Sub piston induction.

[Ian Inverarity]

I was putting a new piston and sleeve into my 90 on Thursday and made a big mistake and snagged the piston in the case causing a small piece of the skirt to break off. Now at TDC the piece out of the skirt opens up at the bottom of the exhaust port making a window about 1.5mm x 4mm.

Not having the time to fit yet another P&L I decided to run the motor to see if it still worked. And it doesnt seem to run very well at all. I had real difficulty launching props that I could easily run before, I was down on speed by about 15k and the motor struggled to stay on pipe.

What makes me unsure tho is this was also the first time I have run it in a completely new rigger hull.

Has anyone else had a similar experience with sub piston porting or should I be looking for other problems? :huh:

Nitrocrazed racing: Doh!!!!

 

[Don Ferrette]

It's time to replace the piston & sleeve. I've only seen sub porting work well once, all other times it absolutely killed all low end power. :huh:

 

[Ian Inverarity]

Don,

****!

Yep, the motor had no torque. :blink:

Thanks for the info!

Nitrocrazed racing: Happy to take advice from a 'Beginner'

 

[TimD]

What was the line from that corny TV show?

"We have the technology, we can rebuild him!"

 

[Ian Inverarity]

Not sure about the technology, but we do happen to have another piston that will go, if a little tight! B)

Nitrocrazed racing: Redundant new boat parts....

 

[Danny Bull]

I remember many years ago playing with sub piston porting, the theory being that it allows exhaust pressure or probably more correct, a pulse pressure wave to add a little extra charge to the crank case to increase boost of the air/fuel mixture. With limited success on gas engines (well I though it worked anyway) I'm probably a little out of my league with this stuff and I'm sure I'll be corrected if my terminology is wrong.......lol B)

What technology can't fix, $$$$$$$$ will !

Cheers, Danny.

 

[Hap Mulvany]

Turn the piston 180 degrees then the broken part may even help your induction and the exhaust will be closed off.

 

[Ian Inverarity]

Hap,

The piston is already skirted on the inlet side, so unfortunately that isnt an option!

Ian.

 

[HendricX]

Raise the sleeve..adjust head ?

 

[Don Ferrette]

Don't think he's got that much room...............

 

[Ian Inverarity]

Hendric,

If I raised the sleeve enough so that the exhaust port no longer opened at TDC then the rest of the timings would be WAY too wild to run!! :huh:

The sleeve is already raised a bit....

Ian.

 

[Mamerjammer]

290 views fer a broke skirt ? h34r:

Place piston in left hand, Throw over right shoulder, Install new piston CAREFULLY,

Take two asprin and relax, You will be better in the morning.........

The show was The Six Million Dollar Man, Steve Austin played by that guy that used to be married to Farrah, Oh yeah Lee Majors........ :lol:

 

[Slideblues]

He,He,He,.........Guess who??????????

Gene

Phase III Racing: Dats 1483, total posts for Me.......... but Ian seems to be stuck, at 1303

 

[Ian Inverarity]

Gene,

But I spent a couple of hours modifying and fitting the new broken one, then wasted a whole lot of fuel running it in! Doh! <_<

It was funny, Mike G and I both ran our riggers on the weekend he was happy with the speed he got, I went faster but I was pi$$ed off with how slow I was!! :blink:

Yeah, yeah, you post me than me, I know! I cant post so much now that I have changed jobs and actually need to work again!

Nitrocrazed racing: Not Sir Post-a-lot...

 

[Slideblues]

Oh you have been running with Mikie G. ? :blink:

Well that explaines it!!!!!

How do ya do rasberries in text.....Pffffffffssssstttttt.......

The Gillman with two L's

Gene B)

 

[Mike G]

LOL, I just have to be fast enough, Ian has to be the fastest!

He's got that small boat mentality! Trying to race a single 90 against all those twins!

That and the fact that mine is my first, and a Gasser!

Get outta my lane, lane one is mine! Not afraid to turn right! B)

 

[TimD]

He's got that small boat mentality! Trying to race a single 90 against all those twins!

Nothing wrong with running a single in X hydro against the twins! Richard S proved that at the HV champs this year. 2 engines doesn't mean twice as fast! Twice the fuel costs tho' :huh:

Tim.

 

[Slideblues]

Think I know why the water swirles backward down there now.......... :wacko:

 

[TimD]

Yeah - it 'cos of all the twin's in X Hydro. :lol: :lol: Surf's up!

 

[Toledo tunnel Man]

Remember the man with the most toys win. My wife has been parking outside from the first day we moved in to our house.My 71 chevelle on one side my two sleds on the other, and the kids are traned to stay out! of the garage or suffer the consaquences.I have a nice room for my boats that use to be the kids play room i booted them out all toys in there own room, only have four boats im way behined most of you, one on the way in two week i run them all just take two or three at a time.