supercharger vs. turbocharger

[UNRULEE]

A turbo is more efficient, taking waste (exhaust) and turning it into more power.


I own both kinds with my 6.0 and my Pontiac Gran Prix GTP, and both are a hoot to drive!!!

 

[LEB Ben]

I chose S/C because I don't like lag.

Maybe a little, but nothing like the power a s/c robs..

Pretty sure S/Cs can rob upwards of 30%.

 

[Fellro]

Detroit's had blowers on them.....Screamin' sum bucks!

What was that saying Cody, 'drive them like you're mad at them'!

An old Detroit won't run without them either, they were necessary to push the air though them. They also piggybacked turbos on some of them.

 

[LEB Ben]

^^^That would be a helluva setup. Any chance you have a ballpark of peak numbers on something like that?

 

[Fellro]

I'd have to do some looking, but keep in mind, the 2 stroke design of the old Detroits required use of a a blower to just simply run. They blew in fresh air and pushed out the exhaust through the holes in the side of the cylinder. They only had exhaust valves, no intake valves. The turbo is what would make any kind of boost there, the non-turbo motors were considered naturally aspirated, even with the blower on them.

The well known 6v71 GMC blower is originated from the Detroit diesel, the 6v71 designation is 6 cylinder v cylinder arrangement 71 series motor.

 

[LEB Ben]

Oh...didn't know that.

 

[dragogt]

I chose S/C because I don't like lag.

Pretty sure S/Cs can rob upwards of 30%.

Its all in how its setup..

Exactly, I remember hearing something about that the S/C on top fuel car requires 500 hp to turn...

 

[5.0Flareside]

ok.... this is honestly gonna be a lengthy post from me...

I Love both.. both do the forced induction differently.

Turbo's: the whole Turbo Lag thing is stupid... its when a Turbo is incorrectly matched to a engine... a 2L 4 banger with a 70ish MM turbo on it, thats gonna take for ever to get the turbo to the point of spooling up... not enough exhaust flow... while with a 40ish MM turbo on it it'll be a ton! faster and better running, wont take as much exhaust to get it going, will be virtually no turbo lag...

think about a huge fan (turbo fins), and the electric motor used to turn it (exhaust gases) you would never put a small electric motor (small exhaust producer) on a big fan (turbo) would take for ever to get it going (turbo lag) and keep it going would be a pain....

but on the other hand a much smaller fan, with that same size motor... well it wont take much to get than fan going....

so take that for what its worth, thats the way i've been talking bout turbos since i've understood their concept... and is exactly how a guy i know who builds turbo'd cars agreed with me on the concept...
just gotta a correctly chosen turbo for the engine...

SC'd... ok... Superchargers are awesome...... make great power also, while they do cause a slight bit of parasidic loss, its not as much as lots of people think, its somewhere truthfully 5-10% at most on a everyday application.. and yes, they do cost a bit more, but they are worth it depending on what your using the engine for...



my conclusion, for every day use, turbo, for the simple cost factor, costs less to maintain if its a good turbo and not abused, also, makes great power if correctly done, and no parasidic loss as compared to a SC....

but i like superchargers more...

 

[Skandocious]

ok.... this is honestly gonna be a lengthy post from me...

I Love both.. both do the forced induction differently.

Turbo's: the whole Turbo Lag thing is stupid... its when a Turbo is incorrectly matched to a engine... a 2L 4 banger with a 70ish MM turbo on it, thats gonna take for ever to get the turbo to the point of spooling up... not enough exhaust flow... while with a 40ish MM turbo on it it'll be a ton! faster and better running, wont take as much exhaust to get it going, will be virtually no turbo lag...

Unfortunately it's not quite that simple, otherwise all turbo'd engines would just use tiny turbos to eliminate reduce lag. You need to have a properly sized turbo to ensure that you're getting boost in the spots of the RPM range where it matters. This is why the 6.4L shifted to a twin-turbo setup (to eliminate turbo lag). Uses a small turbo in conjunction with a large turbo to reduce lag because they spool at different RPMs. Unfortunately this only fixed half of the problem because there was still lag that resulted from having to build up pressure in the long duct between the turbo and the intake (remember that the turbos on the 6.4L are located closer to the exhaust. That time to build pressure in the duct might be minute, but it's enough to translate to noticeable lag (my brother notices it a bit in his 6.4L).

But Ford solved this issue with the 6.7L. They flipped the heads, so the turbo is now in the valley and thus the ductwork is much shorter/smaller-- less space to build up pressure means less time to pressurize and get the air into the combustion chamber.

Ford wouldn't be spending so much money on fancy engine designs to eliminate lag if it were as simple as using a smaller turbo.


All of that being said-- I'm am FAR from an expert on either of these engines so if I have misstated anything then someone please correct me.

 

[5.0Flareside]

Unfortunately it's not quite that simple, otherwise all turbo'd engines would just use tiny turbos to eliminate reduce lag. You need to have a properly sized turbo to ensure that you're getting boost in the spots of the RPM range where it matters. This is why the 6.4L shifted to a twin-turbo setup (to eliminate turbo lag). Uses a small turbo in conjunction with a large turbo to reduce lag because they spool at different RPMs. Unfortunately this only fixed half of the problem because there was still lag that resulted from having to build up pressure in the long duct between the turbo and the intake (remember that the turbos on the 6.4L are located closer to the exhaust. That time to build pressure in the duct might be minute, but it's enough to translate to noticeable lag (my brother notices it a bit in his 6.4L).

But Ford solved this issue with the 6.7L. They flipped the heads, so the turbo is now in the valley and thus the ductwork is much shorter/smaller-- less space to build up pressure means less time to pressurize and get the air into the combustion chamber.

Ford wouldn't be spending so much money on fancy engine designs to eliminate lag if it were as simple as using a smaller turbo.


All of that being said-- I'm am FAR from an expert on either of these engines so if I have misstated anything then someone please correct me.

Yes... i understand all of that completely...

and yes.... my explanation was on the very simple idea of the basics of the turbo lag issue... theres several other issues that play into it, but the largest problem with turbo lag is to big of turbos...


and i was actually talking to brad bout this on the phone.... the 6.7 is pure genious switching the intake and exhaust ports, so the turbos are right on top of the engine where the exhaust aint loosing velocity through a down pipe etc... and then its feeding into the intercooler and almost immediatly after that its in the intake, no fooling around, no wasted space pretty much..

its all about the correct size turbo... a lil bit of turbo lag is acceptable if you have Power all through the RPM ranges... but if you have alot of turbo lag and only have power at higher RPMs well then you didnt do a good job of matching junk together...

theres a math to Turbo size, im not smart enough to understand it 100%, but i can grasp the general idea of it..

 

[Skandocious]

a lil bit of turbo lag is acceptable if you have Power all through the RPM ranges...

I think Ford is of the opinion that a lil bit of turbo lag is not acceptable... Otherwise they wouldn't be working so hard to eliminate the little bit that was present on the 6.4

 

[5.0Flareside]

I think Ford is of the opinion that a lil bit of turbo lag is not acceptable... Otherwise they wouldn't be working so hard to eliminate the little bit that was present on the 6.4

Guess i shouldve rephrased my words... no Turbo Lag isnt acceptable in Modern Brand New vehicles, what i'm saying is older vehicles little to no turbo lag is alright.... now i know i wouldnt personally be happy, but cant always be 100%.... and yes... Ford is doing a absolutely TREMENDOUS job with their Turbo Applicable designs...

 

[Skandocious]

Guess i shouldve rephrased my words... no Turbo Lag isnt acceptable in Modern Brand New vehicles, what i'm saying is older vehicles little to no turbo lag is alright.... now i know i wouldnt personally be happy, but cant always be 100%.... and yes... Ford is doing a absolutely TREMENDOUS job with their Turbo Applicable designs...

 

[BIGRED911]

I'd have to do some looking, but keep in mind, the 2 stroke design of the old Detroits required use of a a blower to just simply run. They blew in fresh air and pushed out the exhaust through the holes in the side of the cylinder. They only had exhaust valves, no intake valves. The turbo is what would make any kind of boost there, the non-turbo motors were considered naturally aspirated, even with the blower on them.

The well known 6v71 GMC blower is originated from the Detroit diesel, the 6v71 designation is 6 cylinder v cylinder arrangement 71 series motor.

the 71s on the 6v71,8v71 and the big ole 12v71s refered to the cubic inch per cylinder i do beleive...and as far as peak hp with turbos and blowers look up any of the pro stock pulling semis that are runnin the buzzin dozen...well over 2000hp on tap and turnin more rpm that youd wanna know, but the down side is lack of torque...4 stroke engines by design make more torque than 2 strokes(and and inline arangement makes more over a v style,just cuz cummins is hangin back while the v8 diesels have their moment in the sun i know for a fact they have a program for the 6.7 cummins thats 450hp and well over 900ft/lbs but they cant find a tranny to hold it and the general public dont need a pickup with that much power)...hence the reason modern diesels are 4 stroke(and why semis are now all inline 6s) and why i always ran 4 stroke 4 wheelers when i was racin....i love me some torque!!!!

btw im turnin my isx up from 400 smart torque 400 hp 1450/1650ft/lbs to a 500 smart torque 500hp 1650/1850....also on a side note, on all cummins engines other than the 6.7 cummins rates average hp not peak, my 400 setting peaks at 502rwhp...the 500 setting im goin to is over 605 to the ground...and all cummins numbers are rated to the ground not crank...cat and detroit are at the crank...

 

[gsxr1238]

and all cummins numbers are rated to the ground not crank...cat and detroit are at the crank...
I don't think that is the case.SAE rules say flywheel horsepower is the advertised horsepower.Gas,Natural Gas,or DIESEL!Too many variables in parasitic loads,drivetrains,etc.Would really be interested in seeing a chassis dyno report before and after you turn that engine up.

 

[LEB Ben]

Hmmm...this turbo and subsequent lag discussion sounds like a modern day 'overcarbing' discussion.

 

[UNRULEE]

Here's what I know.......correct me if I'm wrong.

An old Detroit won't run without them either, they were necessary to push the air though them. They also piggybacked turbos on some of them.

Yup, the early Detroits ran supercharger and in that configuration they were actually classified as a N/A engine. The later 92 series added a turbo to the mix.

They only had exhaust valves, no intake valves. The turbo is what would make any kind of boost there, the non-turbo motors were considered naturally aspirated, even with the blower on them.

The well known 6v71 GMC blower is originated from the Detroit diesel, the 6v71 designation is 6 cylinder v cylinder arrangement 71 series motor.

Yup, two stroke, the pistons are actually the intake valves.


..........and the 8v71 blower is derived from the 8 cylinder 71 series engines.

This is why the 6.4L shifted to a twin-turbo setup (to eliminate turbo lag).
But Ford solved this issue with the 6.7L. They flipped the heads, so the turbo is now in the valley and thus the ductwork is much shorter/smaller-- less space to build up pressure means less time to pressurize and get the air into the combustion chamber.

They actually consider that set-up to be a compound turbo rather than twin turbo. In the 6.7's an atmospheric turbo feeds the other turbo, which further increases boost. One is variable vain and the other is fixed. I believe that the "secondary" turbo is VGT.

The 6.7 is revolutionary in it's design with the heads being "flipped", much more efficient use of the exhaust drive pressure to the turbo (and yes I say TURBO, as in single) the new 6.7 because it's a whole new animal with that turbo on it.

The 6.7 turbo actually is two compressor wheels and one exhaust wheel mounted on one shaft. Essentially making two turbos out of one.