Strictly what I’ve noticed over the course of several years I listed below. This thread wasn’t designed to bash or make one company stand out over the other but is designed to look back & reflect where the B5 S4 stands today.
After 12+ yrs the B5 S4 seems to be lacking a versatile turbo setup for a reasonable price.
Versatile meaning “turbo of quality that performs well down low, mid-range & up top without going broke”
[center] [center][b][u]So far we have the usually below[/u][/b][/center][/center]
RS4 K04 setup (good low – great mid range turbo) expensive & hard to get. Than we have the hybrid setups ie larger compressor wheel No better than the factory RS4 turbo, this has prove to be a large failure for many years. The turbine wheel & housing is far too small “makes the upgraded compressor wheel useless”.
RS6 setup (OK low, great mid – good upper mid range turbo, not much top end) too much money, work & hard to get! With all the modifications needed to make them fit like (cutting, shaving, welding & relocating made these near impossible for the average consumer to take the set of RS6 turbos and make them fit) Than we had very expensive hybrid setups, proved some success but companies abandoned them quickly, the turbine wheel was never addressed properly. Once again to much work, time, talent needed to make them fit. Not practical for the cost of the full setup!
Tial 605 kit (good mid – good upper mid turbo) Very large fancy compressor wheel journal bearing turbo with a pretty fairly small turbine wheel in comparison to the compressor wheel, same mistake the hybrids listed above makes in my opinion. Very comparable to the standard RS6 with a little more peak hp gains but you have to run 32+lbs, more expensive, does bolt on but lacks the low – mid that the RS6 has but doesn’t overall outperform the standard RS6 when looking at the complete power band.
Tial 770 kit (good mid – very limited top end) this setup is really expensive, plan on running 35 - 40+lbs of boost to achieve nothing more than your standard GT kit at 26-28lbs, the priciest setups to date for the parts you get or don’t get by the time you’re done collecting all the parts. They don’t come with down pipes or manifolds. For this power band & setup one would do far better with a custom GT kit where turbo selection & custom wheels are wide & readily available. This setup isn’t justifiable with realistic gains to support the overall project cost at all.
GT kits (great mid – insane top end range turbo) not real fun driving at low rpms & speed. I would say strictly for the guy who wishes to go all out from start to finish while addressing the entire car from end to end. Down side “full kit not readily available & if you don’t go all out ie total car build then it’s pointless” When done correctly you’ll have a super car +!! Have check book ready & maybe you’re first born!!!
Single Turbo kit (Great for drag car) Pros (If you have strictly drag car changing the unit is easier, that’s it) Cons Not practical for many reason “think Honda with large turbo” the fun part where you mainly drive the car around town is now gone just like the 605, 770 turbos, having the crisp throttle response @ lower rpms like K03, K04 & RS6 turbos will never be there anymore, far more relocating work than most realize, potential engine fire is high, runner length on manifolds add length/volume that slow exhaust gases down so on paper the turbo you think is ideal is again to large to spool great, the refined feeling of the Audi is now gone, obtain overall less performance for more money & headaches than what other kits already out offer, turbo by the fire wall is the worst possible place to put anything generating a lot of heat, overall not cheaper, if so not worth the deleting, relocating, risk involved & the list goes on.
After near 1 year of testing, gathering info & from 7 yrs of personal experiences with just about every setup I have the hands down winner. Some may dissagree, think it’s bias or whatever but it’s really the hard all around facts.