art 09 03

TECH TORQUE

tions are aboul the sensible limit. From there you have to start pulting some senous mods out of the bag tor bigger mcreases It s all about the law of dimmishing returns once power levels start to increase much beyond 30 per cent.

Rather than be locked into the ttny T25 exhaust housing tound on these cars. Tim came up with a clean sheet ot paper' tur-bocharger. which features much bigger internals. but also needs a fabricated exhaust manilold. This gives RPM the chance to eftec-Uvely replace both the restrictiye turbocharger and tiny cast mani-fold. Surę it costs morę to do. but as Tim is quick to point out, there is no choice if 150kW at the wheeis is desired.

The turbocharger used is affec-tionately referred to as the RPM hybrid. It is based around the extremely durable and internally 'big Hitachi turbochargers. as used on the turbo factory rotaries. It‘s not a case of bolting the Hitachi straigh:

also a good idea at this stage. as the increased air-tlow potential o‘ the RPM hybrid turbo ensures that if retained. the

Although th.s sounds like a good altemative to the high-ftow item. there are the hidden costs ot the manitold tabncation, and the

designed their own bar and piąte intercooler that tucks tn behind the nose of the Si3, taking a central

very little pressure drop through the core Ino morę than Ipsi drop at 400hp'l and it looks good with tne shmy core erposed Mounted up as hooked up to the hybrid turbocharg-

Management then becomes an

proven path of fitting a Microtech MT8 fuel ano timing system.

system remapped to proyide the is still not much better trom an a completely mappable system

miictures and timing altows the CA18DET to make a substantiai power gam over its stock-com-puter mild-tune buddy, teatured

bing pressure drop. RPM have

upgrade path for bigger mjectors

hot4s ń pfPFnerr-nc- mm i