Reading another thread and this popped into my head. Take my dyno graph:



What are causes my motor to stop making power at around 5k RPMS, and slowly die off? The idea with the cams is to make power well into the 6k + rpm range correct?

So am I hitting some kind of "limit" with my current setup? Or is that simply the power curve of the engine, and there isn't much you can do about it? I am just curious. Thanks for your help in advanced.

 

The intake manifold is the limiting factor here. Everything looks normal based on your setup.

 

Thank you MRT...i couldn't think of what the answer was. I was sitting here for like 10 mins tryin to figure it out lol.

 

Well cams are supposed to make the car pull higher into the rpm band. I mean stock cars stop making power right around 5200rpm's so idk if its the cams he's running or what, but when i usually see a cammed gt's dyno sheet, the power usually is moved up in the powerband some...at least a couple hundred rpm's if im not mistaken. so i dont know why your car only peaks at like 5200-5300.

 

Those Comp's did shift the powerband a couple hundred rpm higher. No matter what cams you run, the stock intake will be a limiting factor, epecially after 6k.

Given his setup, everything looks totally correct to me. They peak a couple hundred rpm higher, start pulling hard at 4.5k, 30 hp gain at the peak, and have slight losses down low.

 

so you think my stock intake manifold is the limiting factor? can you go into more detail? Is it due to lack of air or anything? I'm trying to "visualize" the bottle-neck haha. No real reason, I just want to visualize it in my head.

 

mrstang, are you really pushing 269/305 w/ just a throttle body?

I cant belive that adding a set of cams will only add 15 wrhp and 5 wrtq. What am I missing on your setup? A throttle body / plenum cant possible help that much? (Im just simply
saying that we have pretty much the same setups (minus the throttle body, and I have cams) but we are for the most park makign the same numbers. what gives?

 

hes got longtubes and other mods?

 

I know, thats what im saying.


We have the same mods EXCEPT I have cams and he has a Throttle body. Yet, we are making almost the same numbers.

Im just saying that in comparison, my numbers look low.

 

With adding cams you added more power. To make more power you need more fuel and air. So when you are at a higher rpm your car is demanding more fuel and air. On the fuel side of it you are ok but you aren't getting enough air into your engine to make hp at a higher rpm.

We had a recent thread talking about the Edelbrock Victor Jr intake manifold. A guy over at Corral had ported heads, cams and bolt ons. With the Edelbrock he made over 50rwhp more at 6000rpm than he did with the stock manifold. Which allowed him to keep making power longer.

Think of it like you are running your fastest but you are breathing through a straw. You wouldn't be able to run your fastest for to long and would eventually start to slow down. Now take the straw out and run your fastest. You will be able to go your fastest for longer. That isn't the greatest example but you should get the point of what your intake manifold is doing to your car.

Also when you add your s/c, your intake manifold is going to continue to restrict air at higher rpms. Sxynerd had one in his setup and loved it.