Hi all,

I was just wondering if anyone has any info on or knows a team that are ruhnning a combustor can anti-lag systems? Its basically what the Scooby guys call a rocket box. I have heard that they allow WRC cars to fully spool a turbo whilst the car is basically sat at idle. just thinking it would be brilliant for drag racing as you could basically dial in whatever boost you wanted to launch at, it would be the same each and every time and they are much less harsh on components (ie turbos and manifolds) than convetional ignition retarding systesm (bang-bang antilag or a 2step).

For people that dont know how they work, you basically turbo your turbo(s) into turbines. you bleed off some of the boost from the intake track and inject fuel. This mixture is then burnt in a can that is conected to the exhasut manifold.

As said above it has been used in WRC (World Rally Championship) rally cars for several years now, but there is not alot of info out there.

Thanks,

Chris.

 

1) A "scooby" "rocketbox" is a box that gets strapped to the roof for carrying cargo.
2) Go here: https://ls1tech.com/forums/forced-in...turbo-lag.html and do a "Find" on the page for "the WRC rally" (without quotes).

 

Anti-lag contraptions are actually VERY destructive on turbos. Manifolds also have a tendency to crack at weak points.

The idea is cool, but unnecessary for turbo drag cars where revs are kept high and weight is the enemy. WRC uses them because they have to slow down on turns and need to hit full boost again ASAP. If you have a dedicated drag car, use a bov that doesn't relieve as much pressure so your compressor surges but not enough to lose all positive pressure in the piping.

 

Combustion can systel anti-lag systesmare actually much less stressful on the turbo / exhaust / engine as the event can be much better controled than normal bang-bang style antilag.

By the way this is the methed used bbyu all WRC team that i am aware of. conventional anti-lag hasn't been used in WRC for many years now.

Imma, see your point about having revs, however i was thinking more about the launch. Just thinking it would be nice to be able to dial in whatever boost you wanted, from min to max, whilst sat on the line.

Chris.

 

Ahhh gotcha. I'm pretty familiar with WRC setups. They're pretty advanced boxes with all kinds of checks and electronics and a whoooole lot of over engineering. Not sure exactly how they work as their piping is insane with all kinds of hoses and vac lines going into them.

Maybe something like a big *** helium injection right into the exhaust housing would get that wheel spinning

 

Hence the reason this is in the Advanced Engineering Tech section.

 

From what i have gathered you need to add energy to the exhuast gasses to make the turbo(s) work better. simply adding product alone wont do that much. the easlist way of adding energy is heat. by delaying the cubsion event till the exhasut valves are open means there is more heat in the exhaust gas when it reached the turbo. there would still however bee the exact same amount of gas as you would tbe burning the same volume of air/fuel.

however with a cumbusion can system you are burning extra fuel and thus putting more energy in to the exhaust gasses.

Chris.

 

you guys are over complicating this a bit, anti lag is simply a PCM controlled event that retards the timing to the point that you are combusting your mixture in the exhaust which causes the turbo to spool. usually its linked to your clutch pedal switch so when you engage the clutch your timing goes back to normal and you take off the line with boost ( not full boost but 50-75% usually)

 

The above is conventional bang bang antilag. Combustion can is different and used on WRC cars to help keep them in boost ALL the time, oh and when i say boost i mean max boost!

Its discribed above. All i was thinking is it would be nice for a drag setup to A) be ablbe to spool pretty much ANY sized turbo regardless of size and B) be able to leave a set boost presure EVERY time.

 

http://en.wikipedia.org/wiki/Antilag_system
References Turbo Anti-lag systems - A technical description from rallycars.com http://www.rallycars.com/Cars/bangbang.html


Today's WRC cars also use anti-lag systems which feed air directly to the exhaust system. The reason is that these systems are more refined, more effective with advanced computer control, and also quieter. Today this kind of system has reached such a refinement that it’s even possible to use the system in a road car. A recent example is the Prodrive P2 prototype. The system works by bypassing charge air directly to the exhaust manifold which acts as a combustor when fuel rich exhaust from the engine meets up with the fresh air from the bypass. This will provide a continuous combustion limited to the exhaust manifold which significantly reduces the heat and pressure loads on the engine and turbocharger. With the latest anti-lag systems the bypass valve can not only be opened or closed but it can actually control the flow of air to the exhaust manifold very accurately. The turbocharger is fitted with a turbo speed sensor and the engine management system has a map based on throttle position and car speed which is used to find a suitable turbocharger speed and boost pressure for every condition. When the engine alone can’t provide enough exhaust energy to reach the turbo speed/boost demanded by the management system, the bypass valve opens and exhaust manifold combustion begins. This not only reduces turbo lag, but it also allows boost to be produced at very low engine speeds where boost was previously limited by compressor surge or exhaust energy. With relatively high boost at low speeds, this makes the low end torque superior even to large naturally aspirated engines. The system is quite loud and is banned on some rallies because of the noise it produces.

http://www.rallycars.com/Cars/bangbang.html
This link has a very good article on the subject

 

Thankls for posting the links. Very usful for people that dont understand how anti-lag works. One note on the combuster can systems, they actually inject their own fuel as well as regulate the bypassed air (using air Injectors). also as this is a contius burn (a bit like a jet engine) the loads on the turbo are MCUH more controlable.

If anyone has seen full on bang-bang antilag in action you will know how loud they are! I have had the pleasure so seening both a Group A Ford Escrot Cosworth rally car and a selection of WRC cars up VERY close and peronsal. THe WRC cars are MUCH quiter than the older escort rally cars. the Escorts used to sounds like machine guns every time they backed off into a corner. you could hear the banging of the exhaust well over half a mile away through dense froest stages. On the other hand the WRC cars are MUCH quiter.

If you youtube anti-lag you will see loads of vids showing just hoe violent anti-lag can be (im talking 3-5 foot flames here). but these combuster can systesm just sound like the engine reving against a 2-step limiter!

Chris.

 

All this anti-lag stuff seems too complex than it needs to be. It seems like it would be a lot easier making a sort of boost buffer on the cold side of the turbo. Imagine an in and out 2 way 10lb nitrous sized bottle able to hold many times the PSI the amount of boost your engine will be able to use, then have a big turbo feed that bottle and have a slow bleed off checkpoint from that into your intake piping, then the pipe from the bottle to your intake would have the normal blow-off valve set for your amount and then when you open your throttle you get instant boost and by the time the tank starts to get below the amount of boost it needs, it will be filling up, if your going WOT a lot like in a race anyway. Also the bottle could have a heat sink on it and it will give much more surface area to cool, especially since it should drop tempuratures after it get depressurized from being in the bigger higher pressure tank also. Gas mileage would also be better with this adjusted for smaller turbos and daily driving I would imagine.

So here is a pic as ref and some PSI numbers as example lol

---------high boost piping 35psi+--------Bled off boost piping 6psi
-----(o)===================[____}====================( )/\\\\
-----turbo-----------------------Bottle-------------------Throttle Body/Intake


Umm just thinking out loud, did I make any sense to you turbo guys?

 

Actually it makes alot of sense! lol the WRC guys have tried this. They used to put a tank in the rear bumper conected to the intake. This effectlvy increased the size of the plenum and allowed them to have several times the engine volume of air at 35psi +. Not sure it worked to great though as you still have to fill the bottles/pipework up. this reduces responce time of the turbo (if you double the volume of the pipework it will take twice as long to double the boost presure in that pipe).

Chris.

 

You can see the pipework and almost the solenoid valve they use to direct air into the exhaust.

But really there is little point for 99% of people when simply opening the throttle blade and allowing air to pass through the engine will work almost as well, and cost virtually nothing.



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