top speed limits

[rb77413]

Hey all. I did a top speed run (almost). Now I can feel the wind resistance at that speed, had the tailgate up and no tonneau cover. I lifted just under 110. What was the speed limit again. Its a 99 SLT 5.2. Another thing, it downshifted out of OD and stayed in fourth. If I would have stayed in it would it have eventually gone into OD? was pushing just about 5K rpm's. Or is there something that prevents it from shifting into OD when it is floored? If so would a shift kit help this problem?

Bob

[Walkercolt]

Bob you're looking at two different things here. The speed limiter should cut fuel at about 108-110 MPH stock for the "S" rated tires. The reason you were in third gear is when that 66%OD kicks in, your RPM's(and HP) would drop so much there wouldn't be enough HP to punch a hole in the air at 110 MPH. Figured another way, let's say it takes 150 rear wheel HP to push a Dakota 110 MPH. This means the engine must be very close to maximum output, which with a 5.2 occurs about 4400RPM. Without the speed limiter, a 5.2L Dakota would never pull the 150 MPH that 4400RPM in OD, because that would take close to 270 rear wheel HP.Air resistance is the enemy.To double your speed, it takes the SQUARE of the horsepower. I did study this in physics, but a good friend is an aero-enginner for American Airlines.A dirty airliner can be 20 MPH slower than if it's just been washed.Dodge and Cummings WLSR truck develops over 550HP, 900 ft/lbs. to push a Ram 200MPH.

[inflammable]

that makes sense about the air resistance. which means i wont get the 140mph i should get at 5000rpm in 4th. but all that does interest me, is there a particular part of physics i should look at, cause i know if i go looking for a 'physics' book it wont be as specific as i'd like.

[tobs440]

well then walkercolt,
how come i can do a 120-125 in od at 4200 rpms??? i will have to find the picture but dodge boy has seen it......i love busting your bawls sometimes...... i dont know anything about physics....

[TBIAgent69]

I've gotten my 4 cyl up to 125, but that was down a pretty steep hill

[UserName]

Originally posted by tobs440
well then walkercolt,
how come i can do a 120-125 in od at 4200 rpms??? i will have to find the picture but dodge boy has seen it......i love busting your bawls sometimes...... i dont know anything about physics....

Walkercolt is absolutely correct. On a macro scale the drag due to air resistance alone increases with the square of velocity. There are other factors that play into total vehicle drag but what he said is true.

So.... that means your Dakota is set up different then the other guy's Dakota. Otherwise it would do nearly the same thing. Physical phenomena don't change just for you.

i dont know anything about physics....

You didn't need to tell us that... it's obvious. By the way, you keep running your tranny hard in overdrive an you'll soon be looking for a new tranny.

[BlkBird]

So do all the trolls come out this time of year or what?! Damn!

Anyway, Ive been up to 130 so what's my RWHP(and I dont know what gear the tranny was in at the time)? It was very scary even lowered 4" Dakotas just are'nt top end fliers, then again I did get spoiled by my T/A it was comfortable to 150.

[00DakExCab]

you guys make me sick. I got a 2000 dak with the 4.7 V8 and mine shuts down at 99. Anyone know a way to defeat the speed limiter without buying the new pcm? Also if anyone knows any specifics on how it works I am an electronics guy and I am pretty sure I could figure out to defeat it if I knew more about how it works. Any input greatly appreciated.

[tobs440]

well just to let you know i was taping the brake and keeping it out of lock up...... and for 185,000 miles my tranny looks pretty darn good inside..... what does running a tranny hard have to do with physics?????

[Jon_Smith]

whatchoo scared about blkbrd? Had mine to 135 ridin high on 31" mud tires... talk about tire noise.... FWIW, ~260rwhp

[Duner]

My little 4.7 has seen 150 for a short burst on a deserted road. My guess is that it would probably run up to 165 or so. Not that I'm really THAT interested in checking. It went 136.1 mph when it was NA (242 rwhp, 322 ft-lbs rwtq).... according to both the tach and a moving map GPS device I was using. It did take it a while to get there though. Now it hits that 150 mark very quickly. The truck felt very stable and not floaty or spooky at all.

On paper.... how fast should it be able to go? The performance calculators are saying that the truck is making somewhere in the 450 hp range - based upon ET and mph at the track.

[UserName]

Originally posted by tobs440
well just to let you know i was taping the brake and keeping it out of lock up...... and for 185,000 miles my tranny looks pretty darn good inside..... what does running a tranny hard have to do with physics?????

The present condition of your tranny does not make you exempt from rapid wear due to abuse. If anything it makes you more susceptible. It's like saying, "My engine has 200,000 miles on it. It's obviously strong enough for a 400 Hp nitrous shot." The longevity of your tranny is due to good care and maintenance. The strength of your tranny is an entirely separate issue.

[Walkercolt]

Tobbs, your 410 gears are doing just what you bought them for. Putting your engine at peak power at the ground speed you wanted! Inflammable, if you look under "air resistance" or "drag,(aerodynamic)" you should find your info.And User Name , Tobbs and me get on fine!He just has to give me a hard time. Duner, a 4.7L NA running 150????On what blend of nitro????If you can really go that fast stock, I'll pay the fees to take your truck to Bonneville this spring for an LSR attempt for "D" class, truck. No Kidding. I know the people and have the money. I drove a "G" class Lake tank(200cid limit named for the guys who used WWII fighter drop tanks for bodies) and held the record for nearly 8 months in the early '70's using a tiny Meyer-Drake V-8(old Indy car motor)@168 and change in a 1400lb car.If the salt's bad, we can go to Nevada....

[Duner]

Walkercolt.... I think you mis-read my post. It went 136.1 mph top speed when it was NA. That was WITHOUT the turbo, but it did have a handful of mods done to it. Mainly the custom PCM, ported TB and full 3" exhaust.

Now that it's turbo'd it goes much faster.

What kind of safety requirements do they have for a run at Bonneville or Nevada? I still think I could get to 165 just the way it sits right now. I'd imagine they'd want me to install a full cage for anything like that.

[SwollHottie]

Originally posted by TBIAgent69
I've gotten my 4 cyl up to 125, but that was down a pretty steep hill

I've done about 115 on a straightaway in my 2.5L, but I ran outta room.

[Walkercolt]

Duner I didn't misread it. I think the LSR for a sub 300cid pick-up is 128mph. That was a '67 Chevy 283 Hi-Performance engine and a 4-speed and I think a 2.73:1 axle(maybe a 2.55). If you're stock, you're stock. You just wear a helmet and a Nomex suit and shoes.You make a run one way, and with-in 30 minutes make a run the other way that must be with-in 10% of your 1st run. On trucks they'll allow stiffer springs and I think 2" lowering, I can check the rule-book, I don't have the current one.You run narrow ribbed tires pumped up to about 70PSI to cut rolling resistance.Traction on salt isn't a problem...it has about 4 times the traction as asphalt...but at speed it is ROUGH.The Dodge/Cummins Re-build center effort killed the Mercedes-Benz diesel LSR of about 185 in a tiny 3L turbo-diesel streamliner with a pick-up truck....I still think that's why the Germans bought Chrysler!

[Duner]

I sure wish we would have had this conversation a couple of months ago! That sounds like a lot of fun! And you know this Dakota is more aero than a 67 chevy! They might have considered my truck stock before..... I'm sure they have no way of checking the PCM for it's code. With my 3.92 gears in 5th, 136 mph was only like 4500 rpms. Although I did have a ram-air box installed.... although it got nearly exploded from all the pressure generated on the drive.

I doubt they would consider it stock now! hehehe When you open the hood, the turbo just about jumps out at you. The truck now has the feel of a 250cc 2-stroke engine. When it gets into boost - it's "on the pipe". It pulls very hard to about 5500 rpms in whatever gear you are in. It actually feels like it pulls harder in 5th than it does in 2nd or 3rd. 4th gear feels the best!

So a helmet and driving suit would get me down the track? WooHoo. It sounds like I might have to take a trip to the salt! Thanks for the idea!

[Kevin_Rants]

I've been 130 mph on Autobahn 6 leaving Kaiserslautern, Germany.....doooh, that was a in a BMW 328i, sorry. Want to know scary, ride in a lifted CJ-6 Scrambler with mud tires going 65 mph. NO wonder they had grab handles.

I did go 75 once in my Durango though!!!! Killed a few bugs, no tranny wear, lots of CO2 into the atmosphere, lots of gas used.

Sorry, you all are doing the "my dad is bigger than your dad" thing, thought I would get my smart a$$ comment out for the day.

[UserName]

My Dakota is slow. Pure and simple. But I did wipe out a pheasant once at 65 mph. I didn't have signs of tranny problems either. But my paint has a few nicks in it now from beaks and talons.

[Coolva]

I've hit just over 140MPH in mine... I have 3.55 gears, and had some 325/50/15's on the stock rims (slicks) racing a mod'd LT1 F-Body

I didnt know how fast we were going untill I found out from the F-Body That was fun... heheh My truck often sees 100+ on back roads in the country, it takes no time to get there

[TBIAgent69]

Originally posted by Kevin_Rants
I've been 130 mph on Autobahn 6 leaving Kaiserslautern, Germany.....doooh, that was a in a BMW 328i, sorry. Want to know scary, ride in a lifted CJ-6 Scrambler with mud tires going 65 mph. NO wonder they had grab handles.

I did go 75 once in my Durango though!!!! Killed a few bugs, no tranny wear, lots of CO2 into the atmosphere, lots of gas used.

Sorry, you all are doing the "my dad is bigger than your dad" thing, thought I would get my smart a$$ comment out for the day.

What's wrong with you? People who drive that slow should have their own road, not just a slow lane.

[inflammable]

i must be in the wrong group altogether. i dont cruise much above 75 or so cause of gas mileage.

but i do take it up occasionally. when it was still reading in kilometers (spent its first two years in canada) the first time i went to test it , it shut off at an indicated 105 mph. so, whats that, 160-180 kph???

but after it was shifted over to miles, it hasnt shut off yet. even bounced it off 110-115 or so.

[Walkercolt]

Kevin, I have deceptive speed....I'm slower than I look. Some people say I'm slower than my own shadow, but I think they're exagerrating Hey, when I'm towing my travel trailer, I feel like a snail. But like the snail, I'm taking my house with me I'm thinking about putting a BIG "S" on the side of my truck when I'm towing...that way everyone can look at me and say "Look at that "S"-car-go!"

[Jon_Smith]

EEEEWWWWWWWWWWWW!!!!!!!!!! BAAAAAAAADDDD BAAAAADDDDDDDDDDDDDD BAAAAAAAAAAAAAAAD joke badbadbadbadbadbadbad

[Lesley]

I had my Dak up to 160 km/hr. today on a stretch of fairly deserted toll highway. I don't think it could go much faster, if at all.

[tobs440]

omg my cheeks are red and i cant stop laughing........

[Lesley]

What... at me? You couldn't be laughing that hard at that joke....

[tobs440]

i was laughing at walkercolt..... see that s car go....
but shit you can get you sixer faster then 90-95 with out a prob... exp with the intake and exhaust shoot i have had mine on a reg basis on the hwy doing 95-100 driving back and forth from fla to massatwoshits.... and i still averaged about 4 hours to a tank.. of corse my speedo cable was broke !!!!

[dodgeboy93]

yea....no problem having 6'ers up to high speeds, had the 93 up to 115 in 4th gear but ran outta room so I couldnt grab 5th.

[Lesley]

Mine didn't want to go any faster than 110. I'm in Canada and I've heard that is what the limiters are set at here... true? I should have a V8 TB & headers on before the end of the month, will the limiter restrict it from going faster with those on?