Chevy Cobalt DF/S and maybe keep it streetable

[Mark Yacavone]

Sounds like you'll get there, Mike
Not sure what converter that takes but if you find out.let me know. You should able to come up with something looser but retain the lock -up.
Be careful on the cam .You don't want to kill much torque but bump the lift up . Street and strip pattern with about 220 duration lobes. Talk to Chris Padgitt at Bullet.
I wouldn't use a cut out, per se. Make the header extension pipe end with a flange , where you can bolt the street exhaust back on , or be able to play with collector extensions that I imagine would be fairly long.
Good luck

[Mike Meier]

Originally Posted by Mark Yacavone

Sounds like you'll get there, Mike
Not sure what converter that takes but if you find out.let me know. You should able to come up with something looser but retain the lock -up.
Be careful on the cam .You don't want to kill much torque but bump the lift up . Street and strip pattern with about 220 duration lobes. Talk to Chris Padgitt at Bullet.
I wouldn't use a cut out, per se. Make the header extension pipe end with a flange , where you can bolt the street exhaust back on , or be able to play with collector extensions that I imagine would be fairly long.
Good luck

I think I will wait on the cam because I want to avoid opening up the engine as long as possible.

Regarding the headers, here are my options:

1.5" versus 1.75" primaries;

2.5" versus 3" exit for down-pipe

Short, mid-length, or long tube primaries (caveat is that the long tube header is only 1.75" primaries).

The other challenge is keeping it streetable by keeping the catalytic converter. I wonder if I could have the exhaust shop relocate the cat further back in the system, like just in front of the muffler that way I can still have a longer, unobstructed down-pipe; and just unbolt the cat / muffler section from a flange.

Thoughts?

[MikeMoller]

Originally Posted by Mike Meier

I think I will wait on the cam because I want to avoid opening up the engine as long as possible.

Regarding the headers, here are my options:

1.5" versus 1.75" primaries;

2.5" versus 3" exit for down-pipe

Short, mid-length, or long tube primaries (caveat is that the long tube header is only 1.75" primaries).

The other challenge is keeping it streetable by keeping the catalytic converter. I wonder if I could have the exhaust shop relocate the cat further back in the system, like just in front of the muffler that way I can still have a longer, unobstructed down-pipe; and just unbolt the cat / muffler section from a flange.

Thoughts?

im guessing, but I would certainly lean towards the 1.5 / 2.5 combo. For lower hp cars, smaller is almost always better. You may also want to invest in some type of fuel pressure regulater that will allow you to adjust fuel pressure to the injectors.

[Mike Meier]

A few quick updates on my parts I ordered in the middle of the night last night:

Ordered HP Tuners with 2 credits.

Mid-length headers with 1.5 primaries and 2.5 down pipe (with catalytic converter because "street legal")

I have the parts for a fuel sample valve but will leave that to a professional to install because I might set the whole thing on fire.

I am strongly considering running Sunoco 260 GTX (as opposed to VP C-10).

[Mike Meier]

Quick update:

Unfortunately the test and tune night at Houston Raceway Park this past Friday was rained out so I haven't had the chance to make a full quarter mile pass with most of the modifications; but the local brackets are eighth mile and I have gone as quick as a 9.96 at 69.11 MPH.

A good number of my eighth mile passes were in 3 to 4 hundredth spreads with each respective major change.

Done:

Slicks, front runners, and light weight rims
Mid-length header (1.5 inch primaries, 2.5 inch collector) and down-pipe with 400 cell catalytic converter
Removed upper intake manifold and just running open throttle body (though car is now throwing DTC for the MAF Sensor
Fuel sample valve had been installed
Best run was at 2,850 LBS running 93 octane

Have not done:

Did not flash the ECU with HP Tuners. Walt Walker made some changes to the tune related to when the cooling fan comes on and how much torque is applied (he did not mess with any fuel related tables); it would not sync up properly as it was not recognizing the credits that I purchased with the device. As soon as I can get tech support to resolve the issue, I'm flashing the computer.

Need to drain the remaining 93 octane from the fuel tank, change the fuel filter, and replace with Sunoco 260 GTX. For the record, attempting to run a car that gets 28 MPG until it runs out of fuel is such a pain in the butt. I drove the 30 miles home from Baytown with the Low Fuel warning hoping it would run out of gas so I could dump in the race fuel to make it the rest of the way home.

When the mechanic across the street installed the header and down pipe, he hooked it into the stock exhaust, so I need to open things up a little.

Going to buy a tow vehicle on Monday because the Suburban crapped out in December. Need to get that inspected and registered by Wednesday so I can high-tail it out to No Problem Raceway's Thursday Test and Tune to try and get this car under the index.

[Mike Meier]

Made it back from Chandler, AZ an extra $700 lighter in the wallet due to a breakdown on I-10 with this ramp truck I bought; and probably in for some more as it's in the shop getting the check engine light related stuff taken care of. My comment on this; yes I knew what I was getting into but that's why I bought a truck with a 350 engine....everyone can work on it and parts are easy to find. I can have Jegs or Summit ship a long block to me for about $1,600 if this thing decides to spin a bearing or kick a rod. Ultimately I was happy to hear that the No Problem Raceway LODRS was postponed because I wouldn't have been about to make it out there.

But I digress....back to the DF/S

The Cobalt is completely switched to Sunoco 260 GTX. I drove to the track Friday night and managed to get a best of 26.8 MPG to and from.

The one thing that went wrong was that I couldn't unbolt the resonator from the down-pipe to go completely unmuffled. One of the nuts holding together was at an awkward angle and I wound up rounding it off with my impact wrench. I'll just have an exhaust shop cut it off.

I'm almost at the index. I started off with a 15.90 @ 85 MPH off the bat, followed by 15.94 @ 84, 15.86 @ 85, 15.89 @ 85, and 15.98 @ 84 (heat soak and fog was rolling in). Although the barometer was moving around a tick between 30.02 and 30.05; the humidity was parked at 93%; dew point at 59*, and temperature only varied between 61 and 62 degrees.

What was promising about tonight was that my sixty foot times were in the 2.32 - 2.35 range in this "meh" air and I went quicker in the quarter compared to two weeks ago; but two weeks ago my sixty foot was quicker. I hope that correlates to hitting the index or better when the air is better and they have a LODRS track prep. I still haven't even reflashed the car with HP Tuners because I was on the road and couldn't call their customer service guy about getting the credits on there to work.

[rocketolds400]

Very cool! Thanks for the progress updates and info.

I've been looking for a cheap daily driver, and this thread is making a Cobalt look pretty good...

[Jakedog55]

Can the Cobalt be run in EF/S? Thanks

[gmonde]

whats the motor and trans ? I have tuned a few cars with hp tuners including my supercharged g8,, I will look it up

[Dave Gantz]

Sounds like a fun project, Mike. Where Stock came from.
Moving the cat back may not work. I'm no expert, but I think they need to be a certain temp be effective, and can't achieve that if they're too far back.