450 hp limit

[Magnastang]

I have read about 450 HP. being the safe limit for the 4.6-3V. Is that figure the crank HP. or RWHP?

 

[Larry_H]

Ok...here we go again....the "safe" limit is what the factory designed the motor to have...otherwise, they would not deny your warranty claims when you modify your engine....now....the factory will build in a safety zone in the design specs of the motor, more to hedge their bets on warranty work than to give you peace of mind when you tinker with their work. Generally, the accepted "margin" is 50%...so, if you maintain stock compression, stay within the RPM limits of the valve springs ability to rebound, you can push the motor to approx. 450 HP at the crank....anything more than that or any alterations other than mentioned above...if it holds together...its a gift and you should treat it as such.....some people have been given gifts of 600-700 Hp...others get their wallet hammered at 425Hp....any answer you get from anyone, including me, on this question...the answer will be about as etched-in-stone as the wind....if you are going to attempt to increase the power output of the 4.6 modular motor..start from a bare block and go from there....build it right, build it once, build it to last....

 

[SoundGuyDave]

....if you are going to attempt to increase the power output of the 4.6 modular motor..start from a bare block and go from there....build it right, build it once, build it to last....

AMEN, brother!

 

[silverbull1tt]

Of course it also depends on how your drive the car. If you beat the snot out of it day in and day out, it can let go in the stock configuration with just a CAI & tune. There is no guarantee that just because you build the bottom end that you are 100% safe.

 

[donnyonee]

and as a lot of us have here, im running 481 rwhp. with adams tune and 10 lbs of boost. stock internals, 5000 miles and not 1 problem. its the tune and your driving habbits that determine when those rods will come out for air.

 

[MrClean]

Subscribing...

 

[silverbull1tt]

its the tune and your driving habbits that determine when those rods will come out for air.

I couldn't agree more! +1,000,000

 

[Larry_H]

its the tune and your driving habbits that determine when those rods will come out for air.

I'll agree to that for the most part...but no matter how good your tune is or what your habits are, other things can and do go wrong....Don-W for example....collasped Cat....or not knowing you have a tank of bad gas and you're headed for the strip, sensor failures, etc....the tune is ultra-important, but thinking that your super-duper, whiz-bang tune is going to make your stock lower end last as long as a non-FI stock lower end after you put the boost to it is just fantasy...one of these days...sooner or later....

 

[Booger]

Well said Larry_H.

 

[thump_rrr]

Today is the 1 year aniversary of my Saleen S/C install. The car has been running a canned JDM Engineering tune on the stock bottom end.

The A/F was verified by Jim Sr about a month ago and no changes have been made.

The car is putting down 500rwhp/475rwtq on a 3.2" pulley and 93 octane gas. The car has never seen a drop of race fuel.

My car sees plenty of track time with over 750 N/A and 250 S/C passes.

You can call it luck but with JDM having over 600 examples on the road without a single failure to date says it's more than that.

I know that sooner or later all this pounding on the car will take its toll on the engine which is why I have an engine block sitting in my garage.

 

[Slofoot]

All of the above. There are no guarantees. IMHO if you go with a proven setup, don't cut corners on fuel delivery and tuning, run good gas, and don't try to see if it'll run 170 mph you can make it live. Once again no guarantees

 

[Hawgman]

I can pretty much echo what Peter said. Been running 500hp for quite a while on pump gas and a custom tune from a local shop. Beat on it like it owes me money. So far not an issue.

 

[ChevyKiller]

You got me Doc with that sig! Thought for sure a bug was on my screen! Stole it for another site...


I have said before and I stand by it and that is the magic '450 rwhp' is a guestimate that is not actually based on HP IMO. What I mean specifically is that I think the limits of the rods are related to BOOST and not HP. I think the '450' number is used as a basis for what the 'average' FI kit makes at what is considered safe psi levels. With good tuning, those psi levels can produce up to 520 rwhp and that's why some make 500+ with no issues.

The question 'what is the safe hp limit' is really not a good question IMO. The question should be - "How much boost can I run safely with a good tune?"

Whatever you get HP wise from that is what you get but I believe that is the question that is more important to the life of your rods.

 

[don_w]

The question 'what is the safe hp limit' is really not a good question IMO. The question should be - "How much boost can I run safely with a good tune?"

For the most part I agree... I've never subscribed to the "safe hp level" theory, and also think that boost levels (and thus cylinder pressures) are primarily what stresses the rods.

But even then, there are different kinds of "boost". For example, 10psi on a centri will generally make more peak hp than 10psi on a twin screw. But the twin screw will provide more boost at lower rpms, as well as make more torque down there. And from what I've read, many engines that let go usually don't do it at the "peak hp" rpm (say 6500). A lot of them let go well below that (mine included). And a turbo will give you both the torque and the peak power, but by not being crank driven, it may be easier on the bottom end, too. This isn't to say that one system is better than the others... it's still all about personal preference. All I'm saying is the 10psi does not necessarily equal 10psi (if you know what I mean).

And I agree with Larry... "other things can and do go wrong" that the best tuner in the world couldn't predict or prevent. Shit happens. Like I've said before: If you want to play, be prepared to pay. There are no guarantees.