Turbo Lag

Hi Glen,

I am no expert but I thought it was the dead band at the low end of the rev range before the engine is on boost.

On my navara, the turbo kicks in about 1800rpm

Thanks

TonyG

Turbo lag is the turbo dropping below the maximum boost, which means the engine cant make max power, anti lag items include things like a fuel injector which uses fuel injected into the turbine to stop lag on wrc cars when the throttle is backed off, which is why you hear them pop pop pop out the exhaust on over run.

Another anti lag device is using gas, co2, air pressure injected into the turbo to keep it on boost during gear chnages, or for low down rpm, or where the exhaust gases arent sufficient to get the turbo on max boost for max power.

So lag can be during gear changes, or before the turbo has built up maximum boost from low rpm.

A couple of things that may impact of the meaning;

1. diesel engine
2. petrol engine

light turbo diesel engines tend to operate on boost (ie usually have boost under constant steady driving conditions). Petrols are usually on vacuum under constant steady driving conditions.

Both will be slow to come onto more boost at 'low' revs (Cat D9 being an example exception - idle=900rpm redline=1200rpm). The operative word here is low - its relative to when the wastegate opens, or full boost achievable at desired revs is reached as the case may be.

The dead band may not always be at low revs (ie 3000rpm WOT acceleration on petrol will likely see some delay in coming to full boost avail at those revs @ max load).

The percieved delay will be greater on petrol engines, since they must transition from vacuum to positive pressure, while a (light) diesel will likely already have positive intake pressure.

These points will vary with engine, and its state of tune. Some engines dont even have a wastegate (medium / heavy haulage - until very recently).

That muddied the waters for you any??

4wd Monthly had an article a few months ago about some mob who sold replacement turbines which were of a slightly different shape. The result being there was much less turbo lag as they spun up just above idle.

Cheers,

Glenno.