On a V8 with the driver hot side crossing under oil pan going up to meet the passenger side for the divided inlet. Should I try and make the passenger side a similar length? I have the space and pieces to do it. Just wondered if it would help pulses/back pressure/tuning?

I know some log manifolds that merge both sides can heat up one bank of the engine more than the other.

 

Unless it's a max effort type built, I don't think it will make a hill of beans difference.

 

Probably make it worse due to heat loss from the extra pipework. Divided housings don't harness blowdown energy on V8s anyway because:
a) More than 3 cylinders per volute
b) Firing on each bank is not evenly spaced (except with flat-plane crank V8)

 

Smaller turbo/Amc401, using sch10, 321 stainless hot side. I don't think there'll be a lack of heat.

Mostly concerned from the tuning standpoint, if it makes a difference with one side having more length than the other. Since holley sniper can't tune individual cylinders.

 

No. None whatsoever.

 

Thats something I've always wondered. How can you divide the turbine and still get the same exhaust pressure and cylinder VE on both sides. Seems like one would always be slightly higher.
Different force on the blade row, same blade velocity, same angle. I Have something for water
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The angle, area, cosines, blade V is all the same I think we can ignore it. What I am looking at is input velocity and relative velocity, which could be used to find pressure for two separate yet identical turbine blade rows. I am sure the compressibility of exhaust gas will play a role as well.

 

Your looking at the wheel the wrong way. The driving force in a turbine is deflecting the momentum of the gas, while also creating a "nozzle" to create a pressure drop and jet at the exducer of the turbine.

Sure there is "some" radial torque at the turbine inducer when spooling, but very little since the tip speed- to gas speed ratio is only .6-.8:1. The divided housing does nothing except help isolate the pulses.

The turbine exducer is the only thing that drives the turbine, clip it all off and see how well it works.

 

cosine(alpha) is the angle of deflection, Density*Area*velocity^2 gives mass flow(rho Area Velocity = "mdot"), the mass and velocity which contains the momentum and kinetic energy information. I don't care so much about the math my issue is one of conceptualization- I try imagining the divided housing 'at work' and I can see the pre-turbine tubes are isolated from each other, which puts them at a different pressure potentially due to the small differences between cylinders and tubes that exists. It might adjust VE that way, especially with certain cam profiles. I would have thought the gates would open at two different times because of a difference in Exhaust gas pressure. And maybe they do, but its such a small difference it doesn't matter. Just thinking out loud, saw an opportunity to ask the question I'd always wondered.

 

There is no need to consider what happens in the impeller (angles, momentum etc) if you just want to compare backpressure on the two banks.

The two scrolls form two equal size nozzles with their discharge pressure (tips of the wheel) at the same pressure. Upstream pressure at each nozzle will therefore be determined by the volume flow rate through that nozzle. Assuming mass flow is the same for each bank, the nozzle at the highest gas temperature (the bank with no crossover) will have the highest volumetric flow and therefore the highest backpressure.

 

Thats what I am getting at, how we get away with assuming mass flow will be the same when the higher backpressure hotter bank is going to reduce VE for that bank which will reduce mass flow for those cylinders and also change gate operation. Its like that side of the turbo is on a completely different engine.

 

It is mostly pressure, that is the primary driver. There may be some efficiency to be gained from making everything equal length, but you are down in the noise on a street car. If the cam timing is conservative and the lobe centerline is pretty wide, you will not see very much difference between banks.

 

Forget about bank-to-bank difference in VE and mass flow - they will be a tiny fraction of the volume-flow difference. Maybe 1 or 2 psi difference in back pressure at full noise.

 

hehe just forget about it then. nothing to see here! Nope keep moving along


Reminds me of the book depository. He went to the book depository. The book desposi book depository, the book depos-deposi-depository, the book depository.


"Damn he could be anywhere!!!"

 

Welp idk what the concensus is. But it won't cost me anything to put an extra loop in the passengers side to makes them a bit closer to equal. The passenger side has to make a 180 u-turn back up to the turbo anyhow which in fluid, a 90° fitting is equal to adding 3 feet of strain line as i recall?

 

I agree with this but my opinion is based on Grand Nationals doing this and the idea this not an all-out, max HP project.

IMO, just build it and enjoy it and you'll never know the difference.

ks

 

It will run better with the shorter pipe.
Equating a bend to a length of straight is a rule of thumb for pressure loss in the pipe. It cannot be applied to wave tuning length nor heat loss.

 

I was just thinking how 1 to 2psi is worth 30 to 60hp on the intake side
There are still some mysterious LS myths and legends that I am still curious about, the legends of the rear cylinders l rc
I was wondering whether 1 or 2 psi can be worth 30 to 60hp, and #7 and #8 could be different by 60hp sometimes.

Logically if the cylinder is farthest it has the highest dp/dl because all of them have to wind up at the same pressure and given the extra length friction increasing with distance means the highest exhaust gas pressure and rate of change of pressure per unit length would have to be the farthest cylinders from the turbine, normally 7 and 8.
Which could potentially reduce the VE of 7 and 8.
Which should make those cylinders safer (less VE = less fresh Oxygen = richer or am I crazy?).

And that is not what we normally are used to seeing. Instead cyl 7 and 8 tend to break the most often or have the most concern. I have never seen it happen but I did tons of research and the most often broken online internet claims is 7 or 8. I usually attribute those issues to pressure leaks raising EGT but its still curious, why not 1 and 2 more often. Which is why this mysterious legend has me concerned over steam ports still, and engine level concerns.
So when I ask myself, maybe the higher pressure is dangerous? But thats just crazy talk. The valve closes then the valve closes. When it's open higher EGP Protects the rod cap and rod bearing. During compression and power pressure is much higher than exhaust gas pressure ever can be. So there doesn't seem to be any issue with high EGP on those cylinders in terms of reliability to worry about either.

 

You are really splitting hairs here. A few inches longer exhaust runner on a particular cylinder produces a noticeable difference in pressure loss and therefore back pressure for that cylinder? That difference will be minute compared to the difference in wave action in the unequal length runners - which itself is a negligible effect compared to the difference in instantaneous backpressure on individual cylinders sharing a collector or volute due to uneven firing intervals - (always an issue with cross-plane-crank V8s).

Even on even-firing engines, added pressure drop in a longer runner is probably less than the reduced volume flow due to greater heat loss from the longer runner ie the cylinder with the longer runner will probably have LESS back pressure.

 

nah, ya lose heat, thats lost energy. You increase friction with length, thats lost energy.

Lost energy plus lost energy does not equal more flow. The pressure might be lower- but that won't achieve a superior VE, because the control volume or system in question has no source of input energy besides what each assumed equal cylinder provides.

I agree there is negligible affect for say 800rwhp setups. But many run OEM manifolds which obliterate acoustics I would imagine, so its all pressure differential driven. And variations of pressure within a mostly pressure driven situation are a concern.

 

???????
I said LESS back pressure. I didn't say anything about energy.