Bare Posted June 19, 2003 Share Posted June 19, 2003 Somewhere in one of my Alfa books there is a description and photos of a mid/late 60's Alfa GTA Development Vehicle, Factory fitted with twin Superchargers/Compressor turbines driven Hydraulically by an engine mounted Hydraulic pump.. Claims were that it worked, producing in excess of 200hp and presumably an equal amount of Torque. Tellingly this was a one off.. perhaps Typical of Alfa, but perhaps also because it was a dead end notion ;-) Not too many years ago Ferrari also fitted an exhaust driven Supercharger (not technically a turbo) they called Comprex..into their F1 efforts.. the experiment apparently worked, it lasted about a season if memory serves (surely there is documentation if one searches) reputedly sounded much like a Siren as well. Link to comment Share on other sites More sharing options...
Foxy Smith Posted June 20, 2003 Share Posted June 20, 2003 The Comprex is/was quite an interesting device. Strictly speaking its a pressure wave supercharger. It has a rotor driven by the engine crankshaft as per superchargers but also uses exhaust gas to compress the induction charge. This allows it to be efficent at low engine RPM. Somehow the compressing exhaust gas manages not to mix or heat the induction charge and is scavenged prior to the induction charge being admitted to the cylinder. Used on lorry diesel engines and as Bare said on Ferrari formula 1 engine way back when. Mid 80's?? Link to comment Share on other sites More sharing options...
Trevor Phillips Posted June 20, 2003 Share Posted June 20, 2003 Ricardo have some development superchargers available from the Mini Cooper S project. Racing pics and items for sale here Link to comment Share on other sites More sharing options...
scooby dooby doo Posted June 20, 2003 Share Posted June 20, 2003 Alex - you've not even fitted those new cams yet have you 🤔 They'll get you from 110 to 135 bhp, now you're taking about 250 ❗ HOOPY R706KGU Hoopylight R Link to comment Share on other sites More sharing options...
V7 SLR Posted June 20, 2003 Share Posted June 20, 2003 so what was wrong with the TurboTechnics supercharger again?Nothing wrong with it, but unlike a "proper" s/c its pressure output rises with engine speed whereas most s/cs provide full pressure at low revs. Although this requires a limiting valve, you do get the opportunity to map with max pressure available from typically 2500 rpm, therefore generating a pretty flat torque curve. Probably not much point having more than 3 gears though. Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
Peter Carmichael Posted June 20, 2003 Share Posted June 20, 2003 There have been some fascinating developments and examples of ingenuity. Haven't the different developments served different requirements? Drivability vs. power etc. If the common cause of forced induction is to use some energy to gather more capability for generating energy it becomes a matter of choice of where to obtain the "spare" energy and then how to distribute its use to achieve the best serving of the requirement: drivability or power. For instance: A turbo uses "waste" low grade (thermodynamically it is depleted having already being expanded pushing against a piston) energy in the exhaust to boost the intake. The capture of spare energy and its deployment are inextricably inter-related so the issues become ones of suiting the turbo installation to the application to get the right balance of lag/power/mid range surge/fuel consumption etc. The trade off is that the energy production process has to be made less efficient to extract the waste energy in the first place (exhaust port back pressure). Another case: Crank driven supercharger. You now have less variable control of the input as it depends purely on crank rpm rather than a mixture of crank rpm and the throttle opening of the last few instances. Power is extracted from the crank directly, so it is a very efficient capture of the energy required to compress the inlet charge. The electric driven approach requires the conversion of crank energy into electrical energy in the alternator and then the deployment of that electrical energy via a control system. The collection of the energy and the deployment of it are decoupled so you can correct driveability issues and achieve boost throughout a rev range. You can develop strategies to handle full throttle differently to cruise. The process of collecting/storing/deploying the electrical energy is less efficient than direct drive, so the overall effect will be the inclusion of heavier components - alternator battery - and more net loss of power at the crankshaft as it has to cope with alternator and motor inefficiencies. Doesn't the electric driven approach aim for more in terms of "usability" in direct compromise of principles at the heart of "Seven-ness" - simplicity, lightweight, efficiency compromise in favour of performance. Consider that the derided E-Ram deploys 700 watts and that isn't enough. 750 watts would be 1 hp. Admittedly we don't want full boost all the time, so there is a duty cycle where the charging system gets a chance to catch up, so the demand for more than 1hp in forced induction input would be spread over the duty cycle. The 700 watts gave 1psi of boost at somewhere close to the 10,000 revs demand of a 2 litre engine (back of envelope calculation). This sounds to me like it is about 10% of the sort of serious full boost requirement Seven owners would be looking for. Model it against a 10% duty cycle for road use and we are back to 700 watts continuous from the charging system. 50 amps at all times at 14 volts, with a battery capable of delivering 500amps during its 10% on-cycle. This might be sufficient for road use, but if you went on track and the duty cycle rose to 60%, the demand might be for 300amps continuous charging. All very speculative and I'm sure there are assumptions in there that the experts can knock holes in, but I thought it worth pointing out that "you will need a bigger alternator". Now if the objective was to get a spread of power that enabled you to eliminate the gearbox then you would have 35kg to play with. Question is whether you could pare down an AMG 5.5 supercharged engine to within 35 kilos of a K-series. I reckon you could run one of those without a gearbox in a Seven as long as you had a good clutch. Just blathering. Ignore to taste... Edited by - Peter Carmichael on 20 Jun 2003 13:26:28 Link to comment Share on other sites More sharing options...
V7 SLR Posted June 20, 2003 Share Posted June 20, 2003 Interesting points... and the last line's a killer. My "preference" is for a sprintex-type jobbie because it generates the chrarteristics I like in bigger cars (lot of torque at low revs). Not sure I'd actually want that in a Se7en. The fact that a Sprintex actually wastes energy (you have to limit the pressure as revs rise by bleeding off the excess) means it probably isn't as energy efficient as the TT belt-driven turbo. Also the latter is small and ought to be easier to site. Whatever... I'll have a look at other people's implementations and have a go myself one day. Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
Joe 90 Posted June 20, 2003 Share Posted June 20, 2003 The key to the electrically driven supercharger is finding a sufficiently powerful motor and the electrical energy to drive it, which definitely means a more substantial alterantor, i.e. 100 amps or so. The question this leads to is "Why bother, what's the advantage over a crank driven supercharger?" There are a couple of advantages. 1. Flexibility of installation. The power travel over electrical cables which means the supercharger can be mounted to suit the engine bay space and manifold. This is a considerable advantage in an engine bay as small as a Caterham's. 2. Flexibility of operation. Normal throttle operation can be used for the first 75% of the pedal travel, and the remaining 25% can bring the supercharger in progressively. This means that for normal road use the fuel consumption would be unaffected. 3. Efficiency. An electric motor can spin fast enough to drive a centrifugal compressor, which is much more efficient than the roots or sprintex stype crankshaft driven compressors. The low power of the electric motor means that it is best suited to the smaller engines, so a 1.6 engine running to 7000 rpm would benefit much more than a 2.0l engine running to 10,000 rpm. Crash team to the Upgradeitis ward, the withdrawal symptons are getting worse ❗ Link to comment Share on other sites More sharing options...
Bare Posted June 20, 2003 Share Posted June 20, 2003 Uhhh.. have you ever seen a way to generate a GENUINE 100 amps?? For more than seconds?? suitable for a 4 cyl engine, let alone one that was not part of a Stationary Diesel Genset? At a 100 amps one coud simply use a High Output Electric Motor in place of the Car's engine and Transmission... for Neck Snapping Acceleration. Nice Idea, but No Cigar :-) Link to comment Share on other sites More sharing options...
Joe 90 Posted June 20, 2003 Share Posted June 20, 2003 100 amps is inconvenient but not impossible (for inconvenient feel free to substitute expensive). The bext solution might be to go for one of the new 42V alternators, which will be introduced to power the electrically heated sets, window demisters, 8 speaker stereos on the latest luxury cars. 1000W is then a much more manageable 24Amps. I quite fancy designing a 1000W motor controller. Crash team to the Upgradeitis ward, the withdrawal symptons are getting worse ❗ Link to comment Share on other sites More sharing options...
Peter Carmichael Posted June 20, 2003 Share Posted June 20, 2003 100 amps. 12 volts. 1200 watts, less than 2 horsepower. Admittedly some electric motors can deliver max torque from standstill. Is a "High Output Electric Motor" one that gives you more energy than you put in? Link to comment Share on other sites More sharing options...
david nelson Posted July 9, 2003 Share Posted July 9, 2003 Supercharged 7 My x boss (MD BMW Oxford) Yes where the mini is made had a 7 with a cooper s engine in it. the bonnet had a scoop, its white and thats all i know Link to comment Share on other sites More sharing options...
John Hughes Posted July 10, 2003 Share Posted July 10, 2003 Would it be possible to use a hydraulic motor to drive the compressor ?? Was thinking along the lines of somthing like a power steering pump and a hydraulic motor. Have seen power steering pumps used to drive hydraulic winches, not sure about what speed a hydraulic motor can run at but a small gearbox could be used to get a compressor upto speed ?? Would prob be a bit heavier than electric motors but I'm sure it would have the power to pump enough air. John Edited by - john hughes on 10 Jul 2003 11:15:03 Link to comment Share on other sites More sharing options...
DohNut Posted July 10, 2003 Share Posted July 10, 2003 I think that hydraulics work best at transferring high forces at low speeds rather than spining somthing very fast, although they are good a tranferring power to inaccesible places. I seem to remember some superchargers using a magnetic clutch between the crank and the compressor. This is great in that when cruising at light throttle you are not using energy to compress the air and then stopping it going into the engine because the throttle is only open a bit. You do need to arrange for the engine to get SOME air when the compressor (positive displacement) is not being driven, This may be something really simple like a lightly sprung trap door that opens when the manifold pressure is below atmospheric. Does anyone know how big the VW G-Charger was 🤔 off the G60 golf and as I remember there was a smaller G-40 polo version. I think is was named after the shape of the pumping surface was like a "G" and the number was the depth of the G in mm It might be possible to pick one up second hand and they are about the right size, as they were used in the Golf on a 1.8L 8valve engine producing 160bhp or with a smaller compressor wheel 190bhp. Nick Link to comment Share on other sites More sharing options...
Nigel Riches Posted July 11, 2003 Share Posted July 11, 2003 Some of the Lancia Rally cars of years ago had an arrangement where a supercharger provided boost at low throtle opening, ie, when planting the boot, and at a predetermined R.P.M. a clutch disconnected the drive and boost was provided by a turbo, this was posssibly to overcome turbo lag at low gas velocity, with low engine R.P.M., it only gets as complicated as you make it! and don't forget, you don't get ought for nought, have fun, Nigel. 1982. 5 speed, clamshells. B.R.G / Ali. The True Colours. Link to comment Share on other sites More sharing options...
DohNut Posted July 11, 2003 Share Posted July 11, 2003 Cars Car Conversions this month has an article on a car with a turbo & supercharger and a magnetic clutch ❗ The highly overdriven supercharger works upto 3000rpm then the clutch disengages and a butterfly opens to allow the turbo (which is now up to boost) to continue supplying the engine. He gets full marks for injenuity, using a window winder motor to power the buterfly I think that it was The Lancia Delta S-4 which Nigel refers to. Nick Link to comment Share on other sites More sharing options...
edmandsd Posted July 11, 2003 Share Posted July 11, 2003 One of the staff at Power Engineering has a fwd Mk1 XR2 with an RS turbo engine plus a supercharger and nitrous giving a reliable 300 bhp/torque + and making it the fastest accelerating fwd car around at the moment. Home of BDR700 Link to comment Share on other sites More sharing options...
jackb_ms Posted July 16, 2003 Share Posted July 16, 2003 I had a idea Why not using 2 dc motors. One being a dynamo the other one powering a high speed fan. The good thing about the dc motor is that the speed of rotation varies according to the voltage it is powered by. SO the principile is easy and puting into practice can't be two difficult and the efficiency should be around 65 to 70 %. I have plenty of 120w dc motor so i just need to make a bracket find a high speed gearbox for the second motor. He Voila. You have a electric supercharger. I will give you some news! Jack Link to comment Share on other sites More sharing options...
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