I currently own a '91 coupe. Within the next year I plan to purchase a 2005 coupe, most likely with the F51 suspension package and an Auto Trans.
I Know very little about Chevy's new 360ci all aluminum small block. I have heard that Chevy did a pretty impressive job of wringing horsepower out of this engine, while still retaining a high degree of reliability.
My question is this; what can be done to find an extra 10 - 20 hp / ft lbs of torque without spending large sums of money or harming the engine?
Does this engine respond well to a K&N filter? Or does it make little difference? What fuel pressure works best in an otherwise stock engine - stock, or slightly modified? I like the Flowmaster Cat Back system I put on the '91. Does this engine respond well to such a system - or a different system? Doug Rippie reprogrammed chips do a very nice job on the C4s. Does recalibrating the "chip" on the C6s have the same impact?
I guess, in essence what I am after is maximizing the potential of an otherwise stock engine.
I would be interested in learning from anyone having experience - either good or bad - with any of these ideas.
Thank you in advance.
Glen

 

A catback and intake filter swap should easily gain you 10-20 rwhp for roughly $1000 - $1500 give or take. The preferred catbacks seem to be Corsa, B&B, Borla and Magnaflow, in no particular order. BTW The LS-2 is actually 364 ci.

 

Some say that, others don't.

Headers are the easiest way to pick up another 20-25 RWHP.

 

I have wrestled with the idea of adding headers to my '91. So far, I haven't because I really don't want the noise on longer trips. I know they can add power, but I'm not ready for the power / noise trade-off yet.
On the other hand, I have also heard that C6s are so quiet, that I figured they would respond well to opening up the exhaust a little bit. Again, I haven't bought the car yet. Just laying the groundwork for what I would be willing to pay "extra" for whe I start searching the net for the right car for me.
The C4s respond well to carefully reprogrammed chips, increased fuel pressure, and opened exhaust systems. I was just wondering if the C6s responded as well to these smaller modifications.
Glen

 

The C6 doesn't have a replaceable chip like the C4, you have to re-tune the computer.

Some have added headers with stock mufflers and say its not loud.
I had headers installed with my Corsa mufflers and its not loud at all.
If you add headers with some other mufflers you might need ear plugs.

 

Something in particular about the '05? Make sure you're familiar with the issues the '05s had ... and that your car has had everything resolved satisfactorily.

 

A header system like LG Pros, DynaTechs, American Racing or Melrose will easily add 25+ to the wheels. And none of the headers mentioned will appreciably add to the noise levels. Especially the Dynatech or ARH headers because they have thicker tubes. With the LG header they have a thinner tube wall and you can actually hear the exhaust gases impinging on the tube walls, its like a slight ticking noise. The only time you will hear more noise from your exhaust is when you change the rear muffler section. If you want a decent exhaust but low on noise find a used Z06 Ti system which performs very well. A recent head, cam and header system netted 437 to the wheels on a 2002 Z06 using a rather small cam exhausting through the stock Ti exhaust.

 

Get a tune, with or with out the CAI and aftermarket exhaust it will give you a 10-15HP gain. My 05 Z51 A4 Vert Dyno'd at 331hp and 335ftlbs pure stock after Halltech Stinger intake and GLH CAT back exhaust it dyno'd at 334HP and 336ftlbs after a Chuck COW tune it Dyno'd at 344hp and 344ftlbs, the cheapest of the 3 mod was the tune, you make the call.

Couldn't find the dyno sheets for the stock and first set of mod but here's the dyno after the tune with the CAI and exhaust.

The biggest change in the dyno chart after the tune was in how quick the torque comes on. The stock tune didn't let the torque come on until 600-700 higher, also as part of the tune the shift points and shift firmness is adjusted so as to allow, lets say, for more spirited acceleration and much faster shifting, enough to chirp the tires on second and sometime third gear.

 

Thank you for the information about the headers. I am getting a little old I guess. I still think of headers as they sounded back in the '60s and '70s when I was a "youngster." They were loud - even with mufflers!
I did not know the C6s didn't have replaceable chips. Are the stock computer settings optimal for the type of minor enhancements I'm thinking of?
And Sven, I was under the impression that the 2005 was a pretty well sorted out car, with the exceptions being delamination of the roof panel, and apparently some difficulty with the radios. Are there other issues that were common to this model? In particular, my heart is set on a Daytona Sunset Orange coupe with the better brakes of the Z51 package, HUD, and Navigation system.
Thank you again for your replies. It helps a great deal to be able to reach a decision, and be willing to pay more for items that the first owner may already have added to the car.
Glen

 

What I remember about headers (late 60,s - 70,s) you would lose ground clearance, nothing like crawling over speed bumps and hearing your headers scraping.

 

This is really sorta funny, Glen. You're going to go from 240/250 HP to 400. You'll have all the increase in "bang for the buck" you can imagine.

I've got more than 350,000 miles in Corvettes and the C6 almost got away from me this past Friday. After the "fun" was over I thought: glad I was sort of expecting that, had I not been it would have been a whole different result.

After you've had your C6 for a while think about modding it.

JMO...

 

Changing mufflers pretty much just changes the sound levels. Power increase is negligible, regardless of what the muffler maker's advertising says. The stock system flows very well, it is just quieter than some show offs like.

Same thing for the air cleaner housing. It flows very well. As proof, the car dyno's the same with it on or off. If you want colder (and wetter) air intake, there are simple and cheap (read free) mods you can do to the radiator shroud and air cleaner housing to get more ambient air. This may help with heatsoak caused timing pull at the drag strip, but still won't show any gains on the dyno or while cruising down the road. Save your money for something that matters.

A tune will net you gains. GM tunes the car rich, and uses a more conservative spark advance than you can get away with if you always burn good 93 octane gas. Gains of 10 to 15 hp (depending on altitude) are possible by tuning alone. A tuner can also remove some or all of the abuse mode torque management, which will improve throttle response and the slight tendency of the car to bog at shifts.

If you opt for the A4 automatic in your 2005, a tuner can also raise shift points and firm up the shifts, gaining you quite a bit of practical performance. Higher stall torque converters are also readily available for this time tested transmission.

The LS2 does respond well to a better flowing intake manifold (note, not air cleaner housing). You can install a FAST or Wieand manifold and see another 10 ponies on the dyno. Or you can have your stock manifold ported and see slightly lower gains. The latter is much less expensive.

The LS2 also responds very well to head and cam swaps. Crane makes some good "quick lift" cams for this engine, and you can add 1.8:1 rockers too (the latter may require a slight modification of the valve covers as well as better springs). The usual suspects, AFR, Dart, etc offer ported heads that perform well. A well chosen head and cam combo can net you 20-30 hp without adversely impacting your ability to use the car as a daily driver (more if you're building a race car).

The biggest change you can make that you can feel, however, is rear gears. Going to a 3.90 or 4.10 rear gear (in a manual, autos need less gear) will really wake the car up in daily driving. It will adversely impact gas mileage, though. The rear in the C6 isn't the most durable unit, so a diff swap to gain strength alone can be something to consider.

The brakes that come with the Z51 option aren't really better, except in the bling department. The standard rotors are more durable, and stop just as well. Racers often turn to the standard rotors when it is time to replace them (they're lots cheaper). Standard pads also dust much less than the Z51 pads, but are for the street only, switch to race pads for the track.

The Z51 suspension components are also a hot topic here. The antisway bars are great, and very inexpensive to add to a car with the standard suspension. The spring rates and shock valving aren't so great. The lower rate springs of the standard suspension actually work better on a car of this weight on real world roads, and ride better too. None of the factory shock offerings are good. Plan on installing Bilstein or Koni shocks to gain control of the car over less than perfect real world roads. They'll help control wheel hop at the drag strip too.

The downsides to buying a 2005 are the delaminating roof issue with the painted tops (also a problem with 2006s, but there's a recall under way to fix this), and the tendency to mysteriously kill the battery in the manual transmission cars (there is a reflash that kinda sorta fixes this).

Another minor issue is the "Doughboy" steering wheel. It is bus sized, and GM changed it to a smaller wheel for 2006 due to owner complaints. Originally, the Nav radio in the 2005s didn't play MP3s. There's a software update (which you can do yourself if you like) which fixes that.

An issue with all LS2s (and LS1s) is the unkeyed harmonic dampener's tendency to back out and walk off the crank. Consider pinning this to the crank as a preventative measure. Pinning kits are widely available. GM has their own "fix" for this, but it isn't well engineered. Pinning works.

Another annoyance with the C6 is the push button start "feature". It isn't as reliable and intuitive as a key. But it does have positive anti-theft characteristics. No one is going to be able to hot wire your car successfully. OTOH, you may lock yourself out, or be unable to start the car in some cases due to the quirks of the system. You'll have to adapt to it since it won't adapt to you.

The C6 is a really nice car, a step above the C5, and a huge leap above the C4. It has minor issues, but all cars do. Don't let them dissuade you from buying one.

 

Oh, two other things about the C6. The headlights are wonderful. They're so far above the headlight performance of previous generations you'll actually enjoy driving at night. Second not so positive thing, the Bose "premium" stereo really sucks. Count on wanting a new amp and speakers (the HU is fine).

There are inexpensive alternatives that will give you decent sound, you don't need to spend thousands, or turn your car into a ghetto thumper. Eclipse, Boston Acoustics, JL, etc all make nice reasonably priced speakers that work well in this car. A good 4 channel amp is needed too (the Blose is a highly colored 3 channel amp which outputs mixed mono to the rear and center dash speakers, killing the stereo soundstage). The HUs output 4 channels, so the wiring changes are easy. You don't need a lot of power unless you're building a ghetto thumper. 65 watts is plenty.

 

Wow shopdog confirms what I said, I am not worthy

 

Wow, where to begin?

Thats "Z51". In the '05 automatics Z51 came with the performance suspension, Goodyear Eagle F1 Supercar EMT tires, performance upgraded suspension components, and the 3.15 performance differential. Larger brakes with crossdrilled rotors. The '05s had the 4 speed automatic transmission. Beyond 2005 the automatics were 6 speed automatics.

A few things can be done. The usual are cold air "intakes" such as those made by Callaway, Lingenfelter and Vararam. Cat back exhaust systems for these cars tend to be expensive and are said to provide little performance gain.

For what you are looking for, 10-20 RWHP/RWTQ, a cold air intake would be a good choice.

Cooler air into the intake manifold and "ram air" are believed to yield the most benefits in the C5 and C6. Results on the dragstrip tend to support this. Though the gains these systems provide are typically not demonstrable on the dyno as part of why they work is believed to be due to the car moving. The previously mentioned cold air intakes are said to provide a measure of both with the Vararam marketed as a ram air system. A search of the aforementioned systems will give some idea as to the performance gain to be expected.

Fuel pressure is not managed with a fuel pressure regulator in the C5 and C6 as it was in some of the C4s. It is all managed by the PCM (Powertrain control module) in the C5 and the ECM (Engine Control Module) in the C6, as are a variety of other parameters.

There are a few here who have done the Flowmaster mufflers. But primarily for sound as opposed to any performance gain.

As mentioned before, there is no "chip" in a C5 or C6. The PCM or ECM has to be flashed with the alterations in tuning parameters which the tuner decides upon. There are a variety of options as to how this is done. 1. On the Dyno and using tuning software on a laptop computer. 2. On the street or track doing real time scanning and logging and subsequent tuning using computer software. 3. Combination of both. 3. Sending the entire PCM or ECM to a tuner to have it flashed using tuning software. 4. Handheld units used to alter the stock factory parameters. 5. Consumer software tuning programs for "Do it Yourselfers. 6. Transfer of files over the internet to be used to flash the PCM or ECM by the end user using the same software.

This is done through the car's OBD port or in the case of removing the ECM and sending it out for programming http://www.corvettec5.com/store/?page=shop/install (scroll down to the bottom of that page and it will show you where the ECM is located and how it is removed.)


Stick around this section, search it, and you can find anything you want to know about the C6

Good choice on the color and the brakes. Z51 is a can't miss option. My belief is that if you're going to go, go Z51. Its all that they say it is and more.

http://forums.corvetteforum.com/show...30&postcount=1

Rather than argue about drilled rotors and such, I'll let you read up on your own. See what the SAE says about them

http://forums.corvetteforum.com/show...ghlight=rotors

Heres mine.

 

OK - I'm getting a picture here. Exhaust mods aren't worth the $ from a perfomance standpoint. Z51 package may be buying components that I won't particularly enjoy (harsher ride, more expensive rotors, etc.).
It sounds like a premium tune from a place like Doug Rippie Motorsports may offer me the most amount of performance for the money spent.
As one responder noted, I am going from a 250HP car to one with 400HP. This will certainly provide me with a performance "rush" that nothing I do afterward will equal. But as I orginally indicated, my goal was to maximize the performance of a stock engine. I equate maximum performance with maximum efficiency, mileage, responsiveness, etc.
Thank you to all who have so graciously taken the time to educate me.
Glen

 

Glen I wouldn't say exhaust mods are not worth the $. Typically with headers only and a dyno tune we get between 365 and 375 to the wheels with headers only flowing through the stock mufflers. A bone stock C6 will make about 340 plus or minus 5 to the wheels. So in saying that you can stand to gain upwards of 35 to the tires without any other mods. And if you ever were to step up to installing a head and cam package you will need the headers to get the most out of your investment. With a sleeper cam and cnc ported heads on a A6 C6 I netted 440 hp and 407 ft/lbs at the wheels, this is with a cam that sounds, drives, and idles like stock.

http://forums.corvetteforum.com/show....php?t=1629260

 

Definitely headers will increase performance, but he was asking about mufflers specifically, and they don't. There is a downside to headers too. Technically, long tube headers are illegal under federal law on any post-1996 car because they relocate the cats (swapping the cats to "high flows" is also illegal). There can be issues with codes being thrown too. Scofflaws routinely break this law, but it can be a problem in areas where emissions regulations are enforced (California being the most notorious).

 

Definitely a lot of trade offs if you are talking about doing long tube headers.

But the original poster mentioned that he was only looking for around 10-20 RWHP. That should not be hard to do at all.

 

Hey Glen....

For you....the best gains for the least amount of money would be our mail order tune.....

While we LOVE LG HEADERS and Vararams.....The best BANG for the BUCK is the tune.....

To the best of my knowledge there is no better way to improve the performance of your car for such a small amount of money...Also, for the guys who are on the fence about mods, thinking about trading the car in, or maybe driving a lease car, my mail order tune is PERFECT for you....nobody will ever know!

Stay Tuned!
Chuck CoW