M8 Dyno Numbers
#501
IMHO your a ways off base with your statements. Look at other dyno charts and you will see most of them start the dyno pulls north of 2100 rpm, now why is that? Typically they are hiding what happens at lower RPM's as the dip as you call it shows up as it does in the chart I posted. For reference let's look at the 131 posted just before it and look at what it makes at 1700 - 2100 RPM.......... sorry but you cannot do it, as the runs starts later in the RPM range. So it's important to compare numbers, not pictures. Now could it of had a better pipe, possibly, but this is what the customer had on his bike and since I was only there to aid one of our dealers this was the results. The bike itself hauls *** and you cannot feel the dip as you call it at all. Another thing is the engine temperature runs are made at and how consistent the bike runs from one run to another and as anyone can see it lays one run right with the others as the engine temperatures rise.
The idea that you should compare numbers and not pictures is simply wrong. The reason you're showing a chart is to show how it performs across the rev range. Numbers are very dependent on conditions and test equipment. Higher barometric pressure, lower air temperature, lower humidity will yield better numbers. STD rather than SAE correction will yield better numbers (at higher barometric pressure). A dyno can be calibrated to produce better numbers. The curve, however, shows how well the engine performs in low and high rpm. This bike performs poorly in the rpms where you ride, and only picks up in the high rpms. That's not down to the tune, but to the lack of back pressure from the exhaust. I haven't looked the Supertrapp up, but my guess it's a shorty, or it has a stepped or conical muffler.
If you tune a bike and that's the result, you should be advising the customer how he can improve the low end performance. If that chart is from a Softail with exhausts that don't go past the rear axle, this would be the expected curve, but a touring bike should produce better low end numbers with the right exhaust.
#502
Originally Posted by Bloody Marvelous;[url=tel:20016728
20016728[/url]]That torque dip at 2600 RPM is horrendous. A clear example of putting the wrong pipes on the bike.
Originally Posted by Bloody Marvelous;[url=tel:20017454
20017454[/url]]. If that chart is from a Softail with exhausts that don't go past the rear axle, this would be the expected curve
The following users liked this post:
road114 (07-02-2021)
#503
No offense, but there's quite a difference between starting your pull above 2100 rpm with the curve climbing immediately, and starting it at 1800 rpm and the curve not climbing until after 3000 rpm.
The idea that you should compare numbers and not pictures is simply wrong. The reason you're showing a chart is to show how it performs across the rev range. Numbers are very dependent on conditions and test equipment. Higher barometric pressure, lower air temperature, lower humidity will yield better numbers. STD rather than SAE correction will yield better numbers (at higher barometric pressure). A dyno can be calibrated to produce better numbers. The curve, however, shows how well the engine performs in low and high rpm. This bike performs poorly in the rpms where you ride, and only picks up in the high rpms. That's not down to the tune, but to the lack of back pressure from the exhaust. I haven't looked the Supertrapp up, but my guess it's a shorty, or it has a stepped or conical muffler.
If you tune a bike and that's the result, you should be advising the customer how he can improve the low end performance. If that chart is from a Softail with exhausts that don't go past the rear axle, this would be the expected curve, but a touring bike should produce better low end numbers with the right exhaust.
The idea that you should compare numbers and not pictures is simply wrong. The reason you're showing a chart is to show how it performs across the rev range. Numbers are very dependent on conditions and test equipment. Higher barometric pressure, lower air temperature, lower humidity will yield better numbers. STD rather than SAE correction will yield better numbers (at higher barometric pressure). A dyno can be calibrated to produce better numbers. The curve, however, shows how well the engine performs in low and high rpm. This bike performs poorly in the rpms where you ride, and only picks up in the high rpms. That's not down to the tune, but to the lack of back pressure from the exhaust. I haven't looked the Supertrapp up, but my guess it's a shorty, or it has a stepped or conical muffler.
If you tune a bike and that's the result, you should be advising the customer how he can improve the low end performance. If that chart is from a Softail with exhausts that don't go past the rear axle, this would be the expected curve, but a touring bike should produce better low end numbers with the right exhaust.
Why is it, the 6+ ft lb dip in the dyno chart posted just prior to my posted chart didn't get you all up in arms? It must need a different pipe as well by your logic!
The following users liked this post:
MTBIG G (06-26-2021)
#504
It's not a 10 ft-lb dip. It's a 20-30 ft-lb dip over a range of 2000 to 3000 rpm. That's not a little dip in the curve like the 6 ft-lb over a range of 4100 to 4400 rpm, that's a huge drop in performance over the majority of the range where you ride the most.
I'm not saying not to tune it. Obviously you tune it. But you go over the results with your customer (or in this case the dealer should, I didn't know you were tuning for a dealer when I made my comment), explain why the torque curve is so much lower over that rev range, what that rev range represents, and what options the customer has to improve it.
If the customer's happy with the results, awesome. If he wants to improve it, now he knows how. Just saying "it is what it is", and leave it at that, is a disservice to the customer. He put a lot of money in building a high performance bike, and the cost of improving the low end performance is likely relatively low in comparison. A couple of hundred bucks investment can see major gains in that range.
I'm not saying not to tune it. Obviously you tune it. But you go over the results with your customer (or in this case the dealer should, I didn't know you were tuning for a dealer when I made my comment), explain why the torque curve is so much lower over that rev range, what that rev range represents, and what options the customer has to improve it.
If the customer's happy with the results, awesome. If he wants to improve it, now he knows how. Just saying "it is what it is", and leave it at that, is a disservice to the customer. He put a lot of money in building a high performance bike, and the cost of improving the low end performance is likely relatively low in comparison. A couple of hundred bucks investment can see major gains in that range.
#505
It's not a 10 ft-lb dip. It's a 20-30 ft-lb dip over a range of 2000 to 3000 rpm. That's not a little dip in the curve like the 6 ft-lb over a range of 4100 to 4400 rpm, that's a huge drop in performance over the majority of the range where you ride the most.
I'm not saying not to tune it. Obviously you tune it. But you go over the results with your customer (or in this case the dealer should, I didn't know you were tuning for a dealer when I made my comment), explain why the torque curve is so much lower over that rev range, what that rev range represents, and what options the customer has to improve it.
If the customer's happy with the results, awesome. If he wants to improve it, now he knows how. Just saying "it is what it is", and leave it at that, is a disservice to the customer. He put a lot of money in building a high performance bike, and the cost of improving the low end performance is likely relatively low in comparison. A couple of hundred bucks investment can see major gains in that range.
I'm not saying not to tune it. Obviously you tune it. But you go over the results with your customer (or in this case the dealer should, I didn't know you were tuning for a dealer when I made my comment), explain why the torque curve is so much lower over that rev range, what that rev range represents, and what options the customer has to improve it.
If the customer's happy with the results, awesome. If he wants to improve it, now he knows how. Just saying "it is what it is", and leave it at that, is a disservice to the customer. He put a lot of money in building a high performance bike, and the cost of improving the low end performance is likely relatively low in comparison. A couple of hundred bucks investment can see major gains in that range.
So where are you come up with 20 -30 ft lbs is a complete mystery ? This is a prime example of not know anything about a dyno and looking at the picture only, which is just why I've said you have to compare the numbers at any given test point!
#506
The following 2 users liked this post by Quik:
Mofo67 (06-27-2021),
William Ferril (01-10-2022)
#507
I think there are a few things being overlooked. Being that the dealer was having it tuned, there is the actual setup of the pipe for one. Did the dealer ask to have the pipe tuned as well. Doc tuned my 12 RGU, with a Supertrapp, it took a few hours of time to get the pipe where he wanted it after the initial tune, did the dealer want the extra charges or tune it as it sits. End caps, # of disks all play a roll as we all know. The cam maybe part of the equation with it’s low end performance, and of course looking at where the runs start at is rarely seen on most dyno runs. To me the closeness of all 3 runs says the tune is spot on for what was asked. Just my opinion…..
#508
#509
I think there are a few things being overlooked. Being that the dealer was having it tuned, there is the actual setup of the pipe for one. Did the dealer ask to have the pipe tuned as well. Doc tuned my 12 RGU, with a Supertrapp, it took a few hours of time to get the pipe where he wanted it after the initial tune, did the dealer want the extra charges or tune it as it sits. End caps, # of disks all play a roll as we all know. The cam maybe part of the equation with it’s low end performance, and of course looking at where the runs start at is rarely seen on most dyno runs. To me the closeness of all 3 runs says the tune is spot on for what was asked. Just my opinion…..
The following 3 users liked this post by Steve Cole:
#510