I'm planning to buy an 87-9 Iroc 305 (or an 87-9 350 that someone has added a 5 spd to) and was trying to plan out what upgrades and modification I plan to do. One of the big things I was having trouble figuring out was whether to plan on twin turbo or supercharged. In either case I plan to use a rebuilt 350 or bigger (402/454) that has been built to handle the increased power that a twin turbo or supercharger would add. I have had trouble finding anything meaningful on the subject because I am new to the field of car restorations and am not quite up to speed on the lingo.

What I have come to understand:
A supercharger is more expensive, simpler to install, uses power directly from the engine via a belt drive system, usually adds more power than turbos. additionally, it provides a constant boost level do to the direct nature of it powersupply.

Turbochargers tend to be cheaper than superchargers, feed off the exhaust flow, thus not robbing the engine of power, but they do cause backpressure which does cause a bogging effect. turbos are more complicated to install, have a delayed response due to the need to build up exhaust flow sufficient to drive the fan.

Both increase the performance of the engine by forcing more into the cylinder which in turn allows more fuel in the cylinder. to combat the issue of delayed boost on turbos, people often twin turbo. they both need intercoolers, and you can also use super turbos (didn't list this because I wasn't planning on doing it.)

Is this information accurate? Is there a meaningful difference in boost level between the two choices? what are the different types of superchargers/turbochargers? what makes them better, what makes them worse? any feedback is appreciated.

 

Don't forget turbo-supercharging. And intercooling. And Tuning. So much to learn!

 

There is a huge learning curve when using air induction. Fuel/air mixtures become absolutely critical! The more air, the more fuel and it changes through the RPM band. At 2k rpm you may produce only a couple of pounds of boost, at 5000 rpm, you are turning a lot of boost, and your fuel system has to follow the curve which requires a ton of computer tuning. It is NOT an easy way to go, cant just bolt on and go.
Turbochargers are more susceptible to damage due to the heat and oiling system. Say you run a turbo car hard and pull in to a parking lot and shut her off, the turbo keeps spinning for up to several minutes without oil pressure and can, over time, sieze up. Without a turbo timer (which isn't cheap)you can harm your turbos. With a Supercharger, when you cut off that engine, the charger stops, no damage, no fuss. As for power, you can get all you want out of a turbo, where superchargers are a bit more limited. Ive seen 1300+ horses off of turbo cars, and they are still streetable..

 

My turbos dont spin for long after shutdown but its true too much spinning and no oil can seize the bearing.

What supercharger type? Centrifugal or roots type ?

Centris have a linear boost curve unless you do a wastegate bypass boost control. Makes fueling pretty predictable and smoother onset of power.
Roots have more instant boost effect, very torquey response. However heat soak is big disadvantage. Centri's can also have a heatsoak effect with air intake usually being over header or in engine bay
Blowers can have bad belt slip issues on high boost.

Turbos can be violent in power onset. Its not linear and can build boost very quickly at lower rpms if sizes right. All depends on how you setup the combo. Turbos driven by exhaust is not free energy, still some engine hp lost that way due to restriction in exhaust flow. Turbos can make more power imo if you get the air from outside engine bay, and the fact you can make peak boost at lower rpms which greatly increases power under the curve

Blower kits arent cheap but unless you are good at fabrication, a good turbo kit wont be cheap either. Theres just alot more cheap turbos available to greatly offset the cost from a blower

 

Superchargers don't add "more power" than a turbo...it all depends on the setup. type of turbo etc....

The turbo units themselves do tend to be cheaper, but a lot of mods and fabrication needs to be done to make everything fit....and tuning to make it all run right. There's a lot of power potential there though if you know what you're doing.

Superchargers (centrifugal type) cost more initially because they can be had in a bolt-on kit for most cars...a lot less fabrication needed. So - you're in essence paying the extra $$ instead of fabricating a lot of things like you would a turbo.

Of course as you said, superchargers have more parasitic loss than a turbo...but in the end, it all comes down to boost level and intake charge temps which determines how much power you make...

When you're talking a roots type blower...just like Orr is saying...the whole power band is different. You want a fun street machine traffic light to traffic light?? A roots is a great choice IMO from idle to 5500...which is where most of your street driving is!!

 

Turbos are also soft on parts compared to built motors and blowers.

Either way you will need a way to tune (ebl-flash or code59) and have adequate fuel from the pump to the injectors.

Just find someone's setup on here that you like and piece together something that would be good for your application.

 

I would have to say turbos are easier to install since I did my turbo install with stainless steel from the scrap yard and did all the fabrication in my drive way with fairly simple tools.
Cummins guys keep ebay fully stocked with plenty of Holset take offs from when they do upgrades so good turbos are easy to come by.
I believe a supercharger install would have cost a lot more and been more difficult, plus no on really puts super chargers on diesels any more.

 

i beg to differ a set of t3 turbos or the small t3/t4 hybrids work just as well as a roots blower idle to 5500 , specially with tpi

even a set of t3 50 trims will give u more off idle tq and power then u can use, boost is instant

 

I havent been in a small turbo car that spooled quick but it is a possibility to get pretty good spool off idle, i just think something that small to spool that quick would hurt top end alittle more than a roots. Hard to say.

I've driven a 500 whp 5.4l blower lightning and the response was much like a built big cube na motor that had more of a low rpm powerband. Very torquey. More so than stock tpi L98

Doesnt matter anyway, because 80-90% of these builds whether blower or turbo are built around automatic trannys and your tranny should have alot higher stall than stock so off idle to 2000, who cares. Typical 2500-3000 stall works well with most setups. The crazier you get, you stall it like a na motor where your boost threshold is or where cam makes power. 3000-5500 stall shifting at 5500-7500+ lol all depends where you want power. Big blower or turbo on a big cam an head motor for big will or can have instant response, just not at lower rpms. No different than any other motor na or what have you. All components must match