Zakowsky

So I have search all over and can't find a single example of anyone trying this on any kind of Porsche turbo. The idea is quite simple, the MAP sensor there on the Y-pipe sends a signal telling the ECU how much boost is coming from the turbos based on the voltage it puts out. By putting a potentiometer and a resistor into the circuit you trick the ECU into thinking boost is lower than it is and it calls for more. Used moderately, we should be able to increase the 0.7 bar max on non-CTTS engines up to 1.0 without serious problems or risk. Same idea as using a tuning box rather than flashing the ECU, although I realize tuning boxes also change the MAF, temperature and cam timing sensors as well.

Audi, VW and many other owners play around with this, so why not with a Porsche? Does it not work because of something in the ECU design? Or is the air/fuel mixture or cam timing so sensitive that it throws everything off? Or do people just not want to take the chance on frying an ECU that costs several times more than for other cars?

If anyone has tried this it would be great to hear how it went. Thanks!

J'sWorld

You can use a diode to clamp the max output by the map sensor. By doing this you would need to run a boost controller and if anything happens that results in an overboost you are going to be very unhappy. Yes guys do it.

Zakowsky

Thanks, I'm encouraged to know that some people have done this! I agree the Zener diode method to cap the max voltage can be dangerous. But I was thinking of using the resistor method to lower the voltage coming out the signal line at all pressures, that way the ECU could still kick in and either open the wastegates or trigger an overboost.

My CTT cuts the boost at 0.7 bar, which is about 3.2v coming out of the MAP. So if you shifted the output signal voltage down 20% that would mean that at around 1.1 bar when the MAP would normally be putting out 4.0v, it would now put out 3.2v and the ECU would then cut the boost.

Or that is the plan, anyways!

John Welch.

How are you going to add fuel to that extra air? Detonation is not a pretty thing.

BamaScoot

You want to bypass all Porsche's fuel maps and safety mechanisms so you can run extra lean? Good luck.

Zakowsky

My understanding is that the mixture is primarily regulated off the MAF data, and in other vehicles that use the same MAP sensor supposedly the mixture map works up to about 15 psi, then detonation becomes a problem. At this point you would have to put larger injectors in. But by setting modest goals (like an increase from 0.7 to 1.0 bar max) I’m hoping it will be OK - I was planning to monitor fuel trim, assuming the ECU will try and compensate up to the maximum it can adjust, and stop when that is reached.

Thanks for the feedback btw - if this is a bad idea I want to know about it!

nodoors

I think you are correct. The stock maps and injectors should have more than enough headroom to bump up the boost. Making sure you monitor the air intake temp, fuel trims, and use high octane fuel in these experiments and progressively step it up and I think you are pretty safe. Your right foot will control how long you stay at high boost levels.

If you want to play it really safe install a high quality wideband O2 and EGT gauge and you will be able to safely try this low budget route without too much fear. I think the reason people don't do this on the Cayenne is that there is major fear associated with the cringeworthyingly high replacement cost of a blown engine, or even putting holes in the exhaust to weld in bungs for extra sensors like an O2 or EGT gauge.

It is probably the same reason that nitrous is highly frowned upon in this crowd.

user 83838290

Find the thread about my blue 06 CTTS somewhere. My stock boost controll is completely off, I have an electronic boost controller, larger injectors, turbos and so on. It works but I also monitor my EGT, I have a wideband O2 sensor for each side to be extra sure it's not running lean etc.

As a side note - I retired the blue CTTS from DD duty since I need stuff done and don't have time for it at all. But when it drove, boy it drove ;-) I just gotta put all I need on a big pile and pull the engine one more time and finish it. Take this into account when you start messing with the car - every time you need something done to the engine, it has to come out.

J'sWorld

I think you have it a bit twisted.....

You need the zener diode to clamp the max v output. What this does is let the ecu think that you are not reaching the boost psi that the ecu wants to see. The ecu will keep commanding boost to try and reach that voltage it wants to see from the map sensor, and then letting the ecu know that it's time to regulate boost. Which is why I said you would need to control the boost personally. If you were to use a resistor the ecu would not be adding the fuel it needs under boost correctly based on the base maps. The MAP sensor is much more important than the MAF's in the grand scheme of engine safety. If you do this mod you MUST always control your boost pressure. The MAF sensors are primarily used for lean cruise, part throttle tip-in, and emissions. The signals from the MAF's helps the ecu to make small corrections to the base map to achieve these aforementioned priorities. This is why when you unplug the MAF's the engine still runs great. It can also make the engine run very rich and potentially be harmful to the cats. One would need to look at the base maps in the ecu and know what they were looking at to assess what all this means to the CTT. No MAFS = open loop operation.

I highly recommend NOT doing this mod.

Zakowsky

Some great information here, thanks guys. I think the take home message is that this can be done, but must be taken seriously and not just solder in a resistor and a pot. I see what you are saying about the diode now. I am going to look into the EGT and the wideband O2 sensors, and how to go about setting up my own boost controller.

Just to note, while the goal is obviously more power, I was thinking of going this route in part because I just enjoy tuning engines myself. My other Porsche is a well worked on 944, and I have been rebuilding engines for quite some time. And yeah, I can’t believe how you have to take the engine out to do just about anything on the Cayenne! I actually started off by contacting a major ECU tuning company. I sent engine performance data recorded with VCDS and after some time they got back to me and said they wouldn’t advise an ECU tune, as there must be something mechanical wrong with my engine it was so slow! Now I have been working on it for a while (bought it a year ago) and it runs almost perfectly. No hesitation, no misfires, runs up to redline (and a bit beyond) great, idles as smooth as glass, good mileage (relatively speaking). However 0-60 is in the mid to high 6 second range, and although it has 22” rims right now that is still slower than one would expect. The only thing that I still haven’t tracked down is a slight dip when dropping to idle suggesting a vacuum leak, but I have smoke tested it and everything seems OK. There is also a sense that it pulls stronger at slightly less than WOT - it is possible that it has been flashed in the past, so maybe a not so good map is in there now.

So anyway if they won’t tune it, I certain would like to try to! I am watching the MyGenius boxes; it would be great to play with the maps myself, but that still doesn’t seem feasible yet without the master version and removing the ECU etc.

Anyway I’ll post as I proceed, and thanks again.

bigbuzuki

The idle dip is a known phenomenon with these engines resulting in a shudder felt through the chassis.
I've never seen anyone offer a solution to this sub idle dip.

J'sWorld

The Bosch ME 7.1.1 already uses wideband o2 sensors...
If you really want to tune you should check out,
https://s4wiki.com/wiki/Tuning
Because it is the same ecu.

Nefarious Motorsports also has a wealth of information.

The mygenious is just an interface/flashloader/reader, much like a Kess v2. It does not tune or offer any capability.

Here are a couple of EBC's that I like.
https://www.plxdevices.com/Wideband-...7346002719.htm

http://www.gfb.com.au/products/boost...st-controllers

And I am looking at this one for my Cayenne,
https://www.plex-tuning.com/products...st-controller/

You do not have to take out the engine to do everything. Putting the radiator core support into the service position will get you access to a lot. Removing the core support and disconnecting everything will get you a ton of access. The engine comes out the front suprisingly easily. Matter of fact, a couple of weeks ago I put my engine by myself with a cherry picker. It was easy. Now if you have a special table for the engine/subframe/trans. and a lift, it really is very easy and quick to drop it all out the bottom.

The first thing I would do is get yourself a good boost guage or the EBC that has one built in so that you can monitor that properly. The ME7 will adjust fuel up to a point on its own yes. But, when you get to a certain psi and exceed the programmed boost tables you will throw an overboost an go into limp possibly.

A MIGHTYVAC wouldnt be such a bad idea either so that you can check your wastegates actuators properly.

Zakowsky

Thanks bigbuski - the guy I bought it from told me the same thing, but I thought he was just full of it and I would be searching for a leak. So good to know it is in fact the case.

Mr. Haney - wow, thanks for the links! What an awesome collection of information, and this is exactly what I want to get into. Going to take me a while to learn all this, but looking forward to it. One reason I’d consider pulling the engine myself (I don’t have a lift so it would be out the front as well) would be to get to the turbos - I’ve always been a bit suspect of the wastegates. They make a kind of wheezing sound; not the bark of blow back into the intake, but they just don’t sound right. Anyway thanks again for the links and I will update as I work through this.

nodoors

People that have replaced their engine mounts have found that it drastically reduces the effect of the idle dip. When the engine mounts squish down, they transmit a lot more vibration which makes this much more noticeable. Consider replacing them when you pull the engine.

imalek

Hi, just for sharing my experience, going progressively is safer, this is what I have done on my Cayenne S, pressure was from factory 1.2(15 psi), tried the 1.4, then 1.6. I feel that car can be a little pushed more till 1.8, but at 1.6, boost is quiet good for that SUV. It is not a turbo power, but the car is quiet lighter and acceleration is higher.