4.0L SOHC Supercharger Questions

[afgunn]

I hope we can make a “sticky” of this thread for other newbies like me!

I am interested in putting a supercharger on my 2011 Ranger XLT 4.0L SOHC, but I am a newbie with supercharging. I have now read several articles about how the 9.7:1 CR is too high for a supercharger, the pistons are weak, the connecting rods are weak and the head gasket may blow. I would like to avoid ALL of these problems by getting the information below on FULLY STOCK 4.0L SOHC engines.

I would like the following information or where I can find it:
Degree at which the intake valve closes ABDC (After Bottom Dead Center) on the stock 4.0L SOHC cam.
This is necessary to calculate the dynamic (or real) CR. And to be able to calculate the dynamic CR for the various boost levels with FULLY STOCK INTERNALS.

Running 3.5psi boost
How long have you been running with this boost level?
Are your engine INTERNALS FULLY STOCK?
Tuned, injectors or MAF?
Have you had any problems?
Have you made any changes?

Running 5.5psi boost
How long have you been running with this boost level?
Are your engine INTERNALS FULLY STOCK?
Tuned, injectors or MAF?
Have you had any problems?
Have you made any changes?

Running 7.5psi boost
How long have you been running with this boost level?
Are your engine INTERNALS FULLY STOCK?
Tuned, injectors or MAF?
Have you had any problems?
Have you made any changes?

Running 9.5 psi boost
I cannot see anyone running 9.5psi boost with the stock 9.7:1 CR. The dynamic CR would be over 12:1! Also, there is only a 4hp and 8lbft gain with stock internals from 7.5psi boost to 9.5psi boost. But, hey, if you are then:
How long have you been running with this boost level?
Are your engine INTERNALS FULLY STOCK?
Tuned, injectors or MAF?
Have you had any problems?
Have you made any changes?

Thanks in advance!

 

[Roert42]

Been running 3.5lbs for maybe 30 or 40k miles. No changes to the internals or computer.

No issues related to the supercharger. I have had to make a few custom parts and swap some things around to work better than designed. Nothing big.

I do run exclusively 93octane.

Been planning on installing a widening o2 at some point so I can have the engine tuned, or maybe do it myself.
Maybe some spray too.

Obviously not a priority.

 

[Blmpkn]

Been running 3.5lbs for maybe 30 or 40k miles. No changes to the internals or computer.

No issues related to the supercharger. I have had to make a few custom parts and swap some things around to work better than designed. Nothing big.

I do run exclusively 93octane.

Been planning on installing a widening o2 at some point so I can have the engine tuned, or maybe do it myself.
Maybe some spray too.

Obviously not a priority.

I keep forgetting your truck is cool and stuff...

...still expect a sweet burnout video too.

 

[afgunn]

Been running 3.5lbs for maybe 30 or 40k miles. No changes to the internals or computer.

No issues related to the supercharger. I have had to make a few custom parts and swap some things around to work better than designed. Nothing big.

I do run exclusively 93octane.

Been planning on installing a widening o2 at some point so I can have the engine tuned, or maybe do it myself.
Maybe some spray too.

Obviously not a priority.

Thanks, quite helpful! That many miles says a lot!

 

[rubydist]

I have the Moddbox kit on mine with a SCT tuner (I do the tuning myself, not something most people can do) and it runs as much as 7 psi, BUT I am at 5000'+ elevation, so it takes 2+ psi just to get back to sea level combustion pressures, and I don't run over 4 psi very often, and I have a meth injection set to come on at ~4 psi. (So, you should subtract 2 psi from my numbers if you are close to sea level to get a reasonable comparison.)

I have had it on for over 25k miles now and no issues at all. Here in CO, 91 octane is the best you can buy at the gas station and I use that exclusively, and nearly always use Shell so I know its good quality gas.

Fully stock engine had nearly 160k on it when I put on the blower. I drive about 25 miles each way to and from work, mostly freeway, and I drove the truck enough miles after I bought it to clean up the combustion chambers pretty well before the blower went on. I am still running stock heat range plugs because of the elevation and limited time at higher boosts. I always run Mobil1 oil and the insides of the engine look good (I had the passenger side valve cover off last fall when I thought I had broken a timing cassette, but it just needed the hydraulic tensioners replaced). The only modification I made to the kit was to change the egr valve to one with a better orientation of inlet.

If you read up on the guys who have done a lot of work on the 4.0 sohc engine (mostly in Mustangs) they will tell you that at some level of boost less than 10 psi you will take out the head gaskets because they are a bit shaky. I put the rpcaster kit on the 2003 FX4 that I had back in the early 2000s and put well over 75k miles on that with around 6psi boost max and had no issues, but life changed and I sold it, and I saw it for sale a few years later with blown head gaskets - but I have no idea what kind of use/misuse it lived through after I sold it. fwiw, the Moddbox kit is much better than the rpcaster kit, imho.

 

[Ljowanowitch]

I know this post is dead but in case other people want to reference the thread:
I run the 5.5lb pulley, I’ve been running it for 2 years now. I supercharged and tuned it at 160k and it just hit 200k this year. It still has fully stock internals, 47lb injectors, and a Maf from a 2010 mustang. This HAD to be tuned to run from the copious amounts of fuel and air it gets. I got it tuned at a mustang shop called McNews Automotive. I also strictly run 93 octane with a 180 thermostat and she never goes about 196 degrees (even at a 133mph)

I can’t say that I’ve had any “problems” like what you’re thinking. I BEAT THE TAR out of this thing every single day. I drive it how it was meant to and try to race literally anything that’s willing to play while driving to school and work everyday. As long as you look after it and keep up with the maintenance you’ll be fine.

Now I HAVE had issues with my clutch. Obviously making 100hp over stock will do that but I’ve had a string of bad luck with faulty slave cylinders. I just refuse to drop the trans to replace the clutch/slave cylinder every year so I float the gears until I can’t anymore. Currently in talks with a couple companies about making a clutch and slave cylinder since SPEC is the only company that supports the ranger and so far I’ve had bad experiences with them.(Last one lasted only a year and they refuse to respond when asked about any information on the clutch kit)

For changes, I’ve replaced the blow-off valve/hose with a hose you could hit a baseball with. HIGHLY RECOMMEND since it’s so hard to get to. I’ve also changed the intake when I put the new Maf in. It’s 3.5” piping since Moddbox said I’d be fine with the K&N stock intake I had. Was told at McNews that it was trying to suck air through a straw. I’m also replacing the transmission but it has 200k miles of some long, hard miles on it while floating the gears for a quarter of its life.