Sprintex Supercharger hits 12 pounds Boost!!

I installed a smaller supercharger pulley. Went from a 2.5" pulley to a 2.125" pulley (2 1/2 to a 2 1/8 for those who don't like decimals. )
I now hit 8psi@1/4 throttle, 10psi@1/2, maxes out at 12psi. This was on a 50* night with no manual shifter shenanigans. Not even a hint of detonation. Only running 3* retard (at 6psi. no more retard after that) and 89octane (mid-grade) gas. No belt slip. IATs seem to max out at about 170* before they start to drop (gotta stay in boost longer to see how low they drop. Lmao). So.. To the people who said the SPRINTEX S5-210 was too small for the 4.0 engine.. IN YO FAYCE!!!
Video to follow.

You didn't quote me...

Anywho... BOOSTTTTTTTT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

i hope your camera is exagerating the sound.... **** driving around with that noise.

VAhasnoWAVES said:

i hope your camera is exagerating the sound.... **** driving around with that noise.

Click to expand...

agreed

VAhasnoWAVES said:

i hope your camera is exagerating the sound.... **** driving around with that noise.

Click to expand...

in4aride said:

agreed

Click to expand...

It is. Stupid cell phone... I'll make sure the GoPro is charged next time. :twak:

No detonation or 'pinging'.

Think about it, you can do a 'CPS mod' and add 6* advance with a stock 4.0 and no detonation. So it already had '6* timing retard' built in + an additional 3 degrees and fuel and water intercooling and good AFR's and no detonation.

What does 12 pounds boost really mean? That is the measurement of the pressure in the intake manifold, mind you it is really a 'measure of back pressure in the manifold'. With the 4.0L, the head and cam flow so little, so how much is really getting into the cylinder and raising cylinder pressures?

1-2 degrees is about right with no intercooler on a turbo.
What are your Intake Air Temps? (sorry to sound like a broken record about the IATs)

You need an intercooler or Meth injection. Less timing retard=More Power!

This keeps making me want to get a Sprintex instead of doing a custom setup.

A quick FYI then I'm out. At engine red line, the compressor will be turning 18,529.412rpm. Over the 16K Rpm maximum. Also, unless the cam is changed, to reduce valve overlap, the power is going to drop off at Rpm greater than 4,500. This is happening with the 3.8s and has been tracked directly to the cam timimg.

Yes, this can be done but it will kill the compressor.

For those who might be wondering, as delivered by Sprintex, the compressor runs at 15,750 Rpm. A margin of safety to ensure a 100,000 mile life span with oil changes every 30,000 miles.

Another fair warning is that you can not believe anything that Rick Rimmer may tell you. He has been dumped by Sprintex. He will say anything to sell anything.

Just because you can do something, it does not mean you should. The compressor will not turn into a grenade but, it will fail. So, fair warning and have fun.

Long time...
Your points are all well taken,
but when you 'Live on the Edge', 'Test the Boundaries', and 'Pushing the Limits' there is no room for being conservative.

Your pulley ratios and rpm's don't quite add up. What size crank pulley are you using for your calculations? What supercharger pulley size? What engine redline rpm are you using?

Sprintex rates the 210 to 15,000rpm continuous rating, IDK the maximum rpm they recommend for rare use 1-2 second bursts?
Stock Sprintex SC pulley is 2.5" and I installed a 2.125"
Stock Jeep crank pulley measures 6.0-6.4" depending who is measuring, top of or inside the grooves.

Step up ratio will be somewhere between 2.4-3.012 : 1.
Max rpm of the jeep is ?, my auto shift at 4900 rpm, and there is a harmonic issue at 5200-5400rpm.

According to my calculations 6.4" crank pulley / 2.125" sc pulley x 5200rpm = 15,661 rpm

I can't see how you get 18,529rpm? maybe at 6150 engine rpm? which is not the 4.0 redline.
I can't even see how you get 15,750rpm for the as delivered Sprintex.

Yes the high valve overlap of the stock cam will allow some of the charged intake to go out the exhaust but I would bet more of the power drop off over 4,500 rpm is due to the small stock TB. Using a 62 or better yet 68 or 70mm TB and a bored out supercharger intake manifold to match and free flowing air inlet tract, will allow more flow into the SC and not as much drop off in power above 4500 rpm. The 3.8's should be running a Viper TB and freer flowing intake tract which will help their problems.

CobraMarty said:

According to my calculations 6.4" crank pulley / 2.125" sc pulley x 5200rpm = 15,661 rpm

Click to expand...

I do not think you know what you have bolted to the crank. I'll give you a hint, at 5200 your Sprintex will be spinning 16079 rpm

There is a difference between knowingly exceeding specifications for no good reason and pushing the boundaries/breaking new ground.

One of them results in spending money on boring, predictable part failures, the other may result in learning something.

Talyn said:

I do not think you know what you have bolted to the crank. I'll give you a hint, at 5200 your Sprintex will be spinning 16079 rpm

Click to expand...

Is that to the bottow of the belt grooves or the top of the grooves?
6.57 vs 6.4
5200rpm, my auto shift at 4900 rpm and I never see 5200rpm.

I was pointing out your error, I don't give a crap what rpm you see or don't. If you want to throw numbers around at least get them correct.

I remeasured a new balancer-

6.24" diameter (19.625" circumference) measured at the bottom of the groove/rib.
6.52" diameter (21.5" circumference) measured at the top of the groove/rib.

6.38" average diameter. rounded to 6.4".

Talyn said:

I do not think you know what you have bolted to the crank. I'll give you a hint, at 5200 your Sprintex will be spinning 16079 rpm

Click to expand...

That gives 6.57" diameter, not what my balancer measures.

The ATI measures 6.570" Pulleys are measures from the outer rib, not the V. Being that you mentioned circumference it sounds like your using a tape measure of some sort. Try a set of calipers or better yet a micrometer.