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Discussion Starter #1
Wow, take a look at the Celica forums. There are several supercharger kits already available for the 2ZZ-GE engine. I'm sure somone will get around to adapting it to the Elise. Looks like the most radical kits will be putting out 300HP/ 230ft-lbs. Yikes that'll provide motivation for the Elise. Might be worth the 75-100lbs.
 

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Discussion Starter #3
You got that right. The Celica isn't that big either though. Better chance with a supercharger than a turbo kit. At least you don't have to worry about the intercooler and all that extra heat.
 

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A supercharger setup still needs an intercooler for the same reasons a turbo does (compressing the air increases temperature). Low boost systems, either supercharger OR turbocharger, often do not use an intercooler to keep cost down.
 

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Discussion Starter #5
Most of the supercharger do run lower boost (0.5 bar) You are also not running the air thru super hot turbo. Mine glows red after a spirited drive. Imagine what that does to the air intake.
 

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The supercharger kit for the Miata 1.8L engine that makes 280-300HP does so by using an intercooler. There is a much lower powered version which omits the intercooler and runs at lower boost.
 

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Discussion Starter #7
An intercooler would be tough to fit in that engine bay. We'll have to wait and see what becomes available. One fear I have is the aftermarket might not be attracted to the Elise because of the low volume.
 

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ARGH ok people turbos, even glowing red, do very little to the air temp going into the engine while actually driving. Turbos of the 80s are a different story...

All of todays turbos are cooled by at least oil, and most by both oil and water. The compressor side of the turbo actually only raises the temp of the air by a very small amount in terms of radiated heat due to the cooling, and the design. Think about it this way, you have relatively little surface area with a massive amount of air flowing through letting only a small amount of heat (per volume of air) transfer. So in that respect turbos and superchargers are fairly similar.

In general turbos are MORE efficient than superchargers in terms of how much they heat up the air by compression, plus they do it over a very large rpm range and are easily controllable though wastegates etc. Some superchargers however can be more heat efficient, but are limited to specific amounts of airflow (not boost) at specific rpms. So in a high revving engine, you normally have a boost falloff as you get higher in the range, where a turbo will keep you boosting all the way up to redline.

BOTH a supercharger and a turbocharger SHOULD have an intercooler, especially in a situation where the car will be on the track. Anyone here looking at getting an elise and never tracking it?

The only real advantage to a supercharger is where you put it. Drag cars use turbos because they run at Xrpm for 5 seconds, then they rebuild the motor. Turbos take a small amount of time to "spool" and on the racetrack thats fine, on the 1/4 mile it can really hurt you, even if your overall hp could be higher with lower temps going into the engine. If the turbos are sized properly for your car/torque/hp requirements you probably wont even notice the lag (doing its intended purpose. A race prepped car will lag on the street, though the track it will be perfect)

Scot
 

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Discussion Starter #9
Sounds reasonable bit it's hard for me to believe the heat from the turbo doesn't contribute to the intake temp. The oil to the turbo acts as a lubricant for the turbine shaft connecting the exhaust turbine and compressor. The water cools the turbo enough so that the oil doesn't congele but does little else. The entire casing on my turbo glows red hot after a spirited run. In fact you should see all the heat sheilding around my turbo in the engine bay. Does a supercharger get that hot? I can't imagine all that heat doesn't contribute somewhat to the intake temps. I understand you are moving a fair amount of air but I imagine the whole intake side becomes fairly quickly heat soaked not just the compressor. If the supercharger generates less heat, it may be the way to go for the Elise. Heat may be a problem with the midengine layout.
 

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Must agree with Scot here - there are different sources of heat from a turbo but the biggest source is compression, not the turbo housing itself. Heat is radiated out from the hot housing but due to the volume of air and the speed at which it flows minimizes the exhange of heat.

Think of an AC unit - the high compression side is hot, and the low pressure side is cool. The temp of the compressor doesn't play into the equation.

Cheesey Explaination on how AC works
 

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Discussion Starter #11
I'm still having trouble understanding why compressing air to 34psi would generate soo much heat. My power tool compressor moves more air at a higher pressures yet the air is not hot. What am my missing?
 

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Kenetics my dear friend, kenetics.

It's compressing a much smaller volume of air, it's only compressing it when needed (not all the time) and it's doing it over a longer period of time. Car turbos compress a lot of air all the time. If you do the math a 2L 4 Cycle engine running 1000 RPM will use 500L (2*[1000/4]) of air a minute, 6000 RPMs and you're now at 3000L. Add a 10 PSI compressor and now you are pushing 10 times that much air - 5000L at 1000 RPMs and 30000L at 6000. That's a lot of air.

That was an example, I don't know any cars have a lot of PSI boost at such a low RPM and I'm not sure if the PSI/compression is right - I doubt that it's a 1 to 1 ratio. Undoubtedly some one smarter than me may tell us the real ratio for turbo engines.


It's the difference between getting splashed with hot oil vs. putting your hand in it for a minute. A splash of oil only has a small amount of energy to transfer, but a large amount (like in a deep fryer) has more energy to transfer.


Ok, dork hat off... :cool:
 

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Discussion Starter #13
I think I'll see if I can find a text on the thermodynamics of firced induction. The math doesn't add up in my mind. I'm going to try to find out the contribution of radiant heat and compression to intake temps.
 

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Best setup in this case would be a water-based chargecooler like used in the Esprit. (not water-injection....)

A water/air heat exchanger is used on the engine and pipework+radiator are mounted up front to cool the water.

Works very well, but is expensive (needs a pump too) and would be a lot of work to put in.

BTW.. A turbo on the Elise is usually not a good idea. The non-linear power delivery of a turbo makes the cornering behaviour rather 'interesting' if you get onto the throttle and the boost kicks in.. Light, mid-engined car and all that..

Superchargers work much better to keep a linear power delivery and throttle response.

There is an aftermarket supercharger option for the Elise in europe (don't let the name fool you.. it's from 'turbotechnics', but it's a SC..) and it works very nicely.

Makes the car drive like it has a normally aspirated 3.0L engine in the back.

Bye, Arno.
 

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Why do people shoot down turbos without really understanding how they work? Uneven power delivery? Come on, you have driven a few mid 80s (or early 90s) street vehicles and experienced lag if you think it inapropriate for a race vehicele.

On any car running modest amounts of boost, lag can be almost eliminated with proper choices of equipment and a knowledge of the intended purpose. Getting a small and efficient turbo that is has the right manifold setup and a free flowing exhaust will all but eliminate lag unless you are trying for big boost.

If you are going for big boost (16+lbs) the turbo will probably have lag in the lower rpm range, but should have almost no lag higher up. On the racetrack the rpms should stay way up there through the entire course. When coming out of the corner the best procedure is to set the car to be in a position to make good power coming out, which will dictate a fairly high RPM. This lets the car flow more than enough air to get the turbos to spin up without any lag related issues, linearly, with the throttle application. Unless of course, the wrong turbo is chosen.

Another big myth is that superchargers produce more torque than a turbocharger. BZZT wrong answer. Gas + air = power. A properly sized turbo will throw more air into an engine than a supercharger at the same rpms at a lower temperature. Plus it shouldn't run out of steam at 5krpm. Remember on high revving cars, superchargers become a major liability since they generally cant keep up with the higher airflow required. or they have issues at the low end.

The big drawback to turbocharging is complexity. You need the turbo, the manifold, wastegates, blowoff valves (without that stupid super loud PSSSSHT sound,) controllers, ECU and a really good tuner. The other stuff (including intercooler etc) you would also need on a supercharger running the same amount of boost.

Scot
 

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Re: Lag - it is impossible for a turbo to be spinning fast enough to produce boost when you remove your foot from the gas for any length of time then push it back down... it may spool very quickly but put it next to a car with plenty of toque/power and no forced induction and you will definitely be able to tell the difference.

Turbos have indeed come a long way, but you still get lag, albeit small amounts, when you shift gears or lift off the throttle. You can get "used" to it and compensate for it, but who wants to compensate if you don't have to?
 

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With the Elise we're talking about a high compression N/A motor at 1.8 liter and 190hp it's already running at it upper range. Adding forced induction means lower boost levels, so your looking at 30-50hp gains. Even with a small quick spooling turbo you will not build full boost in the lower gears. Given the complexities of trying to fit all that hardware into a very tight package, the cost and effort to properly tune it and the lost of reliability and durability... if I really want more power, will look at getting it from the N/A motor. Have been driving a mid-engine (small) turbo for many years. As Brain has mention purely from a handling standpoint, I don't want no stinking turbo. ;)
 

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I did not say the car should get forced induction of any type, just that turbos are not the root of all evil. There is no way to absolutely eliminate lag, but it can be reduced to the point it is a non-issue. Just like a supercharger, which has to vent boost when you let go of the throttle, there is a small delay when you hit the gas before the aboost pics up.

If you size a turbo to produce a max of 5lbs of boost at high rpms, it will be well within its efficiency range and probably at full boost around 1500-1700rpm, even on a 4banger. This would give you more torque available at a much lower rpm than stock, more than a comprable supercharge. You could size it slightly larger depending on the exhaust flow out the back. An open exhaust, ie no cats, the turbo will spool extremely fast, to the point you truthfully will not notice it. Stock turbos provided by manufacturers are limited my emissions, politics, and warrantee issues. You have a choice of many many different manufacturers who make turbos that may perfectly suit your needs.

I am sorry if you have driven a car with a bad turbo setup, but properly sized you do not need to "drive around" the turbo on the street. The power will be immediately available when you need it where you need it, and more of it than a supercharger. If you are looking for maximum power, then yes, you will lag at low rpms, but that is purely your choice, and it will be vastly beyond what a supercharger can provide, with the complexity drawbacks in place of course.

Scot

Personally I won't be turbo or supercharging my else. If I want more power, maybe the honda engine will be in my future but I doubt it for the first 2 years. Then again who knows, but having driven the euro demo, and lots of time on the track under my belt in midengined vehicles, I want to learn the car as is first.
 

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Lag in only part of it. With any turbo you get a nonlinear response. There will be varying degrees of lag depending on the setup. None of them get around the lower boost levels in the lower gears (not rpm). Once the turbo spools up it will build boost very quickly. Let off for just a second & all the power from the turbo is gone. Get back on it varying degrees of lag & a quick shot of power as you get into the boost, makes for on/off power when using any turbo. That hardly makes them "evil" it's a great way to get more power from any engine. From a handling standpoint would much rather have the linear power delivery of the N/A, nor am I very concern about the Elise not being fast enough.
 
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