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2things needing clarification

"6) You need to run the engine at idle to cool down in a turbo car after some hard driving,
no need for this in an S/C car."


-if the supercharger is oilcooled, it is a wise idea to run the car for a minute to let the oil cool down, same as a turbo.

"2) Superchargers are parasitic drags on engines: True superchargers do require HP to
operate, BUT so does Turbos, from a different source."


-with a turbocharger, the loss is minimal, and about the same restriction for most size turbos. you also have gases flowing freely out of the exhaust through the wastegate.

-with a supercharger, the horsepower loss is linear, the more power you make, the more power you loose.

although for daily driven cars and owners that aren't hell bent on performance, i would point them twoards a supercharger, instead of a turbo kit. i'll should be seeing SWIFT-RACING TECHNOLOGIES kit soon, i am very interested in how the finished kit will look installed.
 
Turbos are particularly needy for idle/cooldown because the shaft can still be spinning even after you shut the car off. A supercharger stops moving at the exact moment the engine stops.

It is very difficult to make a turbo manifold that can flow as easily as a simple header. Nearly all of the wastegates I have seen are MUCH, MUCH smaller than the equivalent non turbo manifold. I would argue that 95%+ of turbo installations add a signifcant back pressure on the exhaust flow (as compared to a non turbocharged equivalent model).
 
Originally posted by TEG:
Turbos are particularly needy for idle/cooldown because the shaft can still be spinning even after you shut the car off. A supercharger stops moving at the exact moment the engine stops.


actually, that is a common misunderstanding, the actual/more critical reasons is that turbos are in need of cool down because the hot oil, if left hot, will coke (bake onto) the bearings and shaft the connect the 2 wheels. if it cokes onto it, after a while it will start to grind on both causing excessive wear, and inturn impleller and exhaust wheel contact (the death whine as the supra boys know it as) on each wheels respective housing.

[From TEG: It depends on the turbo, but lets say you have a really big ball bearing turbo which recircs air when off - I have heard them spinning for a while after the car is shut down. The problem when shutting off is that the oil and water pressure then stops immediately - so you lose all your cooling and lubrication to the turbo. And yes, oil coking is one of the bad consequences which can lead to shaft scoring and failure. There is a big market for "turbo-timers" that keep the engine idling even after you pull the key out of the ignition...]

a turbos wheels are going to spin the same amount after shutdown, whether back into a parking spot in neutral, or you do that same thing and then let it sit there for 3 minutes. either way you have the same amount of exhaust gases propelling the turbine wheel (s) with the car in neutral as you do when a turbo timer runs the car for 3 minutes.

the key, critical point for length of idle time before shut down is oil temperature, not shaftspeed,at idle shaft speed comes down in about 5 seconds on a standard turbo and 15 on a ball bearing to not moving at all, on the other hand, circulating cool, non damaging oil can take much longer, that is why atleast a minute is recommended for normal driving and 3 minutes if you just ran it hard and pulled into a parking spot.

if you have a VATN turbo with a self contained oiling system, you can shut the car off immeadiately, because the oil is continually circulated until it reaches a certain temperature, and then it is shut off (part of the perks of that kind of turbo)

[From TEG: I somewhat disagree - I think the important issue is NOT _shaft speed_, or _oil temperature_, but rather _shaft temperature_. You need to idle your engine for a while so that the oil continues to circulate and doesn't bake on the hot shaft. If you have an "oil-less" bearing, you still want to keep the shaft spinning, and the coolant circulating until things have cooled down.
There are some developments in "foil bearings" that try to keep the shaft floating on an air pocket when it is spinning, but those are not really found in automotive use (yet). ]


It is very difficult to make a turbo manifold that can flow as easily as a simple header. Nearly all of the wastegates I have seen are MUCH, MUCH smaller than the equivalent non turbo manifold. I would argue that 95%+ of turbo installations add a signifcant back pressure on the exhaust flow (as compared to a non turbocharged equivalent model).
i agree, it definitely causes a much bigger restriction then a N/A equivelant and a turbo manifold will not flow like a n/a manifold, due to the n/a being designed for scavagening, as far as wastegate size, that is dependent on how much air is being forced in and out of the motor. my wastegate's hole is 2" inner diameter. it lets out a significant amount of exhaust when needed. a properly tuned n/a set up will have some back pressure so that lowend torque does not suffer, and a propoerly setup turbo system will have as little back pressure as possible. which will not be THAT much greater then a well tuned n/a setup.

[From TEG: But how does your _one_ 2" diameter wastegate compare to the possible flow of multiple (6?) tubes of the N/A exhaust syst
 
I do not know about the rest of you, but I certainly hope that the Swift-Racing products do what they say. I see in the performance forum the RMM intake has caused some problems and decreased performance. That would be a nightmare! I would be willing to spend some $ to upgrade the performance of the my beautiful IS, however proven HP gains, reliability, and voiding the warranty are concerns of mine. Swift-Racing certainly seems knowledgable and dedicated to the task, but talk is talk, anyone have any information on this company?
Thanks!
 
Originally posted by TEG:
Turbos are particularly needy for idle/cooldown because the shaft can still be spinning even after you shut the car off. A supercharger stops moving at the exact moment the engine stops.
The need to keep the engine running after boost-ful runs, is to keep the coolant (either oil and/or water) flowing through the turbo. Otherwise, the oil cokes and causes buildup... Newer technology (ball bearing, oil AND water-cooled turbos) makes this less and less an issue however.

Originally posted by TEG:
It is very difficult to make a turbo manifold that can flow as easily as a simple header. Nearly all of the wastegates I have seen are MUCH, MUCH smaller than the equivalent non turbo manifold. I would argue that 95%+ of turbo installations add a signifcant back pressure on the exhaust flow (as compared to a non turbocharged equivalent model).
Many people go to a tubular manifold (looks like a nice header) for a turbo for this reason. In the process, however, you lose spoolup. It's a trade-off just like in an NA application - bigger exhaust, more topend power, less lowend...


------------------
Tony
'01 Spectra Blue
'94 Turbo Miata
 
exactly, that is why i prefer turbo over supercharger. also, here is something for all of you to think about....

....the fastest drag imports, are they turbo or supercharged? i have seen (i hate to use this car as an example, because it is the worst car to modify IMO, but everyone is familiar with it so i will) a bunch of turbocharged nine second hondas and even a turbo 8 second honda in person, and plenty more in magazines. i don't think i have ever even heard of a 10 second supercharged honda, let alone a 9 second supercharged honda. why is this? a turbocharger is a more efficient power adder, i think, but you can draw your own conclusions.

Originally posted by webmaster:
Many people go to a tubular manifold (looks like a nice header) for a turbo for this reason. In the process, however, you lose spoolup. It's a trade-off just like in an NA application - bigger exhaust, more topend power, less lowend...

[From TEG: Yeah - and what about the _fastest_ dragsters/funnycars - the "top fuelers" are they turbo or S/C??? ]



[This message has been edited by TEG (edited November 15, 2000).]
 
Originally posted by webmaster:
Many people go to a tubular manifold (looks like a nice header) for a turbo for this reason. In the process, however, you lose spoolup. It's a trade-off just like in an NA application - bigger exhaust, more topend power, less lowend...

Alot of people that are into show will just get whatever looks nice, I mean some of the manifolds out there look like pieces of ART! But those that are into the performance aspect know that some tubular designs are developed and proven to give faster spool up without taking away any topend.

------------------
KP
94 6 speed
BPU
 
Ok, many imports have not used superchargers due to their sizes that are currently available, but like all things technology is changing and we will be having superchargers that are smaller than some turbos and the ease of installation of these superchargers will rival any other system.

Here is a dyno of a GS400 on 15PSI boost:


Here is a dyno of our HFI (High Flow Intake) on the N/A GS300 :


And here is a link to some records using centrifugal superchargers in Fords, yes I know Fords, but 7.2 seconds in the pro class, DAMN!: http://www.procharger.com/newracing.html

Here is a link of our GS4 and some interesting videos, there is a video of us against a turbo charged Integra GSR, See what I mean by turbo lag, and damn all that noise. http://www.swift-racing.com/pics

------------------
Muhammad I. Choudhury
Swift Racing Technologies
www.swift-racing.com
mc@swift-racing.com
 
The war rages on...

Anyways - I stand by my opinion that superchargers tend to be more "drivable" (controllable and friendly) than turbos.


If you want max boost at lowest cost, then a big turbo makes sense.

If you want to run at high altitudes then a turbo makes sense.

If you really want the thrill of an engine that revs for a while then gives you a major "kick" (just for fun) then a turbo (and/or on/off VTEC) makes sense.

=========================================

VATN turbos were mentioned. I don't think it is true that all VATN turbos have oil-less bearings. I think the poster was talking about the Aerodyne unit. I have read that Aerodyne turbos are very "advanced", but have had some reliability issues.

As with many technologies, the "highest tech" often fails compared to older tech that has more sorted out quality control and proven materials.

============================================

Here is another link to keep you busy:
http://www.avatar.com/~kory/fai.htm



[This message has been edited by TEG (edited November 15, 2000).]
 
that is definitely a badass GS400, and it sounds really good too, almost like a mustang (hate the car but love the exhaust note).

as for that integra, i don't think it is the turbo that makes it's exhaust so loud, it is either his Weedwacker Tip, or he has the catylitic disconnected. a turbo will actually quiet a cars exhaust due to the restriction, it causes some sound reverb.
 
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