FoxGT

You're only going to be pressed for room if you get a horribly designed kit. It's very easy to fit two turbos in an engine bay with a 5.0 or even a 5.8 unless you decide to mount them somewhere exotic. Two turbos have double the oil feed lines & oil drain lines as for plumbing that depends on your setup.

Twins will spool faster because of less total rotating mass. Both will make pretty well equal power. A twin kit will have far superior header design, but it also has a bit higher backpressure. I personally don't like building single kits for rwd twin bank engines due to the crossover pipe, for one cool air is going to be going by it cooling exhaust gasses which makes them less dense so exhaust gas velocity will slow down. Another downside is thermal expansion; a crossover pipe will grown in length about 3/4-1", the block wont which puts a big stress on the crossover & can cause it to crack the pipe or the headers. This can be fixed with a flexjoint, but also takes up more room. Twin kits are far easier to build imo.
Turbos aren't high maintenance, If you change your oil/oil filter/air filter on time, let the car warm up before getting on it & give a bit of cool down time before shutting it off after running it hard (which a turbo timer can do for you) then a properly built turbo system will outlast your engine.

Turbos take just as much time to build boost as centrifugal superchargers depending on your exhaust a/r. Yet again, a properly setup kit you will not have to worry about losing boost. I've only had one situation where a car with one of my kits lost boost, about 6 years ago I used hose clamps & the pressure hose blew off after switching to tbolt clamps I haven't had any problems with any.
The problem is, if you run a smaller turbo on one side & a larger on the other you're going to be creating alot more backpressure on one side than the other. Saab aswell as another company tried this setup long ago, it performed horribly & wasn't very smooth.
One turbo does have a small bit more lag than twins due to heavier rotating mass. Lag can't be measured until boost threshold & it does depend on the exhaust side of your turbo. On my kits & others that i've driven/rode in they generally have about .2-.3 seconds of lag at higher rpm. At just above boost threshold my slowest one was about 1 second in 4th gear with pretty big turbo, the remedy... don't try to race someone while your in 4th or 5th gear, instead try the downshifting maneuver. As for boost threshold with a turbo, if you're worried about it think about it this way, how long does it take you in your car in 1st gear to get to 3000rpm?
Turbos will have lag no matter what unless there is another source spooling the turbo. It's not something you can get rid of, you can get it to the point where it is hardly noticable, but you wont get rid of it. turbo's are spooled by exhaust gas, which means you have to get quite a bit of air/fuel into the engine in the first place, then after it has enough exhaust to spin the turbine, it has to speed it up. It doesn't automatically just jump up to speed. The lighter your turbine wheel is the faster it will spool which is why two turbos have less lag than one large.

Also there is no properly sized for any engine, There is sizing it based on where you want your power. Some people prefer their turbo to spool at lower rpm with less lag & are willing to sacrifice high end. I personally prefer turbos a little on the larger side, granted I may not see full boost until 3500-3800 rpm, i'll make more power up top than someone with a smaller turbo. Larger turbos work well with n/a cams aswell, smaller turbos do not because of the higher backpressure in the manifold/header. If your backpressure is higher than your intake pressure, you'll get reversion during valve overlap which will cause a loss in power. Some companies make turbo cams for this purpose. If you're wanting less lag or more low end power I'd suggest going with a roots or twin screw s/c, which imo are more fun to drive. I personally favor a roots/twin screw supercharged car's feel over turbo, they feel faster even though they aren't due to the instant punch.
Turbo's cause a loss in power, you could see it if you went out & hooked a turbo up to your exhaust, but left the compressor disconnected.

Superchargers don't have the lag problem turbos do, even with a centrifugal, if you're turning 4k rpm and you floor it, the air & pressure is already there because the impeller of the centri is already spinning at a high rpm. If you floor it with a turbocharged car the impeller isn't spinning at a high speed. Centrifugals & turbos do share a common boost threshold point, but not lag.
While it will have less lag, twin & single turbos power curve is going to be near identical if both are setup properly.

Some companies use a sequential turbo setup using a smaller turbo & a larger turbo setup in parallel. All of the exhaust are routed into one, there is a gate blocking off the larger turbo so all exhaust is routed into the smaller, once it spools the gate is opened to provide gasses to the larger. This isn't as hard to do on an inline engine If you were to try this on a twin bank engine you would have to route all exhaust gasses into one pipe, then split both off into separate turbos & use a gate to control one.

mustangmike33

well in responce to your thread, im not trying to cause trouble cause i like you guy and your advice, but i recently bought a Vortec V1-S Trim off ebay for $970, which this price included all shipping and handling, as well as a new bearing rebuild kit and a new belt cause the other was too big for the pulley that i decided to use. i got all the hardware, the brakets, the intake elbow, the adjustable filter elbow that puts it into the fenderwell, a t-rex in-line fuel pump, FMU setup, and 4 different sized pulleys. the belt that came with it was run with a pulley that produced almost 18 lb. boost. too much for what i want. i havent installed it yet because the motor im building for it isnt complete yet. and by the way, im not running a blow off valve, and the motor in using it on i believe can handle the pressure without blowing anything off. but i do realize what you were saying, i guess im a belt driven kind of guy, but i do like turbos as well. and your right, you do get what you pay for, but i get everything i needed to fully redo mine so i got what i needed and wanted. but hey man its all good, take care!!!!