it's part throttle operation that makes for really low ET's).

Here's something crude for you to consider. Imagine a motor that loads up when you're off the gas, and so it stumbles when you get back on the gas. We might refer to that stumbling as a transient phenomenon as we might smooth running at part or transitional throttle. A motor of otherwise identical specification that is better tuned and not exhibiting such behavior might be said to have better transient response - but that would be in effect writing off the first motor to a mystery that ought not exist but for ignorance, stupidity, or malfeasance. And but for the case of gross deficiency in the one case I find it hard to imagine such an effect dwarfing driver skill - even at the drag strip.

About all I can see that we can pull out of what you are saying then is that John is one of the worlds greatest tuners, because transients as I described them above aside, it's the amount of torque and horsepower at each infinitestimal point along the operating rev range that determines how fast the crank and car accelerate against the instantaneous load. And that is because that is all an engine can do, and that is why so many of us like area under the curve and nicely shaped curves at that. I am really amused that you set up a straw man to argue against by saying: "Steady state dyno outputs are meaningless to them". I don't know who you are arguing against with that.

I am willing to admit I could be wrong about many things I currently think, but neither you or John have written or presented anything about horsepower and this thing you guys call "transients" that can stand up to reasonable scrutiny. Maybe if you could have some of your friends from F1 write up something factual, logical, clear and concise - then it will all be cleared up.

For what it's worth I never called anybody a liar, I just said that John was Mr. Bullshit. There may be a difference, but it's situational and depends on transients. I'm waiting for a well written reason to change my mind.

Scott, who likes results....and nice hardware.....and people who can communicate.....and front engined V12 Ferrari's....and closure.

 

unlike you , I'm not as assured in the knowledge that engine transient is hiding inside variable load/output.

I'm not an engineer, let alone an automotive racing engineer so I can't pretend to defend with detail, the concept of non-steady state engine loading and response times. I do know that people more learned than me spend a great deal of money and time examining transients.

If you run on your browser search engine the terms transient dynanometer and racing and engine transients, you will get a whole slew of sites that delve into this.

I'm sure it's part of the curriculum in an introductory automotive course as much as Ackerman steering and the DeDion axle. The fact that Ford Racing, Cosworth, and Ilmour mention the use of transient dynos to simulate the car's performance when they don't have access to track time tells me it's not voodoo. They sure spend a lot of money on voodoo anyway if you are correct. I did find one university in the UK that has on their curriculum, formula racing car design (sign me up) and they only mention the role of transient response in the design of their intake and exhaust manifolds in passing without going into any details.

Speedvision had one of their commentators give a tour of the new Jordan Honda F1 facility and they had several transient dynos there as well. It seems that it is de rigour for any F1 testing facility.

Steady state performance does not tell you how an engine behaves as loads change. Brute hp may overcome or make up for lagging response but in the end how fast an engine reacts to changes in load must affect how you well accelerate and turn in transitions. Transient response must be the compensation if you do not have brute hp.

Maybe an engineer can explain it better than someone like me who is trained in the biological sciences and tried to avoid physics like the plague. I just don't think multi-million dollar high level competition teams throw money away on something that does not give them an edge or advantage...hence my conclusion that it cannot be voodoo. don't ask me to draw the force vectors to explain it.


[Modified by Michael Delaney, 11:29 PM 1/10/2002]

 

hey B18C5-EH2 , since you have graduated from Superhonda to here and now consider yourself advanced and amongst the elite, maybe you can explain transient response and engine transients for us or why it can or cannot be Voodoo...or do you have anything intelligent to add other than showing your arrogance (for which you have no basis)?

 

Well I, for one, am one that laughed at the transients. Reason being is that every time John was cornered on explaining it, he came up with some b/s crap that made no sense to anyone. I was never one to corner him on it, I just watched. Either he's not very well spoken, or doesn't have all the details himself.

But to put it all in focus here, remember, most of us here are dealing with street cars. We don't have the multi-million dollar budgets that F1 teams do to chase down very minute details for minimal gains at best. Most here are concerned if the part lines up, and performs well for the price they pay. Most won't ever have the need for a load based chassis dyno, as they spend the majority of their time racing at WOT.

Furthermore, this subject is as tired as a 65 year old prostitute, and I don't like ******* corpses that much

Finally, I'd like to add (with a touch of sarcasm) that out that no fast car of any breed has ever been tuned on a steady state dyno They are worthless tuning devices (rolleyes)

 

The study of transients as they refer to them (in distinction to whatever John means) is not at issue, and I do not question the usefulness of such dynamic load simulation in the development of road cars or racing cars - most typically for drivability and reliability testing and development.

Damn man - don't you want to get it: what makes the crank accelerate is the surplus of power deveoped with respect to the load. And again: who's talking to you about steady state? When you say brute hp you imply peak, when you say response you imply sub peak - both are numbers measurable on a dyno. You are either unclear or incoherent.

Your training in another field of science shouldn't impair your ability to understand or make good argument. You can't simply hold up "Auto Engineering 101" and wave it around and say QED. This topic is not so complex as to require anything more complex than a good descriptive argument - no fancy notation is needed. Seriously, if it's as easy as you suppose it to be why don't you just do it. Oh, it requires force vectors does it? You mean force like on a crank throw - that would be torque you know....damn, that would show up on any dyno. Try again?

Scott, who is glad he's only in this for fun.....

 

John,

Yeah, but you fucked it again anyway.

Scott, for whom the lights in the room just went on......oh man, I didn't know it was that ....

 

LOL

 

ROFL, must still have my beer goggles on from new years

 

I think that subject is dead, dead dead....kinda like me bring up my old pal fakedyn.

its dead. But I am thinking your here because there is no "there" anymore.

Jeff

 

please, god, don't go there... let's leave THAT subject dead too

 

THIS IS ******* RETARDED

Jason- who rarely uses profanity on the board, and who apologizes but feels it is prudent here...

 

obviously....that is very apparent from every one of your posts i have ever read. Quoting equations that you have absolutely no clue of what they mean proves nothing to me.

signed, an engineer