Dear Jim

When I look the very small injector outpout hole and compare it to the size of the metering slits, I really suspect the injectors to be much more restrictive. it doesn't means that the metering slit are not restrictive at all. There is certainly a little margin which can be used in order to increase fuel flow under middle and full metering deviation. I speak about middle deviation, because in your in valuable expérience it is possible that the tuner have increased the slits on the bottom direction which could cause too much fuel at 4000 RPM but which doesn't means you could get tons more fuel at full deviation of the metering arm.

When I see the tons of fuel that the head is able to supply when the injectors are removed ( as Stu did in his matching thread) it makes no doubt to me the injectors are huge part of the equation.

The 3.6T and 3.3T are using exactly the same head distributor. The arm is the same, the metering slits and pins are the same, the valves are the same, the input and output line are the same, same fuel pumps too, but the control pressure is about 0.4 bar higher on 3.6T while the metering cone is a bit larger........ where do you think they get more fuel ? ;)

Maybe the K-jetronic ECU is programmed differently in the 964 turbo to make the lambda valve bleed off more lower chamber pressure at large throttle switch positions. That would send more fuel to the injectors.

I don't know as I've never even seen a 964 turbo up close and don't know what all the subtle differences are in state of tune.

I remember someone posting pics of the 964 turbo and 930 fuel system specs from a book and I remember they were all the same accept for boost control pressure and I don't know where that post was and I think I remember reading it the other way around - I thought I read that the 964 turbo WUR was set to lower boost CP than the 930 one.
If it was thats probably where the extra fuel is coming from under boost.

I have no idea what thread that was in and don't feel like trying to find it right now.

I think area of the slits are not directly what determis fuel flow.

That is, how much that flows through the slits is not equal to the flows to the injectors.

The slits effect the "differential pressure " between the upper and lower chambers. Increasing the differential pressure is like loosening the spring tension in a fuel pressure reg and effects how much the regulator membrane can distort and thus how much fuel passes.

I t makes sense the injector would act to restrict to some level.

Thus, making it larger could increase flow.

The main function of the injector in a CIS is probably to maximize atomization.

With that comes pressure build up, any increase in pressure indicates restriction.

We can overcome that restriction by increasing pressure or by reducing the restriction.


I truly do to know if the injector is "the" restriction. I very much look forward to seeing results of testing.



The rest of this is just educated guessing among friends.

qoute-

"but the control pressure is about 0.4 bar higher on 3.6T while the metering cone is a bit larger......."

Thierry,,,,my data qoutes the control pressure on the 964t 3.3 and the 964t 3.6
to be the exact same on both models! 4.5bar +- 0.2

Keith, if this were true, all of our turbo engines would go rich at max rpm, not lean.
Also, the compressor is sucking double the air across the metering plate than a n/a engine does.

That's true that if you are not familiar to 964T, it a bit difficult for you to follow me. ( As it is sometime difficult for me to follow you on 930 territory ;) ).

To be honnest with you I have the full original Porsche workshop files on my hand. ( both 3.3T and 3.6T)

The 3.3 T kjet ECU supply the same stable 50% duty cycle at WOT to the freq valve ( which is the same as 3.3T). There is absolutely no lambda regulation at WOT.

Fuell pressure system is the same ( 6.1 to 6.8) The warm control pressure is the same 4.5 b . On boost, the control pressure is 1.1 bar shifted on the 3.6T while it is 1.3 shifted on 3.3 T ( Sorry I made mistake it is not 0.4bar less but 0.2 bar only )

By the way, while I tuned my KJET-BOOST controller system on my car . With the stock pumps (before to switch to 044 front fuel pump) , I made the test to trigger the lambda freq valves at stable 75% duty cycle on all RPM. As you can see on the following curve, it brings a lot of fuel ( the car almost stalled) in the mid rpm)....but it doesn't bring same fuel increase at high rpm

http://img697.imageshack.us/img697/6...mbdatrig75.jpg

Sorry, I made mistake a said before. :(

The warm control pressure is 4.5 bar on both 3.3 T and 3.6 T

But the control pressure on boost (300 mb) is lowered by 1.1 bar on 3.6T and 1.3 bar on 3.3T. Thus the boost control pressure is 0.2 bar higher on 3.6T ...

Paul,

Sorry, the key word is 'ultimate'. Yes we are more fuel limited at this time.

I think we can get a lot more fuel out of your CIS systems as they are just mechanical devices. Heck, we could have a HF head built on a V8 core that supplies 33% more than the biggest HF FD we could conceive.

However, I think the tube out of the metering assembly is only about 3" or so. (Dose anyone know the actual size?) Most the turbo's that make over 500hp have 4" inlets.

One way around this would be to convert to a blow through system and having the inter cooler exit hook to the top of the metering assembly and the metering exit to the throttle body. This would remove all restriction from the turbo inducer side (reducing lag) and at 1 bar double air flow we can get through the metering system. (Think 3.2 Carrera blow through turbo conversion making 475whp through a small little AFM opening). The plumbing would be easy with a custom IC. However, it would probably take a lot of work to then get the fueling right.

Crazy, I know.

This is what I thought. CP on boost is lower for the 3.6 than the 3.3. This would give the 3.6 more fuel on boost.

Thierry,

Did you ever test the factory FV at 75% with the increased pump capacity?

Increasing the Lambda FV capacity I think is like making the slits bigger. There may be a limit to how much differential pressure we can generate or how much we can get past the internal orifices. That is find a way to create a higher differential than the Lambda heads can alow. Maybe a more complaint membrane, a larger "unsupported circle on the bottom head section", and or more spring tension around the internal orifice.

The US Lambda head was designed to allow a higher pressure differential than the non which might be its key to supplying more fuel as a HF head than the others.

If that is the case, a larger orifice and or higher system pressure might be our path to more fuel.

---

JF,

I think the main difference between the 930 and 964 Lambda system is the 964 has a provision for acceleration fuel for a short time after start up when at low temp. There is also a relife function built into the 964 head to keep vaccum from building up behind the control pin after shut down and cool off that I do not know if the 930 received. Could be the 930 got both these but I am not sure.

The real difference was on the ignition side.

qoute- However, I think the tube out of the metering assembly is only about 3" or so. (Dose anyone know the actual size?) Most the turbo's that make over 500hp have 4" inlets.

I have spare 964t one on my bench and i am pretty sure by memory it appears more than 3" inches.......in fact even though its about -10 below freeeezing just now here in scotland its bugging me and i will check!!

Gee!
That is restrictive and unfortunately has quite a thin wall,,so not much chance of opening up in size(inside dimensions)

2.85" approx (72.5mm approx)

Your sentence allow me to explain my idea about the full behaviour.;)

Actually, I think it is wrong to think the intake air flow increase considerably at high RPM.
Actually past the max TQ band , we can see the torque is dropping dramatically. This drop tell us directly that barrel filling becomes very poor. ( due to the cams, turbo, intake and exhaust limit...). Somewhere step by step, air can not go in and exhaust gas can not go out.

So past the max TQ band, the flow is mathematically increased by RPM but is decrease by filling efficiency. So I think the air flow doesn't increase so much .

Then be back to the so called Kjet behaviour (stock), I think the max fuel capacity of the Kjet is already achieved at little above max TQ band. Past this point the air flow increase slowly but as the flowed fuel is already at it max, the AFR is increasing step by step either.

Then when we switch to more agressive cams, we never get any problem with mid RPM ( since the kjet is self tuning ) but past it fuel capacity we hit the limit in sharper way. No matter higher or a bit lower RPM is ....

Dropping the pressure control doesn't change anything... the metering plate is fully moved ( or very nearly).

Acting the lambda freq valve doesn't change anything either...For max capacity it is even much better to turn it off and to increase the valves adjs. screws. ( Remember this FV returns an important amount of fuel to the tank)

Increase the fuel system pressure ( by shimming the head) bring almost nothing it self.


....

Sorry keith but no !

3.6T on boost CP = 3.4 bars ( 4.5- 1.1)

3.3T on boost CP= 3.2 bars (4.5 -1.3)


So CP on boost is higher on 3.6T !

I have both Porsche doc in my hands right now...

Thank you much!

Our cars seem to respond well to about a 60mm inducer. That is about 2.4". Most turbo of that size have and a minimum a 2.75" tube connection on them.

I suspect at some point we are asking the turbo to not only compress air but to suck it through the upstream restriction. Thus, boost on on side of the compressor wheel and vaccum on the other.

If someone could figure a way to put a vac gauge on that section and check it at peak HP it would probably yeald some very interesting results.

With this happening it should reduce the efficiency of the turbo significantly at some point.

Thus, the compressor maps for most turbos are not going to be very accurate in our situation.

Thanks for the correction on the CP for the 3.3 & 3.6 heads.


I like your thoughts on where gross air flow is.

Peak TQ is where the motor is running at its most efficient level.

Peak HP is where it is probably using its max air and fuel.

The metering plate moves quickly at first with changes in air flow. Partially to the ratio of the arm to the metering pin but mostly due to the shape of the metering cone.

As we get to higher air flows, the metering plate dose start to slow as air starts finding a more direct path off the end of the metering plate and the plate extends past the metering assembly exit. I say it stalls but to say it slows is probably more accurate.

There is about one full point of added fuel available by reducing CP below stock. This has been the corner stock of the Andial WUR sense the beginning. I believe after about 1.9 bar there is nothing to be gained.


So, after we hit peak HP and air flows fall off, do we want the fuel level to fall off to or do we want to maintain our goal AFR.

If we can get the metering function to compensate for changes in air flow accurately at our expanded air flows it will be self compensating.

Maybe the key is lower restriction injectors and a larger metering cone to a degree.

At some point increasing the flow of the FD is needed but we need to do so in relation to changes in air flow.

Here is a lead on the Gold CIS injector: http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/453683-cis-monster-16.html#post5144489

My guess is they are nothing more than a Porsche 930 injector in a Volvo body.

It looks like a 930 injector might be flowing about 500cc/min at about 6.4 bar.

However, the Gold Volvo Race injector seems to flow 600+ at 8 bar!

It looks like it takes about 600cc under boost to support 100hp.

If we make about 3000cc/ min we might have enough fuel in a stock head for up to 500fwhp if we can keep the air sensor plate from stalling. (another belief of mine).


I am believing the injector is a way to increase fuel.

However, so is a much higher system pressures than we are running as long as we have the fuel pumps to support it.

Thus, the 1994 3.6 Turbo CIS injector might be the king of injectors.

It would be interesting to test a 3.3T against the 3.6T injector at stock System Pressure and see how much of an advantage it might yield.

Fun stuff.

OEM CIS injector capacities aren't an issue. They allow MUCH more fuel than required - with the IA fuel head & the Leask setup I can adjust the control pressure to allow tons more fuel than required....much more than required, top to bottom, for my 514HP 930.

Craig, part of the reason the injector question keeps coming up is because in some cases there may not be enough flow, and switching injectors would be easier than modifying the fuel head. For example, I have an SC CIS which is not flowing enough for my supercharge addition. If other injectors did the trick, then I'd be set. Otherwise, I have to modify my fuel head or get another one from a 930. Looks like you've got a great fuel setup and the HP to boot.

Given the dearth of CIS injector flow volumes, it's worthwhile to add data points on this whenever possible.

Very doubtful, actually -- for a 930. I'd just like to help others not chase down different injectors for a 930 when not needed.
I ought to dig up my flow video and my numbers - they allow HUGE amounts of fuel.

A modified fuel head provides a shedload of fuel,; I am at 1 bar and I use the Leask device to significantly dial back the fuel.
I'd bank on being able to run 1.2 bar and have plenty; at one time I adjusted things to 1.1 bar and still a TON of fuel available.

+1 Craig, it's in the fuel head. The injectors have no metering function, They operate at a constant pressure. The needle valve in the injector vibrates at different rates as the flow changes thus maintaining the constant system pressure. In other words if you can't get the flow through the fuel head don't expect more through different injectors.