Throttle-less intake

[sstephan]

hey guys , new member here
I read this article :
http://www.f1technical.net/features/18247

in the last paragraph he says that without regulations they would not use throttle at all .
now I wonder how is that possible ?

variable valve timing is forbidden , so the only way they can do that is with ignition timing and fuel injection timing control .
one way is to delay the timing , but the cylinder will still "suck" lots of air , so more fuel must be added also (to keep "normal" a/f ratio).this will make the engine to waste lots of fuel at idle speed .

I must be missing something ?

[thisisatest]

the article implies it would be done by cutting ignition- sending no spark at all to certain cylinders. that, with some ignition timing changes, could probably cover most of the spectrum of throttle input.

[riff_raff]

hey guys , new member here
in the last paragraph he says that without regulations they would not use throttle at all .
now I wonder how is that possible ?....I must be missing something ?

All recip engines use some form of "throttling". SI gasoline engines throttle the intake airflow, and then regulate the fuel flow to ensure a suitable A/F ratio and stable combustion. There have been several production gasoline engines (such as BMWs Valvetronic) that used variable intake valve control to "throttle" the engine. Using variable intake valve control is far more efficient than using an intake manifold throttle, since the intake pumping losses are greatly reduced.

[WhiteBlue]

The 2014 turbo engines will probably be having no throttle function over much of their operating range. With the MGU-H assisted turbo you can practically control the air flow without a throttle and without variable valves. I'm not sure you can physically leave the device out but if it is incorporated it will not be used very much. To not use a throttle and incur the associated losses will be one of the ways the new engines will increase efficiency.

[Tommy Cookers]

the article implies it would be done by cutting ignition- sending no spark at all to certain cylinders. that, with some ignition timing changes, could probably cover most of the spectrum of throttle input.

modulated displacement seems to be the term for this cutting of cylinders
Cadillac used 4-6-8 running in production cars in the 80s (before anyone had VVT)
some makers use modulated displacement today
cutting the fuelling of some cylinders (not their sparks)
similarly F1 uses much 4 cylinder running for controllability/response at lower powers (in part like short shifting) and fuel saving
as the poster quoted knows because he read the (very useful) article provided by this site to us all !
in principle 1-2-3-4-5-6-7-8 running is possible, and would need little or no throttling

stratified charge engines SI engines (they do exist) need little or no throttling
the better efficiency of CI engines at partial powers is of course due to their being unthrottled

throttling attempts to reduce power (in various ways) by reducing air massflow
F1 and other race engines need little throttling for this because they have poor air massflow at lower rpm anyway
because their (fixed) extreme valve timing only fills the cylinders well at high rpm (unlike our road cars)

retarding the ignition timing would not be worthwhile just to reduce throttling
F1 retards the ignition timing for a different purpose
deliberately making the engine less efficient to get more and hotter exhaust gas while keeping the power low
because the late ignition means the combustion heat is added late in the stroke when there is little more expansion available
(heat engines function by expansion turning (some of the) combustion heat into mechanical work)
this 'hot blowing' is used (for DF benefit) even today
now limited to min 15000 rpm and min accelerator travel 80%

[Tommy Cookers]

The 2014 turbo engines will probably be having no throttle function over much of their operating range. With the MGU-H assisted turbo you can practically control the air flow without a throttle and without variable valves. I'm not sure you can physically leave the device out but if it is incorporated it will not be used very much. To not use a throttle and incur the associated losses will be one of the ways the new engines will increase efficiency.

current F1 throttling losses are low overall
because the driver almost always has the throttle well open
because the engines have naturally poor massflow over most of the rpm range, so need little throttling
(and because much partial power running is on 4 cylinders)

the 2014 engine gains mostly by reduced frictional losses from downsizing and downspeeding
and recovering a very small but worthwhile part of the waste exhaust heat

throttling losses are not primarily the pumping losses due to the flow-restrictive action called throttling
throttling also lowers in-cylinder pressure and temperature, degrading thermal efficiency and overall efficiency
SI cars are driven by using the accelerator to vary efficiency to match time-varying loads that form our driving environment
the accelerator varies efficiency from 0% to maybe 30%

[sstephan]

i still think its not very practical to run the engine without throttle . shutting down too many cylinders and the engine will be jerky , then they'll need to use larger flywheel , which is no good .
bmw valvetronic is a different story , as it has variable valve timing .

i have another question for you guys -
if throttle is not so important , why do they use butterfly valve for each cylinder ? they could use single valve (like most cars) and reduce weight / complexity .

also , is it legal in f1 to control each throttle valve separately , or all of them must be linked and sinchronised ?

[Tommy Cookers]

if throttle is not so important , why do they use butterfly valve for each cylinder ? they could use single valve (like most cars) and reduce weight / complexity .

cars with 'long' valve timing (suited to high rpm) should not share a throttle with more than 2 cylinders (even road cars)
with more the inlet valve periods overlap and the cylinders try to rob each other, and are not best filled with air

the length of the inlet tract from where it meets the combustion chamber to where it meets the airbox or the atmosphere is crucial
for maximum cylinder filling, hence maximum power, it must be an exact length for the variations in air pressure (pulses) due to the start-stop airflow of a piston engine to best fit the piston and valve motion
this required length is shorter with higher engine rpm, so far too short in F1 to allow any sharing of throttles

[seventhsin]

But if the runners are the correct length, and the plenum shaped correctly, why does it matter where the butterfly is?
At WOT the butterflies are effectivley removed from the inlet tract anyway, so what dictates their number and position?

[thisisatest]

the closer the throttle butterfly is to the cylinder, the quicker the throttle response is.

[olefud]

i still think its not very practical to run the engine without throttle . shutting down too many cylinders and the engine will be jerky , then they'll need to use larger flywheel , which is no good .

Selectively omitting a power stroke on a racing engine should work just fine. At 10,000 RPM there are about 14 power pulses per second per cylinder, or one every .07 second. This would afford power modulation resolution of .0002 with improved response time over an analog throttle valve. Throw in boost modulation for vernier trim and it should be very crisp.

The roughness issue is somewhat illusory. Competition idle can be controlled by cutting a great percent of power pulses with substantial RPM while being only a bit rough since the engine load is low. And at high load cylinder duty cycle would be high.

[riff_raff]

All SI recip engines require some form of intake air throttling, whether the function is performed by variable intake valve control or by an intake manifold butterfly. SI Otto cycle engines require fairly close control of F/A ratio. And the only way to match engine output to load is by metering intake mass airflow. SI engines always achieve best efficiency at WOT conditions. Deactivating cylinders at part load conditions keeps engine efficiency high by allowing the remaining cylinders to operate at WOT. Deactivating cylinders eliminates much of their pumping losses, but it does not eliminate all of their mechanical friction losses.

[Tommy Cookers]

All SI recip engines require some form of intake air throttling, whether the function is performed by variable intake valve control or by an intake manifold butterfly.
Deactivating cylinders eliminates much of their pumping losses, but it does not eliminate all of their mechanical friction losses.

I'm not disagreeing with anything in the post ...... but ......
stratified charge SI engines, broadly speaking, do not have intake throttling (a little might help them ?)
early IC engines were mostly, broadly speaking, stratified charge SI engines
eg those fuelled on gas (not gasoline)
others ran on oil, both had pre spark-era externally energised 'hot spot' ignition

as did early gasoline engines (they were nominally homogeneous charge)
carburation (and throttling) as we know them did not really exist then
the fuel was a lighter fraction than ours, with a wider range of combustability, so precise a:f ratio was unimportant
and engines had less need for partial power operation other than idle (not having much max power anyway)
and were set and governed to run at intermediate power, the accelerator not being a throttle, but a pedal override of the governer

the introduction of (timed) SI was hugely valuable to control power by driver control of ignition timing
until and after proper carburation (and associated throttling) became available
cars had manual (driver) controlled ign timing till near WW2 ?
some (British) motorcycles had this even in 1960s

so it's amusing to see ignition retardation being reinvented in 21st century F1


an F1 engine needs less throttling (to reduce massflow and thermal efficiency) for partial powers than does a normal engine
because its truly extreme valve timing anyway gives poor massflow and TE (at lower rpm the inlet flow is in part reversed)

regarding throttle plate position in F1
surely we must fuel at the throttling point ? (for good dispersion/droplet size at the lower velocities/turbulence)
we wouldn't/couldn't have throttling at the duct mouth (behind the drivers head)
because we'd need a flame trap to prevent explosion, and the cylinders a:f ratios would vary
an airbox induction system when limited in size and/or shape has non-ideal impacts on engine power curve
as Dr Blair's work for Moto GP (predicting these and their treatment with variously phased firing via crankshaft design)

having neither '3-way' catalysts or VVT, F1 is easily and happily deactivating cylinders and benefitting in efficiency
such benefit is in principle available (without needing VVT) in road cars, cold cylinder wear avoidable by dispersed deactivation
there's not much point in having 3 way cats on the road ? especially when (as in Europe) 55% of road vehicle use is Diesel
(3 way cats also prevent us using a lean mixture, the first and easiest way of reducing pumping and efficiency loss from throttling)

EDIT I posted 2 way cats but meant 3 way cats, honest !
the point being that a 2 way allows a lean mixture
(if cylinders are deactivated by zero fuelling and valves continue working the exhaust would have oxygen, useless for 3 way catalysis)

[olefud]

All SI recip engines require some form of intake air throttling, whether the function is performed by variable intake valve control or by an intake manifold butterfly. SI Otto cycle engines require fairly close control of F/A ratio. And the only way to match engine output to load is by metering intake mass airflow. SI engines always achieve best efficiency at WOT conditions.

There are at least two ways to modulate power on an SI engine at WoT. As has been discussed, cutting fuel and spark to select, preferable differing, cylinders is nicely workable. A second scheme involves the classic power/RPM plot that can be exploited to control power at WoT primarily by regulating RPM, as by, for example, a CVT controlled by the accelerator pedal. Varying boost is yet another more limited means. Since these are essentially independent they can be used in conjunction.

In a race engine with an “idle” speed of 4000 or higher RPM, constant WoT operation is readily obtained. I agree that a less bawdy street engine would benefit from throttling at lower power requirements, though it too could with proper engineering realize a fairly high duty cycle at WoT.

[langwadt]

All SI recip engines require some form of intake air throttling, whether the function is performed by variable intake valve control or by an intake manifold butterfly.
Deactivating cylinders eliminates much of their pumping losses, but it does not eliminate all of their mechanical friction losses.

I'm not disagreeing with anything in the post ...... but ......
stratified charge SI engines, broadly speaking, do not have intake throttling (a little might help them ?)
early IC engines were mostly, broadly speaking, stratified charge SI engines
eg those fuelled on gas (not gasoline)
others ran on oil, both had pre spark-era externally energised 'hot spot' ignition

as did early gasoline engines (they were nominally homogeneous charge)
carburation (and throttling) as we know them did not really exist then
the fuel was a lighter fraction than ours, with a wider range of combustability, so precise a:f ratio was unimportant
and engines had less need for partial power operation other than idle (not having much max power anyway)
and were set and governed to run at intermediate power, the accelerator not being a throttle, but a pedal override of the governer

the introduction of (timed) SI was hugely valuable to control power by driver control of ignition timing
until and after proper carburation (and associated throttling) became available
cars had manual (driver) controlled ign timing till near WW2 ?
some (British) motorcycles had this even in 1960s

so it's amusing to see ignition retardation being reinvented in 21st century F1


an F1 engine needs less throttling (to reduce massflow and thermal efficiency) for partial powers than does a normal engine
because its truly extreme valve timing anyway gives poor massflow and TE (at lower rpm the inlet flow is in part reversed)

regarding throttle plate position in F1
surely we must fuel at the throttling point ? (for good dispersion/droplet size at the lower velocities/turbulence)
we wouldn't/couldn't have throttling at the duct mouth (behind the drivers head)
IIRC the duct has for 30 years been open bottomed
even if sealed we wouldn't want to fuel there, because we'd need a flame trap to prevent explosion
and the cylinders a:f ratios would vary
an airbox induction system when limited in size and/or shape has non-ideal impacts on engine power curve
as Dr Blair's work for Moto GP (predicting these and their treatment with variously phased firing via crankshaft design)

having neither '2-way' catalysts or VVT, F1 is easily and happily deactivating cylinders and benefitting in efficiency
such benefit is in principle available (without needing VVT) in road cars, cold cylinder wear avoidable by dispersed deactivation
there's not much point in having 2 way cats on the road ? especially when (as in Europe) 55% of road vehicle use is Diesel
(2 way cats also prevent us using a lean mixture, the first and easiest way of reducing pumping and efficiency loss from throttling)

you almost certainly need a three way cat to pass regulation, for a petrol engine you need toggle between lean and rich
in a very specific way to make it work, oxidizing HC and CO and reducing NOx

modern diesels use throttling together with egr so there is less oxygen in the exhaust limiting the production of NOx