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More Top End Speed Wanted
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KCinKC
Reg. Apr 2010
Posted 2010-06-08 10:23 AM (#4985)
Subject: More Top End Speed Wanted





Posts: 15

I currently have a FL70 with a Cat 3126 (250 HP) engine, a Fuller 6-speed manual transmission, and 4.63 gears. At 2200-2300 rpm's it tops out at 63-64 MPH. I'm looking for ideas on the best way to get more top end speed at the same or lower rpm's.

Would it be to change the rear end ratio? Different transmisson setup ? Other ?

Thanks
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hogtownboss
Reg. Jan 2009
Posted 2010-06-08 4:21 PM (#4986 - in reply to #4985)
Subject: RE: More Top End Speed Wanted





Posts: 176

KCinKC - 2010-06-08 10:23 AM

I currently have a FL70 with a Cat 3126 (250 HP) engine, a Fuller 6-speed manual transmission, and 4.63 gears. At 2200-2300 rpm's it tops out at 63-64 MPH. I'm looking for ideas on the best way to get more top end speed at the same or lower rpm's.

Would it be to change the rear end ratio? Different transmisson setup ? Other ?

Thanks



There is a couple of things you could do. Change your tire sizes, change the gears to something like a 4.10 or buy a programmer which you could adjust you speed limiter.
The tire change will not do much for you. In my opinion I would try the programmer before I would mess with the rearend and should be cheaper also. I think TS PERFORMANCE has a programmer or a module that works on the small Cats really well and also increases the fuel mileage too.
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blacktruck
Reg. Jun 2010
Posted 2010-06-09 5:09 AM (#4988 - in reply to #4985)
Subject: RE: More Top End Speed Wanted





Posts: 2

Look at the numbers you are mentioning here. A programmer will not help you out. You might get more speed but you will pay for it in fuel and shorten the life of your engine. It also will not change the final drive ratio between the engine and rear end. You're turning your engine as fast as it should be going down the road. If you want to go faster you will need to change your gearing between the engine and rear end. Tires will only get you a few MPH and you may not want bigger tires. If you put many miles on look at your rear end gear ratio. It is probably not right for what you do. Keep in mind that if you gear for more speed you will lose some in power to pull the hills. You don't have an abundance of torque like a big truck to play with. Be cautious about how much you change the gearing. If you want to slow the engine down you will either change your rear ratio or your transmission. Used trans or rears can be had fairly easily. Check the salvage yards. Either is about the same work to change.
Ken
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KCinKC
Reg. Apr 2010
Posted 2010-06-09 9:46 AM (#4989 - in reply to #4985)
Subject: RE: More Top End Speed Wanted





Posts: 15

I would agree Ken, I don't think a programmer would be the way to go. From what little digging I've been able to do so far, it appears there are several diffent gear options for that readend. Three of those options would be 3.73, 4.11, and 4.33. Is there a formula I can use to determine MPH increase with each of those ratios ? For example, I could expect X % increase in MPH going from 4.63 to 4.33, Y % increase going to 4.11, and Z% increase in MPH going to 3.73 gears.

Since you mention a transmission swapout to be about the same work, what would be a good transmission reccomendation ? It has the Fuller FSO-8406A (6 speed) currently.

My goal for any changes is to run 70mph at 2000rpm ideally. Thanks for everyone's input.

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windy
Reg. Oct 2004
Posted 2010-06-09 12:42 PM (#4990 - in reply to #4989)
Subject: RE: More Top End Speed Wanted






Location: Colorado
KCinKC - 2010-06-09 8:46 AM I would agree Ken, I don't think a programmer would be the way to go. From what little digging I've been able to do so far, it appears there are several diffent gear options for that readend. Three of those options would be 3.73, 4.11, and 4.33. Is there a formula I can use to determine MPH increase with each of those ratios ? For example, I could expect X % increase in MPH going from 4.63 to 4.33, Y % increase going to 4.11, and Z% increase in MPH going to 3.73 gears. Since you mention a transmission swapout to be about the same work, what would be a good transmission reccomendation ? It has the Fuller FSO-8406A (6 speed) currently. My goal for any changes is to run 70mph at 2000rpm ideally. Thanks for everyone's input.

Roadranger has a website with a roadspeed calculator. Try this link and see if it will work for you. http://www.roadranger.com/Roadranger/index.htm  Look under the "tools you can use" tab for road speed calculator.
Your transmission has a .78 overdrive. Are you running 22.5 or 19.5 tires? If you're running 22.5 low pro tires, it looks like 4.11 gears would do what you want. Also, depending on how "creative" you want to get, you could look into an aux transmission giving you , in effect, a double overdrive. If it were me, I think I would probably just change the rear end ratio. This equation will work for figuring out road speed too, but you have to know the revs per mile of the tires you have.

The theoretical top road speed for that ratio can be calculated using the following equation:
Engine RPM x 60 / (Axle Ratio x Tire Revolutions per Mile x Transmission Ratio) = Top Road Speed (MPH)
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KCinKC
Reg. Apr 2010
Posted 2010-06-09 2:44 PM (#4991 - in reply to #4985)
Subject: RE: More Top End Speed Wanted





Posts: 15

Windy - that roadspeed calculator is a great tool ! I'm not 100% sure the size of my tires other than I know they are 22.5's. I would guess them to be 255/70R22.5 based on the info the roadspeed calculator gave me.

It looks like if I was to go to 11R22.5 tires I would increase my max speed from 64.8 MPH @2200rpm to 73.4 MPH. At 2100rpm I'd be at 70MPH which would be perfect. And those number are with the 4.63 gears.

If I was to go to 4.11 gears and not change tires, I'd have a roadspeed of 73mph at 2200rpm. If I was to go with 11R22.5 tires and 4.11 gears I'd be at 82mph @2200rpm !!

I think I will look into new tires since I was told that I'd probably need them anyway by the time I'm due for another DOT saftey inspection.
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windy
Reg. Oct 2004
Posted 2010-06-09 4:22 PM (#4992 - in reply to #4985)
Subject: RE: More Top End Speed Wanted






Location: Colorado
Glad to be able to help. The tire change, if it's enough for you, would sure be the simplest. Good luck!  
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hogtownboss
Reg. Jan 2009
Posted 2010-06-14 4:24 PM (#4994 - in reply to #4985)
Subject: RE: More Top End Speed Wanted





Posts: 176

An actual programmer will NOT hurt the fuel mileagr at all. Most programmers are set up to adjust the govner and top end speed, so if you make these adjustments to increase your speed not only will you get going faster you will NOT be running the engine agaist the govner therfor you will incresae your fuel mileage.

Working on one for my 98 Kodiac now, will let you know what we come up with, it has the 3116 whick is close to what your is. but mine is an automatic. (talk about SLOW)

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KCinKC
Reg. Apr 2010
Posted 2010-06-15 9:54 AM (#4996 - in reply to #4985)
Subject: RE: More Top End Speed Wanted





Posts: 15

On a related topic in regards to Programmers, has anyone had thier injectors hone and balanced ? I did this on my Powerstroke 7.3L and I was amazed on the HP and MPG increase. Not to mention how much smoother the truck runs as a whole. From my limited experience, this was a much better way to go than a programmer. Anyone else have thoughts? I don't know that I would see the same gains with the Cat engine but I may look at doing it anyway. And I know it won't help with my top end speed or MPH issue but the benefits may still be worth it. Thanks.
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hogtownboss
Reg. Jan 2009
Posted 2010-06-15 1:42 PM (#4997 - in reply to #4985)
Subject: RE: More Top End Speed Wanted





Posts: 176

I have been over at HOLT CAT in Ft.Worth all morning talking with these guys about the 3116 and 3126 engines and how to increase top end speed to get a better running engine.

This is what we came up with, these engines are electreonic controlled engine with rev limiters installed (like the governors on the older engines). So when you increase or raise the limit of the rev limiter you do raise your top speed. This can be done either by getting a CAT daler to reprogram the trucks computer or install some sort of chip or programmer. Just as I said...

This is pretty much the same as doing the older trucks. ie: my 1992 Dodge with the 5.9 Cummins engine, bone stock this truck would run right around 70 and slow. Now with only minor VE injector pump adjustments and 4" exhaust system the top end has been raised to over 80, has more take off power and my fuel mileage went from 17 in town to almost 20. So here is golden poof that these type of adjustment WILL or can increase your fuel mileage as well as your top end speed. Also can be done with electronic engines, my 07.5 Dodge Ram 3500 C/C with the 6.7 engine, 6 speed Aisin auto. The original top speed was 94 and was only getting 12 mpg unloaded and 10 loaded, now with aftermarket tuning and delete kit I can adjust my top speed upto 120 (if wanted) and my fuel mileage has increased to 17 unloaded and avg. 14 or so loaded and no longer have to use my tow/haul mode on the transmission. Although there is NO need to raise the top speed on my truck I am using it as an example of what can be done with electronics when used right!

A big plus to going with a programmer or chip is if you do not like it or want to sale the truck you can remove it. If you change the rear or trans and do not like it you have to spend the money again on labor.
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KCinKC
Reg. Apr 2010
Posted 2010-06-15 4:03 PM (#4998 - in reply to #4985)
Subject: RE: More Top End Speed Wanted





Posts: 15

Thanks Hogtownboss. What is the downside to raising the rev limiter ? I was trying to increase the top end speed while staying within the current engine limitations and settings. But if there is no dowside (and I assume not since CAT provided this reccomendation to you) I may do that. If I had CAT do this instead of a getting a programmer, would this be considered "up rating" the engine? Or is up rating something totally different ?

Did you see my other reply about getting the injectors hone and balanced ? Do you have thoughts on that ? Thanks again


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hogtownboss
Reg. Jan 2009
Posted 2010-06-18 3:28 PM (#5000 - in reply to #4998)
Subject: RE: More Top End Speed Wanted





Posts: 176

KCinKC - 2010-06-15 4:03 PM

Thanks Hogtownboss. What is the downside to raising the rev limiter ? I was trying to increase the top end speed while staying within the current engine limitations and settings. But if there is no dowside (and I assume not since CAT provided this reccomendation to you) I may do that. If I had CAT do this instead of a getting a programmer, would this be considered "up rating" the engine? Or is up rating something totally different ?

Did you see my other reply about getting the injectors hone and balanced ? Do you have thoughts on that ? Thanks again





Only "downside" I could see is if you had other people driving your truck that did not know how to watch gauges and know how to drive they maybe able to hurt something. But we are only talking about going to mid to upper 70's or close to 80. The idea behind this is to drive without having to keep your right foot on the floor the entire trip. My 3116 we just installed a TS module and made a big difference, but since I am way out of warranty I am going to Cat and let them reprogram it and see what that does. Plus I need to get some service work any way before I add too much to it.

Have heard of the injector deal, but too labor involved for me and too much downtime. Now if I was doing a rebuild and had the time I would try it.
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