[Diy_efi] RE: Throttling intake air -- references

[Grant Beaty]

> Hang on if its surging through normal driving, isnt that a bad
> match. For normal road use why would you have wild throttle changes,
> and even if you do the turbo is not going to be damaged.

Thats not reall normal driving, thats trying to modulate low boost at high
RPMs. On a road course I'd probably be unwinding the steering wheel and
giving it more throttle by then. I matched my turbo for 15 to 28 psi.

> I dont seem to have any problem or surge noise when I use my foot
> to back off smoothly from say 5psi to 2psi, it dosnt change the throttle
> opening by much and I dont get any surge noise as far as I can tell.

You can't always hear it - sometimes you need to look for a flutter in the
boost gauge. Not that your probably getting surge.

> In any case, the turbo is well able to handle people deaccelerating
> all the time isnt it, we do it daily so whats the problem  ?

I agree, should be perfectly drivable.

> Who says you need low throttle positions to maintain 10psi boost,

I do!!! VERY low. Then again, my turbo isn't exactly sized for low-end
power, its sized to make power from 4800-6800 at 15-28 psi.

> I am *not* suggesting any sort of wild throttle fluctations
> in any similar format to existing 'flutter' type wastegate controllers
> where the wastegate is modulated on/off fashion with varying frequency
> depending on engine rpm/load situations... <geesh>

What exactly is flutter type controllers? You mean a solenoid of varying
duty cycle? In that case, I believe the solenoid's behavior simple varies
pressure to the WG, the WG itself doesn't "flutter". If it did, you'd be
able to hear it (the ones vented to the atmo).

Grant Beaty

> What I am trying to get across is an extension of the human foot
> pedal control approach, as the boost rises, the rate of throttle
> opening increase diminishes until max boost is reached and not
> allowed to go further but if it does then the throttle is backed
> off in a smooth control systems type paradigm - *not* at all
> by any flutter or wild on/off type movement.
>
> Is that possibly the reason that I am getting some flak for
> even suggesting this, people think I am talking flutter control ?
>
> Are there so many wastegate controllers that are just dumb basic
> bang-bang flutter type controllers and are not PID (proportional)
> that misleads the paradigm I am trying to get across ?
>
> <sigh>
>
> rgds
>
> mike
>
>
>
>
>
> >And this is with a wastegate, I can hear it open modulating the throttle
as
> >low as 8ish psi. Without the WG the pressure ratio would be even greater.
> >
> >Grant
> >
> >----- Original Message -----
> >From: "Mike" <erazmus at iinet.net.au>
> >To: "List for general do-it-yourself EFI talk" <diy_efi at diy-efi.org>
> >Sent: Thursday, January 16, 2003 5:30 PM
> >Subject: Re: [Diy_efi] RE: Throttling intake air -- references
> >
> >
> >> The thing is Grant, when you are driving, you use your foot and
> >> the throttle plate to regulate power output - hence regulates
> >> boost - without the seeming problems people say will happen.
> >>
> >> or am I missing something from that personal experience ?
> >>
> >> rgds
> >>
> >> mike
> >>
> >>
> >> At 02:17 PM 15/1/2003 -0500, you wrote:
> >> >Great idea and all, but unless you work for a OEM making an ECU for a
> >turbo
> >> >car, why bother? External wastegates control boost just fine, my car
can
> >run
> >> >from 8 psi to over 35.
> >> >
> >> >However the extremely small throttle opening required to hold low
boost
> >must
> >> >produce a lot of pressure in the IC pipes. When I first put my turbo
kit
> >> >together I didn't have a dump tube for the WG so I left the boost
> >controller
> >> >off and tried simulating WOT conditions by modulating the throttle,
and I
> >> >noticed I barely had to give it any gas at all; it was actually kind
of
> >> >difficult. Autocrossing a car that spins through first and second
> >requires
> >> >quite a bit of throttle modulation, so I'm used to it.
> >> >
> >> >My WG is currently set to open at 17-18 psi. My boost gauge is plumed
> >into
> >> >the intake manifold, and if I modulate throttle, it opens at around 7
> >psi,
> >> >so thats a 10 psi drop across the throttle plate. On some turbos, that
> >surge
> >> >teritory, and it does surge a bit on mine. If I had electronicly
> >controlled
> >> >everything, I'd modulate the WG more than the throttle to keep it off
> >surge.
> >> >
> >> >Even if there are benifits, just doesn't seem worth the effort.
> >> >
> >> >Grant Beaty
> >> >
> >> >----- Original Message -----
> >> >From: "Mike" <erazmus at iinet.net.au>
> >> >To: "List for general do-it-yourself EFI talk" <diy_efi at diy-efi.org>
> >> >Sent: Thursday, January 16, 2003 1:23 AM
> >> >Subject: RE: [Diy_efi] RE: Throttling intake air -- references
> >> >
> >> >
> >> >> At 10:04 AM 15/1/2003 -0600, you wrote:
> >> >> >> Brian,
> >> >> >>
> >> >> >> You are missing the point totally !
> >> >> >
> >> >> >Well, perhaps, but you have not provided me with any references to
> >> >support
> >> >> >your claim.
> >> >>
> >> >> Brian, I am not making a practical claim from heaps of academic
> >> >> reference which you seem to be fixated upon to quantify a judgement
> >> >> as to whether you entertain an idea. Its basic control systems
> >> >> theory. I dont have my text books from 1980-81 to hand but I can
> >> >> tell you its considered far more sensible to control fuel
> >> >> before its combusted than after its done its thing. Look at
> >> >> rocket engines, jet turbines, they all do what I suggest as do all
> >> >> the people that drive turbo cars that use their foot for reducing
> >> >> boost - some time before the lossy wastegate needs to be vented,
> >> >> its implicit and taken for granted when we dont drive to maximum
> >> >> therefore some time *before* the wastegate needs to be vented.
> >> >>
> >> >> >Again, our regimes are completely different.  I am looking at
steady
> >> >state,
> >> >> >with efficiency as the bottom line I could care less if it took the
> >turbo
> >> >30
> >> >> >seconds to spool up.
> >> >>
> >> >> Well dont look at steay state, because thats not relevant or
> >appropriate
> >> >> is it.
> >> >>
> >> >> When you drive and watch boost pressure long before you get to the
> >point
> >> >> of high enough boost warranting the wastegate opening you can easily
> >> >> and seamlessly throttle back and reduce boost - we all do it, so
that
> >> >> steady state aspect of your para above is already handled implicitly
> >> >> by experience isnt it. I am talking an ECU that handles the
transient
> >> >> to bring it back via throttling the inlet - effectively the same as
> >> >> if you were watching the boost gauge and wanted to back off before
it
> >> >> went over some magic figure. The issue of spool up is nothing I
> >> >> ever suggested, discussed or dismissed, you are adding this and I
dont
> >> >> know why you are adding complexity to a simple issue, which might
> >> >> be relevant admittedly if we were ever in an apples vs apples
> >> >> comparison which we have not yet reached ;)
> >> >>
> >> >> >> We are not talking steady state, we are talking about a control
> >> >> >> dynamic - what you tangentially refer to will happen admittedly
but,
> >> >> >> only in transient for a very shor period of time, then back to
> >> >> >> a stready state which is identical to what you do when you drive
> >> >> >> normally - which is control the pedal by foot pressure for power
> >> >> >> output.
> >> >> >
> >> >> >Not according to the reference I provided you.
> >> >>
> >> >> Are you saying your reference is more authoritative than observing
> >> >> your own pedal pressure to back off boost, I cant see direct
> >> >> evidence for either at this point in time ?
> >> >>
> >> >> >> When I have my engine on a dyno and I select a throttle level
> >> >> >> by foot pressure for say 9 pounds boost (some 1.5 pounds before
> >> >> >> the wastegate {relief} opens at 10.5 pounds boost), I can easily
> >> >> >> throttle the pedal back a little and reduce boost and repeat
> >> >> >> this indefinitely without any problem whatsoever, we do this
> >> >> >> *all* the time when we drive.
> >> >> >
> >> >> >I believe you.  Since your engine is on a dyno, do you have a BSFC
for
> >> >this
> >> >> >specific test?
> >> >>
> >> >> No, I dont do a BSFC on the few minutes of dyno run, but think about
> >> >> it sensibly, when the wastegate opens you are dumping energy - its
> >> >> being wasted - hence the name -"WASTE-GATE",  doh !
> >> >>
> >> >> > I'll bet it's way low.  Also, what is your EGT pre-turbo,
> >> >> >and EBP?
> >> >>
> >> >> As mentioned on several previous occasions which havent sunk in yet,
> >> >> "... from a control systems perspective..." Ok, then think about it,
> >> >> the turbine turns heat into useful work so if the exhaust is not
> >> >> byapssed than useful work is done by all the exhaust, so therefore
> >> >> once exhaust is bypassed it much raise the EGT of the exhaust post
> >> >> turbine - basic logic as its going around the turbine !
> >> >>
> >> >> >From another view, measure EGT before and after a turbine, its
> >> >> higher before, so if you vent it to after the turbine you *must*
> >> >> be raising the EGT after the turbine - basic logic.
> >> >>
> >> >> >> We do that as a matter of course when driving - and it works.
> >> >> >
> >> >> >Are all (or the majority) turbocharged cars on the road set with
the
> >> >> >wastegate completely closed?  If so, please, please give me just on
> >> >example
> >> >> >that's a daily driver so I can check it out for myself.  I'm not
> >> >interested
> >> >> >in F1 cars, or any racing example, as the requirements are
> >performance,
> >> >not
> >> >> >efficiency.
> >> >>
> >> >> No - of course not, but we are not bang-bang drivers are we, dont
you
> >> >> ever watch your boost gauge go to say 9 pounds and back off the
> >throttle
> >> >> and watch it reduce, we dont *need* to go max out for a wastegate
> >relief
> >> >> for an understanding we can back off before that point by virture of
> >> >> throttle pressure applied by discrimination through foot pressure...
> >> >>
> >> >> Ask yourself, is it more efficient to dump exhaust via wastegate or
> >> >> have the turbo use this energy albiet at lower overall flow rate by
> >> >> virtue of the dynamic of inlet throttling... ?
> >> >>
> >> >> >> All I suggest is to flick off the wastegate - get better laminar
> >> >> >> flow from the improved exhaust geometry post turbo and let an
> >> >> >> ECU make the decision to assist me by backing off the throttle
> >> >> >> as it gets to the maximum boost selected in such a way that I
> >> >> >> cant over-ride it and damage the engine.
> >> >> >
> >> >> >Why can't the wastegate have it's own exhaust pipe?  Some airplanes
> >do.
> >> >> >Mine does.  Great laminar flow, but I'm not sure how much that buys
> >you
> >> >in
> >> >> >reduced EBP.
> >> >>
> >> >> Sure we can have its own pipe, I am not arguing against this, I am
> >simply
> >> >> saying, in relevance to cast wastegates in turbo bodies, that there
> >might
> >> >> be an alternative and from a control systems perspectives it makes
more
> >> >> sense to control the input rather than the output to control power.
> >> >> Adding an external wastegate costs more which makes one wonder if
> >> >> its better to avoid stuffing around with venting high temp. exhaust
> >> >> when we can control low pressure air and fuel far more easily !
> >> >>
> >> >> >> That is how turbines from Pratt and Whitney and Rolls Royce do
> >> >> >> it, I never knew Cessna made jet turbines - I cant imagine
> >> >> >> a wastegate biug enough - but you have to ask - why do cessna
> >> >> >> do it when Pratt and Whitney, Rolls Royce and GE dont !
> >> >> >
> >> >> >I'm not talking about turbine engines, turbocharged piston engine.
> >Oh,
> >> >by
> >> >> >the way, Cessna DOES have a line of jet aircraft.  Ever heard of
the
> >> >> >Citation series?  I think they use P&W engines.
> >> >>
> >> >> Hang on ! YOU are the one that launched into aero issues, are you
> >> >> saying Pratt and Whitney and Rolls and GE use wastegates, surely
they
> >> >> dont.  In an earlier email you alluded to the point Cessna used
> >> >> wastegates on their turbines, now you are saying they use P&W
turbines,
> >> >> which jet turbines use wastegates then...
> >> >>
> >> >> And dont you think that if P&W, Rolls, GE dont use wastegates then
> >> >> it might make sense why they have gone that route ?
> >> >>
> >> >> >> Your response to this idea seem woefully dogmatic and you are
> >> >> >> going to some lengths to seem to talk me out of it as if its
> >> >> >> a real bad idea (and I will answer your earlier posts when I
> >> >> >
> >> >> >I'm not saying it's a bad idea, I'm just saying your BSFC will
suffer
> >if
> >> >you
> >> >> >control boost pre-compressor rather than with wastegate.  My books
> >back
> >> >that
> >> >> >up.  I do agree that this would keep turbo lag to a minimum.
> >> >>
> >> >> No, your books dont back it up, they are tangential and predicated
> >> >> on prior art where wastegate turbos were the rage and prior to
> >> >> existing control systems methods - they are therefore possibly out
> >> >> of date. I've never mentioned turbo lag though it might be a
benefit.
> >> >>
> >> >> >> The '...control systems perspective...' re a reference, well this
> >> >> >> is implicit in control systems theory which I studied at the
> >> >> >> local uni, I dont have an explicit reference without you entering
> >> >> >
> >> >> >Which degree do you have?  Which university?
> >> >>
> >> >> Oh really, in to comparing the sizes of our dicks now are we <sigh>
> >> >> think back a few steps so this is not necessary...
> >> >>
> >> >> WAIT = Western Australian Institute of Technology, did my Bachelor
> >> >> of Engineering back in 1982, and my thesis was fuel injection
control
> >> >> with feed forward transmission control. Studied there for 7 years,
> >> >> during which I did electives in AI, psychology, business methods,
> >> >> applied diploma in statistics, effective double major, taught 2nd
> >> >> year bachelor of information processing students for 5 years whilst
> >> >> a student from 1978 to 1982, worked in process control industries,
> >> >> blah blah - not relevant.
> >> >>
> >> >> >I am an instrumentation engineer as well, with a bachelors of
Science
> >in
> >> >> >Computer Science.
> >> >>
> >> >> Then it should be abundantly clear to you its not as efficient to
> >> >> dump power already generated than control its input in the first
place.
> >> >>
> >> >> >I agree that controlling something with a 20milliamp current loop
is
> >> >> >superior to a hydraulic amplified servo, but we're talking about
very
> >> >> >similar forces on the throttle bellcrank, and the wastegate
bellcrank.
> >> >>
> >> >> no. Thats why I made particular mention of fly by wire as part of
> >> >> a control strategy.
> >> >>
> >> >> >Go ahead, call me on the carpet again.  I kept all my books from
> >college
> >> >> >from PID design, circuit design and control theory.  Only in the
last
> >few
> >> >> >years have I purchased my current raft of books on engines from
> >Heywood,
> >> >> >Bell, Macinnes, and just last week, bought another ... it was
> >referenced
> >> >> >here, I was reading it last night before it put me to sleep.  The
> >title
> >> >is
> >> >> >something along the lines of "Tuning Forced Induction Systems".
> >> >>
> >> >> Well sure, but dont assume that *everything* is in books, and if it
> >> >> aint broke dont fix it ;), I am suggesting that:- given advances in
> >> >> processors and control electronics/servos, it might be worthwhile
> >> >> looking at the issue of pre-turbo boost control from a "...control
> >> >> systems perspective..." - surely with the same discipline and
> >> >> training you must appreciate that, and not be led into commercial
> >> >> mass market propoganda forcing you to agrandise an issue as if
> >> >> its necessarily the 'right' one because its based on false logic
> >> >> in terms of control systems theory - the difference admittedly is
> >> >> not huge but *I* am interesting in "the path less travelled"...
> >> >>
> >> >> >> to engine power - thats it, therefore classic control systems
> >> >> >> theory has a great amount to say in terms of application and
> >> >> >> the reason its not generally done is predominatly for cost
issues,
> >> >> >
> >> >> >Hmmm, I doubt that.  Politics has a lot to do with that.  The EPA
> >keeps
> >> >the
> >> >> >MPG bar over the heads of the auto manufacturers.  It's not cost
> >alone.
> >> >>
> >> >> Sure, and this raises in an interesing point... The longer higher
> >> >> EGT occurs the more potential for NOx production, and is more likely
> >> >> to happen with a wastegate, when you dont dump power that way then
> >> >> you can throttle back even more and reduce integral of overall
> >> >> EGT over time for a particular drive cycle. You dont need book
> >> >> references to exercise grey matter and make extrapolations...
> >> >>
> >> >> >> ICE has not even been looked at seriously as a control system
> >> >> >> problem. The people at Pratt and Whitney, Rolls Royce are rather
> >> >> >> more sophisticated and do see their turbines in that light :)
> >> >> >
> >> >> >For aircraft ICE, that's certainly the case.  The auto guys are
light
> >> >years
> >> >> >ahead in technology compared to aviation.  It's why I'm here
soaking
> >up
> >> >> >knowledge on this group.  The turbine/jet guys are completely
> >sensitive
> >> >to
> >> >> >their fixed costs(fuel).  1% here and there adds up to major bucks
> >saved
> >> >on
> >> >> >a single flight.  I spoke to an aero engineer who was EIT to a
Boeng
> >> >> >engineer.  They came up with a vortex generator on the B737 that
> >> >increased
> >> >> >efficiency some fraction of a percent.  Management was happy, they
got
> >a
> >> >big
> >> >> >bonus.
> >> >>
> >> >> Well yes, so the impetus to throttle the input of jet turbines
> >> >> instead of using wastegates must have an efficiency imperative but,
> >> >> I disagreee, aviation guys at Rolls Royce where I last visited in
> >> >> Bristol UK, are somewhat far ahead of automotives in respect of
> >> >> turbine engine developments. Rolls Royce for example, has modelled
> >> >> the whole triple shaft geared turbine through control systems
> >> >> modelling and not one wastegate in site !
> >> >>
> >> >> >I think we are arguing the same thing with respect to turbos, but
> >> >different
> >> >> >regimes.  I still don't agree with your control implementation
theory
> >> >> >though.  Doesn't mean we need to get into a fest over it though.
> >> >>
> >> >> Hey, I dont mind a robust debate and,
> >> >>
> >> >> No, I see two things with your retorts:-
> >> >>
> >> >> a. You are bound by tradition to some degree, if a thousand people
do
> >> >> it then it must be right mentality, and considering an alternative
> >> >> goes a little against the grain so you argue against it 'knee
> >> >> jerk' fashion.
> >> >>
> >> >> b. The dichotomy between steady state and transient in a control
> >> >> systems dynamic *before* the wastegate needs to be opened is
> >> >> something you are fixated *only* as if its steady state which
> >> >> it isnt.
> >> >> In this respect, watch your boost gauge when you drive up say
> >> >> a steep hill and back off the throttle, what I am suggesting
> >> >> is in most respects the same thing.
> >> >>
> >> >> I'm off to bed now, its 1am here and I have heaps of work to finish
> >> >> before holidays, plus I'm going to watch the stars eating glaced
> >ginger,
> >> >> dried paw-paw and a white wine before bed :-)
> >> >>
> >> >> rgds
> >> >>
> >> >> Mike
> >> >>
> >> >> _______________________________________________
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> >> >
> >> >
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> >>
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