Hi, I do performance and emissions testing of engines for an engineering consultancy, who in turn work for just about any OEM you could mention. If you're interested check out my company on www.ricardo.com
Readers of diesel car magazine may well have heard of us on many occasions in that magazine's technical features.
For those of you into diesels and powerbox/tuning devices etc, its true that OEM's leave a fair bit of slack in the final tune or calibration as we call it. They have to, as they try to have just 1 ecu calibration for a world market. Cost! Also in the latter stages of development we run best and worse build engines (tolerance testing) on the "world" calibration, so this has to be robust enough.
I have been reading some of the posts about these tuning boxes and maybe I can help clear up a few myths. For manual cars with lower peak torques than their auto equivalent, due to transmission max torque rating, I would think that fitting a tuning device may not be a problem as in such engines that I have worked on, the ecu knows what gear the car is in, and a fuelling map for each gear can be incorporated if required, which will limit max fuelling regardless of airflow (the way I believe some of the less advanced of these devices work - by making the ecu think the airflow is higher than it really is and hence allowing more fuel). Its usually only 1st and 2nd that the transmission may have problems with anyway. For example with the Rover 25 if I recall correctly we set the fuel maps to limit to 210 Nm in 1st and 2nd and 240Nm in all other gears. Manufacturers data probably just quotes the 240Nm but in the car in the lower 2 gears you would never know you were 30Nm short!
If you have a poor performer after checking air filter, boost hoses are still connected etc. its usually well worth looking at the air flow meter as these like all components have tolerances and you'd be amazed how a duffer can cost you 20-30% power/torque. If you have a mate with the same car ask if you can try fitting his temporarily. Its not a hard job, usually just sitting in between a couple of pipes held in with hose clips. VW's seem to be particularly prone to this from what I have heard/read.
My only concerns with tuning devices on diesels is this: In theory if you keep putting fuel into a diesel engine you will keep increasing your torque. Limiting factors (that we instrument all Diesel max performance engines for), are tailpipe smoke, turbine speed, turbine and compressor outlet temperatures and Pmax (peak maximum cylinder pressure). Adding fuel at a given speed will increase all of these, and I wonder if any, except smoke, are recorded or even monitored when these firms do their development. if anyone who works for Tunit, Superchips etc is reading this I would be interested to know how you do your development? I would be happy to be corrected if indeed you do monitor/record all these parameters! Most customers always seem happy though so I guess they're doing something right! I would say don't be greedy for too much more power/torque and maybe have your car mapped individually.
As for excessive black smoke this is simply unburnt fuel and whilst increasing fuelling will give you that extra torque, once smoke starts to become heavy any further overfuelling will increase the smoke further for a very disproportionate torque/smoke increase. It should also be viewed as an early warning that due to overfuelling you may well be approaching one of the limits mentioned earlier in this post. Remember more torque generated equals more heat to dissapate through cooling system and conduction through the engine componants themselves. Probably not a problem in short bursts but suffer this for a good few minutes whilst slogging up a hill with your van on the back and you could be heading towards early turbo failure, or in the case of excessive Pmax, bent con-rods! And yes I have seen this! The engine still ran quite well but was down on power/torque. It wasn't untill it was stripped that the cause of the loss of power was discovered - slightly bent rods! Also the front of your van will look like you've towed it through a coal mine and these hot particles can burn themselves into the glass fibre front panel making it impossible to clean off.
Another not uncommon cause of low power on a turbo diesel, is the intake hose collapsing (the one between airbox and compressor inlet)and a fault you would be hard pushed to find in your car unless you drove with the bonnet off or taped a camera phone to view it under the bonnet whilst driving. You would be unlikely to see this in a garage unless the engine was under load on a rolling road. Typically this fault would only occur under heavier loads, such as when pulling your laden car/caravan up a motorway incline or long steep hill at full pedal. This hose can become softened over time by the carry over oil (tiny droplets in the air) that gets fed into it from the crankcase breather. Remove any air pipe on your turbo/intercooler and you will find a bit of oil in there - dont worry too much, quite normal.
Finally for anyone who wonders why modern diesels are so much quieter its a lot to do with Pilot Injection! Pilot is a small amount of fuel being injected 5-15 degrees of crank rotation before the main injection. This gets the burn going so that when main injection is injected the sudden pressure rise in the cylinder (the cause of diesel knock) is vastly reduced and hence engine much quieter! Voila! Of course it plays hell with the emissions when cold but I won't go there now!
Here endith the lesson, blimey I never meant to get into it that much! Sorry if I have bored you but maybe a few found it interesting, no point having some knowledge if you're not going to share it.
Finally all the above are my personal opinions/experiences and not the official view of my company, and yes I work nights hence the strange times of my posts!
Cheers and happy caravanning. Andy.
Readers of diesel car magazine may well have heard of us on many occasions in that magazine's technical features.
For those of you into diesels and powerbox/tuning devices etc, its true that OEM's leave a fair bit of slack in the final tune or calibration as we call it. They have to, as they try to have just 1 ecu calibration for a world market. Cost! Also in the latter stages of development we run best and worse build engines (tolerance testing) on the "world" calibration, so this has to be robust enough.
I have been reading some of the posts about these tuning boxes and maybe I can help clear up a few myths. For manual cars with lower peak torques than their auto equivalent, due to transmission max torque rating, I would think that fitting a tuning device may not be a problem as in such engines that I have worked on, the ecu knows what gear the car is in, and a fuelling map for each gear can be incorporated if required, which will limit max fuelling regardless of airflow (the way I believe some of the less advanced of these devices work - by making the ecu think the airflow is higher than it really is and hence allowing more fuel). Its usually only 1st and 2nd that the transmission may have problems with anyway. For example with the Rover 25 if I recall correctly we set the fuel maps to limit to 210 Nm in 1st and 2nd and 240Nm in all other gears. Manufacturers data probably just quotes the 240Nm but in the car in the lower 2 gears you would never know you were 30Nm short!
If you have a poor performer after checking air filter, boost hoses are still connected etc. its usually well worth looking at the air flow meter as these like all components have tolerances and you'd be amazed how a duffer can cost you 20-30% power/torque. If you have a mate with the same car ask if you can try fitting his temporarily. Its not a hard job, usually just sitting in between a couple of pipes held in with hose clips. VW's seem to be particularly prone to this from what I have heard/read.
My only concerns with tuning devices on diesels is this: In theory if you keep putting fuel into a diesel engine you will keep increasing your torque. Limiting factors (that we instrument all Diesel max performance engines for), are tailpipe smoke, turbine speed, turbine and compressor outlet temperatures and Pmax (peak maximum cylinder pressure). Adding fuel at a given speed will increase all of these, and I wonder if any, except smoke, are recorded or even monitored when these firms do their development. if anyone who works for Tunit, Superchips etc is reading this I would be interested to know how you do your development? I would be happy to be corrected if indeed you do monitor/record all these parameters! Most customers always seem happy though so I guess they're doing something right! I would say don't be greedy for too much more power/torque and maybe have your car mapped individually.
As for excessive black smoke this is simply unburnt fuel and whilst increasing fuelling will give you that extra torque, once smoke starts to become heavy any further overfuelling will increase the smoke further for a very disproportionate torque/smoke increase. It should also be viewed as an early warning that due to overfuelling you may well be approaching one of the limits mentioned earlier in this post. Remember more torque generated equals more heat to dissapate through cooling system and conduction through the engine componants themselves. Probably not a problem in short bursts but suffer this for a good few minutes whilst slogging up a hill with your van on the back and you could be heading towards early turbo failure, or in the case of excessive Pmax, bent con-rods! And yes I have seen this! The engine still ran quite well but was down on power/torque. It wasn't untill it was stripped that the cause of the loss of power was discovered - slightly bent rods! Also the front of your van will look like you've towed it through a coal mine and these hot particles can burn themselves into the glass fibre front panel making it impossible to clean off.
Another not uncommon cause of low power on a turbo diesel, is the intake hose collapsing (the one between airbox and compressor inlet)and a fault you would be hard pushed to find in your car unless you drove with the bonnet off or taped a camera phone to view it under the bonnet whilst driving. You would be unlikely to see this in a garage unless the engine was under load on a rolling road. Typically this fault would only occur under heavier loads, such as when pulling your laden car/caravan up a motorway incline or long steep hill at full pedal. This hose can become softened over time by the carry over oil (tiny droplets in the air) that gets fed into it from the crankcase breather. Remove any air pipe on your turbo/intercooler and you will find a bit of oil in there - dont worry too much, quite normal.
Finally for anyone who wonders why modern diesels are so much quieter its a lot to do with Pilot Injection! Pilot is a small amount of fuel being injected 5-15 degrees of crank rotation before the main injection. This gets the burn going so that when main injection is injected the sudden pressure rise in the cylinder (the cause of diesel knock) is vastly reduced and hence engine much quieter! Voila! Of course it plays hell with the emissions when cold but I won't go there now!
Here endith the lesson, blimey I never meant to get into it that much! Sorry if I have bored you but maybe a few found it interesting, no point having some knowledge if you're not going to share it.
Finally all the above are my personal opinions/experiences and not the official view of my company, and yes I work nights hence the strange times of my posts!
Cheers and happy caravanning. Andy.
Facebook
Twitter