lets have a technical discussion

So im addicted to the internet and have nothing to do and it has been a while since we talked about anything worth talking about in this here forced induction forum. So i guess if anyone has anything worth talking about let it out.

I guess ill get started...


Um.. so how about them dang variable geometry turbos. they's somethin else huh. anyone feel like splaining how they work.

now that's something i'll like to find out, i'm still down there learning about bi-turbos

what are bi turbos, whenever i heard of xcar biturbo, i always thought it was another way of saying twin turbo.

bi turbo, it's a twin turbo but one works on lower rpm's and the other one starts working when the engine rpm gets higher, the other one starts to work too. it's the german's way of reducing turbo lag

oh, so it's a different way of saying sequential turbochargers. ok.

ok so it's another way of saying sequential tubochargers.

pretty much (at least i think so). have you found out anything about the variable geometry turbos? i really wanna know about them

they have little flaps in the turbine (they look kinda like teardrops) that shift to make the diameter of it either bigger or smaller and to direct exhaust gases towards or away from the turbine wheel. they are controlled with a diaphragm that senses the boost presure and it moves the vanes. the advantage is that you can have a quick spooling turbocharger with good top end efficiency.

are the flaps actually on the turbine or are they in the turbine housing? i just dont understand how they can make the vanes in the turbine move when its spinning at 100k plus rpm.

can someone find a diagram of how the diaphragm actuates the vanes?

bi turbo, it's a twin turbo but one works on lower rpm's and the other one starts working when the engine rpm gets higher, the other one starts to work too. it's the german's way of reducing turbo lag


No, Bi literaly means 2.
So its a 2 Turbo set up, it has nothing to do with how they are set up, and can be sequential or parrallel.
e.g. the Maserati BiTurbo uses a Parrallel set up with one turbo on each bank of cylinders.

yall see that electrically assisted turbocharger mazda has been testing on the rx-8, it uses an electric motor built into the turbo to spool it at very low rpm.....like 1500, that would be cool but I dont think it would be realistic on a turbo the size of lets say a SP 74 or a GT42 any big power turbo, any feedback

does nitrous decrease gas mileage? i figured no since all it does is make the gas burn more richly and cools the incoming intake air that it has nothing to do with the fuel system.

nitrous leans out a motor not richen it.

no i mean it has more oxygen so it makes the gas burn more richly

no i mean it has more oxygen so it makes the gas burn more richly

Maybe you should try explaining what you mean without using the words "rich" or "lean" ;-)

ok fuel needs oxygen to burn and the more oxygen you can fit in, the better it's gonna burn. air has i think about 14% oxygen and nitrous has about 33% so nitrous is gonna make the fuel burn better. if there was a way that you could spray nitrous for a very long time would it descrease gas mileage? I have a feeling that it won't since it doesn't cram more air into the engine so more fuel doesn't come in to make the fuel/air ratio better, but there's this stubborn ass guy that keeps argueing with me about it.

well you need to learn the difference between lean and rich. lean means that in the air to fuel ratio, there is too much air. rich is the opposite, there is too much fuel for the air to support. now when running nitrous you should add more fuel to make more power and to get closer to a stiochiometric mixture 14.7 to 1 (i believe). if you dont add fuel when running n2o you will have more oxygen than you would have in a stoich mixture therefore you are running lean.

for better fuel economy you are supposed to run a little lean, the fuel burns quicker, giving you more power and less need for fuel. putting a bit of nitrous can help fuel economy but it costs soo much that it isn't worth it, you won't get any return on investment.

Adding the fuel with the nitrous is necessary and will therefore decrease mpg while it is turned on. I am not aware of any nitrous system that will add only nitrous.

it's not necessary to add fuel, you can run a little lean without causing any damage to your engine. you can do this by either reducing the ammount of fuel or keeping the same ammount of fuel and increasing the oxygen. if you add a very small ammount of nitrous without increasing the fuel you will get a bit more power and better fuel economy but it will cost you the price of nitrous. all you have to do is keep the engine from running too lean.

I guess you are correct , add up to just a bit horsepower 20 max. It would be ok. I was thinking in the 100's.

if you want 100 more horsepower you will decrease your fuel economy. the way to get better fuel economy is to use less fuel to do the same ammount of work. so basically you make what you have mroe efficient. putting a whole exhaust system will increase fuel economy, as long as you can keep your foot off the floor, increased compression will do the same. nitrous will only add to fuel economy if you don't use more fuel to do the same ammount of work.

to add a little bit to the variable turbo's, such as aerochargers, they have multiple vains that move on a linkage, which move towards and away from the turbine, creating more or less velocity across the turbine. This allows it to act as a small AR at low flows, and then as the flow increases, the AR increases, keeping the back pressure from getting out of control, but still allowing early spooling.

They are very fragile though, and have a habit of getting damaged with any kind of high boost numbers.

There has been other attempts at the same thing that are more robust....I'm actually designing my own setup on a motorcycle that will have the same idea behind it without the fragile aspect...but although I'd like to take credit for thinking it up, diesel turbo's have been playing with my idea for a long time, but its definitely never been used quite in this fashion, let alone in the application

are the vains on the turbine or compressor or are they a moving part of the turbine or compressor housings?

are the vains on the turbine or compressor or are they a moving part of the turbine or compressor housings?
They're attached to the turbine housing.