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View Full Version : What the hell is going on?



dirtybird91
10-18-2002, 07:52 PM
My SC runs good most of the time, but sometimes it runs STRONGER like a bat from hell!!! What causes this?? It could not be the temperature since it is pretty much the same around here. Is it the computer??? I noticed it at the track too. It is stock, and I once ran a 16.5 and then I ran a 15.4 the next run!!!:D My car is possessed dude! I think I will name it CHRISTINE!:cool:
dirtybirdie:eek:

455Poncho
10-18-2002, 08:13 PM
Mine is the exact same way, i hope someone can explain what the hell is up with it

dirtybird91
10-18-2002, 08:24 PM
What kind of setup are you running dude?? What year is yours, and is it a stick or auto?:confused:

Robert Kohlman
10-18-2002, 11:55 PM
The two things that seemed to make my car act in such a manner are the fuel pressure regulator vacuum fitting blowing off and not working properly. I had to put a new fitting on it to keep it from blowing off. The car literally felt like it had 50 less HP when the line came disconnected. Maybe your fuel pressure regulator is not working properly all of the time? I'm thinking that 35-40 lbs. at idle is good fuel pressure and it should increase 1lb. per 1psi of boost. Easy to check with a fuel pressure gauge hooked to the schraeder valve on the fuel rail.

Another candidate is the supercharger belt slipping. If you go to a smaller SC pulley I suggest getting a 3" pulley on the tensioner because that makes a huge difference in the slippage of the SC belt. Even though you only notice the slippage a high rpms it is slipping much of the time when you are running the engine under load. You can usually tell when the belt is slipping at high rpms because it will squeal and you can see your gauge peak out and drop back while it is slipping. Another tell tale sign is black powder on the snout of your supercharger.

These are just two things to check.

Bob

dirtybird91
10-19-2002, 12:08 AM
Thanks John
I am running a new belt on my "stock" pulley, but I think they can still potentially slip.
I will be putting a gauge on my fuel rail soon. I also suspect that the injectors are not the cleanest.:(
I still can't help but think that the computor plays a role in this somehow. I don't know if it gives different HP output due to the data that is collected or what.:confused:
The car is running like a raped ape today!:D

455Poncho
10-19-2002, 02:40 AM
I have a stock 90 SC with air silencer removed and a freshly rebuilt motor. I dont understand it either, just depends on the day. Gteched my car about a month ago, ran 15.9, which at my altitude should be right for a stock sc. Gteched it again last week and it ran 15.3, with someone in the car. Same time, 2 runs, one after another in opposite directions. Sometimes it feels like the car cant pull from minivans, then i raced my buddy's 91 cobra 5 speed, (also stock), and he beat me by about 2 feet up to 140 km/hr. He shoulda killed me i would think. I used to think it was in my head, but its good to see someone else has the same problem. And im gonna head to the junkyard to try and grab that bigger tensioner, will an alternator pulley of a normal 3.8 bolt on??

tbird88
10-19-2002, 10:36 AM
I live on the upper Texas coast and figure (also known as ~~~-u-me) that the current barometric pressure & air temperature have a lot to do with how my car runs at times. When I drove my 88 Turbo Coupe during the winter with a high pressure system sittin' over our part of Texas the car seemed (~~~-u-me) to run a lot stronger.

'bird

dirtybird91
10-19-2002, 05:34 PM
I'm glad to hear that i'm not alone here Wynn. I'm not sure what sea level I am at and all that kind of thing, but I must have Gremlins in my engine or something. I dont know if the (~~~-u-me) is an issue here or not.:confused: That is something to think about for sure! I hope you were happy with the SC top i sent you a few months ago.
:D
Poncho its funny, but I also ran with a Cobra a few years back on the streets of Tucson when I lived there. I thought he was going to mop the floor with me, but I was in his a$$ up to 80mph or so. I jumped on him from a rolling start at 15mph. Then we ran into a red light. That episode impressed the hell out of my friend who up to that point talked negative about SC's.:D
dirtybirdie:eek:

XR7 Dave
10-19-2002, 07:27 PM
It does mostly have to do with atmospere conditions and engine heat soak. I noticed that consitancy improved DRAMATICALLY when I went to a front mount intercooler (eliminating heat soak pretty much). Our cars are also tuned quite rich from the factory, so if the air is dense out, it will not only help you get more air into the motor, it will also lean out the motor giving it a whole new attitude.

Most SC's are dialed in at around 10-11:1 under boost, whereas max power is achieved at about 12.5-12.8:1.

dirtybird91
10-19-2002, 07:34 PM
Dave,
I wish I had the beans to afford that front intercooler setup. I envy you dude! Magnum Powers is offerning their version for about $1500.00, but I would wind up in divorce-court if I tried to rationalize that to the wife after she let me get away with a new house and car.:(
I am going to get a second job just for the SC fund!:D What you are saying sort of sounds like what "t-bird 88" is saying in a way too, and I wish my car had a stable "personality" all the time.
dirtybirdie:eek:

fastsc92
10-19-2002, 08:29 PM
if you guys are going by what time you run at the track...then its all the driver. IF you get a good 60 time...then you'll run a good et. Every .1 sec off yuour 60 foot time is .2 sec off your et at the end. So if you run a 1.9 60 foot, and you hit all the gears inbetween, you'll have a low 14 sec run. If you get a 2.2 60 foot and a good run you're et should be around15 sec. Its all on how you launch and if your tires are spinning. A faster MPH doesn't mean a fast run. I ran a 14.211 and my mph was only 94.27.....thats very low for that time. The only reason the mph was low was because i got a 1.90 60 foot and a .6 reaction time. So its not always the car..its the driver....plus when the motor is cool its the best. I ice down the intake, SC top, IC tube, and IC and my Ic fan in between every run. Helps quite a bit. Hope this info helps../..good luck.

Tazer999
10-19-2002, 10:41 PM
HIGH mph equals spinnage

LOW mph means good launch

RT means diddly ****

tbird88
10-20-2002, 12:08 PM
Originally posted by dirtybird91
I'm glad to hear that i'm not alone here Wynn. I'm not sure what sea level I am at and all that kind of thing, but I must have Gremlins in my engine or something. I dont know if the (~~~-u-me) is an issue here or not.:confused: That is something to think about for sure! I hope you were happy with the SC top i sent you a few months ago.
:D


Me, i'm chasin' down a little gremlin that rears its ugly head after I first crank her up. Idle down the street, practice a little bit of profiling and next thing ya know she starts goin' rumpety-rump and acts like she's gonna die. Sounds kinda cool but that ain't the way it's supposed to be. Super sharp throttle response but a major pain to keep at a steady idle, either a bumpy 500rpm or a smooth-as-silk 17-1800. Gonna look at the IAC today if I get time.

Very happy with your service on the top, great deal too. It lives in the Great Lakes area now, kinda looks a little different than stock though after I got ahold of it if ya get my drift...heh heh :)

'bird


http://www.datarecall.net/~tbird88/index/parts/alum/bs519F6th.jpg

curse
10-20-2002, 12:29 PM
im with XR7 Dave when my engine is hot it feels sluggish and very heavy but when its cool its strong when I ran my 14.9 run on my 3rd pass then I couldnt get better than a 15.4 same r/t and same 60 foot 2.1-1.9. I let her sit and cool and time when back down to 15 flat. Just my .02. I also wonder how much my elevation plays a role on my power loss Im at 4500 elevation

Deep6
10-20-2002, 05:10 PM
He's up 5000+ft. Yah, the air is thinner. i wouldn't be surprised if your car was 10% more powerful at almost sea levels.

curse
10-21-2002, 04:01 PM
i would love to run at sea level. Stock 98 and up cobras run 14.9s here wonder what i would do at sea level

dirtybird91
10-21-2002, 05:30 PM
I happen to own a 2000GT Mustang 5speed, and I ran a 14.6 at the track in it before it was even broken in. I have a hard time believing that a Cobra would only run a 14.9:confused: Gee, elevation must be a bitch where you are from.:eek:
dirtybirdy:eek:

Aaron Gott
10-23-2002, 02:32 PM
I think you should name it Amanda... for me

dirtybird91
10-24-2002, 02:28 AM
Well, maybe i'll name the Mustang Amanda, but my SC is definately Christine "like the movie":D

Aaron Gott
10-24-2002, 04:33 PM
does your mustang let somebody else "drive" her... try to run you over, and just go downright crazy? (all while making some weird noises)

dirtybird91
10-24-2002, 07:39 PM
Well,
The Mustang is a very gentle, and predictable creature. It only gets pissed-off when I put the big 11 inch jungle-boot down hard! It then becomes uncontrollable.
The SC on the other hand is unpredictable because when I stomp down with the ole jungle-boot I never know which personality is going to emerge.:( It might react violently, but it may not even jump into passing gear!
dirtybirdie:eek:

Aaron Gott
10-24-2002, 11:01 PM
I see... well, cars aren't always a good analogy for girls... I can live without girls... but not cars. My car broke (up with me) four months ago and I am still hurting... my girl broke up with me a month ago... and I'm pretty much over that

dirtybird91
10-24-2002, 11:06 PM
I can't make a decision on that one dude. I was without my girl for a while and lost 10 pounds that I didn't need to loose!:(
On the other hand, if you keep the SC good and shiny you will always have a girl!;)

Aaron Gott
10-24-2002, 11:40 PM
well I was sorta half serious... starting not to think about it all the time... but I am still heartbroken. I haven't lost weight... I've gained weight! (It is kinda nice to get some different assortments of ~~~ though!) I don't need an SC to get ~~~...

Aaron Gott
10-24-2002, 11:41 PM
by the time I get to them, they are too drunk to see my car...

dirtybird91
10-24-2002, 11:42 PM
Yeah,
I know what you mean man! It is sort of nice to have an ~~~ assortment!:D