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Cedric
Joined: 27 Aug 2004
Posts: 2609
Location: Sweden
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 Posted: Tue Aug 15, 2023 7:34 am Post subject: |
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Hey, thats my parents kitchen table with my guages, must be oold that pic:) i just made two 52mm holes in the plastic Radio grill, covered it in a thin glued aluminium sheet and covered in black vinyl. It still looks good after all these years, would be easy to replicate.
That compressor should be good to 1bar of boost while still being reasonably in the map.
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1980 924 Turbo
www.instagram.com/garagecedric/ |
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chuck21401
Joined: 20 Feb 2005
Posts: 526
Location: Annapolis, MD
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| Posted: Tue Aug 15, 2023 8:09 am Post subject: |
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| Cedric wrote: | | Hey, thats my parents kitchen table with my guages, must be oold that pic:) i just made two 52mm holes in the plastic Radio grill, covered it in a thin glued aluminium sheet and covered in black vinyl. It still looks good after all these years, would be easy to replicate. |
Lol. Found on Google. Nicely done.
Here's a different pic, Ideola's garage was selling them at one point?
| Quote: | | That compressor should be good to 1bar of boost while still being reasonably in the map. |
I've run 1 bar (~14.5 psi) no problem in terms of making the boost....when I was first adjusting the manual boost controller it ran north of 15....maybe just under 20psi but I couldn't keep my eyes on the gauge.
What does "while still being reasonably in the map" mean? In terms of the air fuel ratio? Going lean would be bad. I'm using the stock CIS system...not ready to make the jump to EFI. Plus the internals are all stock....seems like 15psi would be the max for me at this point.
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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler |
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Cedric
Joined: 27 Aug 2004
Posts: 2609
Location: Sweden
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| Posted: Tue Aug 15, 2023 7:19 pm Post subject: |
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| chuck21401 wrote: | | Cedric wrote: | | Hey, thats my parents kitchen table with my guages, must be oold that pic:) i just made two 52mm holes in the plastic Radio grill, covered it in a thin glued aluminium sheet and covered in black vinyl. It still looks good after all these years, would be easy to replicate. |
Lol. Found on Google. Nicely done.
Here's a different pic, Ideola's garage was selling them at one point?
| Quote: | | That compressor should be good to 1bar of boost while still being reasonably in the map. |
I've run 1 bar (~14.5 psi) no problem in terms of making the boost....when I was first adjusting the manual boost controller it ran north of 15....maybe just under 20psi but I couldn't keep my eyes on the gauge.
What does "while still being reasonably in the map" mean? In terms of the air fuel ratio? Going lean would be bad. I'm using the stock CIS system...not ready to make the jump to EFI. Plus the internals are all stock....seems like 15psi would be the max for me at this point. |
Yeah there was some kind of guage pod very similar to my diy one that was sold for a while. But it only takes a few hours to modify a stock grill, the worst was cutting the old plastic with a grinder, smelled like nothing else, not sure what they had in those 70s plastic.
I mean that the turbo will keep within reasonable shaft speed and reasonable efficiency, which also means reasonable back pressure. I did a bunch of engine simulations on the turbos (used to be my job) a while ago and i think concluded that the 2664 would be good up to that boost on these engines.
I have the larger 2670 and one step larger turbine, and I seemed to ran out of CISat 1 bar, where it in general ran good but at the absolute end of the rev range it creeped up to high 11s in AFR.
Heres some data which, not sure exactly what logs i had when i generated these. I have lots of jumping around in the rpm signal sadly so discard all the red and organge cells, most of them arent real, green means theres more data in data point. So it seems to hold up well to 1 bar which should be in the region of 245 hp, probably maybe 15-20hp less with your smaller turbo. But your system is different, both turbo and US fuelling. So you can just creep up slowly and see how far the system keeps up, if you want to keep safe keep yourself below 1 bar and it should be good, its quite fast at those boost levels anyway. What ignition system do you run?
The internals can take alot, way more than these boost levels, as long as you keep out of detonation ! And thats a very important bit!
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1980 924 Turbo
www.instagram.com/garagecedric/ |
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chuck21401
Joined: 20 Feb 2005
Posts: 526
Location: Annapolis, MD
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| Posted: Fri Aug 18, 2023 11:54 pm Post subject: |
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| Cedric wrote: | | Heres some data which, not sure exactly what logs i had when i generated these. I have lots of jumping around in the rpm signal sadly so discard all the red and orange cells, most of them arent real, green means theres more data in data point. So it seems to hold up well to 1 bar which should be in the region of 245 hp, probably maybe 15-20hp less with your smaller turbo. But your system is different, both turbo and US fueling. So you can just creep up slowly and see how far the system keeps up, if you want to keep safe keep yourself below 1 bar and it should be good, its quite fast at those boost levels anyway. |
Very interesting data! This week I turned the boost back up to 1 bar....it's difficult to turn the dial back down. 1 bar is about as far as I will go for now. It is interesting to see that max intake temps go up proportionally (or more!) to boost increases. So still considering a larger heat exchanger up front at some point.
The car feels as fast as I need to go...especially with the windows down and the roof off. The reality could be a that a modern Toyota Corolla is faster....but for me the fun is driving an old car fast.
| Cedric wrote: | | What ignition system do you run? |
Stock S1 ignition. NGK B8EGV spark plugs. Accel Super Stock Coil 8140. Recent cap/rotor/wires. Set the timing according to the manual with a timing light.
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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler |
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Cedric
Joined: 27 Aug 2004
Posts: 2609
Location: Sweden
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| Posted: Sat Aug 19, 2023 12:23 am Post subject: |
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What afr do you end up with at 1 bar ?
With s1 ignition you will rung very safe timing, since the timing curve is made for a non intercooled engine. The s2 on the other will advance massively since it bases ignition on intake temperature(probably a bit to much for my liking), which makes the power difference quite significant already at stock boost. If you run 93 octane you could probably use more timing advance to keep EGT down and get more power, or just let it be 
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1980 924 Turbo
www.instagram.com/garagecedric/ |
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chuck21401
Joined: 20 Feb 2005
Posts: 526
Location: Annapolis, MD
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| Posted: Sun Aug 27, 2023 11:31 pm Post subject: |
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Whoops duplicate post. Don't see a button to delete it.
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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler
Last edited by chuck21401 on Tue Aug 29, 2023 2:09 am; edited 2 times in total |
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chuck21401
Joined: 20 Feb 2005
Posts: 526
Location: Annapolis, MD
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| Posted: Mon Aug 28, 2023 10:07 pm Post subject: |
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| Cedric wrote: | | What afr do you end up with at 1 bar ? |
I believe the afr dips to high 10s-11s. Mid-14s when cruising.
I need a better video set up or maybe figure out how to log data. It's difficult to look at the gauges at full boost to get a reading. (I checked again yesterday...on boost mostly low 11s, occasional high 10s).
| Cedric wrote: | | With s1 ignition you will rung very safe timing, since the timing curve is made for a non intercooled engine. The s2 on the other will advance massively since it bases ignition on intake temperature(probably a bit to much for my liking), which makes the power difference quite significant already at stock boost. If you run 93 octane you could probably use more timing advance to keep EGT down and get more power, or just let it be |
I've run 93 octane since I bought the car...until yesterday.
I had to buy some gas from a station that charges too much. Premium (93 octane) was $4.99/gallon and I'm used to paying around $4.20/gallon. So I decided to try 5 gallons of mid-grade (89 octane). I was surprised to see the pre-intercooler temps (on boost) increase by 20-30F degrees ! At cruising speeds there was little difference but as soon as the boost kicked the temps climbed quickly. Ambient air temps were around 80F. The after intercooler temps increase by maybe 10F degrees....with max temps on boost at probably 110F.
I've read through a number of threads regarding ignition timing...I don't see a recommendation about how much advance to run for more power....for intercooled engine. Maybe I should try 25 degrees BTDC with 93 octane?
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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler |
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safe
Joined: 18 Mar 2017
Posts: 588
Location: Sweden
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| Posted: Mon Aug 28, 2023 10:25 pm Post subject: |
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| chuck21401 wrote: |
Premium (93 octane) was $4.99/gallon and I'm used to paying around $4.20/gallon... |
4.99 oh, takes me back to ~2010.... if only we had gas that cheap!!
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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe |
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Carrera RSR
Joined: 08 Jan 2010
Posts: 2309
Location: Somerset, UK
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| Posted: Wed Sep 20, 2023 8:19 am Post subject: |
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| chuck21401 wrote: |
I've read through a number of threads regarding ignition timing...I don't see a recommendation about how much advance to run for more power....for intercooled engine. Maybe I should try 25 degrees BTDC with 93 octane? |
A dyno session will see the best ignition v boost v cam timing.
Challenges - the stock distributor curve is too safe for IC equipped 924 turbo
The WUR dumps too much fuel in during mid range rpm on boost making it run too rich and also limiting power.
There's only so much optimisation of 1970's technology before you start dumping too much time and money into it.
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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