Whats better an Engine Dyno or a Thrust Tester

Automotive powered airboat discussion.
User avatar
executioner496
Southern Airboat Member
Posts: 7
Joined: Tue Jan 18, 2011 6:11 pm

Whats better an Engine Dyno or a Thrust Tester

Post by executioner496 » Tue Jan 18, 2011 6:45 pm

I'm looking at buying a motor for my boat. Right now my choice has come down to two motors for my bowfishing boat one engine comes with a dyno sheet and the other comes with a thrust dyno sheet. I'm just wondering which is better for my needs. I bowfish alot and use my boat for field work. I think both motors are tested and come with a build sheet and warranty but I think thrust testing will help me end up with the most thrust out of my combo.

User avatar
sidejobs
Southern Airboat Member
Posts: 1042
Joined: Fri Oct 01, 2010 7:41 pm
Location: chocolate city, fl

Re: Whats better an Engine Dyno or a Thrust Tester

Post by sidejobs » Tue Jan 18, 2011 7:10 pm

it would be great to have both
________________
IDIOT !

User avatar
JAMES
Site Supporter - II
Site Supporter - II
Posts: 8569
Joined: Wed Aug 22, 2007 10:31 pm
Location: cocoa
Contact:

Re: Whats better an Engine Dyno or a Thrust Tester

Post by JAMES » Tue Jan 18, 2011 7:12 pm

thrust tester.... if it was done with a prop it might be the way too go that the proof of what u have !jmo
people can make dyno sheets and make em say what they want them to ......
are these new or used motors
https://m.facebook.com/321ccc/?ref=bookmarks Wp383 268 rotator 3 bld WT/EX 14.4 perdator

stan
Site Supporter - IV
Site Supporter - IV
Posts: 871
Joined: Tue Apr 19, 2005 7:41 pm
Location: DeLeon Springs,FL

Re: Whats better an Engine Dyno or a Thrust Tester

Post by stan » Tue Jan 18, 2011 8:13 pm

Dyno , Just mutiply the horsepower times three at the maximum RPM you intend to run at will give you the appoximate thrust you should obtain. The reverse holds true for thrust test say 1800 #s of thrust at 6000 rpms will be in the neighbor hood of 600 horse.

flying fish
Site Supporter - II
Site Supporter - II
Posts: 1877
Joined: Thu Jun 21, 2007 11:09 pm
Location: Elkhart, Kansas

Re: Whats better an Engine Dyno or a Thrust Tester

Post by flying fish » Tue Jan 18, 2011 8:27 pm

Thrust Tester better hands down. Also seems guaranteed you can make that much thrust with exact combination. Also thrust would have been achieved with best combination for that engine and gear package. Wow!!!! Why would combination not be the best?? If there were something better, engine builder would surely use this better combo to help sell his product. Just my thinking.

Thrust tester proven combo and correct fuel curve exact for propellor load. Very important this fuel curve..
can't simulate prop load on dyno.
can't tune primaries on dyno simulating prop load.
easy to go lean on primaries dyno tuning then adding prop.
Last edited by flying fish on Tue Jan 18, 2011 8:29 pm, edited 1 time in total.
15' DB - 6.2 LSA - 4 blade 82" R - 2.52 CH-4

greenhorn480
Southern Airboat Member
Posts: 181
Joined: Fri Aug 28, 2009 4:49 pm
Location: Cocoa FL

Re: Whats better an Engine Dyno or a Thrust Tester

Post by greenhorn480 » Tue Jan 18, 2011 8:28 pm

Either is good but to say multiply HPX3 to get thrust is no ware near acurate. That leves no regard for gear ratios or props. That would be like saying just take cubic inches times 1.5 to get your HP on a pump gas motor. With that logic if I take my old Lycoming 180HP X 3 that means I make 540lb's of thrust. I garantee you my 180 made more then 540lb's of thrust.

stan
Site Supporter - IV
Site Supporter - IV
Posts: 871
Joined: Tue Apr 19, 2005 7:41 pm
Location: DeLeon Springs,FL

Re: Whats better an Engine Dyno or a Thrust Tester

Post by stan » Tue Jan 18, 2011 8:35 pm

greenhorn480 wrote:Either is good but to say multiply HPX3 to get thrust is no ware near acurate. That leves no regard for gear ratios or props. That would be like saying just take cubic inches times 1.5 to get your HP on a pump gas motor. With that logic if I take my old Lycoming 180HP X 3 that means I make 540lb's of thrust. I garantee you my 180 made more then 540lb's of thrust.
Have you had it on a dyno? maybe theres more than 180 horse.

User avatar
Whitebear
Site Supporter - VIII
Site Supporter - VIII
Posts: 16555
Joined: Thu Jan 05, 2006 7:49 pm
Location: Palm Bay, Fl
Contact:

Re: Whats better an Engine Dyno or a Thrust Tester

Post by Whitebear » Tue Jan 18, 2011 8:38 pm

A thrust tester actually MEASURES thrust, which is what moves your boat.

When thrust is measured with the engine, re-drive,and prop, plus all the timing and induction tuning, its all SPOT on. Really makes little difference what the or a dyno says. Calculating thrust and measuring thrust are frequently quite different operations.

Thrust testing come into the custom build & tune realm and dyno is more or less a standard shop tool. Some are accurate and some aren't. Some get fudged, and some don't. Not sure HOW anyone could fudge a thrust test. Its either there or it isn't.
"The Constitution is not so the government can restrain the people, it is so the people can restrain the government." Patrick Henry
The government cannot give anything --
that they have not first taken from someone else.

User avatar
:)
Site Supporter - I
Site Supporter - I
Posts: 2110
Joined: Thu Jul 08, 2010 8:07 pm
Location: Baker County, Florida
Contact:

Re: Whats better an Engine Dyno or a Thrust Tester

Post by :) » Tue Jan 18, 2011 8:52 pm

Waterthunder has a little thing on his website I believe. Covers exactly what ur talkin about and explains the difference a little
14 ft Combee. 4 seater, BPE 383 sb chevy, 2.09 stinger, 3 blade ww stump puller.
"When the people fear their government, there is tyranny; when the government fears the people, there is liberty." Thomas Jefferson

stan
Site Supporter - IV
Site Supporter - IV
Posts: 871
Joined: Tue Apr 19, 2005 7:41 pm
Location: DeLeon Springs,FL

Re: Whats better an Engine Dyno or a Thrust Tester

Post by stan » Tue Jan 18, 2011 8:53 pm

I would agree untill the varibles are considered ei altiude, tempature, barometric presure,wind direction and speed at time of test, humidity,the operator and the equipment used which would probley make a thrust test as accurate and repetable as a dyno ,but know better or worse. There is however advantages of gaining information and knowlege from both.

greenhorn480
Southern Airboat Member
Posts: 181
Joined: Fri Aug 28, 2009 4:49 pm
Location: Cocoa FL

Re: Whats better an Engine Dyno or a Thrust Tester

Post by greenhorn480 » Tue Jan 18, 2011 8:57 pm

thats funny your x3 formula doesn't compensate for anything you just stated that had to be compensated for. i doubt she even made 180hp she was a wore out airboat motor that was bone bone stock i think one cylinder only had 90lb's. so by your x 3 formula your saying if a put a 2to1 gearbox on it it she will still only make 540lb's of thrust Your times 3 theroey doesn't even compensate for a gearbox i think ya beter go back to the drawing board and modify your formula

User avatar
JUNIOR480
Site Supporter - II
Site Supporter - II
Posts: 927
Joined: Thu Apr 03, 2008 8:03 pm
Location: the getto...

Re: Whats better an Engine Dyno or a Thrust Tester

Post by JUNIOR480 » Tue Jan 18, 2011 9:00 pm

you can take a engine and run it on 5 dynos and get five different readings and im sure it would be the same for the thrust tester if there where five to compare...the bottom line is the both are tuning tools and one is not better then the other...
HAULIN A$$ SINCE 78......

User avatar
plumcrazy
Site Supporter - V
Site Supporter - V
Posts: 8697
Joined: Thu Apr 06, 2006 10:10 am
Location: avon park

Re: Whats better an Engine Dyno or a Thrust Tester

Post by plumcrazy » Tue Jan 18, 2011 9:16 pm

well a aircraft can make lots of thrust with a little bit of hp and a car motor can make alot of hp with alittle bit of thrust 8) but i got to say that you can look at the prop and pitch if you been around airboats a while and if you know wot rpms then you got to know hulls riggin and such; this crap will drive you nuts that why ive had differant boats. the best boat is the one you have at any given time. so spend your money wisely cause once its gone its gone good luck :)

cntry141iq
Site Supporter - VI
Site Supporter - VI
Posts: 10136
Joined: Fri Sep 03, 2004 9:31 pm
Location: bradenton florida
Contact:

Re: Whats better an Engine Dyno or a Thrust Tester

Post by cntry141iq » Tue Jan 18, 2011 9:19 pm

well powershift used to brag about generating 4 ponds of thrust per hp with what was purported to be a 300 hp 540 a/c. there was lots of controversy over the strain guage used and the kicking of the cable to help it make it but i wasn't there but some of my firiends were and they are airboat ledgends who don't lie so I beleive em. the three pound numbe ris more real world than the four pound number. but choose which ever one you want 3 or 4 greenhorn it still aint the number you are probably looking for ... is it ??? what number would you like to install in the equation ...
Don't waste your time ... it is the only thing you can't get more of
.. if it accidentally looks like I gave advice please ignore it .. and notify me immediately

User avatar
garrett
Site Supporter - III
Site Supporter - III
Posts: 126
Joined: Sun Jan 21, 2007 12:56 am
Location: FLORIDA

Re: Whats better an Engine Dyno or a Thrust Tester

Post by garrett » Tue Jan 18, 2011 9:21 pm

all the above are somewhat true, but if i where building a custom tractor,(for pulling) i would rather test it pulling against a tensiometer, rather than putting it on a dyno , because in the end all you really care about is how hard does it pull.......
PERFORMANCE IS NO LONGER A THEORY!
904-251-5274
15ft deckover, 620 H.P. 496 wheeler, 2.55 stinger, 3 blade sw (and i need more blades)

RiseAboveIt
Site Supporter - II
Site Supporter - II
Posts: 639
Joined: Thu Apr 16, 2009 10:50 pm
Location: Bushnell, Florida

Re: Whats better an Engine Dyno or a Thrust Tester

Post by RiseAboveIt » Tue Jan 18, 2011 9:21 pm

I would rather have a dyno sheet from a reliable builder... Something that would come with a build sheet and show where the horsepower and torque curses run... There is enough info online to figure out from there what ratio box and prop to use for your needs...jmo

Also... I go for the longest warranty I can buy... Cause I'm hard on my stufff...

Just saying...
No matter what happens... Just Rise Above It.

greenhorn480
Southern Airboat Member
Posts: 181
Joined: Fri Aug 28, 2009 4:49 pm
Location: Cocoa FL

Re: Whats better an Engine Dyno or a Thrust Tester

Post by greenhorn480 » Tue Jan 18, 2011 9:25 pm

i don't think there is a formula i don't think one can be done yet because of to many variables such as gear ratio and prop blade, prop dia and it just goes on an on i think the only way to know thrust is to run the entire combo on a thrust tester --now that i think about it only a thrust tester can help you make more thrust a dyno just tells you how much power your motor makes it cant tell you anything about your prop your pitch or your ratio i mean relly what can you do with a dyno sheet besides read it

User avatar
grant
Site Supporter - VII
Site Supporter - VII
Posts: 3425
Joined: Sat Jul 29, 2006 12:03 pm
Location: Felda, Florida
Contact:

Re: Whats better an Engine Dyno or a Thrust Tester

Post by grant » Tue Jan 18, 2011 9:36 pm

I think thrust tester ......however it is only a tool for tuning drive combo for best NUMBERS!
After that you still gotta mount it on a hull w/riggingl....the right hull and rigging and properly tune the combo, or else it will likely just be a PIG....with big NUMBERS :twisted:
"Don't Taze me Bro"

User avatar
plumcrazy
Site Supporter - V
Site Supporter - V
Posts: 8697
Joined: Thu Apr 06, 2006 10:10 am
Location: avon park

Re: Whats better an Engine Dyno or a Thrust Tester

Post by plumcrazy » Tue Jan 18, 2011 9:40 pm

the best tester is the ass in the seat . just sayin. if any body wants to argue that then its on, :twisted:

cntry141iq
Site Supporter - VI
Site Supporter - VI
Posts: 10136
Joined: Fri Sep 03, 2004 9:31 pm
Location: bradenton florida
Contact:

Re: Whats better an Engine Dyno or a Thrust Tester

Post by cntry141iq » Tue Jan 18, 2011 9:40 pm

set your prop to where your engine makes its power ... I have thrust tested engines that have been dynoed and shazam the peak thrust came right where the engine made the most power .. gear ratio's don't make power or thrust they allow the engine to get to the power in it. props don't make power they transmit rotaional power of the engine into thrust ...

Do ya'll really think prop manufacturers have no idea what power it takes to make thrust ??? Ya'll really think they have never tested thrust .. ??? THEY KNOW and there is a formula and they know it .. yes it is a loose formula but it is very close everytime .. but you gotta remeber engine builders live and die for just a few hp .. a 20 hp difference on a engine is huge for them but on a boat it is almost nothing on a carmotor setup running on a normal boat setup. In a race car 20 hp would break your tires loose coming out of the corner ..
Don't waste your time ... it is the only thing you can't get more of
.. if it accidentally looks like I gave advice please ignore it .. and notify me immediately

greenhorn480
Southern Airboat Member
Posts: 181
Joined: Fri Aug 28, 2009 4:49 pm
Location: Cocoa FL

Re: Whats better an Engine Dyno or a Thrust Tester

Post by greenhorn480 » Tue Jan 18, 2011 9:43 pm

good point grant i have seen some bad motors with a ton of power run like crap on the boat they were mostly car motors of coarse

User avatar
grant
Site Supporter - VII
Site Supporter - VII
Posts: 3425
Joined: Sat Jul 29, 2006 12:03 pm
Location: Felda, Florida
Contact:

Re: Whats better an Engine Dyno or a Thrust Tester

Post by grant » Tue Jan 18, 2011 9:45 pm

greenhorn480 wrote:good point grant i have seen some bad motors with a ton of power run like crap on the boat they were mostly car motors of coarse
Lot of A/C PIGS out there too :shock: :D :D
"Don't Taze me Bro"

greenhorn480
Southern Airboat Member
Posts: 181
Joined: Fri Aug 28, 2009 4:49 pm
Location: Cocoa FL

Re: Whats better an Engine Dyno or a Thrust Tester

Post by greenhorn480 » Tue Jan 18, 2011 9:47 pm

thats funny cnt14 so you say you turn the motor the same no matter wahta ratio man some of whats being said makes no sense and contradicts it's self in the same senstance you say you turn the motor the same no matter what lenght prop now that is wrong everybody knows you change prop speed when you change prop dia i see that many people comenting have no idea what their talking about im with grant and flying fish

cntry141iq
Site Supporter - VI
Site Supporter - VI
Posts: 10136
Joined: Fri Sep 03, 2004 9:31 pm
Location: bradenton florida
Contact:

Re: Whats better an Engine Dyno or a Thrust Tester

Post by cntry141iq » Tue Jan 18, 2011 10:05 pm

ROFLMAO believe what you will ... I never said anything you typed ..
Don't waste your time ... it is the only thing you can't get more of
.. if it accidentally looks like I gave advice please ignore it .. and notify me immediately

greenhorn480
Southern Airboat Member
Posts: 181
Joined: Fri Aug 28, 2009 4:49 pm
Location: Cocoa FL

Re: Whats better an Engine Dyno or a Thrust Tester

Post by greenhorn480 » Tue Jan 18, 2011 10:08 pm

ahh here are your words you stated the peak thrust will be where the rpm's the motor maskes peak power without any regard to what rpm the prop turns
I have thrust tested engines that have been dynoed and shazam the peak thrust came right where the engine made the most power

Post Reply

Return to “Automotive Power Only”