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Fifty50Plus
Joined: 28 Feb 2008
Posts: 1422
Location: Washington DC area
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 Posted: Thu Aug 15, 2013 1:53 am Post subject: |
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| fiat22turbo wrote: | Depending on how hard it is to update the CIS to use the lambda-controlled frequency valve (too bad Unwired Tools never really lived up to their promise), that might be an option.
Although both would be bandaids where converting to EFI with programmable ignition would ultimately make the most gains. |
As Stefan says, it's tough to use the Lambda to control fuel through the frequency valve. We tried to control the lambda via a wideband output signal and found that the results were a CO output sine wave of + or - .2 CO with a cycle of about 1 second from peak to peak. This is many cylinder firings non optimum. We gave up and went to controlling fuel pressure to get a more constant CO reading. All of this was with an '82 fuel distributor and flapper. Quite different from a '77 system.
If you want the best results, go for EFT and programmable ignition as everyone suggests. Unfortunately SCCA rules don't allow EFT so we will plug along with this system on our race car. BTW, a street car will benefit quite a bit more from programmable ignition than a race car. Race care = WOT all the time above 4300 RPM vs variable throttle and RPM for a street car. Ignition mapping can help the street car more than a race car.
Chuck
_________________
1979 924 NA race car H-Prod SCCA
1982 924 NA race car - Sold
1981 924 Turbo sold
1982 924 Turbo sold
1972 911 E race car - traded for Cayenne Diesel
1975 914 1.8 Building for H-Prod SCCA |
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gegge
Joined: 27 Jul 2007
Posts: 1124
Location: Sweden
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| Posted: Thu Aug 15, 2013 6:06 pm Post subject: |
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| MikeJinCO wrote: | Ty, I have built a home made variable pressure flow bench and have now tested both a standard NA(40mm intake valve) head and a 931 head this summer. On the NA head I tried it bare, with a inlet stack, with a stock manifold and finally with the throttle body attached. I found that with the manifold the head flow was very comparable to having a stack(3"). However once I installed the small throttle body the flow was choked back significantly. My '77 throttle body was from a CA air pump car and probably the smallest ever made. I would consider ugrading the throttle body to the Audi 5000 version.
I can get numbers tomorrow, not CFM, I can only do flow changes as this point. |
I am very interested in your findings, please post the result.
By reading "924 BOLT ON BONANZA THE SEQUEL – Getting something for something" by Richard Holdener the author tested the flow of the head and is was more than 140 cfm from 0.350" to 0.500" and ported close to 200cfm.
Compare those numbers to the ones presented in the previous article in the bolt on bonanza series when they measure the intake runners, 152cfm, and the throttle body - 108cfm.
108cfm!
I have ported the intake runners on my 924 NA since the runners are tighter and more narrow than the duct in the head. Just measure the diameter. I have not decided if the Weber or Audi throttlebody is the one to have yet. The exhaust manifold is restrictive, but doesn´t perform badly since the pressure is much higher. Exhaustgasspeed is way more important scavenging the cylinders.
(The car in "Bolt on" had the Eurorace head and larger exhaust. A larger throttle did nothing except kill low-speed performance. By swapping to dual 40mm carbs it managed to overtake a 924 turbo easily.)
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Carl Fredrik Torkildsen
924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs |
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MikeJinCO
Joined: 08 Jun 2010
Posts: 1245
Location: Maysville, Colorado
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| Posted: Thu Aug 15, 2013 11:37 pm Post subject: |
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I'll try to get some data together in a day or so in a new thread. At this point I only have raw data. Since I'm a beginner at this some or all of it may be highly questionable.
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Mike
'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild) |
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Cedric
Joined: 27 Aug 2004
Posts: 2809
Location: Sweden
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| Posted: Sun Aug 18, 2013 8:15 pm Post subject: |
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| Arvidw wrote: | | For comparison: Dutchpug dyno'ed two quite high milage stock 924 2.0 NA euro cars on his Dynapack dyno and both produced 92whp. (Yes, I am aware you are not supposed to compare results from different dyno's) |
Was that on rollers?
remove 15% due to alltitude=78whp, and then remove some power from higher ambient T aswell (dont know the difference here, but dutch should be sea level, or lower  ). We dont know anything about sweep times, dyno model, tyre pressure, strapping force, tyre size/type etc. But sound kind of reasonable. Dont forget alltidue, it kills a NA engine pretty efficiently...
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1980 924 Turbo
www.instagram.com/garagecedric/ |
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morghen
Joined: 21 Jan 2005
Posts: 9095
Location: Romania
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| Posted: Sun Aug 18, 2013 10:25 pm Post subject: |
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| morghen wrote: |
AFR seems wrong to me.
You start too lean(14.7?) at 3000RPM and end up too rich(12.5?) at 6000RPM
I'd expect to have @12AFR at 3000RPM and then lean out to 13.7 @6000RPM |
Hellooo!!!
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Supercharger and EFI kits
https://www.the924.com |
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tyfighter123
Joined: 19 Jan 2010
Posts: 551
Location: Colorado
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| Posted: Mon Aug 19, 2013 2:47 am Post subject: |
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| morghen wrote: | | morghen wrote: |
AFR seems wrong to me.
You start too lean(14.7?) at 3000RPM and end up too rich(12.5?) at 6000RPM
I'd expect to have @12AFR at 3000RPM and then lean out to 13.7 @6000RPM |
Hellooo!!! |
I think your right! I don't think the fuel system is matched to the engine very well. The car started as a 95 hp California car. I really don't want to go to EFI yet, but I do want to get more out of the engine. I have dyno time this Wednesday I am going to see what my mechanic and I can come up with.
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Porsche 924 1977 N/A
Mustang GT/CS 2007
Porsche 924S 1987 (parts car)(cut up and recycled)
Porsche 911S 1976
Porsche 931 1980
Porsche 931 1980 (parts car) |
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morghen
Joined: 21 Jan 2005
Posts: 9095
Location: Romania
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| Posted: Mon Aug 19, 2013 4:05 am Post subject: |
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You need to be stoich at expected max power RPM and a bit rich before expected max torque.
Someone back me up on this one or say otherwise..but for low rpm grunt you need to be rich and for max power at high rpm you need to be stoich.
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Fifty50Plus
Joined: 28 Feb 2008
Posts: 1422
Location: Washington DC area
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| Posted: Tue Aug 20, 2013 5:06 am Post subject: |
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We've found that you need about 12.5 - 12.9 for max power across the rev range. Stoic at high revs creates more heat and less power than the 12.+ reading ( but less harmful emissions )
Chuck
_________________
1979 924 NA race car H-Prod SCCA
1982 924 NA race car - Sold
1981 924 Turbo sold
1982 924 Turbo sold
1972 911 E race car - traded for Cayenne Diesel
1975 914 1.8 Building for H-Prod SCCA |
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ptheskil
Joined: 03 Aug 2004
Posts: 128
Location: Essex, UK
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| Posted: Tue Aug 20, 2013 8:21 am Post subject: |
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Yep. 12-13 afr range for peak torque throughout the rev range. Esp. on a turbo as rich as you can get away with for peak pwr and beyond. If you have mapped ignition or a knock sensor you will find that the richer you go the more spark advance you can run - that buys you more torque than you lose by going richer than the optimum afr.
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1981 931 series2 Euro spec |
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Arvidw
Joined: 20 Sep 2009
Posts: 227
Location: The Nederlands (Europe)
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| Posted: Tue Aug 20, 2013 4:02 pm Post subject: |
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| Cédric wrote: |
Was that on rollers?
remove 15% due to alltitude=78whp, and then remove some power from higher ambient T aswell (dont know the difference here, but dutch should be sea level, or lower ). We dont know anything about sweep times, dyno model, tyre pressure, strapping force, tyre size/type etc. But sound kind of reasonable. Dont forget alltidue, it kills a NA engine pretty efficiently... |
He's got dynapack4000's which are hub-dynoes. So no tyre size, strapping force, tyre pressure etc. Sweep times of approximately 10s.
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Porsche 924 2.0 Kompressor 136.1wHp @ 5650rpm / 201.9wNm @ 3900rpm (dyno @ dp-engineering.nl) |
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924 FAQ (Technical)
