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View Full Version : Increased displacement vs. forced induction



Edmond
12-07-02, 06:51 PM
Can you guys give me the benefits and downfalls of each?

Which is safer?

Cheaper?

More efficient?

Easier to do?

Given the choice, which would you do?

klb76
12-07-02, 06:58 PM
The idea of turbos and whatnot sounds very attractive and "cool" but I have heard it too many times that "there is no replacement for displacement" so my vote goes for bore + stroke. Although I really don't know the benefits and downfalls of each.

klb

Mako
12-07-02, 10:35 PM
If your technically inclined and have the time and money to invest into learning how to care and feed for a forced induction motor, I promise you won't be dissapointed.

Otherwise, stick with the simplicity of a naturally aspirated motor. In both cases More Cubes are better.

My Vette has a NA 383 (390RWHP) and my Z28 has a SC 383 (510RWHP).

Both are a total blast to drive.

CYa!
Mako

Evolution1980
12-08-02, 05:34 PM
In my completely novice opinion...

Safer? That's relative. Safer in what regards?

Cheaper? Nitrous (you didn't list it). Supercharger gets 2nd place.

More Efficient? Bore & Stroke

Easier to do? Supercharge

I think it's all about effieciency. But it could probably be argued in many ways. I myself would tend to modify the engine first (stroke it to 383, change the heads & cam), then once the normally aspirated ("NA") is maxed out as far as safe tolerances, then I'd go to a supercharger.

If you are just looking for some quick go-fast juice, throw a nitrous system on it. The downsides to NOS is that it can get expensive if you have a thing for keeping the juice on, as well as improperly done can do irreversable damage to your engine and do it fast at that! But if you get a moderate progressive system (say 100hp or less), that may be enough for you if it's only an occasional yearning... "Progressive" means that it doesn't just open up the tanks full blast. It increases the NO2 shot along with the needs of the engine, which I believe is better and safer for you, your car, and your wallet.

Edmond
12-08-02, 06:13 PM
I ruled nitrous out because it just seems to dangerous for me. I don't like the idea of having more explosive materials on board.

From the reading that I've done, a supercharger can be put on yourself at home in about 8-10 hours with the basic tools right?

When I said safer, I meant in regards to the safety of the whole auto. Which one will cut my auto life shorter barring an accident.

BigRed
12-08-02, 07:24 PM
IMHO

No one is happy with what they got LOL :L

Turbo's are not my cup of tea

Superchargers are wonderful however your going to hurt the motor because we did not upgrade our bottom end for the increased power/torque.

Bore and stroke => Step 1 then supercharge LOL :L

Edmond
12-08-02, 07:56 PM
Originally posted by Mako
If your technically inclined and have the time and money to invest into learning how to care and feed for a forced induction motor, I promise you won't be dissapointed.

Otherwise, stick with the simplicity of a naturally aspirated motor. In both cases More Cubes are better.

My Vette has a NA 383 (390RWHP) and my Z28 has a SC 383 (510RWHP).

Both are a total blast to drive.

CYa!
Mako

That Z28 is street legal right? How does that drive in the street? All that power must be very difficult to put down on the pavement cleanly.

Mako
12-08-02, 10:59 PM
Originally posted by Edmond
That Z28 is street legal right? How does that drive in the street? All that power must be very difficult to put down on the pavement cleanly.

Yep it is. Drives like any other Camaro pretty much, until your right foot gets all itchy, than it's yeeeehaaaaw time :) I am running the stock shocks with stock rear springs, what are called 1LE front springs and 1LE sway bars and subframe connectors. This is a pretty mild street friendly combo.

The 1LE Camaro was the tire and suspension package for racer boys direct from Chevy, kinda like a Z06 without the hot bullet under the hood.

The tires are way over matched (17x275 SZ-50's), it's almost like driving a Zamboni above 4000RPM - the rear end justs floats around :) It's a wonderful "problem" to have I promise you.

The Vette blows the tires away as well, but being a 100HP down, it's just not as enthusiastic about it compared to the Z28.

CYa!
Mako

dry sump
12-09-02, 02:27 PM
You've got to start at the bottom. Steel crank, rods, etc. Then you can add the juice on top. Remember "there's no replacement for displacement".

Vettelt193
12-09-02, 02:33 PM
The old theory is there is no replacement for displacement.... but, with the new engines today, with every part fabricated to closer tolerances than ever before, supercharging is usually perfectly safe.
In the good ole days, it wasn't nearly as safe (as far as longevity is concerned) to supercharge or turbocharge an engine... most people still think back to those days really...

The only place the old displacement theory is completely correct is between two equally set-up engines... a supercharged 383 will have more power than a supercharged 350, etc.

55 Hotie
12-09-02, 04:42 PM
Re: nitrous being an explosive.....
What Nitrous does is chemically increase the amount of oxygen in the combustion process....It is not an "Explosive"per se. When Nitrous is used, the amount of fuel has to be dramatically increased to support increased combustion, and keep the nitrous from acting like a bellows and melting those expensive aluminum pieces....
A lot of people don't understand the difference between Nitrous and Nitro....Nitromethane. Nitromethane is the fuel that is used in Top Fuel, Funny Car and pro mod motors...If it is ever used in a street motor, it is an anomolie.
A mild shot of nitrous on an unmodified engine would provide a noticable increase in power without damaging the engine, but you know the old saying, if some is good, then more........
I have two nitrous setups in my garage, and one of these days i'm going to build the ultimate small block sleeper, but until that happens, I'm building an old reliable bulletproof 355 Roller motor with a B&M supercharger...Should make only about 495 Horses and 470 ft/lbs torque...That should be good enough to handle most rice and almost all 5.0's
Thadd

Evolution1980
12-09-02, 04:48 PM
Originally posted by 55 Hotie
I'm building an old reliable bulletproof 355 Roller motor with a B&M supercharger...Should make only about 495 Horses and 470 ft/lbs torque...That should be good enough to handle most rice and almost all 5.0's
Thadd
I should hope so! :L {End of tangent}

Ken
12-09-02, 04:52 PM
I'll just insert this again since Thadd brought it up. ;)

Check this post I put up back in April of this year: Curious about Nitromethane? (http://corvetteactioncenter.com/forums/showthread.php?s=&threadid=11360)

_ken :w

55 Hotie
12-09-02, 05:05 PM
Edmond;
To add fuel (so to speak) to the fire, the best of all worlds is a large displacement mild engine with a supercharger putting out mild boost!!!
Cost and your level of ability to build an engine come into play. To do it properly, one should buy "good" parts. A 383 is an easy and relatively inexpensive motor to build. I personally have built seven or eight of them, and if I were to build another one I would use some time tested pieces. I have found that a cast crank will be adequate in all but the most radical street engines...Pink 5.7 or Powdered metal rods will work fine especially if the fastners are upgraded. If there was any kind of a chance that I would supercharge or use nitrous, I would Forged pistons...A set of Hypereutectics go for around $280, the last Forged that I bought were Ross, and the were close to $600...But there are other forged pistons that are cheaper.
Many speed equipment manufacturers sell "rotating assemblies" that are crank, rods, pistons, pins, rings, bearings, and in some cases gaskets and cam shaft and timing set. I've seen them with forged pistons and a stroker crank for well under a grand.
Camshaft selection is an arcane science. Once you determine your combination, call your favorite cam grinder and tell them what you want to do.
It is also possible to built really big small blocks. A 400 block bored .030 over and stuffed with a 4" stroker crank comes out a 434 cubic inches.
I built one of these for a kid with a third gen Camaro, and he ran low 12's his first time down the drag strip...On radials through the mufflers. That's impressive and fast !!! That motor is now in a 67 Camaro and it runs low 11's on drag radials....
I didn't mean to write a novel...sorry

55 Hotie
12-09-02, 05:06 PM
Hi Ken...I thought about you today as I was driving past Ruby's...How's things ????
Thadd

Edmond
12-09-02, 05:10 PM
Thadd,

So what you're saying is that a very reliable and powerful combination would be a mildly built 383 + a supercharger with mild boost?

As for what I want to do with a car like that, it won't be for the drag strip. It would be used for everyday driving, with very little expressway driving. The power would be used for passing and occassional "fun.":D

dry sump
12-09-02, 05:18 PM
Built a few small blocks for SCCA. Had the parts for a 422 SB but never got it together. I like the idea of a strong 383 and add the goodies as the money rolls in!!
Right now a mild 427 is good for me.

Edmond
12-09-02, 07:56 PM
I see quite a few people have voted, but I also want to hear your reasoning behind your vote. I need knowledge!:D

bradfordsvettes
12-09-02, 09:46 PM
i believe you would have less plumbing with a super charger and a more flat torque curve because it is is always pumping and less under hood heat . the turbo needs to spin up before hp increases start lots of plumbing lots of extra heat. no substitute for cubes but both a super charger and turbo can be added later . and add ons are always novel . if the boost is kept within reasonable limits longevity is not a real problem . remember turbo regals,typhoons and syclones to name a few and a lot of gm cars are super charged these days regal ,grand prix, bonnieville and buick ultras only my 2 cents steve:w

55 Hotie
12-09-02, 10:59 PM
I guess that I wasn't as clear as I could have been...If I were in your position, I would build the 383, but build it using quality pieces so that I could supercharge it at a later time. I prefer the supercharger route to the turbo because of the plumbing issues, and there are bolt on supercharger kits available for a ton less money.
A torquey 383 will float your boat, and adding a supercharger will make you exstatic to the point that none of your friends can stand to be around you, but your car will be BAD!!!!!!

55 Hotie
12-09-02, 11:01 PM
And Edmond, how did you get my picture to use for your avatar ?????

Edmond
12-10-02, 10:58 AM
Originally posted by 55 Hotie
And Edmond, how did you get my picture to use for your avatar ?????

I went to your house and took the picture!:L :L :L

Vettelt193
12-10-02, 11:35 AM
This debate is also driven by money.... the ultimate question is, how much do you want to spend, and how much power do you want? A side factor is gas mileage and drivability....

If all you want is an extra 100 HP, and the same drivability and gas mileage, then just supercharge or go with Nitros.

If you are looking for more than 100 out of your L98, then you will need to look into 383 for 'safer' power increases. But, with a 383 comes lower gas mileage....

IMO, It would be cost in-effective to build a mild 383 and add a mild supercharger. superchargers aren't cheap, and re-builds or new engine builds aren't either. When you factor in time (either your own or a mechanics) you realize it takes the same amount of time to build a fairly wild setup 383 as it does a mild 383. The cost of parts doesn't go up that much either, from a mild to 'fairly' wild 383. Also, the price of a supercharger won't change much, if at all, from mild boost to big boost. So, while a mild 383 with mild supercharger will yeild very reliable results, with fairly good gas mileage, you will pay a fortune to get that set-up.... this is why most people with 383's just have a pretty wild 383, with no blower, or they wind up keeping the engine closer to stock with bigger boost.

Monty
12-10-02, 04:46 PM
Originally posted by bradfordsvettes
i believe you would have less plumbing with a super charger and a more flat torque curve because it is is always pumping and less under hood heat . the turbo needs to spin up before hp increases start lots of plumbing lots of extra heat.

Sorry, but you have that reversed - turbos produce far more torque than a supercharger (centrifugal). Since a turbo is not rpm dependant like a supercharger, but rather load dependant, it builds boost based more on throttle position. A properly sized turbo can produce boost by 2500rpms or so depending on the turbine, and maintain that boost throughout the rpm range. Of course it's going to be more efficient at some point within that range and less efficient at others. Conversely, a supercharger typically doesn't start to produce maximum boost until 80-90% of engine redline. As a result, the turbo will have a far superior torque curve and have much more area under the curve.

bradfordsvettes
12-10-02, 09:00 PM
----------Turbo vs. Supercharger


http://www.superchargersonline.com/techarticles_detail.asp?RecordID=13


----------------------------------------------------------------------

While the supercharger is generally considered to be a better method of forced induction for most street and race vehicles, the turbo will always have its place in a more specialized market. Superchargers generally provide a much broader powerband that most drivers are looking for with no "turbo lag". In addition, they are much easier to install and tune, making them more practical for a home or novice mechanic. this was off their site This is a great site superchargersonline .com much more info there. I was not saying a supercharger makes more power it is just the power curve is more flat and even with out turbo lag . I have driven and worked on both and they each have their benifits the super charger is better on the street i feel but nothing like the feel of the turbo spooling up it is neck snapping ,but the supercharger feels much the same all the way from idle till when you step on the go pedal so I still think my post was correct Steve:w :beer :_rock :upthumbs

bradfordsvettes
12-10-02, 09:13 PM
monty is that enine in your car now sounds awsome they all sound scary when doing a pull makes me cringe :eek :J Steve

Bullitt
12-23-02, 04:58 AM
Buliding a wild small-block would in all likely-hood have most people looking for more compression to use on pump gas. This would be in direct contrast with what a turbo or supercharged engine's require, which is lower compression. Basically, without getting too technical, the lower the compression (stay above 7.75) the more power either one of the forced systems can make. For superchargers, discounting highly specialized needs, the optimum should be around a 8.5:1 ratio. However, for reliabiltiy's sake, forged pistons are highly recommended. Basically, for any stout engine, you want a beefy bottom-end. Superchargers and turbos demand it! And you still have to use quality fuel.

Once I get back home, unless circumstances change, my mind has been made to build my engine in preparation for a Pro-Charger supercharger. After talking with a few racers that are currently using their system, I'm convinced that not only is it a good product, but it's priced just right. My main problem will be hood clearance, but I have seen a '66 Stingray outifitted with one, albeit with a Grand Sport hood.

I know of no company that makes a competitively priced turbo system for my big-block and would let me retain my side-pipes. I'm sure I could modify a system if I wanted to, but want to finish my "engine stage" in a timely manner.

--Bullitt

--Bullitt

Monty
01-07-03, 04:10 PM
Originally posted by bradfordsvettes
----------Turbo vs. Supercharger

While the supercharger is generally considered to be a better method of forced induction for most street and race vehicles, the turbo will always have its place in a more specialized market. Superchargers generally provide a much broader powerband that most drivers are looking for with no "turbo lag". In addition, they are much easier to install and tune, making them more practical for a home or novice mechanic. this was off their site This is a great site superchargersonline .com much more info there. I was not saying a supercharger makes more power it is just the power curve is more flat and even with out turbo lag . I have driven and worked on both and they each have their benifits the super charger is better on the street i feel but nothing like the feel of the turbo spooling up it is neck snapping ,but the supercharger feels much the same all the way from idle till when you step on the go pedal so I still think my post was correct Steve:w :beer :_rock :upthumbs

I've also owned and driven both custom turbo cars as well as centrifugally supercharged cars, and to say the supercharger is generally considered to be a better method of forced induction for most street and race vehicles is biased, misleading, and blatently untrue. You have to look no further than what the OEM's actually produce to see that turbo's are overwhelmingly favored for street cars . Nearly all of the world's elite cars use turbocharging if they utilize forced induction - Porsche, Ferrarri, Lamborghini, etc. Even the mainstream OEM's are offering and favoring more turbo equipped cars - such as the PT Cruiser, VW Beetle, plus numerous Asian imported cars. Considering that an OEM's primary concerns are ease of drivability, cost, minimal warrenty claims, 100K mile warrenty's etc it's obvious why they chose turbo's over superchargers.

As far as racing is concerned, where turbo's are allowed they out number and outperform superchargers. Look at the NMCA/NSCA and NMRA classes that allow turbos, the supercharger guys and nitrous guys have either switched to turbos or they are whining that the turbo guys have an unfair advantage. As a result, the turbo equipped cars are required to run at a higher weigh in and they are also limited to smaller engine displacments to provide a level field so that the supercharger and nitrous guys can compete. Not only do the turbos outperform the supercharged and notrous cars, they are generally more reliable. Some turbo racers even claim to have competed the entire season without even removing the valvecovers. That's probably an exaggeration, but the fact is that the turbo engines are more reliable.

Before anyone mentions Top Fuel or Funny car as evidence of superchargers superiority over turbo's, remember that turbo's are banned by NHRA as a means of slowing the cars down and reducing the cost of racing. In Top Fuel and Funny car, it's not a matter of power, it's a matter of traction and clutch management. When the cars are already making 6000+hp and running 300+ mph, what would the incentive be for them to add a more efficient power adder so they can make more power. NHRA is trying to slow the Top Fuel/funny Carscars down, not make them faster. Plus, the fans expect to see flames and thunderous nosie when the cars race. Even if turbos would make the cars faster, the NHRA figures that fans would n't like them as much because the cars would be significantly quieter and less dramatic. While it is impressive that those guys are making 6000+ hp from a 500ci engine, or 12+hp/ci. Even more impressive was the fact that the 80's Champ cars were making over 1300hp with only 90ci, or almost 15hp/ci. Unfortunately, the turbo's were again banned in an effort to slow the cars down and reduce racing costs.

To say a centrifugal supercharger provides a broader power band is misleading and untrue as it depends on the turbo size and design. Sicne a turbo is load dependent, rather than rom dependent like a supercharger, a properly sized turbo(s) will spool up and provide significant boost (torque)at a relatively low rpm, and be able to maintain that boost throughout the rpm range. For instance, my engine makes over 700ft lbs by 3000 rpm and maintains that to over 7000rpm, peaking at almost 1000 ft lbs at 5100rpm on 93 octane pump gas. Conversely, most superchargers are designed to provide maximum boost at about 90% of the engine's redline. That same supercharger may not even be produce boost at 3000rpm, if it does, it's probably only 2-4 lbs.

Turbo lag is an overblown issue, especially on a street car with an appropriate converter stall (if it's an auto). With the turbo's available today, there is no reason that a V8 engine would ever have any noticeable or significant turbo lag. Unfortunately, most people hear about turbo lag and it gets blown out of porportion, or their only exposure to turbo engine's is through some small displacement import, Buick GN's, or some other domestic turbo that was built during the 70's and 80's. A V8 engine provides plenty of exhaust energy to spool up a properly sized turbo. Actually, in some cases some lag is desirable because it doesn't tend to overwhelm the tires as bad. With the 3200rpm converter I have, the engine is already making boost by the time the converter flashes and the car starts to move forward. Too much throttle too quickly and the tires light up - a little lag would make it a little easier to drive.


I also don't know where this myth that turbo engine's are hard to tune started - probably by people who don't know what they are doing. After I assembled and built my engine and turbo system, I took it to get dyno'd. Not only did the engine crank, and run on the first attempt, but on the very first dyno pull with no tuning other than setting basic parameters, the engine made over 1000 hp and 900ft lbs. Within 4 dyno pulls the engine was tuned and made over 1200hp/1000tqon 93 octane. It took less than 2 hours to tune the engine for maximum torque and horsepower, while it idles smoothly at 850 rpm. When I got the engine installed in the car and running, it took me about 30 minutes to tune the cold start enrichment, and TPS/MAP enrichments. That's less than 2.5 -3 hrs of tuning - hardly what anyone would consider difficult ot tune.

The only real advantage a supercharger has over a turbo, is that in most cases superchargers are easier and cheaper to install. Hwne cost and ease of installation are the primary concerns, go with a sueprcharger. If performance and relaibility are the primary concerns, go with turbos.

bradfordsvettes
01-07-03, 09:40 PM
That was my point that for the average person with a basicly stock car the supercharger is a pretty good bang for the buck .Plus there is not much of a need for a converter change unless your looking for a stall speed change. I am not knocking turbos at all but there is more work involved and cost. what is your opinion of the under hood heat issue .Obviously you have much more expetise in this field than I do.I am just your every day auto tech{ aka grease monkey}. It was just an opinion as to what would be the easiest conversion for a street car with a good seat of the pants feel .How does your car hook up with that power must be awsome. TURBOS FOREVER Steve :w :beer

sothpaw
01-09-03, 12:37 PM
Edmond,

Nitrous would be the cheapest way to get what you want, and
it's probably just as safe if done right. What I don't like is that
if your NOS installer does it wrong, you WILL blow the engine if you ever get a lean condition. And don't come crying to the NOS installer...

Supercharging: Good if you want 100hp, but won't help if you only
want to pay for 30-40. Plus, you're depending on some manufacturer to make a quality product. I've heard of belts slipping, etc, car is always in the shop. Do you really think if
the supercharge manu. sells a 1000 units a year and mostly to
racers that this thing is going to last 100k mi? Big auto companies
have so much more money to put emphasis on quality.

383: The simplist. Modify what GM made. Drill, hone. I think it will
have to be more reliable. Plus, if you only want 40hp, you don't
have to go full bore, so to speak.

Edmond
01-09-03, 12:42 PM
The 383 would be a project that I could do slowly right? I could get the motor punched .030 over with some nice flat top pistons. That would change my compresson ratio right?

If my compression ratio changes, I should get my custom chip reprogrammed right?

Then I should port and polish the heads, get headers and so on right?

Are most projects like this done over time or pretty much done at once?

JRMaroon
01-09-03, 12:51 PM
My Cubic Inches vote was for the simple fact that I am the only one who knows what I'm running. Forced induction is awesome but how cool is it to have a stock looking car with nothing more than an intimidating exhaust note to tip your hand? People will be more curious about the car if they can't tell what makes all that TORQUE.

Jeff

KANE
09-15-07, 07:17 AM
Can you guys give me the benefits and downfalls of each?

Which is safer?

Cheaper?

More efficient?

Easier to do?

Given the choice, which would you do?

If you are looking to add some umph to your 88... I'd suggest a Powerdyne supercharger. TPI responds well to forced induction (example: Callaways).

I'd like to supercharge my L82/TPI set up. But, that costs $$$ and I think I'll wait a few years until I'm so bored I contemplate selling it that way it feels like a new car when I get done!
:L