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    M156 Ported Cylinder Head Details and Dyno Gains

    http://www.mbworld.org/forums/c63-amg-w204/403501-race-ported-heads.html

    I saw a thread on MBW in which I wanted to answer but obviously couldn't so I thought I'd post the info here instead.

    Stock M156 Intake Manifold and Heads/Cams:

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    We did all the top end homework 2+ years go including cutting one side of one set of heads in half. I bought the first 2 sets in October 2008.

    Gains are +18rwhp/12rwtq SAE conservatively. The stock heads are that good, the casting quality is excellent, the port angles are damn near 45 degrees, the intake valves are 40mm, exhausts are 33mm and have a decent cut on them for an OEM head. They flow like nuts 390/330cfm out of the box and 420/365cfm after we hand race port them and put our own Serdi 5 angle valve job on them.

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    When you're talking about naturally aspirated power you're talking about VELOCITY and then flow. A sewer pipe will flow 5000cfm but won't make $#@! for power Click here to enlarge We spent 1.5 years prepping our ported heads using velocity probes and a flow bench, they are pure race cylinder heads ported by someone who's reguarly netted 233HP per Liter naturally aspirated (1.5L NHRA prostock bike motors 350HP from 1.5L N/A 2v SOHC spinning to 13,500rpm), no question about it.

    When porting it's the shape that matters, the surface doesn't have to be mirror smooth, that's just a selling point people fall into they see big and shiny and think it must flow a $#@! ton. In reality 30% of the gains from any modern 4v head when "porting" come from the valve job, as they (valve seats) are by far the most critical element of machining them as it's the choke point (greatest area of restriction) of any motor. A media blasted pitted port will flow just as well as a mirror smooth one. There are arguments back and forth but facts are facts, it's not the texture it's the shape and eliminating mass production typical flaws, plus knowledge learned over 30 years of porting 4v heads.

    Also the intake manifold is half Mg half plastic, the shape, cross sectional area, volume, and shape are PERFECT you cannot improve on the intake whatsoever, period. I bought one of those too as you can see, along with stock cams and we are still the only ones in the world that even know what the stock cam specs are. You can't extrude hone plastic and Mg and you should NEVER extrude hone to port anything. Why? Because extrude honing removes the same amount of material from every surface the media comes in contact with. When porting you want to remove material in some areas and absolutely not touch or even add to material (via weld or in competition heads even epoxy) in others.

    Gasket matching is the absolute WORST thing you can ever do to a set of heads or an intake manifold, remember this: "Gaskets are for Sealing not for Porting". Click here to enlarge

    Hog the ports out to the gaskets and your car will lift it's leg to piss until 6000rpm+. Velocity, velocity, velocity. Ever see the ports on a Ferrari? They are tiny compared to what most would think.

    If anyone has any questions about M156 heads, M159 heads or cylinder heads in general fire away.
    Last edited by MHP LLC; 06-10-2011 at 08:27 PM.

  2. #2
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    Excellent post! Port velocity is key and you explained very well. Honest about the stock heads and gains too.

    Great job!

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    For a while there I thought you were asking a question about heads for the M156 and thought, wtf?

    Great thread, going to edit the title a bit!

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    Great thread Andy. You knowledge is well appreciated Thank for the write up.

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    Excellent write up Andy.

    Great info.Click here to enlarge
    2012 CTS V - Sedan - 6AT

    Stage 1 Mods:
    - 2.5 upper pulley, Ported snout/throttle body, Fluidyne HX, Airaid CAI w/green filter, ID850 injectors

    Stage 2 Mods:
    - American Racing Headers w/X-pipe, 9.1 Lower Pulley, Tune Time Custom Cam, Moroso Dual Catch Cans, Zl1 Lid, Norcal Tank

    Stage 3 Mods:
    - LSA ported/polished heads, 4.5" G-Force intake, Nick Williams 102mm T-body, 8.6 Lower Pulley

    12.18 @ 118.98 - STOCK
    10.87 @ 127.02 - STAGE 1
    10.53 @ 131.31 - STAGE 2
    10.47 @ 133.20 - STAGE 3

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    Great thread and very valuable info.... Click here to enlarge

    Does porting of the heads require a tune to get the 18 rwhp gain or are those gains without a tune?
    2007 E63 P30
    Click here to enlarge

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    Interesting read. I remember an older theory that you done want the intake mirror finished as it does not aid atomization but you did want the exhaust ports as smooth as possible.

    Weistec is buttoning my engine back up this week. Will be interesting to see how their gains as a percentage on a blown application compare to your NA gains.

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    Click here to enlarge Originally Posted by ecampbell Click here to enlarge
    Weistec is buttoning my engine back up this week. Will be interesting to see how their gains as a percentage on a blown application compare to your NA gains.
    What changes were made? Heads?

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    1 out of 1 members liked this post. Reputation: Yes | No
    I don't want to hijack this thread so will start another...

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    Click here to enlarge Originally Posted by ecampbell Click here to enlarge
    I don't want to hijack this thread so will start another...
    Wise and appreciated.

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    Great thread!.

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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    For a while there I thought you were asking a question about heads for the M156 and thought, wtf?

    Great thread, going to edit the title a bit!
    Thanks Joe!

    Click here to enlarge Originally Posted by PetroC63 Click here to enlarge
    Excellent write up Andy.

    Great info.Click here to enlarge
    Thanks Mike! Get 'em on yet? Click here to enlarge

    Click here to enlarge Originally Posted by Exeenom Click here to enlarge
    Great thread and very valuable info.... Click here to enlarge

    Does porting of the heads require a tune to get the 18 rwhp gain or are those gains without a tune?
    Thanks Mo! Yes extra fuel is needed to bring it to the safe WOT A/F (what we consider to be safe) or else the gains would be a bit higher, 18rwhp is what you get with a nice safe A/F curve.

    Click here to enlarge Originally Posted by ecampbell Click here to enlarge
    Interesting read. I remember an older theory that you done want the intake mirror finished as it does not aid atomization but you did want the exhaust ports as smooth as possible.

    Weistec is buttoning my engine back up this week. Will be interesting to see how their gains as a percentage on a blown application compare to your NA gains.
    It seems everyone and their mother has written a book on cylinder head porting, some like Dave Vizard even go so far as to say one intake vave (of a 4v) should be larger than the other, etc etc.

    The bottom line when it comes to porting is it's contour and shape that matter most, a killer VJ will top it off and gain everytime. Otherwise a pitted port literally flows just as much air (volume) with just as much port speed (velocity) as a polished port, all else equal. We've tested it ourselves countless times. Some attribute it to the golfball "dimple" affect where the dimples hold air in place around the ball so the only friction is air on air vs air on ball which would be greater. IMO when the air starts going supersonic it doesn't really give a $#@!.

    As for gains with your blower, traditionally head porting when paired with a positive displacement blower won't gain much if anything simply because the blower is supplying the mass of air and velocity. Given this instance where the heads flow so well to begin with I'd bet your gains will be in the 20-25hp neighborhood, my WAG anyway. Best of luck and keep us posted.

    Click here to enlarge Originally Posted by ecampbell Click here to enlarge
    I don't want to hijack this thread so will start another...
    Thanks, you can digress fwiw as long as it stays technical I don't care.

    Look forward to reading your thread

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    Awesome write-up, Andy. I really enjoyed the read. And learned some new technical info.

    Quick question, given AMG's alleged complete control over the M156 engine's design, and the fact that they really seemed to build the motor purely for performance, why do you think they didn't port the heads further? I mean, why didn't they want to pickup that extra gain when they easily could have given how nioce a job they did on the heads and intake manifold to begin with. As you said, the intake manifold is perfect. Why didn't they take the heads to that level?

    I'm not trying to put you on the spot. Just wondering if maybe you noticed some things when the heads were apart and in your R&D that perhaps gave you an idea why AMG stopped where they did.

    Could it have to do with the increased fuel demand (which decreases mpg) that you noted due to the increased air flow? And even though the engine is built for performance, the engine is placed in a road car.

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    Click here to enlarge Originally Posted by Sonny Click here to enlarge
    Quick question, given AMG's alleged complete control over the M156 engine's design, and the fact that they really seemed to build the motor purely for performance, why do you think they didn't port the heads further? I mean, why didn't they want to pickup that extra gain when they easily could have given how nioce a job they did on the heads and intake manifold to begin with. As you said, the intake manifold is perfect. Why didn't they take the heads to that level?
    Likely cost and that they didn't need to. The motor had enough displacement and revs they didn't need to squeeze out every last horse.

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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    Likely cost and that they didn't need to. The motor had enough displacement and revs they didn't need to squeeze out every last horse.
    I see. It is interesting, though, that they really did engineer many of the powertrain parts (except for the trans) to make near max power. They really went for it. haha

    Hey, it got em' Engine of the Year a couple times.

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    Click here to enlarge Originally Posted by Sonny Click here to enlarge
    I see. It is interesting, though, that they really did engineer many of the powertrain parts (except for the trans) to make near max power. They really went for it. haha

    Hey, it got em' Engine of the Year a couple times.
    That it did but also keep in mind the motor was aimed at the BMW V10 and to replace the 55. It did the job in both respects so they didn't need to make it as high strung and left more room on the table on NA form. Kind of like the Z06 in a way, they could put out more power if they wanted to.

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    Click here to enlarge Originally Posted by Sonny Click here to enlarge
    Awesome write-up, Andy. I really enjoyed the read. And learned some new technical info.

    Quick question, given AMG's alleged complete control over the M156 engine's design, and the fact that they really seemed to build the motor purely for performance, why do you think they didn't port the heads further? I mean, why didn't they want to pickup that extra gain when they easily could have given how nioce a job they did on the heads and intake manifold to begin with. As you said, the intake manifold is perfect. Why didn't they take the heads to that level?

    I'm not trying to put you on the spot. Just wondering if maybe you noticed some things when the heads were apart and in your R&D that perhaps gave you an idea why AMG stopped where they did.

    Could it have to do with the increased fuel demand (which decreases mpg) that you noted due to the increased air flow? And even though the engine is built for performance, the engine is placed in a road car.
    Jacob,

    Sticky touched on a lot of what I was going to say. Ultimate reason the castings are good enough as is is cost/time. With 380 inches and a motor "only" revving to 7000rpm (trans limited) they are pretty insane. To squeeze those 18rwhp out of the heads takes a good 40hrs of hand work performed by someone with decades of experience porting race quality OHC heads.

    S85 V10 heads are factory CNC ported and with a 1.2L displacement disadvantage the extra static C/R (12.0:1 vs 11.3:1), piezo vs PFI, quasi dry sump vs wet sump oiling, and ability to rev to 8450rpm post tune etc make the S85 a more efficient engine (the smaller the engine the inherently more efficient it is but this goes beyond thats) but when properly uncorked the M156s remind me of the LS1 vs B/C Head 4v 4.6 Ford Modulars, you just can't beat the inches. I would rate the MB M156 top end a 8.5-9.0 (not a solid 9 due to TB placement which among other things are addressed in the M159 which is in another league stock vs stock) and the S85 a 10/10 FWIW. Stick 8 individual TBs directly onto factory ported cylinder heads on a M156 and it would be game over.

    The limiting factor in all M156 equipped vehicles isn't the engine, it's the Torque Converter and 7G trans behind it. The motor can handle 8000rpm as is (would need different cams to make power that high but all else is ready including valvesprings/VT) the trans can't simple as that. The flipside of that equation is if you were to install a SMG from a S85 car onto a M156 it would shred it to death along with the clutch in minutes. You have to pick rpm or torque, unless of course you drive a Veyron and have the world's strongest DCT.

    Porting heads or anything (including slapping on Longtubes, airboxes, tuning, etc) you do to make more HP/TQ at WOT also makes your car more efficient at part throttle. The less restriction the engine (air pump) sees the more efficient it becomes.


    Thanks

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    Click here to enlarge Originally Posted by MHP LLC Click here to enlarge
    The flipside of that equation is if you were to install a SMG from a S85 car onto a M156 it would shred it to death along with the clutch in minutes.
    True in stock form, but the SMG is easier to upgrade with a higher capacity clutch. It isn't limited like the M156 based cars.

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    Click here to enlarge Originally Posted by MHP LLC Click here to enlarge
    Jacob,

    Sticky touched on a lot of what I was going to say. Ultimate reason the castings are good enough as is is cost/time. With 380 inches and a motor "only" revving to 7000rpm (trans limited) they are pretty insane. To squeeze those 18rwhp out of the heads takes a good 40hrs of hand work performed by someone with decades of experience porting race quality OHC heads.

    S85 V10 heads are factory CNC ported and with a 1.2L displacement disadvantage the extra static C/R (12.0:1 vs 11.3:1), piezo vs PFI, quasi dry sump vs wet sump oiling, and ability to rev to 8450rpm post tune etc make the S85 a more efficient engine (the smaller the engine the inherently more efficient it is but this goes beyond thats) but when properly uncorked the M156s remind me of the LS1 vs B/C Head 4v 4.6 Ford Modulars, you just can't beat the inches. I would rate the MB M156 top end a 8.5-9.0 (not a solid 9 due to TB placement which among other things are addressed in the M159 which is in another league stock vs stock) and the S85 a 10/10 FWIW. Stick 8 individual TBs directly onto factory ported cylinder heads on a M156 and it would be game over.

    The limiting factor in all M156 equipped vehicles isn't the engine, it's the Torque Converter and 7G trans behind it. The motor can handle 8000rpm as is (would need different cams to make power that high but all else is ready including valvesprings/VT) the trans can't simple as that. The flipside of that equation is if you were to install a SMG from a S85 car onto a M156 it would shred it to death along with the clutch in minutes. You have to pick rpm or torque, unless of course you drive a Veyron and have the world's strongest DCT.

    Porting heads or anything (including slapping on Longtubes, airboxes, tuning, etc) you do to make more HP/TQ at WOT also makes your car more efficient at part throttle. The less restriction the engine (air pump) sees the more efficient it becomes.


    Thanks
    Andy, thank you!

    Loved reading your reponse. It was VERY informative and helpful.

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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    True in stock form, but the SMG is easier to upgrade with a higher capacity clutch. It isn't limited like the M156 based cars.
    Potentially true. Same goes for a "built" 7G if it ever happens and as we all know that's a different story altogether.

    Jacob, my pleasure!

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    Can you guys start speaking English isn't this a US based forum
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    Drives: Basically a pretty bad ass f250 lifted with 24" wheels! Dpf delete 4" exhaust h&s tuner and intake..

  22. #22
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    Click here to enlarge Originally Posted by Dodger63 Click here to enlarge
    Can you guys start speaking English isn't this a US based forum
    Did you mean to post this in another thread?

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