54mm Pulley for the Supercharger

[O-Gauge Steamer]

Firstly, the photos:

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Pulley is in. Had to shorten the existing bolt by 10mm as the new pulley is different.

Ever have to chase threads up the shank of a grade 12.9 bolt? Not all that fun as it turns out.

Results:

Boost is now a very solid 8 pounds. That would equate to 9.44 pounds at sea level. A slightly better than expected result.

Full boost point has dropped by about 800rpm.

So, that is that. Will be notifying Sprintex after closing this entry.

 

[CobraMarty]

So in the end, At your high altitude CO location,

Changing from a 58mm(2 1/4") to 54mm(2 1/8") SC pulley increased boost from 6.5-7pounds to 8pounds?

What did it do to the IATs going from 58mm to 54mm?

The increase boost will add about 7% more power but an increase in IAT of 50* will cause a loss of about 5%. Almost a case of diminishing returns. I wish you would have dyno tested before and after.

 

[O-Gauge Steamer]

Tell you what. You send me a 10mm x 1.5mm x 70mm SHCS and the cash for a pair of runs on the chassis dyno and maybe it can get done. Provided I can get out of the house.

I am disabled and retired as a result of the disability. Have been since '08... Copious amounts of cash are not my long suit any more. Not like when I was a working Engineer.

CM, Cite your source for the math used to calculate for the IAT increase.

Next time I have an opportunity to get out on the road, I will have the Kid monitor the IAT from the F/IC sensor. Now that the comm port has been improved over the quick and dirty version it started with, the laptop has a solid connection.

Going with used, on hand parts for the comm port compromised the connection. Replacing the port with an L-Com part resolved it. It is now possible to easily monitor both the stock IAT sensor (located in the compressor's intake manifold via the OBDII software I run) as well as the IAT in the Sprintex manifold via the AEM software.

The port now has a standard USB "B" female connection on the cabin side of the port and a standard USB "A" port on the F/IC side of the port. All it took was to heavily modify the switch bezel that holds the rear wiper, cigar lighter and that stuff. Filled in, cut out, filed and painted. In general, had a fun time getting the port to bolt in. But, the installation is now clean. One step closer to being able to sell the Jeep off.

If we look at what mod did what:

1) Replacing the stock TB with a 68mm F&B (their recommendation, btw) TB gave a gain of nearly 50%. Took the boost from 5ish pounds to 7.5ish pounds. The air here, being less dense, provides plenty of opportunity for variations in results. Pick a day, any day...
2) Replacing the stock 58mm pulley with a 54mm unit, increased boost by about 0.5 pounds. Again, varies by day. The mean air density here is sort of a joke for performance... Mostly, this mod dropped the peak boost point down by about 800 rpm or so. Drives easier...
3) Installation of a Header blanket and the insulation under the intake manifold provided a 20 degree drop in IAT.

So, the best bang for the buck is dumping the stock TB. I had a rather long discussion with the good folk at F&B and we decided that the 68mm was the way to go. Post installation vacuum testing (0"Hg with the 58mm pulley) has shown it to sufficient to the need. More would not help.

Keep in mind here that F&B supply the TBs for supercharger kit manufacturers as well as the performance oriented normally aspirated enthusiasts. They have a ton of experience on the subject. And, the cost of the TB was the same for either size so no imperative to sell me one over the other...

CM, please stop being imprecise. These pulleys are metric, not imperial in size. Believe it or not, folk here do know what a millimeter is... It is a thing I have admittedly. Call the metric parts metric.

 

[O-Gauge Steamer]

A quick update:

With the boost building at the lower engine speeds, the drivability is beyond a subtle difference. Being here, in the Springs, level roads are somewhat a rarity. So, it is up and down most of the time. What has been found is that the transmission (AW4) wants to be in OD, TC locked by 1500 rpm. This is just under 40 mph given my final gearing (4:56s and P285/75R16s). On a rise, it is making the better part of 3 pounds (2.5+) of boost at this engine speed.

May put the original pulley back in. Were this a manual transmission, there would be no issue at all. As it is, I find myself pulling the shifter out of the OD position and into third. Problem with that is that the transmission also unlocks the TC.

What I could use is full manual control over the box. That way, third gear with the TC locked would be a near perfect combination. Child9, are you out there?

The Jeep is a completely different beasty indeed.

As a side note, I recently "proved" out the measurement devices in the Jeep.
1) Replaced the 160 psi gauge on my compressors output regulator with a new, fresh out of the box, 60 psi unit (to gain resolution you see...).
2) Set the output of the regulator to 18psig.
3) Made a quick adapter to connect the compressor to the line providing the manifold pressure to both the F/IC and the boost gauge.
4) Took a reading of the current air pressure as reported by the F/IC. A nice 12.5 psia reading.
5) Connected the air line to the supply line and allowed the pressure to stabilize.
6) Read both the F/IC and the mechanical boost gauge.

Results:
1) The F/IC reported 30.5 psia.
2) Boost gauge reported 18 psig.

Why 18 psi? The boost gauge only reads to 20 psi. I figured it would be easier to read the error if the needle had "wiggle" room. Given that all three gauges (2 mechanical, 1 electronic) matched each other, the odds are that all of them are accurate. It takes three to confirm.

So, the system, as a unit, is accurate. At least, as far as I can test it with what I have on hand that is. Nice thing about this test was that the F/IC was quite happy to operate with the power delivered over the USB connection. Did not even need the keys...

Based off of these results, I can state that the Sprintex S5-210 compressor, connected to an engine displacing 4 liters, will supply a tad over (0.056 pounds calculated) 9 pounds of boost at sea level as long as the stock TB has been replaced. This is in accordance with the expectations Sprintex gave me at the outset of the experiment.