Why isn't is possible to.......

[APersondek]

Why isn't it possible to.......

Hello,



I have a 6 spd w/ 3. 73 (see sig below) I am wondering why it is possible to turn up to 3500 RPM when in 5th gear (direct 1 to 1) or in any other gear, but can only turn 3200 RPM in 6th gear (. 75 to 1)? Is there not enough fuel for the engine to turn 3500 RPM in 6th gear? what is the limiting factor that comes into play here?



Is the ECM limiting the engine to 3200 RPM? How does the ECM know that I shifted into 6th? I know the ECM talks to the slush boxes, but did not know if could talk to the 6spd?



Point of this post..... I think if I could turn 3500 RPM in 6th gear (for short burst/time) I should be able to hit 120 mph (and use all of the speedo, instead of just up to the 110 MPH mark) similar to the slush boxes with their . 72 to 1 ratio.



Thoughts? Opinions? Comments?





***insert disclaimer here ----> having been born and raised in the Motorcity, I find certain opportunities to be able to operate safely if only for a short period of time on local highways and interstates. (Mostly late at night w/ less traffic on the road) I do NOT recommend operating your truck like I do mine, unless you are willing to pay to play (I have not been caught yet…. hehe…. . nor do I plan on getting caught anytime soon).



Apologies in advance if you think this post is not worth the time it took to read it.

 

[Apence]

mine only goes to 3200 in all gears

 

[APersondek]

Apence,



Do you have a 4. 10 or 3. 73?

 

[Big_Daddy_T]

My old 215 horse would top out at 107 because it ran out of gumption. It still had some gear left. So I got a drag comp and solved the problem. At 3200 it is defueling. It is past peak hp and you are on the decline of torque. 110 is as fast as that brick will go unless you can get it to fuel up to 3500 like a drag comp does.

 

[ndennis]

Apersondek,

The 3rd Generation Cabs are about 5" taller than the 2nd Generations and I have to wonder how much more horsepower it takes to push a 3G down the road than say a 2G rig in the same configuration.

N Dennis

 

[KLockliear]

At 510hp/1052tq, my 01. 5 goes to the governor in 6th with 3. 54's and 33" tires as 117mph (on GPS). Hits that rpm and falls on it's nose, drops off about 4 mph and surges back to 117. I definitely need at least one more gear.

 

[Evan A. Beck]

Originally posted by KLockliear

117mph...

Not on public roads, right? LMAO...



My '01 does the same thing... But that will change soon. Need more RPM and no electronics.

 

[APersondek]

I think I know how the ECM knows to govern it @ 3200 RPM... . It detects ground speed from the speedo? it does not know what gear its in... . it just knows it going above a certain mph... probably 83 MPH and then it defuels accordingly?

 

[nickleinonen]

defueling is right. if i run through the gears quickly the engine usually will tach near 3500rpm in the low gears if i am not quite quick enough to shift... but at the high gears end, the engine speed isn't increaseing as quickly as in 2-3 so the engine can set the defuel rate better [i think it is the same rate, but just has more time to make it work]

 

[KLockliear]

Originally posted by Evan A. Beck

Not on public roads, right? LMAO...

NEVER! Have you heard of the Silver State Classic Challenge? Nice to have the road to yourself with NO speed limit. And wave to the Sheriff as you pass.

 

[MCummings]

There are several RPM governers in teh ECM.



USUALLY it's 3,200RPM full load govener, and 3,500 no load govener. .



Of course, be cause of the bigger resitance in OD, you will have a higher load, and the ECM will go to the "Full Load" govener.



Merrick

 

[banshee]

Or you're hitting the top speed limiter, which is 108 I believe.



John

 

[Udaloy]

I have a question about the speed limitation. What is it supposed to be set at? I know you drag racers know, as they sell boxes to override it. With my '02, auto, 3. 55's and 35'' tires, I was able to do 105 mph at around 2400-2500 rpm. I ran out of road to see where it would have stopped me.

 

[banshee]

Udaloy,



On the 2nd gens it was right at 118MPH. I have heard from others that it is around 108-110MPH on the new models. With my 315s my speedo has been as high as 107-108, but add the extra 10-11% on top of that from the tire size. The 2nd gens was as simple as clipping a wire, but I'm not sure on the 3rd gens yet.

 

[DPelletier]

NDennis,

The 3rd gen may be 3" taller, but it is way more aerodynamic. I doubt very much that it takes more hp to push a 3rd gen than a 2nd gen. Probably the other way around.



Dave