Hmmm. I've been following this thread closely; I think it's likely the most intellegent thread I've read in recent history. It's interesting to watch the counterpoint of two people willing to stick their necks out in an intelligent conversation-- 99 White Lite championing modeling data and measurements, and truckin in the corner of real world experience. I'm not an engineer, and my L is still totally stock, so I'm firmly in the center, trying to grasp any nugget of truth that seems to fit both sides of the discussion.

Here are some of my thoughts...please pick them apart.

1)The eaton is a positive displacement pump, that until taken to its extremes of normal use, will produce a given amount of air at its exit per RPM. Since it is mechanically linked to the 5.4L engine, it will supply air to the combustion chamber at a fairly linear rate, with the difference between supply and demand represented as boost typically measured by L owners as PSI.
2) The second stage of this system is the 5.4L engine. Its design determines how efficiently it converts the air/fuel to mechanical power, minus the power taken to pump the air/fuel through the heads. At some point, you exceed the intended amount of air being forced through the heads, thus decreasing the overall output of the total system.
3) This is the sole point of power production throughout the system; therefore if you exceed any of the parameters designed into the heads, you not only risk increasing the pumping losses, but also risk lowering the efficiency of the capture of energy conversion. Another risk is actually causing damage to components within the heads, such as overheating the valves, or damaging the sparkplugs. BUT-- this is where you must take advantage of any additional air/fuel supplied through modifications to the first stage.
4) The ECU, through variable programming, is adaptable to control this process over a large range of conditions; However, this programming is only as good as the knowledge of the person supplying the code. That is why a tuner session on the dyno for your particular vehicle is the most productive.
5) Increasing the efficiency of the system by porting the heads, or adding headers, may reduce pumping losses, but will not supply more air. Changes within the combustion chamber must be taken advantage of by the tuner.

Questions:
1) At what point does altering the mechanical ratio of the M112 to the 5.4 (overdrive pully) exceed it's efficiency range, and start overheating its output?
2) Is the reason many people are munching sparkplugs because we are starting to exceed the design of the combustion chamber?
3) The heads were designed for natural aspiration. At what point does increased pressure in the intake manifold exceed the ability of the heads/valves to operate efficiently?

Thanks guys...you've got a lot of info in this thread!

 

LOL So true!!!!

 

I haven't changed the wording in any of my posts. If you look at the time any of my posts were edited it was mere minutes after I posted to correct obvious spelling and word mistakes since I usually posted before proof reading.

I will admit the I was gloated into making bold claims. For that truckn, you are right. I obviously need to learn a lesson about internet "discussions". If I make a statement about something and choose to stick to it, I need to make the statement that these assumptions are within reason. To me 4.6 to 5.4, 2V to 4V are similar enough to be considered together. Obviously 1/4" intakes and B&S 5hp are not.

In order to substantiate your point, you proposed those theories. My immediate reply should have been to withdraw from discussion on those subjects and state that they were outside the realm of reason. For as soon as I made that mistake, you continue to used the argument "They most certainly don't make the power" and use that as arguments that all of my statements are wrong. This appears to by typical of the internet expert.

Since I've lurked on several boards for years, and sometime even registered, but rarely ever post, this was my post to learn my lessons. Well, lesson learned.

Now if you can come out from behind the curtain of real world experience (yet with no data to support you claims) and I will come out from the work of equations and logical thinking (which are not backed up my any experimetal data either) maybe we can reach a happy conclusion.

I originally posted this message as my theory as to why many of the modifications people were making downstream typically showed small to insignificant gains. Now lets look at FACTS, and only FACTS. These FACTS have to be backed up by logical reasons and can be sustantiated.

FACT-By the very nature of a positive displacement blower, the airflow is largely a function of inlet density and speed. There are other things that play a very small role, like downstream pressure. The published data for the eaton are very similar to every other similar compressor on the face of the Earth. Changes in downstream pressures make very small changes in airflow.

FACT - Power is energy released from the fuel, and the only way to put in more fuel, is to put in more air.

FACT - Lowering dowstream pressure does have the effect of lowering the power draw from the blower, and lowering blower outlet temperatures. Both of these things are benificial and can lead to an increase in power. The magnitues of these changes are something that I can not quantify at this time. The blower part I can, but not the temperature.

FACT - There are lots of other things in the system that lead to the final power rating. A cooler air charge temperature allows increased timing (assuming yoy are not already at maximum brake timing). A tuned exhaust will reduce pumping losses that can lead to changes in power, once again, by a magnitude that can not be quantified by me, yet.

My theory on the subject, and what I do with my pocket book: To get more power, upstream and blower mods is where I will concentrate. Downstream mods make changes at much slower rates. Also, the magnitude of gains from downstream mods will be less that their naturally aspirated counterparts on similar engines. I think that if you look at downstream mods, the $$$/hp is probably much greater than upstream mods. Once again, I must state the boundaries. This assumes you are only changing upstream parts that are a bottleneck. If a throttle body isn't a bottleneck, then the $100/hp that is costs is obviously not necessary. This also assumes that the beginning points for any of the changes are normal starting points, not "potatos in the exhaust."

If you [truckn] have your theories about why L owners aren't seeing the magnitude of power changes their naturally aspirated counterparts are seeing, please post them as well. My theory is only a theory, and maybe can be proven wrong. I feel I have substantiated it somewhat, but obviously lack the real world data to back it up.

 

Well, I’ll throw a few cents into the exhaust discussion. Forgive me for being lazy and not spending the hour it would take to play “point-counterpoint” (BTW, I admire and respect those of you who have!).

Back in March ’01, I posted the following with respect to a “H-Pipe” question. Feel free to use all that applies . (The entire thread can be found HERE.)

The word scavenging has only been mentioned by Silver01. An exhaust "header" is designed to scavenge the cylinders at a specific RPM with negative wave pulses timed to meet the cylinder when both valves are open. The flow momentum created when these negative waves collapse in the cylinder can have significant results on a normally aspirated engine with EQUAL length exhaust tubes (and only 14.7 psia to fill on the intake side). On a ‘boosted’ engine, the momentum effect attributed to the ‘header’ is less with 22+ psia available for filling. ‘Long-tube’ headers will have a greater scavenging effect with at lower RPM and ‘short-tube’ will have more effect at high RPM.

Now for some advertising dribble from Dr Gas ( http://www.drgas.com )

The Dr. Gas Crossover

Remember that radio and TV commercial about the piston engine going "Boing-Boing," when it out to go HUMM? Well, all V8 engines with 90 degree cranks, have an out of sync imbalance in their firing order between the right and left cylinder banks. Yes, they do go "Boing-Boing." The firing order imbalance is a necessary sacrifice for dynamic balance of the rotating and reciprocating crank, rods and pistons. Each time the firing order is completed (two full revolutional), two cylinders within each bank will fire and exhaust within 90 degrees of each other. These two cylinders will be exhausting into the header collector or exhaust manifold almost simultaneously. This overlapping condition creates a lot of back pressure and a pop sound. Meanwhile, the opposite exhaust manifold has no activity (or pressure) in it at all. This is where the characteristic, low harsh popping V8 sound comes from.

The most common way of reducing this out of sync imbalance is with rebalancing crossovers such as H pipes and over-and-under X style crossovers. These provide both noise reductions and efficiency (power) improvements. H pipes are effective only at low and mid range. The over-and-under X crossover works a little better but still does not completely rebalance the exhaust at high RPM.

Dr. Gas, Inc. has developed a new generation of crossovers that uses a tangentially siamsed junction, in place of the H or over-and-under X. It evenly splits, smoothes, and synchronizes exhaust pressures at all engine speeds. The high and low pressure pulses in the two pipes are evenly imposed on each other, leveling out the pulse time history pressure differences between right and left cylinder banks. Re-synchronizing the exhaust pulses reduces back pressure, cancels sound, and provides additional scavaging. Tests have sound 6 dBa (75%) reduction in sound levels, and increases of 10 to 30 hp, and up to 40 ft-lbs. of torque! Economy, and throttle response are improved. Exhaust flow after the crossover is completely smoothed out. The job the headers started is finished.

One of the most appealing benefits of this system is the modified exhaust note. The deep growling and popping sound is replaced by a higher pitched smooth sound. The exhaust note is similar to a 180 degree header system without the nightmare of tubing.

Dr. Gas crossover kits replace the first 3 to 4 feet of the exhaust system with pre-bent mandrels pieces. Simply measure, cut and weld into place. The system is universal fit for most header applications. After the crossover, any type of dual exhaust, converters, or mufflers may be used with little or no effect on power. Vehicles that have problems meeting sound limits at local area tracks can also benefit with an increase in power tool. And so, the piston engine can go HUMM!

 

Well now.....that was fun.

I think MR. truckn has a very strong grasp of what is happening in the real world. Good job man, I enjoy reading your stuff.

The other 2 folks are interesting and I might let them tune my B&S......maybe.

Good thread
Dale

 

I'll jump in here. New L owner, mostly theoretical background.

(1) According to Eaton's specs and graphs (see the Eaton M112 Web page), the M112 is already significantly overdriven with the STOCK L pulleys. M112 efficiency is already in the toilet by 10K, which is well under stock Lightning supercharger RPMs at engine redline. Why do you think SVT didn't just add a 6# pulley and agressive knock detection in the 01 Lightning upgrade? Power should increase in a roughly linear fashion with boost in the supercharger's relevant range. This clearly does not happen with the 6# pulley, which makes only marginally more power than the 4#. This is a clear sign that the M112 is out of gas. Caveat: The SVT version may be some special M112 different from the published specs (but I seriously doubt it).

(2) Sparkplugs get munched because of detonation. Detonation is caused by a mixture of pressure, heat, and spark advance. Assuming a given octane rating, increase any of these and the tendency to detonate is increased. I suggest that the muched plugs are due to a combination of excessive boost and excessive timing.

Those with practical experience can flame away.

My $0.02.

TLS

 

This made me chuckle. I posted a set of compressor maps for two systems showing exactly how the differed in relation to changing engine parameters. Truckn doesn't try to disprove anything I posted, but does manage to tell me I'm wrong. Good show

This is where it becomes obvious to me that you really didn't understand any of what I posted- these numbers have nothing to do with an engine. Nothing. There are simply compressor maps- if you create these conditions (compressor RPM and delta-P across the compressor), this is what it will flow. The engine is what determines what one half of that delta-P will be (the downstream half), but it doesn't matter if the compressor is on an engine or a flow bench. The numbers will be the same.

The bottom line is that different types of compressors react in fundamentally different ways to changes that you make. Are you willing to port and polish your L's heads to gain an additional 3-6% (at best) in flow? Because that's all your compressor is going to supply at a given RPM.

You seem to have this idea that if you change your engine to accomodate a potential increase in flow that the compressor will supply whatever it needs. I mean, it works for normally aspirated engines and even Vortech vehicles, so why not yours? Reread my post and see if you can tell me why it won't work that way.

Remember that those compressor maps represent the real-world flow that you will see under the conditions shown on the axes. Its really just empirical data lumped into an easy-to-read chart. You can't change it unless you're planning to violate the laws of physics, and those laws can't be ignored nearly as easily as you ignore reasonable arguments

 

White Lite, I have studied superchargers now for four years as part of a false advertising lawsuit between two centrifugal supercharger manufacturers. I have looked at scores of compressor maps and read (and written) thousands of pages on the subject and conferred with experts for countless hours.

While Roots blowers are only tangentially related to my work, your explanation of the relationship between a positive displacement blower and its host engine is the best I have seen. Light bulbs going off left and right. What I had never done before was compare the mapped flow versus pressure ratio differences between a Roots-type and a centrifugal (technically speaking, SAE standard J1723 applies only to centrifugals, so I have never seen a true "map" for a Roots blower, only the Eaton charts).

In short, I think you have hit the nail on the head in explaining why the upstream mods are so much more effective than the downstream mods for a ROOTS blower. It's a shame that the 112 is so close to its design limits stock, as spinning an intercooled Roots blower faster is a total no-brainer mod.

Thanks for your contributions and for weathering the flames with grace under pressure. Well done!

TLS

P.s. - my engine is bone stock, and will likely stay that way for the foreseeable future--with the exception of a cold air hose to the stock airbox, Factory Tech valve body/deep tranny pan, deep-sump oil pan, extra transmission and differential cooling, and maybe a throttle body with the intake port-matched and extrude-honed (I am setting up the truck for autocross). I may get a chip, but only to change the shift algorithms. [one day when I'm looking at my $20,000 full-race Lightning engine, I will have to eat these words ]

If, however, the Kenne Bell blower sees the light of day, I will probably do the swap. I think the Eaton is already maxed out on the 5.4, as confirmed by Richard Holdener's excellent Kenne Bell article in MM&FF. Plus, add up the cost of mods to get near 500 HP and compare that with the undoubtedly more reliable Kenne Bell swap.

Once again, well done.

 

You goofballs are pretty outspoken considering you admittedly have almost no experience between the two of you with what you're talking about.

What a crock. You'd better check yourself before you start firing off pompous statements like that.

No, they are NOT simply compressor maps. They're heads and cam. You're taking something I said and attacking it as fallacious, completely out of context.

quote:
--------------------------------------------------------------------------------
Originally posted by Keith Shaw
If I were to put a set of ported heads with large lift cams on my S-Trim supercharged vehicle and the corresponding boost went down from 12.5 psi (P2/P1 = 27.2/14.7 = 1.85) to 10 psi (24.7/14.7 = 1.7), I could expect an 30-50% increase in corrected mass flow into my engine.
--------------------------------------------------------------------------------

Then I said:
--------------------------------------------------------------------------------
Hate to sound like I'm tryin to rain on anyone's parade but I defy you to show me a 50% gain in mass flow from intake porting, intake valves, and cams.
--------------------------------------------------------------------------------

Now you attempt to tell me I'm talking about compressor maps? I'm not. And that I have no understanding of any of what you're talking about? Wrong again.

Read what you wrote - "If I were to put a set of ported heads with large lift cams... (snip).. and boost went down form 12.5 psi (snip out formula for laughably irrelevant pressure ratio, which was thrown in to make you look like a brainiac) to 10 psi (basic pressure ratio formula again for no reason), I could expect an (grammar error, I'll overlook it) 30-50% increase in corrected mass flow into my engine."

Once again I will say: Ported heads and high lift cams (not duration I might add) = 50% gain in mass flow? Nope! You can grab your compressor maps and unclick the holster on your pocket protector slide rule to "prove" that compressor maps are god, but talk to any tuner with a dyno about whether your Vortech-powered car will get a 50% gain in mass flow from your heads and high lift cams and he'll see that you're a rookie and if he's nice he'll gently tell you you've been reading too many magazines.



Who's the one doing the ignoring? Grow a pair, and respond to what I really wrote. Or not, and stay ignorant. Either way, you best check your facts before you get on a soapbox with a pathetic antagonistic rant based on - whoops- your own misunderstanding. ""

I'll post more later, gotta go to work.

 

Truckn,

I'm sure Keith will come one a reply shortly, but since he hasn't, I'll offer up an explanation of what he meant.

The compressor maps have nothing to do with engine performance, power, blah, blah, blah. I think we can agree to this. The maps show variables that are obtained from benchtop measurements. For each of the compressors, you control inlet pressure, exhaust pressure, and speed, and measure the mass flow.

For the eaton blower, the results show a 2D map with a line. That means mass flow is dependant on inlet pressure and speed, with a linear relationship between the two.

For the vortech, its a 3D map. Since you can't look at a 3D map on a computer screen, the plot mass flow vs. pressure ratio at fixed speeds, and the results are represented as speed "lines". They are actually curves, though, not lines, and the relationship is not linear.

Now that maps are out of the way, lets talk about Keith's comment. His comment was a demonstration of the role dowstream pressure plays in calculating mass flow. He tried to explain it in real world terms. To actually do the measurement, you want to change downstream pressure. In the case of the maps, it was benchtop. In the case of the engine, it will be cams, heads, exhaust, etc. He said IF you changed the engine enough to lower the boost. Now this isn't trying the state the practicality of that magnitude of change. Its just stating that if you did, these would be the results.


Lets take another look at the calculations and try and use the same numbers for each of the compressors. The rpm is an unknown, so we'll look at several.

For 10 psi DP, Pressure ratio = P2/P1 = 24.7/14.7 = 1.68
For 5 psi DP, Pressure ratio = P2/P1 = 19.7/14.7 = 1.34

Now mass flow through the Eaton Blower,
@4K rpm, flow at 10 psi is 180, 5 psi is 200, for a +11% change in flow
@8K rpm, flow at 10 psi is 420, 5 psi is 440, for a +4.6% chang in flow
@12K rpm (the mose relavent since it is in the area of peak power), flow at 10 psi is 660, 5 psi is 680, for a +3% change in flow

Now we'll look at the vortech,
There really in no relevant speed, but we'll try and get close with the 35K rpm line. At Pr of 1.68, the corrected mass flow is about 50 lb/min. At Pr of 1.34, you've already fallen off of the map and would need to spin the blower faster, but if you keep the rpm the same, the line ends at a Pr of 1.5, and the corrected flow is already at 65, a +30% change.

I chose to look at the numbers this way so you can see that on the eaton, downstream pressures have no real effect. Even with extremly large changes, the flow doesn't change much. On the Vortech, changes of that magnitude change the efficiency dramatically, yet the mass flow is still substanially higher. The point that I looked at on the end of the 35K rpm line, the downstream pressure was at 22.1, just 2.5 psi below the starting point, and already flowing 30% more air.

Truckn, I hope I did a good job of explaining the point. Previously, you totally bypassed the whole point Keith was trying to make, and chose to tell him he was wrong. You didn't make any effort to rebutt anything he said. This explanation should go a long way towards helping you to understand our point of view. Don't worry about how the pressure changes were made, only that once made, here is the effect. On the eaton, very small flow changes are made. On the vortech, the flow changes are huge.

I might not have the experience of having this particular engine configuration on a dyno, but these compressor maps are physics. You can't "tune" physics, and say its a combination, or the system, or a package. One pump feeds the next, and 100% of the second pumps mass goes right through the first pump. The second pump dictates the downstream pressure of thr first pump, and therfore its performance. On the eaton, I think we have done a good job of showing that the downstream pump has small benefits, whereas on the vortech, the benefits can be huge. It doesn't take running this engine on the dyno and the track to understand how it works.

Most people just throw money at parts that a tuner sells, without really understanding what they are doing. They make more power on the dyno, or run faster at the track, and they are happy. I choose to understand what the changes I make will do, and have an expectation before I do them. In fact, I resent the comment that a poster made of leaving me to tune the B&S engine.

And this isn't directed at you, truckn, but any monkey can throw parts at something till its better. I work with technicians that just throw parts at things till they are fixed. I don't have a superiority complex, or inferiority complex. The reason I get paid the amount I get paid, with the peice of paper I earned, is because I understand what I am doing. I understand the principles that drive things, and the physics involved. If someone tells me they left their eaton at the same RPM, and suddenly picked up 50 hp somewhere, my reaction isn't "Wow, that's awesome", its "There is no way in hell that can happen". Then I question the results and get to the bottom of what happened.

I will admit to not knowing the exact results the exhaust plays (spedifically long tubes) in the system. I do know that I can figure it out. I also know enough to figure out that mass flow won't change enough to see a difference in power associated with it, and the only difference in power will be associated with the pumping loop. I also know enough to understand that on the L engine, you will never see the magnitude of HP change (in %) that you will see in a naturally aspirated engine. I also know enough to know that truckn's comment about the exhaust being very important on a supercharged engine was probably true, but it was an assumption based on a different style of supercharger. Physics alone, which no one can argue with, can prove that wrong.

 

This is definitely the best post I have read so far (as far as technical content - bashing aside). I don't know why it's not STICKY yet.

White Lite, Keith, and Tim - thank you for remaining relatively civil. Truckn, while your posts seem a little abrasive, I still have to thank you for prodding the other 3 posters to re-explain their theory in even better terms for the rest of us. All of you should be congratulated for an oustanding effort - it's evident that a lot of thought went into everyone's post and we're all better off for it.

 

I want to see more formulas and line graphs.

 

Ok Quick Question...

I dont have a degree and As I posted before I dont undertand most of the acronyms used here.

But if I am running a 2# pulley on my truck and my aftermarket boost guage says I am making 11lbs of boost max. Then I add Long tube headers and a exhaust system and the indicated boost drops to 8-9 lbs of boost. Doesnt that decrease in cylinder pressure mean something ??

Wouldnt it then be safer to upgrade to a 4# pulley knowing that my cylinder pressures are back up to where they were ?
As opposed to being 2# higher ?

In summary I am NOT talking about any gains in HP from the exhaust but simply talking about increasing margin of safety when going to larger pulley -

????

Doug

PS - Did anyone else read the MM&FF article on 6# pulleys where the vendor/tuner recomended 98 octane for 6 additional lbs of boost ??

 

Quote:

But if I am running a 2# pulley on my truck and my aftermarket boost guage says I am making 11lbs of boost max. Then I add Long tube headers and a exhaust system and the indicated boost drops to 8-9 lbs of boost. Doesnt that decrease in cylinder pressure mean something ??

What you said is true, but realistically you are only talking about a reduction of 0-0.25 psi. Unfortunatly, I haven't done this experiment, not had a chance to model it, so that was purely a guess. So, realistically, I don't think you will see enough of a change to make a difference. The +2# (to 4#) increase is a far larger increase than longtubes could dream about changing.

 

I think White Lite did an excellent job of further explaining the point I was trying to get across.

I'm curious as to where I ever said that. I've been tuning Mustangs, Camaros, and motorcycle engines for years. I work daily as an automotive research engineer doing engine and vehicle calibration work along with measurements for chassis parasitics, vehicle dynamics, and emissions. I'm in this position precisely because of what I know about vehicles and engines.

It may sound a little odd, but I'm glad truckn has contributed his comments to this discussion. I don't think these points would have come across nearly as clearly without the necessary defense that has been made.


Remember, I said 30-50%, which is based on the performance of the compressor. 50% is probably more on the unrealistic side (IOW, you'd never see the downstream pressure decrease enough to get the change in delta-P that would lead to a 50% increase), but 30% is quite reasonable for many setups. Look at the Eaton curves and tell me how you'd get a 30% increase by changing heads or cams.