No, my info is correct, you just didn't read it. First, I said the 996 GT3, not the new 997 GT3. The cam specs on the 996 are closer to what he is using, the 997 cam specs are more aggressive. Second, I said the engine didn't use VVL (variable valve lift), and it doesn't. It uses variable timing on the intake only, just like the VQ, and has a total of 52 degrees of cam phase- which is what I posted. Learning the cam phasing on the 996 GT3 would be worthwhile as a starting base considering the similiarities between cam specs and available phasing with the Nismo CVTC units. Finally, the 996 didn't use 12:1 compression, the 997 does.

You mean like stating that a 12:1 CR is a part of the GT3's ability to make power? As obvious as it is that making NA power is hard, it was a prop to rednezz.
I have not ever tuned a FI car, I let JWT do that for me with my SR. Our school's Formula SAE Yamaha R6 is tuned by us, currently using a Haltech in partnership with the graduate program for Motorsport Engineering.


I think enough people have covered the fallacy of this statement. Seriously, backpressure is never a good thing for power.
Will

 

Simply that an OEM has the luxury to tune an engine to the ragged edge with ignition and cam timing. If they blow one or two up in the process, and they usually do, then they have the resources to cover it. Most of us do not.
A perfect tune, to me, means to have tuned the engine as much as possible within the degree of longevity desired. I cite the GT3 as a good example, but Honda's F20C and F430 are also good examples. 112 to 120 hp per liter is difficult to accomplish NA, especially with an eye towards longevity, emmissions, and noise. Most of the tuners to hit this level will compromise at least two of the last three objectives, and still not make as high a specific output. But as I said, who can afford to really find the limits if it means a new engine to do so?
Will

 

The last part really summed it up. The scavenging effect is what is key. Varying the exhaust diameter, material, and length will all have an effect to either raise or lower the rpm at which the best scavenging occurs. This is also to say that it will change the point of peak Ev and where the engine makes it's peak torque. I think most don't understand that the exhaust charge coming out of the combustion chamber has mass, and it's this mass that creates the scavenging effect. This mass can be tuned to the natural resonance of the exhaust system to increase velocity at a given rpm, and therefore increase the scavenging effect on the combustion chamber. Of course, not all rpm can be tuned to the same resonance frequency unless we had an infinately variable exhaust. Since we don't, exhaust backpressure rises the farther away the rpm is from this frequency. A large exhaust typically promotes higher rpm resonance and a smaller one promotes lower rpm resonance. Remove the exhaust all together, or run too large a diameter, and there is no resonance and a complete loss of velocity and scavenging, and a natural loss in power is the result.
I wonder, have you looked at the book, "Scientific Design of Intake and Exhaust Systems" by Phillip Smith? I think you would really like it and find a lot of the material pretty fascinating, if you don't already have it. There are lots of practical mathematical formulas worth playing around with, and a very comprehensive section on manifold design. As Z1 said, the headers are where the bulk of the power is to be made on an engine from an exhaust standpoint. Running the right diameter, length, and with the properly spaced stepped primaries for a given rpm and discplacement, will net the largest gain to be had. This book goes into good detail as to whay and how that happens.
Will

 

A 312 duration cam would be great? How can you know? It would be anything short of "great", even with the ability to map VTC. It would leave you with a very peaky motor.

You cannot change the laws of physics, even with the ability of controlling cam timing. There is a point of diminishing return, where upping the duration and/or lift has no physical change in the peak power, or power band of the specific engine. Not to mention, there are all of 0 cams made that actually have this lift, so you are then looking at buying expensive blanks, and having them cut to suit this radical profile. How many people are out there that are going to drop $2500 + on a set of cams, and out of those, how many have the rest of the setup that would even make such a cam truly beneficial?

When it comes to cams, there is alot more to it than merely lift and duration. Those are good starting points, but to a large degree they are marketing terms, and do not come close to giving you the true "answer" as to the best cam for a given application.

 

Thanks Will!

I hate reading regular story books but when it comes to deep technical reading (about subjects I like), I can't put it down.

I'll see if I can pick up a copy on Amazon.
Tony

 

Awesome thread, please keep us posted! I've been waiting for someone to do a full N/A build, highly anticipating the results!

 

Thanks for sharing can't wait to see your gains.

 

Went by the shop again this afternoon to see the status of my motor. They got the motor assembled and piston to valve clearances checked good. My builder just need to install the oil pan, manifolds, and accessories and then back in goes the motor. I was hoping to try to start the motor tomorrow but my builder said he fell behind and its looking like early next week. Here are some pics from today.

 

What RPM limit will you set for it?

 

congrats i envy u brotha

 

It depends if I can continue to make power past 6600 rpm with my current intake manifold. If these cams make power to 7700 rpm I will run it to about 8000 rpm. If I can't make power past 6600 rpm I will set it for 6900 rpm. I am looking for reliability since I will be tracking the car in NASA and PCA events.

 

Are u doing any work to the bottom end? What rods are u using? Also any boring of the block? Stock crank or what?

 

subscribing for dyno results

 

I did not have the motor processed, balanced and blueprinted. I didn't process the block because local shops don't really have a reliable record. Using eagle rods, standard 95.5 wiseco pistons (11 cr but ended up with actual cr of 10.7) and stock crank. I actually should have waited for another month and I would have just purchased the Cosworth shortblock. Oh well.

 

So how is the build up coming?

 

It's not an n/a build unless it has some itb's. Unsubscribing...










j/k

 

So Hydrazine, am i right to assume you will be designing and building an exhaust for the Vq?

 

Yes.

 

Looking forward to it, any eta, or setup? i.e. single, td, xpipe, etc..

 

Awesome build. I would highly recommend the cosworth main and rod bearings considering this car is going to be road raced.