HTT/ATS Manifolds...concrete evidence?

[nps]

All things being equal (intake efficiency, exhaust efficiency, turbo efficiency, etc. ) more boost is better (up to the turbo efficiency limit) because under pressure the air is more dense. More dense air can burn more fuel, which creates more power. Or at the same fuel delivery rate, the fuel is burned but lower egts are produced due to the cooling effects of the increased volume of air.



However the ability to deliver the same volume of air (i. e. same number of molecules) at a lower pressure is good because the turbo isn't working as hard to cram all the air molecules into the cylinder.



That means that you have more headroom to add more fuel/egts to the mix and bring the boost back up to 40psi. :-laf

 

[pwerwagn]

However the ability to deliver the same volume of air (i. e. same number of molecules) at a lower pressure is good because the turbo isn't working as hard to cram all the air molecules into the cylinder.

And, the same volume of air, at a lower pressure is also good because it does not take as much energy to move the air. your drive pressure is reduced because your boost pressure is reduced.

Plus, your charge air will more than likely be somewhat cooler when it leaves the turbo at 32psi as opposed to 42psi, so you may possibly end up with a denser, cooler intake charge when it reaches the motor.

 

[RMalone]

Damn you guys are good!!

 

[rivercat]

Would impoved spoolup be a factor or just the improved/same flow with less pressure?

 

[kelly4463]

From what i read about the ATS and HTT manifold santa is going to bring me the HTT for xmas Oo. I hope

 

[hasselbach]

The loss in boost is the same as with the exhaust manifold, the turbo is not having to work as hard to move the same ammount of air.

if the exhaust is flowing more, I'd expect to see increased boost pressure. If you are not changing the cam timing, and the intake timing is the same, you should see more boost not less boost with increased exhaust flow across the turbo.



something sounds like the ATS manifold is hampering exhaust flow with reduced boost pressure since there is very little overlap during the intake and exhaust events, whereby reduced exhaust restriction would actually cause a lower boost pressure...

 

[DHayden]

I was putting it off but I guess I'll have to put the stock manifold back on to see what it does with the HTT exhaust manifold. The ATS intake is of course physically bigger and "more rounded" inside, however the the 2 bolt housings still intrude into the air path just as they do on the stocker. At first I thought this may cause turbulence but didn't know how much of an effect it would have. Obviously the airway is the same for the ATS and the stocker for where they mate on the block.



What you said makes sense and with dimensions being identical I was unsure of any performance gain, but... . my egt's were lower and then again so was boost. So... which theory is correct? I have my theory and I'm eager to hear everyone elses.

 

[hasselbach]

As I remember during the few times we put together some turbo charged big blocks for boats, that cam overlap is the biggest issue to reduce or increase boost. To tight a lobe center (lots of overlap with both valves open at the same time), will blow out boost and lower boost readings.



Think of it this way, if the turbo is seeing more exhaust flow from the better manifold, it will flow more on the intake side. If the cam overlap is not changed, then with more flow on the intake side you will see more boost, not less. The only way you would see a reduction in boost is if you opened the exhaust later in the cycle or opened the intake sooner to allow more overlap to bleed off pressure.



ATS comment doesn't make sense. A restrictive exhaust would not increase boost pressure since the turbo would not flow as much pressure, thereby reducing flow. Granted if the exhaust pressure is somewhat lower I could see the ATS system lowering pressure during the overlap cycle (which is very short in duration), but this would be overcome after the overlap period with more volume during the intake cycle.

 

[Matt400]

ATS comment doesn't make sense. A restrictive exhaust would not increase boost pressure since the turbo would not flow as much pressure, thereby reducing flow.

I can understand your thoughts of the overlap being a source of restriction but flow and pressure are two different things as flow relates to volume and not pressure.



If you were to squeeze off the exhaust system you would reduce the volume/flow of air which in turn would raise boost pressure.

Same a squeezing off a garden hose, flow is decreased but pressure goes up as the hose gets hard.



In order to have pressure present there must be a restriction and reducing the restriction can only lower the pressure.

 

[hasselbach]

I can understand your thoughts of the overlap being a source of restriction but flow and pressure are two different things as flow relates to volume and not pressure.



If you were to squeeze off the exhaust system you would reduce the volume/flow of air which in turn would raise boost pressure.

Same a squeezing off a garden hose, flow is decreased but pressure goes up as the hose gets hard.



In order to have pressure present there must be a restriction and reducing the restriction can only lower the pressure.

Close but you're missing several key issues, thus you're thoughts above are incorrect.



If you pinch off a garden hose, yes the pressure will rise and flow will reduce to zero, thus stopping your turbo from spinning, right? Without spinning you make no boost. Yes the exhaust pressure will go up but again, flow is reduced thereby not creating boost on the intake side.



Hard to prove (if not impossible) that higher restriction in the exhaust and slowing down the turbo will increase boost (it doesn't). The exhaust cycle and the intake cycle are almost completely separate events (other than slight blow down during overlap). Higher exhaust pressure will not make higher intake pressure (turbo not spinning, turbo not making intake boost, remember?)



If the turbo is restricted, it can't flow, if it can't flow, it cannot produce boost. If your theory was actually correct, then a completely blocked exhaust would make mega amounts of boost, but if the turbo is stalled, it does nothing, thereby no boost is produced.



Call a few turbo companies, they will tell you the same thing. On one big block we took off the restrictive manifolds, made custom headers to the turbos and picked up a lot of boost and lowered exhaust pressure a ton as well. Its the difference between intake pressure and exhaust pressure that moves the air into the cylinder. And that is due to having the exhaust flow without restriction.



Now for a supercharged motor, you are correct, since the SC is independent of the intake and exhaust cycles. Reducing the exhaust restriction will lower boost on the intake side due to the overlap period and having intake blow through the exhaust port more easily. Tubos and SC units are way different in the way they operate.

 

[ATSDiesel]

In order to have pressure present there must be a restriction and reducing the restriction can only lower the pressure.

You could not be more right!

 

[hasselbach]

You could not be more right!

If you are agreeing with Matt, I think you ATS guys need more schooling on turbo's and how they work. I just got off the phone with a company that I am ordering some turbo parts with, and the tech person laughed when I read him Matt's garden hose analysis and your attempt to answer why your manifold actually shows a loss of HP.



With your theory, you would show boost increases if you serverly restricted the exhaust prior to the turbo, which makes absolutely no sense since the exhaust flow is what drives the turbo in the first place. IF you ain't driving the turbo, you ain't going to get boost. Again, a SC application with restricted exhaust is a different story.



Think I'll consider the HTT manifold as a better option now.

 

[Matt400]

For comparison I didn't mean to dead head the garden hose with no flow at all.

Of course that would stop the turbo. If the ATS manifold is giving a restriction than how is it that it lowers EGT's?

 

[Fishin Guide]

I don't even pretend to know all the dynamics of the exhaust flow through the manifold to the turbo.



The one thing that stands out is this. Only so much exhaust can pass through the foot of the turbo. So, everyhting else is velocity in the manifold. This is why header diameter and length are tuned in gassers. Changing the diameter has an immediate effect on exhaust gas velocity.



This could in turn result in a loss of energy prior to entering the turbo. Not likely, but it could happen. I wonder if there isn't some sort of plenum effect going on in the manifold. Maybe a pressure drop after the valve and the loss of energy does not have the ability to force the drive pressure back up.



With all that being said, if I had a 10 psi drop going from stock to an aftermarket manifold, I would be looking for a leak on the exhaust side and then on the pressure side. Something is too far out of whack. A 25% reduction in boost doesn't sound right. And what has happened to EGTs?



Now, if there were effencies on the charge air side, this would likely reduce boost. As boost is a measure of the charge air resisting against an object vs. the drive pressure.



So, a few psi I could buy. Not 10. There would have to be much less flow (velocity) at the turbo inlet to lower boost. Restrict those cavities and increase the flow, the boost will climb due to exhaust velocity.



And yes I know that pressure is pressure, but when dealing with velocity and energy, these are not static measurements. and they have to be balanced against the turbo which is eating them both up.



I remember reading long ago about another makers intake and the increase in boost. Doesn't take a really bright person to figure out that was a result of intake restriction.



Are you absolutely 110% sure there is not an exhaust leak?



Dave

 

[ATSDiesel]

Close but you're missing several key issues, thus you're thoughts above are incorrect.



If you pinch off a garden hose, yes the pressure will rise and flow will reduce to zero, thus stopping your turbo from spinning, right? Without spinning you make no boost. Yes the exhaust pressure will go up but again, flow is reduced thereby not creating boost on the intake side.



Hard to prove (if not impossible) that higher restriction in the exhaust and slowing down the turbo will increase boost (it doesn't). The exhaust cycle and the intake cycle are almost completely separate events (other than slight blow down during overlap). Higher exhaust pressure will not make higher intake pressure (turbo not spinning, turbo not making intake boost, remember?)

He is not saying that the hose would be completly pinched off just restricted some, in which case he is completly right. Another example of this would be blowing air through a drinking straw and then blowing air through a piece of garden hose the same length. It takes much less effort to blow the air through the garden hose.



As to a restrictive exhaust system not increasing the pressure you have already stated that it is true with all of the talk about cam overlap. Though the overlap is very momentary there is a time frame where both valves are open and the turbo has to fight the back pressure of the exhaust system. Since boost is a measurment of restriction, and that restriction increases boost pressure like the garden hose. When it comes to making power boost is not the defining factor. Some people say that for every pound of boost you make ten hp. In some trucks that might work out but 95% of the time that is not the case. We have trucks that are putting down 500+ hp at 35psi and I have seen many trucks with 300hp and hitting 40psi. To make power you have to move high volumes of air and the less restriction the easier it can be done.

 

[DHayden]

With all that being said, if I had a 10 psi drop going from stock to an aftermarket manifold, I would be looking for a leak on the exhaust side and then on the pressure side. Something is too far out of whack. A 25% reduction in boost doesn't sound right. And what has happened to EGTs?



Are you absolutely 110% sure there is not an exhaust leak?



Dave

The 10psi drop is a culmination of the new intake AND new exhaust manifold. The boost drops and egt are shown in the first few posts of this thread. Boost and egt dropped with the edition of each manifold. I have retorqued all the bolts and I'm certain I have no leaks.

 

[hasselbach]

For comparison I didn't mean to dead head the garden hose with no flow at all.

Of course that would stop the turbo. If the ATS manifold is giving a restriction than how is it that it lowers EGT's?

Restriction in the exhaust port will slow the turbo down, regardless of volume or pressure. If you inserted a gasket between the manifold and head that blocked the flow 50%, your theory would indicate an increase in boost on the intake side.



Restriction on the turbo exhaust housing size will control at what point the turbo spools up, a smaller housing will spool up quicker and make more low end boost. Not so for the restriction in the manifold which will make the opposite occur (we are not talking about a naturally aspirated motor either as in header primary piping).



I'd figure that the boost is lower at part throttle with the ATS unit due to the simple fact if it flows better, there is less pumping losses to overcome, and therefore the engine will not require as much fuel at a given RPM to produce the same HP amounts (and we know fuel creates heat, and therefore less fuel, lower EGTs and less boost made by the turbo for the same HP produced).



I would also figure that at any given fuel amount injected, that a properly designed manifold will make more intake boost due to the fact you will have more exhaust flow (ie less restriction by the exhaust manifold which causes more heat and energy to drive the turbo) which will create more boost on the intake side.



Some of you keep comparing the effects of exhaust pressure as it affects a SC motor vs a turbo'd motor.



I think something is definitely wrong if you are losing 10 lbs. of boost with the ATS set up.

 

[DHayden]

Sorry the results weren't in the first few posts, but here they are side by side:



Stock intake/exhaust

Max EGT:1228f pre turbo

Max Boost: 42. 8psi



ATS intake and stock exhaust manifold:

Max EGT: 1214F

Max Boost: 36. 9



HTT exhaust manifold AND ATS intake:

Max EGT: 1172

Max Boost: 32. 7



Now for each of those readings I went redline 3rd and 4th gear 3 times each so I would have a standard known reference for egt and boost. Since then my highest Boost is 33. 4 psi and highest EGT is 1199F but these were not achieved under the same conditions of the tests prior.

 

[Hohn]

There's another way to look at this.



Hasselbach's position is rooted in the belief that restricting the exhaust manifold will reduce drive pressure because of its restriction. Thus, less drive pressure means less boost.



We can basically ignore velocity in the manifold because of the fixed area of the manifold outlet. You could DOUBLE the volume of the manifold (creating a plenum effect), and it wouldn't change the flow capability one bit, because the turbo outlet area is the same! If you don't change the most restrictive part of a flowpath, you haven't changed flow!



Let me say that again: if you haven't changed the most restrictive part of a flowpath, you will NOT see a change in flow. Just like a chain is only as strong as its weakest link, a flow conduit will be limited by its most restrictive portion.





Anyway--- We return to the ex. manifold. Let's say that we reduce the cross-sectional area of the manifold's runners by 10%. What effect will it have on boost? Will it flow less? What about pressure?



When answering these, we have to remember that exhaust is being driven by a rising piston. It can generate a LOT of pressure to force flow out. A 10% decrease in cross-sectional area of the exhaust manifold is unlikely to substantially affect exhaust flow overall. Moreover, the turbine housing is MUCH more restrictive than the manifold. So a 10% decrease in manifold sectional area will ONLY be significant if (and only if) it's small enough to approach the restriction posed by the turbo.



There's an expansion chamber effect to be considered that may explain the reading given by DHayden's testing. If the exhaust manifold is significantly larger than the exhaust port runners (by volume) then the exhaust gases will cool as they expand into the manifold.



So it's quite likely that the EGT drop seen onthe pryo is NOT the result of any enhancement in airflow. It could be explained by the expansion of hot exhaust into a larger volume conduit. This expansion will cause the gases to be cooler, denser, and lower velocity. So your pyro might be getting fooled by the expansion of exhaust into the larger manifold volume.



Likewise on the intake side. If the INTAKE manifold is a much larger volume than the piping leading up to it, then YOU WILL SEE A PRESSURE DROP. This is actually quite often done on gas engines to help manage wet flow around turns-- expand the area, and the wet flow will better make the turn without wetout.





So, it's quite likely that flow through the intake and/or exhaust haven't changed AT ALL. Rather, your means of measuring temps and pressures are being tricked by the the cooling expansion effect of a larger VOLUME-- both on intake, and exhaust.



The actual restriction in the system probably hasn't changed one bit with the installation of these aftermarket manifolds.



Heck, I could make an intake manifold (with HUGE volume) that would show 10psi on the gauge, even though actually pressure and flow haven't changed at all.



Now, if your boost is being measured using one of PDRs Boost Bolts, then we're back to square one on the intake side.



Exhaust doesn't have this problem.



JH

 

[Matt400]

Restriction in the exhaust port will slow the turbo down, regardless of volume or pressure. If you inserted a gasket between the manifold and head that blocked the flow 50%, your theory would indicate an increase in boost on the intake side.

Not that its a good thing to restrict things but isn't that what the MTS turbo does? Essentially it funnels down the exhaust which speeds up the velocity directed at the impeller.

I'd figure that the boost is lower at part throttle with the ATS unit due to the simple fact if it flows better, there is less pumping losses to overcome, and therefore the engine will not require as much fuel at a given RPM to produce the same HP amounts (and we know fuel creates heat, and therefore less fuel, lower EGTs and less boost made by the turbo for the same HP produced).

I can agree with that and until you mentioned it I have only been thinking of WOT conditions.



Speaking of WOT doesn't it make sense that if a turbo is capable of pressurizing the intake side to 43 lbs and the only changes you made enhanced flow in the entire system by reducing restrictions that the pressure (as in back pressure) will go down?

You are probably thinking enhanced flow will spin the charger faster and thus more psi but isn't that like perpetual motion? To me enhanced flow is simply a volume of air moving along more easy than the same volume with more restrictions.



I guess where I am stuck is that if DHayden's turbo is only capable of moving "X" volume of air based on its intake dimensions, that reducing restrictions down stream of the turbo could only lower the psi. of that same volume.