Silvia Club of NSW

I want to know why you cannot combine a turbo charger with a supercharger? Has it ever been tried before to your knowledge? Robert Lawndale, CA.

Known as twinchargers, the Lancia rally cars employed both a turbo and a supercharger. HKS even offered an upgrade for the Toyota MR2 with a supercharger-into-turbo kit. Nissan introduced a twincharged car, the front wheel drive March. The March (Nissan Micra in Europe) was originally offered in 1982 and is still around today in Japan and Europe, where there is also a Nismo version with intake, exhaust, suspension, and Rays rims (they get all the tasty cars). A turbo model was introduced in 1985, but the twincharged version was available from 1989-1992 and only sold in Japan and Malaysia. The March Super Turbo version had an inline 4 electronically fuel-injected 930cc single overhead cam turbo and supercharged engine, the MA09ERT. Only 110 hp at stock 0.7 bars of boost (about 10.3 psi), it was still practical to almost double the boost to get an extra 20-30 hp. At only 1700 pounds, the Super Turbo was capable of 0-60 in only 7.5 seconds. Is twincharging possible? Yes. Likely to see on a production car or cost effective? Not usually. It's hard enough trying to fit one forced induction system in an engine bay that trying to get two in a car already on the market would probably take some Crisco, a sledge hammer, and some funky body work. You can produce a kit where the turbo output powers the supercharger or vice versa. Powering a supercharger into a turbo takes advantage of low end spool since the supercharger is powered off the crank and doesn't have as much lag as larger turbos typically do. The supercharger blows air facing the turbo. However at high rpm, the turbo will be flowing too much air and there is a lot of backpressure, creating a vacuum. You would either have to disengage the supercharger as the turbo spooled up or add an outside source of air to power the turbo. Roots blowers, although not too efficient at high rpm, are cheaper and work well at low rpm, making it a most cost effective option. A variable speed centrifugal supercharger is a slightly pricier option as well. Use a higher boost setting in the low end and a low boost setting on the top end to let the turbo take over. Powering a turbo into a supercharger fools the turbo into thinking the engine is a greater displacement, but power is consumed by the spooled up supercharger and SC's are usually less efficient compressors than turbos. One easier option (both mechanically and on your wallet) is to use nitrous oxide to power a large, laggy turbo in the bottom end.

At tractor pulls, they are not using staged turbo's to gain response as much as they are using it to allow them to run ridiculous amount of boost through their engines.

There are obviously packaging issues with this approach too, as each stage needs to be intercooled or the air coming out of the final turbo will be scorching. The tractor guys use water injection between stages to overcome this problem, but i guess a w-to-a intercooler would work well in this application.

The tractor pullers run 200+psi manifold pressure..

What would the maximum boost be out of a BB T28 before it looses efficency / comes apart??

Sounds like you have a hang up on what boost pressure you want to run. You should make a power target and try to achieve it with as little boost as possible.

I had a discussion with one of the blokes at work about this topic a few weeks back...he said it's something that has always facinated him and one thing that he wouldn't mind attempting to do not just to see how much power you could make, but more so how smooth and powerful you could make the car.

The way we figured it is you would want a supercharger to make boost right off idle and hold reliably until around 3-4,000rpm by which time the turbo should be making enough pressure to take over the induction. The system would need to be designed in a way that the supercharger is disengaged once the turbo has built up enough pressure and that somehow the piping to the s/c is blocked and the turbo unblocked to stop unnessacery pressure loss in piping that doesn't need to be pressurised.

It is an interesting topic and if you sit down and have a good think about it it would be indeed possible to do, the fabrication process would be a bit of a headache but would be intereting to see how well it would perform.

yeah you also can't run much boost at very low rpm without running into detonation issues so if super low rpm torque is the main aim a larger engine is the best way to acheive it.