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Volumetric Efficiency calculator- need some figures /checked
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augidog  



Joined: 03 Mar 2003
Posts: 1360
Location: New Jersey

PostPosted: Sun Aug 21, 2005 7:41 am    Post subject: Volumetric Efficiency calculator- need some figures /checked Reply with quote

I found this site.
http://www.stealth316.com/2-air-fuel-flow.htm
With these calculations I figured the 1984 displacement ,at 1000 rpm,
Natural Capacity 100%,Density ratio 1.=574.07 CFM
If I divide this # by 4 should I have the optimum air flow for one runner?
=143CFM 100% VE
Then by using the results from air flow data from "bolt on Bonanza" below
http://www.geocities.com/the_924_site/BOB1_4.html
It seems that the intake manifold is ported more than than enough to allow for 100% VE airflow.
Therefore the problem lies in getting the right TB to hit that 143cfm.
With the restrictor in, the 108CFM is to small, without it at 158CFM its' too big.
This is why a Larger TB upgrade never had any results in HP.
They were going too big when they actually had to fine tune the TB to narrow the opening just a little from 152 to 143cfm.
The closer we get to that 142cfm the smoother and quicker the entire throttle response will be.
Does this make sense or did I figure this wrong?
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leadfoot  



Joined: 11 Dec 2002
Posts: 2222
Location: gOLD cOAST Australia

PostPosted: Sun Aug 21, 2005 2:53 pm    Post subject: Reply with quote

I would think natural capacity would not be 100% as there is a 180 degree bend in the intake, and there is frictional losses due to surface materials.
Most books give an ideal VE of a non forced induction motor to be around 80 - 88% for older two valve engines. All my calculations were adjusted by 15% after I did my supercharger setup and this seems to mesh with the results I get from my ecu, handy having a MAP sensor!!.
Of course I had flow losses from my SC, intercooler and cam as well, but if you gave yourself this margin it might prove to be more acurate.
Leadfoot
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CBass  



Joined: 03 Nov 2002
Posts: 2807
Location: Vancouver, Canada

PostPosted: Thu Aug 25, 2005 3:50 pm    Post subject: Reply with quote

The trick to getting 100% VE is to overcome the inefficiencies inherent to the engine with inertia supercharging. My 924 is modified, but I sincerely doubt I make more than 140-150hp. The head is junk, and either needs to be seriously reworked or it needs to be junked.

One of these days I'm going to hit up a dyno day, and it's going to make me cry...
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Peter_in_AU  



Joined: 29 Jul 2001
Posts: 2738
Location: Sydney, Australia

PostPosted: Thu Aug 25, 2005 4:50 pm    Post subject: Reply with quote

I was reading recently that most older two-valve engines are in the 75% to 85% VE range (they were talking about pushrod V8s) and most modern four-valve engines are in the 85% to 95% range.

I'd guess a 924 would probably average around 85%. Don't forget that VE changes over the entire rev range.

The Honda S2000 engine is rated at slightly over 100% VE (a slight supercharge) but then that engine has won SAE awards because it's so insanely amazing.
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1982 924 (As featured on Wikipedia)

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Raceboy  



Joined: 01 Mar 2004
Posts: 2318
Location: Estonia, Europe

PostPosted: Thu Aug 25, 2005 6:16 pm    Post subject: Reply with quote

Peter_in_AU wrote:


The Honda S2000 engine is rated at slightly over 100% VE (a slight supercharge) but then that engine has won SAE awards because it's so insanely amazing.


And it has almost NO torque (less than hp) in my justification, which is a big no-no IMO.
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'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
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'84 928 S
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Peter_in_AU  



Joined: 29 Jul 2001
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Location: Sydney, Australia

PostPosted: Thu Aug 25, 2005 7:41 pm    Post subject: Reply with quote

Raceboy wrote:

And it has almost NO torque (less than hp) in my justification, which is a big no-no IMO.


Unfortunately no torque is the downside of getting over 100hp per litre from a naturally aspired production engine. Note I said "production engine".

I haven't driven an S2000 but all the reports from writers whose opinions I respect say that Honda totally messed up matching the gear ratios to the engine. I suppose the "correct" transmission would be one with an infinitely variable ratio that would hold the engine at 9500 rpm all the time. They're still working on those.
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1982 924 (As featured on Wikipedia)

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Raceboy  



Joined: 01 Mar 2004
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Location: Estonia, Europe

PostPosted: Thu Aug 25, 2005 8:29 pm    Post subject: Reply with quote

I have driven it 2 times, and IMO with 240hp it should accelerate MUCH better, than quoted 6.8s 0-100kph. I totally agree with you Peter about those gear ratios.
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'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
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Peter_in_AU  



Joined: 29 Jul 2001
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Location: Sydney, Australia

PostPosted: Thu Aug 25, 2005 9:50 pm    Post subject: Reply with quote

I suppose that the scientific equations are:

big hp/kw = magazine covers

big torque = low ETs


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1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

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Lizard  



Joined: 03 Nov 2002
Posts: 9364
Location: Abbotsford BC. Canada

PostPosted: Fri Aug 26, 2005 12:40 am    Post subject: Reply with quote

that is why the boxster hoses the S2000, torque,

I would rather have 300ft lb and 300bhp as supposed to 200ft lb and 400hp,
but then again just remember that high torque is what causes things to break in the drivetrain.
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CBass  



Joined: 03 Nov 2002
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PostPosted: Fri Aug 26, 2005 2:03 am    Post subject: Reply with quote

The S2000 makes more torque than the 924. The original 2.0 liter S2000 made 150ftlb, so 75ftlb/liter, the same figure which was so impressive when the 968 was built. Also, it has two distinctly different cam profiles, and excellent port velocity, so it's really quite driveable at low speeds. Just don't expect it to pull like it has a 5 liter engine, because it doesn't.

Sure, it's no diesel, but drive any classic sports car and you'll find yourself noting it seems to lack torque.
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Raceboy  



Joined: 01 Mar 2004
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Location: Estonia, Europe

PostPosted: Fri Aug 26, 2005 3:01 am    Post subject: Reply with quote

Sry CBass, but as a car journalist, I've driven MANY sportscars (including new 997 S at the racetrack on Tuesday ) and S2000 has: 1) a powerband too high for normal street usage 2) no suitable gearbox to use it's powerband on the track. That's a lousy combination IMO. If it had a good (suitable for high revs) gearbox, it would be excellent ride on the track, but with what it has now, how to put it? No fish, no meat, I don't know what it is....
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'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
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leadfoot  



Joined: 11 Dec 2002
Posts: 2222
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PostPosted: Fri Aug 26, 2005 2:12 pm    Post subject: Reply with quote

"Suitable for turbocharging"

"Powerhouse Amuse in japan has strapped a Trust TD06-20G to a standard 11:1 engine and changed the stock 180nM @6000rpm to a more pleasant 240nM @4000rpm at .45bar"

I'd like to see a whipple strapped to it instead, sacrifice a few top end ponies for some really usable torque. You could easilt fit a eunos charger down the side of the engine bay bolted onto the intake.
Leadfoot
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J1NX3D  



Joined: 06 Feb 2003
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Location: New Zealand

PostPosted: Fri Aug 26, 2005 3:30 pm    Post subject: Reply with quote

i think u guys will like this thread from rennlist
http://forums.rennlist.com/rennforums/showthread.php?t=221549
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CBass  



Joined: 03 Nov 2002
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Location: Vancouver, Canada

PostPosted: Sat Aug 27, 2005 1:49 am    Post subject: Reply with quote

http://www.aempower.com/pdf/dyno/24-6104%202004%20Honda%20S2000%20Dyno%20Numbers.pdf

Dyno sheet for an original 2.0 liter S2000. It's a bit soggy between 1500-2500rpm, but so's a 931 The least torque you're seeing is still over 100ftlb, which in my 2100 lb GTI feels quite torquey. By comparison, the 3.0 liter 968 has a flat torque curve of 150-160ftlb from 2000-3000, and makes the same peak hp roughly. The S2000 is about as torquey down low as a VW 2.0 16v, which is also mated to tall gears. It won't pull stumps but it's still quite liveable. Keep in mind, any built N/A 2.0 liter engine is going to be lacking in the bottom end, even most built 3.0 liter engines are.

I think we're taking a lot for granted these days... It's a sports car, it's not mean to be practical, it's not meant to haul groceries or pull trailers... It's meant to gobble up twisty roads, and they do that quite well. Sometimes I feel like us 924 owners have been spoiled by our practical and easy to drive cars.

As for the gearbox, where do ya think the quote of "mad tight third gear VTEC" comes from?
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Peter_in_AU  



Joined: 29 Jul 2001
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Location: Sydney, Australia

PostPosted: Sun May 27, 2007 11:57 am    Post subject: Reply with quote

Thought some of you might be interested in this. It`s the VE table from a GM/Delco computer for a Holden Camira (4 cylinder, normally aspired, SOHC, 86mm bore, 1998cc - sound familiar?):

Code:

F29H: Volumetric Efficiency (VE) as a function of MAP and RPM

    RPM                          MAP
           20     30     40     50     60     70     80     90     100
   7200    60.55  62.50  64.45  66.41  68.36  70.31  70.31  70.31  70.31
  6400     60.55  64.45  68.75  70.70  77.34  78.52  76.17  78.91  82.81
  5600     60.55  69.14  76.95  80.86  85.16  85.94  87.89  88.28  87.11
  5200     64.45  69.92  76.95  83.98  88.28  89.84  89.84  90.63  89.84
  4800     64.45  70.70  78.91  84.38  88.28  89.84  91.02  91.41  91.02
  4400     64.45  70.70  78.91  83.59  87.11  88.67  91.41  92.19  91.02
  4000     60.55  71.88  76.95  81.64  84.38  87.11  88.67  91.41  89.84
  3600     56.64  66.41  72.66  76.95  80.08  83.20  85.94  88.28  89.84
  3200     52.73  60.16  68.36  73.83  76.95  80.86  83.20  85.16  91.02
  2800     58.59  62.89  70.31  76.17  78.13  80.47  82.42  83.59  87.11
  2400     59.77  71.09  76.17  78.52  81.64  83.20  83.98  85.94  87.89
  2000     60.55  66.41  70.70  75.39  78.91  80.08  82.03  85.55  91.02
  1600     58.59  70.31  74.22  77.34  77.73  79.69  82.42  85.16  86.72
  1200     62.50  63.28  68.36  71.48  73.44  75.39  76.17  78.13  78.13
  800      60.55  62.50  64.84  66.41  68.36  70.31  72.66  76.17  74.22
  600      56.25  56.25  57.42  61.33  63.67  65.63  67.58  71.48  71.48
  400      54.69  54.69  56.25  58.59  60.94  63.28  66.41  66.41  66.41

_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you
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