Using the stock turbo will only increase the cost to build this system and make it live. The issue is wastegating around the stock charger to keep the backpressures in check and making it live. To those that say "But the stock turbo has a wastegate!"....... LOLi was thinking of doing a under body mount. as not to have to relocate a mess of stuff and mess with pipeing it all up in tight quarters. ive seen it time an time again on late model cars with great results. but i need some guidence on wheel sizes an housing sizes.is there like a rule of thumb to go by in picking my second turbo. cause i was going to try pulling it off with a stock style charger keeping the fab work to a reasonable level. an ive heard of tons of guys using the hx 35s an some other larger hx charger to pull off a cheep"er" just as affecive twin set up on their cummins. but i need some guidence,thats why im here to learn. i know it wouldnt make any gaint numbers im just looking to stand outa the crowd.
The stock turbo can not live in a situation with lots of backpressure - and the intergral wastegate is not enough to control that backpressure in a compound setup. While your attempting to plumb an exhaust around the stock turbo you should contemplate building the setup around a turbo that is easily upgraded and tweaked to dial your setup in. Especially if you have lots of turbos laying around you should be able to come up with something like an H2E, or S300, or S400 - all of which would take more abuse and be easily upgraded down the road - and not cost you much if anything. Roughly grab a turbo in the 60-66mm compressor range as your high pressure and then something in the 80mm as you low pressure - turbine wheel size and housings will greatly effect how it works. A junkyard turbo setup could be an H2E (common PSD upgrade turbo off an L10 Cummins) being fed by an S480 (found on many OTR trucks). It would work OK and you wouldn't have a lot of overhead.i'm not following the point your trying to get across. so your saying it cant work with a stock style turbo? is not gona cost me much at all i have tons of materials an cut an weld well. i just need some numbers to go by to pick out what i need. i have many different size turbos rangeing from smaller than stock to compressor housings the size of your head. waste gates blowoff valves. it just the matter of ive never done any custom turboing of any kind and i dont know what size takes what amount of drive pressure to spool it an how much the truck will push an blablabla the list goes on. im just tying to do it an it work the first time not a bunch of trial an error.