porting results on a 701 cylinder vs case

[masterblaster]

what kinda % in power gains are there in just good cylinder porting for freeride,vs the case porting as well on a 701. Ive heard about alot more cylin porting jobs being done than cases as well. looking at it as a large air pump,it doesnt seem to do alot of good to get more flow in one spot if its not matching in another,you would only be as good as the weakest link. Ive rode alot of ported cylinder 701 skis and been mostly unimpressed in the diff it made,though most of these have been stock carb boats.
Ive ridden some non ported skis with nice intake,reed setups with large 46 or 48 carbs and opened up exh manis and been very impressed with them.

Ive read that some port jobs can lessen fuel consumption and yet still make more power,how is this possible?

 

[LIVE2RIDE Powersports]

We ported my cylinders and it ripped. I am porting my 61x cases this winter. Not sure if that helps much on the 61x. They look restricted.

 

[masterblaster]

I am talking 62t cases and X cylinders

 

[WaveDemon]

I'm assuming your a car guy torr. I'll put it in car terms. cylinder porting is the same as a cam change. Depending on the cam it can make your stock motor run better but for the best performance you'll need the rest of the package too (intake, heads, possibly stronger bottom end).


cylinder porting is a lot more than creating more flow, it's also (and more importantly) changing port timing (same as valve timing in a 4 stroke).

 

[scottie mac]

Torr, you should give Erik a call he can port cases pretty good. He said he would do it for nothing.

Scottie

 

[kevbo]

About 90% of performance (power) lies in the cylinder porting, pipe, and pump load. If any one of these are not correct then power (thrust) will be down no matter what else is done. There is simply no way to make good power with a stock (yamaha) pipe, or a stock 61X cylinder for that matter. A little too much pump load will kill the performance of any engine.

 

[wsuwrhr]

As far as your fuel consumption question goes...if I understand correctly what you are asking...

My opinion is, obviously porting changes power or power delivery, this in essense changes how the ski reacts to power, more power delivery, the less you have to open the carbs to make the same power, the less the engine has to work to make the same power.

Less work, less throttle opening, less fuel being consumed.

Brian

 

[2XLR8]

About the only way you can gain power and increase gas milage is by increasing compression. If you port and alter the powerband to increase performance in the rpm range you need to operate I can't see doing this with better gas milage, unless you are tuned bad to begin with. If you port to increase air flow then it is assumed that there will be more fuel along with that extra airflow.

 

[wsuwrhr]

About the only way you can gain power and increase gas milage is by increasing compression. If you port and alter the powerband to increase performance in the rpm range you need to operate I can't see doing this with better gas milage, unless you are tuned bad to begin with. If you port to increase air flow then it is assumed that there will be more fuel along with that extra airflow.

Yes, but you are talking about WOT, the engine makes more power at any given RPM at less throttle opening.

 

[masterblaster]

scottie,yea I talked with him about it already,one of my 701 motors has everything thrown at it but big carbs and case porting,and it baffels me to no end how it compares to your spec boat.I know tuning is huge,but if mine is out of tune it is just by a little bit,far less than than the diff of power. its running 25 deg advance on a rad fly high comp and a sim pipe lpw cylinder porting carbon reeds...yada yada.
So what Im weighing here is just going bigger carbs,intake,cages....this I know is gonna burn more fuel and shorten my ride time,or stick with the 38s and try case porting for some better flow. Just got another set of novi 46s on a 2 piece 46 mill r&d mani sim to the one you were asking for. lost the bucks on the gp stroker.Jon and I bolted them up tonight.we will see what they can do,was thinking on trying them out on the 701 also to see how much more flow "power" they bring it.

Tim. I mean assuming everything else is nice and the same between the 2 comparisons in terms of % power gained. I dont mean moving sleeves or changing transfer roofs, most freeride ports are widening exh ports with minimal duration changes maybe 190 max.Ive seen x screams,lpw and Arts for this purpose.
Leaves me wondering what is gained with finger ports on the cases to match?Im sure there is a % for it for most aps

 

[joesuperjet]

I say you need to sweet talk Erik. Let him peform his magic. :biggrin:


JAM

 

[waxhead]

anything that raises thermal efficiency is going to help your fuel economy the same goes for mechanical efficiency
Things that improve your volumetric efficiency well that depends on the throttle loading

Mechanical efficiency = anything that loads the engine from rotating
thermal efficiency = the work preformed by x amount of fuel
Volumetric efficiency = the amount of new mixture you get in the cylinder

Remember this
you have to feed the ponies

 

[masterblaster]

I say you need to sweet talk Erik. Let him peform his magic. :biggrin:


JAM

LoL Well see what the magic man can do,how do you sweet talk the tuner extraordinaire into dialing it in?

Wax any ideas on %s gained in case porting in your experience

 

[waxhead]

Its a decent gain
Not going to guess at a % but its worth it for sure

 

[2XLR8]

Yes, but you are talking about WOT, the engine makes more power at any given RPM at less throttle opening.

I don't think that fuel usage is only based on throttle opening. This is only true in mechanical fuel injection. The jetting at rpms than at or near max rpms have a lot to do with other factors.

 

[Matt_E]

I don't think that fuel usage is only based on throttle opening.

If it were, you'd use a LOT more fuel running the ski on the hose than you actually are.
Engine load has a lot to do with it.

 

[wsuwrhr]

I don't think that fuel usage is only based on throttle opening. This is only true in mechanical fuel injection. The jetting at rpms than at or near max rpms have a lot to do with other factors.

If it were, you'd use a LOT more fuel running the ski on the hose than you actually are.
Engine load has a lot to do with it.

Exactly.

There are many factors to how much fuel is drawn out.

The main factor is how much the blades are open.

Brian

 

[masterblaster]

This ski used the same amount of fuel after the cylinder port,will be interesting to see if the case port makes any diff.The 48s deff used more fuel,dropping down to 46sto see if that makes any diff.They prolly provide more than enough fuel for low end setups
I dont see how there is any way more flow doesnt equal more fuel usage at any rpm,As long as its not ALOT more I can live with it.We just have a really long ride to our surf break,and its a PITA to bring extra fuel along

 

[2XLR8]

I'm sure everyone has cruised at the speed just below where the pipe and porting comes into play. There is a point where just a tiny extra throttle will get you like an extra 1000 rpm. If you cruise at that inefficient rpm it will consume more fuel. Law of physics apply and if you make more power it is usually needed to add more fuel unless you are too rich to begin with or you get to a much leaner condition than previously.
At cruising speeds of say 30 mph the perceived pipe tuned length can have a big effect on the efficiency factor. It is like a short pipe and only running the lowest screw versus opening the top screw.
Bigger carbs also require more fuel at lower speeds because the fuel droplets having to be bigger in order to have the proper response with out hesitating. This is due to the slower air speed through the carb. That is why the 38's get better fuel economy at cruise.
In response to crankcase adding more power after the port job I think the limiting factor will be the 38's. You would see more gain with the crankcase porting if you were to go with the bigger carbs. In my opinion crankcase porting has very little to do with air flow getting into the engine.

 

[masterblaster]

2xlr8 Thats why im trying the 46s with a r&d intake,carbontech reeds on this setup,just to compare,but id really like to run the 38s if I can cause its still a 701 and gets great fuel time.I can ride 2.5 hours on a tank,and thats about perfect for our main ride zone. Im starting to get hooked on my stroker ski though with 48s,so much more fun in small waves and any wave with reintrys. I only get about 1.5 hours on that setup,If we had a beach launch ride zone I would care less.