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?
Personally I'd be more concerned about its performance under load.
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]
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 ?
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.
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.
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]
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]
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]
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?
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
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
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?
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.
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...
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.
Simplicity... noise... top-end power... YEAH BABY - YEAH!
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.
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.
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.
That's pretty much my suspicions too MrWibble... refinement and emissions.
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....
quote:
Originally posted by coyoteboy
Is it normal to lighten the fly to get a nicer response?