Steve_Yeowart

Group A cars and WRC cars we all know why they pop and bang as much as they do , anti lag etc.

But why do group N evo's bang like they do with out any of that type of kit where as group N scoobies don't, does a Lancer RS road car bang as much as the rally cars given that they should be of equal mechanical setup?

Cheeky Jim

John,

Forgive my ignorance, but can you simply purchase an ALS and install onto the turbo/engine? I rather like the sound of pops and bangs and i presume that it would help with response times (i.e on/off motoring).

Does it also mean that my fuel bill will increase as I am effectively burning up excess fuel in the exhaust?

Do I need to decat?

Am I talking **** ?

Thanks,

Jamie

johnfelstead

you are talking ****. LOL

not a practical proposition on a road car, the main problem is the extra heat generated, you would not believe how much extra shielding is required when running ALS.

total waiste of time on the road IMHO anyway, you would need a £1200 turbo also, bet you are going off the idea now!

ernie

If I may also add a question, why do WRC cars never allow the turbo to cool before turning off the engine?

Kev

ernie

Probably because they don't have to pay for them themselves and they don't have to last 60-80k miles

K

[This message has been edited by Kev (edited 18-07-2000).]

HunterB

"why do WRC cars never allow the turbo to cool before turning off the engine?"

Two reasons - 1) as Kev says, they don't need to last long (they're replaced for every rally and occasionally during an event), and 2) because with fully-synthetic oil, it's not necessary. Carbon-based oil, under extremes of temperature (e.g. when you turn off the cooling to a hot turbo) can "crack", resulting in a deposit of carbon on the roller shaft. Over time, this can build up and the turbo will eventually seize. With a fully-synthetic oil, this chemical action doesn't happen.

Now the disclaimer! This is not a recommendation to stop allowing your car to cool down after the turbo's been running! I use fully-synthetic all the time and still always allow the engine to cool down after a run. There are a lot of other components in the engine bay that wouldn't like the kind of heat that an uncooled turbo can create.

Brian

johnfelstead

guys, stop talking poo

Rally drivers do allow the engines to cool before they switch off unless they have a crash, the same rules apply to a rally car as a road car when it comes to looking after a turbo.

The best way to cool a turbo is to run the car off boost on the road, sitting stationary at iddle is not as good as there is no airflow over the turbo.

you are doing 2 main things when allowing the turbo temp to stabalise at its coolest running temp. firstly you are trying to reduce the temp in the turbo shaft so that when the engine is stopped your arent frying the oil in the bearing, doesnt matter what spec the oil is, it will fry if you switch off a WRC car after it has been on stage, they use a miram shaft in order to cope with the temps generated from the ALS and run significantly hotter than a road turbo. secondly your are trying to protect the cylinder heads from heat soak, it is not unheard of for the heat from a turbo to be so high that if switched off immediately after a stage or due to a crash that it softens the cylinder head alloy to the point where it distorts and causes head gasket failure, in severe cases the head is junk as the softening is perminent.

As to ALS systems, all proper spec groupN cars use an ALS stratagy, its just not as noticable as the groupA and WRC systems as they are not allowed to modify the inlet sytems to use a full air valve controlled ALS system.

There are groupN cars and groupN cars, by that i mean only the top teams running groupN are using properly mapped ALS systems, a pukka groupN car can cost you in excess of £60K and yet you can buy a good spec groupN car for £20K, there is a reason for that extra £40K even though they are both groupN.

below is something i wrote a while back on how our groupA ALS system works on our cosworth rally car.

I run a Group A Cosworth rally car with Pectel P8 mountune mapped engine management, using ALS and water injection.
This is how it works.
Firstly, boost is controlled very acurately by using 2 fuel injectors as air valves, these feed the boost/atmospheric pressure to the waiste gate actuator, allowing minute and very fast acting boost control.
Secondly, the normal method of controlling engine iddle via an idle control valve, that bypasses the throtle butterfly is dispensed with, the static idle is set in the old fashioned way by a locked off bypass screw.
Thirdly, where the iddle control valve used to be, a new valve is fitted that has a solenoid controlled valve (looks like an engine inlet valve internally) that can open/close the throttle buterfly bypass orifice very qickly.
Forthly, a miram turbo shaft is used to withstand the massive increase in turbo temperature generated by ALS.
Fifth, there is no dump valve used on an ALS equipped engine, the whole point of ALS is to keep boosting the engine, even on closed throttle.
The way it works is that when you come off the throttle, for example braking hard into a corner, the throttle butterfly closes as per normal, once the boost drops to a certain level, the ECU starts to pulse the Throttle butterfly bypass valve, this has the same effect as you constantly stabbing the throttle on and off very quickly, this means that the engine is being driven by the ECU as though it wants to accelerate again, however this occilation of the throttle bypass valve is happening so fast, it has the effect of allowing the turbo to stay spinning yet produces no additional torque to drive the car forward.
The effect of all this is that massive heat is generated in the turbo exhaust side, which ignites all the excess fuel, there is no deliberate overfuelling going on to explode the turbo impellar area.
The most modern of ALS systems on the current world rally cars are far more efficient than a couple of years ago, which is why the ALS banging was less aparent this year on the RAC rally.
The turbo used in ALS equipped rally cars is smaller than you would see on a race car for two reasons. the first is that the FIA has a mandatory 34mm turbo inlet restrictor that limits air flow into the turbo, this means that it is pointless useing a large inlet turbine unit as the inlet could not flow any more air, secondly the lag would increase due to the inertia of the larger impeller.
The water injection system works by injecting a fine mist of water/air into the inlet plenum chamber when the boost/air charge temp reaches a certain level, the reason WI is used is to increase the effective octane rating of the fuel/air mixture to elliminate detonation, this allows far higher boost to be maintained, even in very hot climates.
This is not the same thing as intercooler sprays, these cool the external surfaces of the intercooler to help the cooling efficiency of the air/air intercooler.

Kev

And you can't argue with that .... you wanted a techie answer and you got just that ... great answer john, one of those questions you always wanted to know the answer to but were afraid to ask !!
I was told ages ago that the ALS system simply injected fuel into ...... well somewhere to keep the turbo spinning ... hence the some unburnt fuel igniting in the hot manifold/s and exhaust system producing the pops n bangs ... shows you how little I questioned him when he told me !

Thanx John
K

Gary Foster

John, you never fail to impress with you're replies do you I must remember never under any circumstances to ever ever argue with you on a techincal question ever.

Well, even a dumb-*** like myself understood the ALS thing, one question though, what does it stand for ? (yes call me Mr Thick of Thickington if you must

Gary

robski

ALS anti Lag system?

Gary,

you have to get him on one of his weaker subjects, decibels seems a good one

robski

p.s. JOhn if your reading this, does the Dax 4x4 use escort cossie running gear do you know?

Gary Foster

Dax Rush,

Thats interesting, I thought about one (not the 4x4, just the Cossie powered RWD one) - we'll thats not strictly true, I really want a Cossie Westifeld Zei (Johns thing) thing, but they are too rare, can't find any for sale.

I think you have to build the Dax you're self, that puts me off (all thumbs no fingers).

Don't know the answer as to running gear, but they're website lets you download an assembly list which might help.

MorayMackenzie

John,

Are you saying you can't run anti-lag systems on the road then?

Moray

johnfelstead

moray, of course i am not saying you CAN'T run ALS on the road, of course you can. I could run a 10 litre V8 on the road if i really wanted too, anything is possible.

But whats the point, i am talking proper ALS systems here with fully controlled air valves etc., not your pansy *** play things that some road ECU's can develop that may give very slight benefits in lag properties.

I dont class those setups as ALS systems because compaired to real ALS systems they do nothing.

Cheeky Jim

John,

Thanks pal!!

.....i thought I was talking ****, so I thought I would check with the **** meister himself!

I haven't actually got round to doing any mods on my Scoob, and I always did wonder how the rally cars got to sound so good....ho hum, I better think of another arsy question!!! LOL

Jamie

p.s. I am not remotely offended by John's answer, having seen some of the responses on here, me thinks some people really have lost the plot and have forgotten that this is actually a bloody good laugh! and not to be taken seriously all of the time!!

Cheeky Jim

Oh I forgot,

I did go off the idea once you mentioned 1200 squids!!

Jamie