Top Speed 68mph: 4.56 Gears. Normal? Just Making Sure.

98Mustang2017 said:

95 v6 stock 5speed
I'm just posting this thread so others will know a bit about 4.56

high 4th and low 5th i gain no more power and the engine sounds a LOT different as if hitting valve float. RPMs do not change. Top speed is around 65-68mph.
Everything is stock besides the octane spout being removed(3degree ignition pull).

other than that the car spins the tires 1st through 4th way too easy. I need a gear change before i get an Excessive Acceleration ticket or three.
Fear the gear? More like the gear should fear me .

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65 seems pretty low. What does your tach indicate then? imp

98Mustang2017 said:

I think the tach was saying like 4800 in 4th gear. I run the stock valve springs if that makes a difference in max rpm.

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4800 in high gear. Lemme figure out some numbers on that. Try to get back tomorrow. too drunk to continue tonite!

98Mustang2017 said:

CoOOl. Just don't post the math numbers or it will give me a headache and the room will start spinning like a hang over lol . Seriously though, math is not good with me. Great stuff. But not for me. lol.

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Need tire and wheel size and rear axle ratio. imp

98Mustang2017 said:

Stock, stock, and 4.56 .
ummm.. yeah i have no idea on tire sizes yet. wheel size is 15" though.

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Well, I just don't know the stock tire sizes. My '94 has 245-45-17. I can't tell you more about rpms without the actual tire and wheel size, not WIDTH, diameter. imp

98Mustang2017 said:

oh ok. i've heard people referring to having like 27inch tall tires. i didnt know you were asking for the whole thing but its 205/65- 15 .

I might as well ask to see the formula to this equation. i sure hope i'm not asking for a grenade of numbers because blegh. math. and headache.

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Shoot! OK, even if "hot water" follows me for it: You need to know the tire "rolling diameter" and axle ratio. The diameter you can measure closely enough with a steel measuring tape, or use numbers related to the tire size. Here goes: First, you need to convert metric tire numbers to English. I take the first number, 205, which means tire tread width in millimeters, and times it by 0.03937. That gives it in inches: 8 inches. Next, second number, 65, means how WIDE the sidewall is compared to the tread width, as a percent, 65%, which is .65. Times that .65 by the width, 8 inches, and get 5.2 inches for sidewall width, now ya got all ya need to get tire diameter: Add sidewall, 5.2" and wheel diameter, 15", and another sidewall diameter, 5.2", and get 25.4 inches, a pretty good, standard for Mustangs.

Relating to the gear ratio, you need the tire circumference, distance it rolls to make one turn. Chalk mark tire and floor, roll car to get tire to turn one turn, mark floor where the sidewall mark winds up, measure the distance on the floor. It'll be about 80 inches. How man 80-inch rolls in a mile? Divide 80 by 12 (inches per foot), get 6.6 feet. Know a mile is 5280 feet, so 5,280 divided by 6.6 gives you 800 tire rolls per mile. But the driveshaft, and thus the engine, in HIGH gear, turns 4.56 times that 800, or, 3648 engine revolutions per mile, 3648 rpm at 60 mph.

Using the tape measure on the tire is the easiest, probably. You can use the numbers anytime you want to know about different tire sizes, axle gears, even tell about how much your speedometer will change with different tires. imp

60 mph is a mile a minute, we want engine revs per minute,

98Mustang2017 said:

Alright back from some more testing.

i removed my MAF sensor and i feel like i gained more acceleration power.
ok anyways, in 5th gear the car is PEGGED at 3k RPM. i think a fuel or ignition cutoff is there. it SOUNDS like it revs higher but that may just be a rapid cut-off of fuel/air.

I like this car even more now because when it dies when i slow down(because disconnected MAF and havent learned to heel-toe brake/throttle) it feels more like a car should. manual everything.

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Dude you really need to not mess with the car untill you read about how an efi engine works. MAF sensor is there for all the fuel related calculations. Plug it back in go to AutoZone and have them pull the codes. It's most likely that your rpm limited in high gear by the ECU

When I converted my old, '71 F-150 390 FE block to EFI, in a hurry and moving clear across country, used an AOD, getting the downshift rod jury-rigged to work off the throttle body, which was the T.B. made for 460 EFI which bolted right onto the 4-bbl. carb. manifold, I completely FORGOT to provide a Throttle Position Sensor! Damned thing ran OK, but drank fuel, as the PCM tried in vain to sort things out!

Took no pics, unfortunately. If anyone cares to hear I'll describe how I used the 390 intake manifold with injectors mounted above intake valves, and affixed the EFI distributor bowl to the 390 dist. base. imp