turbo questions

[laffie]

well i was wondering whats the difference between sequential twint turbos and pararrel twin turbos? Also why two turbo have less lag than one big turbo? Is it because its easier to spin two small wheel than one big? If i have one big turbo and i don't want the lag, can i just switch to a less heavy wheel?

tx alot

[pwpanas]

Originally Posted by laffie

well i was wondering whats the difference between sequential twint turbos and pararrel twin turbos?...

With sequential turbos, the setup first makes boost from one turbo alone, and then it switches to making boost from both turbos. This lets you get boost almost twice as quickly.

Originally Posted by laffie

...Also why two turbo have less lag than one big turbo? Is it because its easier to spin two small wheel than one big?...

Two turbos (in parallel) do NOT have less lag than one big turbo. Only sequential twins reduce lag.

Originally Posted by laffie

...If i have one big turbo and i don't want the lag, can i just switch to a less heavy wheel?...

Sure, but then it wouldn't be a big turbo anymore (less heavy = smaller).

[laffie]

thank you very much!! but why only sequential turbos reduce lag?

[pwpanas]

Originally Posted by laffie

thank you very much!! but why only sequential turbos reduce lag?

100% of the exhaust goes through only one of the two small turbos first, and all that exhaust flow spools that first small turbo at (for example) 2250 rpms. At 3500 rpms, there's enough total exhaust flow to spool both turbos, so exhaust valves open and then both turbos run together.

[cageceo]

Cool, lol, i didn't know that exactly. i had the concept that on sequential turbos went on one after another.

example.

turbo 1. engages at 2500Rpm
turbo 2. engages at 3500-4000 Rpm, and shuts off the first turbo.

so basically you always got turbo on almost a full power range. that's just what i had thought, but Glad to know the truth. seems alot more effcient the true way.

[pwpanas]

Originally Posted by cageceo

Cool, lol, i didn't know that exactly. i had the concept that on sequential turbos went on one after another.

example.

turbo 1. engages at 2500Rpm
turbo 2. engages at 3500-4000 Rpm, and shuts off the first turbo..

That'd be pretty weird. Why turn off the 1st turbo? What would be the benefit of that setup over a single turbo system? In other words, why would you think it was designed that way?

Originally Posted by cageceo

...so basically you always got turbo on almost a full power range. that's just what i had thought, but Glad to know the truth. seems alot more effcient the true way.

Yep the 1st turbo never turns off, except below about 2250rpms...

[cageceo]

from the word Squence, lol like i said it was just a thought. plus i guess to avoid extra heat, not sure but as i said the way you explained is a heck of alot more efficient, and makes more sense .

i guess another reason to get a TT over a NA supra huh.

is it true that when the turbos are off they some how improve milage on a car ??

check out this link to see what im Talking about

http://www.youtube.com/watch?v=4Y386YPVAFw

[JPDsupra]

I thought turbo made fule economy worse even when there off but they are considered "free power" cuz it doesnt use the engines power unlike superchargers cuz it works on air(partially). I saw a setup on a ustang with a twin supercharger though it looked impossible to recreate and it only made 600hp on pump gas( dont know if it was rwhp or just crank hp). I wish I had a pic but I saw it at a dragstrip.

[pwpanas]

Originally Posted by cageceo

...is it true that when the turbos are off they some how improve milage on a car ??

Not signifcantly, although there is probably a very minor effect from swirling the air more than an n/a engine (a la tornado).

Imo, the only related significant effect is the efficiency of running a relatively small displacement engine, which means that off-boost you get decent gas mileage (unlike a big block v8, for example)...so you get the benefits of a smaller displacement engine, and the power of a larger displacement engine at the same time.

P.S. The focus of Sam Mahdavi's interview was promoting the benefits of turbocharging, which I wholeheartedly agree with!

[JPDsupra]

jw who's Sam Mahdavi and what interview is it on a website