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since you're going nuts with it have you investigated barrel throttles, or shaftless throttle blades?
Haven’t for this throttle body. Åke and Greg Gray (strosek ultra and slate blue) are looking at those saftless ITB systems for their motors. For this throttle body, one might squeeze a bit of efficiency out with a thinner plate from a different material. But we’re sticking with thick aluminum because it’s easier to get all operating modes to work with the ports etc.
Dealing with the loud shock waves from the early exhaust valve open
The S4 cams have short duration and are installed retarded. The Elgin 65-6 cams in the blue engine have longer duration and are (currently) installed straight up. Consequently, the exhaust valve opens meaningfully earlier in the blue engine than in the stock S4. Combine this with the lower compression of the blue engine and higher cylinder pressures caused by the turbo, and we’ll have a situation in which the exhaust valve opening becomes quite loud. We are penciling in pressure ratios that are consistent with supersonic blast waves coming out of the exhaust port.
Cats are effective at quieting down such waves. However, when running “test pipes” with less restriction, the dual 3.5” exhaust might be louder than desired.
We are going to at least testing and probably using these cheap bullet mufflers as the “test pipes” in place of the cats. They have 3.5 inlet and outlet, 9” overall length, and 4.125” outside diameter. They are about the same size as the cats, in other words, but without the restriction of the honeycomb. The purpose of them would be to quiet down the supersonic “blast waves” that we hypothesize are produced by the relatively early EVO of these cams. Made by Vibrant Performance from 304 stainless alloy and they are quite cheap on amazon.com. $117 shipped for the pair, so we’re going to at least look at them.
...the firm selling thru Amazon can’t find employees who can send out correct parts. Not a race muffler, not the right inlet diameter, not the right outside diameter, not the right length, not the right part number. Other than that, all good.
I'm running Vibrant resonators on my custom exhaust and it doesn't make a sound under cruising. They're quite effective.
Good looking exhaust. Not too loud?
I had just Borla cans and no cross-over in my dual 3" exhaust and it was very loud with the bigger cams. This new exhaust that John's making me is going to be bigger but will have a lot more muffling and a couple of cross-overs.
I had just Borla cans and no cross-over in my dual 3" exhaust and it was very loud with the bigger cams. This new exhaust that John's making me is going to be bigger but will have a lot more muffling and a couple of cross-overs.
Cruising, maintaining stoichiometric, the car doesn't make a sound. Roll on the throttle and you get a nice growl. Stand on it and it sounds violent.
Here’s the first attempt at the rear muffler shell/skin. Unfortunately, the metal shop made the shell too short and out of too thin plate. See the earlier comment about four percent unemployment. I’m posting this here just to show you approximate appearance of the rear muffler.
On other news, the basketball season has started again. Things aren’t exactly going our way as far as the Celtics are concerned. The only two bright spots are how well Jayson Tatum is playing for a rookie and that one of our former nannies made the Celtics dancer squad:
This design works in some features from an expansion chamber, absorption silencer, and cross-over combining slightly phase-shifted pulses. Proof of the pudding will be in eating, as always.
John finished the rear muffler. Solar Flux in the welds because it was welded with the packing already inside. The muffler is ready. It’s consistent in terms of style with the Borlas.
10-15-2017, 05:27 PM
