Meter head flow adjustment question??

[JBL930]

Sounds like you've got it stitched up mate, great fuel economy too with 450bhp. Is this type of set up straight forward for anyone, or does it take a lot of fiddling?
Can you let us know what happened with the Digi unit, you've obviously hit a brick wall with it?
Any pics of your frequency valve set up, i'd be interested to see the plumbing. You must be pleased to have it running so well and back out enjoying it, happy days, keep it shinny side up

[911st]

Originally Posted by stup

At wide open meter plate with injectors FITTED my car flowed between 120ml-124ml per 30 seconds(tested twice and results the same both times)..approx all within 3% at WOT...Copied that from earlier,,hope that helps...tested control pressure flow rate also and it was towards upper limit of specs 160-240ml per minute...i was at 220ml..that was the fuel line into the wur.

This is a very important data point!

Is there anyone that can convert this to how many HP a CIS fuel head can support.

[911st]

Is that per injector?

[beepbeep]

Regarding the intake: I believe 930 pancake will actually flow more uneven at boost than at low load. When mass flow/gas speed trough pancake is low, diameter and length doesn't interfere too much. But when you start boosting, cylinders with longest pipes will get less air than those in the middle due to flow beginning to saturate the pipes.

Further, WBO2 sensor will not be fooled by backpressure even if connected to air-injection holes. It's simply a matter of connecting a copper tube and letting the exhaust gases vent to atmosphere. So a theoretical "per-cylinder" WBO2 probe would be a coiled length of copper brake hose going trough WBO2 bung and then venting to air. Sure, it will produce a small leak of exhaust gases but as long as that leak is identical for all cylinders than you would have a repeatable condition.

[911st]

I would not think of a 930 manifold as pipes or tubes. It really dose not have any runners.

It is more like a pressurized vessel with 6 holes in it. Under boost it is the size of the hole or nozzle that determines flow.

[911st]

That sounds like a great system!

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I though we could compute the max HP the fuel head should support from the max deliver noted above.

OK, I am new to this so I may not have done it right but I will try.

240 ml/min = 14400 per hr =486.9 fluid Oz = 3.8 gallons = 31.54 lbs.

It takes .55 to .6 lbs per hour to make one HP.

Thus, 52.57 to 57.35 HP per cylinder or 315 to 344hp total.

What am I missing or what mistake did I make?

The stock fuel head has delivered much more Hp than that?

[911st]

I made a mistake on how much a gas weighs.

It should have been:

I had the weight per gal of gas wrong so I tried it again.

OK, I am new to this so I may not have done it right but I will try.

240 ml/min = 14400 per hr =486.9 fluid Oz = 3.8 gallons. 3.8 gal at 6.073 = 23.08 lbs.

It takes .55 to .6 lbs per hour to make one HP.

Thus, 41.82- 38.47 HP per cylinder or 250 to 230 hp total.

Something dose not add up here.

[beepbeep]

Hello!

I wrote it in your other thread but I will cross-post it here:

3.3L engine turning @ 5500 RPM at 0.7 bar, producing 300 HP at AFR 13.0:1 (CIS goes lean on the top, remember?) at 92% VE, 50 deg. C intake temp and 29% efficiency will gulp 33,7 lb/sec of air and have per cylinder fuel flow of 262cm^3/min assuming 0.75 kg/L density and 43.8MJ/kg energy density of gasoline.

As stup did the measurements in "N/A" mode, there was no boost enrichment present, so control pressure would be still high.

In order to determine flow at boost, one must pressurize the WUR to 0.7 bar in order to dump control pressure to 2-3 bar, which will raise the injector flow over 240ml/sec.

That value is still not accurate as injectors fight against 0.7 bar of boost, which will lower injected value by couple of %.

But all in all, CIS is capable of spraying enough fuel to obtain support around 350is HP in its unmodified form. More than that and you would need to fiddle with control/system pressures (and airflow also gets impended by flapper, which is the main HP bottleneck).

Regards,

[beepbeep]

Originally Posted by 911st

I would not think of a 930 manifold as pipes or tubes. It really dose not have any runners.

It is more like a pressurized vessel with 6 holes in it. Under boost it is the size of the hole or nozzle that determines flow.

I respectfully disagree. Middle "holes" are much shorter than "holes" going to outer cylinders.

A gentlemen on another forum has made a boxy plenum for his Porsche 928 in order to boost it with compressor. The "boxy" plenum has straight walls and huge cavities. Dyno-tests with stock 928 plenum vs. boxy-plenum in N/A mode revealed huge differences:







This makes me believe that a rework of OEM 930 plenum (which is suboptimal due to packaging constraints) plays major role in how much power you can extract from engine.

I'm always stumbled by how much power turbo-converted 3.2 Carrera guys get on mild boost from their otherwise similar engines. Some of that can be explained by EFI usage but I believe a good portion of that comes from better plenum.

[beepbeep]

Originally Posted by WERK-I

I was wondering about the SC 3.0 intake runners with a homemade plenum attached. They're equal length, easily obtainable. Do you know what the size of the primaries are? Larger, smaller than 3.3l intake runners?

I don't know the diameter of SC runners (I believe they are somewhat bigger?) but whole boxy SC plenum is somewhat of a boxy hack-job which works for N/A. I suspect that home made plenum would be just as boxy. Generally, I believe Carrera plenum is the way to go. But then you have port-hole mismatch scenario and less space for intercooler.

[spuggy]

Originally Posted by beepbeep

revealed huge differences:

That's an understatement...

Goran, could you post a link to that thread? Looks very interesting...

[stup]

Originally Posted by JBL930

Sounds like you've got it stitched up mate, great fuel economy too with 450bhp. Is this type of set up straight forward for anyone, or does it take a lot of fiddling?
Can you let us know what happened with the Digi unit, you've obviously hit a brick wall with it?
Any pics of your frequency valve set up, i'd be interested to see the plumbing. You must be pleased to have it running so well and back out enjoying it, happy days, keep it shinny side up

Set up aint too bad to fit,I mounted the main driver(control unit) behind my rear seats,behind the rear shelf lower covering where you cant see it,,the hardest part is probably routing the wiring harness from engine bay,through fire wall then under carpert towards centre consol where i have fitted the greddy controller/display but you would never know its there now its all installed.

Once all is confirmed with correct fuel delivery etc you would be surprised how little adjusting our cars need to acheive bang on fuel curve,,As my engine comes off vac if memory serves me correctly i then open injector 30% when its above 2200rpm then as the revs climb heading towards max torque its open 70% then nearing max revs its 85% and thats it....My fuel curve on boost is like a perfect straight line!...As with digiwur i had been involved help test/develope for a year but with summer approaching i needed my car running perfect so i could use it to full potential so went with my new system..

I will have to take some pictures and may start a fresh thread later on new set up when i get a chance.

Here is just a quick picture of afr graph i had taken from my laptop with my mobile phone.

Please note!......New Lamda sensor fitted...Zeitronix graph reads very accurate so from max boost low down,, AFR line only varies approx 0.2 AFR from then on!

[911st]

Originally Posted by beepbeep

Hello!

I wrote it in your other thread but I will cross-post it here:

3.3L engine turning @ 5500 RPM at 0.7 bar, producing 300 HP at AFR 13.0:1 (CIS goes lean on the top, remember?) at 92% VE, 50 deg. C intake temp and 29% efficiency will gulp 33,7 lb/sec of air and have per cylinder fuel flow of 262cm^3/min assuming 0.75 kg/L density and 43.8MJ/kg energy density of gasoline.

As stup did the measurements in "N/A" mode, there was no boost enrichment present, so control pressure would be still high.

In order to determine flow at boost, one must pressurize the WUR to 0.7 bar in order to dump control pressure to 2-3 bar, which will raise the injector flow over 240ml/sec.

That value is still not accurate as injectors fight against 0.7 bar of boost, which will lower injected value by couple of %.

But all in all, CIS is capable of spraying enough fuel to obtain support around 350is HP in its unmodified form. More than that and you would need to fiddle with control/system pressures (and airflow also gets impended by flapper, which is the main HP bottleneck).

Regards,

Not correct, he did not do the measurement in n/a mode. He did it by pushing the metering plate to full travel so the head was flowing at it's max.

The WUR and CP only effects the rate the metering plate moves relitive to air flow.

All the WUR's boost enrichment dose it lower control pressure to the metering arm can advance further for more fuel.

Pushing it down by hand bypasses the WUR function totally.

[911st]

Originally Posted by beepbeep

I respectfully disagree. Middle "holes" are much shorter than "holes" going to outer cylinders.

Looking at the graph from about 300hp to 400hp or a 100hp gain.

It is unlikely that just changing the volume and configuration of the manifold on a "turbo" car would account for such a gain.

Increases in efficiency can be found in changing runner lengths and make up like Porsche did with Varrioram with the 96 993 but that was on a normally aspirated motor. Turbos do not react the same way to intake phase tunning.

Something else seems to be at play here.

Still, I have seen reports of 930 owners having there manifold extrude honed. I have not ever seen a valid back to back where it was the only mod but it was felt at the time it may have added some HP like about 10 or so.

We have more flow potential for HP in just opening up the tiny ports. Look at any EFI turbo Porsche built. We come with 32mm ports (2.4 911T size) and the 993TT had 43mm ports.

[JFairman]

The "main HP bottleneck" as far as airflow restriction is probably the part of the origonal steel air downpipe where it's all crunched up as it squeezes by and around the left motor mount.

I doubt if a golfball would fit through it there.

[beepbeep]

Originally Posted by 911st

Not correct, he did not do the measurement in n/a mode. He did it by pushing the metering plate to full travel so the head was flowing at it's max.

The WUR and CP only effects the rate the metering plate moves relitive to air flow.

All the WUR's boost enrichment dose it lower control pressure to the metering arm can advance further for more fuel.

Pushing it down by hand bypasses the WUR function totally.

If that's the way it works then you're correct! If measurements are done by pushing the flapper all the way down then fuel limit are a bit on the low side. On the other hand, those dual pumps maybe don't get enough juice on battery alone...when engine is running you get 14.4V, battery alone gives around 12V.

But another poster mentioned this:

Looking at figure 17 in the Bosch K-Jetronic Technical Instruction I have, it looks like the Primary-pressure regulator has a Control-pressure connection on the opposite side of the plunger, to reduce system pressure as the control pressure increases.

Somebody who knows how boost enrichment works?

[beepbeep]

Originally Posted by 911st

Looking at the graph from about 300hp to 400hp or a 100hp gain.

You maybe mixed torque curves with power curves? He gained 50hp with OEM plenum. Look at "steep" curves, they are power curves. He hits 300hp with OEM plenum and 250hp with "boxed" plenum.

P.S. This is 928 V8.

[beepbeep]

Originally Posted by stup

I believe that's as good as it gets. Most aftermarket EFI systems have choppier AFR's on boost than yours. You've done great tuning job!

[JFairman]

Originally Posted by beepbeep

I believe that's as good as it gets. Most aftermarket EFI systems have choppier AFR's on boost than yours. You've done great tuning job!

Really... you'll put the DWUR guys out of business with your setup.
What frequency valve and controller did you use? Was it the Andial frequency valve or did you use the factory one that was part of the lambda system and a longer banjo bolt to mount it piggybacked to the control pressure line on the top center of the fuel distributor?

[WERK I]

Originally Posted by JFairman

Really... you'll put the DWUR guys out of business with your setup.
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I agree. Noting his previous post about using Greddy boost controller, Stu, are you using the Greddy eManage controller over a frequency valve to fine tune the AFR's?