Anti Lag theorizing

ONLY for ADVANCED technical discussion about the 240sx!
Supafly
Posts: 423
Joined: Wed Oct 22, 2003 2:32 pm

Post

here's a topic for discussion: anti-lag setups and possible anti-lag setups.

i understand the use of anti lag setups in WRC cars as being pretty much just super retarded spark timing under high vac conditions that allows the flame front from the combustion chamber to travel out past the valves and through the turbine, essentially spooling the turbine when you're slowing down. but the shortcomings of doing this are burning valves, destroying turbos, and possibly destroying manifolds in the process. not so good in a street application.

but what about doing this in the same way that an actual turbine engine does it, basically an afterburner for your turbo. somehow inject fuel/air into the exhaust just after the turbine wheel and ignite it (if it's not already hot enough to ignite). the explosion/expansion of the burn would help pull the turbine up to speed, but not have the same nasty effects of a "bang bang" setup. the only shortcoming i can see here is if the ignition in the exhaust somehow began traveling toward the turbine basically doing the opposite of what i'm talking about.does anyone else have any input on some kind of anti-lag setup?

anyhow, this is just a topic for discussion, i don't really plan on trying it, i don't want to start some fly by night venture into making this and selling it, i just like to have good technical discussions. and mods if this needs to be in another forum by all means move it.:D


USsil80
Posts: 1949
Joined: Sun Sep 07, 2003 6:21 pm

Post

i belive that in the tracker puller(reall red neck there) that they do do something like that .. that idea would most likely work..just have to do some set up that when you have vacum in the TB that it some how would set fuel(mybe air but that should already be there) and ignite it ..mybe it wold be hot enough to ignite itself or you might need a spark..like one of those flame thrower kits for the very end of the zoust just mount it earler in the piping

User avatar
Hijacker
Posts: 14373
Joined: Wed Aug 13, 2003 4:57 am
Car: '92 240sx Convertible
'94 F-150
Location: Fredericksburg, VA

Post

one thing garrett was doing a few years back was designing a pre-spooling system that used pressurized engine oil to spin an extra fan on the turbine blade and effectively spool it up before the throttle was depressed. unfortunately it only ended up on a few heavy commercial applications.

User avatar
Hijacker
Posts: 14373
Joined: Wed Aug 13, 2003 4:57 am
Car: '92 240sx Convertible
'94 F-150
Location: Fredericksburg, VA

Post

btw, the setup you were talking about in your first post was the misfiring system, right?

DanMathers1
Posts: 41
Joined: Tue Jan 13, 2004 6:13 am

Post

How would you set it up so that the explosion was directional? i mean I can see it exploding in two directions causing the exhaust to get backed up, I may sound stupid, but how is this managed?

Supafly
Posts: 423
Joined: Wed Oct 22, 2003 2:32 pm

Post

tenkawa_akito wrote:btw, the setup you were talking about in your first post was the misfiring system, right?


yeah, the "bang bang" system as some call it, but it's basically just a pre-programmed misfire. it just does so under high vacuum conditions (more vac than idle basically) so if you let off under a load it will burn the charge out through the exhaust but it won't get screwy around idle.

Supafly
Posts: 423
Joined: Wed Oct 22, 2003 2:32 pm

Post

DanMathers1 wrote:How would you set it up so that the explosion was directional? i mean I can see it exploding in two directions causing the exhaust to get backed up, I may sound stupid, but how is this managed?


that would mainly be controlled by the direction that the fuel is spraying in. it's not actually an explosion but a controlled burn. the jet of fuel shooting out and burning would create a kind of pull on the turbine wheel. expanding gases tend to take the path of least resistance, which would be toward the end of the exhaust system in this case. the only thing i'm not really sure about is what effects it would really have on the turbo as far as decreasing the spool times and scavenging of exhaust on the engine under smaller loads.

DanMathers1
Posts: 41
Joined: Tue Jan 13, 2004 6:13 am

Post

right, but the how do you manage a controlled burn, obviously you can't have a spark plug or somthing because that would cause all the fuel to burn instantly, obviously it won't "combust" due to the fact that it's not under pressure, BUT how much pressure would it create in the piping when it burns up? I'm thinking its not gonna create enough pressure to cause a pull. You're gonna squirt gas into the exhaust, it's gonna burn, and that'll be it.

DanMathers1
Posts: 41
Joined: Tue Jan 13, 2004 6:13 am

Post

UNLESS, you could some how cause two seperate, ratarded "contolled burns" which whould pull the gas to follow the these "controlled burns" In which case I still don't think it would be worth doing

User avatar
Ligouri Rd
Posts: 449
Joined: Wed Oct 02, 2002 9:02 am
Car: '96 Nissan 240SX

Post

I was just taking about this in another forum. Anitlag systems I dont know if that injector idea will work. If the engine is tuned properly (I.e. not extremely lean...ping, ping) there should be very little oxygen left in the exhaust to burn the extra injected fuel. In a jet engine they have to re-inject fuel and air at the afterburner stage to use the existing heat to light off more thrust. I guess you cound inject NOS in with the fuel but, dont you need an entire fuel management system to go along with that?

What about using a compressed air charge at the exhaust manifold to spool the turbo. Were only taking about a brief charge here just at low rpm and at launch. Of course I don't know what the extra back pressure will do to the engine tryin to rev.

Toad[^_^]
Posts: 267
Joined: Fri Apr 25, 2003 3:22 pm

Post

Supafly wrote:here's a topic for discussion: anti-lag setups and possible anti-lag setups.

i understand the use of anti lag setups in WRC cars as being pretty much just super retarded spark timing under high vac conditions that allows the flame front from the combustion chamber to travel out past the valves and through the turbine, essentially spooling the turbine when you're slowing down. but the shortcomings of doing this are burning valves, destroying turbos, and possibly destroying manifolds in the process. not so good in a street application.

but what about doing this in the same way that an actual turbine engine does it, basically an afterburner for your turbo. somehow inject fuel/air into the exhaust just after the turbine wheel and ignite it (if it's not already hot enough to ignite). the explosion/expansion of the burn would help pull the turbine up to speed, but not have the same nasty effects of a "bang bang" setup. the only shortcoming i can see here is if the ignition in the exhaust somehow began traveling toward the turbine basically doing the opposite of what i'm talking about.does anyone else have any input on some kind of anti-lag setup?

anyhow, this is just a topic for discussion, i don't really plan on trying it, i don't want to start some fly by night venture into making this and selling it, i just like to have good technical discussions. and mods if this needs to be in another forum by all means move it.:D


Not to be blunt or anything but I work around jet engines 5 days a week. It's a little more complicated than igniting fumes. I mean it could work and everything but in order to make it work successfully the flame would have to burn continuously which requires a constant air supply. You would have to fabricate an intake system for the exhaust flame alone then you have to worry about the air/fuelmixture needed to maintain combustion. Add in the problems of heat, maintenance (trying to explain all of this to your empty bank account). Why not just do it the normal way? Thats right. Normal is no fun:D

Supafly
Posts: 423
Joined: Wed Oct 22, 2003 2:32 pm

Post

like i said Toad, it's just a discussion topic to get outside answering the same mundane "where can i get an SR" questions all day. if you can, enlighten us a little as to how the air/fuel mixtire is injected into the afterburner. i thought it could in fact use some sort of air pump for the air injection and of course some kind of heavy duty fine spray nozzle for the fuel. the ignition would happen either from some sort of sparking device like a sparkplug or possibly just a small metal tab sticking into the exhaust stream. generally a small metal piece with a sharp point just after the turbo will get hot enough to ignite fuel in the exhaust stream.

Nismo_Freak
Posts: 10314
Joined: Wed Jul 24, 2002 10:42 pm
Car: 89 Nissan 240SX

Post

Problem is... especially on smaller turbos your going to have the same problem as the original misfiring system with the exception of possibly the valves getting burnt up depending on where the injection was located.

Why do you think rotary engines eat up turbos so quickly? It's because their EGTs are high... it's also the reason they can spool large turbos relatively quickly.

User avatar
Hijacker
Posts: 14373
Joined: Wed Aug 13, 2003 4:57 am
Car: '92 240sx Convertible
'94 F-150
Location: Fredericksburg, VA

Post

misfiring systems are ok, but only on vehicle that are going to have engine overhauls very often. such as a WRC car. for street applications, I don't think they're feasable

DanMathers1
Posts: 41
Joined: Tue Jan 13, 2004 6:13 am

Post

I wanna hear more about the compressed air charge. After hearing all the other discussions, its obviously the only one that seems feasible now. Are you talking like a tank of compressed air, or could u compress it like a piston compresses the air and fuel in the engine, then release it into the manifold?

MikeMurphy
Posts: 824
Joined: Sun Feb 23, 2003 12:20 pm
Car: Guess
Contact:

Post

Just run nitrous before the turbo is spooled and it will help spool the bastard very quickly. Wont be IMMEDIATE, but it will cut down the time considerably.

Supafly
Posts: 423
Joined: Wed Oct 22, 2003 2:32 pm

Post

MikeMurphy wrote:Just run nitrous before the turbo is spooled and it will help spool the bastard very quickly. Wont be IMMEDIATE, but it will cut down the time considerably.


i don't fancy the idea of spraying something that comes out of the line at something around negative 120 degrees directly into a hot turbine housing/wheel that's sustaining 1300+degree temps.

MikeMurphy
Posts: 824
Joined: Sun Feb 23, 2003 12:20 pm
Car: Guess
Contact:

Post

into your intake not straight into your turbo manifold ;)

Nismo_Freak
Posts: 10314
Joined: Wed Jul 24, 2002 10:42 pm
Car: 89 Nissan 240SX

Post

MikeMurphy wrote:into your intake not straight into your turbo manifold ;)
What good would that do honestly... your not going to pressurize the intake system by the time 90% of the turbos everyone is running spools. It might make a little more power because the air injection is cold but on top of that your just introducing alot of air into the system that the ECU hasn't accounted for... and I don't care to rebuild my engine.

In all fairness if you select a good turbo you'll get timely spool up... there isn't really any miracle way around it else you'd see it on every shelf of every peformance store.

User avatar
Hijacker
Posts: 14373
Joined: Wed Aug 13, 2003 4:57 am
Car: '92 240sx Convertible
'94 F-150
Location: Fredericksburg, VA

Post

the whole point of the nitrous spray or CO2 spray is to prespool the turbine, but the nobody has ever figured out a way to solve the issue of spraying a very cold air stream onto a extremely hot turbine and not cracking something. the pressurized oil squirter on the third turbine idea that garrett had is probably the closest you'll come to that

Toad[^_^]
Posts: 267
Joined: Fri Apr 25, 2003 3:22 pm

Post

Why not use sequential turbo? Baby turbo spools up papa and you're good to go.

Squirrel
Posts: 48
Joined: Sat Mar 15, 2003 9:43 am

Post

Speaking of sequential I guess that at one point garret was working on a sequential compressor turbo, that is two compressors on one turbo, with on fed into the other, to make some ridiculously large amounts of boost. Just thought it was kind of interesting.

MikeMurphy
Posts: 824
Joined: Sun Feb 23, 2003 12:20 pm
Car: Guess
Contact:

Post

nitrous is going to cause expansion far more than ambiant air, thus "more" expanded air flowing through the turbine.

This whole idea seems very sound to me. And why would it not be metered?

maybe im just totally wrong

Toad[^_^]
Posts: 267
Joined: Fri Apr 25, 2003 3:22 pm

Post

Squirrel wrote:Speaking of sequential I guess that at one point garret was working on a sequential compressor turbo, that is two compressors on one turbo, with on fed into the other, to make some ridiculously large amounts of boost. Just thought it was kind of interesting.


I remember that! They had a brief article about it in Sports Compact Car (I think)Whatever happened to that thing?
MikeMurphy wrote:nitrous is going to cause expansion far more than ambiant air, thus "more" expanded air flowing through the turbine.

This whole idea seems very sound to me. And why would it not be metered?

maybe im just totally wrong


I think that nitrous is definetly potent, but its kind of like taking steroids. It isn't really the cars ability, its just bottled "power" that can be depleted and replenished at a whim. Real power is static.

Squirrel
Posts: 48
Joined: Sat Mar 15, 2003 9:43 am

Post

I THINK that it is still being developed but mostly for diesel engines as cars simply can't handle the kind of boost that its was designed to produce. It was based on the fact that a turbos ability to compress is a ratio such as 2:1 and not a set limit i.e. 14 psi. So assuming a 2:1 compression ratio for both compressors that would be 4:1 overall. That would be 4 bar (~59 psi) of boost! I was kind of wondering about the lag on that thing, I assume it would be kind of bad as there would be a lot more mass to get spinning with two compressors and all.

Toad[^_^]
Posts: 267
Joined: Fri Apr 25, 2003 3:22 pm

Post

Squirrel wrote:I THINK that it is still being developed... 2:1 and not a set limit i.e. 14 psi. So assuming a 2:1 compression ratio for both compressors that would be 4:1 overall. That would be 4 bar (~59 psi) of boost!...


*Drool*

But imagine if you could reinforce a block with sleeves and forged internals and what not and run 59 psi... Maybe an onboard air compressor (like an airtank) could aid in spooling the turbo. Think about the top end capability!

Squirrel
Posts: 48
Joined: Sat Mar 15, 2003 9:43 am

Post

It would great. but it would also probably require 7:1 compression, 300 octane fuel and some damn strong pistons

jrc90240sx
Posts: 455
Joined: Mon Jul 29, 2002 9:21 am

Post

I like N2O injected into the exhaust manifold. it wouldnt need a great amount as it would expand greatly and be heated up to the temp of the other exhaust gas. it might even help control the heat temp of the exhaust gas.

Other options is a TC/SC hybrid system with a cluth pulley on the SC so it could turn off and be bypased when they turbo created enough boost. or you could just combine them to make even more boost. you would need a roots type blower so you make almost instent boost at low rpms.

Other options is a small hp N2O system that gives you a small amount of power to in the lower RPM to help leavel out the torque curve.

nightwalker
Posts: 79
Joined: Mon Nov 24, 2003 12:01 am
Car: 240sx

Post

I learned how the so called mis-firing system works, AKA anti-lag system from a retired CART pit mechanic.

The misfiring sytem basically does not let the engine go into vacuum. There is a port that is added into the throttle body to keep the turbo spinning and the air pressurised, whether it being atmospheric, or 1-2 psi. The popping occurs because even as the car is at idle, there is excess fuel being dumped to keep the mixture from leaning out. So as soon as you get on the gas, you are at boost.

He said last he knew, the anti-lag system was being sold by some company in europe, (was it Haltech?) but didn't know if it was available over here. The system also puts a huge strain on the turbo, and manifold. He says that the turbo and manifold glow extremely red from using the setup.

But don't think you can just manually set something like that up. The system itself uses its own ecu, the engine is tuned to match.

I really thought about it, and researched it. The system is actually very costly.

DanMathers1
Posts: 41
Joined: Tue Jan 13, 2004 6:13 am

Post

Well, I think we all know it's going to be costly, no matter what the solution is, if it weren't it would be on every shelf. NOw, the idea of N02 injected into the exhaust manifold. I think most of you skipped over it when tenkawa_akito

Quote »the whole point of the nitrous spray or CO2 spray is to prespool the turbine, but the nobody has ever figured out a way to solve the issue of spraying a very cold air stream onto a extremely hot turbine and not cracking something. the pressurized oil squirter on the third turbine idea that garrett had is probably the closest you'll come to that [/quote]

You're talking about expansion. The expansion is caused by the fact that the cold compressed air expands when heated. That's a great idea, if you could use somthing that wasn't so cold.

Now, I wasn't the best chemistry student, and since I was in Chem last year I have forgetten most things I did learn, so I could be wrong, but when the pressure is increased on a gas, isn't it supposed to get hotter?

If that were true then you could use a non-combustible gas in this scenario, one that when compressed, not necessarily tured to liquid could be shot into the exhaust manifold at a relativly hot/warm temp and create enough pressure w/o causing the piping to crack?

Of course if gases get colder under pressure I'm completely wrong, but if I'm right......


Return to “240SX Technical Forum”