North American Turbocoupe Organization



Speed by RPM
Bader Offline
Junior Member
#1
I was wondering if anybody could tell me of the breakdown of the rpms into speed.
such as 5000 in 5th or 3000 in 4th. since i only have the factory 95mph speedo i don't know how fast my 87 t coupe with stock gears is actually goin. If anybody knows could they please help.

thanks
2.3L of Pure TURBO POWER
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Dan E Offline
Posting Freak
#2
Somebody correct me if my math is wrong (never my best subject...LOL):

Your T5 Gear ratio's are:

1st 3.97
2nd 2.34
3rd 1.46
4th 1.00
5th 0.80

RPM / Gear ratio = Drive Shaft RPM

Drive Shaft RPM / Rear Gear (3.55) = Wheel RPM

Wheel RPM X Tire Circumference = Inches of Wheel Travel per Minute

Inches of Wheel Travel per Minute / 12 = Feet of Travel per Minute

Feet of travel per minute * 60 = Feet of travel per Hour

Feet of travel per hour / 5,280 feet (mile) = MPH

If someone can tell me what the circumference of a stock 255/60/16 tire is...I can write a calculator to do this...
Dan Eaves
88TC 5spd Vermillion Red, Polished...everything...
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Walsted Offline
Posting Freak
#3
According to this website , the 225/60R16 are 26.63 inches, and the 225/60R15 are 25.63 inches tall.

The 255/60R16 are 28.05 inches tall, but that was a typo, right?.
------------------
Mike Walsted
1986 5-speed TurboCoupe .

[This message has been edited by Walsted (edited 07-22-2001).]
Mike Walsted - Sold my 1986 5-speed TurboCoupe
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Walsted Offline
Posting Freak
#4
Here is what I get for standard tire and tranny combos, and for my vehicle:

Yr/Gear------Ratio-- Tire---- Tran----Speed--Conversion factor
[email protected]
83-86 1st----3.45----25.63----4.03----16.5----0.005484164
83-86 2nd----3.45----25.63----2.37----28.0----0.009325392
83-86 3rd----3.45----25.63----1.49----44.5----0.014833007
83-86 4th----3.45----25.63----1.00----66.3----0.02210118
83-86 5th----3.45----25.63----0.81----81.9----0.027285408

87-88 1st----3.55----26.63----3.97----16.9----0.005621319
87-88 2nd----3.55----26.63----2.34----28.6----0.009537025
87-88 3rd----3.55----26.63----1.46----45.9----0.015285368
87-88 4th----3.55----26.63----1.00----66.9----0.022316638
87-88 5th----3.55----26.63----0.79----84.7----0.028248909

Walsted's 1st----3.55----26.10----3.97----16.5----0.005509442
Walsted's 2nd----3.55----26.10----2.34----28.0----0.009347215
Walsted's 3rd----3.55----26.10----1.46----44.9----0.014981153
Walsted's 4th----3.55----26.10----1.00----65.6----0.021872484
Walsted's 5th----3.55----26.10----0.85----77.2----0.025732334

Here is what I come up with. Multiply your RPM by the conversion factor to get your speed. The Speed column is speed at 3,000 RPM. The third set of numbers for my car is because I have a 87 'n/a mustang tranny, 3.55 gears, and will be getting 235/60R15 tires.

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Mike Walsted
1986 5-speed TurboCoupe .

[This message has been edited by Walsted (edited 07-22-2001).]
Mike Walsted - Sold my 1986 5-speed TurboCoupe
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SteveX82 Offline
Posting Freak
#5
Anybody know what the rev limiter stands at on the 87-88's? I've been debating for quite awhile now whether to keep my car in 3rd gear through the traps or shift into 4th. I've always been shifting into 4th about 200ft before the finish line, but my trap speed seems rather low (only about 89mph at 15.1) so i've been thinking about keeping it in 3rd instead.
Estoril blue 1987 TC 5spd, 148k mi, a237, Bailey BOV, spec stg3 clutch, spearco FMIC, 50 trim t3/t4, 3" exhaust, Bamafuel, LM1, 55pph
Best 1/4 mile: 12.31 @ 110mph on 25psi
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Pete D Offline
Administrator
#6
Steve, I'm pretty sure the rev limiter is at 6250rpm on the 87-88 TCs. I found out last year with the IHI that it was slightly quicker to shift to 4th than ride out 3rd,
because the IHI is just plain out of steam in 3rd.

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88 TC X 2, 86 SVO, Main TC with K&N, 3"DP to 2.5"duals through Dynamax, Ric valve at 17+ and disconnected KS.
Elite Bodega 16" chrome wheels. Autometer pod w/ A/F and Vac/boost gauges. New engine shortly, ported head and
manifolds, polished and cc'd chambers, A-230 cam, Race Engineering Adj Cam Sprocket, Crowlers, ARP head studs, Walbro 190 pump and T-3 for starters. KB subs
and jack rails.
Pete Dunham


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Dan E Offline
Posting Freak
#7
Quote:Originally posted by Walsted:
The 255/60R16 are 28.05 inches tall, but that was a typo, right?.

Yep...wishful thinking I guess LOL !
Dan Eaves
88TC 5spd Vermillion Red, Polished...everything...
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Dan E Offline
Posting Freak
#8
Using 26.63" Diameter equals a circumference of 83.66" (2 PI R).

That's all I needed. I come up with the following using my formula (3.55 Rear - 88TC T5):

-------- RPM ----- RPM ----- RPM
Gear --- 3,000 ---- 4,000 ----- 5,000

1st ---- 16.86 ---- 22.49 ---- 28.11
2nd ---- 28.61 ---- 38.15 ---- 47.68
3rd ---- 45.86 ---- 61.14 ---- 76.43
4th ---- 66.95 ---- 89.27 ---- 111.58
5th ---- 83.69 ---- 111.58 ---- 139.48

[This message has been edited by Dan E (edited 07-22-2001).]
Dan Eaves
88TC 5spd Vermillion Red, Polished...everything...
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Dan E Offline
Posting Freak
#9
Guys:

I just went for a spin and noted my rpm's at 60MPH in 3rd, 4th and 5th gears. Then I compared it to my formula and it is almost dead nuts right on target...
Dan Eaves
88TC 5spd Vermillion Red, Polished...everything...
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B D Offline
Member
#10
This is from the August 1987 Road&Track road test on the Turbo Coupe.
Speed in Gears
1st...................33 MPH
2nd...................56 MPH
3rd...................89 MPH
4th...................131 MPH
5th..RPM 4900...est...131 MPH
I do not know why they show no difference in speed between 4th and 5th.
B D

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87 TC 5-Speed
88 Thunderbird Sport 5.0
91 Ranger
87 Turbocoupe 5-Speed, Remote mount K&N filter system,Steeda Shifter,New Heater Core,new clutch.
88 Turbocoupe "Mach 1 SE "
88 Thunderbird Sport 5.0 (Retired)
91 Ranger
NATO Member
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