Turbocharging FAQ

[gibsonj4]

Well, I decided to do a FAQ because of a lot of Forced induction posts on the site. Maybe you will find your answer on here. If you have another question about turbocharging your cobalt, feel free to pm me and I will do my best to answer your question. Again, these are just some of the most common questions to be asked.

1. Why should I turbocharge instead of supercharge?
Turbocharging is an effective way to add power to your vehicle. Turbos run off exaust gases generated by the engine burning fuel so you are effectively using power to make more power. This is similar to the idea of a supercharger, however, in a supercharger the parasitic loss is greater because the supercharger is belt driven (usually it can also be chain driven) and takes power from the engine crank to turn the pulley and compress the air. For an extensive answer to this question read this: Supercharger vs. Turbocharger

2. What Turbo kit's are offered for my car?
There are currently two kits offered. The Alpine Developement Kit which utilizes a 5th injector system and runs off a piggyback unit WAS offered in 2007 but it seems that either 1. AD has gone out of business or 2. The kit has been discontinued because I have searched for their kit and located their homepage which is not up and running anymore. The second kit is offered by Garrett. It is important to note that the Garrett Kit is the same kit as the one offered by Hahn. In effect, the Garrett kit is the Hahn kit and vice versa. The Kit is available in different stages meaning each stage includes different integral parts i.e. the GT Tuner kit offers almost a full kit minus a boost gauge, larger injectors, and fuel management while the Alpha Kit includes all these things. These kits are offered for the L61 (2.2L) Manual trans only 2005-2006, the LSJ (2.0 SC) is in developement by Hahn at the moment, and the 2.4L SS/NA automatic and manual as well as the G5 GT that shares the same engines.

3. Can my car withstand a Turbocharger?
This is sometimes a question that is overlooked and people just slap on a turbo kit without thinking and crank up the boost. There are several factors that we have to look at:

-Drivetrain strength (axles, clutch, mounts)
-Ignition (Colder Plugs, Ignition timing)
-Bottom End (Connecting rods, pistons, headgasket)
-Valve Train (Valves, locks, retainers)
-Fuel Management (Injectors, Fuel pressure Regulator, fuel pump, tuning software)

These are just several things you need to think about before running boost. What are your goals? On 2.2's the rods are good till 250hp~, the stock manifold is good till roughly 15psi of boost (so I've read), and stock axles are pretty weak in the 5 spd transmission in the L61's. Bottom end strength is important because if you are going to run higher boost levels, there is an effective increase on stress on your internals because of the newly produced power.

4. What is compression?
Compression or commonly called the Compression ratio can be defined as the engines potential to make power. When the engine turns, the piston is at some lowest point at it's stroke down and then at it's highest point when the engine turns again at it's stroke up. What the compression ratio is is the ratio between the cylinder's volume at the engines lowest stroke and the cylinder volume at the top of the stroke. So for an L61 our compression ratio is 10.0:1 meaning at the bottom of the stroke, the cylinder volume is roughly 1000cc's and at the top it is 100 cc's.

5. Why is lowering compression better for running boost?
Though you can run boost on a higher compression engine (12.0:1 even!), and it will produce some great low-end torque, you will have to worry about a couple things. For one, your engine is gonna run a lot hotter and your intercooler system better match all that heat you are dissapating from the new boost that is being added. By adding more oxygen, you are getting a quicker burn and producing more power but also more heat. Secondly, you will also have to worry about the ignition and knock which is the next question.

6. What is Knock and why is it harmful?
Knock, also known as detonation, is the random explosions in the combustion chamber because of the different air/fuel mixture. The reason this is bad is because the pressure in each cylinder varies greatly up and down. This variance can cause engine damage. A higher octane rating of fuel can reduce knock and that is why higher compression engines and Forced induction engines run higher octane fuel.

7. What is a wastegate and what does it do?
A wastegate is basically a tool to limit boost pressure in the turbo. A wastegate takes some of the exaust gases away from the turbo to stop it from spinning and creating a huge amount of boost. Basically, it's like a governor for the turbo. It limits the boost level so it doesn't continue to rise exponentially as the engine revs.

8. Why does everyone says theres no "tuning?" What is tuning?
This is a huge factor for our cars, especially those of us with L61 equipped cobalts. It is important to define what tuning is. For our applications, we are mainly concerned about fuel management. That is, controlling the injector duty cycle to match the air we are delivering into the combustion chamber. Our Air/Fuel ratio stock is around a 14.6. We want to stay around this mark. Running higher, we run to lean and running to low we run rich. It is possible to guesstimate the fuel needed for delivery through a fifth injector but this is a dangerous and unreliable system. The ignition timing also has to be changed so the system doesn't pre-ignite causing engine damage. There are many tuning options for other vehicles such as HPtuners, Megasquirt, the AEM FIC, and SCT. Now, we have the SCT handheld unit, Megasquirt, and the AEM unit Fuel/Ignition controller out for our cars. The SCT is available with the 2005-2006 L61 turbo kit's sold by hahn. I have not heard of anyone using megasquirt with the cobalts yet. I know I will be going with the AEM unit.

9. How does the AEM FIC control fuel delivery?
The AEM unit is a great unit because it allows someone to run boost with stock injectors. Now, it is smarter to replace the injectors and regulate this new fuel pressure with an aftermarket fuel pressure regulator. What the AEM unit does is it intercept the inector pulse from the ECU, and changes the fuel delivery from there. It allows the user to change the injector pulse to meet their fuel delivery needs and tune until their A/F is a desirasble 14.6 or close to it.

10. What is Trim? A/F?
The trim of a turbo is the ration between the turbo's inducer and exducer of the turbine wheel and the turbine wheel. More importantly is the A/R. The A/R or aspect ratio is the ratio for a turbo housing size vs. the inlet of the turbo. Larger A/R makes the turbo spool later while the smaller A/R spools quicker. A small A/R turbo is better for our engines allowing it to spool quicker and supply power quicker at low RPMs.

11. What are the main components of a turbo build?
This is just a short list of components. There is a great turbo how-to on ecotec forum written by a former member NJHK. The major parts for a turbo include:

-The Turbo
-Intercooler
-Intercooler piping
-Wastegate (if externally wastegated)
-BOV (Blow off valve)
-Downpipe
-Turbo Manifold with a fabbed or production flange for the turbo.
-Larger injectors
-Fuel Regulator
-Tuning (Piggyback, Standalone, or a Suite such as HPtuners)
-Boost controller (not essential)
-Wideband or an A/F gauge.

I will be adding some FAQs to this list when I have time. Again, any questions just PM me and I will respond as soon as I can.

[Montecarloman]

Originally Posted by gibsonj4

Our Air/Fuel ratio stock is around a 14.6. We want to stay around this mark. Running lower, we run to lean and running to high we run rich.

With a stock engine sure, however most high outpout engines like a richer mixture. Typically at idle 14.6/1 is perfect but at speed running down the road under full load you really want a richer mixture to help take some of the heat out. 12/1 is the standard number commonly bounced around. Also the lower the number the richer the fuel air mixture. Great write up, good information. That was the only thing that jumped out at me.

[gibsonj4]

Originally Posted by Montecarloman

With a stock engine sure, however most high outpout engines like a richer mixture. Typically at idle 14.6/1 is perfect but at speed running down the road under full load you really want a richer mixture to help take some of the heat out. 12/1 is the standard number commonly bounced around. Also the lower the number the richer the fuel air mixture. Great write up, good information. That was the only thing that jumped out at me.

I just was also taught you wanna try to stay around 14.6 no matter what. Of course it will vary but whaat I was sayin it we wanna stay around this mark. Thanks for bringing it up though! Clarified for the readers

[IMADreamer]

Now if you can teach us all compressor maps everyone will be all set.

[gibsonj4]

hahaha hmmm that may be out my reach I'll look into it. hey Ima pm me some FAQs if you come up with anything. Do you know how to read compressor maps? I Know that the pressure ratio goes on the vertical y-axis and the x-axis is the corrected air flow in lbs/minute. I also know that usually if you look at a compressor map, there is a line that is drawn up from initial air input in lbs/minute and levels off. If the line goes off the grid of the map, then the turbo sucks at high revs. If the line enters the grid early and stays on the grid, then the turbo is a good fit for the power band since the compressor mapping goes from intial RPM's to redline usually. Correct me if my understanding is wrong in any part of this.

[xxcooljay23xxg5]

WTb a diagram of intercooler piping for the 2.2 autos. Hell if not a manual would work. >.>, atleast then ill be able to get an idea on how imma turbo mine X(

Good write up tho gib. Im impressed.

[IMADreamer]

Originally Posted by gibsonj4

hahaha hmmm that may be out my reach I'll look into it. hey Ima pm me some FAQs if you come up with anything. Do you know how to read compressor maps? I Know that the pressure ratio goes on the vertical y-axis and the x-axis is the corrected air flow in lbs/minute. I also know that usually if you look at a compressor map, there is a line that is drawn up from initial air input in lbs/minute and levels off. If the line goes off the grid of the map, then the turbo sucks at high revs. If the line enters the grid early and stays on the grid, then the turbo is a good fit for the power band since the compressor mapping goes from intial RPM's to redline usually. Correct me if my understanding is wrong in any part of this.

I think you have the right idea. I have a very basic understanding of compressor maps and that's it.

I will look through some of the things I had typed out at home and see if there is anything that can be added. I will pm you anything I come up with. I'm glad you put one up because I'm having problems getting enough time to work on one.

[gibsonj4]

I'll try to find a pic for you jay

gibsonj4 added 0 Minutes and 46 Seconds later...

yeah I had 35 minutes between class so I wrote this up real quick.

[xxcooljay23xxg5]

awesome thanks man. Just trying to see on how imma get this to work this summer. I shall turbo my g5 auto weither it well kills me or... Kills everyone else.

[gibsonj4]

haha well i mean it could work the problem is of course the room because of the larger transmission and you need a transmission cooler because that automatic is gonna be puttin out a lot of heat. Intercooler piping could be a problem but there's always a way to fit the piping down to the bottom of the front bumper.