54mm Pulley for the Supercharger

[O-Gauge Steamer]

After a goodly amount of discussion with Sprintex Engineering, we have decided that a 54mm pulley will be fitted to my compressor as a test. Sprintex agreed to this modification after I demonstrated how I would prevent compressor over speed.

The F/IC8 has the ability to cut the fuel when the boost level gets to a point defined on the system setup page. Having looked at the commercially available Rev Limiters, all of them I found shut of the ignition leaving the fuel alone. IMO, a massive mistake as it allows unburnt fuel to accumulate everywhere. Bad for everything.

If by chance, anyone out there knows of a system that will cut the fuel, I am more than open to suggestions on that point.

Going from the stock 58mm pulley to this 54mm one should give me an approximate 7.5% (a 1.074074074074074:1 ratio, more or less...) compressor speed increase. What I am looking for is better boost at lower engine speeds. This should improve the drivability of the Heep.

Per my normal Due Diligence, I have spoken with Gates Rubber about the belt and they are of the opinion that 54mm is a good working minimum diameter for safe belt operation. Good to hear that as the Alternator's pulley is 54mm...

The pulley is on the way, shipped yesterday 7/11/13. Once it is here, it will need to be machined to fit the XJ kit. The pulley is from the JK kit and is slightly different. The offset dimension for the belt alignment do not match.

As this is a Factory Part, it has been hard anodized to prevent the premature failure of the pulley or the belt. Some aftermarket suppliers (think Rick Rimmer here...) usually do not bother with it and the pulleys/belts fail as a result.

As of now, the system produces 6.5 to 7 pounds of boost here at 6,000' altitude. A general rule of thumb has it that you lose 3% pressure for every 1,000' of altitude. This means I am losing about 18% of my system pressure due the being here. If this were at Sea Level, then it should produce 7.67 to 8.26 pounds of boost.

This is my starting configuration baseline.
The system is a stock Sprintex S5-210 compressor (58mm pulley) equipped with an F&B 68mm Throttle Body. Air cleaning is Spectre 4" discharge port open element filter connected the the TB by 3" hard line. One 90 degree Silicone elbow at the TB plus two 45 degree elbows. Zero inches of mercury intake restrictions for the plumbing.

Photos will follow.

Sure do wish I had a lathe in the garage...

 

[gradon]

Cool

 

[O-Gauge Steamer]

Stay tuned.

So to speak...

 

[O-Gauge Steamer]

Just a note here while we wait for the part to show. I do not expect any increase in the overall boost level of the compressor as it is already running nearly at it's rated capacity.

The experiment is to move the maximum boost production point down in order to improve low speed performance.

At engine redline (5,250rpm) the compressor is running at 14,626rpm with the stock 58mm pulley. The 54mm should move the compressor to 15,743rpm which is close to the rated 16,000 compressor red line.

To hold the compressor at it's current maximum speed would entail lowering the engine red line to 4,900rpm.

It will be interesting. Anyone in the Springs know of a good, reliable, machine shop?

 

[eflores]

I was of the idea that power loss was based on being naturally aspirated
My cummins made 40 psi of boost here and at sea level
While it did take longer to spool up it still made the same peak boost, torque and hp numbers

I mean if you're not maxing out the compressor you should be able to make the same boost at 6k ft as you do at 0ft

 

[eflores]

What kind of machine shop?
Block engine heads...Burt's on Colorado

Machining small parts
Paul at rocky mountain quality machining
Elpaso over by the dog track
He's the guy who maks bonez shackles and such

Pm me and I'll grab all his info

 

[cruiser54]

When I put the larger crankshaft drive pulley on my Miata, the boost came in sooner and was higher at redline also. Went from 8 to 9.75.

 

[O-Gauge Steamer]

eflores, PM sent, and thanks! I used Burts for block work like 40 years ago... That shop has been there since the dawn of time.

What is at issue here is the capacity of the compressor itself. Sprintex selected this compressor to intentionally limit the boost. It is actually rated for a 3.0L maximum engine. See the Sprintex web site for the performance curves.

This is OK with me as there is not an easy way to get an intercooler installed. No intercooler, better limit the boost. I have installed a header blanket and installed insulation under the manifold to help reduce the intake charge temperature. This mod allowed additional timing to be added back in. The addition of the oil/air separator also allowed additional timing to sneak back in.

Cruiser, installing the larger crank pulley is the similar to my installing the smaller compressor pulley. In both cases, the boost comes on faster. Your Miata has volume reserves available so it was able to make the additional pressure. Have to ask, was the pulley dedicated to the compressor or, is it a one belt installation like mine is. If it is a one belt, then all of the engine accessories are being overdriven as well.

So, we will see what happens. What we are talking about is a 1,117rpm increase. Or, the approximate 7.5% mentioned. If there were to be a pressure increase, it would be in the neighborhood of 0.25 to 0.5 pounds.

Truth be told, replacing the stock TB with the F&B 68mm gave a better response. That mod took the system from 5 pounds to the approximate 7 pounds it operates at now.

 

[cruiser54]

The belt ran just the SC. And, the M45 SC was a lower limit SC for it's application. The MP6w was a better match. You may be surprised at the additional boost you get.

 

[CobraMarty]

54mm/2 1/8" pulley has already been tried with the Sprintex 210 S/C.

You will be surprised at the additional boost generated, much more than the 0.25-0.5 pounds predicted. You can expect closer to 3+ pounds increase (with 70mmTB) but the altitude and 68mm TB may have a slight negative influence.

5 pounds to 6.5-7 pounds with a 68mmTB vs 62mmTB and a 58mm pulley, +2 pounds.
58mm to 54mm pulley, +3pounds boost increase and 50+ degree increase in intake charge air temps.

54mm will have 3:1 stepup (6.375"/2.125") and at 5000rpm, 15,000 s/c rpm and AW-4 shifts at 4800-4850rpm. Still less than the recommended 15,000rpm continuous limit and 16,000rpm peak limit.

Time will tell, Good luck.

 

[O-Gauge Steamer]

Pulley arrived yesterday. Pulled the existing 58mm today so as to be able to compare the two. Sprintex had warned me that there would be an offset issue to deal with and I have found it. In order to run the JK pulley on my XJ, I will need to have a spacer built that has an OD of 1.25", an ID of 0.786" and it need to be 0.064" thick. This will bring the belt alignment to where it should be.

Calling machine shops for quotes...

Pesky belts anyway...

 

[supertubesocks]

Make sure that your fuel cut takes place slightly after ignition cut and not before. Otherwise, you will go lean and detonate.

 

[CobraMarty]

Make sure that your fuel cut takes place slightly after ignition cut and not before. Otherwise, you will go lean and detonate.

This.

Never cut fuel as the only means of rev limiting in a boosted application.:explosion

 

[sidewaysstarion]

The starion uses fuel cut to protect the engine and that's been working pretty well since the 80's.

If you cut fuel, you will lean out, but it's lean to the point it doesn't ignite in a boosted application. No fuel, no fire, no detonation...

 

[CobraMarty]

It's the instant momentary 'lean out' that is the problem. Sure, once no fuel, no fire.

 

[O-Gauge Steamer]

So, here is the deal guys.

If you would like to open a thread on rev limiters, please do so. Do not hijack this thread for that discussion, OK? This thread is purposely limited to the pulley change.

What I will say on the subject is that boosted applications have used fuel cut off for decades.

Under a full boost condition, the bypass valve is closed. All of the air from the compressor is being consumed. There is no recirculation occurring, there is no fuel in the air stream. If the fuel is shut off, the engine dies. No detonation as there is zero fuel in the engine.

If you would care to test this, take your engine to redline and then attempt to exceed the 5250 rpm point. The Factory PCM shuts off the fuel. Listen for a ping.

There is no detonation. I have personally verified this with my Knock Detection System that I installed to aid tuning. IMO, for the best tuning results, a detection system is needed. THAT would be another thread.

Given that my hearing is pretty much shot, I needed the electronics to "hear" the detonations for me.

But again, discussion of rev limiters can overtake this thread and it needs to be separated out of this thread...

On the pulley, I am going to either have to purchase a tool or make one as the method used to hold the two pulleys whilst tightening them to the compressor are different. I will take photos and post so as to illuminate the point.

 

[CobraMarty]

That's cool, but in your opening post 2nd and 3rd lines, you bring up and ask about rev limiters.

Look forward to your pulley findings. Keep the testing coming.

 

[sidewaysstarion]

Well CobraMarty, if you want to discuss internal engine dynamics feel free to make a new thread and we can further discuss what causes detonation and why fuel cut isn't bad.

 

[O-Gauge Steamer]

Back on Subject...

After looking at Adjustable Pin Spanners online, I came to the conclusion that it would be in my best interests to just make the tool.

Taking a chunk (yes, that is a precision measurement, not to be confused with a tad or a bit) of 0.25" x 1.00" cold rolled steel strap, two holes were drilled/tapped to accept a pair of 3/8 shoulder bolts. The bolts were driven all the way to the shoulder and a little more to lock them into the holes. A pair of jam nuts (half height) were added and all of the excess material from the bolts (thread and shoulder/bolt head) was removed with an air cut off wheel. Final pin height was set with an angle grinder.

A third hole was drilled twixt the two for the allen wrench needed to secure the bolt in the pulley to the compressor drive extension. A bolt that will need to be replaced with a shorter one. Photos to follow will explain why that has to happen.

I figure that the tool cost basically, well, nothing as all of the materials needed were just gathering dust around the garage...

Saved about $100.00 in tool cost/shipping. The 3/8 bolts are not a perfect fit as the openings in the pulley are, of course, metric. But the bolts are within a few thousandths of the right size... Close counts here.

Yes, I am a Pack Rat. There are things around here I have been hanging onto for decades as you never know when you might need a left handed variable magnetic base dopticator. It would be a shame if I ever needed one after pitching the thing.

Anyone need a Muffler Bearing? Blinker Fluid? Might have some around here somewhere... Never know.

The strap? It is actually a leftover part from a garage door opener. The link that connected the opener drive to the door. It was replaced with the new opener and, of course, I kept anything from the old unit that looked like it may be usable in the future. Let's see now... Replaced the opener in '98... Not bad, only took 15 years to find a use for the material.

 

[O-Gauge Steamer]

Picked up the spacer today, an freezing the pulley now so that it will fit. Yes, it is a tight tolerance issue by design. Should be able to drop the space onto the pulley in the morning.

Photos will be taken when it comes apart the next time.