Widmer Terms.....

[SStrokerAce]

Larry obviously has a better grasp of this stuff than most of us do and although I get his writings some of his terms we all relate too but don't get into a lot more, and this is about the only place we can discuss them further. If you think he's full of BS then just don't post here.

The first one I understand, and the concept of getting from point A to B is the key which we are all after, but lets still talk about this one more.

Transient Response: "Let’s go to the mystery area that’s really what makes the car run….or accelerate. I call it Transient Response or Recovery Time. How long does it take for an engine to recover from being yanked down 2000rpm on a shift and accelerate back to the redline again….that’s the mysterious quality that all killer engines have, and it’s not something that will show up in "conventional" dyno testing. Quite the contrary, I’ve NEVER seen an engine that possessed this quality make big HP.......The only "number" I’m concerned in is: How much time does it take this engine to accelerate a given "load" from point A to point B. If the rpm range you anticipate operating in is for instance from 5000 to 8000rpm, the combination that will pull the "known load" from the bottom to the top the quickest will ALWAYS be the engine to run regardless of HP."

We could also call this pressure recovery as well.....

Now the 2nd term, I'm lost as to what he's talking about. Only thing I can think is how the pressure waves act when going into a plenum.

Steam manifolding: "There’s also a "black art" that I’ll mention regarding state of the art cylinder heads, and that’s steam manifolding. The design and construction are a pure art form, and if it’s not done correctly, you won’t be in the hunt. That’s all on that subject."

Most of this is found in http://www.theoldone.com/archive/pro-st ... engine.htm

I know Larry is around here from time to time so maybe he can extrapolate on this further.

Bret

[airflowdevelop]

Bret,
Although Pressure recovery has a great impact on pulling the gear. They are 2 different terms by my dictionary

[beth]

Transient Response: "Let’s go to the mystery area that’s really what makes the car run….or accelerate. I call it Transient Response or Recovery Time. How long does it take for an engine to recover from being yanked down 2000rpm on a shift and accelerate back to the redline again….that’s the mysterious quality that all killer engines have, and it’s not something that will show up in "conventional" dyno testing. Quite the contrary, I’ve NEVER seen an engine that possessed this quality make big HP.......The only "number" I’m concerned in is: How much time does it take this engine to accelerate a given "load" from point A to point B. If the rpm range you anticipate operating in is for instance from 5000 to 8000rpm, the combination that will pull the "known load" from the bottom to the top the quickest will ALWAYS be the engine to run regardless of HP."

I completely agree with this statement. Engine requirements change with changing loads. An engine combination has to be matched to the load. An engine designed for small loads will have different requirements than one that will be subjected to very high loads. The lighter the load and the quicker the acceleration the farther the combination will be from maximum torque as measured at a stalled steady state.

[MadBill]

Seems like some of the high-end programmable dynos could simulate this. After all, if Ford could accurately dyno-simulate every lap of 24 hours at Le Mans back in the sixties..
All you'd need is a sturdy dyno and a good controller that could manage say a 600 RPM/sec. pull to redline, then slam it back down 2-3,000 revs and run it up again at maybe 400/sec., etc...

[Justin Jones]

Transient response is a term I've heard used by others as well as Larry, for instance:

http://www.hasselgren.com/services.html

AVL 850 HP/14000 RPM
• Steady state, Transient response and Endurance testing

[Ed-vancedEngines]

Obviously there must be more uses for one word and this one is sure fitting the bill.

Last time I was in an industry where the word Transient Response was used was connected to audio speakers. It is also used in other forms of electronics.

It is knda strange seeing it being used connected with automobile performance but I guess in a wry sort of way it is still talking about the same thing.

Ed

[Boss 330]

Seems like some of the high-end programmable dynos could simulate this. After all, if Ford could accurately dyno-simulate every lap of 24 hours at Le Mans back in the sixties..
All you'd need is a sturdy dyno and a good controller that could manage say a 600 RPM/sec. pull to redline, then slam it back down 2-3,000 revs and run it up again at maybe 400/sec., etc...

How about a simulated lap of Monza?
http://videos.streetfire.net/Player.asp ... engine&p=6

[MadBill]

Yes, something like that! (Except that for example, a 500 BBC in front of a Powerglide might see a little more RPM drop than a current F1. They appear to shift at ~ 19 and change and drop to maybe 17.5, a mere 9% or so...)

[Ron E]

OK, I can't get into the transient-response part of this until I get some help with some of the things I'm reading over there. Just as a starter:



The flow rare for the intakes is 618 cfm @ .800" lift and 675cfm @ .800" for the exhaust ports. These values are only for comparison and are at a pressure drop of 28" H2O. We develop and flow components at "different" pressures than the "norm". The exhaust port will reach 85% of the above # by .400" lift. These lift #’s are not necessarily indicative of the lift #’s currently run in prostock as some cams yield over 1.0" net lift. I will say this, however, I feel the same way about valve lift as I do about rpm.
The material for intake valves is beryllium and the exhaust valves are titanium

[Ed-vancedEngines]

Ron,
I noted the dates of the postings. 1998 was one of the dates there.
I do not see or understand what any of that page has to do with Larry Widmer though. I did not even see him there.

Ed

[steelcomp]

I do not see or understand what any of that page has to do with Larry Widmer though. I did not even see him there.

Ed

Larry was the supposed writer of that "essay".

Top of the page:

Posted by T.O.O. on June 20, 1998 at 20:14:11:

The PRO STOCK RACING ENGINE

[steelcomp]

Transient Response: "Let’s go to the mystery area that’s really what makes the car run….or accelerate. I call it Transient Response or Recovery Time. How long does it take for an engine to recover from being yanked down 2000rpm on a shift and accelerate back to the redline again….that’s the mysterious quality that all killer engines have, and it’s not something that will show up in "conventional" dyno testing. Quite the contrary, I’ve NEVER seen an engine that possessed this quality make big HP.......The only "number" I’m concerned in is: How much time does it take this engine to accelerate a given "load" from point A to point B. If the rpm range you anticipate operating in is for instance from 5000 to 8000rpm, the combination that will pull the "known load" from the bottom to the top the quickest will ALWAYS be the engine to run regardless of HP."

I wish the folow-up to this page was available.

I've asked this question a hundred times and no one has been able to answer it (to my liking)...
What makes an engine accelerate?

[SteveS]

FWIW, I tend to believe that transient response defines the capacity of an engine to recover from an abrupt change to a lower RPM.........such as that which occurs during a shift......and then ability to rapidly recover the lost RPM and in the course of doing so accelerate the vehicle. In these terms, I want to think in terms in breadth of power and recovery of port velocity.

[Ed-vancedEngines]

The name making those posts was TOO.

The subject of the thread was about Widmer's Terminology.


Ed

[steelcomp]

I believe it relates to building an engine with as much "useful" power as possible. Peak numbers don't mean much if you can't get to them. An engine with a wider power band is going to perform better than one with a narrow band, even if peak numbers are slightly less. Higher "peak" numbers usually relate to higher rpm, more shifting, and more opportunity for parts wear and failure, not to mention missing the power band.