"Not Made for Forced Induction"

[cafecito]

Admittedly I'm still a huge novice when it comes to the inner workings of ICEs, but I keep hearing/reading this phrase when researching adding a supercharger to my 3.6L.

Can someone ELI5 what exactly folks are referring to when they say this? What about the 392 makes it "made for forced induction" that the 3.6L lacks? Do superchargers really prematurely wear down engines that weren't "made for them"?

(And not to dissuade anyone from replying, but I know there are a ton of people who have supercharged their Pentastars with no issues. That's not what I'm asking. I want to know what people's reservations are from a mechanical/engineering perspective.)

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[Rattydude77]

My opion not as a mechanic but if you build any top half of a motor or super charge or even a turbo wouldn't you want to build the lower half maybe even a bigger cam

 

[sharpsicle]

It's kinda self explanatory. Some engines are built to be able to safely handle forced induction out of the box. Others are questionable. There are a lot of reasons one engine might do better with FI than another. It doesn't mean you can't do it, it just means forced induction wasn't an original consideration for that particular engine design.

 

[Orange01z28]

There's a ton of different variables from compression ratio, construction of internal parts (forged vs cast), block construction (open deck vs closed deck), ECU tuning, and even more

 

[cafecito]

There are a lot of reasons one engine might do better with FI than another.

This is what I'm asking. What is it specifically about the 3.6L that makes it not as well equipped to handle forced induction as another engine?

 

[P.Lo]

Petty's Garage in North Carolina puts Super Chargers on Jeep Wranglers and Gladiators all the time. Have not heard of any complaints or rebuilds from them.

 

[XraytecH]

At least for the Magnusen SC, depending on the model year and what month your JT was built will answer your question. Some time mid 2021 the PCM can not be reprogramed.

 

[staying_tuned]

This is what I'm asking. What is it specifically about the 3.6L that makes it not as well equipped to handle forced induction as another engine?

Loose tolerances, lack of forged internals, compression ratio, near black box ECU, not much interest and meager output to begin with. Stock dyno on the 3.6 at the wheel is incredibly low, slap a blower and tadaaaa you’re now as quick as most stock crossovers… Last but not least, an F/I solution already exists from the factory.

I was dead set on building a 3.6. Came on here with big plans, big indeed. Ended up with the EcoD and 35k miles later couldn’t be happier. Plenty of far more deserving platforms to throw time, money and boost at over the 3.6.

 

[Tbanks]

I got 3.6 Gladiator running Mag SC. Went from 210 wheel to 375 wheel. The nice thing about Magnuson SC, if you get it installed by certified install with their stock tune. They give you a 36k mile warranty on engine. My Jeep has run fine with no issues sofar.

What I wish I would of done was purchased a full built motor from Prodigy Performance and Turbo charged it. Their built motors with turbo are hitting 600whp and 11 sec 1/4 on jeeps. Which is crazy power and perfect for sand.

 

[jwolfejt]

Admittedly I'm still a huge novice when it comes to the inner workings of ICEs, but I keep hearing/reading this phrase when researching adding a supercharger to my 3.6L.

Can someone ELI5 what exactly folks are referring to when they say this? What about the 392 makes it "made for forced induction" that the 3.6L lacks? Do superchargers really prematurely wear down engines that weren't "made for them"?

(And not to dissuade anyone from replying, but I know there are a ton of people who have supercharged their Pentastars with no issues. That's not what I'm asking. I want to know what people's reservations are from a mechanical/engineering perspective.)

The 392 with boost is a ticking time bomb - anyone who told you this is talking out of the wrong hole. A 392 has really thin piston ring lands search the forums - lots of people blowing them up with relatively lower boost - infact i'd argue you can run more boost on a pentastar than the 392 - built for boost is a b.s. statement. Many engines can handle boost when "not built for it" - look at the Honda K series and many others. Shoot pentastars with a blower can make well north of 400whp on stock internals - thats pretty much doubling the stock output. Some engines can handle it better than others - but just about any engine can be adapted to handle it. Saab's B series engines were originally a triumph slant 4 that had absolutely 0 forced induction considerations on initial design - those engines can handle insane amounts of boost/power.... just food for thought.

 

[brianinca]

How about the stock block BMW 4 cylinders that went Formula 1 racing?

The 392 with boost is a ticking time bomb - anyone who told you this is talking out of the wrong hole. A 392 has really thin piston ring lands search the forums - lots of people blowing them up with relatively lower boost - infact i'd argue you can run more boost on a pentastar than the 392 - built for boost is a b.s. statement. Many engines can handle boost when "not built for it" - look at the Honda K series and many others. Shoot pentastars with a blower can make well north of 400whp on stock internals - thats pretty much doubling the stock output. Some engines can handle it better than others - but just about any engine can be adapted to handle it. Saab's B series engines were originally a triumph slant 4 that had absolutely 0 forced induction considerations on initial design - those engines can handle insane amounts of boost/power.... just food for thought.

 

[Pescatoral Pursuit]

Cast Pistons could be one reason. Insufficient rods, rod bolts, main caps/ bolts, another.
These are the components which would bear the brunt of higher cylinder pressures.
Crank bearing surfaces, bearings, crankshaft, cylinder heads/ bolts/ gaskets, also get honorable mention.

 

[jwolfejt]

How about the stock block BMW 4 cylinders that went Formula 1 racing?

Yes the M10 - they even used production blocks (not even new blocks) to go racing with and completely cleaned house - but it wasn't "built for forced induction" lol.

 

[jwolfejt]

Cast Pistons could be one reason. Insufficient rods, rod bolts, main caps/ bolts, another.
These are the components which would bear the brunt of higher cylinder pressures.
Crank bearing surfaces, bearings, crankshaft, cylinder heads/ bolts/ gaskets, also get honorable mention.

4G63's had cast pistons and IIRC cast rods..... they can make ridiculous amounts of power. Forged internals are definitely stronger - but not a hard requirement. Most of the forced induction versions of say the SR or 3SGTE use different oil pumps, water pumps and lower compression pistons - the rest of the parts usually remained the same internally (oh and different spec camshafts) - but they didn't cast a new block, new crankshaft, new rods etc ... built for forced induction is a stupid statement.

 

[DAVECS2]

Actually the short block on the pentastar is not bad. It is not gonna set any land speed records but it is fine for mild boost. If assembled correctly. I have seen many many overtorqued critical fasteners. Main caps, cam caps and so on.

The issue is the heads and control system.

This engine had variable cam timing and variable lift. On top of this it has individual cylinder fuel trims.

The cams change dynamic compression, if this is set wrong you can quickly elevate cylinder pressures to destruction.

To add to this if your cam phasers are not functioning as they are suppose to be (dirty, broke, weak solenoid) a slow positioning can also elevate pressures catastrophically.

That failure is actually pretty easy to catch but the most scary. Stock valve timing should never be used over 5 psi, NEVER.

Next is variable valve lift. You have 4 solenoids that close at 2800 rpm that shuts down an oil passage in the head that flows oil to the rockers that keeps them in low lift mode. If this solenoid gets dirty or clogged, or the follower to rocker arm interface leaks, then you get leak by and the low lift circuit does not shut off cause the highlift cam to run erratically causing unpredictable cylinder pressures and fueling. Usually not destructive but runs really bad and ultimately leads to cam failure.

The second most scary issue at least with the current supercharging options is injector trim and mappinng. The only legitimate going option right now are the GM 1000cc injectors. They work pretty well with the pentastar ECM, but they can cause some pretty critical failures.

If you are getting erratic fueling combined with misfires. The ECM will actually turn that cylinder off. When you have a flat cam it can cause the valve to stay shut to long and make bad cylinder forces.

The other failure is when using fuel cooling for detonation avoidance, at high RPM you can reach maximum duty cycle of the injector and hang it open, and fill the cylinder with fuel, that causes some pretty bad things to happen, including hydro locking or wash down and making the piston exit stage left.


So the rotating assembly pretty good. The heads and Control system not so much.

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