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Nix328ti · 09-01-2016, 04:14 PM

I did measure the cams and they do sort out at the expected duration/lift. The numbers I can't figure out without having them installed is the IO/IC and EO/EC numbers. Here's why that's important:

We just finished building a CHUMP car. Our M50TUB25 makes an advertised 189hp@5900/181lb/ft@3500. The thing is the M52B25 (basically the same concept, single VANOS) makes an advertised 168hp@5500/181lb/ft@3950.

The chip contributes to that but the cam timing also changed. This would be pretty much invisible if you just compared the duration numbers because they both run 228º/228º cams. BUT the timing is different:

The M50TUB25 works out like this:

Intake Duration is 228.00 degrees.
Exhaust Duration is 228.00 degrees.
Installed Intake Centerline is 110.00 degrees ATDC.
Installed Exhaust Centerline is 101.00 degrees BTDC.
LSA is 105.5 degrees
Overlap is 17.00 degrees.

The M52B25 looks like this:

Intake Duration is 228.00 degrees.
Exhaust Duration is 228.00 degrees.
Installed Intake Centerline is 110.00 degrees ATDC.
Installed Exhaust Centerline is 105.00 degrees BTDC.
LSA is 107.5 degrees
Overlap is 13.00 degrees.

You can see that the exhaust timing is phased for a much more sportier 105 LSA and an extra 4º of overlap as the base numbers. It would be interesting to see what the HP differences would be with a cam swap from M50 to M52...

I was also considering trying an intake cam swap from the M50TUB20 (Installed Intake Centerline is 105º vs. 110º) into the M50TUB25, effectively advancing the intake timing;

M50TUB20 Intake, M50TUB25 Exhaust:

Intake Duration is 228.00 degrees.
Exhaust Duration is 228.00 degrees.
Installed Intake Centerline is 105.00 degrees ATDC.
Installed Exhaust Centerline is 101.00 degrees BTDC.
LSA is 103.0 degrees
Overlap is 22.00 degrees.

Even sportier 103º LSA and a massive overlap difference (to the stock M52). Not great for street but it would be interesting to see how this might feel on track at high RPM and whether it would effect our lap times... This would be a viable stock sanctioned swap because the base numbers of 228º/228º @ 9mm lift is identical for all of these cams only the cam timing is different.

09-01-2016, 04:14 PM	#5
Nix328ti Member Join Date: Nov 2015 Location: Minnesota Posts: 32 iTrader: (0) Photo Gallery	Messing with numbers I did measure the cams and they do sort out at the expected duration/lift. The numbers I can't figure out without having them installed is the IO/IC and EO/EC numbers. Here's why that's important: We just finished building a CHUMP car. Our M50TUB25 makes an advertised 189hp@5900/181lb/ft@3500. The thing is the M52B25 (basically the same concept, single VANOS) makes an advertised 168hp@5500/181lb/ft@3950. The chip contributes to that but the cam timing also changed. This would be pretty much invisible if you just compared the duration numbers because they both run 228º/228º cams. BUT the timing is different: The M50TUB25 works out like this: Intake Duration is 228.00 degrees. Exhaust Duration is 228.00 degrees. Installed Intake Centerline is 110.00 degrees ATDC. Installed Exhaust Centerline is 101.00 degrees BTDC. LSA is 105.5 degrees Overlap is 17.00 degrees. The M52B25 looks like this: Intake Duration is 228.00 degrees. Exhaust Duration is 228.00 degrees. Installed Intake Centerline is 110.00 degrees ATDC. Installed Exhaust Centerline is 105.00 degrees BTDC. LSA is 107.5 degrees Overlap is 13.00 degrees. You can see that the exhaust timing is phased for a much more sportier 105 LSA and an extra 4º of overlap as the base numbers. It would be interesting to see what the HP differences would be with a cam swap from M50 to M52... I was also considering trying an intake cam swap from the M50TUB20 (Installed Intake Centerline is 105º vs. 110º) into the M50TUB25, effectively advancing the intake timing; M50TUB20 Intake, M50TUB25 Exhaust: Intake Duration is 228.00 degrees. Exhaust Duration is 228.00 degrees. Installed Intake Centerline is 105.00 degrees ATDC. Installed Exhaust Centerline is 101.00 degrees BTDC. LSA is 103.0 degrees Overlap is 22.00 degrees. Even sportier 103º LSA and a massive overlap difference (to the stock M52). Not great for street but it would be interesting to see how this might feel on track at high RPM and whether it would effect our lap times... This would be a viable stock sanctioned swap because the base numbers of 228º/228º @ 9mm lift is identical for all of these cams only the cam timing is different.