Thanks for the added info hapisok
It's certainly reinforces the primary nature of how this family of products work from more of a practical level rather then just a theoretical one.
To recap what I've written earlier in this thread
http://camaro5.com/forums/showpost.p...&postcount=362
Quote:
Originally Posted by MACE_ENG
As noted, the main reason the spacers work is not so much that they keep they manifold cool (which they certainly do) but is the fact that change the savaging properties of the manifold. In that the manifold is working more efficiently base on the engine's operating limits. This is based on Helmholtz resonance principle.
To put things into perspective, they could be made out of aluminum and still reel off similar figures on a dyno. Sure repeatability and power consistence on the other hand would fall but that is a different characteristic which is certainly influenced by material properties (thermal conductivity) of the spacer.insulator.
As for what size spacer? We have 3 sizes to give people options (6,12 and 25mm), primarily based on fitment consideration for various firewall, bonnet, intake constraints.
Thickness of a spacer/insulator with regards to runner length, is usually directly proportional to the gains down low, which is inversely proportional to the top end. Generally the latter isn't an issue at all, unless you plan on increasing the factory rev limit or consistently spending your time upper RPM band for competition work or fixated about peak power figures.
If your car is a daily driver, predominately spending most of your time in the lower to mid rev range then you would probably want to consider running the largest spacer/insulator you can.
Understandably we can be seen as being biased (however we do sell three different sizes), but the physics indicates that "optimal" lower RPM manifold scavenging is achieved with longer runner, while the inverse is true with short runners. Both with the same diameter runners of course
Hope this helps
Steve
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It's the above reason that everyone who's purchased the 25mm item for their street duties have been quite happy and surprised with the real world performance of the product. If people religiously hang around the 5-7k power band mark then better value could be had with going a shorter item.
In saying that though I'm sure our plenum spacer which we'll be posting out to some people soon will improve top end performance (even with the 25mm item) by primarily improving air distribution and not just cooling