Don Terrill’s Speed-Talk

Where do the numbers come from in that formula? 19100 empirical constant for a four-cylinder engine, copied by me from the advanced tech post 116.5 empirical constant, copied by me from the advanced tech post 15.9 is the runner cross-sectional area in cm^2 1850 is the plenum volume in cm^3 30 or 40...

A much simpler formula from the advance engine tech section gives this for the resonant rpm. It's pretty damn close as the observed peak with two 30cm runners and two 40cm runners is 3150. 30cm total runner length: 19 100 * sqrt((116.5 * 15.9) / (1850 * 30)) = 3489 rpm 40cm total runner length: 1910...

So are these guys for real or not or what:

https://www.facebook.com/ExtremeTuners

Morgo wrote:http://forums.bimmerforums.com/forum/sh ... ?t=1575817

ptuomov, can you provide the info below in the attached pic? If so I will double check your results using my own spreadsheets. Here's a shot of my spreadsheet: SSHH.jpg It solves for the resonant frequency which I think is proportional to the peak torque rpm. Don't have an opinion about the peak po...

So I am looking at this intake and it has four 40cm total intake tract lengths and four 30cm lengths. The center/inside cylinders have the long runners and the end/outside cylinders have the short runners. Now, isn't this manifold a prime candidate for dual pattern intake cams? That is, move the IVC...

I wrote a little spreadsheet to figure out how changes to that stock s4 intake manifold would change the rpm point of the Helmholtz resonance effect. It's with two cavities (cylinder and plenum) and two pipes (primary runner and plenum inlet). The formulas are from the "Theory of Engine Manifol...

If you are going to keep this thing ostensibly smog legal, you'll be spending a lot of time with that intake manifold. IN CA it is best to buy something you will be happy with stock. What model in that case? In my opinion, 1989-1991 GT is the best value stock. It's fun stock with 5-speed transmissi...

Here are some notes on the intake manifold from one person who has worked with the S4 stock intake manifold and who's judgment I trust: http://forums.rennlist.com/rennforums/5558133-post38.html As another data point, while flow testing the heads to my 6.1 liter engine project, we flow tested the S4/...

For someone considering buying a 928 for a performance car in So Cal, at 1st glance of the specs, it looks like the later 5.4 models would be the place to start, is that right? The '87 and '88 five speed S4's are I think the most fun per dollar. If you are thinking about forced induction, the '87 a...

In case anyone is interested, here's an old article about the Porsche 928 intake and some product ideas by a now-defunct company: https://picasaweb.google.com/105951008271571928631/928Developments?authuser=0&feat=directlink The most relevant page in terms of the intake flow (or lack of it): Head...

The idea is to increase the plenum volume with spacers and move the "flappy closed" resonance point further down the rpm range. This will hopefully help the engine at the point where turbos can fill up any hole. I am curious how increasing the plenum volume, will help lower the resonance ...

First, I know you are in a position to be able to have this done. It would be a tragedy of some sort if you spent a lot of time (and money) making or having something made that "almost" fits. Second, you are proposing to install what is essentially a cyclically cycled bomb casing on your ...

I am constrained, of course. When I was younger, I had all the time and none of the money to complete projects like this. Now I have all the money but none of the time... So much of this is just speculating and dreaming. Start with scans and at least be precise with your projects. Contact Faro and ...

Flap open seems quite good to me, I would choose to avoid the complexity and go with that unless you really enjoy the optimization and can tell the difference. With the normally aspirated stock car, the difference is noticeable. To the point that people who play with these cars can test drive one a...

Sounds like a plan. Now you just need to make a plenum that works. Check on Trans Ams thread in advanced (Strongest Harmonic Pulse) in regards to the plenum. I read that thread and found it very interesting. I haven't actually yet converged on any sort of plan, and I have a lot of project ideas reg...