Anyone have an idea of an average 1/4 mile time for a '94 Z-28? Basic specs LT1 Engine w/Auto Transmission and 122,000 miles. Only mod's I've installed are: Jet Stage II performance Computer add’on (for auto trans) and replaced the exhaust with a 80 series flowmaster (3” in and dual 2” out). Just ran the car the other day and best it ran at was 15.4sec @ 91mph, this was shifting 1 -> 2 -> D.

I've heard this car just stock should be putting up better numbers but just can't figure out why it just isn't. Also another thing I noticed that was really weird was after running the car 3 times in a row my Temp was normal (below middle) but for some reason my driver side power windows started cutting in and out. Had to let the car sit for a few minutes before it started working again, I check the voltage and it was sitting around 12-14 volts.

Pretty much I'm just confused now. But at least the car isn't sputtering out like it was when I bought it.

 

I haven't taken mine to the track yet, but I've read in numerous places that a bone-stock '94 Z28 should run about a 14.2 @ 97 MPH.

 

I ran a 14.4@98MPH stock without the muffler when it was an auto. It had 133k+ miles on it.

 

window motor is getting old. sometimes you will have to let it cool off before you can move it up and down. go to shoebox's webpage to learn how to put a new one in fairly easily. www.shbox.com

if your still running a stock exhaust system back to the muffler, you really just changed the sound of your car by adding the flowmaster.

your car is getting old and a lot of miles on it. whens the last time its had a really good tune up? might want to start looking there for a little bit of power. i havent really heard anything good on the jet chips, someone else will have to fill you in about that thing. i dont know enough about them. only that if you want any real computer enhanced performance, get a custom tune for your car (madz28.com for example).

 

Well, first off, the power window issue shouldn't be related. The 2 main causes I have seen are the switch itself, which can either have a bad contact or the rocker switch cracks, or (dare i say) it is the motor going out. I have heard of cases of a bad ground, too. So do some investigation.

That isn't the worst time for a car with 122,000 miles! It sounds like (i could be wrong) you haven't taken it to the track before, so practice will help too. I took about a second off my time with practice. What was the rough running complaint before? A good tune-up wouldn't hurt if you haven't done so already.

 

when mine was bone stock with 150000 miles on it i turned 13.8s and bone stock with 100 shot turned 13.1 at 107

 

Ok, heres some ideas that would be very likely.
Fuel Filter!
Plugs,Wires,Coil
Opti Spark(maybe)

There would also be a few other sensors you could check. Such as the MAP, IAT, MAS. And if all else fails do a compression check.

Also if your timing is advanced to far from the tune and its starts to detonate it could slow it to a crawl.

 

Well so far the window hasn't gave me any other problems, just only that once. As far as running the car this last Friday was my second time taking it to the track. The first time I took it I had problems where it was basically just loosing all power once I hit about 80-87mph and tripping the check engine light, but was unable to figure out what was causing that. Pretty much since I bought it this is the list of stuff I've done.

- oil pump
- fuel filter
- distributor
- water pump
- spark plugs
- spark wires
- MAP sensor
- O2 sensors
- brake pads
- battery
- oil (mobil 1 – ever 3k miles)
- cut the cat off
- replaced exhaust with flowmaster 80 series
- K&N air filter
- new tires (fusion brand)
- Jet Stage II performance computer module,

I know theres probably some more parts I've changed just can't remember them off hand. But his is the most recent changes.

 

I was running 14.0s @ ~98mph with basic mods -- before headers/ORP/Cutout, 1.6:1 RRs and valve springs. Motor would lay down after 5100rpm due to weak springs.

 

I ran my '94 auto z28 for the first time 14.4 @ 96.7mph on street tires, with the only mod being flowmasters, and 128,500 miles on the car and 4,500 on the motor, in the hot hummid weather of June in NC.

 

mine went 13.8@100 with 90,000 or so miles on it. I wouldn't try to do the shift yourself thing, it will work a lot better if you just put in in d and go. I wouldn't use that jet trans thing either.

what elevation is your track?

 

What is your track elevation? My 1995 z28 with bolt ons, mac headers, mild stall and mad28 tune ran 14.6 at 95mph but thats at 4500 feet above sea level. Ive seen cars that run in vegas come to utah and drop .75 to a full second because of elevation.

Shawn

 

hmm not sure about the elevation here's the website for the track I run my car at. Thunder Valley (oklahoma)

one thing I'm probably going to go ahead and try, is to take off that jet computer module and replace the ODBI computer with a new one (or one that I know is working) I'm thinking some of my problems right now are coming from the computer, before I put that Jet module on it was really running like crap and throwing check engine lights but when we'd hook up a scanner to get the error code there wouldn't be one. All that when away when I put this jet module on.

 

Don't shift manually. Like the other guy said, put it in D and go. 4L60e's can't handle it and build too much line pressure. Let the tranny do the shifting. It will be dead on every time. Try preloading to about 1200 RPM's with your foot on the brakes. When the light turns to the last yellow, nail it!

 

lol, dont go throwing away the computer just yet. do you have a laptop or a friend that has a laptop? if so, buy some cables to hook up to your pcm and get datamaster. then you can do a few scans to get some information from your computer to see how its running (will also pick up your trouble codes at the exact point they hit). dont just go throwing money at it if your not sure what the problem is. and if you do get the datamaster, post the results on here if you cant read the results and see if someone can help you read it. maybe might give you a clue on where to start looking for problems. BTW- if there is something wrong with your tune (i doubt this is the case), it can be retuned. you dont have to trade it in for a new one.
also, as mentioned before, dont manually shift your auto. use D, hold down the brake and keep it at ~2500 rpm for launching.