Turbo build questions. I want your opinions.

[04dreamcobra]

I am nearing a crossroad with my currently Whipple charged 04 Cobra. I am wanting to put down at least 800 to the wheels but can't decide the path to go. I like the ideal of a turbo because it seems a bigger blower woud just be less fun to drive and since its a street car primarely I want it to be "practical".
I am tossing around either the 3.4 or 4.0 Whipple if I stay supercharged or single or twin turbo if I change to that. My question is what are the pros and cons of single or twins and driveability. It does make long trips once a year so I need it to be dependable but when I wanna go it should be ready for it. So what are your opinions? Im new to the turbo world so dont hold back. Thanks in advance. :beer:

 

[static74]

This horse has been beaten numerous times. Search function ftw.

The most recent thread is here:
http://www.svtperformance.com/forums/blower-bistro-74/904352-twin-vs-single-turbo.html


Cliff notes:

Twin - quicker spool, lots more work and money, more to go wrong, 5lbs of crap in a 1 lb bag.

Single - the choice of many, easy(ier) to install and maintain, less to go wrong, more dependable, can make huge power just like twin. The right turbo will spool almost or just as quick as twin setups. Not to mention it is usually a cheaper setup.

Turbo cars are second half track cars, they make most of their power high mid to high rpm vs blowers being low to mid end, unless we are talking centri's.

 

[04dreamcobra]

My search doesnt work for some reason... Thats why i made the thread. It always says i have to wait so much time before I search again. It says it on the first search. Thanks for some info though. Am I on the right page wit thinking the turbo will be less abusive to the engine than a big blower?

 

[AntiHeightPunk]

either way turbo or 3.4 or 4.0 whipple you need to be prepared to build the bottom end and the transmission will need to be built. most of the components on the 03 cobra are solid to around 650rwhp reliable. now is when you need to dig in your pockets.

one thing in your post i dont understand is why would a big whipple not be fun on the street and a turbo would?

 

[04dreamcobra]

Not that it wouldnt be fun. I have heard that the bigger blowers are just more abusive on the engines. I am sure it would be a blast! Just a poor choice of words i guess. ha. I just want to makke sure it is streetable. And the engine is being built for sure when i break into it at that point. Trans too.

 

[AntiHeightPunk]

bigger positive displacement blowers are really fun on e85 or race gas, i would build the stuff up before it breaks.....will save you a ton of cash

 

[tt335ci03cobra]

If you want 800whp reliably on stock internals, turbo power is softer than blower power. You won't have parasitic drag/losses from belts and the boost is cradled; ie pushing and pulling on the rotating assembly vs simply pushing on the rotating assembly in sc setups.

Twins do have a lot more parts but its not as bad as he says about it being 5lbs of parts in a 1lbs bag. Yes it is trickier but its not that bad.

As far as parts failing or going bad, that mainly comes down to research and the extent of the build. If you have a difficulty in budgeting about $7-10k to go twin turbo, then it will be a difficult build. It's much easier to buy a reputable kit and have it optioned correctly than it is to piece one together for first time turbo builds.

It is true that a seasoned turbo builder can easily put a kit together for about half of what the off the shelf kits sell for but that's because they'll know all the small things like turbo placement for oil pickup/drainage, selecting trims and turbo size, heat wrapping, lines, hoses, fittings, discharge, bov setup, return or return-less fuel, e85/petrol, cold/hot piping, journal or bb, etc etc etc, for the average car guy, buying a kit is much more practice than trying to figure it all out.

I'd recommend tagging along as its installed/doing the install with a seasoned friend who's installed kits before because there are many shops that don't quite get installs right because of simple mistakes that can be catastrophic, stuff kinda like a jiffy lube guy forgetting a filter kinda stuff, simple mistakes, huge consequences.

Anyways, bar none if you want 800whp and can't quite afford a full motor/trans build right now, twins is the only option. If you have 650-700whp out of a twin screw now, your engine is already making about 800whp but about 100+whp is being eaton up to spin the blower so with the same or less boost than you're running now, you'll make 800whp roughly if you go twin turbo.

Turbos also have a much richer powerband. Everybody thinks turbos have no torque until they fully spool at an assumed 5,000rpms which is total rot. Real world, if you are in 6th gear with average size turbos around 2000rpms and stand on the gas for 1-3 seconds, you'll see 6+ psi before 2400rpms and have minimum 400-500wtq in a terminator. Yes a whipple might be making 600wtq at 2500 rpm vs a turbo car but honestly it's not like 400-500wtq is a dog, it's still tons more than stock and by 2800rpms you'll be seeing 10+psi and be making 600+wtq, around 31-3300rpms you'll see 15psi and have around 675-750wtq. Again this is assuming a good kit with say twin 57's on a stock 4.6.

I had a stock 4.6 terminator with 57's on it and it more low and mid range punch than my eaton/nitrous combo on another stock terminator 4.6 as long as I didn't mind a second or so of spool.

Lastly, 6psi of turbo boost is worth a lot more power than 6psi of sc boost assuming similar volume on each compressor. Twin 57's at 6psi will make about as much power on a stock terminator mill as 10-11+psi through a 2.1 or even 2.8kb/whipple.

For comparison, when I had the 4.6 (stock internals) with 57's, it made 510whp on 6psi, 650whp on 12psi and 756whp on 16psi. I would see 10psi after a second, maybe two seconds of spool from 22-2500rpms. I raced a cammed c5 z06 in 4th gear from 50 and beat it by car lengths on about 9psi, he didn't even jump out on me from the start of the race, I just stayed even at the start, and progressively pulled farther away from him till redline (of 4th with 3.55's) when I let off because I was a bus and a half ahead.

Twin screws are awesome as well but much harder on internals, much easier install but 800whp twin screw is literally 950+hp in the motor, parasitic drag and heat soak eat up the rest. The stress of a 4.0 twinscrew is even harsher than a 2.8 because its larger parts, more volume, more parasitic drag and so on. 30psi on a 4.0 will make tons more power than 30psi on a 2.1-2.8 but its because its flowing 4l at 30psi instead of 2.1-2.8l at 30psi so the internals of the blower are bigger and the drag and resistance is higher since its larger volumetric resistance. In short, the same way 30psi through a single 100mm turbo will make tons more power (optimally) than 30psi in a single 60mm turbo, you'll also have all the added stress of such a bigger compressor. Psi is just pressure per square inch, you can have 30psi coming through a straw which is very little air flow or 30psi coming through a coffee can sized pipe and it would be tons of airflow. When you add fuel to this new airflow, then spark and cycle it through the rotating assembly, the added straw sized airflow will do next to nothing in terms of power potential, maybe 50whp,where as the coffee can sized 30psi will probably blow the block apart unless its configured to handle something like 2000whp power potential out of all that added oxygen. Now imagine you have a pullied mechanism strapped to your car to spin these two compressors instead of exhaust gasses turning a finned shaft. The little straw esq compressor won't have much drag on the rotating assembly, maybe 10-20hp to spin this "accessory drive" like pullied compressor. Now if you strap on the coffee can sized compressor, it's going to need a lot more power to compress all that air, something like 350+hp. Yes it's capable of 2000whp but its also realistically meaning the motor will be making atleast 2450hp between ~100hp tranny/drivetrain drag and 350hp sc compressor drag. A similar turbo car would only have about 1-3% drag on the exhaust side of the engine so it would only eat up about 20-26hp... Huge difference especially once you couple the physics of force vs inertia. Turbos create force and intertia by pushing and pulling, inertia is softer than raw force. Sc can only force air in which is harsher. The harder boost of an sc plus the drag means a stock internal motor will not live long on a 4.0L supercharger at 800whp. Can it last? Ya stranger things have happened with terminator mills like a bone stock internal hellion build making 1188whp with twin 67's but I wouldn't gamble on it with my own engine.

There's tons and tons and tons of things I didn't go into but cliff notes:

-I'd go twins
-I'd wait to go twins until you can afford a reputable kit like thp or hellion etc
-I'd run lower boost or about 750whp (like I did, 16psi) until you build the motor/trans. 50whp is that noticeable at 750whp, but it is a great cushion for safety and reliability.

Good luck and sorry if this post seems unedited and mangled, I spoke text it on my lunch break while watching YouTube. Ask any questions and if I can help/have any output, I'll post back. Good luck!

 

[AntiHeightPunk]

wish i had a 5.4 in my car

 

[tt335ci03cobra]

wish i had a 5.4 in my car

They're really cool, and make great torque but honestly coyote's have more potential IMO, and are easier to fit.

If my 5.4 grenades, I wanna do a built coyote with vvt-ti heads to replace it.

Twin bb 67mm 5.8 (4v 2013 gt500 mill) with vvt-ti heads and a magically strong rotating assembly for 9000rpm strength would be my dream ford motor, I know it'd be tall and bulky and pricey as all hell but dream motor no less, so much win!!

 

[itSSlow98]

The great thing about big hp turbo cars is you literally have no clue the power the car has. It will drive like a bone stock car and get better gas meilage then a stock car. Im getting 24-25 on the highway and 18 city.

I just prefer turbo>big PD blower because its a lot more useable on the street. Not many 800rwhp whipple cars can get out of there own way from 0-40mph on the street.

 

[tt335ci03cobra]

+1^^

I get 27+ mpg freeway (3.08 rear, viper overdrives~1300rpm at 70-75mph) and even just on 4.5psi off my wastegate springs, the lowest boost I can run, I have easy 11 second power. Mpg wise, twin screws are thirstiest but instantaneously torquier because toe in boost/virtually no spool just boost.

turbo can be super quiet too. I usually run open e mild/wild cutouts and its less than 95 db at wot. Closed, the cars exhaust at freeway speeds is quiet enough that tire, gear, and road noise overpower the exhaust note. (Road noise is probably 10-20db louder than stock though; tubular/delrin/poly/etc suspension/chassis mods). Usually a big twin screw car will be running full exhaust which sounds awesome at wot but is a cop magnet and harder to live with on longer drives at drone inducing 1500-2500rpm ranges.

I like being able to change boost easily electronically via boost controllers. I can go from wastegate springs (4.5-6psi, 550-600whp) to 18psi (max pump gas, 900~whp) in 2-3 seconds while driving. Pulley swaps aren't that hard any more and switch chips can be installed into sc cars do you can change tunes easier now than it uses to be via obd-2 programmer upload.

Sounds is a toss up but I love me some open e-cut out/pure wastegate/bov freeway underpasses and tunnels. Blower wine is awesome too though.

 

[04dreamcobra]

WOW! Great info! Thanks! This is what i was thinking with the big Whipple vs turbo. I would rather have driveability than crazy power. At 600RWHP now traction can be iffy at times from the instant torque. So i dont mind a little lag till i get moving. I wil be doing a built block so i dont have to worry about a time bomb. That way i can sell my longblock minus a few parts for the change over and recoup some of the money.

 

[tt335ci03cobra]

Cool man, good luck on the build/setup!