Power

[Signal]

650performance Thank you for the information that is exactly what I wanted to know.

 

[gunk]

Your welcome addict. Oh forgot to add Uni foam filters that tuck inside the stock sidecovers, Mikes XS oil filter adaptor to use Honda xr500 filter . Like that when It's oil change time. Turned the O.D. filter housing fins down so the hsg. would match the radius of the crankcase cover on the r.h. side. astetics thing there, plus mild o.c.d. on My part.
Have a Pamco Ign on order . Points and condensor ign. at present, But She's a bitch to kick over cold. No problem when warm tho' Nitrogen gas shocks outback, rebuilt forks.
Bronze s/arm bushings, tapered strg. head brgs. TT100's both ends. If I knew how to post a pic I would.

 

[hoffman900]

Has anyone used exhaust port optimisers (that insert into the head) in conjunction with the Lillie replica head in a race engine?
Or are the characteristics of the port changed so that they are not needed or even detrimental.

It's a bandaid for too large of an exhaust primary - you're starting to see people finally figure this out with the SR/TT500s - 1 5/8" off the head for a 540cc engine that is making ~60bhp at the flywheel. If you can shrink the exhaust port, a 1 1/2" primary will support those numbers as well.

You need large 6" bend radii to make this work and you will have to step up within the first 12" or so off the head.

 

[hooser]

We built many 540 and 580 stockers and none of them made 60 hp, learned from SHell and I still sell his style of 500 and 650 head pipes all 13/4" od and 1 5/8id, he won a lot of races. These are not new motors these guys lived them, race them and made them work, they did it all to get the most out of them.
Let's see that 60hp dyno for the 540. then better have it calibrated.

 

[hoffman900]

We built many 540 and 580 stockers and none of them made 60 hp, learned from SHell and I still sell his style of 500 and 650 head pipes all 13/4" od and 1 5/8id, he won a lot of races. These are not new motors these guys lived them, race them and made them work, they did it all to get the most out of them.
Let's see that 60hp dyno for the 540. then better have it calibrated.

Gary,

You're not going to do it with 1980s thinking - just the same as no one racing a XR750 today is using anything by Axtell or Branch.

It starts with the head and a lot of time on the flowbench - and not all head guys (even if they have a flowbench) are of equal caliber.

My 2 cents..

 

[hooser]

80's hell I go back to the 70's, But you are right and they did the work, Axtell and Branch and Shell. Can't re-invent the wheel no matter how hard you try.
I had a Branch head on my evo, along with other parts. I was having issues under 2500, when I put the head on it ran from idle to over 5k with out an issue, Pulled all the way.
Would of loved to have had him do a xs650 today and see if he would change anything.

 

[hoffman900]

Gary,

Things change a lot - headers for instance, look at a current NASCAR Cup car, 1 7/8" OD tubing off the head and they're making ~850bhp. They were making about 300hp less 35 years ago and were running as big or even bigger primaries.

Here is a post from one of the premier header fabricators in NHRA, CUP, World of Outlaws, IMSA:

I don't think that is off topic at all. Back in the old days, (50's through the 80's) bigger headers, (bigger everything for that matter), the introduction of Superflow dynos to the average engine shop along with the "flow bench" in the hands of anyone with a grinder...the quest was for the maximum hp at the top of the curve. The loss of bottom end power was ignored when you could make a big increase upstairs. In most types of racing during those periods, the increase was definitely there and measurable at the track. Over the last 20 years or so, we have found,(with I'd like to think some input from me) that we only have to make things like headers as big as they need to be, in fact the work is in finding out how small can we make the back-door of an engine without losing power. This is much more to do with flow than tuning. When we find that a 1.75" tube on a 6" radius can flow the same as a 1.88" tube on a 3" radius it should change how you build headers, not to mention how large the exhaust port needs to be at the exhaust flange where the header starts... The essential realization that seems missing (to me) from tuners' understanding of the function of an exhaust system is, the larger you make a given system, what you are doing is letting the the full weight of the atmospheric pressure get to the back of the engine sooner and easier. This no longer the way to make more power. If you can see a choke on a merged collector as a valve or orifice through which the atmospheric pressure has to traverse to get to the engine, you may see that the thing to work towards is how small a choke can we get a given engine's exhaust gases through before you start losing power. And another thing to keep in mind is that in most applications I have seen, decreasing choke diameters (and the whole header for that matter, ie smaller and shorter tubes) is not a flow issue but rather a engines inability to deal with the reduction in pressure it sees on the exhaust side for the given cam timing. I think it is important to remember that only one cylinder is firing at a time, whether you like it or not. When I was able to reintroduce a 421 header design in Winston Cup back in the middle 90's, we quickly learned that ANY421 header could use at least a 1/4" smaller final collector choke while making more overall power. Having been learning about the ins and outs of this for many years, I can not help but have to look at the exhaust port itself and what I am given to work with from my customers in terms of area's. There are quite a few cylinder head guys out there that have heard my spiel, some respond and some don't but the bottom line is that I have never seen a exhaust port that I liked. An exhaust port needs to be designed from the point of view of the whole header design and system that it will be using. I am going on because your post just puts forward the grand confusion around exhaust valve vs header size and how it all works. Thanks for the input.

A step functions to reduce flow resistance the longer a tube gets. Unfortunately, Other things happen too. Any sudden area change, "small" or "Large" reflect a smaller magnitude negative wave while reducing the power of the wave that continues on down the system. They also function the opposite way to returning waves either positive or negative. They disrupt their effect, strength etc. There have been some discussions in this forum about that. Do they reduce magnitude but lengthen the durations, etc. A common term is a "reversion dam". The "larger steps" are an attempt to combine the need to help flow and reduce the effect of returning waves. I have experimented with them a lot. Used them in Cup and Drag stuff. They are more effective in 4into1 systems than in 421's. Gee, I wonder why! 4into1 headers have stronger returning waves and the dams help minimize that problem. (I thought we were building "tuned" headers??? well, we are "tuning"out) The merged collector with a restriction or choke is a better way to manage the pressure waves in a system in my opinion. As I have posted elsewhere a lot, in a V8 bent crank engine, the "pressure waves" in our system hurt us more than helps us. We can make more power by tuning "out" and "attenuating" the waves, which means "reducing" them or minimizing their effects. I remember back in the 70's, Jenkins and folks used "flange adaptors" on small block chevies so they could use larger diameter tubes. The bigger tubes definitely reduced flow resistance and the "dam" created at the head/header junction functioned as a reversion dam. In a PS application with a small rpm band, it was not required. But do the same thing in a milder SB and a automatic and you have a "dog", and the dam helps alot! but is only a weak band-aid. Many people fall into this trap. The dams are a band-aid for too large a header or collector or both. So...larger collectors=need for dams, smaller chokes=no need for dams. What I found out early on is that doing a better job of managing waves in your system reduces the need for reversion dams. You can not use as small a choke in your final collector if you use "large steps". This I think is because we give up too much velocity and wave strength. This proved out in pro-stock as large or "Big" steps required longer primaries, even in the relatively tight rpm band. This points out how the steps slow things down and the dam created was not enough to overcome the loss of bottom end power. The merge into the choke works better when we can get more through a smaller hole. If things get lazy and weak the effects of the collector is weakened. You start the header from the head as close in tube area to the port area. I will always step before 10" of one tube size. A 421 for 7000 rpm will want a primary about 17-18" long so you would have one step in that long a tube. The secondary will probably like to be about 1/4" larger in diameter than the primaries and the choke in the final about 1/4" again. If you bunch the header up front as reasonably as possible that would be good as you need as much room for secondary adjustablility and also to try and get a megaphone between the final collector and the muffler. "bunching" it up more though hurts flow so there is a trade off there. Larger tube diam. to allow more "bunching" starts the swirl down the toilet of lost velocity. That would get you started and try and allow for secondary adjustment and collector choke adjustment as that is very important for what you are doing. In answer to the last question, I like square edges to disrupt pressure waves but flow is messed up with larger steps, but that is gonna happen anyway. The way the step it is done is not a player, mostly unquantifiable and irrelavant to your application. A lap weld or simple single tube step is a very weak weld so you will see swedged steps using butt welds but that is why

Things like Intake / Exhaust flow ratios? That doesn't matter either.

Etc.

 

[hooser]

I am not really sure what the common thought is here.. Yes technology has changed but the xs650 head has not so as long as you are using that head the work was already done back in the day and even now to an extent with better machine work and parts. The 'JE pistons I sell know are much better then in the 70. Valves, guides etc. tolerance on cams etc. but the head has not, same old xs650 head. As far as performance it has always been where do you what the power. Shell did that , what tracks are you riding, he had different motors and set up for different tracks and even riders. But the head is the same, and they tried every thing under the sun to make the work, big ports,small port valve angle. But unless you have unlimited $$$ and time the xs650 and tt500 are what they are. Good reliable motors, I hate to admit it but the 4 valve 500 Honda will kick as on any tt500. Gary

 

[hoffman900]

Gary,

No doubt those guys were top of their field during their heyday, but time marches on.

We know a lot more about airflow than those guys ever could. Porters working with much higher depressions than Jerry used (looking for flow separation), pitot tubes, etc.Even Branch's Harley stuff isn't used by anyone racing them (and wanting to win) and have been surpassed by many, even within the Harley castings. The SR/TT500 holds the same potential.

The NHRA Super Stock racers are getting more and more out of castings that are 50+ years old.

A friend of mine who has been racing since the 1950s, championship engine builder and tuner as well, recently worked with a NASCAR header builder on a highly developed engine. They also implemented some things they found worked on the top World of Outlaws team.. This is one he's tested dozens of header designs on over the decades. Well they found another 12% at peak and no less than 10 % gains. This means camshaft development has to be redone. A engine that he was thought was just about maxed out after 50 years of development and boom, 10-12% gains (and more to come).

Progress never stops.

 

[hooser]

Well once again it comes down to show me the proof that you are making 60hp from a 540, show me your XS650 numbers that will blow us all away. With the current xs650 head.
They are not using the Branch evo stuff because of new design call the twin cam and in time they will redesign it. So in short if you are not going to totally re-design the xs650 or tt500 it is what it is. Reliable 70hp give or take and reliable 45hp 540, Change where the power is by exhaust, cams and carbs.

 

[650performance]

In at least one way the discussion is moot. Whether it is old or new technology used to optimize a XS650 stock head casting, you are still hemmed in by the fact that things will start breaking over 72 - 73 or so RWHP. And that power number is available with "old" gas flow technology.
The engines can live OK below that figure, but not above as Tim Witham and the Yam race department found out in 1975. When they hit 75 the engines became grenades.
That's why the OU engines had beefed up innards ... without those changes the original XS650 42 RWHP engine architecture couldn't handle the shaking, twisting and vibration generated by that much more power.
So, intellectually speaking, can modern gas flow technology enhance an original XS650 head's flow numbers? Probably, but practically speaking, who cares?

 

[hooser]

Well put, I get hung up on bogus number people put out, 60hp tt540, I saw about a year ago on ebay a worn out CHampion 750 had 90hp rwhp. So when I see # like that I just want to see the proof. Knowing they can't produce.

 

[650performance]

Gary, you and I are more or less from the same generation. In other words, we've been around a long time and the one thing we've seen in decades of racing and hanging around high performance bikes and cars is that there is bench racing horsepower and performance and then there's the real thing.
I can't tell you how many times I've heard about the 80 horsepower this or the 90 horsepower that and neither one could get out of its own way. Same thing with flow numbers and most any other measure of engine power.
Show me the dyno figures or, if that's not available, how about we do a comparative roll on as we get on to some long straight and let's see what happens. I think we both know what is going to happen.
Otherwise, STFU.
"Performance talks, BS walks" as the saying goes.

 

[hooser]

Well put, did we beat his dead horse long enough. Later Gary

 

[Jack]

Gary,

You're not going to do it with 1980s thinking - just the same as no one racing a XR750 today is using anything by Axtell or Branch.

It starts with the head and a lot of time on the flowbench - and not all head guys (even if they have a flowbench) are of equal caliber.

My 2 cents..

Hey Hoffman haven't seen you around in a long time. If you want to take the TT 0r SR 500 head to the next level,check out Jim Schmidt and no he has no ties with Yamaha. There are some limitations with the head being OHC but nothing is impossible. The SR and XS have a lot in flow and port similarities and you'll soon find out that the cross sectional area of the spigot can be reduced or the entire port for that matter without hindering flow and port velocity will shoot up. You have access to a flow bench and a hell of a porter, what do you have to loose but time that'll return a positive outcome. Forget about the #s and focus on port velocity and the #'s will come.

 

[hoffman900]

Hey Hoffman haven't seen you around in a long time. If you want to take the TT 0r SR 500 head to the next level,check out Jim Schmidt and no he has no ties with Yamaha. There are some limitations with the head being OHC but nothing is impossible. The SR and XS have a lot in flow and port similarities and you'll soon find out that the cross sectional area of the spigot can be reduced or the entire port for that matter without hindering flow and port velocity will shoot up. You have access to a flow bench and a hell of a porter, what do you have to loose but time that'll return a positive outcome. Forget about the #s and focus on port velocity and the #'s will come.

Hey Jack,

Good seeing you still around.

We're pushing 133cfm/sq-in through the MCSA of the head. Peak flow is 235cfm @ 28" @ .600" lift (230cfm @ .500) through the spigot.

With the carburetor and velocity stack bolted on, it goes down to 216.3cfm @ .600 and 208cfm @ .500

A TM-38 will flow 277cfm @ 28" H20 at full open, or 156cfm/sq-in.

This is by all means, not a 'maximum effort' deal. Looking to peak around 7000rpm on a 540cc deal on the street engine. A 40-42mm dia "MCSA" will allow the head to reach a bit over 240cfm.

The two biggest limitations with the stock Yamaha castings are:

1) material in the port sidewalls. This limits how far you can widen the short side radius. We're about at the limit of what we can do.

You can see here:

MCSA is at the port entrance to the head - it needs to be back that far as the port needs to gain area from there to slow down the air enough to get it around the short side radius without separation.

2) Valve lift. Being an OHC set-up, you're ultimately limited on how much valve lift you can run. On a pushrod set up, you can juts keep putting longer valve stems in and work with a rocker manufacturer and come up with a higher rocker ratio than stock. The Royal Enfield guys have done exactly this and are seeing over .600" valve lift without having to use more lobe lift. A win-win.

We're great on velocity - averaging about 300fps through the port. Believe it or not a bigger valve for us did not gain much in cfm, but did make the port more stable and quiet with work. A great thing since running depression can be over 3x what you can measure on the bench.

 

[hoffman900]

Jack, here is a great post by Larry Meaux (PipeMax creator):

Dan...you can use the [Search] Link on this Forum
to find other Threads on just about any Topic you can think of ?


here's some Threads from a couple of Posts that might explain
CHOKE to you

here's a very good quote from STEVES
that explains the general idea and reason why Choke
or too fast FPS hurts HP+TQ
just read rest of Posts with that in mind .

As I understand it, ports don't actually go into sonic choke at .55 Mach - but at this point (approx.) we reach the trade off where the energy required to move the air through the port becomes higher than the power increase (cylinder filling) that comes from higher velocity.
---SteveS

Posts=>


From a previous Thread

too fast Velocity FPS can be a total disaster

Note=>all 3 of these Heads were tried on
the same Short Block with all the same pieces
and Dyno Tuned for best possible HP/TQ Curve
with those pieces.


#041x SBC Heads = 165.0 CCs
1.940/1.500 valves
these are the very Hi-Velocity Heads
with too much velocity everywhere inside
the Intake Port, same FlowBench numbers

and the "BEST" Dyno test with them
600 RPM/SEC , i don't have the Sheets
that we started at 3000 RPMs and all the
rest of the Sheets , but only kept the
Copies that stood out, and these are every
200 Hundred RPM increments as its too much Info to type
every 100 RPMs, but it should give you enough Info ?

note=> at 600 RPM/SEC you get a little Needle/Seat
action showing up especially with small gas bowl
chamber in Q-Jet, so look at Fuel Lbs/Hour trend
as well as rate (Same Q-Jet Carb all Dyno Tests)

RPM---TQ----HP----Fuel Lbs
4500-419.3-359.3--178.4
4700-438.1-392.1--171.5
4900-449.1-419.0--177.2
5100-451.0-437.9--169.8
5300-445.8-449.9--174.1
5500-443.2-464.1--188.3
5700-441.0-478.6--209.8
5900-429.6-482.6--222.1
6100-424.3-492.8--227.4
6300-413.9-496.5--214.9
6500-412.7-510.8--200.8
6700-407.6-520.0--210.3
6900-388.8-510.8--221.9
7100-363.7-491.7--236.1
7300-345.3-479.9--239.8
7500-325.1-464.3--233.4
7600-312.6-452.4--226.1

Avg=>406.5-464.9--206.0

--------------------------------------------------------------------------------

with #041x Heads back-to-back on same Short Block
same basic Flow CFM Numbers, same valves, same CC's
but with Port Velocity slower and more acceptable
throughout the entire Intake Port

RPM---TQ----HP----Fuel Lbs
4500-449.5-385.1--166.1
4700-444.2-397.5--164.5
4900-455.2-424.7--177.0
5100-456.2-443.0--158.3
5300-464.1-468.3--169.6
5500-471.1-493.3--192.9
5700-470.2-510.3--199.2
5900-468.2-526.0--199.3
6100-465.0-540.1--204.5
6300-459.8-551.5--209.7
6500-456.6-565.1--216.3
6700-442.6-564.6--223.1
6900-432.8-568.6--217.2
7100-426.6-576.7--215.3
7300-418.3-581.4--224.5
7500-401.8-573.8--238.2
7600-394.1-570.3--231.0

Avg=>445.7-514.1--200.4

===================================================

with #462 castings 1.940/1.500 162.0 CC Ports
differences just 3 CCs can make when ground out in the
correct places, again FlowBench CFM between the
#462 and the other 2 #041x Heads were very close
and CFM numbers don't indicate the HP/TQ differences observed
and Ports had different Velocity Profiles.
Same ShortBlock and all pieces the same.

RPM---TQ----HP----Fuel Lbs
4500-443.0-379.6--168.3
4700-441.8-395.4--159.8
4900-450.6-420.4--164.4
5100-456.9-443.7--169.8
5300-459.2-463.4--183.9
5500-465.9-487.9--190.6
5700-464.1-503.7--192.0
5900-463.0-520.1--195.2
6100-460.6-535.0--196.6
6300-454.9-545.7--206.5
6500-446.8-553.0--216.1
6700-438.0-558.8--225.1
6900-428.4-562.8--220.8
7100-422.0-570.5--223.9
7300-410.1-570.0--219.5
7500-395.3-564.5--226.4
7600-388.8-562.6--231.1

Avg=>440.6-508.1--199.4


Quote:
Very well put - I have thought for some time that "Choke" is actually a misleading term here.
David Vizard has called it "Power Limiting Port Area", a more accurate description, but unlikely to catch on.


i just use the word "Choke"
because sometimes the Engine will be Choked by an Area
and sometimes by the same cross-sectional, but now has one of the walls
with too much local velocity FPS and/or diverging too quickly on 1 wall

in the above Dyno Test examples the
one extreme hi-velocity #041x SBC Heads
is using more Fuel, but if you try to lean it out, you loose even more Torque and HP...notice it makes Peak TQ and Peak HP lower and runs out quickly with rapid rising BSFC numbers as rising RPMs show Choke problem even more.

the 2nd pair of #041x heads
make more Peak TQ & HP and at higher points,
and don't lay over top end.

the #462 castings with 3 less CC's
make Peak TQ at same point, but past Peak HP point start to layover
more than the #041x

Fuel consumption is about identical

Same FlowBench CFM Numbers
but different Intake Port Pitot Probe profiles/velocities



note thats a 117.9 HP "LOSS" for the extreme hi-velocity Heads at 7600

yet..on a steady-state FlowBench test,
"BOTH" Heads flowed almost as exact CFM as you could possibly
make them be equal on both Intake + Exhaust sides.

even used and swapped the same exact Valves out of both Heads
for those tests

same #041x castings , both same Chamber+Port volumes


what i call the extreme velocity FPS #041x Heads were;

every possible portion of that Intake port that could have
Epoxy added to it, and that Flow CFM was not reduced at all,
was epoxied up.

and the rest of that Port was enlarged just enough
to hold the same Port Volume CC's

the Short Turn Apex speed was to the moon
and so was the pushrod area...and just about every where else in the
Port....the Floor had some "Ski-Jump" shape to it also...as it kept
the CFM Numbers up and the velocity sky-high

i guess you could call it an experiment to see how far
you could "shrink" certain CSA areas of a Port
and not reduce the FlowBench CFM numbers .

pretty evident from Fuel Consumed Numbers -vs- Dyno HP/TQ Numbers
that Intake Port could not handle that much speed FPS
without Choke or Separation

you can also see why just about everyone i know
will Run the #041x heads over the other Legal #462 castings,
those 3 more CC's can be used to "SLOW DOWN" the already
too fast FPS

one other thing that stood out in some of the Tests ,
was the very hi-velocity too fast FPS Heads that had a choke problem,
often liked "more" low to mid lift flow.
The engine's being fed sooner and more, so the cylinder depression is lesser until Choke occurs...and you still have good low-lift to take
advantage of high velocity at end of stroke

also the velocity FPS is slower
in the smallest CSA areas, in the low to mid lift portions of the Flow/Cam Lift Curve...pumping losses working thru rod angle leverage in early
and latter parts of stroke are going to be lesser than at Peak Piston CFM demand point where leverage is great and Choke makes more losses.

a Closed Intake Valve has "ZERO Port Velocity FPS"

at Max-Lift , typically the Cyl Head has its best FlowBench CFM Number
or about in that vicinity...so Port Velocity FPS is highest at Peak Lift or so.
as the valve starts to move towards max lift,
Port FPS is increasing...also the minimum csa area FPS is starting
to really increase or any too fast FPS area is also increasing in FPS
(add to that max Piston CFM demand in vicinity of 70-80 deg ATDC
and volume CCs increasing till BDC, + Flow Lag Times,
pumping losses working thru Rod Angle leverage/velocity, etc.)


FPS = (CFM * 2.4 ) / CSA

if Head Flows 127 CFM at .200" Lift = 156.6 fps @ 1.948 csa

if head flows 260 CFM at .700" Lift = 320.3 fps @ 1.948" CSA

but in reality there will be CSA spots in Heads that will be
smaller than 1.948 sqinches, so the FPS will be higher than 320.3
other CSA will be larger than 1.948
and other localized spots can have too high FPS
even though your Average CSA of 1.948 says its only 320.3 fps


the Port Volume is the same in both cases,
the FPS changes up or down inside the Port
in relation to the Lift/Flow Curve -vs- Piston CFM demand

picking up the Low to Mid lift flow in the too-fast-velocity heads
helped...but it still didn't run as fast down the DragStrip.
the best way i've found so far is to slow the FPS to as close
to reasonable speed as possible, as long as its not too slow,
take the choke CSA out of the picture as much as possible.


As I understand it, ports don't actually go into sonic choke at .55 Mach - but at this point (approx.) we reach the trade off where the energy required to move the air through the port becomes higher than the power increase (cylinder filling) that comes from higher velocity.
---SteveS

Note=> a lot of this stuff is on Darin's CD also
and SAE Papers in your College Library

[/QUOTE]

 

[hoffman900]

Jack, here is a simulated Mach Index trace of my combination at 7000rpm as taken at the valve throats.

Note the mach index on the intake side - right in line with our 7000rpm peak and approaching .55 Mach.

 

[hooser]

hoffman900, can you do the 540 #s at 8 to 8.5k with a 38mm, for every good one that is where we set them up. The 580 we do the 7k, thanks Gary

 

[hoffman900]

hoffman900, can you do the 540 #s at 8 to 8.5k with a 38mm, for every good one that is where we set them up. The 580 we do the 7k, thanks Gary

Keep in mind this is for my application only and my exhaust design.

There are many reasons why the TM-38 on my combination will peak lower than other, but the largest driver is going to be 'Choke flow' and it's a function of CFM vs. the MCSA (in this case 1.77in^2 ) and when the MCSA reaches and starts exceeding .55 mach.

Remember, FPS = (CFM * 2.4 ) / CSA