Information about the 934 CIS Injection

[911nut]

Originally Posted by WinRice

Out of curiosity, what system pressures have you tried, and what do you run now?

6.7 bar was a no-go for reasons stated above. Currently running 6.1 bar and the engine likes it.

[stup]

Quote de JFairman

I know hydraulic control pressure and lower chamber pressure have nothing to with each other and are isolated from steady system pressure by small fuel orifices but hydraulic control pressure fuel pushing down on the top of the control plunger will go up at the same time fuel system pressure is raised so the control pressure regulator will have to be adjusted to return more fuel to the tank to lower hydraulic control pressure.. if you want more fuel from the injectors.

I ran across this issue when tuning my CIS last year. I increased the system pressure to max but no changing of boost control pressure would allow the system to run in the sweet spot of 11.0 - 12.2 afr. It was pig rich all the time. My engine is stock so I couldn't use the extra fuel. When I dropped the control pressure to minimum spec all was well and now runs like a raped ape.

Great thread and has got me interested.
Once you flow balance all fuel to each cylinder in my opinion there is no need to go as rich as 11.0 Afr,the sweet spot is a bit leaner than that.My +400 whp 3.3 turbo barely sees below 12.0afr through midrange,maybe at lowest 11.8 through midrange and pulls cleaner/harder at those settings and has done for the last 2 years plus after several years of fine tuning and comparing results on mine and many several other 930 I have tuned.
Some excellent info coming through from this thread,keep it up ;-)
I am still a total believer in retaining cis on our vehicles if set up/tuned correctly as the engines can run perfectly with no real negatives if you plan to stay below 450 whp or maybe a bit more hp as threads like this maybe prove to us.

[stup]

With all camera tech available nowadays and also editing software etc it would be a really interesting to see if someone could install a small bullet camera in top the air box above the metering plate and capture its movement in different shaped variations( cones etc) and log it along with obviously AFR ,boost rpm etc to see the effect airflow has on top and underneath it..just thinking out loud and this will prob never happen but it would be cool to see

[JFairman]

Originally Posted by stup

With all camera tech available nowadays and also editing software etc it would be a really interesting to see if someone could install a small bullet camera in top the air box above the metering plate and capture its movement in different shaped variations( cones etc) and log it along with obviously AFR ,boost rpm etc to see the effect airflow has on top and underneath it..just thinking out loud and this will prob never happen but it would be cool to see

I've thought about that and never done it but you could do it with just about any small pocket point and shoot digital camera with macro and video functions, and that's probably all of them these days.

With no air cleaner in place you'd mount the camera at a slight angle above the CIS air flow meter somewhow and also a 12 volt light or flashlight lighting it up. A small tripod with adustable leg angles and some bungee cords and duct tape to hold it and the light in place would probably do it.

Then start the video recording, get in and drive the car. The sound of the motor on the video would help you estimate throttle position, boost, and rpms from previous experience during playback.

[911nut]

Originally Posted by stup

Once you flow balance all fuel to each cylinder in my opinion there is no need to go as rich as 11.0 Afr,the sweet spot is a bit leaner than that.My +400 whp 3.3 turbo barely sees below 12.0afr through midrange,maybe at lowest 11.8 through midrange and pulls cleaner/harder at those settings and has done for the last 2 years plus after several years of fine tuning and comparing results on mine and many several other 930 I have tuned.

I played around with my mixture last fall. I first tried 12.0 afr at 3000 rpm, ending up at 12.8 at 6000 rpm. Just for fun (and on the advice of an old engine calibrator that I work with) went to 11.5 at 3000 rpm, finishing up at 12.3 at 6000 rpm.
The car reaches 6000 rpm at little faster at the richer setting according to the data but it also seemed faster from a butt dyno perspective, so I would agree with you, Stu.

[Grupp-A]

Here is a flow chart of Bosch CIS fuel distributors and all 911/930 distributors are listed. I guess the flow rate must be the factory setting from Bosch.









Cole:

Do you have the 037 model?
Do a flow test. It´s very easy especially for you with your flexible fuel hoses and you don´t have to include the injectors, just put the hoses only in bottles, start your pumps and push the air flow meter down for 60 sec and then measure.

Fuel req. per injector:

6 cyl 300 bhp fuel req. 250cc +/- 10% = 225-275cc/min/cyl

6 cyl 350 bhp fuel req. 292cc +/- 10% = 263-321cc/min/cyl

Daniel

[Grupp-A]

Cole:

No I don´t have any info about the metering plate cone but I can ask a guy at a Swedish forum, I will return with an answer.

Daniel

[stup]

Quote de stup

Once you flow balance all fuel to each cylinder in my opinion there is no need to go as rich as 11.0 Afr,the sweet spot is a bit leaner than that.My +400 whp 3.3 turbo barely sees below 12.0afr through midrange,maybe at lowest 11.8 through midrange and pulls cleaner/harder at those settings and has done for the last 2 years plus after several years of fine tuning and comparing results on mine and many several other 930 I have tuned.

I played around with my mixture last fall. I first tried 12.0 afr at 3000 rpm, ending up at 12.8 at 6000 rpm. Just for fun (and on the advice of an old engine calibrator that I work with) went to 11.5 at 3000 rpm, finishing up at 12.3 at 6000 rpm.

The car reaches 6000 rpm at little faster at the richer setting according to the data but it also seemed faster from a butt dyno perspective, so I would agree with you, Stu.

Pretty good acheiving those figures,way better afr than what it came with from factory.good going mate ;-)

[Helmsy]

I had these pics saved and was told it from a 934 style race car. They could be wrong but either way it looks quite different from a 930 air meter assembly.

[Grupp-A]

The secret is revealed!!!

Daniel

[Grupp-A]

Cole:

You gotta see this!!!

Daniel

[cole930]

Stu & Paul:

Great to have you two jumping in here !!!!! Great stuff your posting, it
gives us some real world numbers to compare to.

Ben:

That has to be off one of the race cars that Daniel has refereed to that
used the factory race CIS. Really an interesting metering plate cone on
that one, and defiantly one we have never seen before.

Daniel:

Man, your blowing my mind here, what a fantastic wealth of information.
Can't thank you enough this stuff is priceless !!!!!

My car is an 80 ROW 930 and it does have the 037 fuel head. I am 2-3
weeks away from pouring fuel in and starting to dial in some settings,
makes all this very timely. I'm going to be installing the new adjustable
WUR also. Once I get That done I'll see what the flows look like and get
them dialed in. Can't thank you enough for all the help.

I'll be looking forward to hearing what the next big surprise is !!!!!!



Cole

[Thierry25]

Originally Posted by stup

Once you flow balance all fuel to each cylinder in my opinion there is no need to go as rich as 11.0 Afr

Hello Stup !

100% agree with you !

Here is measurement example with fat mid ( stock CIS behaviour ) VS correct AFR (with my CIS controller ).... The torque difference is clearly visible.



The engine is much less responsive with too fat AFR.

[smurfbus]

Stup and Thierry: So you guys don't worry about the middle cylinders possibly getting more air and if fuel is the same they would be leaner. I wish someone would measure the AF at the headers.

[Thierry25]

Originally Posted by smurfbus

Stup and Thierry: So you guys don't worry about the middle cylinders possibly getting more air and if fuel is the same they would be leaner. I wish someone would measure the AF at the headers.

Hello Smurf

How many % do you estimate the difference between middle and external cylinders ?

As you said, no one has made the real AF measurement at each output ? So how can you believe there is a strong difference between middle and external ?

[stup]

Hi guys!!
Good to be back posting on interesting threads like this one with fellow enthusiasts;-)
I have not measured afr or egt's at each individual cylinder,measured injected fuel though to each individual cylinder on partial and full throttle and got this to less than 2% difference between all 6 cylinders after some adjustments via meter head...what I can confirm though is I removed my headers last year and the colouring of each individual header port looked the exact same and perfect colour,it just so happens I am removing my headers again tommorow to fix oil return tube leaks so I will try take picture to show the even colouring on each port,with this evidence I would then presume the air flow in each cylinder can't be that far out and must be pretty even

[911nut]

Originally Posted by smurfbus

So you guys don't worry about the middle cylinders possibly getting more air and if fuel is the same they would be leaner. I wish someone would measure the AF at the headers.

We hear lots of anecdotal evidence of that being the case but I've never seen any data to suggest it. Someone would have to have a wide band O2 sensor on each cylinder to verify this.
The assumption is that the middle cylinders would get more air because the intake path is shorter. That would only be the case of all intake valves on all cylinders were open at the same time, which obviously, they are not. I'm sure the flow under running conditions is more complex that I have just portrayed it to be so the truth might lie somewhere in between the two models.

[smurfbus]

I have asked about the stock 930 IM flow before with no replys and I haven't found any info over other sites either.
Stock 930 IM flow numbers?

I'm not saying 930IM flows unequal but carrera manifold seems to. It's a bit strange that there is no real info available about this even after 35yrs! It's true that boosted IM kind of softens the impact of flow test numbers.

Chris (tk) said he had asked for the 930 flowcharts from EH but could not get any. That 'could' imply that there was not much delta between the ports either?

Here are some flowcomparisons for the carrera IM:
extrude hone is it worth it????

Copy paste below from that thread.
****************
Here's some real data for you, rather then a bunch of opinions and theories:

Before and After CFM on my 3.2L plenums:

#1 - 197/322 +125 CFM gain
#2 - 313/335 +22 CFM gain
#3 - 227/331 +104 CFM gain
#4 - 197/348 +151 CFM gain
#5 - 313/339 +26 CFM gain
#6 - 233/335 +102 CFM gain

********************

1 257.1 290.3
2 253.2 298.4
3 250.9 297.7
4 264.7 294.6
5 250.4 300.6
6 260.8 297.1

[vas930]

Sorry this has taken so long, Cole.
The dang thing just wont let me post the file.
So I have taken some pics.
This is out of a gen factory 934 man.






Not sure if this is of any help.

Cole, I can get you a copy of the factory info if you want.
A good friend of mine has a set.
He wont let them out of his hands, but I can get a photo copy for you.
Let me know if you want them.

[cole930]

On my build thread we were discussing Jeff's comments about
more air and the issues with insufficient air flow with the stock air
cleaner. We started looking at the original 934 air intakes and
discussing what we thought the theory was behind their design.

Marty / Copbait, who is a real turbo guru, mentioned he also
had a lot of interest in air flow, blowers and fans. He graciously
offered his learned opinion on the best properties for optimum air
flow. His explanation and comments lent credence to what was
actually used on the 934's and why. He also expounded on what
would work best if applied. This is what Marty Posted.


Cole-

"The plate weighs air mass flow.

What I see is basic optimizing of inlet conditions into the metering plate/orifice to eliminate turbulance. Turbulence in this location at higher mass flow could prevent proper metering. A bell-mouth flow nozzle and straight section of tubing (ideally one diameter in height) will accomplish this. Think velocity stack but stubby. (This is not what Brian has with his filter swap.) Probably could find one sold for a four barrel carb.

Looks to be a flow nozzle under the screen in the dirty engine 934 shot. You are not tuning a pulse, you are simply allowing the air inlet to pull in all that is possible and present a uniform column of air to the plate.

Why it is not done on the factory installation? Probably is more about packaging considerations (no room for an ideal situation). These compromises happen all the time. Plus this is a problem outside the normal operating range at their design power level.

Wouldn't mess with attempting turning vanes. One idea discussed
is a definite NO-NO. Never place guide vanes in the inlet of these turbo-compressors. The eddy currents they produce excite the inlet blades and can cause blade separation in very quick order."



I purchased the pieces to replicate an original style 934 air intake.

934 Air Intake





Material to fabricate 934 Air Intake




The Optimum Air venturi




Any input, comments, or suggestions welcomed.

Cole