Young Doc

First off let me say that this is the most beautiful car I have seen for the money. I am sure it has flaws like all cars but it looks very very nice and is almost deceptive. AMG looks, cool cross drilled rotors, good suspension and stance - If I saw it on the street I would think it is definately pricier than it is. Now let the modding begin!

I searched around and saw that since the 2005 motor is relatively new a lot of mods are still in the R&D stage. However I did not find anything in regards to porting the exhaust manifold. Here is why I think its a good idea:
1. It is not readily detectable by the dealer.
2. Its cheap - almost free
3. It can only help gas milage and the efficiency of the engine
4. Even if it only gives 4-5HP, thats okay because you are sacrificing nothing.
5. With an I-4 we have plenty of space (compared to V6/8's) to get that manifold out - plus we only have to port ONE, not two manifolds

Okay, I haven't seen this topic addressed before. Maybe it is because MB gasket matches their manifolds from the factory. If that is the case, then props to MB for good design and porting the manifolds would only give minimal gains. However with a ceramic coating we might still pick up 2-3 HP by keeping the gasses hotter and underhood temps down. Although this may not be cost effective as just plain gasket matching the manifold. Cheap, dealer friendly, and relatively easy. Somebody tell me why this isn't as feasable as I think it is. I am a newbie but I do know my way around an engine bay. Lets keep it a civil discourse.

Burnt Toast

its a good idea, i used gasket matched the headers on my nissan didnt feel any real perfomace increase but better flow is better flow. and its real easy to do with a air tools. it would be better to just extrude(sp) hone the manifold rahter then just gasketmatch it. you would see better gains. also.. im sure some one is going to make some aftermarket headers for this when that happends just get that and save the 2-3 hours you would spend gasket matching and porting.

A more benifical thing would be to gasket match and port the intake manifold.

Young Doc

Cool, its good to see some interest in this. I don't know anything about extrude honing - can you clue me in? I can see cleaning up the welds and perhaps the primary/collector junction on the stock manifolds and then finally gasket matching the primaries. That would take just a few hours and the dealer would never be the wiser.

Also porting and polishing the stock manifold would be a PITA right ? You would have to take the supercharger and IC off and that doesn't seem like an easy job. But while you had the blower off you might as well have a machine shop shave a half inch off the stock S/C pulley and get you some extra boost! Hell, just port the blower too!

MrSpace

I don't think you should be that worried about warranty

I have exhaust, dropped suspension, wheels, cats, headers, pulley and still warrantied

Sure if I run too lean and the engine blows, then they might put the blame on the mods, but they are not voiding my warranty of the mods aren't causing the defect.

Etienne

Young Doc

It really depends on the dealer. I made at least 500+ passes down the quarter mile strip in my last car that had mods out the a$$ - I ended up grenading the valvetrain on a misshift and the dealer paid for everything and even upgraded me to Z06 valvetrain as I paid the difference. HOWEVER - I suspect dealers vary widely in their mod friendliness. So its best to stay on the safe side. Attracting as little attention as possible. The stealthiness of porting and polishing manifilds would be a fringe benefit, the (slight?) performance gain would be the true allure of this mod. Anybody have any idea how much room for improvement we have on the stock manifolds? I am talking 2005+.

Burnt Toast

If I remember right the dealer can’t void your warranty for having aftermarket parts on your car. If they could they would seriously up charge (even more then they already do) on parts because people would be in fear they would void there warranty by having an aftermarket part. Originally the law was not intended to cover the aftermarket parts for performance gains, it was for regular stuff air filters (VW tried to void the warranty on MAF sensors if you did not have a stock VW air filter, claiming the cheap ones you buy at AutoZone and alike had to much oil on them and would cause the MAF to fail), struts/shocks, belts, ect... normal wear and tare stuff. But it’s a thin line from that to the hardcore performance parts. They can still void your warranty if they can prove the aftermarket part caused the damage, then it’s up to you to take it up with the aftermarket company for compensation.

Young Doc

Anybody here have any info on the stock manifolds, their flow or if there is room for improvement - or is this an area that has been pretty much left unexplored?

Young Doc

I see that there is not much info or people are not interested in this. I have no clue why. Anyhow - I might offer myself up as a guinea pig. Can someone out there give me the torque specs on the manifold bolts and downpipe? I want to take them off and put them back on properly. Maybe I can get some pics and do a write up for all you guys. Right now I am pretty busy with some neuro crap, but within the next 5 weeks I will work some time in to investigate this.

Here are my plans, please feel free to add to this list:
1. Scribe and gasket match the primaries
2. Smooth and clean welds/casting marks
3. Scribe and gasket match downpipe connection
4. Polish primaries.

respdoc

Feel free to try this but can tell for 4-5 hp the effort/time is not worth it...IMO..and is probably the reason for the lack of interest. The C's (C32/C55 excluded) are great cars for what they are but fast...without heavy mod's..is basically just wishful thinking...

Jim Banville

I think if you dyno your car, do the mode, dyno it again, and post the results, you'll gain interest. It's hard to get excited over something unproven.

Young Doc

Thats a good idea - but my car is coming in with 0 miles. Cars usually pick up some HP for the first 10,000 miles anyhow. So either I would have to wait about a year to do this or I won't have any dyno numbers. On my other car the ported manifolds were worth 15HP at the wheels, of course this was on a modified supercharged 3.8 V6 that made a lot more HP than the 1.8 to start with.

Porting the manifold WILL gain HP without expending too much effort. The big question is how well do the stock manifolds flow and how well they are gasket matched from the factory. 4-5 HP is a very very conservative number. If the manifold is cast like crap from the factory, 10+ HP is not out of the question.

Jim Banville

Well, take lots of pics and we'll all watch with interest