Any actual dyno test comparisons between headers?
- Thread starter forcefed86
- Start date
They do.
But you have to have the mods to support them.
That is a big part of engine tuning. I run a 3 stage straight pipe on an alcohol dragbike and it works great.
Also seen some big gas engine performance from the bugle type believe it or not.
Saying one design works better than the other kinda depends on a lot of factors.
The theory of staged headers as I understand it is to try and evacuate more exhaust gasses from the cylinder by increasing the ID of the tubing at certain intervals.
If you have a cam with some overlap, this will work in concert with the staged pipe to even better scavenge the exhaust gasses out and more fuel and air in.
To be honest to really find out what works best, you might need to bench flow the head with different pipes and see which type works best. Or see what people with a similar setup are running, and use that as a starting point.
But you have to have the mods to support them.
That is a big part of engine tuning. I run a 3 stage straight pipe on an alcohol dragbike and it works great.
Also seen some big gas engine performance from the bugle type believe it or not.
Saying one design works better than the other kinda depends on a lot of factors.
The theory of staged headers as I understand it is to try and evacuate more exhaust gasses from the cylinder by increasing the ID of the tubing at certain intervals.
If you have a cam with some overlap, this will work in concert with the staged pipe to even better scavenge the exhaust gasses out and more fuel and air in.
To be honest to really find out what works best, you might need to bench flow the head with different pipes and see which type works best. Or see what people with a similar setup are running, and use that as a starting point.
I get the performance bug and tend to buy bandwagon go fast goodies. Trying not to do that. And while I do believe you completely and that does make perfect sense… I'm wondering what kind of performance we are talking about on average for the average back yard “racer”.
Feel like a lot of folks "seat of the pants" power meter's tend to be incorrect. (mine included) I swore my bike felt faster with no muffler. Yet back to back runs with a stop watch show little to no gain. While Im sure a properly tuned pipe with cam events and 100% spot on tuning would indeed perform better... that’s not realistic for most of us. We aren’t using Wb02 sensors... flow benches etc. For the average schmo out there racing his pals... I'm super curious if a pipe of any reasonable length/diameter performs as well as another. The “leader” in our group uses a factory muffler box that is gutted with 1.125” pipe leading to it. While I don’t doubt an aftermarket race pipe may perform slightly better is bolting one on for .002 HP really worth the cost vs performance? Perhaps it is! Maybe he’d get much more power. Just curious if any actual dyno data has been collected on a typical predator swapping out headers back to back.
Thank you!
Feel like a lot of folks "seat of the pants" power meter's tend to be incorrect. (mine included) I swore my bike felt faster with no muffler. Yet back to back runs with a stop watch show little to no gain. While Im sure a properly tuned pipe with cam events and 100% spot on tuning would indeed perform better... that’s not realistic for most of us. We aren’t using Wb02 sensors... flow benches etc. For the average schmo out there racing his pals... I'm super curious if a pipe of any reasonable length/diameter performs as well as another. The “leader” in our group uses a factory muffler box that is gutted with 1.125” pipe leading to it. While I don’t doubt an aftermarket race pipe may perform slightly better is bolting one on for .002 HP really worth the cost vs performance? Perhaps it is! Maybe he’d get much more power. Just curious if any actual dyno data has been collected on a typical predator swapping out headers back to back.
Thank you!
Sorry i didn’t know you meant for average engine.
you asked if the pipe makes a difference, and it does. If you have the mods to support it like i said.
My 3-stage header is on an all out race engine so it makes a difference. It’s a dragbike and has been timed hundreds of times. So no butt-o-meter lol it has been on a chassis dyno as well
for a regular build, i’m not 100% sure on that.
i have 2 identical mostly stock engines 1 with straight pipe and 1 with staged pipe. Can’t really tell the difference except for the sound.
you asked if the pipe makes a difference, and it does. If you have the mods to support it like i said.
My 3-stage header is on an all out race engine so it makes a difference. It’s a dragbike and has been timed hundreds of times. So no butt-o-meter lol it has been on a chassis dyno as well
for a regular build, i’m not 100% sure on that.
i have 2 identical mostly stock engines 1 with straight pipe and 1 with staged pipe. Can’t really tell the difference except for the sound.
From Hot Rod on how they work:
A tuned length primary exhaust header pipe creates a rarefaction (negative low-pressure wave) that’s reflected back up the pipe. On a standard header the negative wave occurs at the primary tube’s open or collector-end due to sudden gas expansion into the larger collector and consequent velocity decrease. With the proper tuned-length for the combo, the wave arrives back at the exhaust valve during the valve overlap period when both the intake and exhaust valves are open, in theory completely scavenging the cylinder of residual gasses.
Incrementally increasing primary tube diameter before the collector—aka a “stepped header” design—creates additional rarefactions. The steps’ location on the pipe and the amount of increase between each step can be used to tune the strength of the various reflected waves. The greater the step-up amount, the stronger the negative pulse. On the other hand, too many or too much step-up weakens the “primary” rarefaction of the main wave at the collector. A typical stepped header has one or two steps ahead of the collector, and each step is progressively ⅛-inch larger.
Stepped primary tubes can be used to create multiple peaks in the power and torque curves and to dial-in at what rpm they occur. One step may be adjusted to enhance the torque peak, and the second for peak power. On the other hand, multiple rarefactions may trade-off peak power in favor of more area under the curve. Stepped headers tend to be very finicky, and to actually see gains over a conventional primary tube requires closely coordinating the steps with the camshaft and induction system. In fact, a tuned induction system with controlled plenum volume and runner lengths acts very much like a header, but on the induction side, giving the tuner yet another tool for careful crafting of the power and torque curves.
A tuned length primary exhaust header pipe creates a rarefaction (negative low-pressure wave) that’s reflected back up the pipe. On a standard header the negative wave occurs at the primary tube’s open or collector-end due to sudden gas expansion into the larger collector and consequent velocity decrease. With the proper tuned-length for the combo, the wave arrives back at the exhaust valve during the valve overlap period when both the intake and exhaust valves are open, in theory completely scavenging the cylinder of residual gasses.
Incrementally increasing primary tube diameter before the collector—aka a “stepped header” design—creates additional rarefactions. The steps’ location on the pipe and the amount of increase between each step can be used to tune the strength of the various reflected waves. The greater the step-up amount, the stronger the negative pulse. On the other hand, too many or too much step-up weakens the “primary” rarefaction of the main wave at the collector. A typical stepped header has one or two steps ahead of the collector, and each step is progressively ⅛-inch larger.
Stepped primary tubes can be used to create multiple peaks in the power and torque curves and to dial-in at what rpm they occur. One step may be adjusted to enhance the torque peak, and the second for peak power. On the other hand, multiple rarefactions may trade-off peak power in favor of more area under the curve. Stepped headers tend to be very finicky, and to actually see gains over a conventional primary tube requires closely coordinating the steps with the camshaft and induction system. In fact, a tuned induction system with controlled plenum volume and runner lengths acts very much like a header, but on the induction side, giving the tuner yet another tool for careful crafting of the power and torque curves.
Appreciate the input as always. I'll bring a couple with me... maybe swap with some guys while I'm there and see if we feel or see a difference. Assuming in general we'd want a longish pipe. Running a 22mm carb 160 headed 212 (non hemi) with a mod2 cam at the moment. very mild build.
With or without this 125cc muffler bolted on tended to make no difference (I did not adjust the tune however) The plug isn't black... that's about all I have to go on. The sound difference is massive though.
I haven't tried this setup with the new clutch. was running a converter prior.
With or without this 125cc muffler bolted on tended to make no difference (I did not adjust the tune however) The plug isn't black... that's about all I have to go on. The sound difference is massive though.
I haven't tried this setup with the new clutch. was running a converter prior.
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Do you know the cam specs on the Mod2?
Is there any overlap?
If so, on a mild build the overlap will still help even without a staged pipe. A staged pipe may be overkill for that type of build.
To me a staged pipe is trying to squeeze every bit of performance from a known and tested combination of parts.
I would def try as many pipes as you can, that’s a great idea to try different ones.
Is there any overlap?
If so, on a mild build the overlap will still help even without a staged pipe. A staged pipe may be overkill for that type of build.
To me a staged pipe is trying to squeeze every bit of performance from a known and tested combination of parts.
I would def try as many pipes as you can, that’s a great idea to try different ones.
Cams specs attached. Def. has some overlap. I have 1.3 rockers on the way as well.
The typical "off the shelf" pipes all appear to be 7/8" ID. How can this be ideal? The flanges claim 1.08" ID and even those seem to shroud the port? By the time you slip a heavy wall thickness pipe in them it seems like you would be making a bottle neck. I ground my "shelf pipe" flange out and attempted to "port match" the flange to the gasket... still seems less than ideal.
I have some 1.25" pipe laying around. I was going to attempt to make my own and at least not cover up the port. Wasn't sure on the length or if I should flare/trumpet the end a bit? Or if thats worthless?
The typical "off the shelf" pipes all appear to be 7/8" ID. How can this be ideal? The flanges claim 1.08" ID and even those seem to shroud the port? By the time you slip a heavy wall thickness pipe in them it seems like you would be making a bottle neck. I ground my "shelf pipe" flange out and attempted to "port match" the flange to the gasket... still seems less than ideal.
I have some 1.25" pipe laying around. I was going to attempt to make my own and at least not cover up the port. Wasn't sure on the length or if I should flare/trumpet the end a bit? Or if thats worthless?
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Yup stock. Believe they are 24mm.
Assuming we target PK RPM? Was hoping for around 6500-7k. The old converter would really struggle to go much over 6100ish. (never understood this) was running stock carb. I'll need to see where the new clutch and carb pull to. Looks like about 2+ feet tho. Unless we want to target PK TQ? Can't imagine having a 40"+ pipe, lol.
Assuming we target PK RPM? Was hoping for around 6500-7k. The old converter would really struggle to go much over 6100ish. (never understood this) was running stock carb. I'll need to see where the new clutch and carb pull to. Looks like about 2+ feet tho. Unless we want to target PK TQ? Can't imagine having a 40"+ pipe, lol.
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one thing you need to understand very well is your engine. you had mentioned in another thread about this same engine you are running that you purchase a 22mm carb from go powersports and they told you it was ready to go. no way in hell that they can sell a carb ready tune to your engine.maybe get it in the pall bark,but that's it. this something you need to figure out. also mentioned type of flywheel you had with only 28 degrees advance. thats not good either. nothing mentioned about the type of head work you have done? that too will have a big effect. and yes changing your rockers to a 1.3 will change things has long as you have all the correct parts that go with it and other mod's done to it. I would try to concentrate on that and then maybe having a 3 stage header would affect how well the engine works. but right now how your engine is ,it wouldn't know the difference between a straight pipe or a tune pipe.
I get there’s no way they can have it dialed it to my setup. Though U do give them a description of the parts installed when you order. I will say it fired and idled great. That’s all I know at this point, it’s been snowing. I forgot… When I pulled it apart this last time I threw a 4* key in there as well. Should be at 32* now.
No real head work. Was a $30 shipped gx160 clone head. Smoothed out the casting and took out some rough edges narrowed down the valve guide area a tad and called it good. Basically did nothing. Did not alter port size or shape.
The 1/3 rockers come with a new guide plate. Was told this was a relatively low lift cam so a 1.3 rocker would help slightly… no reason not to run one. Those should arrive soon but are not installed.
What is the best way to go about tuning tho? Aside from taking a guess a the plug… aren’t the majority of us guessing at A/F ratios? Going by “seat of pants” feel? I have a portable Wb02 setup I use on my race cars… but the sensor is larger than the pipe, lol. Couldn’t exactly clamp it in there. Would need to make some kind of funky large diameter adapter expansion tank thing to get in mounted. Then when I changed back to a “standard” pipe the fuel demands would change I’d guess? Guess I’m basically asking how to tune it… though I get that’s an open ended question.
