Serial Turbocharging

[mlhm5]

How fast can a turbocharger boost be when you step on the gas? It certainly is not anything like a supercharger.

 

IMO, it seems it would be difficult for a turbo to deliver the boost equaling the fuel capabilities of a direct injection system, at least from 0-2500rpm.

 

After all, with a turbo, its abilities are linked to engine rpm and how much air is can be moved at an rpm.

[battyr]

If I understand serial turbocharging, it would work great for down sizing. The only problem is that they require the cost of two turbos and extra plumbing. They have reduced turbo lag, but there is still some lag from all the extra turbo plumbing.

 

It sounds like the EcoBoost has manage better results without the cost of extra plumbing. We will know for sure when the EB comes out.

[focus05]

I don't quite follow everything you're asking, but...

 

If you have a DI system like Ford's Ecoboost, then you maintain some low-end torque before the turbo threshold is crossed (and the threshold is getting lower - many modern engines have the turbo spun up by 1,800-2,000 rpms). There are already many successful examples of this setup even if it isn't as sophisticated as Ecoboost will be (see VW/Audi).

 

If you don't have DI, but the engine is in a small car, you'll likely be ok without DI as long as you're managing the turbos well and don't get a blast of power as they spin up or a drastic drop off the back-end. This is the model GM is taking for the Cruze.

 

GM's system probably won't work in larger vehicles because there probably isn't enough torque to adequately motivate larger vehicles around 1,000-1,800 rpm. Their 2.0TDI, however, will work in larger vehicles if tuned properly. Ford's upcoming 1.6 Ecoboost will work in larger vehicles like the Fusion because the DI helps get more torque out by 1,500 or so and the turbos start taking over from there.

 

Neither one relies on a supercharger and both will probably be effective in their target applications. So, no, you don't need supercharger.

[mlhm5]

I don't quite follow everything you're asking, but...

 

If you have a DI system like Ford's Ecoboost, then you maintain some low-end torque before the turbo threshold is crossed (and the threshold is getting lower - many modern engines have the turbo spun up by 1,800-2,000 rpms). There are already many successful examples of this setup even if it isn't as sophisticated as Ecoboost will be (see VW/Audi).

 

If you don't have DI, but the engine is in a small car, you'll likely be ok without DI as long as you're managing the turbos well and don't get a blast of power as they spin up or a drastic drop off the back-end. This is the model GM is taking for the Cruze.

 

GM's system probably won't work in larger vehicles because there probably isn't enough torque to adequately motivate larger vehicles around 1,000-1,800 rpm. Their 2.0TDI, however, will work in larger vehicles if tuned properly. Ford's upcoming 1.6 Ecoboost will work in larger vehicles like the Fusion because the DI helps get more torque out by 1,500 or so and the turbos start taking over from there.

 

Neither one relies on a supercharger and both will probably be effective in their target applications. So, no, you don't need supercharger.

 

Thanks.

 

I was thinking with such a small engine, the torque would be non-existent without boost from the initial acceleration.

 

The fuel system is more than capable of delivering the fuel required if you floored the pedal, however I am unsure if the quantity of air delivered would match the fuel delivered therefore reducing performance because the combustion would be air, not fuel limited.

[jpd80]

You only have to look at Europe's small diesels to see how turbos can be made to spool in early.

Ford is copying this formula using gasoline, Direct Injection and Turbocharging. Provided the turbo

is sized properly for the application then it works well. Early boost in the rev range also results in

the turbo peaking out earlier at about 5,000 rpms. This will probably suit American buyers because

the smaller turbo engines will act like the larger units they are replacing but with better economy.

 

Before twin scroll housings, serial turbocharging was the answer to turbo lag and rev extension.

Edited September 28, 2008 by jpd80

[battyr]

Serial turbos were needed 5 years ago, but were only used on a very few diesels. Now with high tech high temperature turbos and DI, low end torque is no longer a problem. I believe that Ford has found some secrets to valve timing to eliminate turbo lag witht its EB engines.

 

Serial turbos will provide more boost pressure. If the engine in gasoline, they have to drop the compression to handle the extra boost. With this you get more power but lose any efficiency advantage.

[lfeg]

One other thing, even if the engine is fairly low on torque at low revs, the proper gearing can make up for that. especially if the engine will rev freely and quickly. With 6 and 7 speed transmissions a steep first gear can work wonders.

[battyr]

Serial Turbocharging should give the more power at both low end and high end, but I would think that it would not reve. very quickly because the air would have to travel through and around two turbos and other plumbing. Maybe this is why it is better suited for diesels. Just shift to high gear and let it pull like crazy to redline.

[battyr]

You only have to look at Europe's small diesels to see how turbos can be made to spool in early.

Ford is copying this formula using gasoline, Direct Injection and Turbocharging. Provided the turbo

is sized properly for the application then it works well. Early boost in the rev range also results in

the turbo peaking out earlier at about 5,000 rpms. This will probably suit American buyers because

the smaller turbo engines will act like the larger units they are replacing but with better economy.

 

Before twin scroll housings, serial turbocharging was the answer to turbo lag and rev extension.

 

Newer, lighter weight turbos will help increase the peak a little with a small turbo. IMHO a small turbo and DI is only part of what Ford is doing. I think Ford has added a third element to make the turbos spool fast.

[mlhm5]

Newer, lighter weight turbos will help increase the peak a little with a small turbo. IMHO a small turbo and DI is only part of what Ford is doing. I think Ford has added a third element to make the turbos spool fast.

 

electric assist?

[StevenCaylor]

Do Ford's EB turbos use variable vane technology?

[battyr]

electric assist?

 

Interesting technology but not needed.

[battyr]

Do Ford's EB turbos use variable vane technology?

 

From everything that I have seen, no.

[SVT_MAN]

Superchargers, like the roots style are great at providing additional power and they really provide a ton of torque low down, but the big disadvantage of a supercharger is the parasitic losses involved. A turbocharger is going to be running off the exhaust gases so you aren't losing any potential energy - you are actually recapturing it, so they're actually quite an efficient mechanism. Superchargers, on the other hands, are typically belt-driven and are sucking away some of the potential for the engine to make power.

[jpd80]

Ecoboost is the economical intermediate sep before plug in electric vehicles, once electric vehicles have a range over 40 miles

consumers will by them day and night. Not a cure all in every situation but I see big advantages in peak hour crawl.

maybe overhead power supply for A/C compressors or recharging when stuck in traffic jams,

anything is possible when gasoline is taken out of the picture.