Hey Accorders 🙂 Welcome to the place where we can make your Accord to be a real Honda. I think that at least once you had an idea that your car looks much more agile faster and aggressive than it moves on the road. Sad but true. Don’t worry, we can fix this and bump its performance and acceleration to a Type-R class. The engine in these cars can do much better, it has a great hidden potential that is sleeping and its possible to awake it.
It was a good joke of someone there to put such a nice and powerful engine into a civil car. And someones bad joke was to factory tune it like that. Why? You better ask Honda.
So what we have here… K24 engine, a big brother of the famous Type-R K20. Honda added 400cc of displacement for low-end torque to push a heavy chassis but tuned it for civil usage without spikes, burnouts, with a calm and predictable behaviour for every average Joe. Lots of things been made to bump comfort more than performance in it.
Honda i-VTEC K-series engines are famous for their heads, they are breathing extremely well and let to burn lots of fuel, producing tons of power. These engines are also extremely well designed, balanced and assembled, this allows them to rev that high. So comparing K24 and K20 we can see same head design, both have high compress ratio, both can rev high, but K20 blows like a hot champagne and big bro is dull… The key problem – the tune. The K20 engine is tuned to its maximum, to make every possible HP at every rpm. K24 is tuned for economy, ecology, safety and so on.
And here comes the big question. Why can’t we tune it like K20 is? To the limit! No problem 🙂 It’s done for your pleasure and excitement. And here is the explanation, for those who care about and are interested in details.
As all of you knows, these are i-VTEC engines that have small and big lobes on the camshafts, the small lobes are made for economy and the big ones are made for power. Let’s see how much power a K20 can rev. VTEC engages at 5800 and lasts till 8600, almost 3k of fun for its close ratio gearbox. Now let’s see at K24, VTEC kicks in at 6k and last to 6800rpm on AT and about 7000 rpm on MT. So much less fun and another problem is the existing gear ratios in both AT and MT, every gear you shift will kick you out of the power window (VTEC window) where the small lobes made for the economy are operating.
And one more problem here. Engine consumes air to burn fuel, there is a moment when the small lobes on the camshaft can’t open valve deep enough to supply enough air for power grow, and torque + power starts to fall and recovers only in the VTEC zone, where the big lobes are engaging, but it’s too late, you have reached the red line limitation. So instead of a constant power building through the revs we have a big dip in the middle with a just small bump of power but for a very short duration at the top… They should have made that switch to VTEC window, much earlier to supply enough air. I don’t know and don’t understand all the reasons why Honda screwed the tune of Accords so bad but we have what we have.
They screwed almost everything there. VTC, this tech isn’t fully used in stock calibration, the very small angle of advance is used. Ignition – very conservative, fuel maps – too rich, VTEC – too late.
One more thing to talk about – power management. It’s the pedal under your foot that opens the throttle plate. The cable is gone, say hello to Drive By Wire. How it works: you have 2 resistors , one in the pedal module and one in a throttle body. ECU sees that you pushed the pedal so you need to accelerate and send the command to the TB to open for a certain amount. What is the problem? Why is DBW pedal so sluggish and stupid? Because of the compensation table in the DBW map. You are pushing the pedal for 30% but the ECU opens the plate for 20% . You are angry with bad engine respond and you are starting to push it even more but the ECU cut some of your will again and again. You cant be a solid thing with your car because of this. The solution… just set that map 1:1 like a cable 🙂 So when you push 10% then you have about real 10 %. 40% is 40% and you don’t need to jump on your pedal with 2 legs anymore, you will get the right amount of acceleration you want.
So in short here are the key differences between our tuned ECU program vs the stock tune:
1. DBW map, instant respond on a pedal movement, much more predictable amount of power and acceleration, lots of pleasure knowing that you own this mechanism, not a vice versa 🙂
2. Ignition. Not too much to say, tuned to the detonation limit ( minus 1-2 degree for safety ) for good RON95 gasoline
3. VTC has been tuned for the best performance across the range.
4. Fuel tables have been precisely tuned for max power at the top end and real economy at the low end, fuel efficiency under normal driving is better for about 0.6 – 0.8 litres, depends on the air filter and catalysator conditions.
5 VTEC has been set to the point where the small lobes on the camshaft can’t open the valve enough for more air and VTEC high lobes must start to work, it is at 4600 rpms. So now you don’t have a dip in power/torque, the power climbs smoothly to the rev limiter.
6. Rev limiter has been moved to 7700 rpms. There is a moment when the VTEC big lobes are not able to supply more air for building more power, this point is 7600 rpms. Stock oil pump also has this 7500-7600 rpm productivity limit. So its efficient to rev the engine to those rpms and then shift the gear. And now your new power window is much higher 4600 rpm – 7600 rpm – 3000 rpm of fan!
So … what we have after all? Well, we have a true and sharp Honda engine which now responds like a Type-R engine does but more powerful and much more torquey!
And here is in short how this long theory looks and works on the road, in real life :
Video feedback from Russian customers