2.5 exhaust chest mods....

[FMP]

Without pressure sensors in half a dozen spots in the chest and tuner it's difficult to know what and when.

[FORBESAUTO]

Don't ya wish you could look in there and see what was going on! To help understand why each change made effected power the way is does instead of having to speculate. I may be wrong on some of my theories of why it improved power, but know for sure it did, or did not. There's so many variables and crap going on in there sometimes it's mind boggling! All I can say is the first chest I posted is the best all around performing setup for the way my engine is set up and my rig so far. And as I learn new info I will post for others the see and hope save them some time

[Krazymaan]

You can look in there. Just make a poly carbonate exhaust diverter. It won't last long but you will see some crazy stuff I bet.

[FORBESAUTO]

I bet you'd be amazed of what goes on in there and how dumb we really are and overthink things

[FORBESAUTO]

You really can't do too much about the 1 out of three distances that's the long vs the two which are equally short in the firing order. Meaning, two are side by side in pulse distance to tuned pair, the third jumps over the neighbour to reach the next to close. Longer distances to travel later pulse, if you believe in that sort of thing. If not it's like a Warner Bros cartoon where the character doesn't fall because he didn't study gravity. Nobody has made a crank with firing order 1-2-3-2-1-2-3-2.....lol

I thought i had already checked on this in the past with firing order, but couldn't remember if I was dreaming on not. A 2.5 firing order is 123456 with odds and evens on each sides, resulting in them firing in order from top to bottom in a row . Which is how I came up my theory on angles and low pressure areas changing timing in scavanging or stuffing at different rpms which ever is actually happening or both.

[W2F a V-King]

Yes, the 2.0, 2.4, 2.5 all that way...I always wondered about crankshaft torque bind or wind up, and vibration with that firing order and cylinder order placement.
For whatever reason it does make things easy to remember.

[FORBESAUTO]

Yeah lol!! Kinda makes me think about poor old #1 and #2 not getting any help lol!

[FMP]

I didn't feel like typing out both sides, so just assumed you'd get the single triple 123. So one fires and the next closing cylinder that gets that pulse, the 1 to 3 pulse is the longest travel, two fires and pulses one, three fires and pulses two. Interesting that one has enough effect to stuff three adequately as it passes with the port direction of three, but it's the chest pressure that seeks all . That pulse also makes it in some capacity to the transfes through the shrinking cyl volume, blow down timing etc. How it works on the transfer pressure ???That would be different from low rpm to very high rpm due to arrival time and nothing can be done about it except stuff or pressurised case or delay pulse till after transfer close. Triples with 120* spacing already have an advantage as a result of this spacing, allows for more ex duration and results in pulse arrival that is late to its tuned pair. What's interesting is the bottom cyl port shape, with direction facing out to tuner. Even with this the pulse pressure is still contained and registers adequately at least at the top of the chest and the middle port. No doubt the shaping is helping flow of gas from tuner scavenging , it only makes sense that it would help pull spent charge out but how does this all compare to the gen 1 2.4 chest above?

[FMP]

Forbes www.google.com/patents/US3813880
Old but principals apply, still a good read.

[FORBESAUTO]

Thanks for the read! Pretty much confirms what I'm trying to say about my angle theory. In my picture I used the path originally drawn in pic as the cut version and I drew in the stock path. With less angle the path between cylinders is longer from cylinder port opening to port opening. As you increase angle instead of traveling over mointain, the path is shortened by being able to go through mountain. Also changing the trajectory at which exhaust hits divider and different velocities corresponding to rpm. I realize for the most part the tuning is designed into the mota, but I do feel you can alter it some by shorting the distance between ports and playing with the length tuner. Thanks for the info, havnt read that article yet!

[FMP]

Richard and Dave???
www.google.com/patents/US4187809

[FMP]

www.google.com/patents/US4381644

[FORBESAUTO]

Richard and Dave???
www.google.com/patents/US4187809

Thats some good info!!! Best description and explanation I've ever seen of the 2.5 style chest! I'm resting and driving to Indianapolis. As soon as I get settled gonna study it some more!! Saved it to my favorites

[FMP]

Don't think they mentioned next to close is adjacent two out of three, I just glanced it.

[PanRonnie]

my inspiration
http://www.profblairandassociates.co...mouth_Sept.pdf

my idea
don,t know if it will do anything but it is nice to look at