I was going to reply to some questions in the transaxle thread but thought it would be best not to go too far off topic and clutter that thread up. Continued from that thread:

Those are some good questions and commonly come up when talking about "upgrades" on different turbocharged cars. We'll start with intake and the inlet tubing. The act of compressing air is what causes it to dramatically heat up coming off the turbo's compressor side, but colder and therefore denser air going into the turbo's inlet equals slightly cooler and denser compressed air going out. With that said the SS Turbo already has a cold air intake stock so that isn't a good selling point of an aftermarket intake. What does look like an area for improvement is the stock filter size. I haven't measured the surface area of the stock filter yet but after looking at it I was surprised how small the filter element is. This was probably done for packaging reasons so there may be a small gain in upgrading the intake when pushing the car past stock power levels.

A lot air boxes on modern, forced induction engines are sized pretty well. For example on my Neon a good drop-in filter can flow more than enough air than the stock turbo is capable of flowing and even enough air for the larger Mopar Stage 3 turbo upgrade (which stock can support over 350 hp on race gas). On cars like those you buy an intake for the reduced baffling and increased inlet tract noise (i.e. you like to hear a louder turbo whine and the stock diverter/surge valve) or because you want to open up some room in the engine bay or just for the aesthetics of it. All those reasons should apply to the Cobalt but because of the small stock filter size you might also see some gains when trying to max out the stock K04. It's something that some dyno and track testing by independent, un-biased owners should tell us where the limit is.


As to "upgraded" intercooler piping there should be absolutely no performance gains to be had on the stock turbo from moving up to a 3" tubing vice 2.5" aftermarket tubing. The stock plastic pieces do neck down a little in a couple places but I bet it's still overkill for the stock turbo. Go too big and don't have a turbo that can flow enough air mass and you might get slightly more lag, but that shouldn't be very noticeable on the Cobalt's K04 turbo. Then again like mentioned the bigger piping should provide no performance gains either unless there is significantly better flow due to less restriction due to design of the stock pieces, although I don't think stock is as bad as some people think. The area where aftermarket tubing could be beneficial is if you have issues with the support bracket on the stock plastic upper piece breaking off. So far this appears to have taken out more than a few electrical connectors for the high-pressure direct injection fuel pump. The other reason to buy upgraded plumbing/tubes would be to buy for appearance reasons but to me that alone wouldn't be worth the cost. For others it might.

With regards to the cooling question, like mentioned we already have a cold air intake due to the sealed air box and where it draws it's air from. A different or thermally wrapped intake or intake plumbing will make essentially zero difference in performance. When the engine is running and under boost you're moving a large volume of air mass and it doesn't have time to sit in the intake tract and absorb heat developed from the underhood temps. You're moving a lot of air when under boost and it can't effectively transfer heat to/from the tubing. If you've never looked inside of an intercooler they're not just hollow metal tubes with external fins around them. The intercooler actually has fins inside the tubes as well as outside. This creates turbulence and gives the much greater surface area required to scrub heat out of the intake charge. The intake plumbing does not have this and therefore can't transfer heat from or to the intake charge effectively. That's not to say the intake pieces won't get physically hot to the touch but the amount of heat that gets transfered is minimal.


Another popular "upgrade" lately that goes along with intake upgrades is the the thicker intake manifold spacer gaskets that are supposed to isolate and prevent heat from transferring from the head to the intake manifold. The gasket material is normally a thick phenolic resin material but I've also seen Teflon and other plastic material used. It sounds nice in theory but a few things conspire against it. If you're driving around with the hood closed and come to a stop the underhood temps are going to skyrocket (they're usually not too bad while the vehicle is moving). The intake manifold is then going to absorb this and other radiant heat (but even if it does get a little hotter it's not going to have a giant impact on performance). If you had a supercharged car with extreme temps in the manifold and were running a strictly race-only type car where you have the hood open in the staging lanes at the drag strip and ice down the intake, these gaskets may help keep a little bit of heat from transferring as fast. But on a normal car the gains won't be there.

Speaking a moment ago about internal fins in the intercooler it brings up another common area people try to upgrade. There seems to be a rush from the aftermarket companies to bring a larger, upgraded front mount intercooler to market. The problem with this is I haven't seen any testing to show the stock unit is limiting performance and an upgraded intercooler is needed. The stock unit looks decently sized for the flow and power levels of the stock turbo. In general you can never have too big of an intercooler (unless you're talking a super tiny turbo with very minimal air mass flow which isn't the case with our car). But just because you upgrade doesn't mean there will be performance improvements.

The stock intercooler uses a tube-and-fin design but we'll probably see some places advertising bar-and-plate "upgraded" cores and larger sized intercoolers. As a generality, the bar-and-plate style cores tend to cool better than a comparable sized tube-and-fin core but they also generally have reduced flow capacity and higher back-pressure. This can all vary significantly due to differences in things like internal fin per inch count and fin desing. Cores can vary greatly and most of the inexpensive intercooler cores that intercooler manufacturer/builders use that come from places like China and Taiwan aren't provided with accurate core specifications so it's hard to tell what you're getting. Even when the intercooler makers uses more expensive Spearco and Garrett cores there can be wide variances on the finished product depending on not just core differences but things like the end tank design.

There are two main factors to look at when evaluating installed, in-car performance of an intercooler: cooling ability and pressure drop across the core from inlet side to outlet. You could just go out and buy an aftermarket unit and hope it works better but the best way to test if it's needed is to measure and find out how well the stock unit is working and then compare it to different aftermarket intercoolers. To do this you'd want to install some measurement equipment, namely pressure sensors or gauges at the intel and outlet of the intercooler as well as temperature probes. From this you'd be able to data log cooling efficiency as well as see how much boost pressure the intercooler is dropping (higher internal fin count cores can scrub off more heat but also create increased friction and restriction in the air that causes the pressure drop). You can kind-of use intake charge temp sensor readings using an OBD-II scan tool or scan gauge but that won't give you the precise inlet-to-outlet comparison.

It's possible there are some small gains to be had upgrading intercoolers on the stock turbo but I'd bet you'll just see a little better consistency if you drag race a lot and not a significant increase in power unless you're overspinning the turbo well past it's efficiency range (when it would start moving less and less extra air mass but put out more and more heat which lowers air density and gives less oxygen to burn). The stock intercooler looks very nice for overall design/size although I'm not a big fan of crimped-on plastic end tanks. This may turn out to be a limitation for those swapping over to larger aftermarket turbochargers.

On to the exhaust side, hotter gas generally has a higher velocity. As the exhaust gasses pass through the exhaust system towards the tail pipe it tends to cool down and lose velocity. That might sound like a bad thing but wrapping or insulating the exhaust post-catalytic converter will not make any difference. And from experience there usually isn't much to be had from insulating the exhaust manifold or manifold runners (depending on design) as well as the turbine housing in the front half of the exhaust system. The main reason to wrap exhaust components is lower underhood temps and this shouldn't be needed on a street driven Cobalt.

It's not going to hurt performance but the wrap does have some nasty side-affects which should be given a lot of considering before you go wild wrapping stuff. The material doesn't breathe well and tends to trap moisture under the wrap when the engine is shut off and cools down. Then when the car is started again and heats back up this moisture can become very corrosive and greatly reduce service life by increasing the chance of cracking, warping, etc. Another popular trend has been to ceramic coat manifolds and other pieces. This can slightly help lower underhood temps (but not as well as a good wrap and/or the stock heat shields) but the cost-benefit ratio just isn't there. I've seen way too many companies in other markets using cheap spray or brush-on "coatings" that they bake in their home ovens or let dry and hope will cure when installed on the car and started the first time. I also don't like what some places are doing when coating the inside of the manifolds and exhaust housing as I've seen very few coating exposed to the extreme heat and the corrosive nature of the exhaust gas hold up when used inside an engine.

With either of these methods lets say the could significantly increase the the exhaust gas temps held in the manifold pre-turbo. The turbine wheel and the design of the exhaust/turbine housing concentrates the exhaust gas on the inducer (the side, inlet edges of the finned wheel) and as the exhaust expands across the wheel and exits via the exducer part of the wheel (the top of the fins that face into the exhaust housing and go out to the downpipe) it transfers energy into rotational energy. A higher inlet temp of the exhaust gas may yield slightly more energy that can transfer to the turbine wheel but you normally don't see much if any gains with wrapping a turbo design like ours that is coupled fairly close to the cylinder head. If you had a remote or side mount turbo on the side of the engine bay with a couple feet long exhaust runners it might be beneficial (in addition to helping keep underhood temps down) but isn't worth it on our stock setup.

Again these wraps or coating are something you could test the effectiveness of fairly easy by mounting a fast acting EGT (exhaust gas temperature) probe right at the manifold collector area where the turbo bolts on or placing the probe in the inlet of the exhaust housing scroll area. Then monitor the temps before wrapping or coating the manifold and then log what temps do afterwards. My bet is you won't see more than 50-100°F change, if even that much. You could also remove the EGT thermocouple probe and install a pressure gauge to measure exhaust back-pressure pre-turbo to see if the wrap/coat makes any changes to that (not likely).



Now all of this is just a summary of my experience and what I've seen and tested over the years on a range of different cars. If you have a street driven car, even one that's heavily modified, you'll probably find most it will apply to the new SS Turbo and it's stock LNF engine. Now for someone doing a 1000 hp build and going for every tiny gain no matter the cost or durability impact some things like the exhaust wrap might be worthwhile. For a large percentage of the people on here many of these "upgrades" won't give a significant benefit on their car. There's a lot of aftermarket companies and tuner shops I like and trust but we'll also see a lot of places marketing parts just to sell them and make a profit. It's a sad fact about the automotive aftermarket. As a consumer and group of auto enthusiasts it's our collective responsibility to test and measure upgrades to independently verify gains or losses and not just guess or reiterate opinions of others. If you don't do that the only thing you can be guaranteed is that your wallet will be lighter.

Test, test, test. Data log, data log, data log...

 

WOW! Nice write up!

 

Oh god, my eyes hurt

 

my gawd, that's so much more depth than i can read right now

 

Cliff notes? lol

Read it all and its pretty good. My car is staying stock!

Read it all and its pretty good. My car is staying stock!

 

To summarize I'd say there's some stuff that I wouldn't do to my car, then there are other upgrades that may or may not prove to be beneficial for some people (depending on what they've done or plan to do to their car), but without some strict testing using a scientific method we won't know for sure. You already see a large amount of people here on the forums talking about buying these types of "upgrades" but just because something is on the market doesn't guarantee it's good or beneficial for your car.

Upgrades can be a good thing if a stock piece has a known deficiency or if you've made other changes from stock and need other new parts to make everything work together as a system. Upgrades can also end up being made for appearance type reasons as well (there isn't anything wrong with that since you bought the car, you do what you want with it). Then there are upgrades that can have a negative impact on your car or do nothing for you. Just make sure before buying anything to do your research or you may end up trying to buy a part for performance reasons and never see those gains materialize.

 

Holy crap... so much reading...

Good job though!!

I learned something new today.

 

 

subscribed to read later

 

nice write up

 

Thanks for the great info. I was already under the impression that most people are doing upgrades that are unnecessary...but had no clue that they were that insignificant and had not clue as to why they may not be helping.

One quick question for you...if I am just looking for a bit more performance and reliability in my parts, would I be best suited to get the GM performance kit (when it comes out) and then replace the charge piping with the Hahn piping?

Again, I know that the GM kit will give me some noticeable gains due to the reflash and that the piping will not give me any gains. I'm thinking of upgrading the piping just to get something that is a bit more reliable than the plastic piping the car comes with. Based on your assessment, the only part that you see as slightly deficient is the charge piping (just because it is plastic...not because of size or shape).

Any advice on my plan or does it make sense for what I am looking for?

 

Beautiful write up. Your posts are always so informative and unbiased

 

damn i actually sat there and read

good write up

 

There are two big advantages I see about the GM performance upgrade kit compared to other tuning options. First is that because it comes from GM they've done extensive drivability, performance, and durability testing to ensure reliability along with the increased power. Second is the retained powertrain warranty. When comparing the GM kit to other tuning options it's somewhat dependent on your local dealer as to what they will or will not cover but you should have a much better chance of being taken care of with the GM upgrade (although like the kits for the old supercharged cars, some dealers had issues honoring the powertrain warranty with those kits so you may check with your local dealer before buying).

If all you care about is raw numbers you very well could make the same or maybe even more power using another aftermarket tune/recalibration. It sounds like the GM kit will be less expensive than the BSR PPC flash tool but an HP Tuners calibration could still undercut the GM kit. But it comes down to who exactly is doing the calibration/tune as HP Tuners is nothing more than the tool with results dependent on who is using it. You'd have to weigh the experience of your tuner of choice against GM's resources.

Your logic on the intercooler piper falls in line with mine. If you're on the stock turbo don't buy it for the performance aspect but instead for the increased reliability. Because the stock piping has shown issues with the support bracket problems on the upper tube it might be beneficial, but then again weigh the affect on your warranty. If the stock piece breaks and takes out the injector pump you might be inconvenienced but it should still be covered under the 5/100 powertrain. If you upgrade the piping it may raise a flag at some dealers and prevent you from getting covered service for other future repairs. The only other thing I'd look at if you do go with the aftermarket tubing is that it's properly supported and doesn't place any increased stress on other parts (meaning what holds the piping up and in place whether that be support brackets or relying on the couplers and where it connects to for support of the pipe). That and making sure there aren't and clearance issues when the powertrain moves on its axis under acceleration.

From a simple bolt-on and go standpoint the GM kit should be great if you place a little more emphasis on factory parts, the warranty, and possibly better drivability and durability (i.e. not pushing components like the turbocharger outside of it's efficiency range, etc., like what could potentially occur with non-GM upgrades). If you want a little more power on top of what the GM kit brings to the table that's not to say there aren't going to be further gains that can be extracted with a reasonable safely margin, but you'll need to be very selective and careful about those upgrades.

For example we don't know for certain if the GM kit for the Cobalt will come with a different air box or intake like some have hinted, but if the stock filter element does proves to be a restriction there might be so benefits upgrading that. The stock cat/downpipe assembly appears to be somewhat restrictive and initial testing and results have shown some nice gains. And maybe for those in hotter climates a different intercooler might help control charge temps better which could influence intake charge temps and therefore knock resistance and ignition timing (which in turn affects power production).


There may be other areas where improvements could be seen as well, but some static testing (i.e. dyno) and backing those upgrades up with some data logging on the street and track testing should provide answers on the merits of those upgrades. You also have to be careful about the testing methods and who is doing them. For example, I have some strict testing procedures I like to go by when using a dyno to compare differences between bolt-on parts. Dyno numbers can be manipulated easily, sometimes intentionally and sometimes accidentally, but either case as a consumer you need to be aware that a dyno sheet may not tell the whole story.

Let's say a company introduces xyz part for the SS Turbo. They put the car on the dyno and do a bunch of baseline runs then install their upgrade. If they do this over the course of a few days you can get small differences in dyno readings just by atmospheric changes between days, how hot the car was running on a particular pull, maybe even a different batch of fuel was in the tank, or even from how tightly you strap the car down. In the past on other cars I've seen some wild claims made where the company was using two different dynos done months apart at different facilities. The company was advertising those gains on eBay and a couple auto forums but a close inspection of their dyno sheet showed there was also a barometric pressure reading used in the SAE correction factor that was wayout of whack and showing an atmospheric pressure reading so far off it's not even seen in the middle of a hurricane. That alone would explain most of the difference between the two dyno sheets but very few people paid attention and looked at the fine print and just assumed their parts made these giant power gains.

I've also seen many times where a company will do a baseline dyno run and then install their parts and immediately do another run that shows small gains. One problem is that the computer wasn't reset and then given time to adjust to the new component so the gains that were small to start with might evaporate once the computer has adjusted and compensated for the changes you've installed. Going along with that you'll see people get too wrapped up in dyno numbers and not realize that the 5 hp gain sounds nice on paper but is only a 2% overall change and might be well within a margin of error for the dyno runs. Or those who look at peak number gains without considering drivability and under-the-curve differences in power production. Dynamometers like many other testing and measurement equipment can be an invaluable tuning aid to compare and test changes on a car but they need to be used right and the customer needs to be able to interpret the results correctly.

Another common thing that I've seen is a lot of tuning shops or companies make multiple changes to a car and then produce dyno numbers showing great gains and maybe they even back it up with track times. The dyno numbers may be perfectly accurate too but the difficult part is interpreting where the gains came from since they didn't release test results with one change at a time showing how their different parts/changes interact and affect each other. If a company released an intake kit that replaced the entire air box, intercooler plumbing and the intercooler itself and showed a 20 hp gain and a consistent couple mph (or kph) gain in trap speed at the track it might develop a lot of interest and rightly so. But maybe all the gains came from just the intercooler or maybe just from the air box. The point is you as a consumer won't know unless you test it yourself and may end up replacing parts that don't help performance but instead just cost you more money. Or to go even further with that example, what if the intercooler change caused a small drop in power but the intake made up for it and then some. The kit as a whole would show a net gain but you'd be buying a part (i.e. the intercooler and tubing in this example) that isn't doing anything for you.

These are reasons why aftermarket upgrades whether they are from GM or not need to be carefully evaluated. Its okay to go off what a reputable company/vendor says, but do you know their testing procedures? Have they explained and provided a rich amount of information and specifics on their tests and explained what gains they saw and why they made the changes that they did to their parts, calibration/tune, etc.? Or is it just a mystery dyno sheet on their web site taking their word for granted. Same thing applies to private owners testing parts who post up here on the forum. Do you know how they tested and what they did to get their results? Will you or someone else be able to replicate those results on a different car?

All things to consider and think about when evaluating aftermarket upgrades for your car that can often be overlooked.


Thanks, but while I do consciously try to present things in as unbiased way as possible it's good to realize that even I'm biased towards certain things just like everyone else. That's why it's good to have discussions so you can see where someone is coming from and also see the contrasting lines of thought and their reasoning.

I realize that I'm biased for and against certain things, mostly due to my previous experiences, but you always have to be open to change and listen to what other people say and be willing to try different things. By doing so I learn new stuff nearly every day. Otherwise in the automotive world you may end using a solution that works and has worked great for years but may not be the best solution.

 

Get a job. JK! Thanks for the great write up.

 

You should just copy and paste your posts together and you will have your first novel! Just kidding...thanks for the insightful responses...

 

More great posts blackbird. I appreciate how you support or give examples for the points you try to make.

I actually work at a facility with several dynos, and have all the instrumentation available (temperature, pressure transducers, data logging capabilities) to do this type of testing. Unfortunately, I'm unable to use any of it for personal use, or even bring my car anywhere near the building. Life is such a tease sometimes.

 

sick amount of info. thanks for making me read all that! lol good stuff

 

oh yea that was some good stuff

 

Thanks for blowing my theories into the woods Blackbird. LOL!!! But it does all make sense. GMPP has built an engine that is using a lot of knowledge, technology and materials that was unheard of in the not too distant past. The LNF engine produces TWO HORSEPOWER per cubic inch. More than any production engine in GM history. And now they're increasing the horsepower by about 12% and torgue by a bunch more than that. And they gave it a 5 year, 100,000 mile warranty. It seems to me they know what they're doing.

My plan of attack is to wait for the GM kit and go from there.

Personal question Blackbeard. What do you do for a living?

Thanks for all your knowledge.

One thing I am sure of. You are pissing off a lot of aftermarket manufacturers. But maybe that's a good thing.

 

I've spent a bunch of money over the years buying that type of equipment and have a couple high end scan tools, various data logging and acquisition setups (pressure, EGT, wideband, etc.), 5-gas analyzer, and so on. I'll probably get around to checking a few things on the Cobalt but after getting carried away and having a lot of other "project" cars it's nice to have a great driving car with great power, stock. Add a nice bump in power with the GM kit and retain the warranty and I'm sold.

It's all too easy to get carried away when you start modifying a car. I went down that road with my SRT-4 of saying "oh, I'll buy this car as a daily driver and leave it stock so I can concentrate on modifying my older turbo Dodges" and that didn't last long. Heck, come to think of it I bought the then just pre-announced Mopar Stage 2 kit the same time day I bought that car. I guess it says a lot about the new SS and being so well rounded from the factory that I don't want to change anything.



I did just under ten years in the military doing a wide range of things from electronic maintenance, a few years as an instructor on electrical theory, and working on data systems and software testing. I've been out in the civilian sector for a couple years now but still work for the government providing IT-related tech support.[/quote]I've been known in the past of ticking off small, shady vendor/companies that make unsubstantiated claims. I have no problem with companies selling well engineered, designed, and tested products. But if you're going to sell a certain product that doesn't produce noticeable performance gains don't try to sell it as a performance product. Or if the gains will only be seen on cars with heavy additional mods (bigger turbo, etc.) then spell that out.

There's also many people who will blindly buy "upgrades" for their cars without doing research on the product. What's even worse is when a large group of people starts buying something and praising it but no one tests it for themselves to back up the manufacturer's claims. Then when someone does eventually question the product everyone else slams them for it. There's a reason the auto aftermarket is a multi-billion dollar a year industry and its not because every product is well designed and does what it's advertised to do. Companies have to make a living to stay in business but sometimes it is a case of caveat emptor or "buyer beware" and the consumer needs to understand this and look out for themselves before throwing money at their car.