Source for Campy CT chainrings?

[jim beam]

Ben C wrote:
> On 2008-01-19, [email protected] <[email protected]> wrote:
>> Michael Baldwin writes:
> [...]
>> In most engines, exhaust valves are smaller than intake because
>> exhaust has lots of pressure and compression push behind it while
>> intake has atmosphere. On top of that, exhaust valves have a smaller
>> area to absorb heat from passing hot gas but the valve stems are often
>> the same size as the larger intake valves. For production this is an
>> advantage for valve guides that can be the same for both valves.
>>
>> To visualize this better, there is a good dynamic model on Wikipedia:
>>
>> See desmodromic section:
>>
>> http://en.wikipedia.org/wiki/Four-stroke_cycle_engine_valves
>
> And better be quick before someone reverts Jobst's edits again

lol!

 

[jim beam]

Michael Baldwin wrote:
> Dear Jobst, my question was;
>
> I'm assuming that these phased centers are advanced or retarded in
> relationship to piston TDC timing , no?

and you expect him to give you a straight answer? he really doesn't
know otherwise he'd have condescended on it already.

in the mean time, here's something to look at:
http://www.porsche.com/usa/models/911/911-carrera-s/featuresandspecs/?gtabindex=2

click on "variocam". - toyota's variable valve timing married with
honda's selectable cam profiles.

i believe that prior to this, porsche [and mercedes] played about with a
design that used pulleys to pull at slack in the timing belt/chain that
adjusted the cam timing a few degrees. but that only adjusts timing and
doesn't offer the benefits of switching profile [lift and duration].
doubtless you can check that history for yourself.

>
> Short answer is;
> *Advance the cam timing for "low-end" power. *Retard the cam timing
> for "peak" power.
>
> Modern engines with variable camshaft timing do in fact have broader
> power bands.

indeed.


>
> ..but thanks for the Wiki stuff...the cut-away 4T, DOHC engine gif. was
> especially fun...

if sufficiently bored, check out the correspondence history on that wiki
page! classic jobst.


>
> Sir, there's really no need to continue this charade. You're
> embarrassing yourself.
>
> Sincerely & Best Regards Always
>
> Mike Baldwin
>

 

[jim beam]

A Muzi wrote:
> -snip engaging OT cars-
> jim beam wrote:
>> i have direct comparison of cam profile effects. two hondas,
>> identical motors, one with the stock soh ["low rev"] cam, the other
>> with a soh zc ["racing"] cam.
>
> soh cam?
>
> Acronymfinder wasn't helpful, web search turns up references to a man
> named Cam Soh...
> What is it?

i could have written "sohc cam", and that would have allowed you to
search the acronym, but if you'd been following the thread, knew cars
and knew my dislike of redundancy...

 

[jim beam]

Tom Sherman wrote:
> Clive George wrote:
>> "Tom Sherman" <[email protected]> wrote in message
>> news:[email protected]...
>>
>>> In the 1.6L VTEC engine used in the 1992-95 Si/EX, the change in cam
>>> profiles at about 4800 RPM was quite noticeable as a "bump" in power,
>>> while the 1.7L VTEC in the 2002-05 EX has a seamless transition -
>>> except for the wider than normal power band, one would never realize
>>> the VTEC was there.
>>
>> I've heard that the VTEC in the normal models is set up to be like
>> that - but the ones in the fast ones (Type-R over here) still have a
>> distinct bump - possibly to give the buyer reassurance that what
>> they've bought is working.
>>
> Well the 1994 Si was certainly marketed more towards the performance
> crowd than the 2005 EX Sedan, so it would not surprise me if this
> difference was deliberate on Honda's part.

deliberate enough to have a whole different engine - the b-series b16
dohc vs. the d-series d16 sohc.


>
>> (does the second cam on a type R working between 6000 and 8000 rpm
>> sound about right? Part of the reason honda's NA engines manage such
>> good specific output is their ability to rev high.)
>>
> Yes, I would imagine that some lower RPM torque would be sacrificed in
> the Type R for high end power. High peak horsepower sells in that
> market, even if the car is no faster overall.
>

 

[Tom Sherman]

"jim beam" wrote:
> A Muzi wrote:
>> -snip engaging OT cars-
>> jim beam wrote:
>>> i have direct comparison of cam profile effects. two hondas,
>>> identical motors, one with the stock soh ["low rev"] cam, the other
>>> with a soh zc ["racing"] cam.
>>
>> soh cam?
>>
>> Acronymfinder wasn't helpful, web search turns up references to a man
>> named Cam Soh...
>> What is it?
>
> i could have written "sohc cam", and that would have allowed you to
> search the acronym, but if you'd been following the thread, knew cars
> and knew my dislike of redundancy...
>
Not a fan of the Cadillac Seville STS, then?

--
Tom Sherman - Holstein-Friesland Bovinia
"And never forget, life ultimately makes failures of all people."
- A. Derleth

 

[Tom Sherman]

"jim beam" wrote:
> Tom Sherman wrote:
>> Clive George wrote:
>>> "Tom Sherman" <[email protected]> wrote in message
>>> news:[email protected]...
>>>
>>>> In the 1.6L VTEC engine used in the 1992-95 Si/EX, the change in cam
>>>> profiles at about 4800 RPM was quite noticeable as a "bump" in
>>>> power, while the 1.7L VTEC in the 2002-05 EX has a seamless
>>>> transition - except for the wider than normal power band, one would
>>>> never realize the VTEC was there.
>>>
>>> I've heard that the VTEC in the normal models is set up to be like
>>> that - but the ones in the fast ones (Type-R over here) still have a
>>> distinct bump - possibly to give the buyer reassurance that what
>>> they've bought is working.
>>>
>> Well the 1994 Si was certainly marketed more towards the performance
>> crowd than the 2005 EX Sedan, so it would not surprise me if this
>> difference was deliberate on Honda's part.
>
> deliberate enough to have a whole different engine - the b-series b16
> dohc vs. the d-series d16 sohc.
>
Well, no. My 1994 (5th generation) Civic Si had the 1590 cc SOHC D16Z6.
The only 5th generation Civic (in the US) available with the 1595 cc
DOHC B16A3 engine was the Civic del Sol.

My 2005 EX sedan has the 1668 cc D17A2 SOHC engine.

--
Tom Sherman - Holstein-Friesland Bovinia
"And never forget, life ultimately makes failures of all people."
- A. Derleth

 

[Tom Sherman]

Clive George wrote:
> "Tom Sherman" <[email protected]> wrote in message
> news:[email protected]...
>> Clive George wrote:
>>> "Tom Sherman" <[email protected]> wrote in message
>>> news:[email protected]...
>>>> Clive George wrote:
>>>>> "Tom Sherman" <[email protected]> wrote in message
>>>>> news:[email protected]...
>>>>>
>>>>>>> (does the second cam on a type R working between 6000 and 8000
>>>>>>> rpm sound about right? Part of the reason honda's NA engines
>>>>>>> manage such good specific output is their ability to rev high.)
>>>>>>>
>>>>>> Yes, I would imagine that some lower RPM torque would be
>>>>>> sacrificed in the Type R for high end power. High peak horsepower
>>>>>> sells in that market, even if the car is no faster overall.
>>>>>
>>>>> I've not heard about the Type R's being slow at all. It might be a
>>>>> bit painful on the ears to use the full power, since it's at the
>>>>> high end, but the low end isn't sacrificed for that.
>>>>>
>>>> The higher changeover point from the low-speed cam lobes to the high
>>>> speed cam lobes means that the low-speed lobes need to work to a
>>>> considerable higher RPM (ca 6000 RPM versus ca 5000 RPM). This will,
>>>> of necessity, compromise low-end torque output.
>>>>
>>>> It would not be surprising if an engine with slightly less top end
>>>> power but more midrange torque made the car as fast overall.
>>>
>>> Not necessarily - provided it can be kept in the high end all the
>>> time, which it can be, it'll be fastest the way it is.
>>>
>> True, but one needs a close ratio gearbox to keep the engine in a
>> narrow power band, which only works on the race course and not the
>> street. Note that except for F1, pretty much all non drag racing
>> events use rolling starts. Your typical race car is not something that
>> would work well in stop and go traffic, which is not acceptable in a
>> car sold for street use.
>
> Ah - you perhaps missed that the powerband with the second cam isn't
> actually that narrow - it may start high, but the engine does go a lot
> higher than most car engines. So you don't need the very close ratio box.
>
Note that we are talking about small differences in performance here.
However, it is much harder to keep the engine between 6000 and 8000 RPM
than between 4000 and 7000 RPM while driving on the street with the gear
ratios available in the stock transmissions. In real world use (not the
race track), the engine with peak torque between 4500 and 5500 RPM will
likely offer better performance in most situations than one with similar
peak torque occurring between 6000 and 7000 RPM.

--
Tom Sherman - Holstein-Friesland Bovinia
"And never forget, life ultimately makes failures of all people."
- A. Derleth

 

[still just me]

On Fri, 18 Jan 2008 23:56:22 -0600, Tom Sherman
<[email protected]> wrote:

>> 'course in real life, the lazy man prefers the lower grunt of a turbo...
>>
>Turbo lag is almost as bad as waiting for a slushbox to shift down.

Another design issue. Just like cam design, you can design out most of
the "lag" by adjusting other parameters based on intended driving
style. Twin turbos (small/large) are another solution. And, if you put
a turbo on an engine that already has a fair amount of power, lag will
not show up at all.

Regardless of the design though, turbo rush always make up for any
turbo lag.

Still "real men like to get blown" Me.

 

[Michael Baldwin]

Jim Beam suggests

>i believe that prior to this, porsche [and mercedes] played
>about with a design that used pulleys to pull at
>slack in the timing belt/chain that adjusted the cam timing
>a few degrees. but that only adjusts timing and doesn't
>offer the benefits of switching profile [lift and duration]. doubtless
>you can check that history for yourself.

I was part of the original design/process/manufacturing _team_ that
worked on the GM/Oldsmobile engine that was to become known as the
Quad-4. The engine's engineering designation was 4-83 (then GM "code"
for corporate approved funding as of April of 1983)

The final production version ended up with being a 2.3L inline four
with chain driven DOHC's. We had variable cam timing, lift and duration
prototypes that we knew would never get corporate approval ($$$) We
also knew (can't say how) that TOYOTA had the capability to produce such
models as early as 1981-82.

My simplistic questions of Jobst were deceitful in nature. They were
intended to serve as a means by which to out him. I take no pride in
such behaviour.

Best Regards - Mike Baldwin

 

[Clive George]

"Tom Sherman" <[email protected]> wrote in message
news:[email protected]...

> Note that we are talking about small differences in performance here.
> However, it is much harder to keep the engine between 6000 and 8000 RPM
> than between 4000 and 7000 RPM while driving on the street with the gear
> ratios available in the stock transmissions. In real world use (not the
> race track), the engine with peak torque between 4500 and 5500 RPM will
> likely offer better performance in most situations than one with similar
> peak torque occurring between 6000 and 7000 RPM.

Maybe - but I believe the engine we're talking about doesn't suffer the
torque loss above 7000 RPM, instead it keeps going.

cheers,
clive

 

[Tom Sherman]

still just me wrote:
> On Fri, 18 Jan 2008 23:56:22 -0600, Tom Sherman
> <[email protected]> wrote:
>
>>> 'course in real life, the lazy man prefers the lower grunt of a turbo...
>>>
>> Turbo lag is almost as bad as waiting for a slushbox to shift down.
>
> Another design issue. Just like cam design, you can design out most of
> the "lag" by adjusting other parameters based on intended driving
> style. Twin turbos (small/large) are another solution. And, if you put
> a turbo on an engine that already has a fair amount of power, lag will
> not show up at all.
>
> Regardless of the design though, turbo rush always make up for any
> turbo lag.
>
Suddenly having the engine come "on boost" in the middle of a corner is
NOT desirable (similar to the idiot slush box deciding to down shift
when one wants just a little more power).

--
Tom Sherman - Holstein-Friesland Bovinia
"And never forget, life ultimately makes failures of all people."
- A. Derleth

 

[Tom Sherman]

Michael Baldwin wrote:
> Jim Beam suggests
>
>> i believe that prior to this, porsche [and mercedes] played
>> about with a design that used pulleys to pull at
>> slack in the timing belt/chain that adjusted the cam timing
>> a few degrees. but that only adjusts timing and doesn't
>> offer the benefits of switching profile [lift and duration]. doubtless
>> you can check that history for yourself.
>
> I was part of the original design/process/manufacturing _team_ that
> worked on the GM/Oldsmobile engine that was to become known as the
> Quad-4. The engine's engineering designation was 4-83 (then GM "code"
> for corporate approved funding as of April of 1983)
>
> The final production version ended up with being a 2.3L inline four
> with chain driven DOHC's. We had variable cam timing, lift and duration
> prototypes that we knew would never get corporate approval ($$$)...
>
Penny wise and pound foolish at GM? Say it ain't so!

--
Tom Sherman - Holstein-Friesland Bovinia
"And never forget, life ultimately makes failures of all people."
- A. Derleth

 

[jim beam]

Michael Baldwin wrote:
> Jim Beam suggests
>
>> i believe that prior to this, porsche [and mercedes] played
>> about with a design that used pulleys to pull at
>> slack in the timing belt/chain that adjusted the cam timing
>> a few degrees. but that only adjusts timing and doesn't
>> offer the benefits of switching profile [lift and duration]. doubtless
>> you can check that history for yourself.
>
> I was part of the original design/process/manufacturing _team_ that
> worked on the GM/Oldsmobile engine that was to become known as the
> Quad-4. The engine's engineering designation was 4-83 (then GM "code"
> for corporate approved funding as of April of 1983)
>
> The final production version ended up with being a 2.3L inline four
> with chain driven DOHC's. We had variable cam timing, lift and duration
> prototypes that we knew would never get corporate approval ($$$) We
> also knew (can't say how)

[i think you just did!]

> that TOYOTA had the capability to produce such
> models as early as 1981-82.

interesting. people have been playing with this stuff for ever - it's
always been a question of whether it's worth it. with cheap gas and
cubic inches, who cares? with expensive gas, small engines and fierce
international competition, that dynamic changes.


>
> My simplistic questions of Jobst were deceitful in nature. They were
> intended to serve as a means by which to out him. I take no pride in
> such behaviour.
>

be mindful of the circumstances - since deceit is part of jobst's
playbook, it only seems fair to give him a taste of his own medicine.

 

[still just me]

On Sat, 19 Jan 2008 12:00:15 -0600, Tom Sherman
<[email protected]> wrote:

>>
>> Regardless of the design though, turbo rush always make up for any
>> turbo lag.
>>
>Suddenly having the engine come "on boost" in the middle of a corner is
>NOT desirable (similar to the idiot slush box deciding to down shift
>when one wants just a little more power).

Unless you're foolish enough to tromp the throttle in the first half
of a corner - a problem for any performance vehicle- that would never,
ever, be an issue. Turbo's don't rush in like NO2 and they certainly
don't do it if you don't tromp the throttle.

You can, of course, accelerate out of a corner and use the push of the
turbo coming on in the same way you'd use any high power engine to
throw you out of the corner (a normal "performance driving
technique"). The turbo then is also cranking for when you hit the
straight - a nice side benefit.

The only thing that requires a little learning to control is pulling
out from a stop. You need to learn to finesse to get off the line or
out in traffic quickly without then building too much boost too fast.
Mostly it just means a little extra throttle to start and then backing
off once you start to move out.

Turbo's are not for everyone. You need to have a clue. It's been my
informal observation when riding and running that 90% of drivers drive
automatic transmissions and believe that their vehicles have two
throttle positions - go and stop. They have no knowledge of how to use
a throttle (or a gearbox, or a brake, or a suspension for that matter
.

 

[Tom Sherman]

still just me wrote:
> On Sat, 19 Jan 2008 12:00:15 -0600, Tom Sherman
> <[email protected]> wrote:
>
>>> Regardless of the design though, turbo rush always make up for any
>>> turbo lag.
>>>
>> Suddenly having the engine come "on boost" in the middle of a corner is
>> NOT desirable (similar to the idiot slush box deciding to down shift
>> when one wants just a little more power).
>
> Unless you're foolish enough to tromp the throttle in the first half
> of a corner - a problem for any performance vehicle- that would never,
> ever, be an issue. Turbo's don't rush in like NO2 and they certainly
> don't do it if you don't tromp the throttle....
>
What about the times when you are steering the car with the throttle?
Linear throttle response is optimum condition.

--
Tom Sherman - Holstein-Friesland Bovinia
"And never forget, life ultimately makes failures of all people."
- A. Derleth

 

[Ben C]

On 2008-01-19, jim beam <[email protected]> wrote:
[...]
> in the mean time, here's something to look at:
> http://www.porsche.com/usa/models/911/911-carrera-s/featuresandspecs/?gtabindex=2
>
> click on "variocam". - toyota's variable valve timing married with
> honda's selectable cam profiles.
>
> i believe that prior to this, porsche [and mercedes] played about with a
> design that used pulleys to pull at slack in the timing belt/chain that
> adjusted the cam timing a few degrees. but that only adjusts timing and
> doesn't offer the benefits of switching profile [lift and duration].
> doubtless you can check that history for yourself.

The MGF had an interesting system. I think the way it worked was that
the camshaft itself rotated eccentrically (i.e. not about its own axis),
with variable eccentricity (the axis about which it did rotate could be
varied by turning a gear somehow).

 

[jim beam]

Ben C wrote:
> On 2008-01-19, jim beam <[email protected]> wrote:
> [...]
>> in the mean time, here's something to look at:
>> http://www.porsche.com/usa/models/911/911-carrera-s/featuresandspecs/?gtabindex=2
>>
>> click on "variocam". - toyota's variable valve timing married with
>> honda's selectable cam profiles.
>>
>> i believe that prior to this, porsche [and mercedes] played about with a
>> design that used pulleys to pull at slack in the timing belt/chain that
>> adjusted the cam timing a few degrees. but that only adjusts timing and
>> doesn't offer the benefits of switching profile [lift and duration].
>> doubtless you can check that history for yourself.
>
> The MGF had an interesting system. I think the way it worked was that
> the camshaft itself rotated eccentrically (i.e. not about its own axis),
> with variable eccentricity (the axis about which it did rotate could be
> varied by turning a gear somehow).

fiat had an interesting system too - the cam lobes were sloped and the
cam would be moved sideways to increase the lift against the slope.
subject to rapid wear i understand.

 

[Michael Press]

In article <[email protected]>,
Tom Sherman <[email protected]> wrote:

> [email protected] aka Jobst Brandt wrote:
> > Tom Sherman writes:
> >
> >>> ... A problem with high power engine tuning is that torque may
> >>> fall off more quickly to either side of the peak. This requires
> >>> more gears to keep the engine in its power range, power being
> >>> torque times RPM. So more gears may be an indicator that the
> >>> engine has a narrow power band rather than a desirable feature,
> >>> other things being equal.
> >
> >> That is why Otto cycle engines should have variable valve timing and
> >> lift.
> >
> > That sounds good, but you cant get there from here. Highly tuned
> > engines get higher peak performance but the eds of the power band
> > can't be made to rise equally, so the torque curve has a narrower or
> > more arched form. Variable valve timing may get rid of overlap at the
> > end of the exhaust stroke and beginning of the intake stroke, but that
> > doesn't do much good for broadening the torque curve. There isn't
> > much power there to be gained....
> >
> Better tell that to Honda Motor Company, Limited!
>
> Having driven Honda's with variable valve timing and lift for the last
> 14 years, I can verify that in real life the engines behave like a
> normal engine tuned for midrange power, at less than 5000 RPM. This
> includes excellent fuel economy for the size and weight of the car.
> However, the difference is that instead of the high end power dropping
> off, the engines pull strongly all the way to the fuel cutoff at 7000+ RPM.
>
> The engines are also quite durable. My 1994 Si never used any measurable
> amount of oil, and had excellent compression at 160,000+ miles, despite
> being driven almost abusively hard on a regular basis. Nothing was ever
> done to the engine for maintenance, beyond oil/filter changes, scheduled
> valve lash adjustments and scheduled timing belt and spark plug
> replacements.

What he says. Good solid pulling in the fuel efficient range,
and no fall-off at higher engine speed. Rather the opposite:
truly respectable acceleration all the way to the end. Put
it in third on the freeway and get going now! Sixty to eighty
need not be waiting for Godot even in a family sedan.

--
Michael Press

 

[Tom Sherman]

Michael Press wrote:
> In article <[email protected]>,
> Tom Sherman <[email protected]> wrote:
>
>> [email protected] aka Jobst Brandt wrote:
>>> Tom Sherman writes:
>>>
>>>>> ... A problem with high power engine tuning is that torque may
>>>>> fall off more quickly to either side of the peak. This requires
>>>>> more gears to keep the engine in its power range, power being
>>>>> torque times RPM. So more gears may be an indicator that the
>>>>> engine has a narrow power band rather than a desirable feature,
>>>>> other things being equal.
>>>> That is why Otto cycle engines should have variable valve timing and
>>>> lift.
>>> That sounds good, but you cant get there from here. Highly tuned
>>> engines get higher peak performance but the eds of the power band
>>> can't be made to rise equally, so the torque curve has a narrower or
>>> more arched form. Variable valve timing may get rid of overlap at the
>>> end of the exhaust stroke and beginning of the intake stroke, but that
>>> doesn't do much good for broadening the torque curve. There isn't
>>> much power there to be gained....
>> >
>> Better tell that to Honda Motor Company, Limited!
>>
>> Having driven Honda's with variable valve timing and lift for the last
>> 14 years, I can verify that in real life the engines behave like a
>> normal engine tuned for midrange power, at less than 5000 RPM. This
>> includes excellent fuel economy for the size and weight of the car.
>> However, the difference is that instead of the high end power dropping
>> off, the engines pull strongly all the way to the fuel cutoff at 7000+ RPM.
>>
>> The engines are also quite durable. My 1994 Si never used any measurable
>> amount of oil, and had excellent compression at 160,000+ miles, despite
>> being driven almost abusively hard on a regular basis. Nothing was ever
>> done to the engine for maintenance, beyond oil/filter changes, scheduled
>> valve lash adjustments and scheduled timing belt and spark plug
>> replacements.
>
> What he says. Good solid pulling in the fuel efficient range,
> and no fall-off at higher engine speed. Rather the opposite:
> truly respectable acceleration all the way to the end. Put
> it in third on the freeway and get going now! Sixty to eighty
> need not be waiting for Godot even in a family sedan.
>
I could start out at 50 mph on a two lane highway when passing a semi,
and be up to over 80 mph by the time I pulled back in. Not bad for a car
that averaged 35 mpg in real world mixed driving, and 40+ on the freeway.

--
Tom Sherman - Holstein-Friesland Bovinia
"And never forget, life ultimately makes failures of all people."
- A. Derleth

 

[jim beam]

Ben C wrote:
> On 2008-01-19, jim beam <[email protected]> wrote:
> [...]
>> in the mean time, here's something to look at:
>> http://www.porsche.com/usa/models/911/911-carrera-s/featuresandspecs/?gtabindex=2
>>
>> click on "variocam". - toyota's variable valve timing married with
>> honda's selectable cam profiles.
>>
>> i believe that prior to this, porsche [and mercedes] played about with a
>> design that used pulleys to pull at slack in the timing belt/chain that
>> adjusted the cam timing a few degrees. but that only adjusts timing and
>> doesn't offer the benefits of switching profile [lift and duration].
>> doubtless you can check that history for yourself.
>
> The MGF had an interesting system. I think the way it worked was that
> the camshaft itself rotated eccentrically (i.e. not about its own axis),
> with variable eccentricity (the axis about which it did rotate could be
> varied by turning a gear somehow).

thinking about that, i can visualize a system that would work like that,
but you'd end up with excessive valve lash. [hydraulic lifters would
follow the cam and negate the effect.]

i still think the honda system is the best yet - simplest to implement
too. the toyota system's benefits are real, but don't address lift or
duration. adding the toyota to the honda as porsche seem to have done
is the best of both worlds, but i'd have thought the benefit of changing
the cam timing in the face of being able to effect a whole different cam
profile to be minimal.