acook

hmmm anyone one else that can shed some light on this?

Roger rodbolt

Your last post asks for someone to "shed some light on this" but I'll only offer my opinions and ask questions. Since I don't know how you drive or what you are going to do with those 580-620HP, by looking at your signature I assume you pull a gooseneck trailer and drag race. If that is the case I think the IdahoCTD twins will do just fine, in fact may be a best choice. Setting the two turbo to work together is paramount and there is several ways to do this. Remember if your stock turbo is wastegated at 25lbs. and the wastegate (stock or modified) can keep the boost/drive pressure in check you gain the performance of the big turbo. There is only so much exhaust/heat/flow at any given rpm/engine load that has to be converted into enough energy to drive not one but two turbo. Drive pressure is your FRIEND until it becomes EXCESSIVE. This is why the early street turbo used a small top turbo with a big housing and ran that to a large bottom turbo. The top turbo did most of the work until you really spun the engine up then the big turbo would light. IMHO that is not the best or most efficient way to do it. (Do not confuse all out competition setups with street setups) Many of the small twins now balance both turbo and keep them in the "sweet spot" under normal driving conditions or even at 600+hp. My guess is that if Marco releases the CR rpm and you want to turn 4500rpm you will need a bigger turbine housing on the top turbo or at least a reliable external wastegate. If you want to shoot nitrous and propane then get a bigger top turbo and be prepared to loose some of your towing ability......etc...etc. Unless you are one of those guys that keep blowing up their stock turbo I think you'll be happy .