Does the bottom end care how power is created?

[Josh Kinzey]

The bottom end (ie crank, rods, pistons, pins, block) see the gross HP from the engine, not the net HP as measured at the crank flange.

The gross HP minus friction losses, pumping losses etc will result in the final net HP that is left to accelerate a car or make HP on a dyno. When you increase the turbo or blower load by putting a more restrictive head on the engine, you increase the losses and you have to make more gross HP to make the same net HP. The engine components "feel" that gross HP load.

Rick

Is there anyway to know the difference in gross HP between the 2 set-ups? If the difference is less than 50 HP, I think Joe Customer may be better off with the cheaper head. Another 50 HP is not going to make any appreciable difference in the failure of his particular rotating assembly. If the difference is closer to something like 200 HP, then he definitely needs to consider the better heads.

[Rick360]

The bottom end (ie crank, rods, pistons, pins, block) see the gross HP from the engine, not the net HP as measured at the crank flange.

The gross HP minus friction losses, pumping losses etc will result in the final net HP that is left to accelerate a car or make HP on a dyno. When you increase the turbo or blower load by putting a more restrictive head on the engine, you increase the losses and you have to make more gross HP to make the same net HP. The engine components "feel" that gross HP load.

Rick

Is there anyway to know the difference in gross HP between the 2 set-ups? If the difference is less than 50 HP, I think Joe Customer may be better off with the cheaper head. Another 50 HP is not going to make any appreciable difference in the failure of his particular rotating assembly. If the difference is closer to something like 200 HP, then he definitely needs to consider the better heads.

I think it would take something like a combustion pressure sensor ($$$) on a dyno to tell very accurately. I'm not familiar with the heads/engine in question but my guess is the difference in pumping losses would be less than 50HP. I don't have any real experience in this so it's just a guess.

I wouldn't want to see anybody borrow money to buy parts for a race motor although that is their decison to make. All you can do is advise what you think best for the performance requirements he wants.

Rick

[Ron E]

With somewhere around 100 extra CFM intake and exhaust, with the TFS head, I think the potential is way way past 50.

[SchmidtMotorWorks]

Are you serious?! He is OUT of money. He considering a loan for a $1000 set of heads.

LOL Yah that's life, yesterday a guy wanted to order a manifold from me, he put his Grandmother (sounded about 100 years old) on the phone to give me the credit card info, about half way through I stopped the deal, it just seemed wrong.

[n2xlr8n]

One thing to think about is that the engine that runs the higher boost to get to its power goal will likely be closer to its detonation limit.

Even if the intercooler out temps are the same, conditions in the cylinder will not. Higher exhaust gas back pressure will reduce how effeciently the engine gets spent combustion gases out of the chamber, and the air will be doing more work getting into the cylinder, so its temp will be higher in the combustion chamber. Higher oil temps mean hotter piston crowns etc etc.

I'd say go for the setup that makes the most power on the lowest boost pressure. It will be doing the least work making the power and will have more reserve left before you get into other problems like cooling, and detonation.

Larry

Right. On my budget, I'd gladly spend $1000 to ensure my engine combination is making the number with the least amount of stress.

IMO, spending $15k on Engine management, a short block, two turbos, and an intercooler, and sweating $1k for the right heads is just penny-wise and pound foolish.

S.

[talon]

does it have to be Trick Flow? what about the RHS cast iron heads? This should save him at least $200 bucks - and I think the exhaust low lift flow for blow down is better than Trick Flow. Those RHS heads are pretty good

[Josh Kinzey]

I'll ask him about the other/cheaper heads. I appreciate all the input guys, thanks again.

It appears that the aftermarket head is not necessary, but a really good idea. I'd be really interest to find out what the peak cylinder pressure is between the 2 options, when both are producing 600 RWHP. Anyone got an idea on how to figure that out?

[Torquemonster]

sometimes budget has to rule - but nobody ever regreted buying quality.

Building the best engine base you can afford is simply good sense as is keeping temps and detonation thresholds down. I'd spring the extra $1k just on principle.