Diesel anti lag

[jarrus]

Check this out.....
http://www.competitiondiesel.com/forums/showthread.php?t=95023

The way I've interpreted this is that they just enlarge the post main injection phase to increase the egt's to spool the turbo while the engine isn't underload, a bit similar to how a petrol ALS works except you would actually need to have the main injection first as usual and then up the fueling on the post injection phase, when off the juice you could have a small main injection just to keep the engine moving then a big post to up the egt 's to keep the turbo spooled (on and off)

I suppose this is probably more for Paul's interrest but if any of you are like me then you'll find this very interresting anyway.

Discuss......

 

[Yugguy]

Can't you just change gear quicker?

 

[HDi fun]

VGTs go a long way to eradicating lag such as this anyway.

 

[jarrus]

Not like this, this will allow you to make boost while the engine isn't under load, VGT's just lower the boost threshold

 

[HDi fun]

I remember my Peugeot used to be totally lag free when the DPF was in regeneration. In this situation there's a tertiary injection phase which does exactly as you say ie. keep the EGTs high, thus increasing the exhaust gas velocity.

It's slightly wasteful though.

 

[jarrus]

Yes, it would be wasteful, plus the 2.2 hdi didn't have a vnt just a really small wastegated turbo. Wouldn't be worth pushing it any more over a remap with no other supporting mods, then again a GT15 on that size engine shouldn't have any lag, the last era of XUD9TE's has GT15's and K03's and they were lag free.

Also its not really the exhaust gas velocity that does it, you dump the extra fuel to increase the EGT's as the excess diesel lights off in the exhaust. I suppose you could do this with methanol as it has a low flash point and is cheap compared to diesel as in half the price....

 

[Zwaf]

Hope i'm not full off topic:

So, you said increasing EGT make exhaust fumes faster and that make spool quicker. Would incresing downpipe diameter produce some lag if my assumption is correct and that way exhaust gases would flow slower?

 

[jarrus]

Depends on power output, and how much exhaust gas you're trying to flow.

 

[Zwaf]

Thanks Jarrus! So recomendation could be: Make biger DP only if you bring more fuel into the cilinders and that way you could avoid extra lag?

Know it is kinda off topic and I wont make more questions after this! Thanks for tolerance!

 

[jarrus]

In a nut shell but to be worth while then you'd need to have the complete exhaust that size....

 

[davalav]

I don't understand how an engine can make boost whilst its idling... Defeats the object of a turbo doesn't it? Does the same principal work with a supercharger?

 

[jarrus]

The idea is to spool the turbo before you launch the car so the power is instantly there rather than launching it and waiting for the turbo to spool when the engine is loaded up.

Yes superchargers do offer a lag free alternative to the turbocharger but turbocharger is much more efficient because it uses the engines waste energy to spool itself rather than being driven directly from it sapping more power in the process.

Turbos use exhaust energy to spool themselves up and using this method you are creating a lot of heat and kinetic energy in the exhaust to move the turbine blades so the compressor spins and creates positive pressure in the inlet. The trade off here like I've said before is that your exhaust temps can get quite high if not kept under control.

 

[davalav]

Makes perfect sense. I thought a supercharger was more reliable? Exhausts can get crazy hot, what would be the best way chill charge temps? A meth kit similar to yours?

 

[jarrus]

Yes, injecting water into the inlet would be best thing to keep the exhaust temps down.