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  Topic Review (Newest First)
05-16-2019 05:40 PM
wspohn
Quote:
Originally Posted by [email protected] View Post
My NA Sky sounds a lot better than the twikkey sound of of the turbocharged Sky. Mike Marten put the RL ex. On his and sounds fantastic in his video. As for speed, just went over 3000 dollars in speeding tickets over 10 years, dam cameras. These cars are fast., believe it.
A turbocharger does act as a muffler, so unless the exhaust system is set to produce a louder note, the turbo car may seem restrained. But - spend $1,000 on both the NA and the Red Line and the latter will be getting through the 1/4 mile about 2.5 seconds faster - and that is a huge difference in performance.

If the lower performance version is adequate for you, go for it, but not everyone is willing to take that big a hit.
04-22-2019 12:55 PM
[email protected] My NA Sky sounds a lot better than the twikkey sound of of the turbocharged Sky. Mike Marten put the RL ex. On his and sounds fantastic in his video. As for speed, just went over 3000 dollars in speeding tickets over 10 years, dam cameras. These cars are fast., believe it.
04-06-2019 09:58 AM
tporter I have a spare factory exhaust i could chop up to put a new muffler on. Just hard to find the "note" i really like.
04-01-2019 02:28 PM
Robotech
Quote:
Originally Posted by wspohn View Post
Robo - couple of things.

Is there any dyno evidence that a muffler swap shows any increase on a dyno?

Kinda. Our stock exhaust on the 2.4 is 2.5". The exhaust on the MagnaFlow 2.5" is well, 2.5". The routing of the stock exhaust and the MagnaFlow exhaust is identical until you get towards the muffler because of where the muffler inputs are on each. When I talked to MagnaFlow when they were designing the exhaust on my first Sky, they told me directly there is NO performance improvement from the exhaust piping itself because the stock exhaust is really well designed to begin with. It's relatively straight and the shallow bends it does have are not crush bends. Thus the 7-8 WHP my car picked up on their Dyno (with no other mods) was all from their muffler.


So while my exhaust was a complete exhaust, I'll take MagnaFlows word for it that changing the muffler is where the gains were picked up.

Quote:
Is there any evidence that the size of the stock injectors limits output - in other words are they maxxed out and starving the engine at full throttle at any point? If not, you can triple the size of the injectors and all it will do is ruin you idle when they can't shut down enough at idle.
I do not have any but this is something that has been around the Ecotec world for sometime. You don't hear it much in the Kappa platform, but the Cobalt guys swear by it and my understanding is that those who race Ecotecs in other platforms (they're hugely popular in the off road world) have dyno'd and seen a power increase with the larger injectors. Huge? No, but nothing short of NOS, a turbo or a supercharger is going to be huge.

With the factory tune the injectors are, for all intents and purposes, maxed out. The engine isn't starving for fuel, but it's not running ideal mixtures at WOT either. If you do things to increase the engine's efficiency...exhaust and down pipe will do that...then you make the problem worse. By increasing the injectors and retuning the engine to optimize fueling (and now richen up fueling on WOT so its running a mixture it should be running) you can get more power. Is it worth the cost? That's up to the individual. I decided to turbo the car and run appropriate injectors for that rather than tweaking the NA variant.


36lb injectors won't cause idle issues. I've been told even going up as high as 60lb you can still tune idle (42s are usually used for turbo builds with low boost levels...60 lbs for higher boost levels) on the OEM fuel system. The issue with idle is why I went with a return style boost referenced fuel system instead. At idle, when the engine is under vacuum, fuel pressure is lowered so that the injectors can run low enough at idle without issue. When I run my 80lb injectors in my new setup, this will be a requirement (and is why I did it). Also, when I'm on boost, the fuel pressure will increase at a direct proportion to boost so that relative fuel pressure between the rail and intake will remain the same and I don't have to run larger injectors to make up for a loss of fuel pressure.
04-01-2019 12:59 PM
wspohn Robo - couple of things.

Is there any dyno evidence that a muffler swap shows any increase on a dyno?

Is there any evidence that the size of the stock injectors limits output - in other words are they maxxed out and starving the engine at full throttle at any point? If not, you can triple the size of the injectors and all it will do is ruin you idle when they can't shut down enough at idle.
04-01-2019 12:44 PM
Robotech
Quote:
Originally Posted by tporter View Post
Looking for a little more HP on a budget.
I'm not disagreeing with anyone here. Depending on what you paid for your NA and what Redlines are going for in your area, you may or may not find it cheaper to sell your car and go get a Redline. Nothing I talk about below will give you any more power than a stock Redline. As a matter of fact, none of it will even get you close.

That said, there are some things you can do to eek out a little more power.

First is a muffler swap. You can go with the Magnaflow muffler designed for the 2002 Camaros and put it in keeping your stock piping. Our stock exhaust piping is actually pretty good. You will need a exhaust shop to weld it up and you can, if you want, add a second outlet to it. For inexpensive though, just keep your single outlet and have the muffler shop weld up that tip to the new muffler. You may get about 5-10 whp out of this.

Cold Air Intakes. You will actually lose a little whp with this one...with the GMPP intake I saw a 1 whp drop for peak wheel horsepower. HOWEVER, you will pick up power in the low to mid ranges and this really is worth the 1whp drop at peak. You'll never miss that but you'll like the pickup you get when you get on the throttle to pass someone or accelerate out of a corner.

High Flow Cat or Catless downpipe. IF you're in CA and don't want check engine lights, ignore this one. You may pick up 5-10 whp here too if you go this route.


Tune. This is going to pick you up the most power but it probably will cost the most as a single item. Figure about 10-15 whp increase with a tune.


Tune and injectors. I list this separately just because you can't do injectors without a tune but you can do a tune with injectors. The stock 2.4 injectors are very small. They are the same sized used on the 2.2 liter. They are 24lb injectors. You can upgrade these injectors to 36lb units and then a tune. RPM (who sells the kit for this) has seen as high as a 26 whp increase doing this, a catless downpipe and intake.


All that combined will cost you at close to half way to a turbo kit yet you're going to only improve 30-35 whp. (Injectors and tune with downpipe and CAI is almost $1,000. Figure another $400 for a muffler installed by a shop) That will take you from about 135 whp stock (the 2.4 is rated at 177 at the crank but dynos about 135 at the wheels) to about 165-170 at the wheels. A stock Redline dynos around 225-235 at the wheels. The RPM K04 turbo kit ($3100) will take you to 225-235. The Stage II kit with the upgraded K04 ($3700) will take you to where tuned Redlines usually sit at (270-280 whp).

So the question is what do you consider cheap and what are your expectations? If you got your 2.4 for under $3-5k, then putting a turbo on it may be cheaper than going out and buying a stock Redline. If you're not wanting Redline power, then a muffler and intake may wake up the mid range enough for you. You may not want the hassle of upgrading things and going with a Redline might suit you more.
04-01-2019 10:01 AM
wspohn Oh yes, they recognized the weakness in the design and rectified it for competition cars with a rather expensive kit that does what the DDM Probeam does but for significantly less money.

See https://www.solsticeforum.com/forum/...ro-beam-65529/
04-01-2019 12:06 AM
mstrjon32
Quote:
Originally Posted by wspohn View Post
Maybe I am over rating the flaws, but it was so obvious to me the first time I drove the car hard it seems hard to believe that someone at GM didn't twig to it. Maybe they did, suggested a change and were nixed by the bean-counters - who knows?
It's been a while since I've thought about this, but wasn't there a replacement rear suspension member that was part of the full Z0K setup that effectively does the same job as the ProBeam? My point being that someone at GM likely thought of it and somewhere along the line, it was removed from the stock production car.

In the past I've been really impressed by GM's engineering compared to other automakers, but they are often let down by a bunch of clowns in both their marketing and accounting departments.
03-31-2019 02:57 PM
tporter Thanks for all the input, car was free so there wasn't a chance of driving an RL to see the difference, inside the backbone and loved the difference, guess ill put an exhaust in it and enjoy it for a while.
03-31-2019 01:22 PM
wspohn
Quote:
Originally Posted by JohnWR View Post
I have the DDM ProBeam on the NA, and will put one on the RL this spring, before I take it to New York. At $185 it is the single best upgrade I think anyone can make to either car.
Yes, the difference isn't subtle! But what do you think of a company that does a half job on suspension development and then figures that no one will notice the shortcomings and it would cost them money to improve it, so they just ignore it. But then it was the same company that foisted the first generation Corvair on the public (and it wasn't anywhere near as bad as that twit Nader made it out to be).

Maybe I am over rating the flaws, but it was so obvious to me the first time I drove the car hard it seems hard to believe that someone at GM didn't twig to it. Maybe they did, suggested a change and were nixed by the bean-counters - who knows?
03-31-2019 01:12 PM
JohnWR I have the DDM ProBeam on the NA, and will put one on the RL this spring, before I take it to New York. At $185 it is the single best upgrade I think anyone can make to either car.
I tried a BackBone on the NA and thought it reduced my control on broken pavement more than it enhanced it on smooth pavement, so I took it back off.
03-31-2019 12:01 PM
wspohn I tried both versions. The handling on the NA struck me as too soft (the turbo version has stiffer settings but it also had a flaw - a mid-corner spot where it seemed to grasp for adhesion). Doing the suspension stiffeners on the turbo car I bought made a huge improvement. I can forgive GM for going with softer settings as that is what the majority of drivers will want. I don't forgive them for building an inherently weak rear suspension that requires an expensive (for the GM ite at least) package to put right so that the frame is strong enough to take hard driving.

My advice to potential buyers is always to drive both versions before buying a car to find out if the power is a make or break decision making factor for you. I agree that if you want more power out of an NA you should just sell it and buy the turbo car.

I usually would go for power, but not always. I have a couple of old British cars, one a street version and the other a race car with double the power. I am quite happy puttering around in the lower powered car on the street, and I can understand John, apart from any emotional attachment, being happy with the lower powered car as a fun runabout.
03-31-2019 11:57 AM
44thSKY Our two Kappas are a NA SKY with Redline exhaust as the only change from stock. My GXP is an all stock Coupe, thus with a pretty substantial hearing loss I probably don't hear what others hear.

I like my NA a lot and it is original except the exhaust. On the freeway, at traffic speeds of 75mph, I'd like it to move a bit faster when changing lanes and getting away from a cluster of traffic. I don't have the bracing, but really don't know that I can justify the effort and expense with the type of use we put the car through. (not thirsty for twisty's runs, and the other half objects to them)

Our GXP exhaust isn't heard too much in the coupe with the Targa top on most of the time. The GXP meets my expectations on the freeway where the NA is a little deficient. The long range plan for both cars are two of the oldest children are inline for them.
03-31-2019 11:25 AM
Emmett
Quote:
Originally Posted by mstrjon32 View Post
Does it? I have a RL and have always thought that this car didn't really sound all that great. The only redeeming factor is the sound of the turbo--but every other sound from under the hood just makes it sound broken, and the exhaust, eh. Thankfully the nice handling and the performance more than make up for the sound.

The dual exhaust does look better, though.
I agree with JohnWR when he writes:

> Because of that, the RL exhaust on an NA gives it just enough "throat" to be interesting without being obnoxious. <

I have an an automatic - so I haven't experienced the back-talk crackle he refers to though.

What I like most about the RL exhaust is how the car sounds when I turn on the key. It says performance.

For me - I wasn't happy with the handling of my NA until after I installed the DDMWorks backbone, probeam and swaybars.

Now the car handles pot holes much better, feels more solid. Especially at 90MPG.

Best of all, I like the 'no-boat' 'no-lag' feel changing lanes on the freeway. It feels responsive like an expensive sports car.

Eh. The RL guys have have the enhanced factory suspension package - and get better handling already from GM.
03-31-2019 09:04 AM
JohnWR
Quote:
Originally Posted by mstrjon32 View Post
Does it? I have a RL and have always thought that this car didn't really sound all that great. The only redeeming factor is the sound of the turbo--but every other sound from under the hood just makes it sound broken, and the exhaust, eh. Thankfully the nice handling and the performance more than make up for the sound.

The dual exhaust does look better, though.
I have a RL exhaust on my NA and really like it.

The RL with the RL exhaust sounds (exhaust-wise) about the same as an NA with an NA exhaust, but the RL exhaust is quite a bit more open, due to the muffling effect of the turbo. Because of that, the RL exhaust on an NA gives it just enough "throat" to be interesting without being obnoxious. You also get a very cool crackling "back-talk" when decelerating under certain conditions.
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