stu.p

Jetskied,,i know in my 965 there is a small earth that screws on to the side of the intercooler and if this is even loose your car will shut down on boost

UT_tech

Sure I would be happy to provide additional details. Sorry for the long-ish post but I wanted to give a snapshot of what we’re seeing.

We've been getting a LOT of feedback which has been great. This feedback has been positive and very useful. The only change we've made to the product itself (so far!) as a result of this feedback was to change the RPM sensor. You may have noticed that we used to use a small ferrite toroid core through which a sparkplug wire was passed. This was a problem for MSD ignitions (because we count the pulses) and the installation wasn't as clean as we would like. We recently changed the RPM input to use the Tach signal. This change also happily gave us more pulses to work with (6 times as many) which allowed us to speed up the control loop response time. This is a firmware update for anyone already purchased a UTCIS-PT. The firmware can re-flashed on the car.

We've been getting a lot of feedback on tuning the engine control maps. There seems to be a very consistent problem with high output 930 engines. Apparently with most street-able cams the volumetric efficiency (VE) increases in the mid-range then falls off sharply just before peak power. The manifold air pressure at WOT is usually constant from mid- to max power as set by the boost controls. This increase in VE means that the “effective” boost of the turbo is greater in the mid-range. We’ve been getting VERY consistent feedback that the AFR needs to be very low, 12:1 or 11.5:1 in this range, so the excess fuel can act as an anti-detonant. As you move up in the power band the mixture needs to lean out but still stay rich. Using this technique one of our customers found 50ft-lb more torque in the mid range. We’ll post the dyno results as soon as we get them. It’s hard to visualize how RPM and Manifold Air Pressure work together to affect Control pressure (and thus AFR) so I’m posting the 3D base map to give you a better idea of what’s going on. Every aspect of this map can be easily and quickly changed.

We haven’t posted about the wealth of information that’s been flooding in because we don’t have “finished” case studies yet for high-output cars. We’ve had many 930 owners with bad WURs who simply replaced the bad WUR the UTCIS and they’re happily back to hauling groceries. High-output engine are, however, very interesting. We’re gathering “complete” how-to installations to give specific guidance.

We had a very interesting installation just a few days ago. A customer with a race-ready 930 installed the UTCIS-PT then took the car for a dyno test. Sure enough, the tech immediately spotted the mid-range problem spot (due to higher VE as I mentioned above). The tech lowered the control pressure in that range of RPM and MAP and the torque increased as predicted. Then the tech noticed that the AFR at peak power was higher than it should have been, about 13.5:1. At this point the engine was making about 550hp but the tech knew it could do more because of his experience with similar cam/turbo/exhaust setups he’d worked with in the past. The tech then used the software to lower the control pressure in this specific part of the power-band. He lowered the control pressure from 2.7bar to 2.0bar and the AFR did not change at all. He lowered it again from 2.0bar to 1.0bar and the AFR still did not budge. At this point the tech called us.

After some discussion I agreed with the tech that we needed to confirm that the UTCIS was really delivering and reporting accurately 1.0bar of control pressure. A race-ready 930 engine running at 550+ HP is not a terribly inviting place and there was a concern that electrical noise/vibration/heat might be throwing something off. The tech did the dyno run again with a CIS gauge set connected to verify the control pressure readings. A helper held the gauge during the run so it wouldn’t batter itself to death. This run verified that the control pressure reported by the data link was accurate. The fuel delivery system was simply running out of capacity. More tests showed that the system pressure was stable (fuel pumps were fine) and the injectors had more capacity left. That left the fuel distributor. That’s as far as we’ve got with this car as of today. As soon as we get more progress we’ll post the before and after dyno results. This car is a great study in what the digital WUR is and isn’t good for. The digital WUR is a great tool for visibility and tuning which can only be equaled by a full EFI conversion. It does not, by itself, make more power. If the capacity limitation in this car turns out to be the metering slits in the fuel distributor then it can be replaced or reworked. How much power can this engine make? I have my opinion, but without final test results I can’t prove it so I’ll wait for the next dyno test.

The fuel delivery in the CIS system has lots of capacity but it’s not linear. There are flat spots, hills, and valleys galore. Navigating the “topography” of the CIS system is easy, if you have a map. Adjusting the mechanical WUR helps but it’s a compromise. Adjusting the WUR will to fill in a “valley” will also raise the hills and the flat spots. Fortunately the control pressure is a very effective tool to manipulate the AFR if adjusted where and in the amount needed.

We’re hoping that those of you who’ve worked out engine control maps will be willing to share them. Over time it should be much easier to tune your 930 because the myriad of different engine components will have been tried by someone and documented in the form of an engine map. Please make note of any aftermarket parts you’re using in the “Notes” section of the software. These notes are saved with the engine map.

There are a couple of ways to tune the engine control map. You can use a wideband AFR gauge. You’ll be able to feel and hear when the AFR isn’t right. For example, the base map leaves the control pressure at 3.2bar above a manifold air pressure of 1.0bar. You may notice the onset of pinging at 0.5bar of boost which is 1.5bar of manifold air pressure. If so then lower the control pressure in small steps, say 0.1 or 0.2 bar at the point of boost where needed, until it’s satisfactory. There are controls in the map editor to “clone” the control pressure vs manifold air pressure map for different RPMs. Most cars are tuned this way. A dyno test is mandatory for a high-output modified engine. Any 930 engine will benefit from a dyno test to accurately measure what’s going on.

Both the adjustable and the digital WUR bolt into the same location so it’s really either but not both.

WERK-I

Steve,
Thanks for the excellent writeup. So, you are not not seeing any fuel delivery imbalances across the ports? If yes, then all we have to worry about is that pancake manifold airflow imbalance and the capacity of the fuel distributor. Both can be worked on.

911rudy

What is control pressure?

UT_tech

You can search Rennlist for a very complete explanation of the CIS fuel system. There's a brief explanation just focused on control pressure on page 3 of this document:

http://unwiredtools.com/manuals/CP%2...anual%20A1.pdf

911rudy

Thanks Steve, the manual piece you sent helps me understand. I figured it was fuel pressure but wasn't sure.

UT_tech

Werk-I:

We have indeed seen some imbalance. Fuel delivery imbalance can be hard to troubleshoot because the symptoms can vary. We've been asking experienced Porsche techs how they approach this problem and we've had some interesting feedback. The factory procedure calls for using a large (=expensive) graduated glass cylinder. Here's an idea for testing the fuel delivery balance that I have not personally tried but it sounds great:

1. Get a digital scale with a resolution of no more worse than 0.1oz (0.6% @ 1lb). Here's one:

http://www.target.com/Primo-Digital-...e=1&rh=&page=1

2. Find 6 containers of one qt capacity. Empty oil bottles should be fine. The bottles should be clean so that the gasoline and be re-used.

3. Weigh each of the bottles on the scale, then mark the weight on the bottle.

4. Pull all of the injectors and drape the injectors, with the fuel lines attached, into the bottles. Mark the cyl number on the bottle.

5. Pull up on the air metering plate as far as it will go to simulate max airflow. Don't force it, just make sure you're at the end of travel. Using a stopwatch, run the fuel pump for exactly 30 seconds. Use a switch or jumper to run the fuel pump relay, not the starter

6. Weigh each of the samples, then subtract the weight of the bottle. The samples should weigh within a few percent of each other. If you have a low or high cylinder swap the injector with another cylinder. and weigh out another 30 second sample. If the results change then the imbalance is in the injector.

The total quantity pushed out in the test should be something like this:

Let's assume that the fuel system can supply enough fuel for 600HP. Using a slightly inefficient fuel burn rate of 0.6lb per HP-hour, this equates to 360lb of fuel per hour for the engine. That's 60lb per cylinder per hour, or one lb per minute. If you run the test for 30 seconds then you should have about 0.5lb of fuel in the bottle. Isn't that great? In addition to testing the fuel balance you'll also find out the capacity of the fuel system (at Manifold air pressure=0!).

Autobahn

Steve,

thanks so much for the excellent write up.

nathanUK '81 930 G50

Steve, I think you should make it clear you don't want people using your UTCIS without a high quality AFR setup. It doesn't take much to customise their rings and pistons.


Are you aware of the Imagine Auto modified fuel head? They have been CNC'd to allow more flow. Trying to get 550hp from a 930 on CIS was a bit adventerous

nathanUK '81 930 G50

Could you elaborate on this for us please?

TIA

UT_tech

Just by way of a clarity (disclaimer?) let me emphasize that the addition of the digital WUR does not improve power (by itself), and it does not increase the flow through the fuel distributor.

The stock fuel distributor can flow a lot more fuel than the stock power level requires but we don't have test results to say how much that is exactly. When techs call us with questions we ask them whose parts they're using. There's a very consistent pattern regarding fuel distributors. We hear very often that Imagine Auto and CIS Flowtech supply fuel distributors that really work.

We have also heard from a couple of tuners who have used a fuel distributor from a Mercedes M110 engine. That's the engine used in this car:

http://en.wikipedia.org/wiki/Mercedes-Benz_W116

If anyone has experience with this swap please PM me. I don't understand why this would work because the Mercedes application is only 160HP normally aspirated in the euro version.

Nathan makes an excellent point. I agree completely. If the 930 engine runs too lean at high power then parts can be destroyed very quickly. A good AFR gauge can let you know know when the AFR is beginning to get too lean before you can hear it or feel it. I also agree about a "quality" gauge. We seen a lot of calibration problems with cheap AFR gauges, or gauges which claim to work with any wideband O2 sensor.

nathanUK '81 930 G50

Could you elaborate on this for us please Steve?

TIA

UT_tech

One more minor point, I mentioned previously that the digital WUR does not increase the fuel flow through the fuel distributor. That description was a bit sloppy. I should have said that the maximum possible fuel flow is not affected.

The acual fuel delivered by the fuel distributor, if (!) not limited by other components, can be improved using the digital WUR. This can be done by setting the control pressure at a value lower than would normally be possible. For example, let's asume that the AFR at full power is still slightly too low and the control pressure at that specific point is 2.5bar. You can lower the control pressure to 1.0bar or even lower and the fuel flow should increase if there's more capacity left.

An easy way to check if there's more capacity left to to lower the control pressure at a specific point. When the fuel system starts to run out of capacity then further decreases in control pressure will no longer lower the AFR.

RarlyL8

The fuel head used is from the big V8, not the 6 cylinder. The stock 930 fuel head casting is also used for the V8 Benz.

UT_tech

That's very interesting. So 2 of the injector output ports are simply plugged? That's a great idea. I suppose the best choice would be from a 6.9 liter model, something like a 0 438 100 012 without lamda, or 0 438 100 041 with lamda. Hmmm.... My Bosch book shows that same part number is also used on the generic 450 models (450 SE/SL/SEL/SLC).