Celicasaur

If you have read this for the first time, how could you not have worked out that I've been trying to work out the reason for being down on power all this time

If anything I've been trying to hold off from fitting the headers until I'm satisfied that I've explored every other avenue.

I would agree that the fuel economy is a bit strange. But it also points to an exhaust restriction, thus the reason why the chambers don't need as much fuel as a car with a correctly or free-flowing exhaust system.

FWIW I'm not entirely convinced that a decat will solve my car issues entirely, as it doesn't explain why some people are down even without cats. We'll see how it goes I guess.

sirius9

Based on the MSL charts provided, it seems that your engine is down by about 40bhp using an 18% conversion of whp.

Not sure if this will help you or not, but my C63 was down by 20bhp pre tune and post tune, V5 Eurocharged map. This is despite a service and change of spark plugs etc etc. I was pretty cheesed off.

But then all was revealed when I had IPE headers installed and it made 552bhp on MSL's dyno and this was correlated with a slightly lower figure (as expected) on a Dyno Dynamics dyno. So, it seems that the headers on these M156 were restrictive and may affect each engine differently.

It could still be that once headers changed and cats delete (or sports cats installed), all may be resolved? which i sincerely hope so for you.

chrisridebike8

Omg. Another one of these?! So your car made the gains it was supposed to, meaning the post-tune dyno had enough gains over the baseline. That's all you can use for dyno numbers. For example, i made 380 whp baseline and then 425 whp tune only. If you made 370/415, then it's fine. You can't compare different cars on different dynos, only the gains on the same car and same dyno. So swtching to a different dyno and getting the numbers you want is worthless info without a baseline on that dyno too. That being said, when the OP was down 40 hp to similar cars ON THE SAME DYNO, he probably had a reason to believe he was down on power.

Bottom line: dynos only measure gains or are used for tuning.

sirius9

I am just trying to offer an opinion.
I agree that different dyno on different day gives different results.
What i was referring to was that post headers, bhp gain was around 50 rather than the expected 30-35. Which then conpensated for the presumably low figure on OEM headers.
Anyways, just hope OP has his sorted in the end.
Best of luck.

Celicasaur

Finally unwrapped my headers after having them dormant for months on end. Many thanks to mr747 for his help ... the man is a legend





3" outlet





Waiting on mandrel bends and x-pipe to arrive after xmas now. Hopefully have it all fitted in January and then I'll pop back for a retune.

Car is a little more enjoyable with the extra 20hp all over. Man, you lighter C class guys with strong power must be loving it!

Vladds

So what do you fuel over there, 98 RON?

Celicasaur

Indeed sir, that's correct ^

s.e.a.n.

Interested to see the gains from the decat and headers.