Hey guys, I plan on doing a lot of work to my car within the next year, and had a few questions before I do them.

First off, I have a 94 Z28 with a Powerdyne Supercharger (6psi), MSD ignition/coil, FMU, and an auto trans. I took it to Bristol last week and ran it for the first time with a disapointing 14.104 @ 99.1mph in the 1/4 on stock street tires with lots of spinning. So with some Mickey Thompson drag tires order, I decided its time for more upgrades.

Anyways, after doing some research on a few mods that I was going to do, I only came up with more questions and hope to have some of them answered here.

Torque/Stall Converter
I was doing some reading on putting in a big cam and found out that on some cams, it requires a torque converter. After doing some research online, the one question about a Torque converter I had is, How does a Torque converter work in terms of driving around town. From what Im getting by reading stuff online, it will basically be like being in neutral and let you rev up to a certain RPM before finnaly grabbing and letting you launch off the line. My question is how will this affect me in driving through town. Will it always make me have to rev up to 3k RPMs (if I get a 3k Torque converter) before leaving say a traffic light (making me bark my street tires) or is there another way? Or have I just been reading and understanding wrong about what a Torque converter does.

Gear
I was wanting to put in a different gear and wanting some suggestions on what I should get. Keeping in mind I have an auto trans. I was looking at putting in a 3.54 or a 3.73. With talking with a couple people, they said it would make a massive improvement to my 1/4 times, but would sacrifice a lot of top end. Can someone explain a little about what the gears would do for me.

Pulley's
I was thinking about also getting a new set of underdrive pulleys but after doing some reading about them, seen that they make the crank pulley turn slower (which my supercharger pulley is attached to). With that pulley turning slower, would that not make me lose a little boost off my supercharger?

I also plan on getting some long tube headers, cutout, and a new cam.

Thanks
~Dasstrum

 

Looking at you 1/4 mile time, your supercharger seems to be hindering your engine rather than helping it. Trap speed is mostly a function of engine power, regardless of traction problems. With 6 # boost you should be pulling trap speeds over 115MPH. Rather than worryng about cams, tires, and gears, I would get the car tuned and get the engine to make some power. Something is way off and you need to address it.

All autaomatic transmissions use torque converters, the only differnce is the stall speed. If you engine were working properly, your stall speed should have increased by about 800-1000 RPM due to the extra torque, and best left as is.

If you plan to use a high stall (loose) torque converter around town you will need to get an additional transmission cooler to keep the tranny fluid from cooking itself due to the extra slippage. Driving around town feels about the same with either converter, it is when you go to WOT that you notice the difference.

Pulleys do not make the crank turn slower, it is the size of the pulleys that changes the speed of the crank driven accessories. With a supercharged engine, they should be the least of your worries.

3.73 gears with a limited slip would help.

 

Pete, I sent you a private message when you get a chance to check it

 

like pete said i would definatly get it tuned first cause something isnt right with your engine. The next mods i would do is gears, headers, and the stall. For the gears i would most definatly go with 3.73's they dont sacrifice top end that much and give u alot more power out the dig. Next headers, headers are important becuase they restrict you exhaust flow alot and make ur engine breath better, these are also important cause ur s/c . Finally the stall will make a big diff in ur times, dont go to high with the stall nothing above 3200 specially since its a daily driver but you will definatly need a tranny cooler

 

Ok, im wondering what you guys mean by getting my car "tuned". Are you talking about new plugs/wires and all the basics? Because I've already had that done when the supercharger was installed. The only thing that I have noticed is that the car seems to be running rich, but I dont think that would have that big of an effect on the 1/4 MPH time.

What should I do here, im a little left in the dark about this, and now im a little worried about my car and hoping that something isn't going majorly wrong with it.

Thanks
~Richard

 

when you get your car your computer is specifically tuned for ur stock engine like rpm range , top speed limiter, air to fuel ratio ect. so when you do major upgrades you need to get ur car tuned to change all that and since you have a supercharger you REALLY need one because you drastically change your air to fuel ratio and arent getting the right mix

 

The best place to get a tune is at a local place that has a Dyno. They will get the most out of your engine without hurting it. Tuning it is basically telling you computer what mods you have and how to use them correctly. Why only 6 psi. You said your intercooled you could run more boost safely without too much fear of detonation. Once you get that done you will be amazed the difference.

 

Powerdyne superchargers only let you go up to 6 psi without buying a bigger pulley (can go up to 9 psi). I dont plan on running 9 pounds till I do more work to my engine. And no, I didnt say I had an intercooler.

And pete, as for my 14.104 @ 99mph, I just remembered when I made the run, I did not have my T-Tops in due to one of them blowing off on the way down to the track. My luck! (dont let someone else put in your T-Tops for you, they might forget to latch one)!

Anyways, not having the t-tops in when I made the runs might have a big part in my times too, along with running rich dont you think?

 

The open top would slow you down a bit but nothing like what we are seeing. A stock Z28 will run those times. The PCM needs to calibrated to account for the supercharger, and possibly your fuel delivery needs to be upgraded. Contact PCM For Less, if you dont have access to a dyno tuner in your area. They can send you a propely calibrated PCM on an exchange basis. www.pcmforless.com

Your trap speed suggests around 250 RWHP. With 6# boost, the RWHP should be around 340.

Is you transmission holding OK?? Any signs of slipping??

 

My transmission seems to be holding just fine, I plan on taking the car down to a good garage in a couple days and have them see what would possibly be wrong with it.

And the closest dyno that acually does tuning is 3 hours away. Waiting on a friend to finish with his mx6 complete rebuild (about 3-4 more weeks) before we both take our cars down and have them properly tuned all the way.

Thanks for the help, i'll keep you updated

~Richard