Okay, so I have some questions about forced induction, and I was hoping someone would be able to add to what I know or correct me. I'm talking about if such an engine was offered as OEM equipment, not aftermarket. This is what I found out so far:

Turbocharger:

+hp up
+torque up
+does not draw power off the engine (therefore useful for small displacement engines)

-turbo itself must be maintained
-turbo engines don't last as long statistically?
-turbo lag
-a good turbine is expensive and adds significant cost to the vehicle's price
-uses extra fuel?

Supercharger:

+hp up
+torque up
+less maintenance required than turbo?
+no lag

-draws engine power (therefore requires larger displacement engines)
-may compromise engine life?
-expensive
-uses extra fuel?

I've always wondered why manufacturers (other than VW) were reluctant to offer forced induction on their mainstream cars (like Accords, Taruses, Civics, regular trucks, etc)

 

Turbo

Turbo systems use flow and exhaust pressure instead of a belt driven pulley and are therefore more efficient at generating horsepower and torque.

Boost is easily adjustable with an electronic switch to match your performance needs. No pulleys or belt changes are required.

Turbo systems are quieter when driving around town. Turbo noise isn't heard unless the boost is on.

Turbo systems can increase gas mileage because they make the engine more efficient and don't take power from the engine to make power.

Turbo systems are more reliable than belt-driven superchargers because there are fewer mechanical and moving parts.


Supercharger

Use belts driven by crank shaft to increase boost to the engine. It takes horsepower away from the engine to drive the supercharger.

To change the amount of boost you must change the size of pulley used by the supercharger.

Superchargers in general are noisy because the gear drive is always engaged, even at idle.

Superchargers generally decrease gas mileage because they are using the engine's power even when the supercharger is not producing boost.

Superchargers can throw belts causing damage to other components in your engine compartment.

Superchargers take up more room in the engine bay making it difficult to do some regular engine maintenance.

 

anything with forced induction should be Intercooled in my book.

Turbos and S/C'er produce alot more heat... so if you want the top half of your motor to survive, you should have an intercooler.... High heat = Increased engine wear/destruction!

 

Thanks for the insights. I completely forgot about intercoolers. Those increase the density of the air, thereby effectively increasing efficiency, right? (If I remember thermodynamics correctly).

Turbos seem to have so many advantages. This leads me to the question again about why they aren't widespread. I really don't think cost is a huge excuse, because the top trim level could be offered with a turbo on every model. Especially so since they can INCREASE fuel economy, as bdog has stated.

 

That is most often the case. However, certain cars and forced induction applications put out generally the same amount of power. The RSX-S for example makes about the same amount of power turbocharged as it does supercharged. Plus you have the exhaust flow restriction (the turbo) which hurts efficiency.
Correct, however with a turbo you run the risk of those "electronics" failing, malfunctioning, etc and overboosting which is potentially an instant motor killer.

Same for most superchargers. You hardly hear the supercharger on my car at idle. If the engine fan is running you dont' hear it at all. Plus, if your turbo system has a blow off valve, every time you shift you'll be hearing "pffffftt"

This one baffled me. To support the added boost you'll need more fuel. Period. I see no possible way how any forced induction system would INCREASE gas mileage.

Oil lines, overboosting, etc. A turbo is no more reliable than a supercharger. In fact superchargers are most often considered the MORE reliable option.


Supercharger
Correct

I suppose but they really aren't THAT noisy. As I started earlier you can hardly hear mine.

Yes but as I said above the fuel needed to support the boost from a turbo or a supercharger is about equal.
A piece of rubber isnt' going to damage anything I'd rather throw a belt than blow an oil line and catch the car on fire.

Totally depends on the application. Just because the compressor may be smaller on a turbo charger, you still have all the intercooler plumbing with an intercooler than you don't normally see on a supercharger.

 

One thing i'll also add is this:

Based on the datalogs that I've studied on the Hondata K-Pro for both turbo and supercharger applications on the RSX-S, turbocharged engines are under boost MUCH more than supercharged engines. 95% of the time a supercharged car is not under boost because the bypass valve is open. When you aren't under boost the only additional strain you are placing on the engine is turning the blower shaft (which is about 10hp with the bypass open).

 

Oh and BDog nice use of

Great cut and paste job from a site that SELLS turbochargers. Obviously they will weigh the pros vs. cons heavily in the turbo's favor

http://www.ststurbo.com/turbo_vs__supercharger

 

I guess we need to be more wary of misinformation...thanks for the catch.

 

So essentially running a supercharger would affect fuel economy in the same way that running an air conditioning compressor would, right? Plus a little extra from the ECU sensing the increased air density, requiring it to put more fuel through the injectors.

 

That is not a good comparison... it is all in how you drive the car... lead foot will determine your gas mileage when talking about forced induction & injectors... There are devices that show the OEM ECU no boost, if it sees boost, it will retard timing and the car will fall flat....

 

you should always be very leary of what you read on the intra-web......

Steveo enjoys owning peeps.

 

especially when they make it easy :gheylaugh:

 

Bdog =

 

Yeah...that original comparison seeemed to be waay in favor of turbochargers when in fact, they both have their equal ups and downs.

 

Almost every turbo or supercharger kit comes with or requires a new fuel pump or fuel system.

Which makes sense because unless you want to run extremely lean, more air = more fuel to keep a correct AF ratio.

 

I think one of the reasons turbocharging isn't more widespread is indeed cost. Perhaps not in the system itself, but in the additional cost of maintenance and potential repairs. Turbochargers themselves are fairly reliable themselves but only if properly maintained and cared for. Proper warm ups and cool downs. Frequent oil changes. Proper fuel requirements to prevent detonation. Fuel management issues. I've had a few turbocharged vehicles and each of them have required additional care and attention. Admittedly nothing recently, and it appears that as turbocharging becomes more common the additional maintenance and precautions are much more relaxed.

In regards to fuel economy I'm not sure if this is entirely true. Turbocharged engines can become quite thirst once boost is created. And remember a turbocharged engine can feel particularly flat when not creating boost due to the lower compression ratios required for turbocharging, thus resulting in a more aggressive driving style and of course more fuel use. My Grand National runs 10's on race gas and 22 lbs. boost, but rather doggy if not creating boost (while, not quite).

 

Just like you Googled to find the same information, basically those were points I was going to say, so a Google and cut and paste was easier. They weigh their pro in favor of turbo's because turbos are more reliable, easier on engine and can produce more power.

 

I didn't Google anything. Everything I posted is based on first hand experience.

Smitty Im'ed me and said... "That post before you is definitely a cut and paste" so I looked it up.

Elaborate on how turbo's are more reliable, because by no means are they IMO. Also, they are not easier on the engine as I stated because the engine is under boost more often and as I also said, based upon the application a supercharged car can make the same amount of power as a turbocharged car.

 

Okay don't have to get to work yet so I'll go on...

IMO, a turbocharger has many things against it compared to a supercharger when it comes to reliability.

1) Turbos are oil cooled (sometimes oil and water cooled). While the engine is running the oil is flowing through the turbo and back to the oil pan. Once you shut off the engine the oil is no longer flowing through the turbo, however some oil remains inside the turbo. This oil that once was flowing across the turbo's bearings to cool them is now actually baking the bearings in hot oil. Not a good thing.

2) Although turbos only have 1 moving part (the turbine shaft) which spins with the impeller. Superchargers have more moving parts (shaft, gears, impeller, etc). Although most superchargers (screw-type) spin no faster than 16,000 maybe 18,000 rpms. A turbine shaft can spin upwards to 100,000-150,000 rpms. Which bearings do you think are going to last longer?

 

Supercharging seems like a quick and dirty way to get additional power from an engine. If it's so advantageous, why don't we see it on top trims of models?

 

I didnt' mean you googled your posts, just where you got the link to my c/p on my post. Again, my post was pro turbo and those points there were valid.

Anyway, you will have pro's and con's on both types of units. There are 3 main types of superchargers and on type of turbo. The drawback to a turbo is you shouldn't just turn the car off, or as in your other statement the oil may bake inside it. You should get a turbo timer or let it run for 30 seconds or so at idle before turning it off. I didn't have a timer on my car and shut it off as soon as I stopped, but I never had any problems (8 lbs of boost. 134,000 miles on it) at all.

Cost is about the same either way and if you take care of your car either induction system should last a hundred thousand miles or so. It used to be just the Thunderbird SC, but you are starting to see some S/C'ed factory cars again. Cobalt, Lightning, GT500, but IMO I think most manufactures use turbos because of simplicity and reliablity. I can't prove one is better than the other, just point out pros and cons and have an opinon.

 

1) And of course the oil itself can overheat and harden. Commonly referred to as "coking".

2) Basically correct, but the new turbochargers are engineering feats. Some new turbos use fluid bearings, which allows the shaft to rotate within a layer of oil to both cool the shaft and reduce friction and wear.

Turbocharging and supercharging both have their advantages and disadvantages. For myself, the ability to "dial up or down" the amount of boost with a turbocharger to meet specific requirements has the greater advantage.

Terry

 

Steve:

Perhaps I'm not misinterpreting your post, but how is turbocharging hard on an engine? Currently I have one of each type of forced induction: an 86' Grand National and 03' Lightning. Turbo systems are not always creating boost. If so, then the need for correct plumbing and proper positioning of the turbo itself to combat turbo "lag" would not be required. Also turbos are free-wheeling and do not connect to crankshafts of other engine parts. A turbocharged engine requirement is to low compression (my GN is roughly 8:1) and unless the system is creating boost the internal pressures are reasonably low. In fact I enjoy driving the Lightning more on a day to day basis as it power delivery with the supercharger is much more linear and fluid compared with the on-off power delivery of the GN.

Terry

 

So this is why you can't turbo most honda engines right? The compression ratios are at MINIMUM 9.7:1 even in a 4cyl Accord. And 11.0:1 in the TL. I recall that higher compression engines are more efficient (from thermodynamics).

 

TL:

Absolutely correct. I suppose one could if so inclined, but the cost of a turbocharger to supply only a few pounds of boost wouldn't be of benefit. Superchargers are much easier to apply to engines with relatively normal compression ratios. Many superchargers are capable only of 8-10 lbs. of boost. In my Lightning I have an smaller diameter pulley than factory to supply about 11 pounds of boost. An aftermarket chip was required as well for fuel management. This allows for close to 500 hp, but without major modifications to the engine (lower compression) I cannot increase boost.

The GN on the other hand runs 22 lbs. in race trim. And if I'm not too concerned about detonation I can probably bump to another couple pounds. I see you're from Edmonton, so you may have seen a few turbo Regals run at Budweiser. Two summers ago one from Mission BC ran consistent high 8's.

Terry

 

For a motor designed for boost, such as your Grand National, it isn't nearly as hard on the motor. Same for your Lightning. That motor is designed with the supercharger in mind (a great design I must add).

And you are correct turbo systems are not always creating boost. However, based upon the one car from which I can easily compare datalogs (Hondata) from turbo and supercharged cars (the RSX-S) the turbocharged cars are under boost much more often during daily driving.

My posts and opinion is based upon adding a "kit" (turbo or supercharger) to a car that wasn't originially designed for boost. The added heat from either a turbo or a supercharger (god I know how much the IAT increases with the Comptech kit) will increase the rate at which the motor (the heads specifically) will wear down.

 

You are correct. However, adding a small amount of boost to a high compression engine will create much more power than the same amount of boost on a lower compression engine. For example. One of the turbocharged CL Type-S's is running 5.8psi of boost on the stock motor (10.5:1 CR). He is putting down 420whp. No other modifications. Just the turbo kit (turbo, manifold, 7th injector, intercooler, etc), exhaust dump, and fuel management via the GReddy e-Manage. The e-Manage is only used to retard timing, add pulse width to the stock 270cc injectors, and control the 7th injector (I believe it is a 750cc). Boost is regulated via the wastegate spring. 5.8psi of boost on your Grand National for example would create a very minimal increase in horsepower.

Making power with less boost (i.e., high compression and timing retard) is great IMO. Sure alot more power could be made on lower compression motors (i.e., Dodge SRT-4 or the EVO8) because you can run more boost without the timing retard to avoid detonation.

 

Turbos scare me because what if while you're on the highway at cruising speed, your engine happens to be spinning at just the point that the turbo engages, causing MASSIVE fuel wastage. This is what happens in my friend's 91 Skyline (imported). It gets worse fuel economy than many trucks on the highway if he runs into the turbo range, so he has to drive slower than everyone else.

MrSteve, thanks for the informative posts. I wonder if Honda would ever consider supercharging the RL to quiet down the naysayers? I doubt it.

And what's the point of twin turbos? Just to put in more boost? Why not use a higher compression engine with a single turbo?

 

Not necessarily. Adding large amounts of boost to an engine of average compression will always lead to detonation. Therefore you are indeed limiting its potential. So by the examples stated by both of us, wouldn't it be more advantageous to turbocharge a lower compression engine with moderate amounts of boost than a regular compression engine with nominal boost? As mentioned, the advantage of a turbocharger is the ability to dial up or down, something not easily done with a supercharger.



Terry

 

Admittedly I'm not familiar with these systems Steve. I imagine an aftermarket kit would most like have an turbo of small inertia to create a nominal amount of boost on basically a factory engine. In regards to the Lightning, I've experienced an overboost situation. A set of cylinder heads later..............

You guys have me all worked up now and I may actually replace the water pump on the GN this weekend. Or maybe not.

Terry

 

Again, higher compression engines do NOT react well with moderate amounts of boost. They are very much limited in their potential. It is more advantageous to turbocharge a lower compression motor. And certainly the potential for much more power than a higher compression motor with nominal boost. Now all that being said, turbo lag is the enemy of any turbocharged engine. If one wants to create massive amounts of power then a larger turbo is required. BUT a larger turbo is of large inertia, taking much more time to spool up and resulting in the dreaded "lag". Now take two turbos, both of smaller diameter than one large turbo. Position and electronically control them the function sequentially, that is one creates boost first then the other. Or electronically have them functioning together but only creating small amounts of boost. You then have a turbocharging system that creates boost much sooner than one large turbo. The end result may be the same between two small diameter turbos and one large one (say 20 lbs.), but two smaller units have the ability to be much more drivable. Quicker spool up. Quicker response. Flatter horsepower and torque curves. Do a search on factory high performance turbocharged engines, you'll be amazed at how low the compression ratios are. Herein lies the tremendous potential of turbocharging.

Terry

 

Define "moderate" amount of boost. On my first CL-S (automatic) adding intake/headers/exhaust gave me an increase of 25 horsepower at the wheels. Adding 6psi of boost (supercharged) on top of the "bolt-on" modifications increased my horsepower by 73 at the wheels and torque by 65 ft-lbs for a total of 295/243. Not bad for a car that dynos 190-195 in stock trim.

I now own a 6-speed CL-S that is also supercharged. I have yet to dyno it but give the same amount of boost with less loss through the manual transmission it should go from dynoing 220whp stock to 330+whp at the same boost level.

100+whp from 6psi is pretty substantial in my book. Unlike a turbo I can't get the highest numbers possible but the supercharger on my car continuously builds boost and is great for everyday driving.

 

Damn, now I'm tempted to supercharge my 2.5TL!

That's a substantial amount of power for such low boost.

Too bad nobody makes one for it. And I'm getting a 2006 TL in August 2006 (I think I'll choose a TL), so it's pointless right now hehe.

 

Hi Steve

Not sure if a pre-determined number can apply to "moderate" boost, but in this discussion lets say anything under ten. You mentioned a friend of your who has a CL-S with 5.8 lbs running about 400 hp. Probably around 10:1 compression. Very impressive. I'm not sure of the displacement, being new to Honda products, just recently purchasing an 05' Accord Coupe six-speed. I would assume the car you refer to is a three litre as well. Correct if I'm wrong. You are correct that with the equal amount of boost my GN would feel somewhat slow. I would imagine 275 rwh. I'm running factory displacement and the factory bottom end. Car displaces 3.8 litres, relatively close to your friend's. The car was manufactured with 7.2:1 compression. Now with my cylinder head work, dump, 4 row intercooler, 100 lbs. plus injectors, AND t-76 allowing max at 24 lbs., not allowing any atmospheric conditions, I run a solid 700 hp with absolutely no detonation. And if I ever have the balls I can probably jump a couple more pounds. And this is nothing compared to the stage turbo Regals running around. There was a short clip circulating around some time ago where a modified GN actually beginning spinning ON the dyno.

Again, you are correct in the assumption that if two motors, one of 10.1 compression and one of 7:1 compression, and equal amounts of boost, then the 10:1 car would most like produce the most power. But that car is most like at its limit for forced induction. The lower compression car could readily accept more boost, allowing for more power. Of course such issues as injectors and fuel management would need to be addressed, but certainly not that difficult with today's turbo link setups.

Terry

 

Absolutely lower compression is always more boost friendly.

The CL-S is a 3.2L motor and runs 10.5:1 compression. The J-series motor is very boost friendly. I'm on my second supercharged Acura CL. I run stock injectors with a higher flow fuel pump, a rising rate fuel pressure regulator, and a voltage clamp to keep the ECU from seeing boost and retarding timing. That's the only tuning required on my car. In cold weather I would see boost increase to 7-7.5 psi because the Eaton blower is much more efficient and the air is more easily compressed with colder ambient temps.

Adding an air/water intercooler (similar to the one on your SVT) has been done on the J-series. This allowed for 9psi of boost using the Eaton MP62 blower. That's using stock injectors and minimal tuning for added pulse width and about 4 degrees of timing retard. This set up is good for over 370whp on the manual transmission equiped CL-S's. That's on stock injectors and stock motor. IAT values are also kept within 20 degrees of ambient which is a very good thing for eliminating stress on the motor from the added heat produced by the blower.

 

They sound like stout little motors. I don't have any plans for my six-speed, other than the Borla cat-back I just ordered. I find it interesting that the GN has a knock sensor, where the SVT. manufactured close to twenty years after does not. An interesting quirk is that the 5.4 cylinder heads allow for only about two revolutions for each spark plug, often working their way out under boost. And yes, I know this personally..............

Terry

 

Does your SVT sound like this one?

http://photos.imageevent.com/mrsteve...1-05%20SVT.wmv

 

Here's a quick in-car clip of my old CL-S

http://photos.imageevent.com/mrsteve...S%2020-110.wmv

 

Hi Steve

Having trouble downloading the last clip. Lightning clip worked, however, and was great to see. Mine sounds similar, but perhaps a little more "hooverish". I'm more impressed with the way it hooked. Awesome.

I'm curious if you had to perform any additional driveline modifications to your CL. Clutch? Transmission?

Terry

 

Transmission cooler was added to the automatic CL.

The manual transmission and clutch has been proven to hold just fine. No upgrades needed.

Try this:

http://photos.imageevent.com/mrsteve...S%2020-110.wmv