If you ever have the chance to talk to someone who's built a pro level full mod engine, who has done the dyno time, they will tell you that programs only give starting points. After dyno comes on water verification. The ports give the nessesary size opening for the required charge to enter and exit through in a given time, but there is more to how the ports work along with the rest of the engine design. There is no absolute for port dimension. The thing is to understand the relationships of the varibles so you can make changes in the correct direction. When reading posts on these boards you have those who want someone to think they know what there talking about, so they tell of their experiances or tell of what someone else did as if its absolute. I have rode mod race engines 800cc with over 129 degrees of trans timing with more bottom end than a notable freestyle builders 950cc engine. So yes, there are starting specifications but its better to understand how it works and relates than just repeat a few diagrams and duration numbers. Get books, read, so when you see something or get to listen a top builder speak you'll understand what they say and can soak it in like a sponge. Whats funny is the more you know the less you'll be able to communicate with the guys on the beach because you'll talk over their heads and sound like a know it all, then they quit talking to you cause most of what they say is wrong or dribble and when you tell them so, it pisses them off.
Transfer Port Sizes
- Thread starter x2skier
- Start date
To add to what egbrig said, the porting isn't designed to stand by itself.
Reputable builders build package with all variables as close to harmonious as possible.
The porting for an engine that will be run on pump gas and a stock ignition will be quite a bit different than the porting for an engine that will be run on race gas with a programmable ignition.
Exhausts, reeds, ignition, impellers, carbs are not just simple, interchangeable bolt-ons that will produce identical results on every engine.
An engine built as a package will have porting designed for the entire application. Even seemingly minor things such as cooling, water routing, etc have an impact on porting performance.
I never realized this before talking to someone who truly knows what they're talking about.
The more I learn, the more I realize how little I know.
Reputable builders build package with all variables as close to harmonious as possible.
The porting for an engine that will be run on pump gas and a stock ignition will be quite a bit different than the porting for an engine that will be run on race gas with a programmable ignition.
Exhausts, reeds, ignition, impellers, carbs are not just simple, interchangeable bolt-ons that will produce identical results on every engine.
An engine built as a package will have porting designed for the entire application. Even seemingly minor things such as cooling, water routing, etc have an impact on porting performance.
I never realized this before talking to someone who truly knows what they're talking about.
The more I learn, the more I realize how little I know.
- Location
- South Africa
The programs shorten the calculation time only. The Blair book is so technical that you get the essentials by reading it, the programs are needed for the calcs as otherwise you would take forever to do it.
I'm building a freestyle motor now with 127 degrees of transfer duration and power peak is set for only 6000rpm. Blowdown, port sizes, crankcase compresson, port angles, head design, reedvalve design, carb size, wetted hull area, pump intake gullet, pump, impeller, etc. The list is almost endless for the variables you need to take into account.
This is one of the reason I build my own pipes, I struggle to see how the PF drypipe can work on a multitude of engine setups. Must give it up for Supertune that he steers people away from it if he doesn't think their setup is right for it, many another dealer would just go for the $$
Any pipe sold should at least have a reccomended exhaust duration and pipe temp on the sales packaging.
I'm building a freestyle motor now with 127 degrees of transfer duration and power peak is set for only 6000rpm. Blowdown, port sizes, crankcase compresson, port angles, head design, reedvalve design, carb size, wetted hull area, pump intake gullet, pump, impeller, etc. The list is almost endless for the variables you need to take into account.
This is one of the reason I build my own pipes, I struggle to see how the PF drypipe can work on a multitude of engine setups. Must give it up for Supertune that he steers people away from it if he doesn't think their setup is right for it, many another dealer would just go for the $$
Any pipe sold should at least have a reccomended exhaust duration and pipe temp on the sales packaging.
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crammit442
makin' legs
- Location
- here
Ain't it the truth. Numbers are no doubt important, but give me an experienced builder with an intuitive sense of how it all works together every time. I prefer builders who cut their teeth in racing. Racing gives measurable, objective ways to evaluate modifications that are hard to replicate in the "freestyle" world. "Hardest hitting boat ever" doesn't really mean much to me when you consider all the possible variables. Something as simple as a really loud boat will sometimes give the illusion of big power. A lot of times, perception IS reality in freestyle. IMO, the ability to observe and accurately read mechanical trends is rare and is a good bit of what separates good builders from really great ones.
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man, I only wish. I agree with the other comments. I'll put any of my race 130 transfer duration motors with high exhuast duration up against a "freestyle" motor for hit. Race motors are all about "HIT" off the line.
Do you make your own exhaust manifolds? thats were most of the work I think is needed.
SUPERTUNE
Race Gas Rules
- Location
- Clearwater Fl.
Yes, This CAN be true, but not always.
Most race porting that your speaking of requires MSD TL, High compression w/race gas and expensive carbs. A lot of the time this is not freestyle friendly for some.
- Location
- South Africa
Use manifolds available, one day I will have the motivation to make one
worked pretty good.JAM
D
Dr.Nikich
Guest
Please,
Hello! please, if it is not so difficult for you, send me too some articles or any other information about 2 stroke engines.
This site is the basic source of information for me. And your posts are very informative.
alex_nike@mail.ru
Best regards, Alex. Russia.
Hello! please, if it is not so difficult for you, send me too some articles or any other information about 2 stroke engines.
This site is the basic source of information for me. And your posts are very informative.
alex_nike@mail.ru
Best regards, Alex. Russia.
D
Dr.Nikich
Guest
#.0, please, give me some information about 2-stroke....
Hello! please, if it is not so difficult for you, send me too some articles or any other information about 2 stroke engines.
This site is the basic source of information for me. And your posts are very informative.
alex_nike@mail.ru
Best regards, Alex.
Russia.
Hello! please, if it is not so difficult for you, send me too some articles or any other information about 2 stroke engines.
This site is the basic source of information for me. And your posts are very informative.
alex_nike@mail.ru
Best regards, Alex.
Russia.
davidescu_radu
sea riders
- Location
- Constanta,Romania