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Variable Valve timing

  #1  
Old 06-20-2004, 06:29 PM
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Hi all,
Ok, It hasnt been done <_< , I wont be able to do it first <_< , but someone does NEED to do it B) . Anyway...heres my plan. Automakers have had variable valve lift and duration (read, V-TEC or VVTL-i) and Mazda has recently come up with (or was it Mitsubishi?) a three stage cam lift and duration...so heres my plan. Use a three stage design but have the lower stage an Atkinized setup (the Intake valve overlaps into the compression stroke reducing the volume of air consumed and compressed...read variable volume). The second stage would be the normal lift and the third the high lift for high rpm's. I was thinking that less air=less gas therefor atkinizing the timing when power isnt needed (read...lean burn) it could allow for efficient engines with the power to get out of the way of the Semi breathing up your butt. I'll do the calculations later not now....I hope it wasnt to cryptic.
Cheers,
Steven
 
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Old 06-20-2004, 06:36 PM
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Hi Steve:

___Except that the Atkinsonized ICE’s have a fixed compression ratio per volume. If you change that intake timing on the fly, the compression ratio is going to go way up which is nice for greater power but you are speaking of either a DSI type setup or a large pull back of the advance to prevent detonation. Heavier cranks, Rods, Pistons, and Heads to go along with the increased compression ratio will be needed as well … That and NOx will go through the roof!

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
 
  #3  
Old 06-20-2004, 06:44 PM
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Wayne,
I dont think you understood (err, I probably didnt explane it). OK, take the normal Honda 1.6 lt engine with V-TEC...it has its normal cam profile and the high lift/ duration. Add a third profile for low load situations that would overlap with the compressions stroke reducing the compression fro 9.6 to 7.6 or so (it works out better w/ a V-TEC installed echo 1.5 lt w/ a compressions ratio of 10.5 then reduce it to 8.5 at low loads). I'll do some calculations of projected power drop...hmm, I need to find some dyno curves.
Cheers,
Steven
 
  #4  
Old 06-20-2004, 07:13 PM
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Hi Steve:

___Ahhh, I get it. Start with a std. Vtec and create a low compression Atkinson from it instead of taking an Atkinson and creating a high compression std. VTEC … I don’t know, those Atkinson’s w/ std. compression ratio torque numbers are pretty anemic although at highway speeds and loads, who cares. Good point.

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
 
  #5  
Old 06-21-2004, 03:54 PM
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Wayne,
I was just thinking that with the difficulties brought up by lean burn this would be another solution.
Cheers,
Steven
 
  #6  
Old 06-21-2004, 04:02 PM
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Hi Steve:

___My mind was wondering a bit today as well … With VCM about to go mainstream in the HAH as well as a ton of GM products and others, I was thinking more along the lines of a Diesel with a VCM via an actual crank shaft disconnect instead of valve timing. I am sure it would be more expensive but I can bet there would be better then just 15% increase in fuel economy (VCM adds about this in the real world) with that mod. Another idea I was bouncing around after reading your thread the other day was having VCM added to the lean burn 1.3 L 4. I have heard Honda is working on VCM for the 4 bangers and with that, let’s place that engine in the “Fit” or “City” directly! 60 + shouldn’t be a problem from the std. SI ICE in those 2 automobiles with this technology installed. Or just give me the iCDTi in a 1.0 – 1.3 L format in a “Fit” for 70 + and I would be a very very happy camper

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
 
  #7  
Old 06-21-2004, 05:01 PM
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Wayne,
A crank disconnect will not...I repeat WILL NOT work. (err, it would require separate cams all its own timed with it...the catch wouldnt be in the correct spot every time). The problem with GM's VCM (that the variable volume right?) is that it only shuts down the valves of the pistons. This is compressing and expanding static air for every rev...plus its dragging copper around on the piston walls. In addition...hypermilers would have to heat the cylinders back up when they needed the power. I was thinking on my commute today (oooo, look at my last tank ) that the atkinized V-TEC would require a variable intake manifold...but thats pretty simple.
Cheers,
Steven

Oh, I was also thinking...why the heck are milage machines not using boxter engines?!? The way they balance themselves out kills the need for the extra weights on the crank...less spinning weight....same as reducing the weight of wheels.
 
  #8  
Old 06-21-2004, 06:20 PM
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Hi Steve:

___Yes, separate cam shafts and cranks but coupled through an electric clutch (ala MDX’s RWD). Same block and external HW to save on having 2 engines in the thing.

___VCM is the acronym for Variable Cylinder Management and it works. It will be included in the 05 Honda Accord Hybrid but is only good for ~ 15% increase in highway fuel economy from what I have read. Those that have driven it say it’s seamless other then a light on the dash stating that you are in VCM mode under low load. When stepped on, those idle 3 cylinders fire back up almost instantly for V6 power as expected. It somehow shuts down 3 of 6 cylinders but I am not sure if it buttons up the cylinder at TDC, somewhere in mid travel, BDC, or simply opens them up to another port/valve/hole whatever and lets the piston run the distance with no fuel or ignition? I would think shutting off all valves at TDC w/ an exhaust valve being open up to the last fraction of a millisecond before TDC to bleed off any cylinder pressure and closing up immediately afterwards would be the best idea but I don’t have a clue as to how it really works. IIRC GM tried this way back in the 80’s before they had exacting control of the valve timing via solenoids but it didn’t work very reliably. Today’s valve timing capability is not only much more capable but is much more reliable as well.

___As for Boxster engines, I haven’t a clue as to what you are speaking of? Is that a Porsche Boxter’s flat 6?

___Another item that you are going to love. In the Honda Insight, the IMA acts as the balance shaft! That is how Honda made the 1.0 L so light and responsive as it doesn’t have a group of balance lobes or any other such thing on the crank!

___Lastly, great last fill from the Corolla! Considering where you were just a few months ago to where you are today is simply amazing. Just don’t lose your head. Scream, yell, swear (under your breath of course), and/or wave your arms around like a crazy person but keep that accelerator working slow and steady in accordance to the roadway your Corolla is traversing at the moment. At least that is the way I handle it when something isn’t quite right and I can’t figure it out immediately

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
 
  #9  
Old 06-21-2004, 06:29 PM
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Wayne,
_I wasnt meaning the current VCM doesnt work...just some drawbacks that reduce its effectiveness.
_I didnt know that the Insight 1lt didnt have balancing lobes...does the 1.3lt from the HCH?
_This is a good website about different engine set ups...the boxer is at the bottom http://64.233.161.104/search?q=cache:4U9fQ...-6+inline&hl=en
_Thanx about the tank...I think the other drivers on my commute are starting to recongnize me and shift over sooner. They just dont seem to ride my tail as much.
Cheers,
Steven
 
  #10  
Old 06-28-2004, 06:30 PM
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ARG! I hate my brain! I just realized today that with the cylinder forcing air back out during the compression stroke that the vacume in the manifold would be reduced so denser air would be entering the cylinder...grrr. (well, im getting mad but its not really screwing anything up...im sure someone out there understands)
Cheers,
Steven
 

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