Great forum...been reading for a while and decided to post. I have a stock 98 vette that I bought new. Thinking about going with a blackwing and exhaust. Heres the question. I have a Harley and when I changed pipes and put in a less restrictive air filter, I had to recalibrate the fuel injection so it would run right. Is this true for FI cars as well? I have not seen anyone talking about it, so assume it does not have to be done, but just curious. Also what are the benifits of an x-pipe? Thanks in advance.

 

The corvettes have "learning" computers. You can change the air flow, within limits, and the computer will learn the new fuel settings after driving about 50-100miles.

An X-pipe is used to smooth the flow of exhaust between the two branches of the exhaust system, equalizing pressure. The stock system is an h-pipe which requires air to make a 90 degree turn (which is doesn't like to do). X-pipe reduce that angle, which will theoretically get the exhaust out faster. It was change the engine tone, may add a small amount of horsepower.

BTW, Welcome to the Forum
Chris


[Modified by chaase, 12:02 PM 10/14/2003]

 

Welcome to the forum :hurray: You'll find it a great help.

This is what I've learned, and it applies to the '97s and '98s. They come programmed rich from the factory. The fuel injection 'map' in the powertrain control module (PCM) has been programmed from the factory with rich setting for some reason. If you look at the rear bumper of your car after some hard charging, you'll likely see the 'black mist' from the fuel. The PCM can learn, but is limited and is based on the original programming. I've studied MAFTs (mass air flow translators) and adjustable fuel pressure regulators (AFPRs), as suggested by 'knowledgable' people, and found out that the MAFTs will be 'learned out' by the computer for the normal driving parameters but will help the rich condition during wide open throttle (WOT). The fule pressure regulator will help some, but reducing fuel pressure impacts the spray pattern from the injector...and I personally don't want that. I've opted for getting my PCM reprogrammed until I can afford the software to do it myself. I've just installed it in my car and can't report on results as of yet.

Now, the Blackwing question. This is highly recommended for our year vehicles since it helps to lean out the mixture and is really needed since the stock airbox is built to meet noise requirements as well as flow...they balanced it out. The Blackwing is supposed to help the earlier years more than the later years, so it should be a real SOTP power increase for you (12-20 RWHP). I plan on getting one later since I DO think it is better than my modified stock box for numerous reasons....but I had to check it out for myself.

The x-pipe primarily helps in reducing resonance when an aftermarket cat-back system is installed. With my Borla stingers, resonance is VERY noticable and the x-pipe is on my list of things to get. HP increase is low (maybe 1-2 RWHP) and not worth the cost if HP is the only reason. The biggest HP improvements from simple bolt-ons come from headers and intake, Blackwing being best for the money IMHO, and the Donaldson (Blackwing) filtration material should be better than anything available on the other cold intake systems.....Donaldson is a filter leader, do a search on Google. After those two changes (headers and filter), a tune to the PCM is suggested as well as a 175-180 degree thermostat. During the PCM tune, the tuner should reduce the cooling fan turn-on temps. so you can take advantage of the cooler thermostat. The list of mods go on from there. Be careful :D Mod fever is VERY contagious and, in my case, gets worse with time. If not for my significant other, I'd be living in the garage with my wrenches in hand :reddevil

BTW, if you have an automatic, and don't have the performance transmission (3.15:1 ratio), the next mods typically suggested are a 3.42:1 rear, 3000 stall torque converter, and a Transgo shift kit. Although, IMHO, the shift kit is a cheap way to start. If you have an M6, just ignore my rambling :chevy


[Modified by TopCat, 12:30 PM 10/14/2003]

 

Thanks for all the info....I can see how modding can be addicitive. So if I want to do a blackwing, x-pipe, and exhaust do you think I need to mess with the PCM? I just want the car to run smooth w/o backfiring on deceleration, etc. Any good exhaust out there w/o resonance?

 

You don't need to mess with the PCM. Most people on this Forum believe that an ls1edit tune from a good tuner will give you extra horsepower. I will get one when I do my mods..

As for exhaust there are lots...
Corsa advertises no resonance on their systems as well as a few manufacturers.

Chris

 

No need to worry about the PCM, it'll do just fine. And, I disagree with the previous post that the PCM runs "rich" from the factory. It runs rich only at WOT, by design. At those power settings you want to run rich to eliminate (or at least minimize) detonation. You'll lose more power due to the PCM pulling timing out due to detonation than you'll ever pick up by leaning out the mixture at WOT.

When you aren't at WOT (the vast majority of the time) the O2 sensors provide feedback to the PCM on whether to lean or richen the mixture. My M6 gets better than 30 mpg on the highway, so she must not be running TOO rich! ;)

Hope this helps, and have a good one,
Mike

 

Mess with the PCM if you want to drop your coolant temps (through fan temp on / off adjustment) and shift changes (if you have an automatic) and if you want more consistent A/F ratios across the board. As I mentioned, it's the 97s and 98s that run rich, and it is worst at WOT. But the most power is achieved not at the stochiometric A/F ratio of 14.6:1 but at a richer 13:1 A/F ratio. For @$250 you can send your PCM off for programming, with 60 days of free updating, and can get an extra 10+ RWHP.....at least that's what I've read. Not as good as real-time tuning on a dyno, but all I can afford.

I've got my preliminary dyno results, and I was running an A/F of 11:1 at WOT (after the cats) and only 293 RWHP (expected closer, if not greater than, 300). I expect to get 20-30 HP over that with a Blackwing, cat-back, 180 t-stat, and LS1 Edit added. Don't know how soon I'll get to the dyno, but I'll add it to my sig when through.

There's a lot to the LS1 Edit; more than power tuning. If you've got time, you can download the instructions at their website and read through it to get a flavor for what's possible. To me it's as important as having the right gap on the spark plugs :cool:

but that's my opinion.....one of many you'll find here. You're doing the right thing by reading all the info first.

I had others tell me the approach to take, but I had to learn myself. Now I know they were right.......intake (Blackwing), headers, exhaust for sound and looks primarily, then you have to start with more time-intensive mods (heads/cam, nitrous, turbos, superchargers, stroke/bore cubic inch increase) which will then be followed by tranny upgrades, since something will surely break there once you start upping the horses :D

I've heard the Corsas are good exhausts for avoiding resonance. Do a search here on exhausts and you'll find all sorts of info., and many recommended exhausts for avoiding resonance.

:cheers:


[Modified by TopCat, 3:20 PM 10/14/2003]

Oh yeah.....don't forget to install a column lock bypass (CLB) and to change your battery to an Optima yellow top!!!!! Search the forum,,,,,you'll see why!


[Modified by TopCat, 3:23 PM 10/14/2003]