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Discussion Starter #1
has anyone come across tentative specs for how much boost the S/C will be putting out? i am wondering because the S/C version is supposed to have beefier internals, correct? if so my plan is to buy the S/C version sell the S/C and throw together a turbo setup with roughly the same boost levels, in turn not having to replace internals (hopefully), therefore saving me money. from there the tuning shall ensue!!!!!

my longterm goal with this car, since it is impractical from the get go, is to produce around 350hp yet still be a daily driver.

can anyone provide me with details, or point me in the right direction to start planning what i may need. please no "read corky bell's maximum boost", or am i better off finding a reputable shop to install a custom turbo setup?
 

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Discussion Starter #3 (Edited)
no crap, i was just wondering if anyone knew off hand what the actual PSI will be. ill stop being lazy and look.

pointless reply by the way;

anyway, ive looked all over and cant find any numbers for the PSI of boost the cobalt is putting out, anyone?
 

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Discussion Starter #5
sounds good to me, thanks for the USEFULL post.

now it seems to me that that much boost was developed to keep it reliable to their warranty standards. i wonder how much more could be handled with the appropriate upgrades (not including internals)

i dont know much about that though. im thinking it would be smart to get the base model and go the whole 9 yards with a custom turbo setup. does anyone know of some reputable companies known for doing breakthough work on new cars like this? preferably in the midwest?
 

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As I understand it, peak boost depends on alot of factors. The 12 psi figure quoted in that article is suspect to me. Here's my train of thought based on experience. My '99 GTP made 7 psi peak boost as it came from the factory. I know this because I installed my aftermarket gauges, to include a boost/vacuum gauge before I started modding the car (the factory gauge in those cars is just a segmented bar graph with no numbers). The stock pulley on that s/c (roots type Eaton s/c, by the way) was 3.8" in diameter. When I swapped to a 3.4" pulley, the boost peaked at 10.5 psi.

Here's where it gets interesting. When I installed a 3" cat-back exhaust, with the same 3.4" pulley, my max boost dropped to 9 psi. At first I was puzzled, and thought something was wrong. However, dyno tests and 1/4 mile runs proved that I was making MORE power with less boost. The reasoning behind this is that the exhaust was more efficiently getting the spent gases out of the combustion chambers. So the cylinders were more devoid of air at the beginning of the intake stroke, and they could thus suck more air in from the manifold on each stroke. The supercharger was pumping the same volume of air into the manifold, but the heads were able to swallow more of that air than they had before the exhaust modificatoin. This is what lowered the overall manifold air pressure (boost). So, overall, my engine was moving more air/fuel even though my max boost was lower.

Now, when I swapped in my 3.25" or 3.0" pullies for track use, my max boost would shoot up to the 13.5 psi range. Up there, I absolutely had to run race gas and bump up my fuel pressure in order to avoid spark knock and the dreaded knock retard. I could have controlled it with a modified PCM, which contained more performance-oriented fuel maps, but that's another topic.

Anyhow, that is my train of thought. A higher max boost doesn't necessarily equate to better performance. Sometimes, it can mean quite the opposite.

As for the 12 psi figure, my best guess is that maybe that supercharger, installed on that motor, but with a pulley sized to spin the s/c at the max RPM recommended by Eaton may yield 12 psi of boost. But unless the compression ratio on that motor is really low, there is an intercooler in there, or GM programs the ECM to just dump loads of gas into the mix to lower combustion chamber temps, you would have heaping loads of knock retard.

As for the differences in engine internals, I would expect dished hyperutectic-coated pistons just as in the L67 (GTP motor). The dished pistons lower the compression ratio, and the coating makes a good compromise between cheap cast pistons and far more expensive (and in some ways problematic) forged pistons. Ironically enough, it's the hyperutectic coating that makes the pistons in L67 engines so brittle, and thus shatter-prone under severe spark knock conditions! I'd be surprised if much else changes besides the pistons. Ecotec motors are built to take a beating as-is.

Now, the turbo vs. roots type blower vs. CSC argument is a whole other issue. Personally, I'm in the [unpopular] roots camp, but that can be argued another time.
 

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Vita said:
sounds good to me, thanks for the USEFULL post.

now it seems to me that that much boost was developed to keep it reliable to their warranty standards. i wonder how much more could be handled with the appropriate upgrades (not including internals)

i dont know much about that though. im thinking it would be smart to get the base model and go the whole 9 yards with a custom turbo setup. does anyone know of some reputable companies known for doing breakthough work on new cars like this? preferably in the midwest?
i will be working ( i hope, at least) with one company to bring either a CSC, turbo, or both to market for the kappa platform. i would expect a kit could be engineered and tested and released within 1yr. preliminary work could begin before the car is even out, which might lessen that timeframe. bad news for me is that im sure other entities, with their massive financial resouces are already developing similiar kits.

if you wanted to make your own, i would give great consideration to the two intake manifold types likely to appear on the solstice before you decide which version to buy. the NA version will likely have a polymer ("plastic") manifold and the SC version will likely have the cast aluminium intake/SC housing like the SC kits already out for the ecotec. personally, i would be wary of applying a lot of boost to the polymer intake. it is structurally weaker than the cast aluminium (tubes and flange) and may be prone to cracking or leaking at the head due to it being used for something it was never designed to do. the problem with the SC intake could be that the Sc outlet is cast as part of it. it may be possible to cut away the SC portion and machine a mounting surface for the throttle body allowing you to use this manifold for a turbo setup. maybe not! with out one of them in my hands, i can only venture a guess. all that said, it would probably be best to fab your own intake with equal-length tubes ala headers. this will give you the freedon to mount the turbo where you want, route the pipes the way you want, and design an intercooler for the car without being restricted by a stock intake manifolds orientation.

ive just forgotten half of what i wanted to say...dont post and watch TV at the same time! :nonod

i'd also take compression ratio differences between the two versions (if any) before choosing.

why cant GM just put a whipple on the solstice and make all this moot? :jester
 

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Limiting function on boost for a specific engine is really three elements: octane (burn charactoristics) of the gasoline, temperature of the intake charge, and maximum cylinder pressure before ignition.

Amount of power you get from boost is a function of chamber volume. A common mythconception is that boosted engines lower the compression ratio to reduce detonation. The real reason is to increase the chamber volume so that boost can increase the charge *mass* while keeping the peak pressures within reason and not to just increase the charge pressure.

Realistically, 12 psi boost on a stock engine and with pump gas at sea level is Right Out. (IMNSHO supercharging has a place, it's just above 10,000 feet) You are talking chamber pressures in the compression ignition (diesel) range. 3-6 psi is much more realistic particularly if you expect the engine to last 50,000 miles. More is going to require a considerable infusion of cubic money everywhere from the crank up.

The problem is in control of the burn in the cylinder. Every engine is different but basically you want two things:
1) smooth increase in chamber pressure following ignition (no detonation or secondary flame fronts developing)
2) peak chamber pressure in the 8-15 degrees ATDC range (will vary with engine configuration, one of the factors that makes tuning an art form)

RPM doesn't matter, gear doesn't matter, just those end points. How much explosive mixture you can introduce into the chamber while maintaining those two elements determines the torque produced at any given instant which determines the accelleration rate.

Number 2 can be achieved with timing maps but number 1 is a complex function that depends on a lot of factors such as shape/size of the chamber (spherical with ignition point in the center is best but hard to achieve in practice and I have yet to see an intake valve shaped like a kidney bean), efficiency of intake and exhaust, size and temperature of the intake charge, and temperature of the chamber.

Bottom line: if you can't control the burn and pressure rise in the chamber, the engine will never be all that it can be. Further, errors come out as heat and broken pieces. Not a good.

The limiting factor of any fuel is intake charge temperature and pump gasolines are formulated for specific temperatures and pressures found in normally aspirated automobiles. Exceed their expected parameters and you lose control of number 1 and then number 2 does not matter.

Incidently another mythconception is that there is more power in premiun gas than regular. Not particularly so. The difference is that premium burns slower than regular and has a higher flash point, both desirable as you increase cyl pressure and temperature, but even 93 PON has limitations. This is why water/alcohol injection and intercoolers are popular with boosted engines: both cool the charge so you start out further down the P-V curve (more power) and further from the flash point.

Can do more with special fuels which is why T/F uses a nitromethane/alcohol mix and hypergolic propellants like Hydrazine are banned by most racing organizations but doubt that anyone here wants to go there.

Now the ecotec engine with a long stroke and narrow bore can tolerate more boost on pump gas than an oversquare engine could but the limiting factor is still available gasoline so without visiting the track or an airport, about 6 psi is as far as an amateur (kit) should go and maybe 9 with a considerable amount of cooling, instrumentation, and dyno time.

Yes. I know, the article says "The supercharger produces a maximum boost pressure of 12 pounds per square inch (psi)." as usual it does not say at what flow rate or whether it will be allowed to deliver that much to the engine which I strongly doubt, there is a little matter of choked (sonic) flow that would need to be designed around.

As for 12 psi with add-ons to a stock n/a engine, well I suspect it would be kind of like 8,000 rpm with a 1971 TransAm 455HO. Once.
 

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Just as was mentioned already, knowing the PSI without the CFM at that level doesn't really tell you anything. Remember a motor is an air pump. The greater the volume of air you move through it in a given time period the greater the HP.
Use the garden hose analogy. It would take lets say 30psi to move a gallon of water through a 1/2" hose in 1 second, but only 15psi or so to move the same gallon through a 1" hose in one second. In other words, more "flow" with less pressure.
 

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Since the article mentions an Eaton M62 compressor, a quick look turned up not only a data sheet but also a good basic decription of what is going on and why more boost demands an intercooler. In the case of the Eaton would expect it would have to be air-water or air-freon and mount like an a/c core under the supercharger. ("Oh that's just the compresor for my a/c." :smile )

From this you can get a good idea of why the factory boost is limited to about 7 psi with premium gas. Yes people "just change the pulley" and get 10 psi which the engine controls (with lots of knock retard) can probably handle. It may even be a little faster than with 7 but efficiency is going to be declining fast and are investing a few more HP at all times just to spin it.

Now the Ecotec 2.0 has a smaller combustion chamber than an L-67 3800 so may be able to handle a few more psi but are a LOT of variables involved and all must be addressed when you exceed a half-atmosphere of boost at sea level, not the least are your timing, airflow, and fuel management maps.

Oh well, too much for one morning.
 

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Discussion Starter #11
wow, thanks for all the info everyone, a little much for one morning as was said but all will be considered. i'll probobly have to re-read that all 2-3 times later.

rergardless, more will be revealed as GM puts the car into production and more can be discussed.

bizz, keep on it. im doing some research on some places near me and im hoping to get some good work done to reach my goal of 350whp for under 8,000.

with respect to one of the above posts, it sounds to me like it may be hard to keep an engine with this much power reliable, but i've been looking into 300zx's and they seem to be very high maintenane, yet as long as you keep up with it all they are very reliable, ok i guess thats off the point a bit. really, what is a semi-realistic number of years an engine will last considering all is kept well, and only quality investment goes into the project?

i apolagise if that doesnt make too much sense but im a noob to boost, honestly i've never had to deal with it. but i think turbo is the way to go for me because i take a lot of long road trips and at cruising speed there isnt really too much boost or fuel consumption is there? correct me if im wrong
 

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Hoo boy, turbos (turbosuperchargers) are a whole different ball game. First use I know of was on the P-38 and came into play to allow it to really reach way up there and touch someone.

Are two kinds: then that blow through the throttle plate and those that do something else (don't want to get the anti-vulgarity league bothered).

Personally have always considered blow-through the wrong answer because when you shut the throttle, the air charge moving through everything suddenly hits a barrier which does two things:
1) It creates a pressure wave reversing through the intake which has rather complicated math we won't bother with right now.
2) The backpressure the turbo is pushing against goes way up which both slows the turbo and the work the turbo is doing against the backpressure causes heat.

When you open the throttle again, you get one burp as the backpressure dissipates, followed by a sag (turbo lag) as the turbo tries to come up to speed again. Not good.

OTOH with the "alternative method" which puts the throttle plate in front of the turbo, when you close the throttle, tthe turbine speed *increases* since it is now operating in a near vaccuum (and may need some sort of overspeed device) and when you open the throttle plate again, the increase in flow is much more laminar. Also spinning free in a near vaccuum, there is very little drag to translate to heat of the intake charge and backpressure on the exhaust.

If you are using a MAF sensor, putting it and the MAT sensor infront of the turbo also keeps the values much closer to what the computer expects. Win-Win.

And on the gripping hand, a blow through is the simplest to install and cheapest to build a kit since you do not need to relocate the throttle plate or other intake components so if you go on price, the salescritters will point you to a blow through and claim it is the greatest thing since sliced bread. Isn't. As usual the result is proportional to the effort and cubic $$$ you put into it.

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Engine driven superchargers are generally via the alternative method since is usually bolted to the top of the manifold. Was not always so, in the '30s bolting a supercharger to the end of the crank was popular but drive belt technology has come a long way since then.

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Engine longetivity under boost depends a lot on how the engine was designed in the first place, a proper design will last as long as a n/a engine or about 200,000 miles these day with proper care.

Failure occurs when the entire package was not considered. For example using n/a injectors on a boosted engine or stock injectors with smaller pulleys can lead to reaching the injector limit before the top end. When this happens the cylinders lean out and combustion temperatures go through the roof (why professionals pay close attention to EGT). This is when you burn holes in things like pistons and valves.

The other factor is that a boosted engine has much higher loads on the rod and main bearing surfaces than a n/a engine. This is why you see different bearing materials used and often a higher pressure/volume oil pump.

Finally, everything on a boosted engine runs hotter because you are putting out more power and the waste energy has to go somewhere. Intercoolers, larger radiators, oil coolers, and lowered thermostats all can help.

Personally, I run my computer cars at 180 instead of 195 including reprogramming the fans to come on earlier. In my experience *everything* lasts longer - hoses, belts, batteries, everything. I would run a boosted engine even cooler: 160-170 F just to start out that much further down the PV (power) curve.

Keep in mind that while the general designs cars to a lot of factors, longetivity past the warrenty period is not one of them and I tend to keep cars far beyond their sell-by date (at the moment we only have one car with less than 100k on it and that is the '88).
 

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Bizz,
Dont waste your time or hard earned cash on a turbo kit yet
the Saab 93r has the same ecotec engine with a factory turbo.
of course this design will be lacking but many cues can be taken from it and improved upon.
I also come from the GTP crowd so I know a bit about boosting and such. It was also very nice of gm to pay for all that research on their drag car to let us know how much an ecotec can take and what to do to get it there :)

-K
 

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I'm in the "turbo is better than SC" group myself, having owned and modified a turbo, but I wouldn't bother changing a S/C to a turbo. Especially not on something like this. The difference in efficiency is going to be minimal, the custom piping to suport a turbo will be difficult if not near-impossible due to space, and the necessary additional equipment will be $$ and again, a big need for under hood space. You would be FAR better off spending the money upping the power from the existing setup. Dollar for dollar I see no way you can come out ahead with a turbo setup. Unless of course you know enough about turbos to get a good one from a junkyard and can do all your own custom piping.

I have no doubt that a factory supercharged 2.4L Ecotec can safely and reliably hit 350hp without swapping to a turbo. It WILL take some R&D by various performance shops, learning the weak or restrictive parts that need upgraded, ECU upgrades or piggy-back chips.....

Here are a couple key points to the 2.4 ecotec that will allow higher boosting:

# Piston-cooling oil jets spray the underside of each piston with a continuous bath of engine oil, increasing longevity by reducing engine operating temperatures.

# Redesigned cylinder head with structural improvements and new multi-layer steel gasket.

What I can't find is if this is an open or closed deck design.. I can't even find a pic of the engine without the heads. With all the apparent emphasis on strength it seems like it must be closed or at least semi-closed, but I would have thought that would be listed with the other ecotec good points.
 

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Kael said:
Bizz,
Dont waste your time or hard earned cash on a turbo kit yet
the Saab 93r has the same ecotec engine with a factory turbo.
of course this design will be lacking but many cues can be taken from it and improved upon.
I also come from the GTP crowd so I know a bit about boosting and such. It was also very nice of gm to pay for all that research on their drag car to let us know how much an ecotec can take and what to do to get it there :)

-K
is the 93r's engine transverse or longitudinally configured?

the custom piping to suport a turbo will be difficult if not near-impossible due to space
theres puhlenty of room. :jester but,THIS shows how easy a CSC would be.
 

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Reasonably certain, TOL Ecotecs are supercharged (2.0 uses an M62 & is claimed to be good for up to 3 l), Turbo from the swedish airplane company is a different base engine, and GM cars today rarely use turbos in this country, probably drivability issues.

Now where I would put innovation would be in the intercooler. We can figure that the Solstice will have A/C stock. And GM compressors since the '73 Vega have been capable of declutching during WOT. So what I would like to see is a R-134A intercooler...
 

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Isn't the Saab 9-3 a 2.0l ecotech-based turbo?

While there's not many Saab's, I wouldn't call them "rare". And Saab's a subsidiary of GM.

I just can't imagine where they'd put a supercharger in the Solstice, hood's pretty darn low.
 

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solsticeman said:
Isn't the Saab 9-3 a 2.0l ecotech-based turbo?

While there's not many Saab's, I wouldn't call them "rare". And Saab's a subsidiary of GM.

I just can't imagine where they'd put a supercharger in the Solstice, hood's pretty darn low.
Who says it has to sit on top of the engine? There's plenty of room for it to sit side-saddle where the intake plumbing is. The throttle body is alredy there. Check out this pic of a s/c'd 2.0L ecotec, and you'll see how it's likely to be configured.



It looks like there could even be room to sandwich an intercooler between the s/c outlet and the intake manifold without making the assembly taller than the top of the valve cover!
 
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