So you’ve changed your oil, oil filter, and air filter. You’ve even found the DIY on how to change your fuel filter. So your service is done and your car feels better, right! But when was the last time you had your injectors calibrated?? Why do I need to have this done? Putting it simply no two injectors are made the same. Each injector has a slightly different fuel flow rate. When your ECU tells your injector to pulse and inject fuel unless it knows the fuel flow rate of each injector the pulse rate for all the injectors will, by default, be the same. So if you have an injector with a slow flow rate then less fuel will be injected into a cylinder and vice versa. Yes during driving the engine will request more or less fuel depending on the load on the engine but this is done uniformly across all injectors. The ECU needs to identify the flow rate of each injector. It can then be calibrated to adjust the length of the pulse required to ensure the same amount of fuel is being inserted into each cylinder. Surprisingly this calibration is not performed in the factory when the car is built, and it’s not checked by the dealership before the car is sold. Neither is it checked when you take your car in to have it serviced. Unless you specify this to be done it’s likely never been done. Where can you get this done? Anywhere with a HDS. So this is usually not the sort of job an independent mechanic can do as they don’t have the software. You will either need to take the car to your main dealer, I think the going rate is about £70 for this, or IchibanAccord (CJ) has very kindly offer to give this service along with a full health check using HDS equipment for members who have reached a specified level of posts. I chose to make the journey up to see CJ. Before calibrating my injectors he performed the following using his HDS equipment: Checked and cleared all historic error codes stored on the ECU for all systems including the VSA. Ensured there were no current error codes showing. Checked the operation of the EGR valve and IMRC valve. Checked the fuel rail pressure and efficiency of the fuel filter. I’m sure there are other things which CJ checked as well but I can’t remember those, but I’m sure he will mention any I’ve missed. After checking all the other systems operated correctly he then checked the fuel flow of the injectors. Mine had the following approximate results: Cylinder 1: -1% Cylinder 2: +2% Cylinder 3: -1% Cylinder 4: -1% As CJ pointed out number 2 cylinder was doing all the hard work. The ECU was then recalibrated to adjust for these results. The results To be clear the car was not performing badly by any means before I had the calibration done. None of the things which I've now identified as differences before were ever considered to be an issue. I was happy with the economy and performance of the car and only had the calibration done as a check to make sure the car was running as well as it could. I’ve broken the results down into different categories to best explain the differences I’ve felt in the car before and after the injector calibration. Cold start-up Before: When I started the car recently I would feel a slight stuttering from the engine until it was warm. Also when I pulled away for the first time I used to get a slight characteristic diesel knock for the first 300 yards of my journey After: The stuttering on cold start-up has now gone completely, due to number 2 cylinder now not solely doing all the hard work, and the severity of the knocking has been reduced and stops sooner as the load is spread evenly across the engine. If I don’t accelerate hard the first time I pull away (which you shouldn’t do anyway) it’s actually possible to hear no diesel knock at all. Acceleration Before: Below approx. 2000 RPM (off boost) when accelerating the turbo lag was around a second. And when the turbo kicked in there was a huge step in power from off boost to on full boost Above approx. 2000 RPM when accelerating the turbo lag was slightly less but there was still a big step in power when going onto full boost. The engine also used to feel like it was reaching its power limit between 3000-3500 RPM. After: Below approx. 2000 RPM (off boost) when accelerating the turbo lag has been reduced to around half a second. Now when the turbo kicks in the power delivery is progressive and quick but smooth. The huge step onto boost has now disappeared. Above approx. 2000 RPM when accelerating the turbo lag has completely disappeared. The power delivery is again progressive, quick and smooth. I can really feel the variable vane turbo working to reduce the lag and deliver power at low boost. It feels strong and consistent right up to the red line. The engine now feels like it wants to rev a lot freer rather than having to feel like I’m working it hard to get it to work higher up the rev range. Lift off/ Coasting Before: This was more noticeable on motorway driving. When lifting off and letting the car coast in gear I notice the car used to slow down quicker and lose momentum more than my previous petrol car. I put this down to a characteristic of the car being a turbo diesel than a naturally aspirated petrol. After: Now when lifting off the car feels like it wants to coast a lot more and carry the momentum without the reduction in speed. This is because the engine now revs freer and isn’t holding the car back. Cornering This section only applies when you’re driving with the intention of getting round the corner quickly. Before: I used to throw the car into the corner, press the accelerator and wait for the boost to kick in by which time I’d already be at the apex. Then accelerate out the corner and usually if it’s a tight corner because of the big step onto boost the front wheels would spin. After: Now I throw the car into the corner, press the accelerator and instantly get a response. Because of this I can now balance the car into and through the corner using the accelerator. And because the power is progressive rather than a big step the car retains a lot more grip through and out of the corner. The experience is far more rewarding and the car now puts a smile on my face when I want to push the car. Economy Before: On the way to meet CJ I was travelling up the motorway with the flow of traffic (approx. 70-80 mph) driving reasonably economically i.e. no hard accelerating etc. and the car returned 55mpg. After: On the way back despite having the air con on and repeatedly accelerating to play with the new found low down progressive power the car still returned 55 MPG. When I calmed down and maintained a steady 70 mph for the last 30 miles of my journey without trying to drive economically the car returned 61 MPG. I think the increase in MPG is down to 1 factor. This is that the engine was always slowly trying to slow the car down and the amount of acceleration required to overcome this and maintain its speed was ever so slightly more than needed to achieve the hyper mileage figures. Now the engine runs freer the car requires less acceleration to maintain its speed and thus higher MPG figures are now achievable. Overall The car feels transformed. The engine now feels far more refined and the car is far more driveable. As mentioned above the engine revs easier. It accelerates better, smoother, and stronger from low RPM. The power is there instantly from higher RPM, and the power delivery is constant right up through the rev range. Also the engine now feels freer and want so ‘run on’ far more than it did instead of hold itself back. Am I happy I got it done? Definitely, I wish I’d had it done a long time ago! The car now puts a smile on my face every time I drive it and point it into a corner. I recommend everyone gets this checked on their car because it’s very likely it’s never been done. Your car will thank you for it. Big thank you to CJ for taking the time to see me on his weekend, especially as he’d managed to double book himself.