Yea the cars are good on gas when treated right, I had a 2000 vert M6 with a bassani exhaust, k/n cold air, and a tune and I could average 20 to 23 around town not babying the **** out of it just driving normal. I still did worse below 55-60mph in 6th gear. I'd say it is the area I live in which is north east TN and it his very up and down as far as hills.
Steep rear end gears (4.10s) compensated by replacing overdrive in a T5?
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Yea the cars are good on gas when treated right, I had a 2000 vert M6 with a bassani exhaust, k/n cold air, and a tune and I could average 20 to 23 around town not babying the **** out of it just driving normal. I still did worse below 55-60mph in 6th gear. I'd say it is the area I live in which is north east TN and it his very up and down as far as hills.
Man.... found a really good article on fuel mileage, and it does mention the vacuum gauge which is cool. Apparently the vacuum tells you how hard you should accelerate: How To Increase Your Gas Mileage
It also supports my premise that driving around 45 mph was perfect in the vette. It actually says 35-45, but I don't think going slower than 45 would be advisable in 6th gear, and 6th gear was always noticably better for mileage than 5th.
Chris
It also supports my premise that driving around 45 mph was perfect in the vette. It actually says 35-45, but I don't think going slower than 45 would be advisable in 6th gear, and 6th gear was always noticably better for mileage than 5th.
Chris
Yeah, I can see how steep hills would be worse on the vette at 45 in 6th. Hell, that's barely above idle.
Thanks for the info, Mike. I would've guessed that the fuel economy computers did computations based on injector duty cycle and miles traveled since being reset.
Chris
Thanks for the info, Mike. I would've guessed that the fuel economy computers did computations based on injector duty cycle and miles traveled since being reset.
Chris
Well with a 0.52 ratio,
you would have basically a 2000 RPM drop from 4th to 5th.
SO get your revs up in 4th, get ready to coast and then drop into 5th.
I definitely wouldnt try a WOT shift from 4th to 5th gear.
Only downside is cost. i want to do the same thing, but can't find a good source for cheap O/D gears...unless you've found one.
I beleive astro performance sells them for $200
I could see how you could get used to the 4th to 5th shift, just like any other mod. A t56 is out of the question for me cost wise, but a better overdrive 5th cog seems feasible. I don't think Id miss my current 5th too much, its not like its used very often in town, and is mainly just for highway cruising. Its appealing to me because I really do miss the low rpm cruising of the 2.73s with the top down on the way to the cabin, and this would let me have the best of both worlds. It would be interesting to calculate the cost vs. gas savings to see how long you would have to drive before the gear starts paying for itself.
Lets estimate a 7mpg increase, 27 mpg highway vs 20 mpg, so 5.5 gallons used vs 7.5, at $4 a gallon. A round trip to my cabin is 150 miles... so you'd save $8 every time. So i guess Id have to make 25 trips to break even. Of course this would be lower because Id save on daily driving too, but it would still take awhile to break even. Its hard to say if its a worthwhile investment or not for some comfort and economy.. hmmm
tranny
I think its a good idea. you don't have to worry about a huge rpm drop because shifting to 5th is only for cruising down the highway. 5th is not an acceleration gear anyways. it will cost a little money though, plus time. If you are considering adding horsepower in the future, you'll need a stronger tranny anyways. i have a tko500 5 speed in my 88gt and I know for a fact you can order them with any kind of modifications you want from the beginning. I know a lot of guys run a taller first gear than normal, so adding a .52 or something close for fifth gear would be no problem at all. Tremecs are great for rebuilding too, each gear has their own compartment so you do not have to tear the whole tranny apart to change something which saves you time and money!
I had a thought today, would it be feasible to have steep rear end gears for good around-town acceleration and then replace 5th gear in the tranny with a stronger overdrive to maintain highway cruising? I dont think Ive seen this done before, but it sort of makes sense
I think its a good idea. you don't have to worry about a huge rpm drop because shifting to 5th is only for cruising down the highway. 5th is not an acceleration gear anyways. it will cost a little money though, plus time. If you are considering adding horsepower in the future, you'll need a stronger tranny anyways. i have a tko500 5 speed in my 88gt and I know for a fact you can order them with any kind of modifications you want from the beginning. I know a lot of guys run a taller first gear than normal, so adding a .52 or something close for fifth gear would be no problem at all. Tremecs are great for rebuilding too, each gear has their own compartment so you do not have to tear the whole tranny apart to change something which saves you time and money!
SO who has the best price on 5th gears?
I have my t-5 apart...so it's now of never for a taller 5th gear
I have my t-5 apart...so it's now of never for a taller 5th gear
I read, just the other day in a Car And Driver magazine, that leaving the car in gear while coasting down hills or to a stop is actually more effective in terms of saving gas than slipping it into neutral. Why? Because most modern fuel injection systems can recognize engine braking conditions and disable the fuel injectors until the car is allowed to idle normally, or the throttle is again opened. It makes sense, something I never considered before, as most of my EFI tuning knowledge is based on conditions where the throttle butterfly is WIDE OPEN haha.
Check it:
Gas Pains: Mileage Myths and Misconceptions - Feature/Features/Classic Cars/High Performance/Hot Lists/Reviews/Car and Driver - Car And Driver
Sounds reasonable to me, but I'm confident that's not the case in my car. Either way the TB is closed and the TPS reads 0 load. The injectors will only be spraying a minimal amount of fuel to keep the AFR at 14+:1. Regardless, my decision to drive in this manner didn't come from theory or concepts, but from experimenting with the DIC in the vette, which shows an increase in instantaneous fuel mileage coasting down hills in neutral as opposed to leaving the car in gear.
Plus, leaving it in gear, as you already mentioned "engine brakes" the speed of the vehicle. I don't want to slow the car down or to keep it from picking up speed on its way downhill. So even in a newer car using less fuel on the way down the hill, it still may not be the right thing to do.
Chris
Plus, leaving it in gear, as you already mentioned "engine brakes" the speed of the vehicle. I don't want to slow the car down or to keep it from picking up speed on its way downhill. So even in a newer car using less fuel on the way down the hill, it still may not be the right thing to do.
Chris
Also, the thread you linked seems to be discussing the disadvantage of going into neutral in an auto, not a manual. Because the Tq converter allows slippage, it won't engine brake at the same rate as with the manual. If I get a chance when I start driving the vette again, I'll demonstrate on video for you.
Chris
Chris
I have 4.10's but want a very high overdrive cause I like to make runs well above 140 mph... 4.10's and stock 5th gear is redlining right around 160....
Don't flame me for that.. I live somewhere where I can do this safely.. You most likely don't
And yes, the overdrive is the close to the same in a cobra t-56 as in t-5... I'd rather have a 5 speed anyway if you have enought power.. Shifting just slows you down
Its not that I don't believe you, the topic just related to that article in C&D. Food for thought. You don't have to do the video unless you get really bored, haha.
Curiously enough, even though the GM rep mentions automatic transmissions, the page's image shows a MT car. And who takes the effort to shift into neutral in an AT car when coming to a stop anyway? Weird. Maybe the GM rep was just rambling, or its just a partial quote.
You and I have been derailing threads like we get paid to do it here lately...
Glad someone else can see it my way
I love bangin gears but if that extra gear doesn't get me any faster in the top end then it's a waste. Now, if there's an option to get that top speed 6th gear then i'd just go a step higher in gearing to maybe 4.30s so it'd be a monster at the track but still haul ass with the best of'em on the highways.
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