I was just wondering how fast ya'll have taken the LO3? I've gotten it up to 110 before and she still seemed to pull pretty damn hard, so I was wondering how much further I could push her.

 

ive had mine to 110 also.... i read somewhere that there is a tbi cutoff at 115 but you can modify it.... i think its on the site under tech articles....

 

Not sure how fast it can go. But when you get that SOB up to 110mph it starts rattling like crazy!

 

i have had mine to around 125-130. I think i could go even faster than that, but i dont think ill try.

 

About 120 with 2 passengers in the car and I still had a bit more room on the throttle. I figure I could have got it up to about 130. It was smooth too.

 

No 305 TBI will go past 112 unless you have deleted the speed limiter in the chip. You could also bypass the limiter (via tech article) manually and achieve higher speeds. If your speedo tells you else it is off or you have a different tire or gear size.

 

I've hit the speed limiter as well, and I think there's more room left in her. That was with the stock 2.73's when I did that, so once she got up there, she cruised effortlessly.:hail:

 

Well... no 89+ tbi. If your an owner of an 88 model, there is no speed limiter, which means on a hill with a good stiff breeze to your back, you could probably get it up to around 125.

 

In the manual versions with the 3.08's (which I have) the govenor is set, well at least on mine, at 119mph (varified by multiple cars capable of higher speeds). Not only have I hit it MANY times, but my lil' LO3 is still pulling really hard when I hit it. I wanna get that thing off there sooo bad and have my buddy tail me in his GT so I can see what my real top speed is.

Bruce (90RS305)

 

Your speedo is off or whatever method you used is wrong. The speed limiter is set to 112 mph, which is the speed rating of the tires. If it was set higher there would be potential for major law suits and gm would not do that.

 

hmmm...maybe something is wrong with my computer? I've had my friend in his GT and my other buddy in a lancer pace me and the GT came up 118 and the lancer came up 120. Not saying your wrong, just curious as to why that might be off...

Bruce (90RS305)

 

i dont know how fast i had my car up to i had the needle pinned to the trip odometer so take your measurement from there

 

There is some variance withing 5mph or so. Some are 110 and others are around 120. Tire size and a gears can play into it as well. I know you are stock but chances are your speedo is off just like our tachs are. I have done the speed measureing method as you decribed by riding ext to someone who is at a cetain speed. However, their speedos are off as well. Digital ones aren't off that bad but it is hard to get two cars to go the same speed.

 

Speed governor aside, I know my car has gone at least 120 mph. My wife and I were going down an old country road with me in the lead, and her speedo was at 120 and she couldn’t catch me.

I know her speedo to be true because just the other day I was driving by one of those radars that flashes your speed at you, and it said I was going 44 mph and her speedo said 45.

 

Hers is still most liekly off. The higher you go the more they are off. Pass the same radar thing going 120 and I bet it will say 112 or so. Most speedos out there are really off the higher speeds go.

 

I hit 125 the other night. Cable driven speedo's are suppose to be more inaccurate the higher the speed.

 

ive been up to about 147 before (with TBI measured via rpm, gearing, and tire size so its accurate) it had way more in it but I got Skerrrrrd


top speed isnt all that fun anyways.. acceleration is where its at

 

At 110 I didnt have any vibration at all and i know it has the stock drive shaft. Why is that? The only other noise I had was my little brother screaming at me telling to slow down

 

It depends on the shaft. The steel shaft in my RS never vibrated at all all the way up to the limiter. One the other hand the steel shaft in my 95 will vibrate at 90. It just depends.

 

dunnno what ive had mine up to cause the speedo is unplugged

but she was a floatin and everything on the sides of the road was a blur

 

One of my fondest memories in my car is when I was cruising down the road with my friend and she says "Brian, how fast are we going?" and I replied "I'm not sure, I ran out of speedometer a couple minutes ago."

 

not really sure.. the speedo only reads 120.. she went quite a ways after that

 

i took mine 120+ because i raced a z28 and we both were flyin

 

well i have been clocked at 127 in my 88 k2500 pickup by a buddy of mine that has a gun. that was nuts 6000 pound trucks with 33" mud tires and a plow should not go that fast. but i have a 350 too

 

Unless you have larger tires or deleted the limiter out of the chip your 89 and later 305 TBI car will not go past 112. I promise you. The speedos, just like every other GM one out there, get progressivly less accratue as speeds increase. It is hard to judge speed even if someone is pacing you. I thought I was goin 125 when I was running behind my roomates 02 SS when in fact he was going 135 and I was stuck bouncing off the limiter at 117 (larger tires). Even though the car may seem like it is going the same speed as you chances are it is not and it too has a inaccurate speedo.

 

Just keep goin' until the computer kicks your RPM's down, then you know you've reached the end.

That's what I did in my mother's lumina a few years back. The sad thing is, that it didn't kick in until 120, which means I've gone faster in my mother's lumina than in my camaro.

 

thats y you use win adl or find a cop buddy that is able to bring his radar gun home.

 

..... that would be a deleted limiter right out of my chip

 

in my 89 i was cruising down a backroad and i was testing her out and i got all the way past 120 on the speedo with a friend right in front of me and his car shuts off at 109 on radar and i blew past him leik he was sittin still so must be my limiter is not connected

 

The highest I've had mine is 110, damn thing still had 1000 rpms left before redline.

I rember tryin to top it out and I went over a shallow bump. That was scary, I was suddenly weightless then scrape, float scrape.

 

I can only get mine to about 105-110 (? i have the double sided speedo stock from my 83), but following my buddie in his jetta we both got up to 120. I think it was cuz he was in front of me blocking the wind though, those headlights are just big air pockets trying to slow you down, and the law won't let me put covers on them. I have the stock auto tranny though, with the overdive that kicks off if you push the pedal down past 3/4 of the way, and at that speed if i do, its yellow lined in 3rd, so i don't want my car to go any faster than that.

 

Yes and no, headlight pockets included, the thirdgens still have a pretty good COD. IIRC EVERY thirdgen model has a .35 or lower COD, the formies are the lowest, i beleive .31 or so.

 

Yup. I always use between .35 and .40 when I do nerd stuff with these cars. 4th gens are a bit better.

 

hmmm, i always thought i had seen that the 3rdgens had a lower COD, because of the reduced frontal area. :: shrugs :: it has been a while since i looked at the numbers.

 

the speed limiter for the ANTT cars (like my 91) is set to 114.

you can verify that with a laptop if you want.

ive hit it many many times. including uphill... shes still pulling when it hits.

disconnecting the VSS enables you to exceed the limiter (since the ECM doesnt know its speed) and the code will disappear as soon as its plugged back in and the car moves.

 

They do have a reduced frontal area but it is by no means stream lined. Stream lining a car will produce a much lower COD than frontal area alone.

 

140 mph and they shut off the dyno at 6000 rpms.

 

im not sure about that shifty, the car of choice for stock bodied stuff at the bonneville salt flats is a thirdgen firebird. Fourths have been tried but failed, they tend to fly at like 220... granted that doesnt tell us anything about drag

 

Yea the birds are better than camaros. The salt flat car was not based on drag only. I think they chose that car for a "coolness factor" over high tech aerodynamics.

 

Third gen's have a better drag Co than 4th gens, especially the 91-92 birds. IIRC, they were very close to the vette, if not better.

 

Normally you're a reasonable person, but I gotta do this..


While I'll agree that speedos are rarely accurate, they don't progressively get worse as speed increases.

Do you ever read Motor Trend, or Car & Driver? They clock the cars then post the readings compared to the speedo. The most they're off is 3mph, and they're consistant.

The chart will read like this.
Speedo - Actual
30mph - 27mph
40mph - 37mph
50mph - 47mph
60mph - 57mph

Saying a speedo is off 8 mph at 120 is

Are you in denial that a 305 TBI will actually break 120mph or something?

 

they wont do it unless the speed limiter is eliminated or its an 88


as for motor trend, they test brand new cars with stock size tires and wheels. Theres no telling whats on a 15 year old thirdgen not to mention the fact that alot of thirdgen ownership is 17 year old bull-****ters

 

Speedos are often off by a percentage, so they get worse as the speed gets higher...

 

And your point is???

Mine was removed. I had a Jet Stage II chip for ~2 yrs, and before that day I never knew the speed limiter was gone. It was probably best that way.

Quote:

as for motor trend, they test brand new cars with stock size tires and wheels. Theres no telling whats on a 15 year old thirdgen not to mention the fact that alot of thirdgen ownership is 17 year old bull-****ters

That's all true, but that doesn't mean the speedo becomes more incorrect as speed increases.

It's a gear driven device. Regardless if the actual speedo is electric or not, the signal is still taken from the mechanical movement of the speedometer gear. The gear ratio does not change as speed increases.

 

Even though our speedos are gear drive they still rpoduce an electric signal and are not gear driven in the unit itself. It is half mechaical and half electrical. Therefore there is some error and it does not read 1:1. New car speedos are far more accurate since they are completely electric and are calibrated much better accroding to various engine parameters. A 305 TBI can go 120 without the limiter. In fact I am sure one can go to 130 in stock form if there is a stiff tail wind and downhill grade. I say they can't because of the limiter and not because of their lack of power. Pablo is 100% correct that our speedos get farther and farther off as speed increases. There is a lot of confusion goin on in here. You can put a 450hp minirammed 355 in your car but if the limiter is set at 112 the car will not go past that no matter how much power it makes. These cars always feel like they are going faster because you use so much road up to get to 110. These things do not pull up top. My daily driven 2.4L grand am pulls harder than a stock LO3 up top.

 

Id really have to see a bone stock LO3 hit 120+ mph. With a fresh tuneup my car bone stock was dead at 112 or 114, I barely hit the limiter.

Its quite a different story now.

 

chuck, i hit 130 on the front stretch of PIR.

 

it is BECAUSE its a gear driven device that its off.. example:


i dont know the exact numbers, but you only have somthing like 5-7 drive and 5-7 driven gears to chose from (possibly less on the drive)

so you pick whatever is closest. so the RATIO is off ever so slightly....

this slight ratio diff makes only .01 mph diff at 10mph, but as you go faster, the ratio stays constant..... constantly off that is... so because its a ratio, it goes farther off depending on the speed so by the time you hit 50, its off by 2mph, and when you hit 150 its off by 12.... ect... (this can be expressed as a percent)




but how does this explain Motor Trend, or Car & Drivers test results?


simple. they test new cars.


new cars, like the 4thgens, operate diffrently... they dont use cables or little gears.


the VSS is turned at a specific speed... in the case of the 4thgen T56, 17 pulses per driveshaft rev.

the computer (or in my case, SGI box) gets this signal and takes into account tire size, rear end ratio, ect, and it mathmaticly changes the signal to the correct one, and sends it to the speedo. so its highly accurate.

why is it constantly off by a specific number then? because the needle is tweeked. plain and simple. the speedo itself is getting the signal for 15mph and pointing at 18 or 12 or whatever.
you have to keep in mind, you have a stepper motor, screwed/rivited into a piece of metal, with PRINTED plastic/paper over it and a piece of plastic pressed on over that. of course it might not all line up perfectly in production.. theres alot of tolerances there.

to compare what the computers seeing to what your speedo shows(and you can do this with any EFI thirdgen) hook your laptop up and watch the speed on it... this is what the ECM sees... compare that to what the speedo says... my 91 is dead on compared to the ECM.... but the speed its showing is only close..... my speedo is currently calibrated by doing the "pace a friend in the car next to you and mathmaticly figure the correction ratio from that" method.
its very very close though... compared to the radar signs cops put up, it was dead on with the 2.73s... sicne i put the 3.42 rear in, i havent found a speed sign...

 

mine rushed up and then slammed on the limiter.... it felt like i tapped the brakes.

only mods were open element and catback. i know i went past 114 once, but i had the VSS disconnected so i dont know how far past....

 

MrDude is 100% right on. He clearly explained mechanically why our speedos are off. :hail:

Dewey,

You must have had some long road