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This weekend I bought a 93 Lightning with an SN2000 charger on it. This will be my first experience with a centrifugal supercharger. I've had a couple stock Eaton supercharged Fords, but this is a different game for sure. Admittedly it's not much, but from what I've read on this SN, it should have about 8 pounds out of the box. This one is showing about 3 pounds on my gauge, at WOT and redline. The charger is pulling air through the entire stock intake setup. I pulled the clothes dryer tube off the air box and got about 5.5 pounds, but it's probably not a good idea to run around w/o an air filter.
I guess my question is, does this sound right? I can't imagine this kit, installed correctly with the stock intake setup in place, only makes 3 pounds of boost. I'm sure there are two dozen things it could be, but any ideas would be very much appreciated. Also, if it does sound right, what can I do for more boost? Pulley, power pipe, XX trim Vortech?
If by pulling the stock airbox off the SN2000 intake side took your boost from 3psi to 5.5 then I think it's obvious the stock airbox may be proving to be a serious restriction.
You can remove the stock airbox and run a cone-style filter mounted directly to the blower. The cone filter that came with the SN-89 I have is a round/cylindrical K&N unit with a 3.375" (86mm) flange diameter, 4.375" (112mm) overall diameter, 4.6875" (120mm) filter length, and 0.8125" (20mm) flange length. Unfortunately, there's no model number on it and I can't seem to find it on K&N's website under their universal filters listing. I think this filter might have been a custom application.
However, almost any universal cylindrical/conical style filter with a 3.375" (86mm) inside flange diameter and a 0.625" (16mm) to 0.75" (19mm) flange length will work. Just make sure the overall length of the filter won't cause it to interfere with anything that might be located behind the blower itself (like the exhaust manifold, brake master cylinder, strut tower or tower brace, etc...) If you go to the K&N website and look under their universal filters listing, you'll find several cylindrical and conical shaped filters that will fit.
It might be important to mention, 5.5psi-6psi is actually a very normal level of boost for an SN2000; 8psi is a bit on the high-side and would typically only be seen if the blower is equipped with an H.O. impeller and if pullied to spin at upwards of 41,000rpm.
Wow! Thank you for all the info and good advice. Especially for a supercharger noob. :) I will work out something with the intake side, but there is not enough room to put a cone on the back of the head unit. Since I'm going to have to run an intake tube to a filter, will it be to my advantage to replace the stock Paxton clothes dryer tube with something smoother inside? Any suggestions on that?
That quick run with 5.5 pounds of boost was better than 3 pounds for sure, but a few more pounds would be even better. The motor will handle it without issue, but what's the best way to achieve it after I fix the intake side? Is the stock impeller maxed out? I've read that ~38000 rpm is about the limit of this charger. Would a smaller pulley exceed that limit? What figures must be calculated to find out the rpm?
Again, thank you for your previous help, and for your help with these new questions.
39000 is the limit but hear of some that have gone to 42000 RPM's.
The gear ratio is 4.44:1 in the SN head unit. Do the math with your pulley ratios of course at the engine and supercharger. There was a spreadsheet posted some time back but I don't remember where it is located.
I had a 93 lightning with a Powerdyne making 7.5psi. It was a fun truck. I moved the wiper/overflow tank to the fender. It just bolted right up, after removing the stock air box. That gave me clearance to run a 4" 180 degree elbow and a big cone filter. I'm not sure how the Paxton mounts up compared to the Powerdyne. Post some pictures of your setup.
Also, I max'd the blower RPM at my shift point. I think my Lightning always shifted at 5,000 rpm with the shift kit. So, pick a pulley combination that maxes out the blower at your shift point.
I'm almost certain both pulleys are what came with the charger. I have a stack of receipts that came with the truck, and new pulley receipts were not among them. If you need a more accurate measurement than that, just tell me how to measure the pulleys, and I'll do it. The motor is completely stock. Here are a few pictures I just took.
No, there's not much room, but I can fab something up that's more efficient than what's on there. Do I measure the pulley at it's largest diameter or where the belt rides? Will a tape measure work, or does it have to be a mic?
Here's a picture of the other end. I'm not sure what it is. I believe the second picture is the FMU, but I'm not sure about that either. I'm sorry about my ignorance, but I'm learning a lot here. :)
The one on the fire wall is definitely a FMU. The one next to the fuel rail kind of looks like a fuel pressure isolator, used to run a pressure gauge inside the cabin. However, the hose looks a little cracked and checked. With the engine under boost you could be up in the 75-90psi range on fuel pressure, you may want to address that hose for safety. Of course I’m just going off some pictures, perhaps its okay. When you remove the stock air box, that bracket for the Wiper/Overflow should turn 90 degrees to the fender side. It opens up a lot of area for a cone filter, plus there is an opening behind the grill for some fresh air.
Thank you! I'll check that hose as soon as I get home. I do have a fuel pressure gauge, but it's not working. Should I start at that isolator to try to get that fixed? I'll get that tank moved to the side too.
The isolator would be where I would look if the gauge is not working. Here's a link http://www.autometer.com/productPDF/1124.pdf to the instructions for the one I had, but mine was not blue in color, so yours could be a different brand. Or it may be for something else?
Wish I had pictures, but it was before the digital thing caught on.
I'm sure you're anxiously awaiting whether or not I've been under the hood of my truck yet. :) Well, I have been super busy at work the last couple days, so I haven't, but I will. I just wanted to say thank you again for all the advice, links, and general friendliness around here.
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