Question regarding lag.

[StockyMcStock]

i'll post up some dyno sheets in about 6 months when my twincharged (blower + turbo) RB25/30 is built, should be good for a laugh.

[R31Nismoid]

G'day R31Nismoid, just wondering why you were so quick to say no, can you see a problem with this that wouldn't work? Thankyou.

depends how you look at it.

to make yourself forget it.

nissan are doing it, but what combo is the turbo gonna have?

Shitty wheels and stuff that are good for stock but hopeless for modification?

How long will it last?

What if a turbo dies? What is the replacement cost gonna be like?

Say you change a BOV from stock and you get a bit of flutter etc, will that shit the motor or whatever they use?

lots of things that i wouldnt wanna find out myself as it would be costly

[lwells]

nissan are doing it, but what combo is the turbo gonna have?

I haven't checked for awhile, but the last thing I read (thanks to Rezz) was saying a twin turbo setup with electric motors to "pre-spool" the turbos.

Shitty wheels and stuff that are good for stock but hopeless for modification?

I assume by "shitty" you don't mean "shitty" quality but "shitty" size? We'll just have to wait and see, but the gentlemens agreement between Jap. manufacturers is dead and Nissan keeps making hints about challenging Porsche, so I don't think it will be that conservative (though longevity is always a consideration for OEM solutions).

How long will it last?

I imagine it will be like the existing setups: 100,000KM/5 years before overhaul. Then again, who actually follows Nissan's recommendations

What if a turbo dies? What is the replacement cost gonna be like?

Horrendous would be my guess: its going to be used on a expensive sportscar after all. But remember, plain old turbos use to be expensive at one stage.

Say you change a BOV from stock and you get a bit of flutter etc, will that shit the motor or whatever they use?

Electric motors should (AFAIK) have no problems going in reverse. Perhaps one of the engineers on here could comment.

Lucien.

[JCMarshall_Law]

Takes a lot of power to spool up a turbo and they operate at around 80,000 - 120,000 rpm, no conventional 12V electric motor will do it.

get anti-lag

[lwells]

get anti-lag

... and overhaul your turbos every couple of hundred clicks.

Lucien.

[GTR-Ben]

You say electricallty assisted turbo's would take more power than they would make... but doesn't the new GTR prototype have something like that?

[stolly]

Takes a lot of power to spool up a turbo and they operate at around 80,000 - 120,000 rpm, no conventional 12V electric motor will do it.

get anti-lag

..What is 'anti-lag'?

[browny]

It is a perfectly feasible concept to have the turbo spooled up by an electric motor. The actual logistics of doing it make it a little more difficult.

A turbo might use 5-10kW of power. A 5-10kW motor is reasonably large so there are packaging issues for one. The main problem however is providing power to the thing, and the problem with this is the amps required because we are only working at 12V.

For 10kW, you would need around 830A @ 12V. So you are talking big cabling and either a huge alternator or some form of stored energy (ie a battery). Also a 12V 10kW motor needs to have really large conductors inside because of the high currents involved, meaning it's big and heavy.

WRT the comments that they would take more power than they make, I don't think this is neccesarily true, as long as you could design a nice efficient system (I'd think ~5% loss in the motor would be achievable and you might also lose another 5-10% in the rest of the electrical system). So it might use 1-2kW more than what a conventional turbo would, which is more than made up for by the extra power that you get from FI.

I don't know anything about what Nissan are planning on doing, however my comments above are based on full load, constant operation. Once you start to get into short term transient stuff, like what i'm imagining their system does, then you can start scaling the size of everything down.

[Freeman]

..What is 'anti-lag'?

Can someone please tell us?

[Bass Junky]

Anti Lag... Basically a fuel injector and spark plug in the exhaust manifold so that when you come off the throttle, the fuel injector and spark plug go to work and continue to push air through the exhaust housing of the turbo, keeping it at full speed.

You hear Rally cars popping as they come into corners off the throttle, that's what it is.

[browny]

Its also incredibly harsh on the turbo, meaning frequent rebuilds are needed.

[rob82]

This isn't the only method, if you reduce the timing it creates a hot high velocity exhaust flow, this combined with enough bypass airflow should be adequate at maintaining shaft speed.

[NickR33]

I heard Porsche were looking at an electrical motor setup to keep the turbos spooled when you were off the the throttle in their new 911 turbo? ... may just be fanciful stories but interesting...

[Kaido_RR]

... and overhaul your turbos every couple of hundred clicks.

Lucien.

i love this comment; (im currently studing mech eng, so i do alot of study relating to materials, chem etc etc)

lets take an example for you, it is very common for aftermarket turbos to come with steel wheel correct?

depending on the grade of steel uses in the wheel; The Tensile Strength of Mild steel is 450MPa and has High Ductility, Just using a random Max temp from the net for Steel is 870C.

Now Antilag itself does the following retarding ignition timing so far as to cause the exhaust valve to open well into the power cycle, resulting in extremely hot and explosive gases rushing past the turbine, spinning the turbo up therefore reduing lag.

Now antilag will not be running all the time only when lag is present and if the users has it switch on; so ruff calulcation would show that the steel would be able to handle the temp, also even if the turbo wheel is under CREEP, it shouldnt affect the wheel greatly as it would take along time for the affects to show

Also i know numerals cars which run antilag constantly, all of them are WRX, i have never seen this antilag on a nissan in real life but i would like to try it myself when i get my aftermarket turbo

cheers michael

edit: also the heat which is resulted from the antilag, will only be a few seconds and would not be closes together therefore the steel in the wheel will be able to cool down and therefore the affect of the heat would be greatly reduces

[Bass Junky]

Generally Anti Lag is only referred to in racing circles, where it's not really used during gear changes, its more used when you are off the throttle for the braking up to a corner.

This can be for several seconds. The antilag keeps the turbo spinning using fuel injected into the exhaust manifold so that when you get back on the throttle, you have full boost.

It's not really that good for any part of your turbo system. This type of system is only used on race cars.

The launch control style of Antilag involves a 0 kph speed limiter also to allow the drive to hold full throttle and the timing is retarded to increase boost. This system is turned off as soon as 1kph is registered.

[Links]

http://www.rallycars.com/Cars/bangbang.html - here is some info on ALS

[dangerous_daveo]

There are other ways to get around lag. If your doing it yourself the motor thing is just far too much effort. Factory is much much different, they have a lot more money to throw at R&D, and production.

Other ways might be, a good tune, a good exaust manifold. Keeping the exaust gases and their heat inside the pipe work, hot air travels faster as it is thiner. You can go for a heavier than standard fly wheel. If the car is already rolling, jump on the brakes and the go go go pedal. Basically putting load on the engine, and bring it on boost earlier.

[browny]

Gts_evilution

Refer to the two comments in the page posted up by Links. Anti lag is very hot and very violent = short life span.

A quick rise of the turbocharger's temperature (which jumps from ~800°C to the 1100°C+ region) whenever the system is activated

A huge stress on the exhaust manifold and pipes (mounted on a street car a bang-bang system would destroy the exhaust system within 50-100 km)

The turbo produces significant boost even at engine idle speeds

The explosions which occur in the exhaust tubes generate important flames which can, sometimes,  be seen at the end of the exhaust tube

Reduced engine brake

[Bass Junky]

Yep, that's exactly what I though.

Extremly hot, extremly damaging.

Blow the guts out of your cat in minutes.

[Kaido_RR]

Gts_evilution

Refer to the two comments in the page posted up by Links. Anti lag is very hot and very violent = short life span.

cheers for the reply i agree with the comments about the exhuast, the cat would not stand a chance.

Now that you have given me any idea about the lvl of the temp the turbo will go through when antilag is uses, i should be able to calucator if the turbo will be able to hold the temp, just need to find the grade of steel/metal uses in the turbo, if anyone has any idea please post up

cheers