I've asked this before...but

[Foxfan88]

what causes a car to really slow down at higher rpms???

I posted a topic a while back and i tried finding it but its gone.

When my car gets to around 70-80 it starts getting sluggish, i mean it just loses it power it seems like. One time it took A WHILE to get to 110, and when i was there the motor felt like it was missing or something, felt like the motor was weaker than a toothpick....

I am hoping if i rebuild my motor it will help it....

 

[Dbeck002]

If cars never slowed down as they went into the higher gears, then all cars would theoretically have an infinate top speed with higher numerical value tranny ratios (i.e shifting into 5th, 6th, 7th)

But because there is air resistance, rolling resistance, mechanical resistance etc... the car will eventually stop accelerating and all of the force exerted by the engine is to overcome the resistances as you go faster and faster and eventually, you will stop accelerating and there will reach an equilibrium. Thats why there is no 7th, 8th ,9th gear because most engines are not powerful enough to sustain acceleration past ~160 mph... Hope this helps..

 

[mondos90lx]

and 2:73s might have somthing to do with the sluggish feeling

 

[IntenseBlue]

It's not the gears.

 

[04sleeper]

First check all your regular tune up items and make sure they are up to par. Also make sure your timing is set correctly.

Do you still have a stock fuel pump? When was the last time you changed your fuel filter?

All these thing could contribute to what you are describing.

 

[jeffs89gt]

If cars never slowed down as they went into the higher gears, then all cars would theoretically have an infinate top speed with higher numerical value tranny ratios (i.e shifting into 5th, 6th, 7th)

But because there is air resistance, rolling resistance, mechanical resistance etc... the car will eventually stop accelerating and all of the force exerted by the engine is to overcome the resistances as you go faster and faster and eventually, you will stop accelerating and there will reach an equilibrium. Thats why there is no 7th, 8th ,9th gear because most engines are not powerful enough to sustain acceleration past ~160 mph... Hope this helps..

that remindedme of somethin i saw on tv a lil while back. there was a show about setting land speed records in the salt flats and they had a guy with a bike doin like around 300 mph and the bike was pickin up speed and then all of a suden the back wheel started to brake loose and the rpms jumped up, becasue thats when the arodynamics part kicked in, and there was more speed left in the bike, but the resistance was to much. it was cool to watch but probly scared the person on the bike half to death....

 

[Euphoric306]

lower numerical gears would actually help him acheive higher top speed,

foxfan, didnt u have a missing problem too

whatevers causing that could be the reason ur feeling sluggish at higher speeds


scratch that, id be willing to bet my life (savings) on it,... hehe


(i dont save money by the way)

 

[Redfire 05]

I'm betting that wind resistance is most of the problem. I used to own a pretty fast buick grand national. It had 350 to 400 hp, but it was a buick regal. I could hit 110 realy fast, but those brick-like aerodynamics kicked in and it took a lot of time to get it going faster. I never topped out in it because I couldn't find a straight away that had enough room to push it that far (at least not where I could see if the cops were somewhere ahead). If you are still running 16.8's (from your signature) then you don't have the power to defeat the wind. Bump up the power and you'll go faster, but fox stangs aren't them most aerodynamic car out there, so wind resistance will always be a factor. With more power you just won't notice it until you are going faster.

 

[Foxfan88]

i am just guessing its missing, i know something isnt right.

Because my friends v6 camry with a 5 spd got to like 125 WAY faster than my mustang gets to 110. Plus i went for a ride in my cousin's friend mustang back a long time ago, it was modified but nothing too radical, i remembered it got to 80 like it was nothing.

I have changed fuel filter, i have changed cap and rotor, and plugs. Getting ready to change o2 sensors.

My motor sounds all fine up until around 4000rpm then it has the strange ROAR!

In first gear it get to 4000 and then it kind of loses its pull (doesnt really you can just tell all that power doesnt sound like its getting to the ground, hard to explain), then at 4500 it shifts.

In second it pulls decent up until around 4k and then it starts losing its pull, with this ROAR! this roar sounds like the motor is WORKING REALLY hard but not doing much of anything.....

I think whatever it is it may be contributing to my poor times.

Maybe someone could make a small vid or link me to a vid of a close to stock mustang interior clip, of the car flooring it through the gears whie showing the guages, so i can compare mine.

 

[Redfire 05]

By the way, even if you have an AOD car (like mine) you should be running faster than 16.8 @ 85 mph. Unless your AOD or your engine has some serious issues. Your in Oklahoma right (again from the sig) I would think that your trap speed should be in the low to mid 90's at your elevation.

 

[Foxfan88]

Yeah and here is a small thing, when i hit the finish line, i trapped 84.75 MPH but when i looked at my speedo while crossing the line, it was at like 75 mph, so i dont know....

 

[Foxfan88]

Plus its not like i get to 110 and then it starts slowing, the car starts getting sluggish at like 70 and then say going from 100 to 110 is like OMG takes FOREVER!

But when i changed cap/rotor/plugs/wires it seemed a tad bit better early on in second gear, the car's shift was smooter it seemed like.

 

[Redfire 05]

Yeah and here is a small thing, when i hit the finish line, i trapped 84.75 MPH but when i looked at my speedo while crossing the line, it was at like 75 mph, so i dont know....

That could be because your speedo isn't working or because you have the wrong speedo gear in the tranny.

 

[Foxfan88]

it moves pretty good, it boucnes sometimes in the lower speeds.

 

[Euphoric306]

yea dude, if u trapped 84 but only saw a speedo of 75, thats a clear indication that maybe u werent going from 100-110, maybe from like 120-135 or 140, which naturally would take a lot longer than 100-110


...just like it takes longer to get from 50-90 than it does to get from 10-50, see the picture?

 

[Foxfan88]

ahh i see maybe that the problem???
Well the AOD isnt the original tranny so i dont know.

Maybe this AOD has a 3.08 speedo gear??

What rearend gear does it sound like my tranny is set at???

ALSO how fast is a stock 5.0 going at around 4k rpms in last gear??

CORRECTION, not last gear, in Drive

 

[Foxfan88]

If i posted my mph at a certain RPM would this help. because i know i have 2.73 so maybe something wont make sense....

 

[Synned]

Maybe your converter is slipping in the higher RPM range? Does that make sense? Thats why your motor is revving but you aren't really going anywhere?

 

[Foxfan88]

OK my speedo says 65 MPH and i am pulling 1600 rpm in OD

 

[Euphoric306]

i would definitely get the right speedo gear and then check us up again, theyre like 15-20 bucks i think