My new 944 ... and it's issues

Naturally aspirated tech and talk
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Tom
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Those numbers look great to me. Very consistent, which is key since the absolute number will vary with temp, how long you crank, the amount of oil left on the walls, etc. As a rough reality check, if you multiply sea level air pressure (call it 14.7) by your static compression ratio (10.6:1 I believe?) you get just under 156, so I'd be pretty happy with those results on a 40 year old motor! Of course, the compression test numbers don't follow that formula exactly, since valve timing lowers the dynamic compression (vs the 10.6 static compression ratio) and compression heat increases pressure, but it puts you in the right ballpark to feel pretty good about those numbers. Also, you would likely see higher numbers if you warmed up the motor before the test. :shh:

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PSU_Crash
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9.5:1 US spec and 10.6:1 euro spec is what I read on rennlist. Seems odd the math works so well with 10.6 ratio though. I have no idea what may have been done to the internals of this, so who knows. Either way, I agree, seems quite healthy!
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PSU_Crash wrote: Sat May 17, 2025 8:36 am 9.5:1 US spec and 10.6:1 euro spec is what I read on rennlist. Seems odd the math works so well with 10.6 ratio though. I have no idea what may have been done to the internals of this, so who knows. Either way, I agree, seems quite healthy!
Ah, fair enough, I'm sure that's right. The formula is only coincidentally that close when using 10.6. The more accurate formula would take something like 7 or 8 as the dynamic compression ratio and raise it to the power of 1.2 to account for compression heat and multiply that by the atmospheric pressure at your elevation. But it comes out to the same basic ballpark...

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Been a long time since using PV=nRT Math seems legit. Just registered for my first car show with the ol girl. I'm excited to get out and about and mingle with the locals!
'86 Zermatt Silver 944 N/A :thumbup:
'86 Mitsubishi Starion - Purpose built SM class Autocross car
'87 Chrysler Conquest - Mid LS Swap

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ROB III
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PSU_Crash wrote: Sat May 17, 2025 9:09 am Been a long time since using PV=nRT Math seems legit. Just registered for my first car show with the ol girl. I'm excited to get out and about and mingle with the locals!
CONGRATULATIONS!
In record time no less!
Rob
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ROB III wrote: Sat May 17, 2025 12:51 pm
PSU_Crash wrote: Sat May 17, 2025 9:09 am Been a long time since using PV=nRT Math seems legit. Just registered for my first car show with the ol girl. I'm excited to get out and about and mingle with the locals!
CONGRATULATIONS!
In record time no less!
Thanks Rob!
Unfortunately it seems the "show" is a scam. Advertised free car entry, donations welcome! Then wanted $25 to register. Sure, that's fine. Then a half hour later wanted another $20 for "parking and raffle" Nope. Not today Satan!
Very dissapointing, but there will be more. Got her all shined up and cleaned the interior anyways
'86 Zermatt Silver 944 N/A :thumbup:
'86 Mitsubishi Starion - Purpose built SM class Autocross car
'87 Chrysler Conquest - Mid LS Swap

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PSU_Crash wrote: Sat May 17, 2025 12:58 pm
ROB III wrote: Sat May 17, 2025 12:51 pm
PSU_Crash wrote: Sat May 17, 2025 9:09 am Been a long time since using PV=nRT Math seems legit. Just registered for my first car show with the ol girl. I'm excited to get out and about and mingle with the locals!
CONGRATULATIONS!
In record time no less!
Thanks Rob!
Unfortunately it seems the "show" is a scam. Advertised free car entry, donations welcome! Then wanted $25 to register. Sure, that's fine. Then a half hour later wanted another $20 for "parking and raffle" Nope. Not today Satan!
Very dissapointing, but there will be more. Got her all shined up and cleaned the interior anyways
PCA show & shine season is almost upon us! Paying to show your car has always been counter-intuitive to me, unless it's for charity. With all the Tennessee Carpokeans, I'm guessing you guys could have your own get together...

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Tom wrote: Sat May 17, 2025 1:09 pm
PSU_Crash wrote: Sat May 17, 2025 12:58 pm
ROB III wrote: Sat May 17, 2025 12:51 pm
CONGRATULATIONS!
In record time no less!
Thanks Rob!
Unfortunately it seems the "show" is a scam. Advertised free car entry, donations welcome! Then wanted $25 to register. Sure, that's fine. Then a half hour later wanted another $20 for "parking and raffle" Nope. Not today Satan!
Very dissapointing, but there will be more. Got her all shined up and cleaned the interior anyways
PCA show & shine season is almost upon us! Paying to show your car has always been counter-intuitive to me, unless it's for charity. With all the Tennessee Carpokeans, I'm guessing you guys could have your own get together...
Lots of goings on in TN - Cars/Coffee, meets, etc. We had our Nashville area PCA's (Musik-Stadt) Concours today at 111 Motorcars in Franklin. A lot of nice cars but we could have used more transaxle participants... :angel:
Tim
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blueline wrote: Sat May 17, 2025 1:39 pm
Tom wrote: Sat May 17, 2025 1:09 pm
PSU_Crash wrote: Sat May 17, 2025 12:58 pm

Thanks Rob!
Unfortunately it seems the "show" is a scam. Advertised free car entry, donations welcome! Then wanted $25 to register. Sure, that's fine. Then a half hour later wanted another $20 for "parking and raffle" Nope. Not today Satan!
Very dissapointing, but there will be more. Got her all shined up and cleaned the interior anyways
PCA show & shine season is almost upon us! Paying to show your car has always been counter-intuitive to me, unless it's for charity. With all the Tennessee Carpokeans, I'm guessing you guys could have your own get together...
Lots of goings on in TN - Cars/Coffee, meets, etc. We had our Nashville area PCA's (Musik-Stadt) Concours today at 111 Motorcars in Franklin. A lot of nice cars but we could have used more transaxle participants... :angel:
Maybe I'll make it up to one soon! Nashville is about 3.5 hours from me, so it's a commitment.
There are definitely other meets and shows closer to me. Just have to start going.
'86 Zermatt Silver 944 N/A :thumbup:
'86 Mitsubishi Starion - Purpose built SM class Autocross car
'87 Chrysler Conquest - Mid LS Swap

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Loving this thread @PSU_Crash - thanks for sharing. I had to resolve many of the same issues when I got my n/a 944 at the start of the year, but nowhere near as challenging as yours! Amazing work to date.

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