Pulley and Chip Question

[Sonic Cobra 03]

Sorry, I know i am full of questions, but I am so excited about modifying my cobra. What size S/C pulley would you switch to? What are the adv/disadv? Also i heard that the chip can be specifically tuned for your mods. Should I wait to get that after i have done alot, or is ok to get it now?

Thanks!!!

[Brad12]

It depends on what pound pulley you are going with,also try to plan out all your mods so the chip can be burned for all you are going to do.2 lb pulley you should be safe but 6 lb you will want the chip as well.Just make sure you keep an eye on you air/fuel ratios so as it does not run too lean,these cars are VERY rich running from the factory.Too lean is what will cause engine damage.Also change out those stock plugs,they are terrible.They break up at high RPMs.Also consider doing the lower crank pulley,METCO makes an extremely well made kit.

[rachrse]

Sonic Cobra If you know about how much horsepower you want to get I would go to Amazon Racing .com and ask Rick what you need to do to get there. He is verry helpful and will explain things to you. He will also custome tune a chip for you.I changed pulleys and installed a chip after I had put around 2000 miles on my 03 Rachrse

[DaleM]

When you install the chip have your pulley, intake(throttle body if you go there) and gear mods done simulateously (expensive but not as much as a new engine). The problem you run into is a very lean condition when under load without the chip. The injector pulse width and duty cycle is modified by the chip to give you a nice, safe 12.?? A/F ratio and fuel curve.
JDM has a nice combo that uses a SuperChip with two programs if you like.

v/r,
Dale

[payjota]

Why change the lower if it is so hard to get to. If you can get 5-6lbs from the 2.93 what is the advantage of changing the lower pulley and what size would be changed to get the same boost lower pullley combo?

[dwtalso]

Divide the lower pulley diameter by the upper pulley diameter and you'll have a ratio that you can use to compare any combo you'd like. Combos with the same ratio are going to make the same amount of boost. For example, the stock lower is 7.5" and with a 2.93" upper the ratio would be 2.56. That means to get an equivalent ratio with an 8.5" lower you'd need a 3.32" upper.

[EbloomPonycar]

One of the problems with changing the lower is overspeed of other components. Fix a budget and talk to several shops. It seems the general consensus is pretty standard on the 03-04 Cobras. I think was last months 5.0 magazine had a nice article on modifying these cars. They went through each upgrade and dyoed to show results. I did pretty much the same items and am extremely please with the results and the retention of great driveability. Some of the cars at the Mountaineer Madness were making 500 - 600 RWhp. After all said and done the tuner has alot to do with bringing it all together. Spend the money to dyno tune. I have seen several dyno sheets with A/f ratios all over the place.

[dwtalso]

The only accessory that overspeeds is the alternator. Metco and others sell an underdrive alternator pulley that's inexpensive. My alternator with it's OEM pulley lasted about 20k running overspeed (9" lower).

[payjota]

How much of a diff. is the 2.76 that billit flow sells then others selling the 2.8. If i am not going to change the bottem pulley what is the best setup.

[TDS-03]

Why change the lower if it is so hard to get to. If you can get 5-6lbs from the 2.93 what is the advantage of changing the lower pulley and what size would be changed to get the same boost lower pullley combo?

One of the main advantages to changing the lower is that the upper pulley can remain larger to attain the same level of boost. The smaller the upper pulley the more likely is that it will slip at higher RPM's. Slip lowers boost, or causes it to flux and so does the HP. Spark blowout is common with higher boost as well.