Why is my car slow..?

[SlowStang2]

OK here goes. I own a 94 5.0L 5-Speed Mustang GT Convertible. I have BBK shorty equal length headers, BBK off-road h-pipe, Flowmaster American Thunder Cat Back, Mac Cold air induction w/K&N, 65mm T/B, Cobra upper and Lower intake, fuel adjustable regulator, pulleys, 9mm wires, 3.08 gears, aluminum driveshaft. With that setup i ran a 14.3@101. Not bad for 3.08s right? Well i installed 3.55s. I ran a 14.8 consistently. I had no problems in traction, launch, shifting, and the car ran as well as it did with the 3.08s. I had some1 look at it and they calibrated the computer a bit and checks for vacuum leaks...I then installed 24lb injectors and a Pro-M 77mm(calibrated FOR the injectors) and I run a lousy 14.6. CONSTANTLY. Needless to say i am pissed. All in all the car runs great. Shouldn't I be in the 13s??? And I know it isnt me, cuz after all the runs ive done (which is over 20) I would ACCIDENTLY gotten a good run by now. Come on. If there could be a problem I can't find myself or have overlooked to check, can some1 share some light on the subject? Or maybe some1 was in the same situation im in now that could be of any help, i would be most grateful. ctrlmeeee@aol.com

[90dpscoupe]

Not bad actually, well the 14.3, you may need to get used to the grs, but dude your car is heavy, a set of 3.73s or 4.10's would of been a little better, but i understand your frustration, my friend dumped lots of $ building a 347 to run 14.8 , of course he still had stock intake and tb. You might need to play with the FP regulator, run some scanner codes, im not sure what to tell ya, but i think low 14's @ 101 is good for a car like yours with stock heads imo. whats your timing set at?

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90 lx coupe: Mac cold air fenderwell, accel supercoil,ADS chip (not yet track tested),3-core radiatr, FMS alum D/S, Black magic fan, 3.27grs, 3chbr flows.
Best time: 13.9116(on 225/60/15 firehawks)
Best mph: 98.17
Best 60': 1.9607

next mods: subframes, mac h-pipe

[Skyman]

Whats your mph. that indicates whats going on here. 101mph is awesome for you mods and can take you into the 13's w/ traction and gearing.

Skyler

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-1989 Saleen Mustang #406- TFS Heads, E-303, edelbrock intake,70MM TB, 73mm MAF, off road H, headers and 3chamber flows.
12.55@107mph
Mustang owners get a 15% discount!
www.OJAIPCPROS.com

[dinomite]

Ya, you must be having traction problems, or be shifting slow/wrong place.

[exgmguy]

Yeah, we really need to know the mph to tell if it is a traction problem or a motor problem. 101 does sound pretty fast for that car with those light mods.

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1988 Mustang GT
12.0 @ 122
1992 BadAzz Wrangler
1993 Explorer

[SlowStang2]

My current MPH is 100 or 99. I have gotten it down to 14.4 @ 100 at best. My timing is set at 12 degrees. Other than that the car pings (im in FL..its HOT HERE!!) I can't understand how 3.08s will deliever me 14.3s but 3.55s get me worse. Then I put in the Mass Air and injectors and it bought me 2 tenths. How good is my stock fuel pump for? Like for how much HP? Also what RPMs have granted everyone the best shift points? I have shifted all over, but maybe I am forgetting a golden rule some one knows..?

You can have a good combo (which you do) but it all comes down to the driver. Traction is usually the time killer....also, like dinomite said you may be shidting to early or too late (every car is different and everyone has to know what works best for his/her car). I think you should be in the mid 13's. Get a nice set of heads and you'll be there for sure.

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'90 LX 5.0; 12K original miles (no sh*&); 3.55 gears; pulleys;Edelbrock Performer Heads; BBK shorties; MSD 6AL box w/ blaster 2 coil; Motorsport E303 cam; Pro-M 75mm MAF; BBK 70mm TB; Eibach spring kit; Southside welded subs; K&N cone filter charger; Hurst shifter; fiberglass turbo hood; A/C-less; rear seat-less; cat-less; 2 chamber Flos; Corbeau racing seats (fronts);
30# injectors; JMS Chip; 190 lb fp; TFS track heat Intake (12.299 @ 113)

[bigwhitecobra]

I was reading this and I think I figured out what the problem is. Ok bear with me here for a second ok?

Ok, with the original setup you had with the 3.08's, let's say you were shifting at 5000 rpm just to make this work, you were pulling 14.3's. Now that you have a 3.55 gear, your engine will be reving up quicker, which means that you will have to shift earlier. Shifting too late will cause the funky ET's. Now, I'm not saying that this is the problwm, but it is a very good possibility. try shifting 500 rpm lower.
My best runs with my Cobra came as a result of shifting at 4400, and I have 3.73's. After that my power curve seems to wavier slightly. It will pull untill 5600, but like I said, my best times came at 4400. try it and see. Let me know if that works, or if I'm full of chit. Later man.

[moosejaw]

You are shotgunning your engine tune. Get it to a dyno shop and do some tuning. If they have a wide band O2 all the better.

94 and 95 computers are notorious for pulling out timing above 4000 rpm. (Ford wanted to conserve some trannies for warrenty issues.) Prior to your gear swap you spent less time above 4k than you do now. You probably have a net loss of torque when running at the strip, due to the timing retard. If your engine is knocking with high octane fuel there is a problem. If you are not using high octane fuel then try some and gradually add base timing. This should help some. The best fix is to chuck the 94 computer for the 89-93 with a conversion kit from pro-m.

Mike

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Live near St.Louis?
Check out Mustang Muscle and Dyno in High Ridge, MO
Check out my ride.

[exgmguy]

Hot weather or not, if you are detonating at 12 degrees of timing with premium gas you have a problem. It sounds to me that you are running too lean. What is your fuel pressure at WOT? If you have a fuel pressure gauge on the schrader valve you won't know. Just winging the throttle won't tell you. You need to read the fuel pressure under load, all the way up the rpm scale.

With you combo 24 lb injectors are not yet necessary. Probably 32 psi at WOT is all you need.

Also your stock fuel pump may be failing.

[exgmguy]

I also believe that stock headed cars should shift at 5000-5100 rpm tops.

[Unit 5302]

Hmmm... by the factory tach, I get my best runs shifting at 5800. Stock 87GT engine, BBK hiflow, 2.5" exhaust, K&N.

I'll lose 2mph shifting over or under.

Now, you say you've been shifting all over the place. If you were shifting really high in the rpm's, which is what the taller 3.08's would have liked, when you switched to the 3.55's, you'll lose ET. Simply because you won't drop as many rpm's, and you're outside your powerband.

You should be shifting around 600rpms lower than what you were, at least.

[SlowStang2]

Well, I finally took my mustang to a mustang specialist. He dynoed the car to having 225rwhp. He told me that sounds about right for my car with the mods I listed. I got the car to run 14.40@100, but no better. I gotta tell you, I'm disappointed. Also, the mustang guy said that with all my mods, like the Cobra intake, they aren't working at their full potential because of my stock heads. Nonetheless, those stock heads got me in the 14.3s, at one point at least. I'll be getting my heads, I'm not sure which will be the choice that will add HP but not alter anything in the car's driveability, but if after I get these heads and I don't see an improvement, my mustang days are over. Unless,....a supercharger pops up from someplace.

[Hounddawg]

Having read what everyone had to say, I got something to add. Considering how heavy your car is and a speed of 100MPH, I would have to say that your car is capable of running faster than a 14.4 et. Sounds like either the traction or shifting needs to be improved. My recommendation is to get better traction and keep working on your shift points nad reaction time. The first 60 feet are VERY important.

[blue00gt]

My friend's 94 Cobra with almost exactly the same mods runs 13.5-13.9 on street tires at a little over 100mph. Not sure what heads Cobras have on them stock, but if they are better than yours that could explain it.

What was your 60ft time? Judging from your trap speed, you should run high 13s if you 60ft even under 2.0 sec.

[Z28EATR]

a good way to find out if its traction is to look at the 60 ft times. I ran my best a 14.17 @ 98 and some change. But my best 60 ft on that pass by the way was still only a 2.158. Once i get my cheater slicks or some full baldy's i should get mid to low 1.9's. I have an 88 lx 5.0 ragtop. It weighs about 3540 with me in it. What 60 ft times is he pullin???

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88 LX 5.0 Ragtop
"Desire"
14.17 @ 97.65 mph
Best 60ft 2.19 YUK!!!!
Best Mph 98.9

[TJR]

There used to be a guy around here that had a 94-95 coupe with almost identical mods as you (SlowStang2) and I think he ran a best of 13.60 at 99 on cheater slicks. This was done at Norwalk which is like 100 feet above sea level.

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1989 lx notch
89,000 miles
bolt-ons,stock heads/cam
60'- 2.07, 8.90@78, 13.93@99

[Skyman]

I dont know what your complaining about. Your car has more mph than most. Get some real sticky tires. Learn how to launch and shift and you'll be way into the 13's.

Skyler

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-1989 Saleen Mustang #406- TFS Heads, E-303, edelbrock intake,70MM TB, 73mm MAF, off road H, headers and 3chamber flows.
12.55@107mph
50-175 Nitrous Works WET Kit just added.

[stevstum]

Are you sure that the gears you swaped out were really 3:08's. I test drove a car that the guy said was completly stock and when I drove it I was in 5th doing 70mph and the RPM's were at like 2500. You might have had a better gear it and did not realize it.

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Steve Stumbaugh

89 LX 5.0 5sp.
Removed air silencer
Motorcraft 8mm wires
Autolite platinum plugs
BBK O/R h-pipe

[fastang]

Originally posted by moosejaw:
You are shotgunning your engine tune. Get it to a dyno shop and do some tuning. If they have a wide band O2 all the better.

94 and 95 computers are notorious for pulling out timing above 4000 rpm. (Ford wanted to conserve some trannies for warrenty issues.) Prior to your gear swap you spent less time above 4k than you do now. You probably have a net loss of torque when running at the strip, due to the timing retard. If your engine is knocking with high octane fuel there is a problem. If you are not using high octane fuel then try some and gradually add base timing. This should help some. The best fix is to chuck the 94 computer for the 89-93 with a conversion kit from pro-m.

Mike

I dont think the 94-95 Cobra and GT share the same cpu. The GT's cpu is great. I think thats why they give you 2 different maf connectors when you buy a Vortec MAF. One connector is for the crappy Cobra CPU and the other is for the GT. I could be wrong but I dont think so.



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95GT B303 cam, 1.7 rockers, 65mm TB, milled heads, 355's K&N, BBK Longtubes, Flowmaster cat back, pulleys, msd coil, 9mm wires, Tremec 3550, Pro5.0 shifter,10.5 Motorsport clutch, FMS aluminum driveshaft, weld in subframe connectors