Diskussion zu meiner Leistungskurve

[head_guy6]

2 graphs:-

cfm@24"on the vertical scale. Valve lift on the horizontal scale.

First one shows the (suprisingly) poor flow from the Spitfire INLET MANIFOLD.

2nd graph, the difference between a STD TR6 Pi early head flow & different modified heads, from normal road spec to outstandingly good race spec.

Then is a bit technical, but it shows clearly how the inlet manifold is a strong influence on valve flow.
Nota:- point 5 is 0.360" lift (9mm), point 6 is 0.432" (almost 11mm lift).

comparison between 4 & 6 cylinder flow rates.

The green line s719 is the MODIFIED inlet 6 cylinder manifold after much work. It's clearly much better than the "jcc3" line which is the 4 cylinder manifold which you CAN SEE THROUGH! (I mean literally see the port from the carburettor. But it doesn't flow!
Why it doesn't is a whole different game!)

The bottom RED line is the flow from a STANDARD brand new "big valve" Spitfire head.
Clearly no worries there, so the Mk3 & 1500 heads would flow even less!

The 814 blue line is the flow figures from a Spitfire head now found in Finland on a 1300 Herald.

Even before 9mm lift the head is OUTFLOWING the MODIFIED inlet manifold, never mind the SU carburettor.

This is an exceptionally good head because it would even outflow a modified 2.5S manifold, and is MUCH better than pretty much all the 6 cylinder heads in the world today.
It took many happy hours experimenting, to get Spitfire heads to work like this.
Not suprisingly they knock out quite easily in 100bhp/L territory as road cars.
Unfortunately, the guy running this head, is using a TR5 profile cam but an aftermarket twin choke DGV Weber conversion from the USA which flows even worse that the SU manifold, if that were possible. (!)





Comparison between STD and modified 6 cylinder flow rates:-

This is a little more complex, but we can still see the (s719) green 6 cyl manifold line.
This manifold was later fitted to a TVR, and a near identical one was used on the Vitesse 2.5L that knocked out 160-170bhp a few weeks ago....

The bottom blue line is the flow on the STANDARD head, (which is not much bettered by Triumphtune (moss) on their heads, & which only just underflow the STD LATE manifold (s721 line).

The engine tested a few weeks ago has the red line 769.
This clearly already outflows runner 1 pretty much all the way but would outflow runner 2 & 5 by about 30% if we hadn't sorted it all out.

The original head wouldn't outflow those defective runners.
Topmost on the graph is 785 which is an outstandingly GOOD TR6 head.

This head*** would start to outflow the inlet manifold by a wide margin from as little as 7mm lift.
If the valve hits 11mm lift, the head would be getting a serious detune from the inlet system never mind the carburettor!
Such an engine is optimal running on fuel injection.

NB:-
This sort of head*** would be the one we had to use to test the inlet manifolds tested here.




What is the conclusion?

If your engine torque drops off a cliff at 4000rpm, then it's highly likely to be:- FIRST the Stromberg inlet manifold to blame,
then the cylinder head as well as the combining factor the CAMSHAFT.

Using more valve lift and less duration ACTUALLY worsens the effect of the constriction in the inlet manifold & carburettor, and gives it less time to raise a draw at the needle.

Tut mir leid wegen technische deutsch...
ubersetzung bitte!!

[darock]

that is some serious data to think about

based on that information it is clear why the weber carb setups produce higher numbers. I am pretty sure that none of our (definitely also not mine) intake manifolds flow equally.

so we are back to the conclusion that the dual carb setup is the main cause of poor top end power.

which now really drives me to get the PI ITB EFI setup ready

braucht jemand eine Übersetzung?

Bernhard

[head_guy6]

that is some serious data to think about

based on that information it is clear why the weber carb setups produce higher numbers. I am pretty sure that none of our (definitely also not mine) intake manifolds flow equally.

so we are back to the conclusion that the dual carb setup is the main cause of poor top end power.

Not agree about the dual carb setup being bad.
It's a few hours work to make the inlet manifold work properly, just like it is to TIG weld up a weber manifold and make it FIT/MATCH the head properly.
(I always charge 300 Euro).

Jaguar 4.2L engines also work fantastic with twin HS8 SU carbs, and really not better with DCOE.

Lucas Injection is just MUCH MUCH better and always has been.

NO weber carb set up will ever rival the power output of a good Lucas Injection set up UNLESS the Pi has been set up to run at sea level, and you drive 1000+m up, or you insist on driving at extreme temperatures above 40C.

You can see the EFI cars have no better power output, and not neccessarily better driveability.

Below -15C the Lucas injection will also ALWAYS be better to drive than a DCOE carburettor, especially those Spanish ones!

(We have plenty of experience in Russia. We use, Either Downdraft carbs or fuel injection, - below -30C FORGET side draft carbs.)

[darock]

Do SU carbs flow better than ZS?

Do you have a picture of a ported and optimized late dual carb inlet manifold were the changes are clearly visible?
I will try to get a picture of mine on the weekend to compare.

Bernhard

[head_guy6]

I don't think so.
Btw:-
Stromberg nadeln sind von phosphor bronze.
SU nadeln sind von messing.

[Gerry57]

Hi Ihr,

Übersetzung wär nicht schlecht.

LG Gerry

[darock]

In Kurzform:

Die Doppelvergaser Ansaugbrücke benachteiligt aufgrund ihres Designs Zylinder 2 und 5 und man braucht einen speziellen Prüfstand um das zuverlässig beheben zu können.

Die ZS bzw SU Vergaser am 2.5l schaffen angeblich maximal 160 PS

Was bei mir bei 4500 den Hahn zu macht ist immer noch nicht 100% klar ... Es könnte eine Kombination aus dem Problem mit der Ansaugbrücke und der Nockenwelle sein, die eher weniger für höhere Drehzahlen geeignet ist.

Bernhard

[V8]

:so we are back to the conclusion that the dual carb setup is the main cause of poor top end power.

which now really drives me to get the PI ITB EFI setup ready

Die waren ja damals nicht dumm.
Wenn man besser und vielleicht billiger
an Leistung kommen könnte,
als mit der der PI-Anlage und Zubehör
hatten die Triumph Leute das sicher gemacht.

Wenn man heute noch höher hinaus will
muss man mindestens mal auf dem Niveau einsteigen.
Das heißt aber auch 280er Cam, die Triumph ja nicht freiwillig
aufgegeben hat und was ja irgendwo 20 PS gekostet hat.
Was nämlich noch keiner hier erwähnt hat sind die kurzen Pleuel.
Einfach gesagt mindern die die Wirksamkeit der Überschneidung
und damit die Schärfe der Nockenwelle
und damit das Drehvermögen des Motors.

Also der TR geht aktuell mit der 280er Bastuck ab 1200Upm Vollgas ohne stottern
und man kann ab 1000Upm im Vierten bequem cruisen....
Einzig das schlechte Abgas würde ich als Gegenargument gelten lassen.
Das Auto läuft in der Konfiguration perfekt und absolut empfehlenswert.

[Pioniergeister]

der Grund für den optisch etwas versteckten Abgang der Zyl. 2 und 5 könnte darin zu suchen sein, das die schwereren Benzinanteile im Gemisch in den Kurven das bestreben haben gerade aus zu fliegen
dann würden die beiden mittigen Zylinder anfetten

Ein Bild von meinem bearbeiteten Ansaugkrümmer - hatte damals schon was gebracht

Jetzt ist eine 3-fach eingebaut, mit 280er Newman
dreht willig bis 5500, muss er aber so gut wie nie - vielleicht mal im 3.Gang

Grüsse
Alois

[V8]

der Grund für den optisch etwas versteckten Abgang der Zyl. 2 und 5 könnte darin zu suchen sein, das die schwereren Benzinanteile im Gemisch in den Kurven das bestreben haben gerade aus zu fliegen
dann würden die beiden mittigen Zylinder anfetten

Hallo Alois,
genau so sehe ich das auch: Der Sprit kommt in drei Phasen zum Brennraum. Gas, Tröpfchen und Film an den Wänden.

Der Erfinder der Zentrifuge oder Mr Dyson hat sich schon was gedacht.
Der Effekt ist da und wenn nur der "flow" kontrolliert wird hast Du noch keine Aussage über die Gemischqualität.

Deswegen geht der begeisterte Kellertuner den einfachsten Weg und gibt jedem Zylinder sein eigenes Ansaugrohr mit eigener Spritdüse nah am Ventil und eigener Drosselklappe. Da kann jeder machen was er will und keiner stört den Anderen und nimmt ihm was weg!

Nicht umsonst macht das heute fast jeder Motorenbauer. Früher als der (zusätzliche) Vergaser noch viel Geld gekostet hat und zudem eingestellt werden mußte hatte die Rohrstrickerei noch Sinn, heute ist das nur für Originalliebhaber erstrebenswert.

[head_guy6]

der Grund für den optisch etwas versteckten Abgang der Zyl. 2 und 5 könnte darin zu suchen sein,

.. Sprit kommt in drei Phasen zum Brennraum. Gas, Tröpfchen und Film an den Wänden..

So viel einfacher ist es.
Laminar flow und turbulenz.

We fight 2 contradictory ideals (larger area with circular flow) and larger constriction with laminar flow.

Here in the SU carb manfold it is essential to get the balance just perfect.

too big in throat NO FLOW.
Too small NO FLOW.

[V8]

Here in the SU carb manfold it is essential to get the balance just perfect.

I am right with you that, if it is as pointed out, you did a good job on the SU Manifold.
Also I agree that it is better to look on the equal flow of all cylinders first.

But the question for me is:

If I can read clearly in the booklet of Kastner that he achieved a gain of 20 pretty horses with the swap from SU to PI on a modified engine and also a huge increase at lower revs
and can also look in my cellar where instead of a nice flow bench three PI manifolds are looking at me

why should I stay with the SU manifolds which need work I can not do by myself with prooven results
when I can get more power, more economy, better idle and better part throttle behavior with just the swap of the manifolds?

By the way: In the booklet is a change on a modified engine from the stock cam to the S-2 cam which is similar to 280 sportscam prooven with a huge gain of 30 horses.
This brings us back to the topic here of the engine rubber band at higher revs. That points out my feeling that all must be matched together and in a modifed TR6 engine a 260 degreee cam is more or less a tribute to the idle of the SU carb than a perfect choice for the project.

[head_guy6]

Here in the SU carb manfold it is essential to get the balance just perfect.

I agree that it is better to look on the equal flow of all cylinders first.

If I can read clearly in the booklet of Kastner that he achieved a gain of 20 pretty horses with the swap from SU to PI on a modified engine and also a huge increase at lower revs

why should I stay with the SU manifolds which need work I can not do by myself with proven results

when I can get more power, more economy, better idle and better part throttle behavior with just the swap of the manifolds?

By the way: In the booklet is a change on a modified engine from the stock cam to the S-2 cam which is similar to 280 sportscam proven with a huge gain of 30 horses..

Forget Kastner.
Those "S" whatever cams don't work, and you are comparing a 280 degree modified cam with the total crap USA TR250/TR6 cam
timing 10-50 50-10 which runs at a CR of 7.75:1!
This is not science it's just comparing apples with oranges.

We have MUCH better cam designs in Europe for 30-40 years now, even the CP camshaft they did not have in the USA.

As for the power output using the later manifold and SU carbs.

I have several documented cases where the engine with 2 x SU carbs gives BETTER power than the STD TR5 CP original engine with injection.
(using a 6-3-1 manifold).
Recently we tested a 2.5L engine with CP cam +one of my heads & those 2 SU carbs.
It gave just under 170bhp, beautiful idle, low emissions & low wear rates.

(He brought in a TL DEAN head btw in exchange, which was SCRAP,so had to have a head non exchange. The engine had been built at XRN and lasted about 200miles before falling to bits, with pistons hitting the head etc etc etc..)


This is how it works.
You raise the inlet flow from 65cfm to around 76cfm at 9mm maximum valve lift, by flowing the head with some nice valves + convert to lead free at same time
(the inlet manifold will flow 80cfm quite easily on all runners. That is more than most people are capable of getting out of flowing a head PARTICULARLY Moss/Triumphtune).

This gives approx +10cfm per inlet valve which you divide by 2.2 to get bhp per cylinder...(say 4bhp per cylinder more).

You raise the compression ratio to compensate for the restriction caused by the carburettors. Say 10.4:1.
As there are 6 cylinders this yields about 24bhp.
From a well built 143ps motor you get about 165.

As the exhaust valves flow a lot more early in the exhaust cycle and get a much bigger improvement by flowing the ports properly+you get a 30% increase in exhaust flow at max valve lift, and as much as DOUBLE just as the exhaust valve comes off the seat.*
This gives you the TOP END performance extending to a good 5500rpm +

This is called "TUNING UP" an engine, not detuning it by fitting a camshaft of only 260 duration.

What more do you want?

This is scientific,-
....
it's not some sort of haphazard Kas Kastner, try this or try that "I bolted this on" and it gave me (maybe) 20(USA) bhp stuff.
Thats all "old hat".
It was OK for 1967, but it's not for 2007 or even the 21st century.

Nota:- TBQH
I never got over Kastner's endorsement in his book, of that amazing bodger T -L Dean who has cost me more replacement non exchange heads than I care to think about.
Yet Kastner wrote for ever in a book, how good that idiot is, and everyone believes it, because some old crusty who should have retired 20 yrs ago, WROTE IT!

(T L Dean heads are always ruined.
He ground out inlet ports to some crazy over-size, and I can't put material back where he had removed it, & he has ruined loads of them!
One of them even ruined a perfectly good engine of mine!)

Theory WORKS in practice, because it enables you to understand EXACTLY what is going on and why.

*What most people cannot understand is,- more valve flow is EXACTLY the same effect as increasing cam duration, as the valves flow a LOT more a lot earlier.

I made a great effort to make my exhaust manifold fit with this carburettor inlet manifold, and it gives effortless torque even with the mild factory cam.
That operation alone took 18 months of a great deal of effort carefully checking and making an exhaust Jig (at my expense) and bringing in several cars to cross check for fit, inc a TR6 pi RHD, a Vitesse 2L & a TVR 2500.

I'm not here to advertise.
I just do stuff which works
+
It has to be able to last 10 year's driving without falling apart.

[V8]

Nice reply, thanks a lot for detailed informations.
They are interesting although I do not agree
with every detail (what seems to be not necessary)

What I do not understand is why you stick with the carb system?
It seems to be your favourite subject but
with no doubt at some other places you agree
that a well done engine improves from individual runners.
Also every racer uses PI if allowed or 6 carbs.

Besides the static output of power of the engine
at certain revs there is still the question of dynamic.
If you lift throttle due to street/car requirements
the carbs can not deliver full power soon after
because they will need a small time to reopen the venturis.

[head_guy6]

Nice reply, thanks a lot for detailed informations.

What I do not understand is why you stick with the carb system?
.

Because that is what people keep wanting me to fit, despite me telling them it's better on Pi.

Customer is always right and all that. Remember?