H/C/I and all bolt on's and still ran 14.24@94mph

[5.0hatch]

I've been trying to work out the bugs in my car for over a year and I'm fighting a never ending battle .

I went to the track today with these results:
First pass I missed 4th gear
1.84 60ft
8.40 1/8
13.7@77mph

Second pass
2.00 60ft (bogged)
9.01 1/8
14.24@94mph

I dont have a clue on whats going on here. My first pass would have been a low 13 for sure based on the 1/8th mile. But the second just sucks bad, I shifted at the same points and everything. I've trapped as high as 108mph before . I'm either thinking of selling the car are putting a carb on it, any ideas cause I give up and fed up? I've changed my maf and injectors last week and that for sure didnt fix it.

Mods:
15,000 mile stock shortblock
RPM intake
New style edelbrock heads
TFS Stage 1 cam
73mm maf
70mm tb
tried both 24lb and 19lb injectors
3.73s
bbk headers
pulleys

dynoed a sick 259rwhp and 275tq

On a side note, the car idles perfect with no surging are bucking. Gets 23mpg and drives like stock with no problems that are usually associated with the mods I have.

 

[IMPORTSMOKER]

hey 5.0hatch...where did you race at??

 

[willys1]

IMO,,I think you would be faster with a 65mm TB,,maybe get a dyno tune.

 

[Grn92LX]

70mm is the ideal size tb for your set up. The combo is fine, just somethings wrong. I rememebr you saying you did a compression test on cylinders 5-8, but have you done 1-4? Dont sell the car or convert it to carb, just continue trouble shooting and when you fix it you'll be happy. Do you have a fp gauge thats visible at all times? Fuel pressure could be dropping due to a bad/dying pump. Maybe throw a new 255 pump in. Put new spark plugs in. I know it sounds like a long shot, but my friend gained 50hp on the dyno due to his plugs being shot and he had no idea. They weren't old at all. What happened was, the car ran lean (due to a clogged fuel pump screen) and the lean condition killed the plugs. he made 3 pulls on the dyno, on pull #2 he made 255hp, pull #3 he put new plugs in and made 308hp. You may have an issue like my friend, try new plugs and consider a new fuel pump and a new filter too. Fwiw, his car went from runnign mid 13's @ 101 to 12.4 @ 110 the next week after the new plugs/pump. Try swapping easy parts from friends to see if it helps. Borrow a buddys distributer or anything else to eliminate it from being an issue. Im leaning towards a fuel issue (bad pump) and put in new plugs.

mike

 

[IMissMy93Fox]

I went to the track today with these results:
First pass I missed 4th gear
1.84 60ft
8.40 1/8
13.7@77mph

Second pass
2.00 60ft (bogged)
9.01 1/8
14.24@94mph

This is slightly off the topic but if you guys look at his 60' times you can see how much they affect your 1/4 time. I'm not trying to critcize you or anything, they're better than mine were but everyone on here talks about how important they are and you can see even w/ missing 4th .16 in the 60' was worth .54 on the big end... Back to the point sounds like a nice combo, I might change the cam if it was my car though, I would definately try to work the bugs out of this though before trying a carb or anything... good luck.

 

[Dark Knight]

did the dyno have a wide band 02 sensor?
double check the timing etc.. my AFR's like 17* initial.. you might need more..
77mph in the 1/8th sounds like it's crapping out somewhere... 94 mph is average for a stock car..

what RPM are you shifting at?

 

[SmockDoiley]

An 8.4 would be good for high 12's not low 13s. I'm not sure what the problem is since you are trapping up to 108. Obviously the power is there if you can manage those speeds. Also if you popped a 13.8 while missing 4th then your not doing too bad. You really need more runs to compare data because those 2 runs are so vastly different, you can extrapolate anything from them. You need a couple clean runs with good starts, and no missed gears. This is when you'll see problems. Have you actually run on the quarter before or is this all from guessing off 1/8th times. If your running 8.4 in the 1/8th but still running high 13.8s or 14's then you know you have a fuel delivery problem or something that is starving your engine. Get some good runs in and let us know then.

 

[5.0hatch]

Thanks guys. Heres what I tried so for. Did compression check across all cylinders and everything is where it should be. Next I put in new plugs, cap, rotor, and wires. Changed fuel filter, injectors and recalibrated maf. I know these 2 runs were completely different but the fact on the second run it only trapped 94mph kinda scared me and I didnt want to make another pass after that.

This has been going on for the last year. I can make one pass and it traps 108mph then the very next time it will do something like 98mph with no changes in between. I thought it was my 24lb injectors that were bad so I changed them out for my 19lbers and recalibrated my maf and that resulted in nothing.

As for as my fuel pump, it is showing no signs of being bad. But who knows, I guess i'll change it out and see if that is it. btw its a 190.

I'm a couple of hours from a shop that does custom chips, I wonder if it would be a waste of my $500 to get it dynoed and a chip burnt??

 

[NKau]

What kind of fuel pump do you have just out of curiousity?

 

[25thmustang]

What was the 1/8 mph on the first run. I had an 8.300 @ 82.7 in the 1/8 and went 13.05 @ 103.4...

Looks like there is a tuning issue there, maybe time to get it to someone who can tune it!

 

[Stump1000]

umm... maybe time to get someone that can drive it

 

[2000xp8]

Lose the 70mm TB, get a 65, get a real MAF like a pro m, then get a dyno tune for the Fuel pressure, and then try again.

I'll assume your maf is a C&L (because i think they are on the only ones to have a 73), either way, they rarely work right, some of the local shops by me won't even tune your car with a C&L on it. They suggest it's too inconsistant.

 

[5.0hatch]

1/8mile was a 8.40 on the first run, then I missed 4th right after that. My other runs from a couple of weeks ago were all in the 8.40s on street tires and I was running 13.20s@108mph with 2.0 60fts.

I don't think it's my driving. I always leave at the same rpm and shift at the same rpm everytime just to make sure that i'm consistant. But like I said it is nothing for it to drop 10mph from one pass to another with no changes at all.

Also my hp peaked at 5900rpms and i'm shifting at 6100 seems to work best. My timing is at 16 degrees and fp at 36psi. I picked up 25rwhp under the curve and 3 peak horsepower with those settings.

To get a dyno tune and custom chip I would have to drive 3hrs. and it is $500 to do it. Think if I go they would be able to find the problem?

My biggest problem is that I dont get how it can change that much from one pass to another. My last mustang I had was all stock except 3.73s and it would trap 101mph 90% of the ~500 passes I made in the car, this one is just giving me hell.

 

[5.0hatch]

1/8mile was a 8.40 on the first run, then I missed 4th right after that. My other runs from a couple of weeks ago were all in the 8.40s on street tires and I was running 13.20s@108mph with 2.0 60fts.

I don't think it's my driving. I always leave at the same rpm and shift at the same rpm everytime just to make sure that i'm consistant. But like I said it is nothing for it to drop 10mph from one pass to another with no changes at all.

Also my hp peaked at 5900rpms and i'm shifting at 6100 seems to work best. My timing is at 16 degrees and fp at 36psi. I picked up 25rwhp under the curve and 3 peak horsepower with those settings.

To get a dyno tune and custom chip I would have to drive 3hrs. and it is $500 to do it. Think if I go they would be able to find the problem?

My biggest problem is that I dont get how it can change that much from one pass to another. My last mustang I had was all stock except 3.73s and it would trap 101mph 90% of the ~500 passes I made in the car, this one is just giving me hell.

Can a c&l cause that much trouble? I always heard they can cause idle problems and such but never really anything like i'm having at WOT. I never changed it because the car idles perfect with no bucking are anything.

 

[NeQX]

My personal opinion is your timing and air fuel is def off, with that combo you should be pushing about 280-290rwhp, and trapping at about 106-109....I would suggest setting timing to 15* and fuel pressure to 40psi, then you can goto dyno and dyno with a/f ratio and adjust as neccessary

 

[Grn92LX]

5.0hatch, try a new fuel pump, get a 255. Do you have a FP gauge on your car so you can moniter FP during a wot pass? Don't listen to anyone that says to remove your 70mm tb for a 65mm, thats not the problem and 70 is ideal for your car. Funny how a 75mm was recommended for my car by Ed C Anyway, get a new fuel pump and go to the track again. I think its the problem. Only other thing I can think of, is a slipping clutch. Your tune is fine, the problem is a mechanical failure somewhere..

 

[Hissing Cobra]

If you've been trapping at 108 mph, then you're probably making more horsepower than the dyno was showing. I base this opinion on the fact that just about all the cars that trap that speed are somewhere between 290-320 horsepower (my brother's dynoed at 290 with consistent 12.50's-12.60's @ 108-109 mph.)

I see that you've got 3.73's in your rearend. Do you have any traction control aids? If your 60 foot times have been inconsistent, then you may want to look into those, if you don't already have them.

Drag shocks/struts, upper/lower control arms, and subframe connectors would be good additions if you don't already have them.

 

[5.0hatch]

Maybe I do have a fuel pump that is about to die. That will be my next thing to do. I totally agree that I have in the area of 300rwhp based off my trap speeds and a full weight 93 Hatch. Nothing at all was removed, still had spare tire and all when it trapped 108mph, even had 17" bullitts all the way around. Yesterday I took out the spare, jack and all loose items in the car.

suspenison is all bullitt and I have subframes and all adjustable control arms.

I always base my tunning on trap speeds since they normally dont change that much and they show how much power you are making. Its just hard for me to tune when it traps anywhere between 94-108mph without a single change.

The timing and fp is what worked out best for me on the dyno so it is for sure in the right spot.

I dont have a fp guage that I can watch while at WOT so that is out of the question.

 

[NKau]

May want to look into a FP guage like someone else suggested; nice to see if you're fuel pressure drops off once the fuel pump is warm, and it's just nice to have in general. I asked WHAT fuel pump you had before, because I've heard of people having problems with the Walbro's holding consistent pressure; that they drop pressure after running for a while. This would definitely explain your problem. You will obviously have problems with consistency/tuning if your pump isn't giving a constant flow.

 

[5.0hatch]

I wish I knew what kind of pump it is but it was in the car when I bought it. Also I never thought about the pump not pumping as good after it gets hot. I hope that is the problem, I wish someone had a similar problem to mine.

About the whole 70mm tb vs. 65mm tb. I've seen track results that prove a 70mm is better than a 65mm. I'm sticking with my 70mm. Ed C recommened me to get a 75mm also.