How close is my porting to drag?

[Burt Reynolds]

Your probably going to get yourself into a mess,getting the ports to the right height is only half the problem. The transfers need to aim a certain way,some parts need to be radiused,some need knifed,theres a little trick to everything you cant just raise and lower the ports.

 

In my opinion nothing can beat the knowledge and skill of a qualified cutter

[SLORYDER]

Your probably going to get yourself into a mess,getting the ports to the right height is only half the problem. The transfers need to aim a certain way,some parts need to be radiused,some need knifed,theres a little trick to everything you cant just raise and lower the ports.

 

In my opinion nothing can beat the knowledge and skill of a qualified cutter

Laying it on a little thick, aren't we?

 

Let's cut the crap here.

A stock banshee engine makes a certain amount of torque at a certain rpm . This rpm is determined by certain factors, the main ones being the tuned length of the exhaust pipe and the other being the port timing.

Now Horsepower is torque times rpm. So if you have 50 lb of torque at say 3000 rpm, you wouldn't have bus say 25hp (numbers may be way off but the correlation is accurate". Now, if you can move that torque peak higher in the rpm range, say 6000 rpm, you would have effectively doubled the horsepower.

Now you must keep in mind that generally the torque curve is shaped like a mound, as in if you are looking at a dyno plot with rpm on the horizontal axis and horsepower on the vertical axis.

So basically the further you go away from the peak tq rpm in either direction, the less hp you will make.

 

The reason a banshee engine has so much potential, it that it is able to rev to a very high rpm, and if you can get the torque "hump" to slide over to the right (on the dyno plot, of coure), to say, 9000 rpm instead of the like 7000 or whatever it is- even without actually increasing the amount of torque that the engine makes (increasing airflow through the engine) you can raise the amount of hp drtastically.

 

This is what raising the transfer and exhaust ports do. It shifts the torque bump higher in the rpm range; this effectively increases total horsepower output and, at the same time reduces the amount of power down low.

 

Now about the pipe, the other important part of the equation. The pipe also determines when the engine makes its peak power.

 

How a pipe works: The exhaust pulse or pressure wave leaves the exhaust port and heads down the pipe. As it passes through the different diameters of the chamber, it caused the pressure inside the cylinder to fluctuate. This fluctuation actually "sucks" the rest of the exhaust out of the cylinder, pulls the fresh air/ fuel charge in, then pushes any fuel that may have escaped out the exhaust port back into the cylinder. (look at bansheemans sig). Anyway, the length of the pipe and its different diameters is what determines the peak hp rpm, as at that rpm the pulses going through the pipe reach a resonant, or harmonic frequency.

 

Long story short, a pipe can be tuned to 6, 7, 8, or 10,000 rpm or more, depending on the purpose (trail-low, dune-medium-drag-high rpm tuning.

 

So. you take a pipe that produced power at 10,000 rpm, shict the torque bump to peak at that same rpm and you will seriously bump the horsepower.

Now, I realize that there's more to porting than just increasing the port timings, but there's a VERY significant amount of power to be had by raising the transfer and exhaust port windows IF yo know how much to move each one.

 

My question, in a nutshell is if I slapped some shear pipes on my bike with the porting I have how many more hp could I expect from a drag port.

 

Thanxx

[SLORYDER]

Re

He

He

Heeeeee

aaaallllly

[sheefreak]

I am going to go out on a limb here and say you will be in the 65- 70ish horsepower range on methanol w/your current moddest port durations. If I am understanding your ? Correctly, I would say another 20ish hp could be had(on methanol) if you up'd those numbers to the 194-196 and 130ish areas. This number may require opening the transfers as much as possible and not f'ing up the angles the transfers are aimed into the cyl. I believe more power than that can be had if you do some welding on the transfers and really open them up.

 

I want to declare I do not do port work and only barely understand the basics. I am curious though if you may have already known what I just told you?

[sheefreak]

This is all on the assumption you are running the proper dome, timing, etc.

[Burt Reynolds]

I said it sounds like you were getting yourself into a mess because you didnt even know what area duration a drag port is. And you also said that you had to show them to someone before if you knew they were ok or not. I was just stating a point that i think you are selling yourself short by not letting an experienced person do it.

 

And no your question wasnt how much horspower difference will there be between a drag and dune port your question was "how close is my porting to drag?" Wich is what i responded to.

 

Anyone with a search button can spend all day on here spitting out 2 stroke facts,but it takes real experience and know how to do a proper port job. Wich is why im saying you would have been better off letting someone else do it.

 

Did you use a degree wheel? A little flashlight? Measure from the deck? Whats your blowdown? What angle are your main and secondary transfers? What size domes are you going to need to have proper compression because of the loss from raising the ports?

 

 

AALLLLLLLLLLLLRRRRIIIIGGGHHHTTTYYY THEN!

[SLORYDER]

I said it sounds like you were getting yourself into a mess because you didnt even know what area duration a drag port is. And you also said that you had to show them to someone before if you knew they were ok or not. I was just stating a point that i think you are selling yourself short by not letting an experienced person do it.

 

And no your question wasnt how much horspower difference will there be between a drag and dune port your question was "how close is my porting to drag?" Wich is what i responded to.

 

Anyone with a search button can spend all day on here spitting out 2 stroke facts,but it takes real experience and know how to do a proper port job. Wich is why im saying you would have been better off letting someone else do it.

 

Did you use a degree wheel? A little flashlight? Measure from the deck? Whats your blowdown? What angle are your main and secondary transfers? What size domes are you going to need to have proper compression because of the loss from raising the ports?

 

 

AALLLLLLLLLLLLRRRRIIIIGGGHHHTTTYYY THEN!

And you sir are a Burt Reynolds imposter.

I know he isn't this much of an asshole.

 

And to sheefreak no sir I wasn't aware that those increased durations would yield that much more power. I, however would not feel comfortable hogging out the intaes on my own though.

You are the man and I salute you for not being like the others on this forum who swing off the testes of the builders out here.

[SLORYDER]

BTW anyone know the stock durations off hand?

[Burt Reynolds]

170 something exhaust if i remember right,sorry if i came off like an asshole.

[mopar1rules]

179* if zero deck height and 181* if .017" deck height.

[troyzstang]

"And you sir are a Burt Reynolds imposter.

I know he isn't this much of an asshole."

 

 

Laughing my ass off

 

What a come back !

[SLORYDER]

Would o be ok bringing my exhaust up to about 192-194 with my transfers like they are or does that seem like a little much?

[sleeper06]

To me your blow down numbers seem low,I dont see a problem with going to 194 except limitations of the pipe.shearers and cpi are your best bet from 194 and up ex.drag ports are higher than 196.I personally have found that a staggered port design works better for me at least.Since I have started porting I learn something new on each set.Do your self a favor,build a whore motor and test shit out within the same parameters.I have personally spent thousands on tooling.A dremel and a dream is not going to get you where you want.I have wasted tons of parts on test peices but learned alot with what works and what does not.

[camatv]

just to let you guys know i stoped reading this post a few post's back. i just wanted to say that the more you increase the lower ends compression ratio ( welding transfers, cuttin g the trans tunnels up) the LESS tq or lower end midrange ( acceleration) the motor will make IT will make a nice big peak hp number but peak hp in a very short range wont get you down the track fast it will make a nice dyno number that you can brag about but if your a lil on the heavy side and its in a stock frame the motor will be a lil boggy and be very peaky and possibly harder to ride.. you can get some of this back through alky, lower rpm pipes ( cpi's) and less rotating weight..

( pistons, crank, flywheel, axle, lightweight frame stuff, NOS)

 

if it is really a 189 * exhaust its going to be a turd.. i think 189 is like stock with the sleeve hanging down in the port i think ( i dont rember ) if you just clean the sleeve out and make the port flat with the roof you end up with about a 192* which even with stock transfers runs ok., i would consider a 196* exhaust and a CERTAIN exhaust shape to be more to your liking and better suited to those "high rev" pipes.. the square style port in my opinion just plain SUCKS!! it causes unneded piston wear and creats a very flat peaky power band. the more d shaped or oval shaped it is the more it will pull.. just my experience with porting over the last 10 years.. i have recently been running a 198* exhaust duration on even the trail bikes. i know its crazy to some but the more i experiment with the actual shape of the exhaust the more linear i have been able to get the power band..

 

you have to rember the engine/ frame set up makes more difference to a bike than the actual porting.. BUT its all a "package"

[SLORYDER]

just to let you guys know i stoped reading this post a few post's back. i just wanted to say that the more you increase the lower ends compression ratio ( welding transfers, cuttin g the trans tunnels up) the LESS tq or lower end midrange ( acceleration) the motor will make IT will make a nice big peak hp number but peak hp in a very short range wont get you down the track fast it will make a nice dyno number that you can brag about but if your a lil on the heavy side and its in a stock frame the motor will be a lil boggy and be very peaky and possibly harder to ride.. you can get some of this back through alky, lower rpm pipes ( cpi's) and less rotating weight..

( pistons, crank, flywheel, axle, lightweight frame stuff, NOS)

 

if it is really a 189 * exhaust its going to be a turd.. i think 189 is like stock with the sleeve hanging down in the port i think ( i dont rember ) if you just clean the sleeve out and make the port flat with the roof you end up with about a 192* which even with stock transfers runs ok., i would consider a 196* exhaust and a CERTAIN exhaust shape to be more to your liking and better suited to those "high rev" pipes.. the square style port in my opinion just plain SUCKS!! it causes unneded piston wear and creats a very flat peaky power band. the more d shaped or oval shaped it is the more it will pull.. just my experience with porting over the last 10 years.. i have recently been running a 198* exhaust duration on even the trail bikes. i know its crazy to some but the more i experiment with the actual shape of the exhaust the more linear i have been able to get the power band..

 

you have to rember the engine/ frame set up makes more difference to a bike than the actual porting.. BUT its all a "package"

 

198 with what, a 135 exhaust?

Has anyone had success using a base plate to make increasing the transfer duration easier?