Need advice! 2003 Cobra w/ Procharger

[brandon_s0854]

Hello All,

I'm new to the forum and have a ton of questions regarding my new cobra. Let me start by telling you about the new vehicle. It's an 03 Cobra with a P1SC-2 unit and Flowmaster cat-back system installed. I have no idea if there's anything else, because the vehicle was a repo and I never got to actually talk to the previous owner.

As of right now, the thing absolutely flies from 5k to 7k rpms, but it's a little sluggish below 4k. I'm not looking for people to tell me that I should buy a Whipple/KB or find an Eaton. There's been a large investment already into changing to a centri, and the thing flies on a long straight, but I'm looking to further improve it without changing blower types. I'm considering upgrading to an F1A, but that is further in the future. I've done quite a bit of reading and researching as to modifications that can be done to help this and with what little info I've found regarding this particular setup, there are three main things that can be done to help the situation quite a bit.

1) 4.10 Gears - Helps get the rpms up faster and will feel like there's more torque.

2) Put on 01 cobra/03-04 mach 1 lower intake, which have longer runner lengths that will make more power in the lower/midrange.

3) Increase compression ratio, which will wake up the engine in general, but especially in the lower/midrange.

My main question is regarding the compression. Is it possible to get a decent increase in compression without changing the heads on these vehicles? How much increase can I get by milling the stock heads without having to worry about destroying the engine? What would be the cost to do this? If I can't modify the stock internals to do what I want, what would be the cost to purchase the necessary parts and them installed? (Approx ofcourse)

I'm looking to end up between 9.5-10:1. Again, not looking for people to tell me I should do more or less; just trying to find more out about the process. Also, any other useful information or suggestions would be much appreciated!

Thanks again! I'm really enjoying being a part of the mustang community and driving one ofcourse, but I'm looking to make this vehicle the best it can be with what I have to work with.

 

[Brutal Metal]

The gears, don't bother with the other things mentioned!
Show some pics of the engine bay..

 

[01yellercobra]

I think you should track down the previous owner and smack them across the head. Who pulls off an eaton only to put a P1 on there? Not to be an ass, but are you 100% positive it's an 03 Cobra?

Out of your choices I would do the gears. You can deck the heads on these motors, but it would take a lot of material removal to make a difference. It would be better to swap pistons. Since you're not looking to do that right now I'd do the gears.

 

[Whistler98]

Gears. 4.10s will def wake it up. If that doesn't work good enough then go from there. How much boost are you running?

 

[pacific4v]

Pulley it down, put a wastegate in the intercooler piping to regulate boost. With a smaller pulley it'll build boost lower in the rpms, but the wastegate will let u regulate the boost if u don't want to run the amount the small pulley will make. 4.10s would be easier tho.

 

[brandon_s0854]

Gears. 4.10s will def wake it up. If that doesn't work good enough then go from there. How much boost are you running?

I have no idea. I plan on taking it to get tuned shortly. I can tell you the factory boost gauge is buried at about 5k; so I would assume it's about 15 psi, but that's just a rough guess.

 

[brandon_s0854]

I think you should track down the previous owner and smack them across the head. Who pulls off an eaton only to put a P1 on there? Not to be an ass, but are you 100% positive it's an 03 Cobra?

I agree; I wish I could. Also, yes I am 100% positive it is an 03 Cobra. The P1SC-2 is not a bad blower; it's impellar is improved over the standard P1. It's supposed to make 550 rwhp, but 550 rwhp on a centri feels like 300 until you really get in to boost. I am curious as to how difficult it would be to put an F1A cog drive on it.

According to what I've read, the fuel intake/a2a IC and increased compression should make a big difference, but I was hoping to hear from someone with experience since that's probably about $3k in modifications. Don't want to spend that much to make an extra 50hp and hardly any better low/midrange response.

 

[InKogNigRow]

Hey Brandon Im In midland Id like to check the car out. I have an 03 cobra too.. are you on baycityrides or illicitspeed? there's some quick local car's around you may want to meet..

My best guess.. is pulley it down.. with a waste gate and some gear's.. my buddy is making 734 to the tires in his mach 1 with head work cams and a d1sc..

 

[InKogNigRow]

my name is TrouserSnake on the other boards.. my Plate says' TROUSER keep your eyes peel for me..

 

[97desertCobra]

Gears. Dont bother with the other things mentioned. However, the only other option I would consider would be swapping to an 01 intake and then run a FMIC as the factory intercooler can suffer from heat soak on back to back runs. Plus the Procharger sheet metal intake really kills low end power.

Personally, I wouldn't run a cog setup on a street car. 8 rib and proper alignment will take you pretty far. Past 650rwhp I would look into a dedicated drive set up.

For increasing compression I would swap pistons but obviously thats pretty involved and you will want to wait to do that.

 

[02blownGT]

Dont raise the compression raise the boost it has the same effect and will cost alot less.Boost=compression.Unless you run a ton of boost 20psi+ and wastegate it you will never have the instant TQ that you want with a centri.Milling the heads is more likely to cause detonation since it isnt really a performance mod its what people do to save $$ when they should buy new heads.Like said above get 4.10s or 4.30s and you will see it will feel like a new car.

 

[brandon_s0854]

Dont raise the compression raise the boost it has the same effect and will cost alot less.Boost=compression.Unless you run a ton of boost 20psi+ and wastegate it you will never have the instant TQ that you want with a centri.Milling the heads is more likely to cause detonation since it isnt really a performance mod its what people do to save $$ when they should buy new heads.Like said above get 4.10s or 4.30s and you will see it will feel like a new car.

Ok so as of right now, gears and intake/intercooler are definite mods. I'm not sure how you figure milling heads isn't a performance upgrade. Obviously, new pistons would be better, but either way you're raising compression, which is still a performance upgrade.

There are lots of people (that I've read) that are running high 9's low 10's for compression in combination with a centri that have no problems with detonation as long as the tune is right and you're using premium fuel. And I also thought I read somewhere (can you tell I've been reading alot?) that it's not actually true that boost raises compression, but increasing compression does restrict the amount of boost that can be safely ran. Can someone chime in on this?

 

[01yellercobra]

Ok so as of right now, gears and intake/intercooler are definite mods. I'm not sure how you figure milling heads isn't a performance upgrade. Obviously, new pistons would be better, but either way you're raising compression, which is still a performance upgrade.

There are lots of people (that I've read) that are running high 9's low 10's for compression in combination with a centri that have no problems with detonation as long as the tune is right and you're using premium fuel. And I also thought I read somewhere (can you tell I've been reading alot?) that it's not actually true that boost raises compression, but increasing compression does restrict the amount of boost that can be safely ran. Can someone chime in on this?

From what I understand it's dynamic compression that you're raising with increasing the boost. I'm sure there's a formula somewhere to figure it out. I'm running 9.5:1 in my set up right now. And I wish I had gone closer to the stock ratio of 9.8. But I haven't had any problems. The higher compression can restrict the amount of boost and timing you can run depending on the fuel. But it helps down low where there isn't much boost with a centri.

 

[brandon_s0854]

From what I understand it's dynamic compression that you're raising with increasing the boost. I'm sure there's a formula somewhere to figure it out. I'm running 9.5:1 in my set up right now. And I wish I had gone closer to the stock ratio of 9.8. But I haven't had any problems. The higher compression can restrict the amount of boost and timing you can run depending on the fuel. But it helps down low where there isn't much boost with a centri.

Good info here; thanks. Are you running an 03/04 cobra as well? Just to get some perspective. Did you notice a nice improvement after raising compression?

 

[01yellercobra]

Good info here; thanks. Are you running an 03/04 cobra as well? Just to get some perspective. Did you notice a nice improvement after raising compression?

No, I'm running a 2001. I really can't say anything about differences. I went from a 4.6 to a 5.3. While the 4.6 was at 9.85:1, the 5.3 makes up the slight loss in compression with cubic inches. So the motor has a little more low end then the 4.6.

 

[02blownGT]

Ok so as of right now, gears and intake/intercooler are definite mods. I'm not sure how you figure milling heads isn't a performance upgrade. Obviously, new pistons would be better, but either way you're raising compression, which is still a performance upgrade.

There are lots of people (that I've read) that are running high 9's low 10's for compression in combination with a centri that have no problems with detonation as long as the tune is right and you're using premium fuel. And I also thought I read somewhere (can you tell I've been reading alot?) that it's not actually true that boost raises compression, but increasing compression does restrict the amount of boost that can be safely ran. Can someone chime in on this?

MIlling heads consists of putting the head on a huge belt sander,usually to even out a warped head and is not as exact as doing it the right way.raising boost and using a wastegate will provide you with the outcome you are looking for as far as the engine is concerned.I have seen a 03 cobra pull 18psi out of a p1 but you wont get much more than that.

 

[Crackerballer]

I am surprised no one said long tubes. Get you a good set of long tubes and better exhaust when you turn the boost up. You could probably add a pulley equivalent to 5 pounds and only jump 2-3 but still see a better power increase. Plus you get the great sound and the headers will be beneficial for any upgrade minus turbo.

 

[01yellercobra]

MIlling heads consists of putting the head on a huge belt sander,usually to even out a warped head and is not as exact as doing it the right way.raising boost and using a wastegate will provide you with the outcome you are looking for as far as the engine is concerned.I have seen a 03 cobra pull 18psi out of a p1 but you wont get much more than that.

Who's been milling your heads? To be done properly they should be done on a milling machine. If the shop is doing it correctly then it's as exact as anything else. Removing a certain amount of material makes the combustion chambers smaller which raises the compression.

The wastegate idea has been attempted. And most of what I've seen it has been showed to not be as great as everyone hoped. It puts a lot more stress on the head unit when it has to make up the boost after the wastegate has bled it off.

 

[02blownGT]

Who's been milling your heads? To be done properly they should be done on a milling machine. If the shop is doing it correctly then it's as exact as anything else. Removing a certain amount of material makes the combustion chambers smaller which raises the compression.

The wastegate idea has been attempted. And most of what I've seen it has been showed to not be as great as everyone hoped. It puts a lot more stress on the head unit when it has to make up the boost after the wastegate has bled it off.

My mistake on the milling machine,its still more of a cheap fix in my opinion.As far as the wastegate goes i dont see how it stresses the head unit anymore than normal its not like a turbo, a centri spins at the same speed if you vent the boost or not.Waste gates on centris serve one purpose to get boost earlier in the rpm range.

 

[01yellercobra]

My mistake on the milling machine,its still more of a cheap fix in my opinion.As far as the wastegate goes i dont see how it stresses the head unit anymore than normal its not like a turbo, a centri spins at the same speed if you vent the boost or not.Waste gates on centris serve one purpose to get boost earlier in the rpm range.

There was a write up in MM&FF one time. And I think someone did one on here as well. They talked about the stress and I think it caused a little more heat in the air charge as well. The biggest thing I remember taking away from it is that it wasn't worth it to me.