More conversations with Jim Steck regarding Superchargers, EFI, & Twin Spark engines
(Non quoted portions are Jim Stecks comments)

(8/19/02)
'Would not external gearing (pulleys) make a big difference in how quickly a supercharger 'spools up' (puts out reasonably quickly more oomph than it takes away) - along with a waste-gate (blow-off valve - for when it becomes fully wound up) and wouldn't / couldn't it be made to make a fair amount of boost right from the git-go?"

There are two basic types of mechanically driven superchargers...positive displacement and centrifugal. The centrifugal is not well suited to street-driven cars with small engines. As Greg Hermann stated in digest #1036, 'their boost, after all, varies with the square of their rpm.' This means max boost at the redline only...if you want 8 psi maximum boost and consider 6500 RPM your redline, you would have only 2 psi boost at 3250 RPM...an increase in power of only 14%.

Several companies have designed systems to improve this condition. Studebaker used a mechanical variable speed drive on their Paxton supercharged engines, but the drives were very high maintenance...some would say "unreliable". In the Alfa GTA SA, the centrifugal superchargers were driven by hydraulic motors, powered by a variable displacement pump...probably more reliable, but more complicated and certainly more expensive. It's also less efficient...converting mechanical power to hydraulic power and back to mechanical power.

Boost control is generally not used on mechanically-driven superchargers. The output cannot be throttled without damaging the supercharger from over pressure or over temperature...it must be bypassed or recirculated. This is not something that can be done with a wet system...fuel added before the supercharger...and pressurized carburetors have their own problems...collapsed floats, regulating fuel pressure, hot fuel, etc. So, port fuel injection is the only reasonable approach.

Positive displacement superchargers are a much better match to the air requirements of a piston engine and can usually be matched in size and drive ratio to provide a very nice power curve without any auxiliary boost control. The usual method is to tune the basic engine for maximum torque at low RPM. Then at higher RPM's, the torque curve is pulled up by the increasing boost...producing a torque curve similar in shape to a normally aspirated engine, but higher all the way across.

"How sophisticated do the electronics need to be? Stock 'black boxes' make me very uncomfortable. Custom, one-off, insides known only to one person in the known universe scare the pee-pee out of me. How simple (as in it works really well and is still bullet-proof) can the EFI and if Really required, programmable ignition system be made?"

I only have personal experience with the Electromotive system. The TEC (Total Engine Control) integrates fuel and ignition and has been nearly bullet proof. I had a crank sensor fail because I didn't know how much the nose of the crank moved around...and the trigger wheel hit it ...and I've had one throttle position sensor (a General Motors part) that needed replaced after about 60,000 miles...internal diagnostics told me I had a failure. I've heard similar Testimonials for Haltech, Motec (expensive) and Autronic.

(from Greg Hermann)
"While you are at it, wide band O2 sensing gear is almost mandatory, EG Sensing and logging capability are very useful, and some sort o detonation detection system is also all but mandatory. All of these are very necessary during the tuning and 'set-up' phase, use of any of them on a "closed loop" basis during use / driving of the vehicle (such as is the case with "auto tune" ) is not all it is cracked up to be."

My experience here is different and may not be typical. The engines I've built with aftermarket EFI have been 'high RPM engines' with fairly large valve overlap. I've tried several different knock sensors, mounted them in several different locations and always have to ignore the signal above 5000 RPM...where the really destructive detonation occurs.The Alfa engine is noisey and fools the sensor at higher engine speeds. Since I've never detected any knock at low speeds, I have never been able to use this feature. My ignition curves are worked out on the dyno and have an appropriate safety factor.

As fas as 'closed loop' operation goes, I consider it essential, and have developed a tuning strategy that produces excellent power, good throttle response and good mixture control during part-throttle operation...this applies to unleaded fuel engines only. The fuel map is developed for maximum power...plus a small safety factor...and then the output from an O2 sensor is used to lean the mixture out during part-throttle operation. The Electromotive is designed to operate in 'closed loop' this way. Its 'auto tune' function is intended only for setup. It sounds like the Autronic 'auto tune' is also intended for setup only and not continuous closed loop operation.

Tuning these systems is not difficult. It may look overwhelming at first...the Electromotive system has over 400 variables...but the 'Tuning Wizard' will get you a basic calibration that will get you running...better than a lot of Weber conversions I've seen. Then you can then start fine tuning by pressing a few computer keys. You don't need a box of jets, or springs and weights, just a laptop...sorry Biba, you'll have to use a Windows machine.

(8/20/02)
Here are a couple photos from last year. Since appearance hasn't changed (except the color of the cam cover), they may fill your request.

On supercharged engines...I'm working on the design of a bolt-on supercharger kit using an Eaton M62 supercharger. If someone wants to deliver their car to me tomorrow, I'm ready to start installation.

The multiple engine maps are completely unnecessary...as the Electromotive system will adjust the fuel delivery to driving conditions based on feedback from an O2 sensor. I would develop a calibration that is optimised for performance in open loop, but would operate in closed loop until past half-throttle or high RPM. This strategy works very well for performance and drivability. Since we don't have annual emission testing in my county, I don't have numbers to fall back on, but believe I could make the system pass on almost any vintage Alfa...certainly on any Spica-equipped car. A limp-home mode is also part of the system.

A new stock clutch is capable 200+ Hp on a spider and 250+ on a Milano. A Milano transaxle would be advisable in an Alfetta. I've already produced similar cars, but with turbo superchargers instead of mechanical. The intake on the Eaton blower would not be difficult to design and build, and the power level would be easy to manage. The turbos produced a minimum of 275 Hp and were daily drivers...with occasional track use. After 60,000 miles, the end gap of the rings in my engine had only grown 0.002 inches. Brian's Alfetta hasn't been torn down, and my improved engine only has a couple thousand miles on it...the increased Hp was too much for the spider transmission.

An engine can always make more flywheel Hp with a turbo because of the mechanical losses in driving a blower, but an engine with a 50-60 Hp increase would be easy to build. The real problem with turbos is the exhaust syste...even stainless steel has to be considered temporary. You can expect some rebuilding every couple years. And the exhaust note doesn't sound as good...it's not crisp. To me, the sound of a supercharged small-bore engine is the best! And I like the whine of the blower.

(Continued on next column)

(8/24/02)
"Jim, don't suppose you'd care to give me an estimate as to how much you feel your Eaton supercharger / Electromotive package will go for - with and without engine rebuild?"

(The following has been removed at Jim Steck's request - see following).

"I'd like to either include this on my website or perhaps first pass it on to the Digest in general - if you have no objections. I'd also like to include your information regarding the rear brakes."

The brake kit is fully developed, and costs & performance known, but the details of building brackets, and intake for the building of a supercharged engine are still not fully worked out...I'm not ready to publish a cost estimate for a system. There are a lot of variations that could be made that would really affect costs.

"A couple of questions: If one used your transaxle rear brake system on an Alfetta, wouldn't the rears then do more braking than would be wise (brake bias wise)?"

Since the rotor diameter and caliper piston diameter are not changed, the brake bias does not change. The only thing the vented rotor does is keep the rotor temperature in it's designed operating temperature...stops it from overheating. There have been other discussions on the Digest about cooling the rear brakes on these cars...some suggesting that ducting more air to the rears should do the job. I've even seen a track car with squirrel-cage blowers mounted in the rear seat area blowing cockpit air directly on the calipers...it was an improvement, but not a complete solution.

The vented rotor is the air pump, and with roughly 3 times the surface area and more than twice the mass, it absorbs the brake energy better and gets rid of it much faster.They will easily keep up with the vented front rotors of the V-6 cars.

"On your supercharger system, would you use / recommend forged pistons, and if so, what compression ratio?"

Here is where the choices have to me made. Compression ratios from 8.5 to 7.0 would be used, depending on the boost/power desired. At the lower end of boost pressures and RPM, the stock Borgo pistons could be cut down...I think a 180 Hp engine could be built with stock rods and modified stock pistons. A good intercooler would help keep piston temperature down.

"How loud would you say the whine is? Ahmet emailed me and said before they installed a 'muffler' on his GTV's supercharger, it sounded like a 747 taking off. Afterwards, it was somewhat more bearable but still very loud. Doubt if that would thrill any potential clients I might have. Can one hear the engine over the supercharger whine, or does the whine pretty much become the 'engine' sound? Most of the cars I restore are for couples."

More horsepower will make more exhaust noise, but should be able to be muffled...another one of those 'unknowns' in building a supercharged car. The intake noise is another problem. I've driven a supercharged T'bird, and the noise was almost undetectable...but I don't know how extensive the work on the air cleaner / silencer is. Personally, I love the sound of the old superchaged Alfas, with all the gear and supercharge whine. The noise question can only be addressed after the first system is built...another reason I'm reluctant to quote any prices yet.

I'll be happy to discuss options with anyone interested in building one.

(8/24/02)
"Let me say that I'm somewhat curious as to the V6 'boys' search for more power, especially when in includes superchargers. The reason I began the entire (see above subject heading) was these were the 'items' I was interested in for cars which 4-cylinder's were originally supplied. Yes, I know, in Europe and elsewhere 'they / you' put 4-cylinder engines into just about anything.

"All I ask is don't say in your subject headings, " Was, etc." Then talk about turbos for V6's. Just talk amongst yourselves and leave us little guys who admit we have little guys and aren't afraid to admit it - though we would like to achieve a bit more potentiality from our undersized units. (I can hear the echos now, "Speak for yourself, Biba!)."

I think Mark Donohue had it about right when asked about the horsepower of the Turbo 917's...how much horsepower would be enough? Without looking up his exact words, he said something like ("When I have enough power to spin the tires all the way down the longest straight").

"Norm Riffle is going to put a TS head on his engine - I'm assuming pre-TS block. Please tell me if I'm wrong but heard the water passages don't line up all that well - perhaps other things. The only TS head I was up close and personal to was some years ago at Alfa Ricambi. The head seemed taller. A fair amount taller. Should this be the case, what happens if a Spider goes over a large pebble which hits the pan guard which pushes the engine up into the hood?"

The only difference between the TS block and the block of a Bosch-injected spider block is the length of the head studs. The water passages of the earlier blocks are different, but still compatible. And yes, the head is taller.

8/24/02
"The feeling I get is that Jim personally prefers superchargers, but admits that, 'An engine can always make more flywheel Hp with a turbo because of the mechanical losses in driving a blower, but an engine with a 50-60 Hp increase would be easy to build'."

I like the power I can get from a turbo, but the exhaust note and mechanical sounds from a supercharger...

"Wes Ingram shows the Electromotive ignition system set up for a 4-cylinder alfa engine on his website. He cleverly uses a Spica cover on which to mount the pick-up. Would be nice to have an ignition which is a really mount it and forget it type. Jim did have a problem with oneignition setup because he belatedly found that the front pulley had avery slight wobble. This surprises me after looking at Wes's as the pickup appears to be some distance away - but then, I don't know the complete story."

I guess I need to get a little more specific. When Electromotive first started manufacturing their Total Engine Control, the teeth on the trigger wheel were saw-tooth shaped...tapered leading edge and a vertical trailing edge. The recommended clearance to the magnetic pickup was .005-.007 inches. That seemed a little close, so I set mine at .010 inches...the wheel had no runout. At high engine speeds, flex in the crank, plus bearing clearance, and perhaps some movement of the timing cover allowed the trigger wheel and magnetic pickup to touch just slightly. That was enough to cause the pickup to fail. The replacement was installed at .015 inch clearance and I had no more problems.

Since then, Electromotive has changed to a square-tooth shape on the trigger wheel and recommended .020-.030 inch clearance...depending on wheel diameter. The Alfa 60-minus-2 tooth trigger wheel and Bosch pickup work fine with the Electromotive.

To contact Jim Steck

The following Bonneville photos have little to do with the above questions / comments,
but thought you might enjoy them.

 
The Besic's Series 4 Alfa Spider next to the Bank's record breaking streamliner.


Bonnie at the salt flats in 2001.

 
Bonnie's engine bay BEFORE (taken in 2001)


Bonnie's head AFTER (see below - taken in 2002)

 

 

8/16/02

At least we're in good company...Al Teague, in the Banks Engineering streamliner...retired today. His last run had a terminal speed of 410 mph.

We have the official G/BFMS...G (2.0 liter)/Blown, Fuel, Modified Sports record with a two way average of 203.15 mph.

The turbine housing that would make 24 psi boost on the dyno in Dayton could only spin fast enough to make 22 psi boost at the density altitude of Bonneville...average 6800 ft...where we needed 27 psi. In a attempt to break the 211 mph record in G/BGMS...G/Blown, Gas, Modified Sports...I flew in a smaller exhaust scroll. It probably would have done the job, but halfway through the middle timed mile we had a failure. I think we had a rod bearing failure that let the pistons hit the valves...and break them off. The number one rod broke at the big end and put a hole in both sides of the block. If you look closely, near the engine mount, you can see where the stiffening rib has cracked, and the piston cooling nozzle has been pushed out.

Last year I was disappointed that we didn't run for a record, or break trying...this year we did both. I'm happy!

Jim

  Steck Bonneville Supercharged Engine | Steck Turbo 2002 Bonneville Engine + TS Parts | Supercharged GTV
More Conversations With Jim Steck | Steck 4-Cylinder Engine Adapter

AlfaCyberSite Site Map  | ACS Accessory Parts Home Page
Alfa Spider Diagonal Seat Belt Info.

Cibie Home Page | Cibie Replacement Headlamps | Cibie Auxiliary Lighting Units: Rectangular | Round
 Talbot Mirror Home Page | Biba Restorations | ACS Home Page

 Copyright © 2002 - 2005, AlfaCyberSite.. All Rights Reserved.