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Old 02-17-2019, 01:57 AM   #1
Mike Meier
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Default Chevy Cobalt DF/S and maybe keep it streetable

After much debate I'm back in the Stock Eliminator game with the world's most expensive DF/S car.

A quick rehash of what was already discussed in the Stk/SS Tech section to bring everyone up to speed. I sold my Q/SA AMC Spirit last year. Bought a rolling dragster chassis with the intention of just buying a motor and just slapping it in there to run Super Comp (NOPE.....found out the chassis was twisted and though not that expensive to fix the chassis guy can't get to it til mid year, but I want grade points now).

On to the Stocker project and forgive me for the several tangents this may take.

My girlfriend had this 2007 Chevy Cobalt for a few years, hardly any miles on it due to her infrequent commute but we spent 3 years bringing it in for service to try and correct a gremlin in the electronics. What finally solved it in '16 was a dealership replacing the wiring harness after two other dealerships changed the ECU and TCM on several occasions. Fast forward to November of '18 she purchases a new vehicle but decides against trading in the Cobalt because the dealer only offered $500 trade in. I offer her a thousand after having already spent 2 years looking into the combo (bolt-on wise) and liking the potential (snuck out to the track with it in 2016 and ran a 16.90 in Drive on a humid night....1.30 over the index).
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Before I actually pulled the trigger on buying it, my big hang-up was finding wheels and slicks that reduced rotating weight and helped gearing. I ordered and tried-on a 13 inch dirt racing wheel that had the same bolt pattern but the back spacing didn't work out and they stuck out like a sore thumb. But I eventually found my drive wheel rims on Tire Rack, a pair of rims from Enkei.....it's a 10 lb ricer wheel meant for Honda Civics but it was the same bolt pattern (4 x100) and it was the right dimensions to put a slick on it (15 x 7). $466 later and those bad boys were at my door. Add in some Mickey Thompson 22x8 slicks and some 24 x 4.5 Mickey Thompson Front Runners ran the total up another approximately $850.......I told ya, worlds most expensive DF/S....the wheels and tires cost more than the car.

I did do some junk yard scrounging for the "front runner" wheels; fortunately the Chevy Cobalt donut rims are 15x4. Unfortunately it took over two hours at the junk yard to find two because every 4 lug Cobalt I'd come across was missing the donut. All the damn Cavaliers and Sunfires were 5 lug donuts.

Prior to all of this, back in November or December I weighed the car with myself in it at a CAT scale. It weighed in at 3,020 with the NHRA minimum weight being 2,830.

So today was the big day to finally bring the car out to Houston Raceway Park and make some runs. The only change I was going to make today was swapping from the street tires (45 lbs each) to the new slicks (25 lbs) and skinnies in the back (30 lbs). That alone was a 70 lb weight reduction coupled with some driver weight reduction of 25 lbs via diet, and clearing out some miscellaneous junk from the car (floor mats, engine cover, spare tire). I neglected to weigh the car on the first run before changing the tires but based on what it weighed a bit later I think I can reasonably approximate it.

So on to the results.

For my first run all I did was empty the trunk and pull the paper air filter. With the car in sport shift mode (start in "L", let it do the 1-2 shift, push the shifter into "I", let it do the 2-3 shift) it does a 16.50 in the humid 73 degree air. In hindsight I estimate my weight to be 2,890 lbs based on knowing the street tire/rim weights versus the racing tire/rim weights. The water temperature was at 207 F.

I went back to my pit spot and threw on the slicks / skinnies; which brought the car's weight down to 2,820 (which is 10 lbs under the minimum). This collectively picked the car up 3 tenths. I rang off three passes of 16.20, 16.18, and 16.22 over a two hour period with the water temp being in the 165 to 180 range..

This is very promising. Only 6 tenths over the index and nothing has been touched on the engine other than pulling the air filter.

The plan for next week is to order an exhaust header and down-pipe with catalytic converter. The stock exhaust looks pretty restrictive but I can't lose any more weight from the car otherwise I fall into a quicker class; so my idea is to have an exhaust place install a cut-out just before the cat then fabricate a low restriction exhaust / muffler. I can open the cut-out for racing Stock; leave it closed and leave on the heavy wheels to race in Street ET.

I'll see by next weekend how much ET I can pick-up with the header / down-pipe / cut-out then determine if my next step will be to have a higher lift cam installed (stock lift is .397 and FWDs can still go up to .430) or to try doing a computer tune with HP tuners, which I might need first anyway to run a NHRA Accepted fuel like 260 GTX or VP C-10.
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"World's most expensive DF/S" 2007 Chevy Cobalt....because suffering through owning an AMC Stocker wasn't enough

Last edited by Mike Meier; 02-17-2019 at 02:06 AM.
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Old 02-17-2019, 10:26 AM   #2
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Default Re: Chevy Cobalt DF/S and maybe keep it streetable

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
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Old 02-17-2019, 07:14 PM   #3
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Default Re: Chevy Cobalt DF/S and maybe keep it streetable

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Originally Posted by Mark Yacavone View Post
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?
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Old 02-17-2019, 07:31 PM   #4
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Default Re: Chevy Cobalt DF/S and maybe keep it streetable

whats the motor and trans ? I have tuned a few cars with hp tuners including my supercharged g8,, I will look it up
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Old 02-17-2019, 07:47 PM   #5
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Default Re: Chevy Cobalt DF/S and maybe keep it streetable

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.
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Old 02-17-2019, 07:52 PM   #6
Mike Meier
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Default Re: Chevy Cobalt DF/S and maybe keep it streetable

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

Its the 2.2 liter L61 engine and I believe the 4T45 transmission (automatic)
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Old 02-17-2019, 08:07 PM   #7
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Default Re: Chevy Cobalt DF/S and maybe keep it streetable

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Originally Posted by Dave Gantz View Post
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.
Maybe I can just have two identical length down-pipes since they are both options on this web site. One with a cat for street driving; the other I can swap on when I get to the track.

Hell, the annual inspection isn't due until September and the last D-4 divisional is in July; maybe I'll do a cat-less down-pipe until inspection time as long as it doesn't throw a check engine light. In reality this is just going to be used for driving to Baytown for the monthly bracket points races and to 4 or 5 LODRS.
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Old 02-17-2019, 08:26 PM   #8
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Default Re: Chevy Cobalt DF/S and maybe keep it streetable

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Its the 2.2 liter L61 engine and I believe the 4T45 transmission (automatic)
Looks like you have a 3.61 final drive and could use a 3.91 from an HHR, G6 or Saturn Vue
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Old 02-18-2019, 01:33 PM   #9
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Default Re: Chevy Cobalt DF/S and maybe keep it streetable

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Originally Posted by Mike Meier View Post
Maybe I can just have two identical length down-pipes since they are both options on this web site. One with a cat for street driving; the other I can swap on when I get to the track.

Hell, the annual inspection isn't due until September and the last D-4 divisional is in July; maybe I'll do a cat-less down-pipe until inspection time as long as it doesn't throw a check engine light. In reality this is just going to be used for driving to Baytown for the monthly bracket points races and to 4 or 5 LODRS.
You should be able to use a spacer for the rear O2 sensor to minimize check engine light problems when using a catless exhaust system.
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Old 02-18-2019, 04:27 PM   #10
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Default Re: Chevy Cobalt DF/S and maybe keep it streetable

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Originally Posted by Mike Meier View Post
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.
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