3.55 vs 3.73, how much of a difference between?
WOODSS
I'm just wondering about how much of a difference there is
between these. For an example, let's say I have a stock car with
5spd and 3.08 rear end, it runs 15.3 ET @ 92Mph. The car also
gets 28Mpg Highway, 18 Mpg city.
With a 3.55 would my time drop to approximately (just a
close guess will do) 14.8 seconds? Then would my gas mileage
also drop to say 24 Mph Highway, 15 Mpg city? Would it make that
big of a difference or more?
If I went to 3.73 would the time drop to 14.4 seconds with
gas mileage of 20Mpg Highway, and 12Mpg city?
Also, lets say that the car currently tops out at 140Mph
with the 3.08. If I go to a 3.55 would my top speed drop to
135Mph, or would it be lower? If I went to a 3.73 would my top
speed drop to 130Mph or lower?
I would just like some ballpark figures to see if going to
the 3.73 is worth it in comparision to a 3.55.
Thanks for your time!
** "Never tell the same lie twice!" **
Garak, DS9
F. Sam Woodson
E-Mail sam.w...@daytonoh.ncr.com
* * I've Never posted as Anonymous, and never will *
Don
Read my post on another thread discussing cartest.exe, you might find
it a useful program for you.
Since I've aready done simulations on the program using different
gears for my car, I can tell you what I got out of it. BTW, I'm using
a 4.6L pumping out 215hp and 285lbs./ft of torque and a T-45
transmission.
With 3.08s, 0-60 was 6.67sec. and the1/4mile was 15...@93.0mph.
With 3.27s, 0-60 was 6.61sec. and the1/4mile was 15...@91.0mph.
With 3.55s, 0-60 was 7.20sec. and the1/4mile was 15...@91.8mph.
With 3.73s, 0-60 was 7.11sec. and the1/4mile was 15...@92.2mph.
As you can see the numbers actually got worse because of having a top
speed of 65mph in 2nd gear with the 3.08s, it drops to 57mph with the
3.55s. I wouldn't go past 3.55s without planning to add more power. So
what's the advantage of going 3.55's now? 40-70mph times are a lot
better. It seems pretty accurate considering the impressions I'm
getting driving my car with the new 3.55s.
Don
'97 GT, T-45, SFConnected, 3.55s
On Tue, 5 Nov 1996 12:19:26 GMT, WOODSS <Sam.W...@DaytonOH.NCR.Com>
wrote:
Don
(Sorry if this is a repeat. Dumb server was giving me write errors)
Well, I haven't taken my car out to the track for some real testing
either and I thought the numbers looked odd too when they first came
out but let me try to explain how the program got those numbers and my
opinions on the 3.55s on my car now...
The program shows that with the 2.73s, 3.08s and 3.27s the car is able
to accelerate past 60mph in 2nd gear giving the estimated times
listed. It seems that the 3.27s are the best gears considering the
stock hp numbers and torque (215hp and 285lbs/ft for my 4.6L GT)
With the 3.55s, the program figures out that, with the horsepower
available, 57mph is the top speed for 2nd gear. Which means, in a
0-60mph run, you'd have to hit 3rd gear. The extra gear shift would
slow the times compared to a higher gear needing only 2 gears to get
to 60 and that's how the program got those times. Neat huh? To make
the 3.55s more useful in an 0-60 run, you would have to add enough hp
to get the car to 60mph in 2nd gear.
Of course the main focus here is 0-60 times. If you look at roll-on
acceleration times and 40-70mph acceleration times, they improve with
every gear increment and that's where most of the hands-on driving
will show in the way it pulls stronger in every gear (it's really nice
now).
I've only had the 3.55s in my car for 1 week (I did put about 800
miles in though :) and from what I can "feel," the car does pull A LOT
stronger. With my old 2.73s, I had to downshift to 2nd, anytime I
needed more power. With the 3.55s, it accelerates and the revs come up
a lot faster in every gear. I can actually break traction in 1st AND
2nd gear!
I wasn't watching the speedo when doing a few launches but it does
seem as though I'm coming short of 60mph in 2nd and that I probably do
need to be in 3rd to drive me through it, so the program numbers have
made sense to me for my situation. It does feel as though it needs
quite a bit more horsepower to bring the power curve in-line with the
new gear.
With your '88 GT and 3.55s, maybe you do have enough power to go
through 60 in 2nd gear, or maybe your power starts dropping off as you
get to 60mph in 2nd gear and need to shift into 3rd. Can you tell me
whether you do or not? If I were to keep the hp numbers stock, I would
have also considered going with 3.27s and get better gas mileage
considering the ET diferences were practically the same (traction loss
does get factored in the program and I still have the 225 16s). But
I'm thinking Vortech in the future so I'm planning ahead but in the
mean time, it's so much better having power available in every gear
compared to the 2.73s.
With the 2.73s, I will say I do miss "cruising" at 80mph at only 2000
rpms; sooo smooth at that speed :)
So what do ya think?
Don
'97 GT
>Don-
>
>Not doubting what you are saying, but the numbers sure
>_look_ weird. It would seem that as you lower the gear
>ratio you would see much better 0-60 times and perhaps
>a lower ET, unless traction was a problem or the engine
>is some kind of torque monster engine that won't rev
>or can't breathe on the top end. My 88 GT _seems_ much
>quicker with the 3.55s although I haven't had it down
>the strip. Anyone else here think these numbers look
>weird? The ETs are flat. I'd run the 3.08s and get better
>gas mileage if that were the case <G>.
>
>Mike
Don
Just for the heck of it, I ran Cartest, used an '89 GT that they have
in the databank and compared 0-60 and 1/4mile times using different
gears. The results are interesting (if it's correct)...
'89 5.0L GT - 225hp/300lbs.ft. torque
With 3.08s, 0-60 was 7.17sec. and the1/4mile was 15...@92.0mph.
With 3.55s, 0-60 was 6.91sec. and the1/4mile was 15...@92.8mph.
With 3.73s, 0-60 was 6.86sec. and the1/4mile was 15...@92.5mph.
If you recall the data with the 4.6L GT - 215hp/ 286lbs.ft. torque
With 3.08s, 0-60 was 6.67sec. and the1/4mile was 15...@93.0mph.
With 3.27s, 0-60 was 6.61sec. and the1/4mile was 15...@91.0mph.
With 3.55s, 0-60 was 7.20sec. and the1/4mile was 15...@91.8mph.
With 3.73s, 0-60 was 7.11sec. and the1/4mile was 15...@92.2mph.
Why did the '89 GT have better 0-60 times as you increase in ratio?
The gearing in the T-5 in the '89 GT is different than the gears in
the T-45!
With 3.55s, the '97 GTs top speed in 2nd gear is 57 mph.
With 3.55s, the '87 GTs top speed in 2nd gear is 51 mph giving it
better drive through 60 in 3rd gear. The 4.6L's 0-60 numbers look bad
because it's stuck shifting into 3rd at around that speed. How do the
figures look now?
Don.
On 8 Nov 1996 03:08:11 GMT, "Mike Burress" <mbur...@ix.netcom.com>
wrote:
>Don <don...@gnn.com> wrote in article <328129ec...@news.gnn.com>...
>> Read my post on another thread discussing cartest.exe, you might find
>> it a useful program for you.
>>
>> Since I've aready done simulations on the program using different
>> gears for my car, I can tell you what I got out of it. BTW, I'm using
>> a 4.6L pumping out 215hp and 285lbs./ft of torque and a T-45
>> transmission.
>>
>> With 3.08s, 0-60 was 6.67sec. and the1/4mile was 15...@93.0mph.
>> With 3.27s, 0-60 was 6.61sec. and the1/4mile was 15...@91.0mph.
>> With 3.55s, 0-60 was 7.20sec. and the1/4mile was 15...@91.8mph.
>> With 3.73s, 0-60 was 7.11sec. and the1/4mile was 15...@92.2mph.
>>
>> As you can see the numbers actually got worse because of having a top
>> speed of 65mph in 2nd gear with the 3.08s, it drops to 57mph with the
>> 3.55s. I wouldn't go past 3.55s without planning to add more power. So
>> what's the advantage of going 3.55's now? 40-70mph times are a lot
>> better. It seems pretty accurate considering the impressions I'm
>> getting driving my car with the new 3.55s.
>>
>> Don
>> '97 GT, T-45, SFConnected, 3.55s
>>
>> On Tue, 5 Nov 1996 12:19:26 GMT, WOODSS <Sam.W...@DaytonOH.NCR.Com>
>> wrote:
>
Mike Burress
sean1...@aol.com
I put 3.73 in my '92 GT. I have not run it since changing it at the
track. Last run
was 14.57 and 97 mph on warm AZ. evening. Gas mileage stayed the same,
or
just a little higher (17 Mpg.). Probably top speed would go up, you can't
pull
redline in OD anyway. I was not concerned about gas mileage. For all out
performane 3.73's seem to be the way to go. It was well worth it.
Josh
Don (don...@gnn.com) wrote:
: (Sorry if this is a repeat. Dumb server was giving me write errors)
: Well, I haven't taken my car out to the track for some real testing
: either and I thought the numbers looked odd too when they first came
: out but let me try to explain how the program got those numbers and my
: opinions on the 3.55s on my car now...
Those numbers are wrong... Lowering the gearing is going to increase
torque multiplication and increase acceleration through the gears. The
only reason you would slow down would be lack of traction. The only
reason you'd slow down in the 1/4 mile is finishing too low or high in the
powerband for whatever gear you go through the lights in..
--
=====================================================================
Joshua J. Lowe - / - bo...@newworld.bridge.net/bo...@shadow.net
=====================================================================
Justin Luton
From the look of it, you haven't re-ran the "Optimize Launch" option
after changing the final drive ratio in the CarTest program. All of
the cars i've put into this definitely have benefitted (at least et.
wise in the 1/4 and 0-60)
On Thu, 07 Nov 1996 00:21:56 GMT, don...@gnn.com (Don) wrote:
>Read my post on another thread discussing cartest.exe, you might find
>it a useful program for you.
>
>Since I've aready done simulations on the program using different
>gears for my car, I can tell you what I got out of it. BTW, I'm using
>a 4.6L pumping out 215hp and 285lbs./ft of torque and a T-45
>transmission.
>
>With 3.08s, 0-60 was 6.67sec. and the1/4mile was 15...@93.0mph.
>With 3.27s, 0-60 was 6.61sec. and the1/4mile was 15...@91.0mph.
>With 3.55s, 0-60 was 7.20sec. and the1/4mile was 15...@91.8mph.
>With 3.73s, 0-60 was 7.11sec. and the1/4mile was 15...@92.2mph.
>
>As you can see the numbers actually got worse because of having a top
>speed of 65mph in 2nd gear with the 3.08s, it drops to 57mph with the
>3.55s. I wouldn't go past 3.55s without planning to add more power. So
>what's the advantage of going 3.55's now? 40-70mph times are a lot
>better. It seems pretty accurate considering the impressions I'm
>getting driving my car with the new 3.55s.
>
>Don
>'97 GT, T-45, SFConnected, 3.55s
>
>On Tue, 5 Nov 1996 12:19:26 GMT, WOODSS <Sam.W...@DaytonOH.NCR.Com>
>wrote:
>
Paul Leedell
>>>Just a thought. If the sim. thinks the horsepower figures are at the
>>>drive wheels regardless of axle ratio, then changing the axle ratio
>>>will
>>>have no effect on times since horsepower and torque at the wheels would
>>>be
>>>the same (rather than increasing as with an increase in gear ratio).
>>>Everyone knows increasing the gear ratio gives shorter 1/4 times. The
>>>sim
>>>is wrong. It thinks torque at the drive wheels doesn't change with
>>>gear ratio.
sayb...@aol.com
The whole purpose of matching rear end gears with transmission gears is to
be going through the time traps as your engine maximizes its output in
whatever final gear you use. To say that a car will go through the traps
at the same speed with four different gear ratios is ludicrous. In the
50's we ran with the Borg-Warner close ratio four speeds. First gear was
2.20:1, second was 1.91:1, third was 1.51:1, and of course, fourth was
1:1. 4.56 seemed to be the rear end gear of choice. The idea of the
close ratio was to KEEP the engine in the POWER range as much as possible.
Ideally, you wanted to be going through the traps in fourth gear with
your engine topping out in rpm hp. Tire size would actually change the
effective gearing. Example, in first gear, at 2.20:1 times 4.56 (rear end
gear), we would effectively be coming off the line at a gear ratio of
10.32:1 Now when we shift, the drop will not be that great because we
will be going 1.91:1 times 4.56. What this does is keep our engine reving
in it power range. The high the rear end gear, the lower the top speed
but the faster you will get there. FORD has played a nasty game on us.
Their first gear ratio is somewhere in the 3.12:1 ratio. Multiply that
times your rear end gear and out the showroom floor, it feels like the car
really has power. We all know what happens to PULL once we get into
fourth or fifth gear, especially with the 2.73 gears. In my many years of
drag racing, whenever I increased the ratio of my rear end gears, my ET
always came down. I never cared that much about speed, just wanted to get
their first. I have a 92GT convertible with 3.73 gears in it and I am
considering going to 4.10's or 4.30's, if they make them. Even with my
extra weight, (convertible) I am able to walk away from many sedans
running 3.55's. My advice is go to the 3.73's or higher. Lastly, I must
say, with no disrespect intended, I was shocked at the info that has
preceded. Good luck.
Don
On 17 Nov 1996 05:09:26 GMT, sayb...@aol.com wrote:
<snip>
>running 3.55's. My advice is go to the 3.73's or higher. Lastly, I must
>say, with no disrespect intended, I was shocked at the info that has
>preceded. Good luck.
I apologize to everyone for my previous posts on this thread. In no
way, did I intend to pass off the numbers as "real" figures. Someone
posed a question on approximate figures and I thought that this little
program could give him an idea of what kind of numbers he could expect
to see (but even then, I messed up because I didn't know there was a
difference in the T-5 and T-45 gears and am also disappointed at
myself for even posting my opinions on this at all). Desktop
benchracing is no substitute for actual track-time which I have little
on cars.
In the future, I'll try to keep my opinions based on my own personal
experiences.
With that said, I am curous if anyone has installed 3.55s in a T-45
equipped 4.6L SOHC GT and if they can share their opinions on the gear
change. I had just had 3.55s installed in my 4.6L and wanna know if
other people are getting the same impressions that I have.
- -
Don
'97 GT
http://members.gnn.com/donmui/five-oh/five-oh.htm
Edward Kim
Don (don...@gnn.com) wrote:
: With that said, I am curous if anyone has installed 3.55s in a T-45
: equipped 4.6L SOHC GT and if they can share their opinions on the gear
: change. I had just had 3.55s installed in my 4.6L and wanna know if
: other people are getting the same impressions that I have.
What are your impressions on the 3.55s? I'm going to get some 3.55s in
about a month and am curious to what it feels like on the 4.6L SOHC.
--
Edward Kim
Georgia Institute of Technology, Atlanta Georgia, 30332
uucp: ...!{decvax,hplabs,ncar,purdue,rutgers}!gatech!prism!
1996 Mustang GT White/Black interior 5-speed
Don
Acceleration is LOTS better. Expect your revs to be about 600 rpms
higher in everything you do (if you're going from 2.73s). In the city,
I use to shift at about 2000 rpms with the 2.73s but now it's about
2500rpms. Power is available in every gear and 2nd gear is no longer
the only choice of gear when you need to downshift for a burst of
acceleration (but it's a lot more fun now).
Highway driving is still acceptable. The one thing I liked about the
2.73s was "cruising" at 80mph @ 2000rpms but 5th gear was useless when
you needed a little acceleration. Now, 70mph is 2000rpms, 80mph is
2600rpms, and 5th gear is now a little more responsive when a short
burst of power is needed.
Decent gas mileage is still possible but you can also go thru a tank
of gas a LOT faster if your not careful. Last week, my city/hwy
mileage was 19.83mpg. This week is not as good...
The one downside I am feeling is city driving; specifically when
accelerating off a dead stop. When driving conservatively, I try to
make my shifts at 2500rpm. But 2500rpms in 1st gear is 15mph, and
about 25mph in 2nd gear meaning you (I) lag behind in traffic. Some
people may not care, but I do. I don't mind taking it easy on the road
but I don't like the feeling of lagging behind in traffic when
accelerating off the light. Of course the only thing to do then is
shift at 3000-3200 rpms but then your blowing a lot more fuel and
making a little too much noise for "conservative" driving.
I think that this also has to do with the powerband of the 4.6L. Below
3000rpms, it is REALLY underpowered and with the 3.55s you really feel
it. 3000-5000rpms is where the meat the powerband is but after
5000rpms the power drops off. So the 4.6L has a real narow powerband.
I'm still working on restraint but this week it just got the better of
me and I've been punching it a little harder.
I definitely like the 3.55s. If I had 3.27s and had no plans to add
any power, I'd probably stick to that but if you have 2.73s and plan
to do a little engine work, the 3.55s are your best choice. I think
3.73s would not be your best choice if gas mileage and highway driving
was a concern.
Hope this helps give you an idea of what to expect.
Don
http://members.gnn.com/donmui/five-oh/five-oh.htm
On 18 Nov 1996 00:18:09 GMT, gt7...@acmey.gatech.edu (Edward Kim)
wrote: