Chris' Automotive Tech Info & Links Page

5-18-2003: It fits! Click da picture to see how much I'm streeeeetching the definition of "fit".

This page documents my efforts to install a Sprintex S102 twin-screw (aka Lysholm) supercharger on a 1988 Nissan VG30E 3.0L V6 installed in a 1971 Datsun 510. Project challenges include: fitting the larger SC unit into a small engine bay, managing the high boost & resulting power output, & desiging a custom drive system from the ground up. The S102 supercharger is sized to deliver enough air mass to support approx 375hp at SC redline (12krpm). This configuration will require a 2:1 drive ratio & will generate approx 17psi of boost. My calculations suggest that 375hp is possible, but proper intercooling & anti-detonant (toluene or methanol) injection will be required to support 17psi. However, the SC & drive system will first be tested with a 1.45:1 drive ratio & a more conservative boost level of 4-6psi.

Ok... so it's been 3 months since I bothered to update this page... but that doesn't mean that I haven't accomplished anything. The stock VG30 has been running and functional for about 10 weeks & 2500 miles now. I'm still amazed by the low-end grunt that a stock VG30 has... there's nothing like being able to blow-away almost any other car in the road in 4th gear. That being said... I want to be able to smoke Vettes in 5th... and do it sideways with the tires smoking. :^) It's time to let the boost out of the bag.

When I bought this supercharger, I figured there was a 50/50 chance that it'd fit in the engine bay with the VG30 installed. As the conversion got underway, it became obvious that hood clearance was going to be the biggest problem. Sure, I could make it work with a hood scoop or bulge, but I also wanted to keep the SC low to for the sake of the center of gravity. After exhausting all possibilities of mounting the SC in a "normal" horizontal orientation, I tried flipping it 90 degrees. Much to my delight, I discovered a "3D" window of ~1/2" where the SC will sit square & not hit anything! My only concern was that the SC'd internal drive gears wouldn't be properly lubed w/ the sump rotated, but according to the S102 documentation, this won't be a problem.

After fine tuning the position, I whipped out the MIG and built a lower front mount out of 1/2" mild steel tubing. This first link runs from the a lower bolt in the front case of the SC to the first exhaust manifold stud. Since I have no way to precisely align the SC to the crank pulley (no belt yet), I made the lower link length adjustable w/ a threaded insert. I plan on doing this for the rest of the mounts. Speaking of which, I mapped out the location for three more links that will secure the SC to the engine. One from the top rear of the SC to the intake plenum, one from the top front of the SC case to the middle of the engine "V", and one from the lower rear SC case to the rear exhaust manifold stud. These 4 links should be more than adequate to withstand the forces from ~25hp of drive power (keep in mind 25hp @ 12krpm is only 11lb/ft). I'm actually more concerned with the vibrations & forces from the front end of the car as it gets hammered down the road. Weighing in at 35lbs, the S102 is a beefy unit and will require equally beefy mounts.

I also had a brainstorm on the belt tensioner plans. A 1/4"+ aluminum plate attached to front of the SC case by the 6 bolts around the drive flange will provide a great platform for the tensioner. For now, I plan on using a stock VG30E timing belt tensioner because I have several extras lying around. The SC belt speed will exceed the VG30's belt speed by about 50%... so I'll probably try to find a larger tensioner bearing.

1.45:1 Drive Ratio Calculations & Graphs (not finished, limited confidence in results) - Click for larger image.

Manufacturer	Sprintex, division of AEC Inc.
Model	S102
Displacement	~1100cc/rev
Type	Lysholm (screw) compressor
Internal Pressure Ratio	~1.3:1 (4psi @ 1 atm)
Max rpm	12,000 rpm
Lubrication	Rear bearings: Synthetic grease Front gears: 75-90W gear oil
Size (WxHxL)	8x6x16 (approx)
Weight	35lbs empty

Spring is nearly here & I'm ready to build another guinea pig for my engine management system development/tinkering... this time it's gonna be supercharged! Ever since I discovered that Roots blowers are only 40-60% efficient, I've stayed as far away from supercharging as possible. It seems... things have changed. The twin-screw (aka Lysholm) supercharger is finally becoming affordable. While companies like AutoRotor (Kenne Bell) & Whipple have been selling these for years, I've never seen one for less than $4k (kit). They still aren't cheap. I paid $830 for just the compressor (new) & Whipple is asking $1200-1400 for their ala carte medium sized screw jobs (w/o drive extensions). Allow me to explain why I elected to drop $830 on a supercharger when 6 mos ago I would've put the $$ toward a nice ball-bearing T4 turbo.

1. First and foremost, I'm an engineer and it bothers me to see wasted power... I can't help it. It's been beaten into my brain and I have no escape. I've stayed away from supercharging because roots blowers set off the efficiency alarm in my head. Click here for a a history lesson & brief rant on roots blowers. However, while reading of my many automotive tech books, I learned of a type of supercharger that can generate full boost by 1500rpm, has a adiabatic efficiency that rivals most turbochargers (~70%), & is capable of boosts in excess of 25psi. This is of course the Lysholm (or twin-screw) supercharger. When I learned about these compressors a couple years ago, they were far too expensive to me to rationalize buying one just to play with it. Now that manufacturing capabilities are catching up, it appears that the Lysholm supercharger is becoming affordable.

2. I own and drive a fairly quick turbocharged 240Z. While I love this car as a whole, I'm not 100% happy with the way it develops power. It simply isn't quick enough off the line. I want 300 wheel hp and I want it at 1500rpm (I need an excuse to finish developing my traction/launch control system). Considering I'm still running the stock turbo on the Z, any attempts to break into the 300hp territory are only going to hurt the 0-30mph performance (bigger turbine/compressor). While twin or sequential turbos are fine and great, lets not forget how much of a plumbing nightmare a typical single turbo installation is. I don't care if you have 3" aluminum tubing & silicone unions falling out of your ass... turbochargers are still a pain to duct (I'm thinking exhaust & oil lines here), and I'm really not motivated to double the trouble w/ another turbo.

3. Turbocharged Datsuns are fairly rare... but there still quite a few of them at Shasta every year. However, other than a few select Z cars, I don't know of any Datsun's w/ supercharged (Nissan) powerplants. I tend to anti-mainstream in everything I do... so it's only natural that I'd select the rarest & most expensive supercharger for my next project!

I will be dumping pictures and details here as I have time. Right now I'm collecting parts for a quick rebuild of the clean VG30 that will be the base for this endevor. The supercharger is due to arrive on the 11th. I'm working on the calculations for drive ratio and intercooling requirements. Oh, and I'm trying to get a better compressor map for my SC. If anybody has a map for a Sprintex S102... email me!

I tore into the engine today. This VG30 was ultra clean... I was told it had 112k on it, but there's no carbon build up in the heads (the rockers are still silver, not brown). It was either rebuilt at some point or the owner took really good care of it. Big thanks to Jeff Klein of Thumper Racing for finding this engine for me.

I tend to be a little anal when it comes to my engines, so I ripped the engine all the way down to the bearings to see what the rest of it looked like. Bores were awesome... no ridge & they still had the crosshatch marks. Sure enough of all the bearings, only one of the main shells had a scratch in it. The bottom end was probably good for another 112k. I'll pick up a set of bearings & moly-rings next week so I can complete the rebuild next weekend. I also noticed that this was a later VG30... it had the full-floating piston pins & the fuel cooled injectors. Exhaust studs also appeared to be the better ones... I didn't break any.

Super charger arrived today :^) It fits. Generated a huge spreadsheet to calculate boost using the flow/pressure ratio graphs that came with the SC.

Engine rebuild completed & car delivered to Thumper Racing for engine install & custom fabrication. Replaced everything but the rotating assembly. Used all my favorite parts, moly rings, King bearings, new Nissan timing belt, oil pump etc. I spent way more time/money on the build than I needed to, but I wanted this engine to be perfect. I did not put forged piston in this engine yet. I figure if/when I try to break into the 350hp territory, I can tear the engine down for an inspection and new pistons. I can't see ever needing more than 400hp from this engine.