AFR tuning and intro

[930martini]

Hi Pelicans
I am a long time lurker and big admirer of the competence and knowledge of this forum.
I have rebuilt my 930 from the ground up in recent years and I am getting close to finishing it. The engine is mildly modified with ported heads, SC cams, GT-35, Ruf intercooler but is otherwise pretty stock.
I have hooked up a Zeitronics ZT-2 to compare AFR with boost and RPM. I did dial in the CIS pressures with a gauge and I did a couple of runs to see where I am at. In the chart below you can see the usual boost dump down to an AFR of around 10.0.
My question is if I should further fiddle with the WUR or go straight away and install an rpm switch? Cruise is around 13.5 and is maybe a little rich.
Thanks Marco

[patina]

Install RPM switch asap. Total game changer.

[Alan L]

Yes the boost dump is always a DUMP. You may finally get it tweeked to something a bit less rich when you get a final tune in it. But the switch helps more than anything else you can do.
Alan

[930martini]

Thanks for the replies! My question is if I install the switch and have the dump activated at around 4800RPM where will be the AFR's from lets say 3000 up to 4800? Will they stay at over 13?

[Alan L]

It will depend on your tuning, but in general terms it will keep leaning out, until the switch opens. The leaner you run it before the dump, the smaller the AFR drop at the dump. That also then depends on how big a dump (in Warm Pressure) you set in the WUR. But at around 0.5 bar dump, I let it get up to around 12.5 before the switch opens. Typically this would be around 4600 rpm. I am usually running a dump between 0.5 and 0.3 bar. So it drops to around 11AFR and quickly climbs again toward 12.5.
To be safe to tune it first time start low around 4000 rpm and work your way up to what AFR you are comfortable at. That will depend on boost and timing.
Alan

[930martini]

Alan,
just to get it right: if I install the RPM switch I need to lower my WP first in order to have AFR's around 12.0 at +/- 0 MP. They are now 13.5 at 0 MP.
Thanks

[Alan L]

No.
Set your basic tuning where you are happy with it before fiddling with the switch.
Then decide on the parameters you are happy for the switch to work within. ie how lean do you want it to run before the boost dump.
Alan

[Tonger]

OP - Here are the annotated data points summarized from another post that I have collected in tuning my car over time which is similar to your build. [1.1 bar boost, twin scroll GT35R, Garretson long neck IC, TK headers/exhaust, Leask adjustable WUR, RPM switch, 964 cams, stock heads]

1. Modifying the fuel head and WUR will be essential to getting enough fuel at higher RPM for a high flow turbo like the Garrett. There are different degrees of fuel head modification and it needs to be opened 'all the way' by CIS Flowtech to support 400 hp levels at redline. My FD made two trips to CIS Flowtech - the first time I got the 'normal' mod, the second trip Larry opened it all the way and I finally had enough fuel. The other key factor is to remove the Lambda which restricts flow in the fuel head via a frequency valve. The presence of the frequency valve is a phylical restriction in the system which cannot be completely overcome even by pulsing the valve more frequently. Eliminating the Lambda (78 and 79 cars did not have this) provides the least restrictive path for fuel allowing higher flow rates.

https://cis911primer.com/pages/descr_lambda.html

2. Opening up the fuel head all the way to provide adequate fueling at redline will make you undriveably rich in the midrange, even if you have an adjustable Leask WUR. However, you stand no chance if you don't have the Leask adjustable WUR. ** Update - it seems Leask has stopped his WUR service. Look online for how to make your WUR adjustable, it will save you time tuning.
3. As Patina said, the RPM switch is essential to allowing the vehicle to not drown in fuel in the midrange and still have enough near redline. In my car, the RPM switch is set at 5500 rpm before the car is allowed to see the enrichment pressure.

So in summary you need at bare minimum three things for 400 whp and CIS - 1. Fully opened fuel head by CIS Flowtech - mine is non lambda. 2. Adjustable WUR with good control pressure starting points. and 3. RPM switch.

These three things are common with the folks I know who have gotten their modified cars to run acceptably well on CIS.

4. Other factors such as Euro fuel lines (larger inside diameter), two Bosch 044 fuel pumps, and euro CIS injectors can help even more - I am employing all of these.
5. A real time and data logging AFR meter is essential - you already have this. After tuning the car acceptably, use CIS gauges to record WUR pressure values of working setup for future reference and share them with other users so that they can get up to speed faster.
6. Dyno time is the most efficient way of tuning allowing user to make changes and see changes in real time.
7. Take care to ensure that your fuel pump, WUR, and RPM switch are all getting adequate voltage. Old wiring, marginal fuses, and poor quality red fuel pump relays can all be sources of poor running.
8. Drive your car regularly - CIS hates to sit, especially with untreated fuel.

Here are the WUR parameters that work for me. I can't get an ideal AFR curve like with EFI but it works acceptably well and I can enjoy driving the car.

**Cold Pressure 2.1 bar, Warm Pressure 3.75, Enrichment Pressure 2.0, RPM Switch 5500 rpm

**Idle AFR is set at ~13.0, cruise AFR ~14.3

I still adjust the idle AFR on the metering plate for winter/summer changes to compensate for air density changes using my AFR meter. It's a simple 3.5 mm Allen key adjustment and I don't have to make any other changes.

In the end, I'm just sharing my data points because there are good folks like Chris Carroll at TK and Cole (miss the dude) who have taken significant time to help me and I'm just trying to pay it forward.

** Maybe Patina and Alan can share their WUR settings also? It would be helpful as additional data points for those who need to tune their cars and have different configurations.

[Alan L]

I am generally running 3.6 bar WP, and boost dump between 0.3 and 0.5 bar. Generally set the switch at 4600 rpm. These are the general parameters I use - but I tune it at the track on the day. Have set the WUR up so I can tweek the WP and boost dump without removing the WUR. 5 min job.
I run the AFRs up to 12.5 without concern. I aim for the switch to come in around 12.5 AFR and I aim to not go leaner than 12.5 at the redline. I must say it took a LOT of fiddling with the fuel system to get enough fuel to accomplish this comfortably. But it is running reliably in those parameters every time now.
I generally don't run more than 0.9 bar. Very rarely I will run it to 1.0, assuming the tuning will permit it.
Alan

[930martini]

Thanks Tonger and Alan for all the info!
I do have a Euro engine with a 037 FD and an adjustable WUR. I do not expect to get 400hp out of my engine and I will not enlarge my FD yet... I hope to get the AFR's right with my current set up except for adding the RPM switch. I think that my AFR's are not to far off except for the midrange fuel dump. As soon as I have installed the switch I will check my AFR's and measure CP's again.

[DSM]

Hi Marco,

I have 4800 rpm chip installed for boost fuel dump. Took a few days of adjustment to get it right. CIS is a balancing act. See attach data log. Wish I could tell you exactly what to do to get desired result but its just not that cut and dry. My advice would be set all the pressures & sensor plate for your application per spec then make small incremental changes one at a time, data log and review. Obviously pay close attention to AFR under boost. Do not want to harm engine. After changing different things you'll notice patterns and figure it out.

Attached pull is from my blue 930. Stock rotating assembly 3.0 CIS with BLWUR, K27, B&B HE, AEM EBC, Garretson IC, BOV dump to atmosphere.

Click link to watch full screen. Embedded file will not go full screen, not sure why? Pause/play or pause and move seek bar to see any specify point. See top right (RPM/AFR/MAP) readings. I tuned it street driving. Still a bit rich under boost but left it there for now.

Dante


LINK: https://drive.google.com/file/d/1nDN0Zbeo1f6PJzXQUpF1m38xyzfkZ8ku/view?usp=share_link

[Bucketlist]

Not to hijack but this is the first video file I've seen loaded here that would play in the window, good job! I need to try this.
I have been working with my LM2 to generate some similar log files.

[patina]

Originally Posted by Tonger

OP - Here are the annotated data points summarized from another post that I have collected in tuning my car over time which is similar to your build. [1.1 bar boost, twin scroll GT35R, Garretson long neck IC, TK headers/exhaust, Leask adjustable WUR, RPM switch, 964 cams, stock heads]

1. Modifying the fuel head and WUR will be essential to getting enough fuel at higher RPM for a high flow turbo like the Garrett. There are different degrees of fuel head modification and it needs to be opened 'all the way' by CIS Flowtech to support 400 hp levels at redline. My FD made two trips to CIS Flowtech - the first time I got the 'normal' mod, the second trip Larry opened it all the way and I finally had enough fuel. The other key factor is to remove the Lambda which restricts flow in the fuel head via a frequency valve. The presence of the frequency valve is a phylical restriction in the system which cannot be completely overcome even by pulsing the valve more frequently. Eliminating the Lambda (78 and 79 cars did not have this) provides the least restrictive path for fuel allowing higher flow rates.

https://cis911primer.com/pages/descr_lambda.html

2. Opening up the fuel head all the way to provide adequate fueling at redline will make you undriveably rich in the midrange, even if you have an adjustable Leask WUR. However, you stand no chance if you don't have the Leask adjustable WUR. ** Update - it seems Leask has stopped his WUR service. Look online for how to make your WUR adjustable, it will save you time tuning.
3. As Patina said, the RPM switch is essential to allowing the vehicle to not drown in fuel in the midrange and still have enough near redline. In my car, the RPM switch is set at 5500 rpm before the car is allowed to see the enrichment pressure.

So in summary you need at bare minimum three things for 400 whp and CIS - 1. Fully opened fuel head by CIS Flowtech - mine is non lambda. 2. Adjustable WUR with good control pressure starting points. and 3. RPM switch.

These three things are common with the folks I know who have gotten their modified cars to run acceptably well on CIS.

4. Other factors such as Euro fuel lines (larger inside diameter), two Bosch 044 fuel pumps, and euro CIS injectors can help even more - I am employing all of these.
5. A real time and data logging AFR meter is essential - you already have this. After tuning the car acceptably, use CIS gauges to record WUR pressure values of working setup for future reference and share them with other users so that they can get up to speed faster.
6. Dyno time is the most efficient way of tuning allowing user to make changes and see changes in real time.
7. Take care to ensure that your fuel pump, WUR, and RPM switch are all getting adequate voltage. Old wiring, marginal fuses, and poor quality red fuel pump relays can all be sources of poor running.
8. Drive your car regularly - CIS hates to sit, especially with untreated fuel.

Here are the WUR parameters that work for me. I can't get an ideal AFR curve like with EFI but it works acceptably well and I can enjoy driving the car.

**Cold Pressure 2.1 bar, Warm Pressure 3.75, Enrichment Pressure 2.0, RPM Switch 5500 rpm

**Idle AFR is set at ~13.0, cruise AFR ~14.3

I still adjust the idle AFR on the metering plate for winter/summer changes to compensate for air density changes using my AFR meter. It's a simple 3.5 mm Allen key adjustment and I don't have to make any other changes.

In the end, I'm just sharing my data points because there are good folks like Chris Carroll at TK and Cole (miss the dude) who have taken significant time to help me and I'm just trying to pay it forward.

** Maybe Patina and Alan can share their WUR settings also? It would be helpful as additional data points for those who need to tune their cars and have different configurations.

This post is full of great information, thanks for taking the time to put it out there!

As Tonger stated, knowledge transfer from the top down, across the community, is the only reason most of us have our cars running worth a damn!

I was lucky enough to have Leask rebuild my WUR just before he shut down his business. It would be nice to know who can service these units in the future. For example, my WUR was great for about 10-years until it developed a tear in the enrichment diaphragm. This leak presented itself as a dramatic stumble/erratic AFR spike at boost onset.

Specs on my car:
3.3 US Engine
007 Fuel Head (25% more fuel capacity)
Leask WUR/CSV @ 4800rpm
RarlyL8 Headers/Hooligan Exhaust
Andial Shortneck
Tial F46 w/.7 bar Spring
Dual Stage Manual Boost Controller
K27 7200

360whp @ 1.0bar

My current fuel pressures:
Cold: 2.3 bar (I think)
Warm: 3.8 bar
Enrichment: 2.4 bar

My idle AFR is around 13 and cruise is around 14.5. At 1 bar of boost at 70* ambient, AFR is solid 12.0 stepping up to 12.5 before the CSV kicks in, which knocks it back down to 12.0 where it then steps back up to 12.5 before redline. To avoid constant tuning based on ambient temperature, I have installed a dual stage manual boost controller. That way, if I am running a tad too lean for my comfort, I simply flip a switch and run slightly less boost (.8 - .9 bar) on my "base" tune. For me, the slight power loss (~15hp) is worth the convenience of re-tuning the WUR every season change. DSM said it best - tuning these cars is a balancing act. The nice thing is, with such low compression, they can take a slip here or there unscathed. Optimizing the tune is critical if you are going to be running the car hard for extended periods of time.

[patina]

The funny part is I know so many 930 guys are out there running an exhaust and a 1 bar spring and have never seen a wideband AFR gauge in their life, lol. Meanwhile, a few of us over here are obsessed with tuning these cars.

[patina]

As an update. I was once again running into some lean conditions upon boost enrichment in our current ~80* ambient temp. I've just set my cold pressure to 1.9, warm pressure to 4.0 and my boost enrichment to 2.0. It's storming badly here but will post results once I am able to go for a drive.

[patina]

Here are some additional data points straight from Brian Leask.

"Here are the control pressures I run on my personal 400+ RWHP 930 with 007 fuel distributor, K27HF, B&B headers, and 1.1 bar of boost. The RPM CSV kit is needed to keep the AFR from dropping into the 8.0s and 9.0s when full boost hits around 3500 RPM.

Warm: 4.1 bar
Enrichment: 2.0 bar"

[Alan L]

There is a point where dropping the WUR pressure on boost, makes no difference. What you are doing is making it easier for the metering arm to open the metering slits in the FD. Once they are fully open, that is it. Nothing more to gain. Depending on WP I would have thought 2.0 would be in that territory - ie same result you would get with 1.5. And raising the WP simply leans it out across the board - requiring a bigger dump at boost.
I have an 007 FD also and am running close to the specs from the manual. But the other part of the equation is to make sure the pumps are doing what they are supposed to - otherwise you end up compensating via the WUR (or trying to).
Alan

[patina]

So 4.0 was way too high. Ambient temp today was ~50* and I was running .8 bar. Cruise AFR was around 16, not good. Dropped it down to 3.6, cruise dropped to around 15.5. Dropped it down to 3.0 and that was the sweet spot for my car. Cruise is around 14.7 and the car is very responsive off boost. Boost enrichment at 2.0 seems to be a good setting for me. With the CSV set to 4600rpm, I'm seeing a peak 12.4 AFR that drops to 12 or so when the CSV triggers and tapers back to maybe 12.3 or so at redline. Maybe some more fine tuning but this seems like a good setup for me. I can only imagine Brian's fuel head is opened up more than mine and perhaps he is running euro fuel lines and injectors for the 4.0 warm pressure to produce a safe cruise AFR.

[patina]

I am also considering a permanent mounted fuel pressure gauge at or near the WUR. Seems like it would be useful to glance at occasionally to ensure WP has not shifted like I seem to have experienced.

[Alan L]

That is a very low (rich) WP setting. I doubt the 2.0 boost drop is actually that large, ie get same result with half that. At a WP of 1 bar that would be a pig rich setting.
How are you determining cruise 'sweet spot'? Are you aiming for a particular cruise AFR number?
That is a very oddball WUR setup number wise.
Alan