C43questions

I bought a cls550 a week back, already have a tuning bug. U think the m278 engine in this car can handle an e30 mix just as well as your c43 can? I really want the extra gains from running e85.

TwoC400s

I had been putting increasingly more E-85 in my tank over several months (my station actually tests and posts the ethanol content and it's consistently at or above 85%).

I had zero issues on the stage one EuroCharged (Houston) tune, but I tried turning up the boost by just 1.5psi in the upper revs (JB4 map 6) and I hit the fuel cut.

Currently in the process of getting flow-matched injectors, bored fuel rails, and hi-flow LPFP installed, and then on to the Spool HPFP.

TwoC400s

The problem is if you lean on that m278 too hard you're going to either scuff a cylinder wall, bend a connecting rod, or both.

MB2timer

A big problem with ethanol mixed with gasoline is moisture. More moisture is attracted and settle in fuel the higher the ethanol content. Also, the longer ethanol mixed gasoline sits and stagnates, the more moisture can form and precipitate. Water in a fuel system can cause corrosion, and possibly cavitation, which can add to or cause corrosion.

C43questions

so would aiming for e35 on a e30 tune be safer so I make sure I’m not running too lean ? How close can I get to e25 on a e30 too before the problems ur talking about could happen ?

C43questions

if I buy a ethanol analyzer with a fuel filter and make sure I’m always sitting around e30 shouldn’t I be ok ?

TwoC400s

Really has nothing to do with Ethanol vs normal gasoline.

The M278 and M157 motors have two connecting rods per crankshaft journal (and thus loose tolerances at that end of the rod). They have VERY tight tolerances inside the piston/wrist pin/rod interface. This is basically the opposite of most performance internal combustion engines.

When you try to push more power through these motors, they walk the big end of the rod on the crankshaft, and cant the piston sideways in the bore (which scores the bore and may eventually bend the rod).

C43questions

there’s dudes out here pushing over 800 hp with upgraded turbos that are doing fine. and ur telling me I’m going to have those issues just with a stage 1 e30 tune ?

MaverickC43

C43 with 800 hp, on just upgraded turbos?
stock internals?
I don’t know a ton, but I’ve read a bit
and I feel like that’s pretty high

C43questions

no I’m talking about e550s or cls550s on upgraded turbos

MaverickC43

Ok got it

TwoC400s

And there's plenty of people on stock tunes with bent rods and scored piston bores.

Sorry it's not what you want to hear, but it's a flawed engine design. I got VEEEERY close to buying a 2016 S63 coupe last year, but after doing more research on the engines, decided to just stay with my C400 for now.

If you want to build the motor with sleeves and rods knock yourself out.