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RPMs @ 70 MPH

vicco27

By vicco27
in Watering Hole

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vicco27

vicco27

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I have a question. All of you with 83 thru 91 first & second gen Venture & Venture Royales, could you please tell me what you'r engine is turning at 70 MPH? As most of you know it took me three years to turn our 89 Venture Royale into a trike, which I finished last spring and we took on a 4000+ mile trip. However I can't remember what RPM the bike used to turn at 70 so I don't know if my gearing is right or wrong. Thanks in advance.

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twigg

twigg

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That was a "how long is a piece of string?" question with no definitive answer :)

 

What we see on the dash is pretty meaningless, depending as it does on the accuracy of both the speedo and tacho, neither of which are great. Even were they perfect it would also depend on the actual rolling circumference of the front tyre.

 

You can work out what it should be from the gear and final drive ratios, and an accurate speed but my question is why do ya want to know?

 

Is it just a ballpark figure you are after?

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BradT

BradT

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What we see on the dash is pretty meaningless, depending as it does on the accuracy of both the speedo and tacho, neither of which are great.

 

Is it just a ballpark figure you are after?

 

First gens speedo's are pretty much dead on, but a second gen is off about 7% on speedo and 2% on odometer.

 

Vicco after Triking what is your RPM ?

 

Brad

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vicco27

vicco27

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My gearing in the trike now is giving me a reading of 3800 at 65. With all the response you guys have given me I am now sure the 3.27 rear gear is too low and my plans of changing up to a 3.08 is the right choice. Thanks for all the replies.

 

The change will also help my fuel mileage. Thanks again!

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Venturous Randy

Venturous Randy

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Posted
My gearing in the trike now is giving me a reading of 3800 at 65. With all the response you guys have given me I am now sure the 3.27 rear gear is too low and my plans of changing up to a 3.08 is the right choice. Thanks for all the replies.

 

The change will also help my fuel mileage. Thanks again!

 

I tend to disagree with you. The 3.27 gear is slightly higher that the stock 3.30 and if you go to a 3.08 gear you may have to drive with slighty more throttle to maintain the same speed and I can not imagine that the trike set up it not a lot more drag on the whole system. These engines were designed to run at a little more RPM's and you may not gain any gas milage improvement by lowering the operating RPM's.

I believe your thinking is that with a taller gear, you will cover more ground with less RPM's, but you may end up using more throttle to do it. And, as far as your RPM reading on your tach, these things are pretty good but I would not bet that they are spot on.

Just out of curosity, what is the difference in the height of the tires with the trike set up compared to the standard rear tire?

RandyA

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Squeeze

Squeeze

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My gearing in the trike now is giving me a reading of 3800 at 65. With all the response you guys have given me I am now sure the 3.27 rear gear is too low and my plans of changing up to a 3.08 is the right choice. Thanks for all the replies.

 

The change will also help my fuel mileage. Thanks again!

 

Sounds pretty spot on for me.

 

As Randy said, a taller Gear will hurt Fuel Consumption.

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vicco27

vicco27

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Not trying to create an argument but the higher the gear number ie 4.56:1 the higher the engine RPMs. Example we once had a 1962 Dodge Dart that we drove back an forth to the drag races, it had a 3.23:1 ring and pinion gear set in it, but wouldn't launch off the line, so I decided to cut a fat hog and put a 4.56:1 gear (third member) in the car at the track, the idea worked great and we won the race but when we got ready to come home 100 + miles the engine was turning way too many RPMs to drive that far on the highway @ 70 mph. We had to rent a lift in town so we could change the third member back to the 3.23:1. (we had to have more gear lube anyway). Thanks

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Condor

Condor

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Not trying to create an argument but the higher the gear number ie 4.56:1 the higher the engine RPMs. Example we once had a 1962 Dodge Dart that we drove back an forth to the drag races, it had a 3.23:1 ring and pinion gear set in it, but wouldn't launch off the line, so I decided to cut a fat hog and put a 4.56:1 gear (third member) in the car at the track, the idea worked great and we won the race but when we got ready to come home 100 + miles the engine was turning way too many RPMs to drive that far on the highway @ 70 mph. We had to rent a lift in town so we could change the third member back to the 3.23:1. (we had to have more gear lube anyway). Thanks

 

You're trying to compare apples to oranges. The Venture engine runs better and get's better fuel milage staying in a lower gear and turning higher RPM's. The only thing 5th will do for you is get you there quicker over the long haul on the slab at 80+mph, but it sucks gas doing it....

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skydoc_17

skydoc_17

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Hey Vic,

Nice trike by the way! You are absolutely correct, if you lower the gear ratio on the rear end of your trike, you will in fact lower the RPM that your engine cruises at. The point that the other members are trying to make is if you lower the RPM on your engine down closer to the 3000 RPM range, you have actually moved the cruising RPM of this engine out of the "sweet spot", or power band for this engine. At that point, you would have two options, you can drive around in 4th gear most of the time, (creates poor gas mileage) or you could "Lug Around" in 5th gear most of the time. (creates poor gas mileage) I have an 87'VR First Gen. and run the FJR1300 Final Drive, and at 70 MPH, I am at 4400 RPMS. If I want to pass a vehicle, I just roll on the throttle. No need to down shift. I usually get between 45 and 51 MPG 1 up, unloaded, as long as I stay out of the throttle, and don't engage the VBOOST. With the 300 lbs. of extra weight you have added to your bike to trike it, and 4th and 5th gears being virtually overdriven in the Second Gen's. tranny, that 3.27 gear ratio is looking pretty good to me. I think you would be disappointed if you put a taller gear in the rear end of your trike. But the bottom line is, it is your bike, if you have an extra $500.00 to throw at this project, by all means, have at it. Keep us posted as to what you find out.:thumbsup2:

Earl

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vicco27

vicco27

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@skydoc_17: The additional trike weight is 520 lbs, I already know if I run at 70 mph my rpm is at 4000 + or -, I also know that I am losing 1 to 3 mpg from 3800 rpms and above. Thanks.

@Keith R: Thanks I have the same chart.

@DragonRider: 3500 at 70. Thanks

@Bill Kroger: 3500 at 70. Thanks

@Snaggletooth: 3500 at 70. Thanks

@Dave 77459: I use 5 th gear 65, above 65 and our fuel milage goes down to many rpms. Thanks

@Lonestarmedic: 3800 at 70. Thanks

@Twigg: A ballpark rpm number was all I wanted. Thanks

@Venturous: I'm a trained profesional that had a brain fart, when in doubt ask vicco27 for help. Thanks

@Squeeze: It's not spot on higher rpms hurt our gas milage. Thanks

@Condor: Refer to Squeeze. Thanks

 

Thanks to all of you for your help!!!

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Dave77459

Dave77459

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@Dave 77459: I use 5 th gear 65, above 65 and our fuel milage goes down to many rpms. Thanks

 

The reason I asked is that I assumed there was a correlation between RPM and fuel economy. It still puzzles me, but I get better fuel economy at 70mph in 4th gear than I do in 5th. Above 75, 5th is the right gear, but if I am doing 75, my fuel economy is falling into a black hole anyways.

 

I have more power in 4th gear at 70mph than 5th, so I am just barely puzzled. But still, I am. LOL

 

I just wondered if that were true for more than just me, but if everyone runs in 5th, then my bike must be special. Not that I doubted it.... :)

 

Dave

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Condor

Condor

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The reason I asked is that I assumed there was a correlation between RPM and fuel economy. It still puzzles me, but I get better fuel economy at 70mph in 4th gear than I do in 5th. Above 75, 5th is the right gear, but if I am doing 75, my fuel economy is falling into a black hole anyways.

 

I have more power in 4th gear at 70mph than 5th, so I am just barely puzzled. But still, I am. LOL

 

I just wondered if that were true for more than just me, but if everyone runs in 5th, then my bike must be special. Not that I doubted it.... :)

 

Dave

 

These engines love high RPM's. First and second gens alike. Lug them down and they'll suck gas like a horse eating oats.... Probably the best fuel economy you'll get is riding in the mountain twisties and using 2-3-4th, and very little 4th. You'll get +10 mpg. Seems weird but it happens....

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Venturous Randy

Venturous Randy

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Posted (edited)

The RSTD has a higher 5th gear than the RSV and both are higher than the 1st gen. This is one of the reasons the RSTD seems to be under powered if not revved up more. The RSTD really does need the FJR or V-Max rearend which also helps the RSV.

When considering gas mileage and RPM's, if you are running in 5th gear and without changing the throttle setting while down shifting to 4th, if the bike increases in speed, then you would have to decrease the throttle to maintain the same speed. Therefore, you should get better mileage at that RPM and terrain in 4th than 5th. Conversely, if you shifted from 5th back to 4th and had to increase the throttle setting to maintain the same speed, then 5th should give you better gas mileage.

As a comparison, 5th gear is as follows; RSTD is .750, RSV is .786 and 1st gen is .906. Also, 4th gear on a RSTD is .906, RSV is .960 and a 1st gen is 1.068. Therefore with the same stock rearend with a 3.30 ratio, 4th gear on a RSTD and 5th gear on a 1st gen would run the same RPM at the same speed. Keep in mind that the higher the numerical reading the lower the ratio with higher RPM's.

This can get confusing when using the terms higher, lower and taller. General consensous is the example with a car. If it has a 3.30 rearend, it would be higher or taller geared than a car with a 4.11 rearend, which would be considered to be lower geared even though the numerical number is higher. The 4.11 rearend will be approximately 20% higher RPM's at the same speed as the 3.30 rearend.

RandyA

Edited by Venturous Randy
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Rosie1965

Rosie1965

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Posted (edited)

Vicco, cheap way to experiment and fine tune would be tires. I'm sure with your trike you have all kinds of options. By the way, my VR runs 3500 rpm @ 65. Reason being the previous owner installed a 150/80-16 on the rear.

Edited by Rosie1965
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Billkroeger

Billkroeger

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Ok, So I get this straight , it is better to run 4th at 70 then 5th ???? I plan on riding this top work to save fuel $ and if 4th is better then 5th please let me know.

 

I normaly shift when RPM's get 3000 is this to early gas milage wise ? BTW, I love this site !

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