wrxsandy

...how does it work on rally cars? What causes those fantastic pops and bangs?
Cheers
Paul

wrxsandy

Anybody?

misty

do a search mate! this questions been asked time and time again.
dave

zhastaph

I'm not totally sure, but I think that just chuck a shed load of fuel into the engine which then explodes in the headers and the uppipe thus driving the turbo.

RB5-Black

AFAIK

Fuel is injected downstream of the turbo into the Exhaust. This causes the flames and bangs you see/hear.The explosion inside the exhaust causes the Turbo Impeller to spin up thus reducing the time that it takes the turbo to reach the required outlet pressure.

Craig

SUBTYPER

So if thats what ahppend then RB how does the GEMS engine management manage to get anti lag then. Cause that unit which we are doing a group buy on manages to create the anti lag flashes and bangs.

RB5-Black

you have to put fuel into the exhaust so that it burns !

you either do this on purpose or you run the car rich.... I don't know how that ECU works

SUBTYPER

Me neither I dont know how that Ecu creates it but I have been told with a flick of a switch you can get true anti lag So I am going to order one and apparently you cna adjust how much Antilag you can get so you dont kill your exhaust or turbo.

johnfelstead

You are wrong RB5-Black. Do a search.

SUBTYPER

Hi john.

So can you explain how it works then and by the way was really ncie to see you mising it up with the bikes and porsches on the Ring videos you did. Did you wear the brakes and tyres much.

RB5-Black

not far off for a blabbering fool

just wrong side of the turbo

scooby-si

got mine on a switch on/off ask john how it works hes alot more techie than me

greasemonkey

To answer the original poster's question on the rally cars, there are a variety of separate things that constitute the lag control strategies employed on modern world rallycars, from cutting spark to retarding the timing to modulation of the throttle butterfly to exhaust gas recirculation and more besides, so there's no one single explanation.

It's not simply a case of switching it "on" and "off" either - the Impreza WRC99 and onwards has three settings. The higher up you have it, the more effective the lag control is, but the more the throttle pedal starts to feel like a switch rather than a linear throttle pedal.

With the GEMS and similar programmable ECU's on a standard engine, again different mappers have different methods, but it's a combination of severely retarding the timing and continuing to inject fuel on a trailing throttle. The timing is retarded enough so the spark is fired when the exhaust valve is already opening, and thus the fuel mixture burns primarily in the exhaust manifold rather than the cylinder, with the resulting explosion driving the turbo rather than the piston.

BTW, SubTypeR, while the ECU in the GEMS group buy is capable of implementing ALS, are you actually getting ALS as part of the group buy? If so, are you getting the bits necessary to disable the brake servo assistance, ABS and so-on?


[Edited by greasemonkey - 2/1/2004 7:04:52 PM]

scoobynutta555

"the bits necessary to disable the brake servo assistance, ABS and so-on? "

You need to do this to have anti-lag?

greasemonkey

Yes, if you're talking about a proper ALS rather than just a few poncy exhaust farts.

The brake servo relies on vacuum in the inlet manifold. With (proper) ALS running, there will almost always be positive air pressure in the manifold, so no vacuum to drive the servo.

Even with the one-way valve in place, the ALS can give an extremely hard brake pedal (try pressing the brake pedal with your left foot while accelerating hard to see what this feels like), so the most consistent solution is to disconnect the servo altogether.

I don't know for certain that the ABS would have to go, but without the servo assistance, I'm not sure it'd work properly.

Again, all depends on whether you're talking about proper ALS, and how extreme an implementation you had, but issues like reduced exhaust, turbo and header working life, increased underbonnet temps, the need for more frequent oil changes and so-on all come into play. TBH, given the complications it causes, there's just no need for a toy like this on a daily driver, IMO of course!

[Edited by greasemonkey - 2/1/2004 6:39:31 PM]

SUBTYPER

Well according to Steve who is helping to run the group buy he is including ALS and Launch control (vehicle dependant on Launch control) on the deal price which is signifcantly reduced to normal price. I cant see why he would offer the system if you needed to buy other things to make it work. I would agree ALS is not required for everyday driving, would anyone feel that the AlS might reduce times on quarter mile and 0 - 60 runs if the boost is constantly their.

Thanks Greasemonkey (I wish I knew your name as i feel so rude calling you Greasemonkey) for the info on the brake servo. I will ask Steve Simpson who is supplying and mapping these systems if this will be affected. I have spoke to many a happy GEMs Customer in the past and from the previous group buy and they seem really happy with the mapping and ALS that can be individually mapped to the customers level. So a less fierce system can reduce wear and tear on the car.

I would be interested to hear from people that arent so happy on the GEMS front tho.

RB5_245

I have it, brakes wotk fine and the system works amazingly well, it's like 2 different cars when it's on.

Using 25% throttle opening don't remember the timing or fueling.

Launch control wasn't available though (MY99).

I never expected it to work half as well as it does, just expected some flames and bangs

Dave

greasemonkey

Maybe it just hasn't occurred to him? (no reason why it would!) All depends on the severity, how much boost you want at what rpm and so-on.

That's a bit of a piece of string question. You'd need it quite fierce to make a big difference under full acceleration, and then you're into issues with the working life of the components.

The areas where ALS comes in really handy are circuit racing and rallying where you're braking and on and off the throttle all the time. If all you're doing is quarter miling, my guess is that you'd gain just as much from removing the dumpvalve and fitting a spark cut device that will enable you to shift while holding the throttle open. This will keep the turbo spinning while being less stressful on the engine and other bits than a traditional ALS implementation.

Yeah, it all depends on the severity. As you say, there's a compromise between wear and tear and the effectiveness of systems like this. Same goes for gadgets like launch control. Sounds like a cool toy to have, but if it starts stripping gears or snapping driveshafts you might be slightly less happy.

Do you want a daily driver you can take quarter miling at weekends, or are you building an out and out drag car (with all the associated caveats about regular component replacement)? It's an important question for any potential customer to ask before they get their ECU mapped.

[Edited by greasemonkey - 2/2/2004 12:23:38 AM]