I have a brother that has a 1999 cobra. He was having a few engine problems, so we decided to have the motor torn down and rebuilt. So we sent the block off to an engine builder. Well we just got the motor back from being rebuilt by a reputable engine builder. He cleaned it up .20 over....and basically brought it back to stock form. Replaced the pistons, rods, rings, seals...pretty much everything that could be replaced to bring it back to stock specs.

Now that the engine is almost ready to start i have some tuning questions.

1) His motor was one of the ones that didnt get the intake fix...so we hand ported the intake. (Does this modification require a tune due to the smoother inlets?)

2) We installed a JLT CAI but are using the stock MAF sensor....(would it be a good idea to get a tune after this mod?) I know the tubing is much larger than the factory intake...BUT the Mass Air meter is still factory..... Would this effect the air to fuel ratio enough to require a tune?

Mods to the car so far

1) JLT CAI
2)Ford Racing shorty headers
3)Mac O/R X pipe (no catylitic converters)
4)Flomaster 2 chamber

**** Would these mods be enough for him to NEED a tune? or is he fine without?


I own a 2007 GT and use the XCAL2 tuner and am using Bamachips tunes for the mods I currently have.

Who can my brother deal with as far as getting the car tuned? Are their tuners out there that you cobra guys use? Do they have mail order tunes for the XCAL2 for his car? Any and all suggestions would be much appreciated.

*** Also how much are these 1999 cobras detuned from the factory? I know when I installed my CAI and tune on my S197 I picked up 27 Rwhp....Would his 4v pick up the same? Thanks!!

Jarrod
Tulsa Ok

 

I believe Ford uploaded a new tune as part of the fix when they did it. He could probably get by without one but it may be on the lean side. If It was my car, I wouldn't hesitate to get it on the dyno to at least check the A/F ratio. Im sure he could make more power with a good dynotune though. A mail order tune is pretty iffy.
Not sure about tuners out that way.

 

A Few that I have talked to about this argue that the Mass Air is the at the factory setting so even though the JLT tubing is larger...No more air is getting in than the MAF will allow (is this entirely true?). They also ported the intake....not sure how much this would effect the A/F ratio if any.


Mail order tunes for our S197s have been dead on, but Im not sure what tuners around the country are any good with the Cobras.

 

Don't know anything about brands and diameter, but physics still applies. You have 3 variables of flow through pipes:

1.) Orifice
2.) Pressure (vacuum in this case)
3.) Fluid (intake air)

You can vary flow by changing any one of these (i.e. cold air intake). If you drop the inlet air temperature you effectively change the fluid. If you change the tubing you change the pressure (pressure drop in this case) and by keeping the same orifice and changing pressure and fluid you effctively change the velocity.

So, the MAF uses a thermistor to generate an electrical signal signifying the air flow into the motor. This will be the input to the Engine Control Mangament for adding fuel (i.e. modifying the fuel curve). When you affect the flow rate into the engine the MAF will notice and thus your "tune" becomes a factor.

Typically unless the piping from the MAF to the intake, or the intake track is modified you won't need to retune. Since you "ported" the intake track you may see slight variations, but nothing the existing ECU wouldn't compensate. (did this on a 1997 TA Ram Air once). Because your engine is drawing vacuum and the restriction of the airbox is gone, you will see a significant flow increase through the MAF. The MAF undoubtedly is a restriction, but the engineers at Ford used the whole system to decide how to set the fuel curves, and even though it "should be ok", I would make darn sure you weren't running lean before I ran this thing too much.

As others have stated, you most likely should spend the money on a dyno test and check the A/F to be sure, especially since your setup is customized by you and you can't simply download info from others.

I hope this was helpful and you didn't fall asleep.

 

I would deff get a tune.
you'd make more power and it wouldnt be hard on your engine.
you really need a tune if you have headers and a cold air intake.

 

you hould be able to start the motor and run on the factory programming for the break in period, but after that you should get a tune.

 

Thanks for all of your information guys! Shaun Beauchamp ....didnt fall asleep and I followed most of it...Thanks! Your saying that the I have changed variables that the computer may not be able to compensate for fuel and air...although the ECU "should" be able to compensate for it..theres still a possiblilty that the curves have been changed and we've done enough to warrant a tune. OR at least check it out on a dyno.

We will most likely run the break in period and then schedule to have it dyno'd and check A/F and make sure the timing is in check.

***So even though the MAF is a certain size...when the tubing before and after is changed as well as porting the intake (changing air velocity)...its sometimes enough that the computer cant compesate and the possiblity of running lean is there? Am i comprehending this correctly?

 

Your deduction is spot on. Unless you have extensive experience with how the ECU is affected and compensates for intake track changes, then you're flying a bit blind. Having it dynoed and checking A/F is a safe way to ensure extended life.

 

Ok so we got the motor in and shes running fine. BUT now we notice some purplish tinted smoke (ie rich unburned fuel) coming out of the tailpipes on a load. Car is surging a little bit as well.

Check engine light is on and I pulled the codes (there were 3 of them)

· P0136 02 Sensor Circuit Malfunction (Bank I Sensor 2)
· P0141 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
· P1000 - OBD-II Monitor Testing Incomplete

Is bank 1 sensor 2 one of the back O2s (if so which one?) Also shouldnt the MILs delete the rears and shouldnt be throwing a code? If anyone has any opinions or can shed some light on this please do.

 

In my unprofessional opinion, I wonder if the MIL's are correctly installed? If not they might be screwing with the sensor signals or something. That is just a wild guess though with really no basis or experience with those things.

 

unfortunately the MIL's arent very good. i have them on my 98 cobra and i still get codes for not having converters and for my rear 02 sensors being further downstream than factory.

 

Changed the o2 to factory ford. still having trouble but the engine has not thrown the code again so i think that is fixed but still smoking. but i am second guessing my self. i think it is a oil buring problem from the rings not seating yet.
Was searching on youtube to find a video of a mustang that is having similar exhaust smoke on start up and load. The video I am linking is the closest to the color of smoke that is comeing out of my cobra.
My vehicle doesnt blow this much smoke out the exhaust as this car, but this is the color that closely matches my own.

http://www.youtube.com/watch?v=h2sFIj8iEeI

 

If you just built the car or the car sat for a very long time, you get some smoke. Even my 2006 smokes a bit on startup when sitting for a week or two.

I would say that if it cleans up and doesn't get worse, then it should be fine. Maybe someone can chime in on where the bleed down comes from on these motors.

Later,

Shaun

 

Thanks Shaun,

It smokes on startup and billows out the back when on a load...I mean so much that it blocks out the sun hehe. or at least the car behind me.

Spoke to the engine builder warranty guy today and he let me know that this is perfectly normal and that the rings probably havent seated yet. Said they probably wont seat until the 500mi mark. He said to drive her normal...dont worry and give him a call after 500miles.

So I guess we'll see. Im currently at 200miles or so

 

Weird we took the car out last night and got on her a bit to see if we couldnt force the rings to seat hehe.... this morning on startup there was a little smoke but by lunch time We got on her and Zero smoke! took her out this evening and again no smoke...even when we got on her a bit. Usually we would black out the sun, but it looks as though the rings decided to seat themselves for the most part. Havent had anyone behind me to see if its smoking at all in the upper RPMs but from what I can tell from the mirrors...no smoke.

a little wierd but im glad

 

Maybe that is what it needed to seat the rings? I was thinking about suggesting to you that you need to beat the %$$# outta that thing and see if that helps. Glad it seems to have worked!!

 

hehe yeah sometimes they need a little push to get things settled I guess

 

jarrod, updates??? hows things going with the car? definitely interested since i should get my car back hopefully before end of jan with a new engine.