Highest RPM's on a 75cc?
04-15-2002, 01:16 AM
#1
Thread Starter
My Feedback: (6)
Join Date: Dec 2001
Location: Frisco, TX
Posts: 169
Likes: 0
Received 0 Likes
on
0 Posts
Highest RPM's on a 75cc?
I was looking at the Formula 1 giant air racing 42% planes. The biggest engine you can have is one that is 75cc. Which 75cc engine out there has the highest performace for a racing style plane? -Steve
04-15-2002, 01:31 AM
#2
Senior Member
My Feedback: (4)
Join Date: Jul 2002
Location: Somewhere,
DC
Posts: 9,825
Likes: 0
Received 0 Likes
on
0 Posts
Race engines
The engine of choice is the Zenoah 445 twin...The good ones are turning close to 11,000 rpm in the air, about 175 mph..The Q75 is a close second..I don't know af any other engines being used at this time..The GR7 is winning all the races, but there will be some new Polecats this year, and maybe a few others..Check out the USRA web page at www.usra-racers.org for rules, pictures, and anything else you want to know..
I'm turning the two I have here at 11,000 rpm to test the carbs..
Engine spec goes to 81cc next year...
I'm turning the two I have here at 11,000 rpm to test the carbs..
Engine spec goes to 81cc next year...
04-15-2002, 01:38 PM
#4
Senior Member
My Feedback: (4)
Join Date: Jul 2002
Location: Somewhere,
DC
Posts: 9,825
Likes: 0
Received 0 Likes
on
0 Posts
zdz80
The rules dor this year limit engine size to 75cc
Next year is 80 cc..If the zdz is 80cc or less it will be legal..
Sometimes manufacturers call and engine something else other than what it actually is..The bore and stroke would have to be measured to see....RC
Next year is 80 cc..If the zdz is 80cc or less it will be legal..
Sometimes manufacturers call and engine something else other than what it actually is..The bore and stroke would have to be measured to see....RC
04-15-2002, 10:00 PM
#5
Highest RPM's on a 75cc?
I would venture that the 75 Zenoah is slicked up a little to produce good performance at 11 grand?
My limited experience with this engine at 5--6000 rpm showed very limited performance -
I was only an observer/flyer - but it sure seemed like it was very meek.
My friends who run the 80 agree - these are quite tame in stock form.
Have you come up with any mods that wake these things up --in the 6000 rpm range?
My limited experience with this engine at 5--6000 rpm showed very limited performance -
I was only an observer/flyer - but it sure seemed like it was very meek.
My friends who run the 80 agree - these are quite tame in stock form.
Have you come up with any mods that wake these things up --in the 6000 rpm range?
04-15-2002, 11:41 PM
#6
Senior Member
My Feedback: (4)
Join Date: Jul 2002
Location: Somewhere,
DC
Posts: 9,825
Likes: 0
Received 0 Likes
on
0 Posts
445
I was running 2 "slicked up" Zenoah twins to test carb..The prop was a 16-12 wood..The fuel was 20% nitro..The exhaust is 7 inches long, to comply with the rules..Tested 4 different carbs..WJ64 modified for methanol, a $400.00 EC Birt Tillotson, a
Walbro SDC 80,and a Herbrandson twin drone carb, modified and bored out to 23 MM..
They ran within 1 or 200 rpm of each other..Then I took a stock 445 to test with the 4 carbs..Almost the same result..Makes me wonder why we take the time to modify the stockers..
We'll test the engines in the race plane, with a race prop, later..The reason for the 11,000 rpm is to test the carbs at the rpm the engine turns in the air..
The instructions that come with the 445 recommend props that will turn bertween 7 and 10,000 in the air, so there's no wonder the engine seems meek at 5 or 6,000..Like running a car at 20 mph in 3rd gear..The instruction also say the max power is at 10,000 rpm--Who reads instructions ??
If you want power at 5,000 rpm, get a 3W or DA that was designed to run at that speed....
The modified engines might unload better with the race prop...
Walbro SDC 80,and a Herbrandson twin drone carb, modified and bored out to 23 MM..
They ran within 1 or 200 rpm of each other..Then I took a stock 445 to test with the 4 carbs..Almost the same result..Makes me wonder why we take the time to modify the stockers..
We'll test the engines in the race plane, with a race prop, later..The reason for the 11,000 rpm is to test the carbs at the rpm the engine turns in the air..
The instructions that come with the 445 recommend props that will turn bertween 7 and 10,000 in the air, so there's no wonder the engine seems meek at 5 or 6,000..Like running a car at 20 mph in 3rd gear..The instruction also say the max power is at 10,000 rpm--Who reads instructions ??
If you want power at 5,000 rpm, get a 3W or DA that was designed to run at that speed....
The modified engines might unload better with the race prop...
04-16-2002, 01:35 AM
#7
Highest RPM's on a 75cc?
I guess I am lost then-
are we speaking of the same 445 and the 80 twin that Zenoah sell thru Horizon?
The pattern engines do run at 8000 unloaded but I imagined they wer sold to an audience which was NOT a racing audience .
Understand - I am not an anti racer guy- just trying to sort this out.
(I have had plenty of racing engines from 6000 rpm flathead Fords to 8000 rpm Chevs to Mac 10's in Karts etc.)
are we speaking of the same 445 and the 80 twin that Zenoah sell thru Horizon?
The pattern engines do run at 8000 unloaded but I imagined they wer sold to an audience which was NOT a racing audience .
Understand - I am not an anti racer guy- just trying to sort this out.
(I have had plenty of racing engines from 6000 rpm flathead Fords to 8000 rpm Chevs to Mac 10's in Karts etc.)
04-16-2002, 06:22 PM
#8
Senior Member
My Feedback: (4)
Join Date: Jul 2002
Location: Somewhere,
DC
Posts: 9,825
Likes: 0
Received 0 Likes
on
0 Posts
445
Same engines..They're not meant to be 6000 rpm engines..At least 7000 in the air is way better..A 24-10 Zinger will turn that rpm and hover my 24 lb cardboard plane, call a Ruler by the designer...
