Did anyone see the series of EMPI deals with the same motor on the same dyno just with different exhausts? The dyno numbers where hugely different. 90 to 120 offhand. Is this possible or just trying to make a buck?

Kevin

They probably had a high performance motor that they choked out with a stock exhaust. Then installed a better exhaust system to let it breathe.

OK, I'm intrigued now - got a link?


.

Correct, it's the only way you can see a jump like that.
Typically your performance increases are well under 10%.
If someone sets a test up like that, it's a pretty sure bet the actual gain is unimpressive.
I personally saw about 4 % on the dyno on ours. In all fairness, 2 diferent dinosaur, diferent atmospheric conditions. The main reason we don't push the performance side of it.

Out of Stock, but is this the muffler in question:

https://www.dubparts.com/cdn/shop/products/...pg?v=1562218354

Yes it's the mondo muffler

I'm not even sure you'd see that much improvement using a Tangerine full-on racing header on a stock 914 motor. And his stuff is the best.

Color me very skeptical of those claims.

--DD

DD
I was actually hoping someone from EMPI would reply.

Kevin

hypothetically...

that design with 4 into 1
would be less efficient than the bursch design of 4 into 2 into 1

If you "@" them they will be more likely to see the post.

Zach

Is the Bursch still regarded as the most efficient production muffler ?

The exhaust in the link muffler exit pipe is on the wrong side. I would want to see the exhaust on a set of heat exchangers. Bursch 4/2/1 piping will accept a number of mufflers. The exit pipe will be on the correct side. Edelbrock and similar suppliers will have muffler sizes that match or are close to the Bursch.

My train of thought was has anyone done dyno testing with the mufflers we commonly use rather than just saying it’s the muffler Porsche used and we’ve always done it this way?
The T4’s all have ~ 100hp and there’s a difference between 83hp and 123hp.

@Empi

I'm a HUGE believer that the design of the primary tubes and their collectors have a much greater effect on exhaust flow than anything else.

The tubes have to be sized for maximum airspeed with minimum restriction.
Going too big is as bad as going to small in regards to diameter.

Primary size has to be "matched" to engine flow.

Primary length to collector is the next critical thing. IMHO the ss heat exchangers appear to be OK in size (up to 2.0l) but a bunch too long and the paired tubes are NOT 180 degrees to each other in the firing order.

I found a post by Jake Raby where he said "4 into 1 with short primaries" was best overall for a street-based performance application.

Look to Tangerine Racings design for an elegant solution to this problem.
In Chris's set up he uses fairly short primaries that go through two collectors.
His design first collects 2 pair of opposing cylinders and then collects the output from the first collectors into a single collector for the whole system.
This is a classic tri-y collector set up.
If it works like it should you get a negative pressure vacuum reflection from both collectors that can increase VE through the engine at two different RPM ranges.

There's lots of arguments "4 into 1 VS Tri-Y"...
Sometimes it seems to help.
Sometimes it doesn't.

I like Chris's design!

A well-done primary system increases VE.
I do not believe a muffler could actually increase VE over any other muffler design that had the same flow rates in CFM.
You CAN change how it sounds just not how much volume it flows.

I like David Vizard's stuff! He calls himself an engineer, he's an "engine design professor" in my book. His use of 30-degree intake seats is damned interesting to me.
Here's one on muffler design. Per his video he believes mufflers can only equal straight pipe exhaust. Gets good at the 20 min mark but whole thing is worth watching...

https://www.youtube.com/watch?v=5keTM9eyCOg

Im a bit of a data junky and actually hoping to collect some data specifically related to this as soon as my car goes back together. The math that Megasquirt uses for fueling in speed density mode is such that the "fuel" map actually is actually a Ve map. Once fully tuned to target AFRs the resulting map is representative of the engines Ve across all operating points.

I currently have a built 2056 running Megasquirt tuned on a 4-1 Eurorace header setup.

I also have a Tangerine 4-2-1 header setup waiting to go on my car this spring. In theory, once installed and retuned to the same AFR targets I am currently running I should be able to see any changes to engine Ve across the entire operating range between the two different header configurations.

Granted this will only be representative of how it impacts my specific motor, which is quite a bit more cammy than stock, but should be some interesting data none the less. My hope is that the 4-2-1 system helps me pick up some torque in the midrange, but we will see.

Anywhere you have to add fuel will be directly related to the change in VE caused by the header design ALONE!

You should make a stand alone thread!

Get as much data as possible on both setups please.

If I ever get time, I'd like to build a dedicated DEFI intake system for the T4.
Tuned length, maybe electronic throttle, MAF/MAP, cruise control capable, COP.

I'd really appreciate the data on a hot 2.0 regarding the exhausts.