SMALL - SMALL - Telemetry SMALL - Radio
Thread Tools
Old Jan 15, 2013, 04:46 AM
Registered User
United States, OR, Portland
Joined Dec 2010
127 Posts
mufflers for OS fs-70 ultimate

I've got a question regarding fs-70ultimate's muffler.

I know that the fs-70u has a fuel pressure system so it does not need fuel tank pressurisation from exhaust pressure like most non-pumped engines.

earlier today I found a shop selling fs-70u mufflers ( f4020u 45925050) but I couldn't remember if there was a pressure nipple on the muffler.

anyone have a clue on this?
murcielago is offline Find More Posts by murcielago
Reply With Quote
Sign up now
to remove ads between posts
Old Jan 15, 2013, 06:19 AM
Registered User
DarZeelon's Avatar
Israel, Ramat HaSharon
Joined Nov 2003
1,333 Posts

Your assumption is correct.
Engines that use a fuel-pump, like the OS.70 Ultimate, neither need nor use a pressurized fuel-tank.

The only reasons a pressure fitting might exist on the Ultimate's muffler, is if it is use to burn-off excess oil (connected to the crankcase breather), or if it is a carry-over from earlier Surpass engines.

Earlier YS (Yamada) engines differ, since their pressurized fuel-system requires the tank to be highly pressurized (over 5 psi, compared to ~.3-.6 psi for muffler pressure).
This is done by timed pressure from the crankcase - not from the muffler.
DarZeelon is offline Find More Posts by DarZeelon
Reply With Quote

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Sold NIB OS FS-70 Ultimate Pumped SFT2 Aircraft - Fuel - Engines and Accessories (FS/W) 4 Apr 23, 2013 04:36 AM
Wanted Mufflers for OS 91 Surpass and OS 61 FS needed shooboy Aircraft - Fuel - Engines and Accessories (FS/W) 11 Jul 23, 2012 08:14 PM
For Sale NEW OS Max 70 FS Ultimate Four Stroke LCS Aircraft - Fuel - Engines and Accessories (FS/W) 1 Jun 08, 2012 07:09 PM
FS: Brand new OS .70 Surpass Less Muffler $125 + Shipping AcroFlyer Aircraft - Fuel - Airplanes (FS/W) 1 Nov 24, 2003 10:59 PM