Geoffrey

CJV,

The thing that is interesting to me is that the engine appears to cycle in that aformentioned rpm range. I'd find it difficult to believe that the Fuel map would go up/down/up/down/up/down in such a regular pattern with such great variations. You'd have to see AFR varing as much as 3 points in regular intervals. I'm wondering if the ECU is reacting to something. I would think that the ECU would have an Air Temp sensor and a atmosphere Baro sensor (MAP) to make any compensations in air temperature and density.

Geoffrey

Since you say that the AIC is not activated until 6000rpm and the pattern begins well before 6000rpm and continues after the AIC is activated is additional information that leads me to believe it is not and AFR issue per se at all, but something else CAUSING fueling issues. Without the ECU data logging facility that aftermarket ECUs have, it is difficult to speculate. Perhaps a fluxuation in fuel pressure, injectors being over driven or sticking because of too much pressure, things along those lines is where I'd start. It is such a large jump from peak to valley that I doubt it is the computer advancing the timing, then reducing the timing, but I'm not all that familiar with how a stock ECU works in detail so I really couldn't say.

sharkster

There is an AWD in mountain view called ATP. I believe there are only two in California (one in LA).

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by cjv:
<strong>Geoffrey,

You are correct about not having using the best type dyno. Unfortunately I do not know of any four wheel dyno's in Northern California. I believe what you are refering to is the area between the 3900 and 5600 rpm range. This problem is caused by the air/fuel mixture which is varing around 11.0-1 in this area. Actually, it is not quite as bad as the 100 rpm interval shows. The actual dyno run was is six pages long, in ten rpm intervals.

Any way, I had to show the good along with the bad. The bad is, the run was conducted under high humidy conditions compared to the previous run. The good is, what air/fuel modifications that were made, closed the gap and the torque figures improved nicely. The problem area prior was between 3100 and 5700 rpm's and 6700 thru 7400 rpm's. The problem area now is between 3900 and 5600 rpm's.

Next dyno run should be in about two weeks. Thanks for your computer work and resulting comments.

<img border="0" alt="[thumbsup]" title="" src="graemlins/bigok.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">

sharkster

Hehe, well we all owe you since all of your TT's laundry is kindly laid out for all to see... Sent you a PM.

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by cjv:
<strong>Sharky,

I learn something new everyday. Thanks for the information. Do you have any more information on this place, address, phone number or website?

<img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">

Steve Lavigne

Chad, your car is simply amazing.

FYI, I read several months ago about someone with a tiptronic 996tt who blew up his center differential on ATP's awd dyno.

Look here, three posts down the page:
<a href="http://supraforums.com/showthread.php?s=&threadid=95488&perpage=25&pagenumber=6" target="_blank">Supraforums: ATP Dyno Day</a>

I posted it in <a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic;f=6;t=001277;p=2" target="_blank">this</a> thread a couple of months ago.

Also, using a OBD2 scanner/logger to log data on the dyno could assist with tuning. I've never used them, but here is a link to one such system:

<a href="http://www.obd-2.com" target="_blank">http://www.obd-2.com</a>

PorschePhD

Chad has a bigger and better diff, however I too still can not recommend the AWD dyno. I have heard a stories about the 996TTs on AWD dynos.. <img border="0" alt="[nono]" title="" src="graemlins/nono.gif" />

Steve Lavigne

I just took a closer look at that OBD2 site. Check out the 'SPK AD' (spark advance) gauge. That looks very useful. I'm sure all of that information can be logged and then incorporated with dyno data using the rpm to match the data.

<img src="http://www.obd-2.com/dashg.gif" alt=" - " />

caneaddict

Chad,
Stephen just mentioned that you have "a bigger and better diff [than standard]". Have you already gone ahead and changed the front diff. I know you were considering it and that it was going to be very expensive. I assumed you hadn't done it yet since I didn't read anything.

Konstantin

you probably know this but I would buy the <a href="http://www.aquamist.co.uk/" target="_blank">http://www.aquamist.co.uk/</a>

Konstantin

jimrd

CJV - sounds interesting. When you say mapping, do you mean mapping of the water injector system or ECU mapping? I'm currently having the Ruf conversion done - if I were interested in this system, would it screw up the new Ruf programming?
Jim

PorschePhD

You map the water injection. You can remap the ECU, but you should stabilize the ECU program then use the water injection to tune. For example where you might be on the edge of needing higher octane or additional fuel the system would spray a mist of cool dense water into the intake. This allows the system to drop the AFR. There are many systems, but the one CJV is talking about actually has a mapping like an ECU to inject the mist of water based on several variables. <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />

TB993tt

FWIW
An engine builder I know in the UK tried installing an Aquamist system on a 650+hp RS Tuning race engine - I think it was a 996tt based motor, with the usual promises from the manufacturer - what did it do for power/torque - on the dyno no gains whatsoever.

jimrd

Thanks Stephen - thats what I thought, but I was not sure. I look forward to yoour testing. It sounds like this could be a safe/simple way to increase torgue and perhaps add a margin of safety.
Jim

BC

CJV - I would really like to think that the 300 dollar system is just as good as the 2 and a quarter thousand one.

If Your ECU set up can control the additional injector, then why not a methanal and water mixture map? A nice big tank, a high pressure pump to properly atomize the mixture, and a nozzle.

Do we know why one is 300 and the other is 2250?

Brendan

BC

CJV - I am sorry, I was under the impression that your additional injector was being controlled by a piggy back? I may have misread as per your explination to me, but there ARE 23 pages now

Motec notwithstanding, I am sure that an aftermarket ECU would/could be programmed to pass smog. Just download another program. Now I am sure you know that, but it should be said. Now, with respect to the facts of:

- Big Brother may check the computer for smog cert.

- You may be under a warrantee still.

- Your PSM and ABS is controlled by the computer.*

...An aftermarket computer such as motec (but in reality, you would do great with <a href="http://www.dtafast.co.uk" target="_blank">www.dtafast.co.uk</a> - as I will) may not be what is in your game plan for this "street legal" and "un-opened" motor.

My notion in the above post was made with regard to the price difference between a tank, pump, and nozzle for 300, and 2250. I understand now that the more expensive (by almost 10 times) unit has some sort of mapping computer to make the mist come in at the appropriate times.

I would think that the mist should come in at, well, WOT. Maybe even anything above a certain boost, or throttle angle. All you need is a simple switch for that.

I like the big-A$$ tank that the hiebar stuff comes with though.

Just for an info purge here, water/methanol injection is just a tank (large or small), a nozzle that will correctly atomize the mixture and not clog, and a very high pressure pump so that this mix WILL atomize.

&lt;&gt;&lt;&gt;&lt;&gt;&lt;&gt;

* Are you sure the ABS and PSM is not linkable? The ABS does not have its own computer? Same for the PSM? I would think that they do, and then simply trigger a few codes to the main computer, such as spark, fuel changes to control slip.

But really, I only have the Porsche Flagship from 1989. What do I know?