that is true unless the manifold runner length catches another reflective value at a higher rpm...please let me know if you even have a clue what I'm talking about...that way I can get you some reading before wasting anymore time typing

you completely missed the point there...some people do use that part of the powerband...now yes, for road course and drag racing where you can much more easily stay in the powerband, stacking all your VE's in the mid-> top end is what you want (dictated by used section of the powerband and gearing) Now in extreme's like auto-x you statement is 100% wrong...you need the entire powerband
please do tell me what effects a designed peak VE?...as I'm sure you know that is dictated by charge/discharge coefficents, port design, cams (tons here), turbo, rod ratio, compression ratio, fuel type, manifold pressure reatio, etc....
so please tell me how you design for an engine's peak VE. Yes, I know peak torque is peak VE but EVERY motor is different...yes every single 4G63 regargless of mods will have different VE's...great phenomenom I've spent hours discussing with some of the Penske North crew

Now these statements are true but you neglect that small turbo's peak and peter out because of the smaller hotside that start to choke them out as the manifold pressure ratio goes in the undesirable direction causing lower VE's as reversion and residual gases start to take heavy effect on the fresh air/fuel mixture capable of entering the combustion chamber.
Now the compressor side of the story is a whole other story that can be made quite happy pending the trim of the compressor wheel.

 

anyone wonder why the fullrace twin scroll mani has two wastegates instead of having the gates on the turbine housing?

 

two, maintain a more regular pressure across both sides of the turbine...easier to keep even pressure if bleeding off pressure from both pulses on bothsides...Think of that turbine kinda like two turbos...kinda

 

im not saying anything bad about twin scroll, i love full race's turbo kit, but no need to call the companies who have the proven best 1/4 miles times in the world to be just "whatever" , it just seems to me that your not looking at the hard numbers just because a manifold doesnt look "cool" doesnt mean it doesnt have function. id take AMS or Full Race's turbo kit i love both, but i have to give respect where its due, AMS' turbo kit has proven why they have the quickest evo in the world

 

Please POST it ASAP

 

your response makes no sense. once the exhaust pulses enter the turbine housing they merge, there ceases to be two "turbos" as you say. at that point only ONE gate would be required. agp has done this before.

i'm looking for an answer like... we tested on turbine housings and the turbulence created by exhausting the turbine pressure through the side of the housing detracts from any packaging benefits it creates.

if there is no such answer i will wait.

 

some good posts in this thread, you definately know your stuff.

when designing intake manifolds, if you get the runner length an plenum volume right, just like you said, there can be 2 pressure peaks. I like to get the peaks around 3200rpm and 7500rpm

one of the guys here did his senior design project (mechanical engineering) on intake manifold design for the B series honda...

 

Actually we replaced the twin scroll on the Drag Evo with an undivided Tial housing.

I still run a divided housing on my car but will replace it at the end of the season with an undivided housing. The twin scroll keeps cracking.

 

I am very aware of Helmholtz turning in an intake manifold. Catching a significant pressure wave off the exhaust valve or the plenum itself would be pure luck without some serious research and computer power. Are we now qualified to chat???

The key word in your statement is SOME. Yes, for a person that spends time in first and second gear dodging cones, where speeds are so slow and turns so tight that you can easily overcome your available traction, shifting up a gear and reducing the gear multiplication of TQ might benefit from added low rpm power. For everybody else, its pointless. Well.... maybe there is that one guy that tows a boat behind his Evo....

We can go on and on about every nuance of a motors VE but I am trying to keep things simple and on track. Lets talk about what effects VE MOST thank you.


There are many things that I have not mentioned that may have an effect on boost spikes and taper but none have more influence than turbo sizing versus VE of the motor.

 

I explained it very poorly...when running a twin scroll properly imagine you divide the motor into two...as you have essentially split the exhaust housing into two.
Now each half works seperately from the other as to its effect and pressure build on the turbine wheel as one side effectively has a larger A/R than the other.
Now to control the exhaust pressure as best you can, you dont want to bleed pressure from the lower pressure side (bigger half of the exhaust housing) as it is still not effecting reversion and is still trying to spool hit its target pressure.
The small side is now at its pressure and bleeding off...
when you run a regular ewg do you want to pull all the exhaust pressure from one runner? no...you want to evening pull the pressure to keep the pulse strengths as even as you can.
I really suck at explaining things but hope I helped clear it up some.

 

Thank you. We appreciate the comments.

While the Drag Evo is a good indicator of ultimate power production we can get out of an Evo, we also pride ourselves on our Time Attack Evo and what it shows we can do for spool, power band, and longevity of our products.

That being said, we are MOST proud of our customers. While breaking records and winning races is cool, knowing that people choose to spend their hard earned money on the products we produce and sell is the absolute BEST feeling. Especially considering there are a lot of other great products out there to choose from.

Thanks again

 

so to sum it up we were arguing the same thing...just you wanted to stack all the VE's at the top end for drag racing...makes sense for a drag racer...
as for the auto-xers time in gear (just like drag racing and road course) is the key to winning...just ask audi and top fuel cars (who basically run a cvt in the form of a clutch)
so shortenging gearing vs. broader torque curve doesn't always win...

 

I am glad that at least somebody understands torque curve v gearing. I just wish you wouldnt insist that this only benefits the drag racer.

If people want to spend their time and money chasing better spool so they have a higher peak TQ number to brag about or get that sledgehammer feeling for half a second when they hit the gas, thats fine... I just hope they arent too upset when they get smoked in the 1/4, out accelerated coming out of a corner and down the straightaway, or blown off the highway by the guy that spent his time and money increasing upper RPM TQ.

 

no, I was mearly saying that stacking ve's at the top end hinders spool up. My point wasn't to have a VE spike like a ****ty off the shelf domestic. I did say flatten the torque curve = level out VE's. As I'm sure know and would have noticed in last months scc...look at your longer rod ratio'ed 2.1 vs. the 2.3L and the torque curves up top. Notice the more steady, less peaky torque curve of the longer rodded 2.1? I'm also sure the head and valves appreciate the extra shroud room too
I'm not saying to design for 3000rpm just saying that if its done it will help with spool up buy shifting ve's lower...it just reshaped the torque curve...besides if you can catch two reflective values as Geoff and I are both talking about, what do you have to loose by shooting for 3.5k and 7.5k? why not do 4.5&8.5k for drag set up?...
Nascar teams have been riding the 2nd, 3rd and sometimes 4th reflective values on intake designs...
manifolds (intake and exhaust) normally don't dictate where peak ve will occur but only shift the curve around it.

I think you have me all wrong by thinking I'm saying to only raise low end torque. I'm a fan of raising your torque as much as possible for your gearing band (leaving a littel fudge room of course)...some guys gearing band is sadly 3-8k though...but serious cone chasers are few and far between (I was one in the Formula SAE car but not in any of my cars)

 

I wish full race would built an Evo and shatter AMS's record, Then there wouldnt be anything bad to say about the twin scroll.