A Question about Anti Lag...

[RSmith]

Hi guys,

In my quest to know more I've been buffing up about anti lag. And I've soon discovered that 90% of people don't have a clue what it is, and the other 10% can't explain it very well.

I'd just like to clarify that anti lag basically retards the ignition of an engine to the point where maximum cylinder pressure occurs very late in the compression stroke so that the engine maintains high exhaust pressures and temperatures while keeping the torque on the crankshaft low. This means the turbo is kept spinning between shifts etc.

What I don't get is then they talk about a bypass valve system from the turbo's compressor which feeds air during anti lag operation to the exhaust system so the fuel can combust??? I'm getting confused... is this another type of anti lag system where unburnt fuel is introduced to the exhaust system and picks up so much latent heat from the pipes and turbo it ignites causting a pressure rise? Can someone help me out? :blink:

 

[HDi fun]

Exhaust driven superchargers do rely upon exhaust gas velocity for effective operation. Your point is an interesting one. I think you're wrong, nevertheless. THe only way to make make a car accelerate faster is to increase the crank torque, which translates to an increase in torque at the driven wheels.

 

[claymore]

I inject fuel directly into the exhaust manifold, (Very simple system, I use an arming switch on the dash, then have a micro switch on the throttle linkage at closed throttle position which triggers a nitrous fuel solenoid) but be aware you need a good stock of spare turbos.....lol

 

[HDi fun]

I inject fuel directly into the exhaust manifold, (Very simple system, I use an arming switch on the dash, then have a micro switch on the throttle linkage at closed throttle position which triggers a nitrous fuel solenoid) but be aware you need a good stock of spare turbos.....lol

So what Claymore's driving is basically a horizontal chimney fire

 

[claymore]

So what Claymore's driving is basically a horizontal chimney fire

thats about right

 

[Loz]

 

[HDi fun]

Nope, you've lost me now.

 

[Loz]

It's a ROFL-copter, I found your "horizontal chimney fire" quite funny! :bigsmile:

 

[HDi fun]

My Peugeot had something similar as well. Cunningly disguised as a diesel particlate filter.

The exhaust temps were unbelieveable during filter regeneration.

 

[RSmith]

I inject fuel directly into the exhaust manifold, (Very simple system, I use an arming switch on the dash, then have a micro switch on the throttle linkage at closed throttle position which triggers a nitrous fuel solenoid) but be aware you need a good stock of spare turbos.....lol

So basically, I'm presuming the solenoid has been drilled directly into the exhaust manifold / tract to provide anti lag during shifts? I'm guessing the heat from the exhaust is enough to set it off to create the turbo spooling pressure rush.

I know what you mean about turbo mincing! Just to clarify I'm just trying to get my head around the ALS systems commonly used on race and rally cars.

 

[HDi fun]

Race cars and rally cars are not totally immune to emissions and roadworthiness regs. Most rallys incorporate some road stages.

Turbo lag is not the massive deal it was 30 years ago. With the advent and universal adoption of fully managed engines it's possible to work around turbo lag. Variable geometry turbochargers have probably made the biggest single contribution, however.

Turbocharging is not new. It's been used in commercial vehicles, railway traction and static engines for decades. Piston engine aircraft makers also have employed the same techniques.

There is also a question to be raised: When is turbo lag not turbo lag?

Traditionally, turbo lag meant waiting until the engine hit a certain point in its rev range. Early turbo installations in cars were pretty crude.

What's more commonly encountered is actually turbo spool up time. This can impede progress anywhere in the rev range.

With ever more sophisticated and lighter materials from whcih the turbocharger is made, the spool up time can be reduced almost to the point that it's not noticeable to the driver of the car.

If that's not enough, then the current fashion for dual sequential turbos offer an even better solution.

I am talking mostly from a road car dirveability perspective. Race cars don't need to be flexible at 1300rpm when Granny engages 6th gear.

But, the principles are very similar.

Diesel engines lend themselves very well to turbocharging for one simple reason - they have no throttle.