General Car Related Discussion. To discuss anything that is related to cars and automotive technology that doesnt naturally fit into another forum catagory.

Is 'TFC important?

Thread Tools
 
Search this Thread
 
Old 21-05-2007, 05:27 PM
  #1  
Billabong
PassionFord Post Whore!!

Thread Starter
 
Billabong's Avatar
 
Join Date: May 2003
Location: Northants
Posts: 9,076
Likes: 0
Received 0 Likes on 0 Posts
Default Is 'TFC important?























<Southern drawl>
'tucky Fried Chicken??
</Southern drawl>

Old 21-05-2007, 05:41 PM
  #2  
Stu @ M Developments
PassionFords Creator



iTrader: (12)
 
Stu @ M Developments's Avatar
 
Join Date: May 2003
Location: Blackpool, UK Destination: Rev limiter
Posts: 28,824
Received 95 Likes on 76 Posts
Default

Old 21-05-2007, 05:41 PM
  #3  
ECU Monitor Enthusiast
BANNED
BANNED
iTrader: (1)
 
ECU Monitor Enthusiast's Avatar
 
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes on 0 Posts
Default

Sorry Bill, dont get it, I must be dim
Old 21-05-2007, 05:45 PM
  #4  
L33 BYT
PassionFord Post Whore!!

 
L33 BYT's Avatar
 
Join Date: Jul 2003
Location: SUFFOLK
Posts: 7,482
Likes: 0
Received 0 Likes on 0 Posts
Default

I'm with you on that Simon!
Old 21-05-2007, 05:59 PM
  #5  
ECU Monitor Enthusiast
BANNED
BANNED
iTrader: (1)
 
ECU Monitor Enthusiast's Avatar
 
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes on 0 Posts
Default

Now I get it.

Classic

Old 21-05-2007, 06:23 PM
  #6  
Stu @ M Developments
PassionFords Creator



iTrader: (12)
 
Stu @ M Developments's Avatar
 
Join Date: May 2003
Location: Blackpool, UK Destination: Rev limiter
Posts: 28,824
Received 95 Likes on 76 Posts
Default

(TFC) Transient fuel correction is very important indeed, infact, its algorythms can make or break an entire management system, or even, on a smaller scale, just a mapping session...

KFC however, is even more important tonight, or at least to me it is. LOL
Old 21-05-2007, 06:30 PM
  #7  
Anonymous
Banned
 
Anonymous's Avatar
 
Join Date: Dec 2002
Posts: 142
Likes: 0
Received 1 Like on 1 Post
Default

Ok
Old 21-05-2007, 06:35 PM
  #8  
Thrush
Irritating c........

iTrader: (1)
 
Thrush's Avatar
 
Join Date: May 2003
Location: The Dark Side of the Moon...
Posts: 21,265
Received 147 Likes on 126 Posts
Default

Coooooooooont! Do you know how ficken hungry I am?
Old 21-05-2007, 06:42 PM
  #9  
ECU Monitor Enthusiast
BANNED
BANNED
iTrader: (1)
 
ECU Monitor Enthusiast's Avatar
 
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes on 0 Posts
Default

Stu,

You are quite right. That was one of the last issues I fixed on my own ecu
design and probally the hardest thing to get right in the whole grand plan.

In the start, I has some software to detect a sudden rate of change in the
TPS position which added and amount of extra fuel based on percentage of map.
Then over a short time, it decayed the extra fuel back to zero.

The problem wasnt that algorithm, it was actually two things....

The first was that by the time the extra fuel was injected on the next
injector cycle, the extra air was actually in the cylinder so the extra fuel
made little difference as it was injected at the next point without
adjustment of the start point of injection.

The second, a turbo can increase the air load without movement of the
throttle so the extra air was getting in the cylinder without extra fuel.
(After the initial movement to stir things up)

The solution was to check for changes in map pressure as well as throttle
position then advance the point (make it happen sooner) that the injector
starts to squirt fuel in.

The actual software modifications were less than 20 lines of C code but
it took me 2 years to pin point and fix.

All these things happen very quickly even at low RPM's and are
exagerated with larger injectors/cams/port sizes etc.


THIS ISNT A FOR SALE POST
Old 21-05-2007, 06:58 PM
  #10  
fuzzy
14000+ post superhero
 
fuzzy's Avatar
 
Join Date: Oct 2005
Location: upside down in a field
Posts: 17,459
Received 490 Likes on 383 Posts
Default

Originally Posted by LS35A
Sorry Bill, dont get it, I must be dim
neither do i. must be an 'in' joke
Old 21-05-2007, 06:59 PM
  #11  
GARETH T
Professional Waffler
 
GARETH T's Avatar
 
Join Date: May 2003
Location: barry-south wales
Posts: 30,980
Received 9 Likes on 6 Posts
Default

intresting simon,,,

PMSL at bill
Old 21-05-2007, 07:01 PM
  #12  
GARETH T
Professional Waffler
 
GARETH T's Avatar
 
Join Date: May 2003
Location: barry-south wales
Posts: 30,980
Received 9 Likes on 6 Posts
Default

Originally Posted by fuzzy
Originally Posted by LS35A
Sorry Bill, dont get it, I must be dim
neither do i. must be an 'in' joke
someone (ima? ) made a point about transient fuel correction and he was wrong in his understanding!
Old 21-05-2007, 07:03 PM
  #13  
DanRSturbo
10K+ Poster!!
 
DanRSturbo's Avatar
 
Join Date: May 2003
Location: Handcuffed to the Mrs' Bed ;-)
Posts: 10,089
Likes: 0
Received 2 Likes on 1 Post
Default

Damn right, a "tucky fried chicken" is a must at least once a month I feel

Or is it "Turkey Fighting Champion" ??
Old 21-05-2007, 07:07 PM
  #14  
Billabong
PassionFord Post Whore!!

Thread Starter
 
Billabong's Avatar
 
Join Date: May 2003
Location: Northants
Posts: 9,076
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by fuzzy
Originally Posted by LS35A
Sorry Bill, dont get it, I must be dim
neither do i. must be an 'in' joke
Not at all, just light hearted humour (NO malice intended). Probably only makes sense if you've been keeping up to date with posts in GD....
Old 21-05-2007, 07:09 PM
  #15  
fuzzy
14000+ post superhero
 
fuzzy's Avatar
 
Join Date: Oct 2005
Location: upside down in a field
Posts: 17,459
Received 490 Likes on 383 Posts
Default

Originally Posted by Billabong
Originally Posted by fuzzy
Originally Posted by LS35A
Sorry Bill, dont get it, I must be dim
neither do i. must be an 'in' joke
Not at all, just light hearted humour (NO malice intended). Probably only makes sense if you've been keeping up to date with posts in GD....
oh i see. i havent so still dont understand
Old 21-05-2007, 08:11 PM
  #16  
Stu @ M Developments
PassionFords Creator



iTrader: (12)
 
Stu @ M Developments's Avatar
 
Join Date: May 2003
Location: Blackpool, UK Destination: Rev limiter
Posts: 28,824
Received 95 Likes on 76 Posts
Default

Who wants to explain "Tau"
Old 21-05-2007, 08:18 PM
  #17  
vx220
Too many posts.. I need a life!!
 
vx220's Avatar
 
Join Date: Aug 2004
Location: THE ESSEX
Posts: 733
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by fuzzy
Originally Posted by LS35A
Sorry Bill, dont get it, I must be dim
neither do i. must be an 'in' joke
a chick-in joke, perhaps
Old 21-05-2007, 08:23 PM
  #18  
ECU Monitor Enthusiast
BANNED
BANNED
iTrader: (1)
 
ECU Monitor Enthusiast's Avatar
 
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Stu @ M Developments
Who wants to explain "Tau"
Stu, are you referring to basic injection calculation with temperature cooefficient correction ?

OR

The effect of transient correction based on the rate of change of engine speed. ?

I seem to remember both types refer to the acronym Tau and TauB
Old 21-05-2007, 08:44 PM
  #19  
Mr-Ford
Wahay!! I've lost my Virginity!!
 
Mr-Ford's Avatar
 
Join Date: May 2007
Posts: 86
Likes: 0
Received 0 Likes on 0 Posts
Default

all i was saying was if you dont know about tfc then you wont know how to idle a car on greys at mot standard.

i am not here to teach mapping.
Old 21-05-2007, 08:47 PM
  #20  
ECU Monitor Enthusiast
BANNED
BANNED
iTrader: (1)
 
ECU Monitor Enthusiast's Avatar
 
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Mr-Ford
all i was saying was if you dont know about tfc then you wont know how to idle a car on greys at mot standard.

i am not here to teach mapping.
Phil,

TFC has nothing at all to do with idle no matter what injectors you have.
Old 21-05-2007, 08:59 PM
  #21  
Mr-Ford
Wahay!! I've lost my Virginity!!
 
Mr-Ford's Avatar
 
Join Date: May 2007
Posts: 86
Likes: 0
Received 0 Likes on 0 Posts
Default

so you are saying LS35A that you can get a car to pass the mot on greys if you have no idea about tfc?I would say knowing how to map in every area is paramount to being a credible mapper?
Old 21-05-2007, 09:05 PM
  #22  
ECU Monitor Enthusiast
BANNED
BANNED
iTrader: (1)
 
ECU Monitor Enthusiast's Avatar
 
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Mr-Ford
so you are saying LS35A that you can get a car to pass the mot on greys if you have no idea about tfc?I would say knowing how to map in every area is paramount to being a credible mapper?


I say again, Transient Fuel Correction has nothing to do with Idle.

Whats transient about Idle then ??? NOTHING

As for MOT on greys, it is possible depending on the whole package
and I dont mean just the mapping and of course the type of MOT test too.

Attention to detail and closed loop help a lot.

And not a TFC or KFC in sight.
Old 21-05-2007, 09:17 PM
  #23  
Rick
15K+ Super Poster!!

 
Rick's Avatar
 
Join Date: May 2003
Location: Stockport, Cheshire
Posts: 15,885
Received 17 Likes on 17 Posts
Default

Direct quotes from my 1st class hons thesis on Engine Management:

Two major factors influence acceleration enrichment; wall wetting and air charging. The concept of wall-wetting is simple: for every injection event, the majority of fuel enters into the cylinder, but some of the fuel collects on the wall of the intake tract. In simplistic terms, a certain percentage of fuel (defined as (1-X)) reaches the cylinder, the remainder sticks to the walls (X), hence the term 'wall wetting'. The fuel that sticks to the walls eventually evaporates back into the air stream and is drawn into the cylinder. This is a time variable, Tau, which is the amount of time it takes to get the fuel clinging to the wall back into the cylinder. (Aquino, 1990)
This is true in all engine operating conditions, not just under acceleration. However, under steady state conditions, this does not present a problem. Fuel condenses and evaporates at the same rate so equilibrium is reached. During a throttle transition more fuel is required outside of this equilibrium due to the increase in air flow per unit time. If a percentage of the fuel clings to the wall, then more fuel needs to be added i.e. and increase in pulse width to compensate. The fuel evaporating which usually maintains equilibrium is from an injection event prior to acceleration, which is not enough. At the end of the acceleration event i.e. when the engine is at steady state, the reverse is true. The fuel which is now evaporating is from an acceleration event – too much fuel will be delivered to the combustion chamber.
Hence this method of compensation is known as "X-Tau" compensation, where you specify:
X, the amount of fuel clinging to the port walls, etc., and
Tau, the time it takes for the fuel to dissipate.
Both these variables can be a function of MAP, RPM, and coolant temperature. C.F. Aquino came to the conclusion that the value for X stays relatively constant for a given engine, but that Tau is a function of many variables.

Below is a listing giving a high level description of an X-tau calculation.
fi = mi - ((Mi/(tau/(dltau))) )⁄(1 – X) )
Mi+1 = Mi + X∙fi –( (Mi )⁄(tau/dlta))
Where
fi = total fuel injected
mi = total fuel going directly into combustion chamber
Mi = net fuel entering/leaving port wall
dltau = time (secx100) between tach pulses = dtpred
X = fraction of fuel injected which goes into port wall
tau = puddle fuel dissipation time constant (secx100) as function of map, rpm, coolant temp and air temp.
XTfcor = % correction to calculated fuel to ensure the calculated amount gets into the combustion chamber.
acceleration conditions, richer mixtures would be in effect from the current VE bin.
Air charging is also factored into the X-Tau calculation. Air charging is fully documented in the Aquino Paper; a brief introduction is given here. Air charging can be viewed in a similar fashion to the wall wetting phenomenon – intake runners introduce a capacitive effect, where air flow is not linear with respect to MAP. The illustration below should help explain the problem.

1) Note the amplitude of the ripples in the MAP sensor, and the overall amplitude of the MAP signal trend. The trend dominates over the individual ripples (for this case). The ripple magnitude depends on factors like RPM, sensor response, manifold+runner volume, etc.

2) Note the time scale of 10 milliseconds, and note the length of time of a single intake stroke (although RPM dependent). This may help answer the question of phase delay of MAP signal due to port placement and/or length of vacuum tubing. For MAP delay due to the LP filtering caused by the RC input filter, the R is 1K and the C is 0.22uf, giving a time constant of 220 microseconds (at 63%) - not a real factor here in comparison.

3) The extremely interesting thing here is the air flow. Notice the point where the throttle stops moving, the air flow rate reaches a maximum and actually starts slowing down to an equilibrium value. This is known as air charging, where the capacitive effects of the manifold/runner volume and the increasing air density peak when the thottle is moving, then settles back down. Note that the trend of the MAP reading does not indicate this - the MAP pretty much follows the throttle (or TPS) angle.”
(Bowling, 2006)
Old 21-05-2007, 09:22 PM
  #24  
ECU Monitor Enthusiast
BANNED
BANNED
iTrader: (1)
 
ECU Monitor Enthusiast's Avatar
 
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes on 0 Posts
Default

Rick,

Very interesting.

I have seen many equations involving different meanings of Tau.

You have just given me a new one "X-Tau"

I understand what the ecu needs to work but what you have said clears up why.


Nice calculation thats offten a best guess from my experience and
knowledge of how other ecu's work.
Old 21-05-2007, 09:28 PM
  #25  
Rick
15K+ Super Poster!!

 
Rick's Avatar
 
Join Date: May 2003
Location: Stockport, Cheshire
Posts: 15,885
Received 17 Likes on 17 Posts
Default

Millions of Tau's - i agree.... But strangely... only one pi....
Old 21-05-2007, 09:41 PM
  #26  
ECU Monitor Enthusiast
BANNED
BANNED
iTrader: (1)
 
ECU Monitor Enthusiast's Avatar
 
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes on 0 Posts
Default

Pi.....

Mmmm

They say Pi R squared. ???

The ones my mum bakes are round - Figure that out
Old 21-05-2007, 09:45 PM
  #27  
Stu.H
10K+ Poster!!
 
Stu.H's Avatar
 
Join Date: May 2003
Location: Brierley Hill
Posts: 11,973
Received 0 Likes on 0 Posts
Default

Im a bit p'd off coz I want some KFC now

Old 21-05-2007, 09:46 PM
  #28  
Rick
15K+ Super Poster!!

 
Rick's Avatar
 
Join Date: May 2003
Location: Stockport, Cheshire
Posts: 15,885
Received 17 Likes on 17 Posts
Default

Simon

never heard that one - u are clearly a geek
Old 21-05-2007, 09:47 PM
  #29  
Mr-Ford
Wahay!! I've lost my Virginity!!
 
Mr-Ford's Avatar
 
Join Date: May 2007
Posts: 86
Likes: 0
Received 0 Likes on 0 Posts
Default

I am sorry but you are again misunderstanding me,maybe i would be better off talking to the trees.

Mapping doesnt come easily.
Old 21-05-2007, 09:48 PM
  #30  
ECU Monitor Enthusiast
BANNED
BANNED
iTrader: (1)
 
ECU Monitor Enthusiast's Avatar
 
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Rick
Simon

never heard that one - u are clearly a geek
I am a geek because it was the only way to get my first cosworth
working the way I wanted it to be.

You on the otherhand are training to be one


Respect
Old 21-05-2007, 09:53 PM
  #31  
Rick
15K+ Super Poster!!

 
Rick's Avatar
 
Join Date: May 2003
Location: Stockport, Cheshire
Posts: 15,885
Received 17 Likes on 17 Posts
Default

I know... Tragic really.

I also have a deep affection for clubbing
Old 21-05-2007, 09:55 PM
  #32  
ECU Monitor Enthusiast
BANNED
BANNED
iTrader: (1)
 
ECU Monitor Enthusiast's Avatar
 
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Rick
I know... Tragic really.

I also have a deep affection for clubbing
Clubbing - Good Lad.

Me too in a big way as you may be aware...

Do you know anything about lasers ?, my other pet subject
Old 21-05-2007, 10:12 PM
  #33  
Stu @ M Developments
PassionFords Creator



iTrader: (12)
 
Stu @ M Developments's Avatar
 
Join Date: May 2003
Location: Blackpool, UK Destination: Rev limiter
Posts: 28,824
Received 95 Likes on 76 Posts
Default

I am actually Inspired. There are at least 2 people on PassionFord who knew the meaning of Tau.

And no Mr Ford... if you turned of all transient fuelling correction and used say, 1000cc injectors, you would still be able to get a car to idle nicely at 1% co with 3.5bar fuel pressure as TFC has no real effect at idle. If you want to pop up here tomorrow i will prove it as i am doing an extrenally gated GT30 on such injectors tomorrow, and it has a massive plenum so a transient nightmare.

What you will find, and this i can almost GUARANTEE, is that some tuner has told you about it because it sounds so fooking impressive to the un informed...

"I fully understand the fuelling and throttle angle related transients in an engine that are thus required to map the transient fuel correction parameters in such a way as i can make your greys run lean at idle where other mappers fail."

What absolute bollox... but i agree it sounds really impressive. In fact, It reminds me of a quote we fondly called "BBB"


"Bullshit Baffles Brains"
Old 21-05-2007, 10:32 PM
  #34  
Rick
15K+ Super Poster!!

 
Rick's Avatar
 
Join Date: May 2003
Location: Stockport, Cheshire
Posts: 15,885
Received 17 Likes on 17 Posts
Default

Simon - Lasers - i studied Physics at the university of Salford which did have - and may still do - a quite advanced underground laser lab. It never got really involved in it, but they were funded by the Tate to develop means of restoring old paintings using the lasers. The wavelenght was tuned in such a way that the bad stuff absorbed the energy and burnt off, but left the good untouched.

They used to do this demo to impress people. The prof would get a group of people, and say that light is infact invisible - which would puzzle a few people. The lights were then dimmed, and a smoke machine turned on. The lab would then come to life as thousands of lasers became visible, it really was impressive
Old 21-05-2007, 10:35 PM
  #35  
Rick
15K+ Super Poster!!

 
Rick's Avatar
 
Join Date: May 2003
Location: Stockport, Cheshire
Posts: 15,885
Received 17 Likes on 17 Posts
Default

Stu, what is the minimum pulse witdh change that L8 can do, and what sort of pulse width do u see on a 2 litre with 1000cc injectors? And does this factor in the injector opening time? THe actual fuel delivery period must be under .2mS!
Old 21-05-2007, 10:38 PM
  #36  
ECU Monitor Enthusiast
BANNED
BANNED
iTrader: (1)
 
ECU Monitor Enthusiast's Avatar
 
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes on 0 Posts
Default

Rick,

Excellent, would love to see such a place but unless I start a degree I
somehow doubt that will ever happen.

I built laser systems for entertainment displays such as clubs and skywriting but
have been looking at using them for measuring gas
composition out of exhaust pipes at long distances as a side line.....
Very interesting... Emissions "speed" guns here we come.

(For those who dont know, this is already a proven technology)

Anyway, sorry back on topic.
Old 21-05-2007, 10:40 PM
  #37  
ECU Monitor Enthusiast
BANNED
BANNED
iTrader: (1)
 
ECU Monitor Enthusiast's Avatar
 
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes on 0 Posts
Default

Rick,

Minimum pulsewidth before any movement
Old 21-05-2007, 10:40 PM
  #38  
Charlie Chalk
Unknown.
iTrader: (1)
 
Charlie Chalk's Avatar
 
Join Date: Oct 2003
Location: ...
Posts: 50,873
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by Rick

I also have a deep affection for clubbing
same here.... Same here!!
Old 21-05-2007, 11:10 PM
  #39  
Stu @ M Developments
PassionFords Creator



iTrader: (12)
 
Stu @ M Developments's Avatar
 
Join Date: May 2003
Location: Blackpool, UK Destination: Rev limiter
Posts: 28,824
Received 95 Likes on 76 Posts
Default

Originally Posted by Rick
Stu, what is the minimum pulse witdh change that L8 can do, and what sort of pulse width do u see on a 2 litre with 1000cc injectors? And does this factor in the injector opening time? THe actual fuel delivery period must be under .2mS!
Ive never had to go sub 1% mate, so have never had any way to really try, bar winding the fuel pressure up for teh hell of it, which ive no interest in doing. I will maybe try tomorrow just to see what the datalogger will report.

1000cc at std fuel pressure requires around 1.3ms total time at idle.
Old 22-05-2007, 09:48 AM
  #40  
JjCoDeX75
PassionFord Post Whore!!
 
JjCoDeX75's Avatar
 
Join Date: Jun 2003
Location: Exeter
Posts: 3,744
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Stu @ M Developments
Originally Posted by Rick
Stu, what is the minimum pulse witdh change that L8 can do, and what sort of pulse width do u see on a 2 litre with 1000cc injectors? And does this factor in the injector opening time? THe actual fuel delivery period must be under .2mS!
Ive never had to go sub 1% mate, so have never had any way to really try, bar winding the fuel pressure up for the hell of it, which ive no interest in doing. I will maybe try tomorrow just to see what the datalogger will report.

1000cc at std fuel pressure requires around 1.3ms total time at idle.
Stupid laymans question coming up.....

Given the above, and the limitations of the computer speeds of the time (compared to the modern stuff), in the hypothetical situation where an injector at idle required an open time of 0.2ms, would the solution not be to reduce the fuelling pressure on the rail in order to allow the injector to work for a longer period?

JJ


Quick Reply: Is 'TFC important?



All times are GMT. The time now is 01:24 PM.