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My experience with a MINI S and a de-catted down pipe leads me to believe that a good deal of power can be gained with the FiST. Of course this typically leads to a crappier sounding exhaust, but it may have been my particular brand of pipe.

I also believe that most folks are likely to upgrade the cat back portion of the exhaust and call it a day. Anyway, which tuners are working on a catted or offload (cat less) down pipe?
 

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From what Cobb and a couple others have reported on this subject, a dp really won't do too much on this car. The biggest restrictrions are the intake and the FMIC. The restriction on the exhaust is the turbo outlet size. Much like what they've seen on the FoST.

I know I was excited at that thought as well b/c of how big of a change the dp made on my 135, but after reading around, i think i'll be going intake/fmic as well.
 

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M-Sport uses(d?) the stock plastic intake manifold on the WRC engines. That means should it should be good for 300bhp at minimum.

Unless you're just talking a CAI.. Which will obviously help, just cant see that alone adding big #s w/out replacing the stock intercooler because it is pretty mini.
 

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On many forced induction cars the inlet before the compressor is a restriction, like GT500s that find power with inlet elbows and dual 70mm throttle bodies but those are highly tuned cars with twice or more power than the sub 300hp that seems like a reasonable goal for a 1.6l engine.

I think the interior surface roughness, gentle curves and a continuous cross-sectional area are probably more important than diameter because there is roughly 14 psi of atmospheric pressure pushing the air to the turbo inlet. Its just not a very big restriction.

The intercooler shouldn't be a restriction either but a better one might drop the charge temperatures which means more density, better cylinder filling and more power.

Since intercooler design is fairly well understood, if I ever found an engine with a truly restrictive intercooler, I would first assume a packaging problem but if that wasn't it, I would conclude that the restriction was intentional to cover up something else like a durability issue.
 

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Back to the downpipe, can it do much if your turbo is already over-reving?

That seems like the only reason to have less boost at 6,000 rpm than at 3,000 rpm.

Its fairly normal for an engine to be more detonation resistant at high rpm than low rpm so I think the holy grail Fiesta ST engine will be one that spools almost like stock but makes 20+ psi boost all the way to the redline (or very close).

That's not going to happen with the stock turbo unless its got a lot of potential that no one has tapped in to yet.

Looking at the Pumaspeed web site it might take $1,500+ to try a downpipe and cat back, then add in money for a tune. If it only adds 10 HP, you might be disappointed with your ROI.

I think 10 HP might be optimistic too.
 

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Boost isn't what makes an engine blow up, detonation is what does that.

If there is no detonation at 3,000 rpm and 20 psi, I doubt its on the edge with 13 psi at 6,000.

Its much more likely that Ford is worried about losing a fin from the impeller and sending it in to the engine.
 

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Exactly. Especially with the electronically controlled timeing. Any detonation at high RPM'S is easily cured by backing off the ignition. That little turbo would likely grenade trying to push 20psi @ 6000rpms.

Im now hoping we can get to 240bhp with standard parts before having to do a turbo upgrade.
 

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Boost isn't what makes an engine blow up, detonation is what does that.
If there is no detonation at 3,000 rpm and 20 psi, I doubt its on the edge with 13 psi at 6,000.
Its much more likely that Ford is worried about losing a fin from the impeller and sending it in to the engine.
Are you aware that the ST engine still uses a cast iron crank, not forged? There's a limit to how much HP it will take before breaking.

As for the turbo blowing up, I find that doubtful. The fact that it's small helps this. And if it did, the pieces would have to travel through five feet (or more) of intake pipe, the intercooler, and uphill to the MAF before actually reaching the engine.

Your assertions about the engine being able to safely take 13 psi boost at redline are pure unsubstantiated speculation and should be acknowledged as such. :poop:
 

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Unsubstantiated?

How about claiming a cast iron crank can't handle 300 HP?

I'm sure the crank would have trouble with prolonged detonation but if I'm right and the engine can handle boost at high rpm without detonating, the crank is one of the last things I would worry about.

Most crank failures are actually caused by something else that's wrong, connecting rod failure, too little bearing clearance, main caps walking, block flex, and high loads on the snout (supercharged).

The way modern aluminum engine blocks are designed for NVH and the durability testing that is routinely done during development tell me that the connecting rods are the most likely point of failure because OEMs usually use small cheap bolts and sintered powdered metal cracked cap rods but computer simulation and design have come to a point where Ford can get the Coyote engine right on the first shot on a compressed schedule with more than twice the power, a higher rev limit, longer stroke, wider main journal spacing and 90° throws which all require a stronger design than a little short stroke flat crank engine with a 6,350 rpm red line.

Claiming that Ford would widely release an engine without enough design margin to handle a modest increase in power is silly.

Turbochargers on the other hand have a rev limit where compressor blades can shear off due to the forces. The only way to build boost is to force more air in to the engine and when you increase boost you have to increase the turbo rpm. When you get to the limit you have to do things like reduce boost to control the speed. Ford would do that because they were optimizing for low speed torque and fast spooling.

Looking at the Cobb tunes, it looks like that is exactly what they did.

Barring any evidence like a broken crank or someone that can get a stock turbo to build more boost at high rpm (it hasn't been done), I've got to draw a conclusion from what is out there.

My "unsubstantiated speculation" is actually a pretty educated guess along with being told that the turbo is too small by one of the guys from Cobb.

If it looks like a duck, swims like a duck and quacks like a duck, its probably not a kangaroo.
 

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My "unsubstantiated speculation" is actually a pretty educated guess along with being told that the turbo is too small by one of the guys from Cobb.
You've just nicely defined "unsubstantiated speculation"...
 

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OK you better tell Cobb to stop tuning the 1.6 or they are going to wind up with a pile of broken crank shafts.
 

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Hey, you & they can do whatever you please. I have no objection to anyone's efforts to get more power out of an engine. I've done it many times myself. I was only trying to point out that opinions were being presented as facts, which is a disservice to the less experienced participants on this forum.
 

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Crank aint the problem.. lol We've been tuning Gen1 QR25s to +300whp at 10psi and 7K. Its a horrific 1.47/1 rod to stroke ratio. FiST is way better. You wont see 250whp with bolt ons tho
 

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Unsubstantiated?

How about claiming a cast iron crank can't handle 300 HP?

I'm sure the crank would have trouble with prolonged detonation but if I'm right and the engine can handle boost at high rpm without detonating, the crank is one of the last things I would worry about...

...
Looking at the Cobb tunes, it looks like that is exactly what they did.

Barring any evidence like a broken crank or someone that can get a stock turbo to build more boost at high rpm (it hasn't been done), I've got to draw a conclusion from what is out there.

If it looks like a duck, swims like a duck and quacks like a duck, its probably not a kangaroo.

+1
 
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