I was talking to a guy who has a mitsubishi 3000GT VR4, twin turbo and he he says he has a supercharger blowing air into the inlets for the turbo.

He says he has no lag and the power is there to 7K plus.

Anyone ever used this setup?

 

I've seen setups like this before.. thought it was reversed, The turbo had the outlet plummed into the inlet of the supercharger. This required a secondary inlet into the intake from the turbo with a 1 way flapper valve, as once up in the higher end, the cfm rating on the turbo exceeded the capability of the supercharger, this is why the secondary inlet was put in. As for performance gains, Sure you may gain some low end torque, and maybe a tad bit of low end HP, but I would honestly think that in the end, the overall HP figure will be no higer than if it were just a turbo, maybe even lower in hp figures.
To make things simple, Garret is apparently trying to make a Turbo that is both standard and electric, so it would act as a supercharger in the low end, but then be taken over by flow just as if it were a normal turbo.

In the end. I think all of that is a waste of time. If a properly matched turbo/engine combination is used, Lag will hardly be anything of an issue.

 

i think one of those new nissan's over in japan uses a electric turbo.

 

:rolleyes:

 

:rolleyes:

 

It wouldn't be a turbo then, it would be an electric supercharger, if it actaully even exists. A turbo by definition is an exhaust driven supercharger.

With regards to a suprcharger/turbocharger combination, it's totally unneccessary. Some people on these internet forums seem to be fascinated with the idea of turbo lag. A properly sized turbo on a V8 engine is not going to have any noticeable turbo lag. There's a big difference in the amount of exhaust energy created by a V8 engine and a small displacement 4 cylinder, or even a Buick 6. The inherent torque of the larger engine is going to get the car moving and make the transistion from manifold vacuum to boost transparent - with the exception of the sudden lack of traction ;). Trust me, you get on the throttle and you better be holding on tight because the power is there immediately.


[Modified by Monty, 9:19 AM 5/1/2003]

 

I know a guy who has a turbo/supercharger setup on an MR2 MK1 of all things. Don't know how it was plumbed, but that car suffers no lag. It was built as a track car, has full roll cage and all, but the guy who owns it uses it just as a street-show car. :rolleyes: Anyway, whether that type of setup is advantageous for a V-8 is questionable, but for those 4-cyls, it seems like a pretty good setup.

Tony

 

Now this is Just for sake of argument, most commonly the reason for cars to have lag is cause they want more CFM and the only way to "properly" gain more cfm is by using larger trim sizes or a completly larger turbo. So the question is, what difference does it really make wether you have a 4 cyl or a 8 cyl. when comparing the flow rate, they should be similar, but only on different levels. I don't think there is a perfect combination of engine/turbo settings. If you want no lag, then you get a smaller turbo, or smaller turbine and large compressor wheel, but then in order for the turbo to produce enough cfm in the high end, you would technically have to overspin it. On the other hand, you get a larger turbo, with a little lag, you get lower inlet temps, more cfm at lower rpm's and no risk of over spinning in the high end.

Now this is just my thought.


Aside from that, the electric turbo is still exhast drivin, but also has a starter style motor that will spin it when in the lower end, no boost level.

 

Remember that turbos are comprised of both turbines and compressors. Other than being connected by a common shaft, the wheels and housings can have a wide variety of characteristics that enable you to tune the turbo to a particular application and desired performance characteristics. The ability to match the compressor to your cfm/pressure ratio needs with the turbine wheel/housing to put it where you want in the rpm for your specific engine combination is what makes turbos the ideal power adder.

As with everything else engine related, there are always compromises. As you indicated, if you want off-idle boost, you'll more than likely sacrifice efficiency in the upper rpm range. This will result in increased IAT temps depending on the compressor map, but except in extremely mismatched applications the compressor is still capable of providing the air flow necessary to support the engine. All you have to do is look at, and understand, a compressor and turbine map to see this.

But the fact is, you really don't want boost that low if you are going to use the engine in a street car. One of the advantages of a turbocharged engine is that it typically has very mild, OEM streetability when cruising or in traffic, but as soon as you get into the throttle with authority the power increases tremendously immediately.

The inherent torque of a V8 engine is going to mask any "turbo lag" that would be present on almost any reasonably sized turbo. All turbos have lag since they are not directly connected to the crankshaft, but it is measured in milliseconds. One thing that turbo detractors fail to mention or realize, is that while turbo lag does exist, that is a single event of very short duration. Once past that transitional period, again measured in milliseconds, a turbo has the ability to gain boost at a greater rate than the engine rpm rise rate. A crankshaft driven supercharger cannot do this. There is a reason that almost all of the world's high-end, exotic cars are turbocharged.

 

As an example, here is my compressor map with a "trace" of where I am operating on the map throughout the rpm range at WOT. This is based off of a dyno run. As you can see, it tracks the peak efficiency island throughout the rpm range pretty well, at least from ~3000 to 7000 rpm. If anything, it indicates that I need to run a little more aggressive boost curve past the mid-range rpm to increase efficiency further. At that time, we had teh boost controller fully closed so the boost curve was dictated soley by the wastegate spring. Now that I have an electronic boost controller, I will be able to optimize the boost curve to ensure peak efficiency and help alleviate my traction issues.

 

when those 4 & 6 cylinders get rolling, they sure do fly. I personally know somebody who owns a GTR34, AWD & AWS...twin turbo. It is a really nice car, but expensive state side at like $90K for 280 hp stock!!!!

 

Very true monty, and your correct that just the torque alone normally makes the off boost transition hardly noticable, but yet when compared to the power levels of it when in boosted state, there is quite a difference, I think the complaint is when people use such low torque engine to begine with. But you are right that a v8 it's not as big of a deal, cause you can still get off the line fairly quickly, I drove a turbo mercades, the car was sooo slow off boost that "literally a person on a bicycle could beat off the line. however once boost kicked in it was much nicer of a drive. what I am trying to get at is I bet you the torque percentages between off and on boost against 4 cylinders and 8 cylinders are very similar, but yeah v8's just have alot more to begin with. s for the turbo matching, again yes you can use a smaller turbine a larger compresser wheel, however there is a limit to this, as once under boost the added CFM capability of the compressor will overwhelm the turbine wheel/housing, and in certain situations too much back pressure will be created in the engine, "usually you have reached max prm potential of the turbo at this point" and usually the turbo bearing will begin to act as a reverse pump and actually block out oil from entering leading to massive turbo failure, but it is possible, and the only time you would see such a setup is on small displacment high rpm race engines, though some HonDUH's like to to the same thing, but are just building their own grave.

 

Here is a pic of what you are talking about.

http://www.supraforums.com/attachmen...postid=1047693

:cheers:


[Modified by Corey 68, 4:31 PM 5/2/2003]

 

Electric supercharger? :skep:

I did see pics of a Honda with a leaf blower under the hood that actually developed a few pounds of boost. But jeeze!

Anything wrong with conventional methods?
That's what I meant by...
:rolleyes:

 

link wont work unless we join that forum............

 

here is some info re: electric turbochargers
http://www.goldenbig.co.kr/Part_2_files/main.htm
http://www.goldenbig.co.kr/Part_2_files/p2-01.htm

they do exist!

 

Yes and it's junk!

There's alos people selling detmar tunnelblowers as electric superchargers. There's no such thing as an electric turbocharger sine a turbocharger is exhaust driven.

You will not see any gains w/ those electric things, the only thing they might do is wreck your engine when a vane breaks off.

There was indeed a guy w/ a red leaf blower (was it called torro or soemthign??) under the hood.

 

nissan uses a setup like this on some of its japan only vehicles. I would not call it "junk."

Granted, it is not a turbocharger by definition (no exhaust fumes used), that is the name it has been given in japan & asia so it is just making its way to the states.

It may take some time to get use to the imports.

CFM is CFM and RPM is RPM, so if the twin electric turbo can spin at 80,000 rpm and feed up to a 8000CC engine then these minor examples are just the tip of the iceberg.

Seems that adding one or two of these will definetly drop a some time off your e.t.

 

this looks like it's becomming a conflict of opnion. It's hard to call an item that is both electricly operated, AND ALSO EXhAUST DRIVIN. IT's still drivin by exhaust, still operate exatly like a regular turbo, it's just when it's not under boost, an electric motor takes over, keeping boost present. Now don't confuse these with the "electric turbo you see on e-bay. Those things are junk and in no way even resemble the operating chararistic's of a turbo.

 

*edit*

supercharger/turbo pic wont post here.


[Modified by reallycoolcorvette, 8:50 PM 5/6/2003]