The Plenum

Some time ago i was looking around a drawing of the 24v plenum and it didnt take long for me to see the problem, in fact if you remove the throttle body and look inside you see a wall of casting, the air has to pass through and around this casting, not good, further investigation told me that it was designed for an engine that would produce bestpower and volumetic efficiency between 3600rpm and 5000rpm,ideal for auto box but, not ideal for my manual gearbox,what is more of a worry is, beyond 240bhp the restrictions become a real problem, Any attemps to boost the airflow with a turbo or supercharger would also be restricted by this bottle neck, so the more i looked in to it, the more it became a "do-able job".

well now i have found a like minded person who has his own workshop and together we have chatted away with this one aim in mind, we now seem to have ironed out many problems,The development manifold is to be cast out of alloy and will be of two parts, base and lid. this was we thought would allow us more options with extendable trumpets, a partitions and packing blocks to fine tune the inlet tracts and plenum volumes, eventually this development plenum will carry 6 extra injectors ready for turbo/supercharger requirements. At the time of my starting to write this page, there is a base plate thats all machined with a throttle bolted on it, ready to take the cover, the later pictures should show the lid attached

Inside will be trumpets these can be ajusted in length so as to obtain the best possible power, the next picture shows a fibre glass moulding taken from our plug (mould), this did stick and will eventualy be made in carbon fibre but for now its cheaper to use fibre glass for testing. h5>

well the plenum was delivered and it looked like this

well here is a view inside, this shows the center partition fitted to alow two smaller plenum volumes.

And here it is being test fitted to a spare engine

but there was a problem, once fitted the bonnet wouldnt close, so it was back to the workshop for a mod to lower the throttle down. however the engine was run and tested with out being driven and the engine responded very well and rev'd more freely. The plenum was sent off with all the information required to change the angle of the throttle alowing the bonnet to close, so any day now i should be able to report how she goes once its re-fitted.

well it was returned and fitted thetesting started and the results where truly good, the power band had moved up the range, as expected and it drives so much better tho between myself and mike at boost performance long discusions took place! W e are very happy with the out come but feel we could get a slightly better air flow with twin throttles of the 12v engine.

below you will see the next plenum, the MK2 that id due to be fitted very soon, at this time i am making changes to the throttle and verious parts to alow it to be fitted with ease.