Shearer or sniper pipes

[mailman]

Thanks Chris,

 

I would have thought the atv dyno would read higher, what is puzzling is that both dynoes come on the pipe at the very same rpm but peak at different rpm's. All of the dyno runs I have with your pipe peak at 9900 to 10200 and take no more than 3.5 seconds. Very interesting.

 

I think there are two really good questions here.

The first is asking which dyno will show more power and why.

The second question is: "Why the shift in rpm at peak power on the car dyno even though the curves start at the same rpm on both dynoes.

 

I will try to answer the second question first since it is a little easier. I will answer the first question in a separate post.

 

Short version: heavy rollers = longer run times = higher pipe temp = shorter pipe characteristics = higher peak rpm

 

Long version:

The rollers are much heavier on the car dyno so it naturally takes longer to accelerate them vs. the lighter atv dyno. Think of yourself on a bicycle with gears. Starting from a dead stop in low gear, pedal as fast as you can. You will accelerate the bike to max speed in that gear in a few seconds then won't go any faster due to your physical limitations. Now repeat the same experiment except put the bicycle in the highest gear. It will naturally take you longer to reach a max. speed. The load on your body is greater in the higher gear and therefore takes longer to overcome it. A better example is if you put the bike in any gear and record how long it takes you to reach max speed. Then repeat the exercise except put on packs that double or triple your weight then repeat the exercise. It will take longer in the same gear to reach max speed due to all the weight you have to accelerate.

OK, so you accept the fact that the car dyno pulls will take longer since the rollers are heavier. Why does the peak rpm shift then?

The longer the run time on the dyno, the more heat gets put into the exhaust. As the exhaust gets hotter, the pipe starts to act shorter. A shorter pipe will push peak rpm higher. For the technical people, the waves in the pipe move faster when the pipe gets hotter. This speeds up the flow of the return pulse which means peak efficiency or peak torque is now at a higher rpm.

If you are jetted correctly, and make 3 back to back passes on a dyno, then you will usually see the curve shift to the right due to the heat and pipe starting to act shorter.

Pipe performance changes with heat.

[BB3]

The Shearers ended up making about 10 hp more than the Snipers with this motor and on this dyno. The Snipers made about 100 HP and the Shearers about 110 HP.

 

 

 

Ok...mailman sorry...ur probally not done....but i thought Snipers where gonna make 10more HP then shears....but it seems to be the other way around?

 

Isnt that what all this BS was about in the first place the snipers could be bolted on any Motor and make 10 more Hp then any shears....oof's or inframes??

 

Plz dont kill me ....im just asking.

[WINDYCITYJOHN400]

Your seeing the info

Your reading the info

Your understanding the info

 

It's just kind of hard to let it all soak in isn't it.

 

I'm looking forward to the Sniper/Passion response. I sure hope they don't try to throw Chris under the bus because he tried everything.

Edited July 26, 2012 by WINDYCITYJOHN400

[PassionRE]

I'm confused.....I was looking at your post in the dyno section showing your 465 on gas making 113HP and 62 ft. pounds of torque.

Now looking at this big 554 DM motor I see 113 and only 59 ft. pounds as a best.

Now I know Chris is the king of dyno testing. (He's got quite a few runs over the years.... there are well over 350 at this point.) I think he's made more runs on the dyno per year than runs on the hill.

He dyno'd the snot out of that bike to try to find power in that combo. As you can see he's willing to double check his info on multiple dyno's to verify results. He's so into the testing and tuning that he's dynoing dynos against each other to see how weight differences effect results.

 

But I also know he tests in the real world too. So he has radar runs at the hill to confirm the whole dyno vs. real world results too. (As I recall his hill speeds were very close between the 492 and the 554)

 

I have my own theory as to why the heavier car dyno runs differ from the ATV dyno pulls. I also have some thoughts on why your dyno testing runs ramp up so fast. But I'd sure like to hear your thoughts on these results because he tested his 492 on the same dyno as the 554......so the HP numbers are apples and apples.

Not sure who this first question was for but I can answer it.

The 465cc engine making 113 and 62 was developed well after this build and was a balanced set-up. The 554cc DM was extremely under carbed making intake velocity so high that it literally choked itself out on the big end. Basicly the engine had the ability to process much more air, it just couldn't overcome the choke point in the venturi. Jim

[WINDYCITYJOHN400]

 

 

The 554cc DM was extremely under carbed making intake velocity so high that it literally choked itself out on the big end. Basicly the engine had the ability to process much more air, it just couldn't overcome the choke point in the venturi. Jim

 

Why was the motor able to breath better up the entire curve with the Shearer pipes on it? The motor clearly was making more power even before you get to a perceived max carb flow point. Why aren't the Sniper runs above the Shearer runs at ANY point in the curve?

[lms1977]

Why was the motor able to breath better up the entire curve with the Shearer pipes on it? The motor clearly was making more power even before you get to a perceived max carb flow point. Why aren't the Sniper runs above the Shearer runs at ANY point in the curve?

 

good question

 

does passion and or sniper have a dyno to test there motor setups out?? the only reason I ask is if a builder sets you up with a set up like the 4mil DM you obviously have a shit ton of money in it and he should have proof as to what it will make, and what carbs pipes domes etc. you need to use

 

I'm not trying to be a smart ass but if I put that much money out I would want a honest answer as to what it would make, and what parts to use..

 

I dont think mailman had 34pj's on that motor either so the carb thing seems kinda weak

[Phelps]

good thing about all this is mat's nuts got a break from all the weight for a minute

[locogato11283]

Can no one answer my question?

 

Did Mat design the original small bore Shearers?

[wacko2000]

Can no one answer my question?

 

Did Mat design the original small bore Shearers?

I believe the answer is NO bob- but of course I could be wrong

[J-Madd]

I think there are two really good questions here.

The first is asking which dyno will show more power and why.

The second question is: "Why the shift in rpm at peak power on the car dyno even though the curves start at the same rpm on both dynoes.

 

I will try to answer the second question first since it is a little easier. I will answer the first question in a separate post.

 

Short version: heavy rollers = longer run times = higher pipe temp = shorter pipe characteristics = higher peak rpm

 

Long version:

The rollers are much heavier on the car dyno so it naturally takes longer to accelerate them vs. the lighter atv dyno. Think of yourself on a bicycle with gears. Starting from a dead stop in low gear, pedal as fast as you can. You will accelerate the bike to max speed in that gear in a few seconds then won't go any faster due to your physical limitations. Now repeat the same experiment except put the bicycle in the highest gear. It will naturally take you longer to reach a max. speed. The load on your body is greater in the higher gear and therefore takes longer to overcome it. A better example is if you put the bike in any gear and record how long it takes you to reach max speed. Then repeat the exercise except put on packs that double or triple your weight then repeat the exercise. It will take longer in the same gear to reach max speed due to all the weight you have to accelerate.

OK, so you accept the fact that the car dyno pulls will take longer since the rollers are heavier. Why does the peak rpm shift then?

The longer the run time on the dyno, the more heat gets put into the exhaust. As the exhaust gets hotter, the pipe starts to act shorter. A shorter pipe will push peak rpm higher. For the technical people, the waves in the pipe move faster when the pipe gets hotter. This speeds up the flow of the return pulse which means peak efficiency or peak torque is now at a higher rpm.

If you are jetted correctly, and make 3 back to back passes on a dyno, then you will usually see the curve shift to the right due to the heat and pipe starting to act shorter.

Pipe performance changes with heat.

 

It has been my experience that when its jetted correctly (for the dyno) that the curves should overlay on back to back pulls. If its rich, it will shift right, if its lean, it will shift left.

[lms1977]

Can no one answer my question?

 

Did Mat design the original small bore Shearers?

 

I have no idea if he did or not but I'm sure there not the original version he sells now ..!! and what the hell does that matter if I could ask?? are you the guy that designed concrete I mean come on

[mailman]

The next graph will show the Snipers on the car dyno vs. a set of OOF silenced Shearer big bore pipes with the head pipe cut down 1/2 inch to an inch. I forget the exact amount. The carbs used for all these dyno runs were 38 pwk's on gas. The Shearers are red and the Snipers are blue. You can see the Shearer pipes are stronger through the entire curve until 9500 rpm. From 9500 rpm on up, the Snipers are stronger.

It is important to note that this comparison was not done back to back on the same day. The Sniper run posted here is "the best run" from 3/16/11 and the Shearer best run was on 5/27/11.

 

[guns4children]

Shit just got real

[dajogejr]

It is important to note that this comparison was not done back to back on the same day. The Sniper run posted here is "the best run" from 3/16/11 and the Shearer best run was on 5/27/11.

 

 

 

Mailman, while I appreciate sharing the info, truly...I do. How can anyone have any faith in these numbers and runs when they're done over 2 months apart?

It is interesting to see the similar power curves...but anyone can tell you that many days apart is not a good comparison of the two.

[mailman]

It has been my experience that when its jetted correctly (for the dyno) that the curves should overlay on back to back pulls. If its rich, it will shift right, if its lean, it will shift left.

 

I think you are mistaken. Keep in mind that this is all based on gas and not methanol. The longer you run a motor on the dyno, the hotter it will get which will push the curve to the right and read max rpm higher. Now tuning for max power on an atv dyno vs a car dyno is different and this may be where the disagreement lies. If you tune to max power on an atv dyno, then go to the hill, most likely you will burn up your motor from being too lean. Most atv dyno owners will richen up the main at least 2 to 3 sizes before they send a customer out the door because they know this. On a car dyno, the load is greater so it is possible to jet for max power on the dyno then go run the hill with the same jetting or maybe 1 size richer due to altitude and temps. Phx is about 1100 ft and Glamis is 0-500 ft.

 

Here is a back to back comparison of the Snipers on the car dyno. You can see the curve shift right due to the increased heat. This is the same setup I ran the hill with.

You can see this same thing happening on the atv dyno in my first graph that I posted.