I've got a 98 coupe that I want to do a few things to. It already has some flowmasters on the back and a non-stock cold air intake. I'd like some advice as to which bolt on parts to do first, then second, etc plus how to determine what I already have. I bought the car in Oct 2011 and I believe I'm the 3rd owner. It's an A4 w/3.15 gears and runs very strong. The bolt ons I'd like to start with are long tube headers, xpipe, etc back to the flowmasters, and new intake and throttle body. So this brings me to a few questions. I won't be doing this all at once (not made of $$) but I've got enough saved right now to do some of it. Are the LT headers the best place to start? Or would I get a nice jump in performance if I got a new intake and throttle body? Headers now, intake later? Also, how can I determine if the previous owner might have already put on a LS6 intake? And how can I determine which throttle body I have now? Lastly, planned for the future would be a nice cam to give a bit of HP and cool idle sounds. Looking to get up to 400-450 HP eventually.

Last part of my questions concern throttle bodies. How much performance gain does one get by going to a 90mm vs a 92mm vs a 96mm vs a 102mm? Will all of these fit on a LS6 or should I bite the bullet and spend the $$$ for a FAST LS intake? Is the price difference worth it for the HP gain? Do the intakes support different sizes of throttle bodies? Can a used intake off a Camaro or Firebird be used on the Corvette? Just a bunch of newbie questions.... Sorry. Back in the day when I had my 67 Chevelle SS396, I didn't have to worry about all this stuff the way you do now. Seems a bit more complicated now with all of the computer stuff and tuning.

And the final question is regarding tuning. When to get it tuned? After the headers are installed, or wait for everything to be installed then do it? Should it be tuned multiple times? Thanks and I appreciate your patience. That was a stupid long post.

 

Headers, cam, heads if you can swing it will get you to 400+rwhp, with a tune. intake and throttle body are the last things i would do, too much cash for little gain. It will run with headers, but to run right you need the tune.

 

Do it all at once, or wait.

After each major mod, a new tune should be done.

So if you do LTs, exhaust and CAI, get it tuned.

then when you do the TB and Intake, get it tuned.

Tuning is a key to get the most out of any bolt on mods.

Good Luck

 

I have walked in exactly the shoes you are wearing. Here's my suggestions/observations based on my own experience:

1. From your starting point, LT headers (with your CAI) and an aftermarket exhaust should give you about 345-350 rwhp and 340 ft/lbs of torque. Plan on spending $2,000 or more (depending primarily on the cost of the LT headers - which can run from $1,100 to $1,800 -or even more if you are buying an exhaust system) if you have someone else do this install. If you have your installer port your existing intake manifold and throttle body (rather than upgread them), you will accomplish roughly the same result, but save several hundred bucks. (I bought a Forum member's Z06 Ti exhaust for $350.)

2. Next step: upgrading your heads and swapping in a mild cam should net you about 410 rwhp and 400 lb/ft of torque. (Cam selection is key: if you later intend to add a blower, then be sure the cam you select is compatible with the blower; otherwise you might need to change out the cam (again) when you put in the blower). Plan on another $3000+ for the heads/cam install. Unless you live and drive in really cold weather, change out your thermostat (to, say, a 160 degree unit) at this same time. Also, adding in a 2800-to-3600 stall converter might be advisable at this time, or at the worst when doing the next step (#3 below). If so, that's an additional $1,000 or more. In any event, you'll want your tuner to also tune your A4 transmission -firmer shift points will complement the power gains you get from the engine mods.

3. If you ultimately determine to add a supercharger, then be sure the cam you select (in #2 above) is compatible with the blower. Otherwise, you would need to trade out the cam for one that maximizes your blower capabilities. If/when you add in the blower, be sure to also add a transmission cooler. A blower will cost you $6,500 to $7,500 installed.

In all events, follow AU N EGL's advice and get a dynotune (a) after the LT header install, and (b) preferably after each other major upgrade. If you use the same installer for all upgrades, he might give you a major $$$ break on the cost of the tunes.

Best regards,

The Lizzard

 

Thanks gentlemen for the tips. I need to find me a good tuner (locally I hope) or maybe I could use CoW? Have to dig into that a bit further. One more question. Should I try and take on the LT install myself? The car is not my DD and if it has to sit for a week or so while I get my s**t together, that's ok. I really like wrenching myself, but have never taken on a header install. My question would be how high do I need to get the car off the ground to easily do a header install? Again, my appreciation for your comments, advice and guidelines. You guys ROCK!!

 

Start with a hi stall converter first. You won't be able to get the max out of your power adding mods with the stock converter. Excluding nitrous a hi stall T/C gives the best bang for the buck on an automatic.

 

You'll be lucky if you can notice a change with just the intake. Maybe a little different throttle response but it's maybe a 5hp gain going to a LS6 intake. Personally, I don't think headers give a huge change either that's super noticable. I'd think you'll notice it more along the lines of spinning the tires when you didnt expect it or it hitting the next gear a little quicker than you were expecting (hitting the rev limiter quicker in a 6-speed). Heck, the headers and tune only give about a 10% power increase.

As just mentioned, a converter would likely give way more SOTP improvement compared to headers or an intake.

400rwhp to 450rwhp is a big target range. You might get close to 400rwhp without heads. Not 450rwhp though. But then I'd want to see at least 425rwhp with heads and a cam.

 

A 90mm or 102mm TB will NOT fit an LS1/6 manifold. Your stuck with your STOCK 78mm. You can port it but,, the MAF and Throttle Body are NOT your HP limitations. The LS1/6 TB is a THREE BOLT assy. The LS2 is a FOUR BOLT assy.







LS2





LS1 vs LS6 manifold:

LS1 with winged bottom:



LS6 FLAT BOTTOM:



I installed a home ported FAST90 and Home ported 90mm Throttle Body on my 02 ZO6. It has Patriot stage II heads, Comp 245-245, 610 lift at 114 lsa. With a professional tune, im in the 450HP range

NOTE! Once you pass the 400hp mark,, you will need to start beefing up the drive train!

Headers... You can find XS Power headers for LESS tham $900. I installed them in the drive way on jack stands on a C5 and C6. The C6 is a SNAP!





Any modification that you do that worth any good HP increase will or should be followed up with tuning! When you change that can,, your going to need new BIGGER injectors and they must be tuned in.

Save your cash, get as many mods together that you can easy afford. Example and my recommendation:

-Low cost headers OFF SHORE or used LT/SS Headers
-High flow Cats and and an X pipe
-LS6 /2001+ manifold (if you dont already have one)
-Ported TB
-VARARAM
-TUNE!!!!

With the above mods on my LS6, I was at 390 HP/375 Tq. The LS6 has better heads and a little bigger cam. You will easily be in the 350-360 HP range.
Just tuning the PCM will give you a very good SOTP performance gain with improved transmission shifting and shift timing!

BC

 

if you're looking to get off the line. A stall convertor will make the most difference on an automatic.

 

Bill

TPiS90 fits on the LS6 intake http://tpis.com/parts/view/39

 

Keep in mind if you already have an ls6 intake the conversion is only $350. That $799 price is if you don't have a core and buy one outright.

 

I would suggest the LG Street Series for fit and performance. They slide right in and are easy to install.

Here is a good DIY http://www.ls1howto.com/index.php?article=29

Headers http://forums.corvetteforum.com/c5-p...-shipping.html

I would suggest the Vararam for your intake. They perform

 

Just realized you were local. PM me if interested in headers and intake. I can work it to offset the tax cost. I have a suggested tuner as well for you.