Im new to the whole supercharger and turbo scene. I was just wondering if and when a supercharger comes out for the rx-8 will it lower engine life or have any other bad side effects. Im planning to go on a lot of long trips back and forth from college to my house. Also do u guys think mazda dealers will install the super or turbo for you, so the warranty wont get voided.


Sorry for the noob questions

 

there's been a lot, and i mean a LOT of discussion about it so far... considering the amount of info we have, the vast majority of which is purely speculation.

people have said a turbo will be difficult due to the exhaust manifolds...and that a supercharger isn't as good over all the revs, but with either option, the renesis has a 10:1 compression ratio...that doesn't leave a whole lot of room for boost =p

so, keep yer panties on. the car ain't even out yet and it'll be a good while before any kits come out, then you'll get a bunch of owner reviews and can decide for yourself.

 

Often times you will decrease the compression ratio with FI to give better reliability, and I would guess they would do that (by using different rotors) if they supercharged/turboed (sp?) the Renesis.

 

It is against Federal Law for a Dealer to refuse a warranty claim because an aftermarket product has been installed on your vehicle. If a warranty is denied, contact the Environmental Protection Agency (EPA) at (202) 260-2080 or www.epa.gov or the Federal Trade Commission (FTC) at (202) 326-3128 or www.ftc.gov. Additional information is available at the SEMA (Specialty Equipment Manufacturers Association) website www.sema.org.

However, a warranty claim can be denied if the aftermarket product caused the problem that prompted the claim. So if you turn up your boost to 80 lbs, and your apex seals shoot through your hood, the engine won't be covered. But, if you installed a super charger, and your brake master went south, they cannot deny the claim. There is a grey area, however, like if your tranny or rear end go out but the boost was set to normal, better hope you can debate well!

 

"Where there is a will, theres a way" an cliche that aftermarket tuners live by... they also get paid for it

 

ENGINE RESPONSE:

TURBOCHARGER
The Turbocharger does not reach its maximum efficiency range until high speed and airflows are achieved later in the vehicle acceleration event. The latest Turbochargers with variable geometry housings and ceramic turbines still take four times as long as a positive displacement Supercharger to produce maximum boost.

SUPERCHARGER
The Supercharger is continuously driven at full boost speed for the given engine speed. This offers almost immediate boost response which takes approximately 0.4 of a second to produce 50 KPA boost.


EFFICIENCY:

TURBOCHARGER
Turbocharger airflow delivery characteristics do not match the requirements of the internal combustion engine because of the volumetric efficiency versus speed difference. Turbochargers only display efficiency over a limited flow range. Turbo systems must be compromised to provide some low speed boost while matching high speed flow requirements. This usually requires wastegating which reduces maximum power.

SUPERCHARGER
The Supercharger exhibits an airflow delivery characteristics very close to the engine requirement. Thus, boost remains almost constant over the total speed range without wastegating or other compromising control systems.


NOISE AND DURABILITY:

TURBOCHARGER
With Turbos driven by exhaust gases turbine noise is nearly eliminated. Durability cycles are affected by the extreme temperatures that the turbine and housings are subjected to, leading to fatigue and inevitable failure.

SUPERCHARGER
Supercharger noise along with durability concerns have been the expressed reservations associated with automotive use. With improved designs and advanced materials noise levels have been reduced considerably with durability cycles proven well in excess that of Turbochargers.


LUBRICATION:

TURBOCHARGER
Turbochargers are subjected to extreme temperatures and in "shut down" situation the oil remaining in the turbine bearing sections will reach coking (burning) temperatures. The carbon build up in the engines lubricating system will accelerate the internal wear of the engine and add to the rapid deterioration of the oil.

SUPERCHARGER
Superchargers can be lubricated by self contained systems which without the extreme heats experienced by Turbochargers will last for periods well in excess of the engine lubricants.


AFTERCOOLING (INTERCOOLING):

TURBOCHARGER
Turbochargers again are subject to extreme temperatures and discharge temperatures need lowering through aftercoolers if high performance levels approaching that of Superchargers are to be reached.

SUPERCHARGER
Superchargers do not require aftercooling as outlet temperatures rarely exceed 140 degrees C.


DRIVEABILITY:

TURBOCHARGER
Unlike a direct coupled Supercharger, performance is only enhanced in proportion to turbine speed. Therefore performance at low speed is limited and a distinct pause is encountered under acceleration known commonly as Turbo lag.

SUPERCHARGER
Performance is obtained without sacrificing the practical and constant rate in which this torque is delivered. Towing and Off Road-4-Wheel Driving can benefit greatly from the increased torque at low speeds.


EXHAUST EMISSIONS:

TURBOCHARGER
Turbochargers can be tailored to meet emission levels at normal operating temperatures but suffer on cold starts. Contrary to the heat generated by a Turbo the exit gases are still low and on cold starts results in a longer catalytic light up time. This results in unacceptable levels of exhaust emissions at engine start up and legislation is slowly reducing the light up period available which will create problems for Turbochargers.

SUPERCHARGER
With legislation increasing pressure on automobile manufacturers to generate clean running engines Superchargers can easily be tailored to suit engine manufacturers emission designs.


VEHICLE MODIFICATIONS:

TURBOCHARGER
A Turbo becomes an integral part of the exhaust system, therefore requiring major modification to the standard exhaust. This also is the single limiting factor dictating its position in relation to the inlet manifold. Additional pipe-work can be required to reach air cleaners and inlet manifolds when mounted on the opposite side of the engine. If an aftercooler is incorporated the potential piping requirements can become impractical. Turbochargers fitted to some vehicles needs to be insultated with a heat-shield lagging to protect under-bonnet-components from the extreme temperature generated. Brake
master cylinders have been known to melt in a Turbocharged vehicle which raises other problems. Internal modifications are required in some cases such as compression modifications to accommodate the hot delivery air of the Turbocharger. Early opening of the exhaust valve will allow a high blow down pressure giving smaller engines more drive pressure from its exhaust but does sacrifice engine efficiency at cruise due to loss of full gas expansion.

SUPERCHARGER
A Supercharger need not change the physical configuration of a motor vehicle. A Supercharger is fitted where convenient by brackets and drive belt. Standard air cleaner and exhaust stay intact. No internal modifications to engines are required as the extra boost delivered is at a moderate temperature and which reduces the chance of detonation. No heat shielding is required for under-bonnet-components as again operating temperatures are low. No excessive plumbing required as Superchargers do not require aftercoolers and the unit can be mounted near the intake manifold requiring only a short discharge pipe.


MARKET TRENDS:

TURBOCHARGER
Manufacturers have worked with or around the inherent problems of Turbocharging in the pursuit of performance, economy and emission controls. Now with other options available Turbocharging is becoming less important to many vehicle manufacturers.

SUPERCHARGER
Supercharging is becoming more widely accepted by original equipment manufacturers and different forms of Supercharging are now appearing on new vehicles.


SUMMARY:

In the past Turbocharging has been an accepted means of increasing engine performance. Even with its inherent problems it was the most cost effective method of forced induction. Now with improved manufacturing techniques and high volume production Superchargers can now not only offer better performance and packaging characteristics but can also now be price competitive.

 

That settles it for me. I was trying to figure out a way to haul a trailer while I off-road with my RX-8

 

I don't even like turbochargers due to their driveability characteristics but I just couldn't read this crap and be silent.

Where is your proof? Tons of turbo engines live for 100k's miles. A turbo will not thermally fatigue any more so than a freaking exhaust manifold on a supercharged car.

Coking is not true anymore with water cooled turbos and higher quality oils.

In fact the opposite is true. At any boost pressure a centrifugal compressor is more thermally efficient than a Roots or a Lysholm. At 5 psi a turbo will heat the air less. At 10 psi, also. At 15 psi, also. And so on.

There is more BS but I am feeling too lazy to go into it.

 

I can't wait for a 6lb of boost supercharger kit to come out. That'll be enough for me.

At the same time, I think Supercharger here has clearly exaggerated the benefits to supercharging.

-Mr. Wigggles

 

Exactly.

---jps

 

Don/t forget, a supercharger is driven off of the crankshaft. At the top of the rev range a supercharger, depending on the type, can easily steal 50 bhp just to keep itself spinning. This is efficiency?

 

This discussion...hell argument, over which is better has been going on for decades. If you say that superchargers are more efficient over all, someone will say that they parasitically pull power off the engine to operate. If you say turbo's fail b/c they use the engine oil system i'll say they are fine if you throw on an oil cooler.

No matter what anyone says there's always gonna be a counter statement for the other. Would it surprise you if many people bought one over the other based solely on sound??? i bet about a quarter of people buy things in this way.

Personally i love turbo's. I just don't like the idea of another belt off the engine. But then again i love anything that can put over 100hp into an engine. Either way you dress it up you're looking at thousands of dollars.

Just b/c superchargers (may becoming) the accepted choice of forced induction does'nt mean they are better. Cars have been, and still are being turbo'd from the factory with literally just the manifold and turbo being the only parts to the system and driving for 100k+ miles.

You seem like your trying to sell superchargers or just love them

this is exagerated. Yes superchargers response time is faster but can you honestly perceive the difference b/w .4 seconds and .16 seconds?? Depedning on the size of the turbo you can have full spool by 2500rpms. For most people the speed at rpms below this mark are irrelevant anyway...unless you're building a drag car.

ok my rant is over. Basically it comes down to PERSONAL PREFERRENCE and application.

 

no, there is superior system, but if i say Super's wrong, he'll pull something ELSE out of that magical hat of his!! LOL!! :D

 

In my last post I dispelled BS and exagerrations of how superchargers are superior. Now I will do the opposite and dispel the exagerated 50 hp number above.

Modern street belt driven superchargers consume about 15-25 hp. Some high hp versions for V-8's may suck up 40 hp. 50 hp is an exagerration.

Also, the power to spin a turbo is not completely free. There are pumping losses the engine must endure to overcome the increased restriction of the turbine. Since a turbo is more efficient and since some of the energy to spin the turbo is actually free turbos usually have about 30% of the parasitic loss that a belt driven setup has.

Basically a belt driven supercharger that can pump enough air for 325 hp will have about 25 hp of pumping losses and have a crank output of 300 hp. A similar turbo system of 325 hp capacity will have a crank output of about 315 hp. So the difference in peak power is 15 hp. Remember, this is peak power only. At cruise (say 20 hp) the turbo will not be more efficient at all. The turbo will still have a small pumping loss will the supercharger will be bypassed and will only have about 0.3 hp of pumping losses.

 

Turbos suck, Superchargers blow

 

Originally posted by babylou: 50 hp is an exagerration.


Actually, it is much, much worse. It was a guess that I stated as a fact. Sorry. Although I bet a roots type blower could do it.

 

Just wondering out of the blue, but was there ever such an application where someone used a hybrid turbo\super charger? I was told it has been done but without good results. I was also told that done incorrectly the supercharger would just rob the turbocharger of its ability to boost. If you can get a setup like this to work imagine the possibilities. But then the whole setup would just be too heavy for practical applications.

 

yeah, Lancia had that in some of their Delta rally cars from the 80's (butt-***-ugly things), and i know for sure that HKS developed a "twin charger" system for the MkI MR2 (which had a supercharger, high power version)... just some random examples, i'm sure there have been other applications like this...

really, i don't see the point of having two things which do the same thing, where one works half the time, and the other doesn't... too much wieght, too many moving bits, too much cost... just make the freakin' engine bigger if you're that desparate!! :D

 

Yes hybrids have been built. However, instead of getting the best traits of both systems they seem to get the worst traits of both systems. Plus we are looking at an induction sytem that costs more than the rest of the engine.

 

Yes there are Roots blowers that can suck up 50 hp. Top Fuel drag cars have something like 500 hp parasitic drag. Of course I think they are pumping like 10,000 scfm whereas a 250 hp street car my be pumping 380 cfm.

The largest modern Roots blower, an Eaton M112, can pump about 660-680 scfm depending on boost pressure. At this flow rate the blower has between 28 hp (5 psi boost, maybe 5.3 l engine) and 44 hp (10 psi boost, say a 3.5 l engine) of losses. At this flow rate the engine output would be about 400 hp after parasitic losses.

 

i agree...the only application where a duel charger (turbo) system should even be used is in deisel big rigs. Since the deisel market drives the turbo industry they are now designing a twin turbo setup where, after the second turbo, total output is b/w 100-120 psi!!!! Did you know most big rigs rev limit to 2500rpms but have up to 17 forward gears?!?!?

 

Check the April '03 issue of Turbo & High Tech Performance magazine (www.turbomagazine.com). They have an article about "Compound forced induction" as they call it.

From the article:

Roots Advantages
-Instant boost on throttle application
-Good low-rpm boost (with by-pass valve) zero charge heating at idle and high vaccum cruise
-Good and linear volumetric efficiency

Roots Disadvantages
-Excessive heating at higher boost (over 8-10 psi) due to reversion-pulsed turbulence of non-compressed air from the supercharger encountering higher-pressure previously compressed air in the intake
-May be inconvenient or impossible to intercool
-Robs some of the power it produces from the crankshaft
-Can be noisy

Turbocharger Advantages
-Excellent thermal efficiency to high-boost pressures
-Not limited to crankshaft speed (may lag behing, but can surge ahead with sufficient exhaust energy)

Turbo disadvantages
-At least minimal delay in onset of boost
-Boost inaccessible at lowest rpm ranges

Compound Advantages
-All of the above
-Supercharger produces excellent low-rpm exhaust energy to spool turbo

Compound Disadvantages
-May be inconvenient or impossible to intercool supercharger section


Other info I could pull out:

"the turbo began making additional boost and torque above and beyond that of the supercharger as low as 2300 rpm. From this point, torque and boost increased in a smooth linear fashion until the wastegate opened"


So it seems they have a succesful application of combined forced induction.

EDIT: The engine they are working on is a 1MZ-FE 3.0L Toyota V6 (into a '91 MR2) with a TRD Eaton Supercharger @ 5 psi and a Majestic T-76 Turbo @ 5 psi for a total compounded 10 psi boost.

 

neit,

Very informative post. Thank you very much.

I agree completely with Turbo's Super/Turbocharger rundown and it is nice to know that someone has successfully implemented a "compound" system. (I bet it is pricey though)

-Mr. Wigggles

 

Hey, I was just looking in the turbo magazine web page and saw a twin turbo 350Z!!

Final numbers:
Power 334.2 whp
Torque 339.2

MY Observations / thoughts:

It was possible to twin turbo it even with "the tight confines of the 350 engine bay" so it may be possible to turbo the 8

Also note that the engine has a 10.3:1 compression ratio, a little bit higher than that of the 8 (10:1) so it may be possible to have a little bit higher boost (maybe 6 or 7psi ?)

They achieved almost 90whp gain @ 5.6psi! I don't know how rotaries respond to boost compared to a piston engine so I can only imagine the power gains we can get...

Last thing, they acheived this using the factory cats in CARB-legal trim, imagine using some aftermarket high flow cats

 

well, that low boost pressure number is a good thing, meaning they're getting terrific flow with less effort from the turbo... boost pressure isn't a measurement of flow, just (obviously) how much specific force the turbo is putting on the air (pressure)... another thing to consider is that it's 3.5L large, which is a big big displacement... even if the efficiencies of the system weren't so good, you're still going to see huge quantitative increases in power with small increases in boost, simply because it's ingesting so much of it at once.