Question regarding lag.

[lwells]

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

I don't know why you find it so funny: almost every example of a an anti-lag system I can think of is on a car that is overhauled regularly. If there weren't serious longevity issues, don't you think manufacturers would all be running anti-lag?

Lucien.

[browny]

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

Easy, just make them from a directionally solidified nickel super alloy like jet turbine blades.

The only problem is that people might baulk at a turbine wheel that costs the same as the entire rest of their car.

Really, if its as simple as just picking a suitably high temperature grade of steel for the turbine, then i'm sure that anti lag would be a lot more feasible at a consumer level. The fact that it's confined to race cars suggests that there's a whole lot more to it.

[stolly]

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.

thanks everyone for all the replies, dangerous_daveo - not going to rush out and try the motor thing! - (although I might one day) just started the thread as a bit of a hypothetical on ways to get around lag. I realise a good tune etc etc will go a long way to helping, but I guess what I was thinking was possible ways to eliminate lag.

[33SOM]

Are we talking about lag here or how long it takes for a engine to spool up a turbo?

[Kaido_RR]

I don't know why you find it so funny:  almost every example of a an anti-lag system I can think of is on a car that is overhauled regularly.  If there weren't serious longevity issues, don't you think manufacturers would all be running anti-lag?

Lucien.

I think the issue of having to run the car without the Cat is a major issue for manufacturers and which they wouldnt be able to over come, also by the sounds of things were talking about a street car which would only uses antilag now and then, not all the time

[Rolls]

Instead of using a massive electric motor couldnt you just make some sort of hybrid super charger/turbo all in one that somehow runs a geared drive from the engine to spin the turbine and then clutches off when the exhaust gases start flowing?

[dangerous_daveo]

thanks everyone for all the replies, dangerous_daveo - not going to rush out and try the motor thing! - (although I might one day) just started the thread as a bit of a hypothetical on ways to get around lag. I realise a good tune etc etc will go a long way to helping, but I guess what I was thinking was possible ways to eliminate lag.

Anit lag is really about it without going to the crazy twin charger set ups.

But do you really want to remove all lag on a street car? Thats the reason I went the turbo option, I can put round all day with no boost, and use bugger all fuel.

[stolly]

Anit lag is really about it without going to the crazy twin charger set ups.

But do you really want to remove all lag on a street car?  Thats the reason I went the turbo option, I can put round all day with no boost, and use bugger all fuel.

-Yeah, great point. I suppose what I want is totally unrealistic. A switch in the cab saying 'lag' or 'no lag' and when you're not worried about fuel consumption flick the switch - you've got V-8 like pickup from idle until the turbo(s) kick in, and then boost! - Surely that couldn't be to hard!!

[Amaru]

The method of using an injector and spark plug in the exhaust manifold isnt and hasnt been used for a long time. Most new ECU's (Motec M800 and M48, Autronic, Link) run a timing based anti lag setup with rotational idle support.

The ALS retards ignition timing and keeps the throttle open so unburned fuel and air pass through the engine and ignite in the exhaust manifold (thanks to the retarded ignition timing firing the spark plug when the exhaust valve is open).

The way the throttle is held open varies from ECU's, but the three common ways are the use of an idle speed motor, a throttle screw or a solenoid setup.

The ECU uses an idle control sequence so that once it hits the set target idle speed, the ALS will cut a spark in a rotational sequence with each cylinder (explains the lumpy idle), and this whole setup is called rotational idle. If there was no rotational idle, the engine would just freely rev (because the throttle is partially open remember?).

As soo as the RPM goes over the arming target, the ALS goes into full antilag mode, and makes lots of noise. Once you come down from the arming target RPM the system will stay in full antilag mode for a period of time (making loud bangs and pops), after which if you dont hit the arming target RPM again it will fall back into rotational idle mode. It will stay in rotational idle until you hit the arming target RPM again.

Whilst running in full antilag mode, the car has no vacuum so any vacuum assisted hardware (brakes) will be alot harder to work.

As for reliability, the rotational idle is actually beneficial to the whole setup as it cools the pistons, valves and turbo exhaust housing (pumping raw fuel and air over these components brings the temperature back down -very- quickly). With occasional use, EGT's are no major problem unless you are running in full antilag mode on a highway for a long period of time. Alot of the ECU's now will have a "failsafe" setup in them as well, which will disable full antilag mode and kick you back into rotational idle if the EGT's go over a certain temperature.

It has come a long way, and I have seen plenty of street cars (including GTR's) run ALS setups without a problem for many thousands of km's. If youre EGT's start skyrocketing and you keep pushing the car while in full antilag mode, thats when you will start damaging components. I should also mention you can turn antilag off so the car runs normally without going into rotational idle or full antilag mode

EDIT: One of the cars in question ran a pair of 2530's and would build over 1 bar of boost at 2500rpm running in full antilag mode (with a target idle speed of 2000rpm and arming target of 4000RPM).

[lwells]

*snip*

I happily stand correct

[browny]

Interesting Amaru.

When you say:

It has come a long way, and I have seen plenty of street cars (including GTR's) run ALS setups without a problem for many thousands of km's

Can you give me a few more details on these cars.

eg

Are the cars everyday drivers in the true sense?

Is the antilag switched on all the time or only say at the track?

How many km's do you consider to be "many" - 10,000km?, 50,000km?, 100,000km?

[Amaru]

Are the cars everyday drivers in the true sense?

Is the antilag switched on all the time or only say at the track?

How many km's do you consider to be "many" - 10,000km?, 50,000km?, 100,000km?

Define true sense? Whilst majority of them have daily drivers, the cars are driven on the street on a regular basis without much hassle (some have dog boxes so are a pain in the arse irregardless). That said when ALS is running in full antilag mode, the car will buck and kick around alot and be a general pain in the ass unless you keep the revs up.

Some people use ALS on the street, some use it only at track. When it is armed it makes an assload of noise and pops and bangs quite a lot. When sitting in rotational idle the car is also extremely loud.

A couple of the cars I have seen (including GTR) have travelled well over 10,000km without a problem. All these cars are regularly serviced at 3000kms.

[Bass Junky]

I know that if I had it, and some little turd in a Hyundai pulled up next to me at the lights and squared up, I turn the thing on just to scare him!!!!

[Rolls]

Wow I didn't know ECU controlled anti lag was that good

[browny]

Define true sense? Whilst majority of them have daily drivers, the cars are driven on the street on a regular basis without much hassle (some have dog boxes so are a pain in the arse irregardless). That said when ALS is running in full antilag mode, the car will buck and kick around alot and be a general pain in the ass unless you keep the revs up.

Some people use ALS on the street, some use it only at track. When it is armed it makes an assload of noise and pops and bangs quite a lot. When sitting in rotational idle the car is also extremely loud.

A couple of the cars I have seen (including GTR) have travelled well over 10,000km without a problem. All these cars are regularly serviced at 3000kms.

By true sense I mean used as everyday transport, in traffic etc.

The only reason i'm asking these questions is that I found your first post very interesting, although it did make modern antilag systems sound like they are all beer and pretzels.

So i'm just trying to establish exactly how feasible it is to use ALS for an everday driver, and based on your second post i'd say not very, because of the loud and obnoxious factor, but also because i'd like to see a whole lot more km's racked up before I'd consider it reliable.

[Amaru]

So i'm just trying to establish exactly how feasible it is to use ALS for an everday driver, and based on your second post i'd say not very.

You can have it installed on an every day driver without being activated, I personally dont think its much use on the street though (unless youre street racing :chairshot).

There are downfalls including: excessive noise, excessive flames, lack of vacuum assistance for things such as power steering and brakes. Run the EGT's too hot and you can kiss your exhaust valves good bye etc. The only real benefit I can see of it, is for launching a car at the drags and improving shift times (as they car will be on full/almost full boost and you dont even have to flat change). Continual running around a circuit with it in full antilag mode will make the EGT' skyrocket after a few laps, and on stock valves the cars not going to be happy.

So at the end of the day, having it installed and using it on the street would purely be for wank factor

[Links]

http://www.autronic.com/technical_data_fil...les/antilag.pdf

http://www.autronic.com/page_files/techdata.htm

Details on using autronic ECU anti-lag system..

http://www.kiwisport.net/wp/?page_id=417

Details on how it works.. again..

enjoy..

I've seen/read about a number of street cars using it.. usually done in conjuction with a launch controller that dials up e.g. 4,000 rpm with anti-lag spooling @ say 7PSI.. launch and your off..

Mainly used in AWD cars, with a rear wheel I think you'd be struggling for traction..

[browny]

and some more, taken from another forum...

Anti-lag systems retard the ignition timing and, in combination with a throttle opening system such as a solenoid, idle speed motor or throttle screw, open the throttle wide open, so unburned fuel and a large amount of air pass through the engine and, instead of igniting in the engine, the fuel/air ignites in the exhaust manifold, and spins the turbo over, even at low engine speed.  

The theory is, as soon as you open the throttle, you have full boost and no lag.  

The air needed for this combustion is provided by the standard throttle body, which is opened to a greater extent than normal whilst anti-lag is running...  

The way the throttle is held open is a discussion within itself. On Autronic and Motec M800, they use the idle speed motor, where as on other ECUs such as PossumLink and Motec M48 (for example, which hasnt got enough outputs to run an idle speed motor), a throttle screw or solenoid is used to keep the throttle open (as stated by Group N rally rules). Running a throttle screw or solenoid allows more air to flow in, hence a greater anti lag effect.  

On my car, I have a VR Commodore air-con solenoid to hold the throttle open. Having a constant throttle opening with a throttle screw is not convenient on a street car.....throttle screws are fine on rally cars, as driveability isnt their main concern.  

The ECU uses an idle control sequence so that once you've set the target idle speed, the anti-lag will cut a spark in a rotational sequence with each cylinder, which is why they idle so lumpy, and thus the reason its called rotational idle. If there was no rotational idle, the engine wouldnt idle at all, because the throttle is so far open that the engine would just rev.  

As soon as the RPM goes over the arming target (which on my PossumLink, is set to 4000rpm), the anti-lag goes into full anti-lag mode, and it pops and bangs very loudly. The size of the bangs and pops depends on the amount of ignition retard. Once the revs come back down, it idles very loudly at about 2000rpm. As soon as the engine is placed under any load, even just cruising, there is positive boost pressure....and in some applications (mine ), it will produce 1.3 bar at 2500rpm..  

If the RPM doesnt meet the RPM arming target for a certain amount of time (user definable on some ECUs, preset on others IE 15 seconds), the anti-lag switches back into the rotational idle until the revs are increased to the arming target once again.  

The anti lag is NOT a good street modification. When the engine is in anti-lag stand by mode, the idle is lumpy and makes the whole car shake, not to mention it being super loud, although it does sound awesome  

The actual engine is MUCH louder with the anti-lag turned on, because of the massive air flow, its pops and jumps around at low speed, and if you go over the anti-lag rpm threshold, the car gets even LOUDER, and pops flames. It makes the brakes very hard due to the lack of vacuum, and it can catch you out if your not careful. Rally cars dont have to worry about vacuum because they run pedal boxes anyway  

To take off, you have to bring the revs up or it'll stall and buck around like a demon, which isnt good for the clutch or gearbox. As already stated, lots of throttle is needed to keep the car driving smoothly  

Different story at the track though. It produces tyre smoking launches, boost comes on instantly, and there is no need for flat changing or anything like that, because the anti-lag does all the work for you keeping the engine on boost  

The rotational idle is actually beneficial to the turbo, it cools it right down after a run, and if you feel the engine bay, you can actually feel how cool it is if you leave the rotational idle on for a while.  

As for turbo longevity, rally cars run incredibly aggressive anti-lag 100% of the time, so it compromises the metallurgy of the turbo, exhaust valves and manifold, requiring them to be replaced at regular intervals.  

On a street car, with occasional use, EGTs arent a huge problem, unless you go onto the freeway, rev the engine out and back off the throttle...high RPM over run for constant periods of time with the anti-lag switched on is what damages turbos and exhaust manifolds, because of excessive EGTs.  

Some high end ECUs have an EGT recovery strategy, that reduces or disables anti-lag when EGTs exceeds the set figure, as long as the EGT sensor is connected to the ECU, which means you save your exhaust manifold, exhaust valves and turbo from melting into a heap  

On the street for every day driving, anti-lag is useless, and its only good for wow factor and as a conversation point on car cruises and shows. It does produce tyre smoking launches and awesome throttle response, but we dont do this on the street anyway do we?