tuning of diesel engines

[edtf]

I picked this up from Berrima diesel center and consider it as a good read:

[SIZE=2]If you’re getting your diesel engine tuned or considering increasing the power of your diesel, it’s important to consider the exhaust gas air-fuel ratios (AFRs.) AFR is the mass ratio of air to fuel present in an internal combustion
engine. It is an important measure for reducing pollution and performance tuning. AFR is commonly misunderstood,
but it is extremely important if you are towing a heavy caravan or have a heavily loaded motorhome. I have many years experience in tuning. It is best said that a diesel begins to smoke when the AFR gets below 15-14:1 for a non-turbo and 16-15:1 for a turbo-diesel. Remember, a diesel doesn’t need a perfect AFR to run and operate, but a petrol engine cannot run much either side of its perfect AFR of 14.7. In a diesel, too much fuel (a low AFR) means smoke and engine heat. Not enough fuel (a high AFR) means clean running and lower engine temperatures. The following is a guide for tuning diesels. A non-turbo diesel, such as a Toyota Coaster with 1HZ engine, would generally be tuned in between 15-16:1. This means it is running just on the clean side of exhaust emissions. Any lower in AFR and it may begin to smoke. An aftermarket turbocharged diesel, such as a Toyota LC100 with 1HZ engine, would be best running at around 19-20:1 AFR or higher under full load. The reason for the higher[/SIZE][SIZE=2] and l[/SIZE][SIZE=2]eaner (oxygen rich, fuel lean) AFR in this application of aftermarket turbo is so that you know the engine will last for a very long time at that exhaust gas level. While it turbos safely, it wasn’t made for turbocharging. A factory turbocharged diesel, such as a Toyota LC100 1HD-FTE or an Isuzu NSeries, would be running an AFR from new
of about 20-22:1 or higher under load. While you may get a tune up performed or a chip fitted on your diesel,
always make sure you check what the AFR reading is before and after. So often I hear about big power gains had from a diesel tune or performance modification. Then I find out that there were no AFRs supplied to support the gains and changes made. Remember, for the safety of your diesel always ask for the behind the scenes figures. These include the AFR, to assure you really know ‘how’ the power was achieved.
-ANDREW LEIMROTH[/SIZE]

[niky]

Slightly incorrect there. Gasoline engines can run at AFRs in many different ranges. Gasoline engines run cleanest at 14.7:1, but for maximum power, 13-13.5:1 is best. To ensure safety, gasoline engines sometimes run as rich as 10-12:1.

Under light loads in open loop, modern gasoline engines can run from 16-20+:1... especially with proper EGR usage and/or stratified direct fuel injection.

[babkalakal]

Under light loads in open loop, modern gasoline engines can run from 16-20+:1... especially with proper EGR usage and/or stratified direct fuel injection.

the condition that you are describing to here is actually a "lean burn" mode.

[niky]

the condition that you are describing to here is actually a "lean burn" mode.

I know. I keep mixing up open-loop and closed-loop tuning... I was actually talking about closed-loop mode.

On some new cars, they even run an "ultra-lean burn" mode... that's where direct injection comes in.

Mazda goes even further by using ultra-high compression and cooled EGR. I can't wait to see how these new engines perform.

Too bad HCCI development is so slow... those can run even leaner, and use pre-ignition to power the car in ultra-lean burn... in other words, they burn gasoline like diesels... without using spark plugs... in closed-loop mode, but this requires very sophisticated knock sensors, which still cost too much.

[babkalakal]

Yup. ako din nalilito meron GDI, FSI, TFSI may hhalong marketing terms na pero puro gasoline direct injection din.

I think you are referring to Mazda's sky drive family of engines.

HCCI is new to me I had to look it up pa hehe. Pero from what I read I suspect we would see a resurgence of the gasoline engine in response to the current popularity of CRDIs kun madevelop nila ito. Sa Europe currently ata there are some small gas engines that give CRDIs a run for their money in terms of fuel consumption and combined with a turbo these gas engines may also rival the torque figures of the diesel but over a wider range.

Talaga ang bilis ng engine tech. ngayon di na pwede i-distinguish ang gas and diesel as either spark-ignition or compression-ignition kun wala nang spark plugs. And I find it quite ironic that pre-ignition is used to fire up the fuel in the combustion chamber where before hand pre-ignition/combustion (detonation/tope) would be the beginning of the end of your engine.

OT: i hear that Porsche is returning to the top flight le mans racing class (LMP1). I'm quite interested to see which route they would take in terms of engine choice. either inherit the diesel technology of their sister company Audi or go with their own gasoline engine.