A460 Tunnel Ram R&D

For a few years now I've been working on the design of a "Better" A460 Tunnel Ram for the 6,800 - 7,500 rpm range.

In 2021 I had a set of spacer inserts made for my new style TR to get the intake pulse more inline with my RPM range:

Baseline:


with spacer inserts:



Dyno results -  Spacer is blue line: ( engine was down 28 hp from baseline-if fresh it would have made 1,000 at 7k)


I wanted to try another approach with a longer runner manifold and decided to do some tweaks to a "Holmes" manifold I purchased from Lem some 12 years ago or so:

The manifold went from:





I wanted to shorten the original runner and the best way  I could figure out to do it (other than cutting off the plenum and chopping the runners and then welding plenum back on, was to build up the outside bottom of the plenum and then cut through the original floor and cut the runners down from the inside, and at the same time increase the plenum area.  Here are a few pictures off the process, over the past couple of weekends:



Got to cutting:


Where the quarters are sitting there's another .185" to cut:



The floor was finished up this evening and will start working a bit more on the runners this coming weekend:

Are you going to do a A to B Test also on the Intakes?

The runners on the Holmes look like they are around 3/8" bigger (rectangle now instead of square) in the plenum then the other one.

Looks like you are pretty close to a Cast "Sheet Metal" at this point

supervel45 wrote:Are you going to do a A to B Test also on the Intakes?

The runners on the Holmes look like they are around 3/8" bigger (rectangle now instead of square) in the plenum then the other one.

Looks like you are pretty close to a Cast "Sheet Metal" at this point

The runners are getting opened up. The stock "Holmes" runner is about 5.13" sq in. 2.7 x 1.9 approx.
These are getting opened up to around 5.75" sq in or a tad bit more:

The target runner length on this was determined by a combination of a couple different math formulas and the chart that Paul Swartz has posted on his web site. Paul is a sharp guy and made my spacer inserts for me posted above:
http://www.swartzracingmanifolds.com/tech/index.htm



Target RPM is 7,300. I'm on the "long" end of his scale for now, but I might lower the runner just a tad.

Why 7300 rpm?

BOSS 429 wrote:Why 7300 rpm?

Jet boat engine. It's operating range is 4000-7,200.

I figure with a target of 7,300 it would make for a good Bracket Racer intake.