Why a V8 instead of a Supercharged V6?

Why is it that truck manufacturers offer V8 models when they can just offer a supercharged V6? I'm sorry if it's a noob question, but why not just put an SC or Turbo on a 4.0L V6 and get 300+HP and more torque, then put a 5L V8?

What are the benefits of both?

 

doesnt a super charger or turbo require more maintenance?
doesnt that also create a higher compression ratio as well; which wears more on an engine?
i think those parts would also cost more than just having a regular V8 engine.

thats just my guess. if i had to chose, i think i would take a V8 engine.

 

Actually turbo'ed engines will create a lower compression than an NA... Not quite sure about supercharger, but my guess its lower as well. So you are wrong at that point.

Price is key... it will cost a manufacture less money to make a v8 engine then supplement a v6 with parts they dont even manufacture. If you look at most turbo'ed vehicles that come from the manufacture the turbos are made by a different company as well as most of its components..

Its basically all about the moneys..

 

the most important maintence thing with f/i is oil changes

 

Money and reliabity. V8's create power at low RPMs and fairly effortlessly. So for most cases you only use a fraction of what the V8 is capable of producing so you're not putting much strain on the engine. Plus V8's are heavy, they produce a lot of torque which is ideal for hauling and towing. A supercharger produces more power from a smaller engine but adds another expensive moving part to maintain.

 

Isn't the reason why you're required to run 93 fuel after installing the TRD supercharger because of the higher compression?

 

ya.. just read this (section #4):
http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech102.html

i couldnt definitively find an answer for the supercharger. however, it is suggested that compression ratio might be higher with one:
http://www.chevyhiperformance.com/t...s/0610ch_superchargers/compression_ratio.html

 

First you need to know what a turbo does... It forces more air into the engine, well when this happens your engine will run lean on lower octane gas... therefore a proper air-fuel mixture is important, or you will get the following:

Preignition is the reason why higher octane is more suitable in a turbo vehicle. Below is a great description i found... Couldn't be said better.


Knocking or pinging is a sound that an engine makes when the air-fuel mixture in the combustion chambers ignites too early. Although slight knocking or pinging won’t damage your engine, loud knocking can cause damage and should not be allowed to continue. The solution is to use a high octane fuel, which is actually more difficult to ignite, despite the misconception that high octane fuel is more powerful. When the fuel is more difficult to burn, early ignition is eliminated, and with it the knocking or pinging.

 

So, if a turbocharged engine is lower compression than a normal engine, what is the BOOST that is created and what is the reason for increase in HP and/or torque?

 

BOOST is PSI the turbo is creating. It's intake pressure and the increase in HP/torque is because you're forcing more air into your engine rather than having your engine suck air.
EDIT: Which goes back to what Yan said, you're not forcing more air into your engine and you need to adjust to maintain a favorable air/fuel ratio so the engine runs properly.

 

Ok just did some quick reading and in this case I don't think "compression ratio" is really the correct term to begin with...it probably really should be cylinder pressure instead. The higher volume of induced air increases the pressure within the cylinder which makes it prone to pre-ignite with a lower octane fuel in compression.

 

Think about this what would win 400hp 400tq v8 vs 400hp 400tq turbo v6. V8 would no boost lag. And both vehicle weighs the same. Sounds right?

 

In that case, Displacement > FI

 

There are way too many factors to compare a turbo, supercharged and N/A engine. You can generally speak of pros/cons of a forced induction V6 vs a V8 but there will always be exceptions depending on which vehicle, tuning, etc and also what you're trying to accomplish with the engine.

 

torque

 

I know, I was agreeing with you. This is one of those debates that could go on forever and in a million different directions so I was throwing that out there. Lots of factors to consider...

 

I love superchargers. I am not a fan of the lag on a turbo, but that is just preference, of course.

 

The reasons are as follows:

1. Expense... N/A engines are cheaper to make (usually), while a turbo/supercharged engine costs more and most vehicle manufacturers do not make their own parts. (I dunno if Toyota actually makes their own S/C or not.. )

2. End-user Stupidity... Manufacturer supplies you with a N/A V8.. yes, it sounds nice, but you are less likely to get some moron racing everything in sight and wrecking than when you put a boosted motor in. Something about the sound of the S/C whine and the turbo blow-off that just turns people into idiots?

3. Warranty... Boosted motors are much more likely to have failures before warranty is out.. do the math.

4. Regulations... Thanks to our lovely environmental laws, having a vehicle that isn't going to cost you huge amounts of money that has a s/c or turbo means that you're only getting a very low PSI increase.. and if you "tweak" your vehicle, you just voided the warranty, so now you're screwed when something does break.

5. Just ain't gonna happen... Read that first part again.

 

No, a turbo or supercharger will no change the compression ratio of the engine. You usually want to lower your compression ratio on a boosted engine however