coyoteboy
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| posted on 15/2/11 at 10:10 PM |
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Duratec V6
I've been scoping out all the V6s and concluded the duratec v6 (2.5) seems to have a horrifically slow throttle response when revved load-free,
and it appears to redline just shy of 7000rpm - bit of a low down slow slugger? Is it normal to lighten the fly to get a nicer response?
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interestedparty
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| posted on 15/2/11 at 10:13 PM |
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Personally I'd be more concerned about its performance under load.
As some day it may happen that a victim must be found,
I've got a little list-- I've got a little list
Of society offenders who might well be underground,
And who never would be missed-- who never would be missed!
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coyoteboy
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| posted on 15/2/11 at 10:24 PM |
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Naturally, but its unloaded throttle response is indicative of that (just loading the engine with its own mass).
Compare a (slightly smaller) but similarly powered v6:
http://www.youtube.com/watch?v=wWAX2T0Q5LE
Just seems to suggest either an engine with a lot of rotating mass or poor low down torque.
[Edited on 15/2/11 by coyoteboy]
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mcerd1
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| posted on 15/2/11 at 10:28 PM |
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you sure its not just a drive by wire throttle thing - i.e. you plant your foot to the floor, but teh ECU thinks it knows better ?
-
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coyoteboy
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| posted on 15/2/11 at 10:31 PM |
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That's an added complication I'd not considered, but the video I was watching had a non-FBW duratec so that would suggest not.
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RazMan
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| posted on 15/2/11 at 10:53 PM |
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On my Duratec V6 I lightened my flywheel to improve throttle response and it seemed zippy enough to me. Get rid of the secondary butterflies as they
don't help either. Throttle bodies seem to help even more 
They can make 200 bhp with just a simple change of exhaust and intake - an aftermarket ECU and a remap gives you a bit more and also improves throttle
response.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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coyoteboy
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| posted on 15/2/11 at 11:00 PM |
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Secondary 'flies really help a lot with low down torque, I'd not be removing them unless I was going way over stock power, even if
removing them helps a bit with upper end power. Been through that issue with the 3SGTE - disabling the butterflies trashes low down torque and idle
quality.
[Edited on 15/2/11 by coyoteboy]
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RazMan
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| posted on 15/2/11 at 11:06 PM |
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The V6 has got so much low down torque that you don't need any more on such a light car - it pulls like a train! Mine will go down to 20mph in
5th gear and still take off like a stabbed rat. If you are going to keep the secondaries you will have a hell of a job getting them mapped and I found
that the power curve was smoother without them anyway. They are just an unnecessary restriction that robs the engine of power IMO and the tickover is
even more stable than stock. If you want a more responsive throttle response, just ditch them - probably the reason why the FTO V6 revs so much
quicker
[Edited on 15-2-11 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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coyoteboy
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| posted on 15/2/11 at 11:15 PM |
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Not wanting to get into an argument about it, I'm not sure why you think secondaries cause such an issue - they're actually a really handy
item that can flatten the torque curve nicely. With one set of runners you get a torque curve that peaks at Xrpm, with them open and two sets you get
a peak at X+Yrpm, having the secondaries switch gives you the benefit of both torque peaks merged. In order to map the transition point you just do a
power pull with them closed and another with them open and pick the point half way between the peaks? No doubt they get in the way when really maxing
out the upper end of flow rates for a head but at anything lower than X+Y they're nothing but positive? Whether you need the low down torque is
a different matter I suppose and you do have an interesting point, but unless you only ever accelerate/perform above your secondary switch point the
low down torque is nice for me.
Ah well, we'll have to agree to disagree on this one! I tried both ways with my other engine and the difference made the car notably less
drivable, but I suppose that is a low compression high boost engine.
http://websworld.org/marcel/tech/tvis/tvis.html
[Edited on 15/2/11 by coyoteboy]
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MikeRJ
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| posted on 16/2/11 at 12:46 AM |
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quote:
Originally posted by coyoteboy
I've been scoping out all the V6s and concluded the duratec v6 (2.5) seems to have a horrifically slow throttle response when revved load-free,
and it appears to redline just shy of 7000rpm - bit of a low down slow slugger? Is it normal to lighten the fly to get a nicer response?
I wouldn't say a red line of just under 7000RPM for a V6 would suggest it's sluggish, that's more than a lot of inline 4's.
Most modern DOHC V6's thrive on revs though, the KV6 in my car is exactly the same and even the older 2.7L Honda V6 was reknown for it. If you
want something for pulling stumps out of the ground use one of the old Ford V6 boat anchors 
Lazy pickup is typical of modern production engines in general I find. A lot of it is programmed into the management to give smoother response, and
also enabling softer engine mountings to be used without excessive movement.
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RazMan
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| posted on 16/2/11 at 08:49 AM |
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quote:
Originally posted by coyoteboy
Not wanting to get into an argument about it, I'm not sure why you think secondaries cause such an issue
I understand the design intentions for the secondary runners and agree that they make quite a big improvement to the lower torque curve - a big
advantage in a heavy car like the Mondeo. My point is that a car weighing less than 800Kgs will not fully benefit from the extra low down torque. If
you want a cruiser which will pull at low revs then why build a lightweight sportscar in the first place when a Landy might be more suited to your
requirements? 
I have used my V6 for 5 years now and have slowly 'evolved' its state of tune in various stages from bog stock to its present level of
ITBs and I can tell you that it is a really lively, fun car now. Mine is the ST200 version and removing the secondaries made a noticeable improvement
to the mid range with no difference to the lower end power - certainly no dips anyway. Mapping was a lot easier as we discovered some irritating
'pulsing' with the secondaries and the power curve smoothed out noticeably when they were removed (the combined surface area of spindles
and butterflies is quite substantial) and about 20bhp was 'found' in the process too.
I have yet to get my new ITB version onto the rollers but I am hopeful to squeeze another 30 bhp out of it. It is now one of the most responsive
V6's I have encountered.
Well, you did ask
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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mrwibble
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| posted on 16/2/11 at 10:58 AM |
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quote:
Originally posted by RazMan
quote:
Originally posted by coyoteboy
Not wanting to get into an argument about it, I'm not sure why you think secondaries cause such an issue
I understand the design intentions for the secondary runners and agree that they make quite a big improvement to the lower torque curve - a big
advantage in a heavy car like the Mondeo. My point is that a car weighing less than 800Kgs will not fully benefit from the extra low down torque. If
you want a cruiser which will pull at low revs then why build a lightweight sportscar in the first place when a Landy might be more suited to your
requirements?
I have used my V6 for 5 years now and have slowly 'evolved' its state of tune in various stages from bog stock to its present level of
ITBs and I can tell you that it is a really lively, fun car now. Mine is the ST200 version and removing the secondaries made a noticeable improvement
to the mid range with no difference to the lower end power - certainly no dips anyway. Mapping was a lot easier as we discovered some irritating
'pulsing' with the secondaries and the power curve smoothed out noticeably when they were removed (the combined surface area of spindles
and butterflies is quite substantial) and about 20bhp was 'found' in the process too.
I have yet to get my new ITB version onto the rollers but I am hopeful to squeeze another 30 bhp out of it. It is now one of the most responsive
V6's I have encountered.
Well, you did ask
so as an independant observer on this debate, it would seem to me that it was easier to tune and get good results with this engine with only 1 set of
tbs with an aftermarket ecu. leave it to ford to play with complicated dual tb setups would seem my uneducated take.
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coyoteboy
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| posted on 16/2/11 at 11:39 AM |
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quote:
My point is that a car weighing less than 800Kgs will not fully benefit from the extra low down torque. If you want a cruiser which will pull
at low revs then why build a lightweight sportscar in the first place when a Landy might be more suited to your requirements?
This whole statement makes no sense to me unless you never use lower revs. Weight of the car is totally irrelevant in this field of argument as all
weight does is limit either acceleration and/or traction. If you're traction limited at low revs you'll be traction limited at high revs
and higher torque up at high revs will spin just the same as at low revs so you're stuffed. With respect to vehicle mass and acceleration of it,
more torque is always better regardless of the RPM it's achieved at, in fact low down torque is very often something people are willing to trade
top end power for. (many) People don't like the drive characteristics of a large turbo because you need to keep it high up in the range to get
any fun, same with the horrible gutless celica VVTi engines, I can't understand why anyone would aim that way on purpose when the benefits of
variable intake geometry are available and easy to tune (IMO). On a road going vehicle you don't spend most of your time bouncing off the
limiter - race vehicle sure.
Well, thats my point of view anyway, based around my own little monster tuning cockups and watching other people cock up theirs and helping to fix it.
If it worked for you then well done, you're one of the few who hasn't just removed them assuming they're a negative and not realised
the trade-off they've made  Everyone watches top end figures and pay little attention to the area under the curve, which is a mistake.
[Edited on 16/2/11 by coyoteboy]
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coyoteboy
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| posted on 16/2/11 at 12:31 PM |
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Though, to be fair as I say, you're running a NA engine so the secondaries will have more notable affect on top end than my application, and my
application feels bloody awful when low down torque is lost.
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scootz
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| posted on 16/2/11 at 01:51 PM |
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I'm with Raz.
I'd always remove secondary butterfly's if it's going into a lightweight kit.
Original induction off... and ITB's or Carbs on!
Let it breathe properly...
It's Evolution Baby!
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coyoteboy
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| posted on 16/2/11 at 02:05 PM |
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Still makes no sense. Engines work better at low revs with narrow intake runners and better at high revs with wider ones. It's just what
you're willing to sacrifice if you're trying to achieve headline figures at the top end. With secondaries it is breathing properly lower
down and up top. It's all about charge momentum at the ports, without secondaries you have sod all low down so you get lower cylinder fills and
less power. Ripping them out, IMO, is like going from EFI back to carbs - totally backwards unless the only think you're striving for is
simplicity and noise.
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scootz
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| posted on 16/2/11 at 02:14 PM |
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Simplicity... noise... top-end power... YEAH BABY - YEAH!
It's Evolution Baby!
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coozer
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| posted on 16/2/11 at 02:23 PM |
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Have a nose under the bonnet of an Aston Martin V12.
2 Ford V6's engineered into one. May be some clues as to the best induction.
1972 V8 Jago
1980 Z750
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mrwibble
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| posted on 16/2/11 at 02:34 PM |
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quote:
Originally posted by coyoteboy
Still makes no sense. Engines work better at low revs with narrow intake runners and better at high revs with wider ones. It's just what
you're willing to sacrifice if you're trying to achieve headline figures at the top end. With secondaries it is breathing properly lower
down and up top. It's all about charge momentum at the ports, without secondaries you have sod all low down so you get lower cylinder fills and
less power. Ripping them out, IMO, is like going from EFI back to carbs - totally backwards unless the only think you're striving for is
simplicity and noise.
now i'm only repeating what i've read else where (Mr A G Bell) but he says there are rules of thumb, but sometimes u have to throw out the
rule book as engines don't always behave as expected.
i would also suggest that ford have engineered the problem for economy and refined (read quiet) characteristics.
Keep It Simple Stupid was always my design and technology tutor's mantra.
but if you can get them to work prove us all wrong, as long as u post a vid of its first start
regards,
Ed.
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coyoteboy
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| posted on 16/2/11 at 03:10 PM |
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Yes, Ford will have done it partly to improve idle emissions and the secondary butterflies help in controlling knock when it's heard. But
secondaries don't alter "refinement"/sound in an OEM configuration - you'd never tell the difference, thats what the intake
tract upstream does and the resonator boxes fitted.
KISS certainly has its advantages, and open ITBs do definitely make me giggle so I'm all for it (and I reckon thats worth the loss alone so
I'm not saying he's taken the wrong route at all), but I'm fairly convinced as to the use of secondardies - theres a reason every
single manufacturer out there has used it (and are still using it) on some of their engines. Toyota, Ford, Honda etc etc. Toyota chose to scrap it on
their later 3S engines, primarily because they were aiming for higher peak powers to compete with others higher peak powers and the reduced complexity
saves a lot of cost.
As I say, we'll have to agree to differ If I had one I'd really have to seriously think about whether I wanted to have form over
function.
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scootz
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| posted on 16/2/11 at 03:13 PM |
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That's pretty much my suspicions too MrWibble... refinement and emissions.
It's Evolution Baby!
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coyoteboy
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| posted on 16/2/11 at 03:35 PM |
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I don't think it really affects emissions, other than improving fuel/air mixing at lower RPM for a better burn...and more torque per cc....
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RazMan
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| posted on 16/2/11 at 04:58 PM |
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quote:
Originally posted by coyoteboy
Is it normal to lighten the fly to get a nicer response?
Going back to your original question, I suppose the answer is yes ....... but better breathing helps too. Narrow primary runners tend to hinder the
'revvability' but when you open all the ports then the full potential is unleashed ...... but you might lose a fraction of low down torque
and maybe fuel efficiency - it's a no-brainer in a sportscar, surely.
Having tried both ends of the tuning scale on the same engine over 5 years (still more to go though), I know which one I prefer to drive
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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