Nope you are correct. And even back then (1998) Kenne Bell told my that the extra octane booster would be OKAY. NOT!!!! I am a firm believer that the tune make all the difference. But I still would not take the chance without going with a forged bottom end today regardless of the tune. Like I said...thrash your car like Don does and get back to me.

 

I thrash my car every time I drive it..... you know that Scott. But give me the weather that Don has out there, and you and I both would thrash it at the strip more often LOL!

 

I know! I know! I had to solve this problem for one of my ME courses many years ago...

There are two main failure modes for the rods: They fail in tension as the piston goes "over the top" and it wants to KEEP going up, but the crank and rod is trying to pull it down (not on power stroke of course). This usually is going to occur at max RPM (remember those rpm SQUARED loads!) and when you let off the gas (no more combustion loads pushing down on the piston), things get pulled a LITTLE too tightly.

They also fail in compression during the meat of the power stroke. That failure mode usually happens closer to peak torque than RPM. Given that the rods are usually quite a bit stronger in tension than compression (ANY beam is), this is the normal failure mode.

As for why people talk about a "safe" HP limit, well, probably because a whole of people think more in terms of "HP" than "torque". When's the last time you heard someone bragging about the peak torque of their car? Unless they are driving a diesel pickup, it's probably been a while. Plus, given that torque = HP * rpm / 5252 AND the fact that most gasoline internal combustion engines have the same general torque curve, talking about peak hp actually DOES relate back to what the torque is doing in that same engine.

 

I agree. Add to that a common scenario of detonation occuring while under load at low rpms and mashing the loud pedal, and you have a recipe for metal soup in your oil pan.

 

LOL... so agreeing with me is a sure way to be unpopular, huh?

 

Well being one of the "blow ups" out there would make me and my opinion unpopular. When it comes to talking about what these motors can and cannot take I err on the side of safety... meaning a strong bottom end. We have shared the cost of building a new motor which makes us more unique in our opinions I guess. But learning from lifes hard knocks is a great teacher. And I know we have both been beat up a few times!!

 

Plus, when are you most likely to have detonation? Normally below and/or around peak torque. Probably because peak torque is when you also have peak cylinder pressures...

That does add up to an ugly recipe, doesn't it? I guess that is why I haven't put the turbos on mine yet. I can't afford the fully build long block and I KNOW I wouldn't be able to resist playing with higher boost "just for a test" a "few" times!

But someday...

 

I noticed Roush is selling fully forged short blocks with their supercharger kit that delivers over 500 HP.
You may be able to buy just the 4.6L short block from them.
http://store.roushperformance.com/detail.aspx?ID=1148

 

Like this?






And like this too?




I'm with Don 100000%.

 

Those look vaguely familiar...

 

^ Misery loves company!

 

100+ shot of nitrous maybe 25 (?) bottles through it. Sometimes I would forget to change tunes . Launches at 5K+ rpms clutch drops with a centerforce DFX and drag radials. No problems.



Oh yeah....then I went turbo.



10 psi over 500rwhp, all day. Lots of 150+ mph, 5 gear pulls. Many, many 60-140 races on the highway. Then I decided to up the boost, without getting retuned, to 13 psi on race gas. All the same stuff, still no problems. Here's what my stock pistons looked like when cleaned up:




They were perfect, the whole motor was perfect. I have a pretty good feeling not very many people have been as hard on their motor as I have.

 

This might be a stupid question but here goes. If you are still running a stock short block with all of that turbo power than why are you showing us your pistons???????/

 

Bragging????

Actually, I suspect he decided he REALLY wanted to try 16psi and finally forced himself to upgrade the rotating components. But that is VERY much a guess!

 

rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination.

450 rwhp is a Good reliability Rule of Thumb for the 05-09 4.6L 3v with a Stock rotating Assembly.

KC

 

There's no chance for this motor at the power levels that I want. Plus I wanted a stroker.

And RRRoamer, 16psi is a joke.

 

Bullitt995,

Just for the record, you SUCK!!!! I've been wanting to put a turbo on my Mustang before I ORDERED the silly thing back in January 2005. I STILL don't have that done!

Oh well! If the new business works out, I'll probably be heading down that road a whole lot faster than I would have staying as an IT guy for Intel. If it doesn't, well, I'll be one of those bums down on the beach in Florida in a few years! At least I'll have a good tan!

An yes, the stroker + turbos approach is how I want to go as well. That combo just makes me drool thinking about it. Better quit before I short out my keyboard...