johnnc
New Member
My bike is NC750X
Does the Leo Vince decat de-cataylser improve performance in any significant way? In one word, NO. Not from my figures. I know that some people might have "found" a performance increase and I know from experience when I bought a product there can be a placebo effect that it goes faster or feels smoother etc so that is why I decided that I would measure the performance before and after I put this decat pipe on. Only by measuring can you get a true answer, at least for my bike.
The pipe goes on easily and quickly and seems good quality. It maybe has slightly more throaty sound. I did not like that it slightly changed the position of the O2 sensor. On standard pipe it is shielded behind plastic "belly pan" but on the Leo Vince pipe it is turned around a little and more exposed to the muck that's going to come off the front wheel.
Here are the figures I measured and I'll explain the method but first the figures.
I did 12 runs with each pipe. 6 in each direction on exactly same piece of road with standard Honda downpipe and 6 in each direction (exactly same piece of road) with LeoVince decat downpipe.
Speedo set to kph and full throttle acceleration in 3rd gear from 40kph (about 25mph) to 125kph (about 78mph) when rev limiter hits in on my bike.
With standard pipe average time for the runs was 6.61 sec. With Leo Vince average time (corrected for temperature) 6.63 sec. So it is slightly slower though this difference is tiny and would not be noticeable to the rider. Leo Vince pipe is 1.2kg lighter and losing 1.2kg would improve times by about 0.03 sec.
So for the power to be the same with 1.2kg less weight it should be 0.03sec faster on time, not 0.02 sec slower. From full tank of petrol to almost empty would make 0.22 sec difference.
(Uncorrected it was 6.51 sec) Why do we need to correct for temperature? Although I tried to pick similar days with no wind, the second day was 5C colder which means more power for your engine.
How is that calculated? We are doing this ball park calculations but for this situation it is quite accurate as the differences are slight so other factors don't play such a big part. Temp was 8C first day and 3C with Leo Vince. That is 281 deg absolute and 276 deg absolute. Air is slightly more dense when 5C colder so there will be more power from engine, about 1.8% more.
I connected a high temperature probe directly below the exhaust port on the inside bend of downpipe in as simlar position as possible with standard and Leo Vince. With Leo Vince temp seemed to be higher all the time and max reading when bike was flat out in top was 560C compared to 520C for standard downpipe. This differentce may well have just been where I put the probe. I tried to get it exactly the same. If it does indicate an increase in temp then I would not like that.
I kept as much as possible the same. I wore the same leather one piece suit. Tyre pressures the same. Each time I filled the bike with petrol and took the same route travelling about 20 miles there and back on motorway to get engine up to temp then went to the road to do the tests. Though I had lost some weight from the first run of about 1 or 2 kg as I had increased my training.
How did I time the runs?
Firstly I did many days finding the right piece of safe road in the countryside with no houses and little traffic.
Beforehand over a few days I did many, many practice runs in different gears to see what was best way to do it. For me it was 3rd gear. I just roll along at about 38kph then fully open the throttle and accelerate until it hits limiter at about 126kph. There is no point in starting from standing start or changing gears as there are too many variables like letting the clutch out or when you change gear. I sat up straight as normal.
With a full throttle roll-on you are getting the proper performance difference all the way through the rev range.
In a way this is a true dynometer and it's telling you what is really happening.
If you had an airfield or private motorway then top gear would expand the differences but on an open road there is always some car in your way (if you are trying to go flat out in top you'll need to be on motorway) and slight changes in incline or wind direction will have more effect.
If you have steep long hill this is also good but there can be a lot of variables here too.
I used a camera pointing at the speedo. Speedo was set in kph but mph might actually be better, but started in kph and just kept with that. Each run is recorded on video then I play them on the computer in "Movie Maker". You go back and forward one frame at a time until you see the run starting at 40kph. You write down start time that is shown in Movie Maker. Then I moved on each 10kph stopped the video then back and forth frame by frame to get the right time for that 10kph increase. Write down each time from 40kph until 125kph. You then take the starting time from the final time to get your total run time. 40-125. On the first 12 runs, 7 runs came in at 6.61 seconds. I actually could not believe it was so consistent but I checked all the raw figures and it was correct. Movie Maker shows 0.01 of a second but it is 30 frames per second so the frame differences are either 0.03 and 0.04 seconds. But that is more than accurate enough for this purpose.
We make a few assumptions, that won't be 100% correct if you want to use the calculations to fly to the moon, but in this case it will be accurate enough as there was little difference in any of the times.
I took the weight of the bike and me at 300kg in total. Which would be close enough. So if you take off the 1.2kg for the lighter pipe that should be 1/250th (0.4%) improvement in the time and acceleration. 10kg decrease in weight like the difference from full fuel to very little will give 1/30th (3.3%) improvement in acceleration or 0.22 seconds on this run. Thinking only about accelerating the weight of bike and rider. There is also rolling resistance and air resistance but as we are putting the bike through the same speeds these are similar in all the runs,
There is the air temperature and air pressure and humidity. (Air pressure and humidity were similar) Temp was 281 deg absolute first day and 276 deg absolute with Leo Vince. These figures meant the air was 1.8% more dense with Leo Vince so there will be more power from engine (because the air is cooler not because of the pipe) which is about 1.8% more or around about this.
In any case the results from both pipes are so similar that if you had a big meal beforehand then it might make more difference.
Certainly I saw no reason to keep this pipe on my bike so I took it off. If it had given a little improvement in performance then maybe I might have kept it on bike but the increased exhaust temp and more exposed O2 sensor would be more than enough reason for me to take it off.
Why no performance increase when there is a "power sapping" catalyst inches from the exhaust port? Don't know, except maybe on this bike the catalyst is not power sapping. The catalyst has about five time the cross-section area of the exhaust pipe going into and out of it. The catalyst can probably flow all the gas that exhaust pipe can throw at it. It's also very possible that the catalyst shape and close position to exhaust port is designed to help scavenge the engine's spent gases. Maybe this engine is not suitable for easy tuning and when you look at few things then this is probably correct. A low revving engine with a single throttle body and single exit "exhaust port". Removing "restrictions" like the catalyst and standard silencer and air filter probably won't make this single inlet and single "exhaust port" flow more gas to any significant extent. They are probably the biggest restriction and de-restricting elsewhere won't make much difference to the gas flow. Maybe the engineers at Honda know what they are doing.
I see that a popular fuel tuning module for the NC was withdrawn from sale while they work on trying to improve it.
I was really hoping that this pipe would give little bit of extra performance. Disappointed but I did learn a lot and it was well worth the effort.
Does the Leo Vince decat de-cataylser improve performance in any significant way? In one word, NO. Not from my figures. I know that some people might have "found" a performance increase and I know from experience when I bought a product there can be a placebo effect that it goes faster or feels smoother etc so that is why I decided that I would measure the performance before and after I put this decat pipe on. Only by measuring can you get a true answer, at least for my bike.
The pipe goes on easily and quickly and seems good quality. It maybe has slightly more throaty sound. I did not like that it slightly changed the position of the O2 sensor. On standard pipe it is shielded behind plastic "belly pan" but on the Leo Vince pipe it is turned around a little and more exposed to the muck that's going to come off the front wheel.
Here are the figures I measured and I'll explain the method but first the figures.
I did 12 runs with each pipe. 6 in each direction on exactly same piece of road with standard Honda downpipe and 6 in each direction (exactly same piece of road) with LeoVince decat downpipe.
Speedo set to kph and full throttle acceleration in 3rd gear from 40kph (about 25mph) to 125kph (about 78mph) when rev limiter hits in on my bike.
With standard pipe average time for the runs was 6.61 sec. With Leo Vince average time (corrected for temperature) 6.63 sec. So it is slightly slower though this difference is tiny and would not be noticeable to the rider. Leo Vince pipe is 1.2kg lighter and losing 1.2kg would improve times by about 0.03 sec.
So for the power to be the same with 1.2kg less weight it should be 0.03sec faster on time, not 0.02 sec slower. From full tank of petrol to almost empty would make 0.22 sec difference.
(Uncorrected it was 6.51 sec) Why do we need to correct for temperature? Although I tried to pick similar days with no wind, the second day was 5C colder which means more power for your engine.
How is that calculated? We are doing this ball park calculations but for this situation it is quite accurate as the differences are slight so other factors don't play such a big part. Temp was 8C first day and 3C with Leo Vince. That is 281 deg absolute and 276 deg absolute. Air is slightly more dense when 5C colder so there will be more power from engine, about 1.8% more.
I connected a high temperature probe directly below the exhaust port on the inside bend of downpipe in as simlar position as possible with standard and Leo Vince. With Leo Vince temp seemed to be higher all the time and max reading when bike was flat out in top was 560C compared to 520C for standard downpipe. This differentce may well have just been where I put the probe. I tried to get it exactly the same. If it does indicate an increase in temp then I would not like that.
I kept as much as possible the same. I wore the same leather one piece suit. Tyre pressures the same. Each time I filled the bike with petrol and took the same route travelling about 20 miles there and back on motorway to get engine up to temp then went to the road to do the tests. Though I had lost some weight from the first run of about 1 or 2 kg as I had increased my training.
How did I time the runs?
Firstly I did many days finding the right piece of safe road in the countryside with no houses and little traffic.
Beforehand over a few days I did many, many practice runs in different gears to see what was best way to do it. For me it was 3rd gear. I just roll along at about 38kph then fully open the throttle and accelerate until it hits limiter at about 126kph. There is no point in starting from standing start or changing gears as there are too many variables like letting the clutch out or when you change gear. I sat up straight as normal.
With a full throttle roll-on you are getting the proper performance difference all the way through the rev range.
In a way this is a true dynometer and it's telling you what is really happening.
If you had an airfield or private motorway then top gear would expand the differences but on an open road there is always some car in your way (if you are trying to go flat out in top you'll need to be on motorway) and slight changes in incline or wind direction will have more effect.
If you have steep long hill this is also good but there can be a lot of variables here too.
I used a camera pointing at the speedo. Speedo was set in kph but mph might actually be better, but started in kph and just kept with that. Each run is recorded on video then I play them on the computer in "Movie Maker". You go back and forward one frame at a time until you see the run starting at 40kph. You write down start time that is shown in Movie Maker. Then I moved on each 10kph stopped the video then back and forth frame by frame to get the right time for that 10kph increase. Write down each time from 40kph until 125kph. You then take the starting time from the final time to get your total run time. 40-125. On the first 12 runs, 7 runs came in at 6.61 seconds. I actually could not believe it was so consistent but I checked all the raw figures and it was correct. Movie Maker shows 0.01 of a second but it is 30 frames per second so the frame differences are either 0.03 and 0.04 seconds. But that is more than accurate enough for this purpose.
We make a few assumptions, that won't be 100% correct if you want to use the calculations to fly to the moon, but in this case it will be accurate enough as there was little difference in any of the times.
I took the weight of the bike and me at 300kg in total. Which would be close enough. So if you take off the 1.2kg for the lighter pipe that should be 1/250th (0.4%) improvement in the time and acceleration. 10kg decrease in weight like the difference from full fuel to very little will give 1/30th (3.3%) improvement in acceleration or 0.22 seconds on this run. Thinking only about accelerating the weight of bike and rider. There is also rolling resistance and air resistance but as we are putting the bike through the same speeds these are similar in all the runs,
There is the air temperature and air pressure and humidity. (Air pressure and humidity were similar) Temp was 281 deg absolute first day and 276 deg absolute with Leo Vince. These figures meant the air was 1.8% more dense with Leo Vince so there will be more power from engine (because the air is cooler not because of the pipe) which is about 1.8% more or around about this.
In any case the results from both pipes are so similar that if you had a big meal beforehand then it might make more difference.
Certainly I saw no reason to keep this pipe on my bike so I took it off. If it had given a little improvement in performance then maybe I might have kept it on bike but the increased exhaust temp and more exposed O2 sensor would be more than enough reason for me to take it off.
Why no performance increase when there is a "power sapping" catalyst inches from the exhaust port? Don't know, except maybe on this bike the catalyst is not power sapping. The catalyst has about five time the cross-section area of the exhaust pipe going into and out of it. The catalyst can probably flow all the gas that exhaust pipe can throw at it. It's also very possible that the catalyst shape and close position to exhaust port is designed to help scavenge the engine's spent gases. Maybe this engine is not suitable for easy tuning and when you look at few things then this is probably correct. A low revving engine with a single throttle body and single exit "exhaust port". Removing "restrictions" like the catalyst and standard silencer and air filter probably won't make this single inlet and single "exhaust port" flow more gas to any significant extent. They are probably the biggest restriction and de-restricting elsewhere won't make much difference to the gas flow. Maybe the engineers at Honda know what they are doing.
I see that a popular fuel tuning module for the NC was withdrawn from sale while they work on trying to improve it.
I was really hoping that this pipe would give little bit of extra performance. Disappointed but I did learn a lot and it was well worth the effort.
