Exhaust Collector Discussion

[slw240sx]

that work is kind of rough for a high dollar race team...
that much money invested and i would remade that and focused on getting rid of those cheater cuts and pie cuts. i like the gradual bend on the main tube, but it completely screws it up going with that sloppy angled "cheater cut" then pie cut. that kinda follows my idea that it does not have to be perfect to make power. that charge piping would never fly with me especially if it was a high dollar build like that. i would have done it over or made whom ever built it do it over. how ever that thing made what 1600 almost 1700whp and goes over 200mph? sloppy work but great results.

notice the thin wall collector! now that is a much better collector then i use in production. i bet that is burns 321 stainless. looks to be double slip fit and not welded too. id love to get a look at the hot parts on that thing.

[ForcedFirebird]

You saw the prototypes...











How about some cast iron to 14ga tubing...



Cast iron to cast iron...

[slw240sx]

looking good overall ! i like that runner on the header that first one that i make super short. I like the way you figured out how to lengthen it. that cast stuff i have to give you props, i normally wont even touch the stuff.


http://i158.photobucket.com/albums/t...lscar001-6.jpg
on this, is this stainless steel? can i offer some pointers? over all the weld is nice and straight and consistent, but i spot a major issue. one i really really suffered with for the longest time until someone helped me out. Gas coverage! what are you using on your torch cup wise? are you using a gas lense what size cup? how much post flow, how many CFM of flow on your regulator for SS?

[ForcedFirebird]

looking good overall ! i like that runner on the header that first one that i make super short. I like the way you figured out how to lengthen it. that cast stuff i have to give you props, i normally wont even touch the stuff.


http://i158.photobucket.com/albums/t...lscar001-6.jpg
on this, is this stainless steel? can i offer some pointers? over all the weld is nice and straight and consistent, but i spot a major issue. one i really really suffered with for the longest time until someone helped me out. Gas coverage! what are you using on your torch cup wise? are you using a gas lense what size cup? how much post flow, how many CFM of flow on your regulator for SS?

I use all kinds of cups, tungsten and CFM values pending wall thickness, material and rod size. You can be concerned all you want, but that's fuse welded, no filler.

The collectors I posted earlier are 304 SS, 16ga, and are going on these "useless N/A headers" I've been picking away at for almost a year for my e30...

[NateD4]

What's wrong with using filler material on welds?

BTW some of those tig welds look really good. A few of them look over heated a bit.

Also for anyone that doesn't know you can remove the nitriding from the stainless HEZ by wire brushing it immediately after the purge gas is shut off.

[NateD4]

I think I need to chime in again. Story time:


When I first got into 60 degree V6s back in 1998 I was young and looking to put the baddest a$$ V6 I could dream up in my Fiero. Back then the goal was a 3.2L 14.5:1 compression engine making 400-450 HP. Many people on the forums of the day said just turbo it quit wasting your time and money. Ironically I think they were right. There's a certain achievement and cool factor in having something totally unique and thought impossible...

A lot has changed since then. Mainly the Gen 5 V6s (High Value V6). In my opinion it is a game changer. New heads, new intakes, new tech every where. Better everything.

In the mean time I've come to realize that in order to optimize an engine to the level that it sounds like we are talking here the task is monumental and certainly in my book not worth the time and engineering required.

Now I'm not saying its wrong. However, I am saying that unless you are ready to buy or write your own analysis software, buy a few thousand dollar CAD package, pay to have your parts CAT scanned in 3D to get the production 3D models (which to my knowledge are nearly impossible to get from GM), invest in $50,000 to $100,000 analysis software (CFD, FEA, Dynamics, Combustion analysis etc..) you are chasing details for the sake of chasing details.

I could probably tie up a supercomputer for a few days running a totally correct engine model that would require 2 years to construct. I could also spend a $200K to construct the engine (take a look at J Leno's Pratt and Miller billet blocked 700 HP LS engine for an idea).

There's an old adage 10% of the effort and cash gets you 90% of the way there. The last 10% of the way takes the other 90% of the cash.

[This is why 2-4 years ago one of the F1 teams spent 200 million euros to raise the redline on an engine from around 19K to 20K RPM. F1's rule body decided this was ridiculous. A season or two later the Kinetic Energy Recovery System (KERS) system was devised. Which basically is a hybrid like power boost. They figured if teams were going to spend that much money to raise redlines (which included new materials and crazy coatings), why not spend the time, talent and effort to address problems the rest of the industry could learn from.... ]


Now in my opinion (and for my project) simpler is better to a point. I'm now planning on spending a bit of time to CFD model the ports to see exactly what they are doing before I start porting. BUT keep in mind that even in wind tunnels the time you spend to do something as simple as reduce the drag (or in our case increase CFM) by a few percent is huge. On top of that it can be totally hit or miss. This is exactly why guys like WOT spend the time with the flow bench.

If you want to optimize your exhaust build a few sets and take them to the dyno. Go with a few theories and test them.

If you really want to mess with them you might try CFD (OpenFOAM is free but a bear to use... and you'll want an 8 core computer with 18 to 32 gig of RAM and a few hundred Gig of drive space). But even CFD has its limits... garbage in garbage out. If you pick the wrong equations sets or assumptions, pick the wrong initial conditions or the wrong air properties your small percentage gains mean essentially nothing.

Sorry to get off on a tangent but I think its important to keep things in perspective with your goal. If you want to prove everyone else wrong and show how cool an engine you can build have at it.

Another thing to keep in mind is that Engineering supports the build and as such the build drives the need for engineering not the other way around. Engineering to engineer is fine if you have the resources. But in all reality if you had them you would probably buy something out of the box. Unless of course you like the challenge.

As for my approach. It has changed a lot in 10 years. I've since went from NA only to Turbo and have decided to start with the latest and greatest tech GM had in pushrod V6 (which is also based on another decision process).

My current build will be somewhat of a mix between optimization and forcing more air and fuel into it. But I'm approaching it fully aware of what's in store and accepting that I'll probably spend a bit more then I need to. But I've always wanted to do a build like this we'll see where it ends up.

Just my ¢50 worth.