MAHLE 2.7 90 MM PISTONS AND CYLINDERS: EURO RS vs US CIS

CARRERIC · 07-14-2003, 02:30 PM

Two weeks ago I brought my car into Butch Stokes in Florida for a complete engine rebuild on my 2.7L. I would like to keep the car stock and reliable with minor upgrades.

I am trying to decide on the piston and would like to know the difference, and opinions on the Mahle 2.7 RS (euro) part#911 103 928 01 and the (US) CIS version part# 911 103 949 01? The price difference is only $50.

Also doe it pay to Port and Polish the heads?

THANKS
ERIC

Tim Walsh · Tim Walsh's Garage

do you want to run the CIS or carbs? I don't belive you can run stock CIS and the EURO (MFI) pistons

CARRERIC · 07-14-2003, 05:01 PM

Tim thnks, I'm going to run the cis.

724doorE · 07-14-2003, 05:01 PM

If you want to keep it down around 160 hp, keep the cis pistons. If you plan on some performance increases in the future, get the RS pistons. Honestly, I don't know why you would stay stock, you have no emmisions testing down there so Do the RS pistons and have your heads ported to 36 mm int and exh. Then get some early S cams and switch to Webers or become an mfi junkie!!

Joe911 · 07-14-2003, 05:21 PM

It is the overlap from the cams typically used with the RS pistons that would cause the majority of problems for the CIS. The air inversion during overlap upsets the CIS sensor plate. This crown of the CIS pistons were designed for additional swirl so the mix might not be quite as good with RS pistons (the CR is the same at 8.5 as I recall) - BUT you can always convert to E/S or solex cams and Webers if you are ever so moved. This would definitely bring it around.

If your engine is the 2.7S (now this is not like the early S), the ports are already about 35mm so no need there. If you have the non-S engine the ports are probably about 32mm so some opening would help but some lower end grunt would be lost. The ports themselves are so straight in no modification other than opening is needed. The cams that came with the 2.7S are very mild but the 2.7 was even more so you could exchange for them for the 2.7S cam for a small increase. Check the HP difference in Bruce A’s book or Wayne’s engine book for the HP difference. I think it is about 15 HP (ports and cam were the only difference I think). Plus I am sure you have already upgraded the exhaust which is also worth some additional HP.

CARRERIC · 07-15-2003, 06:15 PM

Thanks guys.. it is a 2.7S with upgrades including SSI's and pre74 muffler. One of the reasons I am staying with the CIS is for reliability. I plan to take some longer trips with my girlfriend. I also need the a/c in Florida and need the rear condensor.

I currently plan to port and polish the heads, and my shop also mentioned a mod to the intake runners.

I think the RS pistons will give me the availability to make more agressive mods in the future like cam and PMO's.