Your post tune dyno numbers are the highest I've seen without a cam. Are those SAE corrected numbers?

 

The dyno sheet does not tell me if they are SAE corrected numbers. It is a WinPEP Dynojet Performance Evaluation program. I will check with the tuner next week. The tuner said car was very strong and he usually saw 380-385 HP when tuning C5Z's.
It was a perfect day for tuning,bay door open and nice cool air.

 

I agree with you about the ETs. I was not talking about dyno numbers. I was talking about actual trap speeds and I was not impressed, considering the expense. Since the quoted horsepower gains are usually peak number increases (5000-6500 rpm), I'm not surprised by the marginal real world performance gains. BTW - ECS did the header install and the tune on that Z. They certainly know something about careful part selection and tuning. I will look to them when I do my header/cam/tune.

 

The SAE correction factor will correct for the environmental conditions during tuning. Without correction, the numbers are not very helpful. Eg: My bonestock Z has trapped as high as 118 in 46 degree weather but typically traps in 115-116 in 70-75 degree weather and 113-114 in 85-90 degree weather. I once had my car dynoed and the first pull was SAE corrected 359.5/345.6, and the subsequent two pulls were 353.8/335.8 and 333.8/325.5 (no cooling fan was used). Temperature makes a big difference with the C5Z, about the same as headers and a tune.

IMO better indicators of improved performance are the average rwhp/rwtrq numbers. I had my C4 LT1 dynoed after LTs and a PCMFORELESS tune and the peak rwhp was 290.1 but the average rwhp was 239.4 (this produced 12.60s at 109 on DRs). After a cam install and another PCMFORLESS tune, I had the car dynoed again. The peak rwhp was up 32 rwhp at 322.29 but the average rwhp only went up 20 rwhp to 259. I'm not expecting a big improvement in performance at the track (should have picked a cam with less LSA - live and learn).

 

We appear to be in agreement. I was not criticizing any of your observations or tuner. I refered to the dyno as a tool rather than the end all be all definition of performance. Many people are proud of their dyno results and that's fine. For me, I only care about my performance. So far my gains have been 3 to 4 mph. This has translated into exceptional 1/4 mile performance. I feel that a Z06 with bolt-ons is capable of astounding times.

 

An engine is a combination. It is only as strong as it's weakest link. Improving a part that is already doing it's job well enough for the performance level you are looking for is pointless. Throttle bodies and MAF's are good examples of this, these are not restriction points on stock cars so making them bigger is going to get you a whole lot of nothing performance wise.

That being said if you start to modify your car you will run into the power wall where the stock exhaust manifolds start to hamper the car, at that point they are money well spent.

There is also the fact that they look nicer and do sound a lot nicer. Have to consider everything. Also they create more heat in the engine compartment, even coated headers don't retain heat like cast iron manifolds and heat sheilds, not even close. This reduces the life of every heat sensitive component in the engine compartment, which is damn near everything. It will also allow the extra heat to migrate up toward the air filter area at slower speeds. I know the radiator 'wall' is there but I don't doubt that hot air can still get up there at low speeds.

And last but not least, matter of fact last but probably most important is smog legality. Most of these cars are now transitioning out of their 6 year 'free pass' that a lot of states allowed on new cars and are going to need smogs to be re registered. To my knowledge there is not one aftermarket header that carries a CARB EO# yet. So if you live in a inspection/smog state that means no chance at passing and registering your car. I have been there, it sucks really bad.

Personally I have been torn over an centrifugal supercharger vs an STS TT system. Both make CARB legal systems but for a supercharger to really work you must have a free flowing exhaust. That means headers. Bam, back to not smoggable. Which sucks because I really like the look of the kits from A&A and ECS.

Oh, yeah, by the time you add up the total cost of a good system and it's installation you need to look at other areas that do yield more performance. The reduced weight from an aluminum hat BBK can be huge and unsprung weight is 1:8lbs ratio so losing 30lbs there is like losing 240lbs from your car, that is a noticeable seat of the pants difference and won't affect your smog or drivetrain. Plus it will stop better. Have to think outside the box on things that can give you equal performance without the downsides. Lot's of options for these cars, it's one of things that makes them one of the greatest cars ever made to modify. I would pick a C5Z over a C6Z to modify (and did!).

EDIT: oh yeah, my car had them on there when I bought it. I would not have spent $4k for 30hp. A few grand more and I get a supercharger kit that will be MUCH more noticeable power wise.

 

my 01" z best of 12.5@114,115 before kooks Lts, x-pipe, bullets, vararam, stat and fan control, 11.92@118 almost 119 on MT drags if thats not worth it punch me and not tune YET

 

This is why you dyno after each mod if you truly want to know what you're getting. 330RWHP with just a Blackwing and CF airbridge. 360 with LT headers and stock Ti exhaust. And the improvement in the sound was almost worth the spend even without the HP.

If you don't think headers are worth it, no one's holding a gun to your head but I'll put my headers up against someone with just a CAI any day.

Final point is that in order to maximize an increase on the intake side you also need to improve the exhaust side. They work better together. Performance 101.

 

I agree.

 

Cai and tune are the best bang for the buck....after that it starts getting expensive. Next logical steps are LT's and a cam. If you don't want to for it, don't do it

 

Been there, done that. What's up with the rolleyes? I know what the component gains are and aren't. This thread was intended to inject a dose of reality into the fourm, as the C5 crowd is getting younger on average, there is an increased hype/reality ratio. The number of people buying FAST intakes for stock cars is proof of that.

 

I agree with what you're saying to a point. If you believe what you read then a filter is worth 15hp, a CF bridge is worth 10hp, HP MAF sensor is worth anoter 10hp etc, and a hand-held tuner gets you 15 more. 50hp from bolt-ons right? Done right it might equal half of that.
In fact, a Blackwing and CF bridge netted me no more than just a K&N with the stock black box. It's also proven that most cat-back exhaust only adds noise and minimal HP. We do it all anyway cause it's fun.

Then someone has to go and rain on the parade!

 

coming from a svt lightning where you can add tons of hp/tq with a simple pulley, cai, and dyno tune it was hard for me to get past the cost of modding a c5 z06. But when i thought about it if the c5z had a factory roots/twin screw blower it would be very cheap to mod it. So the cost of dynatech long tubes/cat x-pipe/bassani catback for my lightning was almost the same price as the same mods for my z06. And the gains should be about the same if the lightning was keep in the 16psi range. The cost of modding any car is high. There is a huge demand for certain parts which adds to the cost and yes companies are going to charge alittle more for parts for a corvette. If you dont have plans of doing a cam, stroker, or FI i dont think Long tubes are worth it. But i do want a stroker so long tubes are good mod for me. It comes down to what money do you have to blow and what you want out of your car/

 

Here is another thread to read

http://forums.corvetteforum.com/c5-t...ifference.html

 

You can't just look at peak numbers when your talking about longtube headers. They typically show gains from 2,500-up. Look at the numbers under the curve and they were definitely a worthwhile mod.

 

The big mistake I see in this assumption is that CAI/LTs and tune are the only mods being done... ever. When is that the case?

I bet you'll see a huge difference in a car with stock manifolds and a big cam vs a LT header car with a big cam. I bet that gain increases on a car such as mine. If I had manifolds on and went to LTs at my power level it could be worth 150rwhp. How's that for a return on your investment.

The best part about LTs is they are a gift that keeps giving. The more you do to the car, the more the LTs give you.

 

Read the very first post when I opened the thread; I addressed that issue.

A lot of guys just jump in and buy headers on a street car thinking they're going to get amazing power without analyzing or researching what is actually going to happen. The truth is most people will not notice a difference in performance on a street car when adding and removing a 170lb passenger which will make more of a performance impact than a set of headers.

P.S. I love your flared rear wheel wells

 

With the x-pipe (no cats) it runs about $850. Not bad if stainless, but it's coated mild steel.

Also, because of the o2 sensor location you have to cut/trim a notch out of the heat shield in the transmission tunnel. Not many guys want to hack their car.... I bet the system would corner the market if they would angle the sensor location..... and ditch the mild steel in favor of stainless construction.

 

150 increase ?? not a chance.

To get a 150 HP Increase you need lots of displacement.

a 30 to 40 HP increase with bolt ons, CAI, LTs exhaust and tune is possible, with most of that coming from the Tune

any more a cam and better flowing heads, plus all the others to get the increase.

Getting 550 rwhp out of an LS6 is not impossible but it would not be too street friendly and need periodic rebuilds

Even getting 500 rwhp takes quite a bit of work on pump gas out of an LS6.

 

I think he is referring to the 402 he has + SC and pushing 750 RWHP. I think 150hp is a little much, but I bet if you threw on a set of stock manifold his power rating would drop off about 70hp. Just a guess though, unless he really wants to try it out and see what the result is Would be VERY interesting.