>Hey Jim, do you think the performance would go down with the
>p&p manifold?

Absolutely not. Performance will go up - times will go down. I don't know what they were smoking when they made the molds for these manifold castings and the template for the upper to lower gasket, but it must have been good. Alot of material needs to be removed to properly port match the manifold sections. The upper to lower gasket actually hangs out into the stream - it needed to be cut back. Also, the port outlets to the head have a severe angle on the bottom of the port.

Here's some shots of the upper manifold. It was the worst off as far as port sizing. ALOT had to be removed to port match it.

This one compares an initially ported runner(left) to one that hasn't been touched(rigt). If you look really close at the one that hasn't been touched(left) you can see the score marks that I made from the gasket.


Here's a closeup that shows how much actually needed to be cut.


Here's a closeup of a finished runner


The finished upper section


Here's some pics of the lower section. The upper ports did not need much taken from it, but I did have to cut the gasket so that it wasn't sticking out into the runner flow.

This one shows how I cut the gasket. It only needed to be cut on 2 sides for each port - by about 1/16th of an inch.


The finished upper section of the lower manifold.


The ports to the head needed quite a bit of material removed to port match. Here's a side-by-side of an initially ported(right) and completely unported(left) runner.


This shot gives a good picture of how much actually needed to be removed to port match the head ports. It also gives a descent picture of how sharp the angle is on the bottom of these port outlets(somewhere around 40 degrees). I was able to greatly reduce this angle(to somewhere closer to 15 degrees), but it required a tremendous amount of porting.


So, most importantly, with a p&p all of the ports/gaskets are matched. I was able to smooth the surfaces of pretty much the entire bend, all the way from the plenum to the flat section in the lower manifold, which is good. Also, that severe angle at the head port outlet was a killer - I just HAD to make it more gradual. I should definately see gains with this.

Now if the original question was "Would performance go down if i port match the manifold to the TB?" - I'll find out soon enough. Before this thread started my thought was that I would see a gain, but now I'm not sure if I'll see a gain or not. I still do not think I'll see a loss.

My plan: What I'd like to do first is run the p&p manifold without port matching the Jeep TB and see what that gains it makes for me. I will definatly see a gain with that. Then, hopefully before I get the turbo on, port match the upper section to the Jeeper and see what that does for me performance-wise. By staging the mods like that, I'll be able to see what they give me individually.

>I'm trying to picture the airflow based on the
>times you've given. It seems like the difference between the
>two is nominal, as in, getting the bigger tb hasn't destroyed
>performance, but it hasn't really helped either.
>
>I'm thinkin since the manifold is still restrictive, the tb
>isn't really doing much to affect performance.
>

What do you mean it hasn't helped. It gives me somewhere around .2 seconds off of my 1/4 mile times - on an already fast(relatively speaking) car. If you look at the second post that I made with times, you'll see that I noticed the same .2 second drop on the 1/8 mile as well. I don't know but that seems more than nominal to me.

>On a side thought, would the diameter of the piping on an
>intake affect this airflow too? Injen's intake starts at 3"
>and then bottlenecks to 2.5 right before it connects to the
>tb. I think AEM's is 2.5" and stays that way all the way
>through.

Yes the diameter affects the airflow. I've always though that what really matters is to make sure that the intake piping(if you have any) is bigger than the TB. So maybe someone else can chime in as to which size is better.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html