NineMeister

From 2002 through to the current 997GT3 Cup & RSR Porsche Motorsport fitted the Motec ADL & display as standard.

DaveK

What we need is a C4 owner who wants motec (and nothing else). Colin doesn't have a 4WD dyno - so the C4 owner could go to an independent dyno and get readings.

Then take the car to Colin and get Motec.

Then return to the independent dyno and get another run.

Wouldn't that be conclusive?

tonytaylor

I find it difficult to believe that Porsche were not conservative with their fuel maps for the following reasons;
1) to prevent warrenty claims they would error on the safe side
2) the bosche knock control isn't that sophisticated; knock still occurs and the control is reactive. OK it prevents further detonation but over long periods damage is still likely
3) there is far to much anectodatal, circumstantial, hearsay, unstubstantiated, unqualified evidence for an improvement in power with rechips for it not to be true. Even Lorenfb says 5%. I have no doubt meta analaysis of all the available data would confirm the power improvement claim.
4) My own car, albeit with intake mods as well, is faster with the new chip measured over a set distance. Its also faster than other stock 964s measured on the same accelerometer based performance tool. It's been independantly dyno'd over stock hp.
5) I believe Porsche decided the 964 was going to produce 250 hp regardless of what the engine was capable of and set the ignition maps to suit that hp level. 964s NA can make 300hp with ease and it costs buttons to do so, hence to suggest Porsche, with their budget, had optimised the 964 engine is risible. Why 250hp? if the engine was optimal surely it would be 248.7 or 251 .3 or whatever. 250 is just a nice round figure. The 964rs is the same engine but makes more power because it has a different chip - go figure .

Geoffrey

The stock maps are not optimized for performance. The fuel curve dips to .8 lambda at 4500RPM and again at 6500RPM. The ignition timing is not optimized for high octane unleaded street fuel (93). The Cup chip with more advanced timing and similar fuel curve (I believe them to be the same as the stock chip, but don't have the table data) produces 10rwhp more, simply due to ignition timing.

If you had access to the tables in the Motronics and could change the load strategy from an AFM, I believe it would produce the same power as MoTeC. MoTeC is not a low budget racer equipement and is run in many professional series and is on Grand Am DP cars and I've personally done tuning for Mazda's Grand Am effort. But I'm not going to get dragged into a which is better argument. Controlling basic engine functions such as fuel and ignition timing is not that hard. Even the internet has blueprints for a "build it yourself" ECU (Megasquirt). The difference between MoTeC (or any aftermarket ECU) and a factory ECU is total control over the engine management strategy and acceess to all tables.

Red rooster

Geoffrey,
Very well put. I couldnt agree more. I have converted Motronic to being a tps system for race cars with six individual throttles and it works very well.Because there were other changes, cams etc ,power numbers for this thread are meaningless.

In Europe the 964 was calibrated for 95 RON fuel and made 250bhp. The RS version has the timing raised and made 260 bhp. The 993 was introduced requiring 97 RON fuel and was calibrated for 272 bhp.
Standard 964 mapping is far from ideal for maximum power production. In common with pretty well all German manufacturers the 964 has to be able to run at full throttle on an Autobahn for around 50 miles and be totally reliable.
This forces calibration engineers to back off top end timing and increase fuelling over the numbers that would be optimum.

Hope that may help ?

Geoff

Lorenfb

"If you had access to the tables in the Motronics and could change the load strategy from an AFM, I believe it would produce the same power as MoTeC." - Geoffrey -

Agreed! Some do have access to the tables, though.

As mentioned, the key is availability of higher octane fuels which is very limited in the USA.
Just like with the old distributors & centrifugal advances, increasing the spark advance
(performance chips) ALWAYS produces more torque, but the issue of detonation becomes more problematic.

Sure you can get a little more out of tweaking the maps, but who wants to be ALWAYS
driving near (limited to) the only neighborhood high octane fuel source????

KirkF

Since I have so many experts in this thread right now, let me ask this question:

To get a C4 on a regular dyno, couldn't you just slide the connector sleeve forward on the driveshaft, and effectively disconnect the front dif from the transmission. Do your dyno runs, and then reconnect it?

Kirk

DaveK

My understanding is that you can disconnect / run a 993 on a 2wd dyno. You can't a 964.

TR6

Is 93 octane in the US considered adequate for the purposes of this discussion? That's what I burn in mine. Or are you meaning higher octane?

Red rooster

Kirk,
Dave is absolutely right. The 964 C4 torque split differential doesnt allow a disconect. The 993 viscous coupling does .

Greg,
I run on 93 PON and would consider that pretty reasonable octane. The gas over on the east coast can be pretty poor , certainly nothing like what is available in Europe on the High street !!
The available fuel quality can certainly limit what can be acheived by DME map recalibration.
The 964 is calibrated to run on 95RON , about 91 PON ,so you do have opportunity !!

Hope that helps

Geoff

Lorenfb

"Is 93 octane in the US considered adequate for the purposes of this discussion? That's what I burn in mine. Or are you meaning higher octane?"

The 93 octane may in some cases still be too low for the aggressive timing which
performance chips use to get the "feel" of a performance improvement. Many here
on the west coast with 964s have reported pinging even with the limited availability
here of 93 octane under heavy loads and high temps during the summer. As a result,
they've gone back to using the stock chip.

Is it really worth it having to closely monitor for pinging and always
making sure than an adequate octane level is being used for the very slight
performance improvement? I doubt it for many!

Geoffrey

When I had some chips burned for me, I found I could not improve upon the 964 Cup ignition timing with 93 octane fuel. Granted it wasn't steady state ignition timing testing I was able to do to arive at the numbers, however, I did what I could do.

TR6

I guess one could always dump a can of 104+ booster in the tank!

KirkF

One of these days we really must discuss exactly what happens in a C4 when it sees the rear wheels spinning and the front wheels standing still. I am guessing it would try and shift power to the front axles... But if the front axles are dosconnected, then what?

I double checked and there is no awd dyno in Winnipeg. There is talk of one maybe going into fargo, and apparently there is one in Minneapolis. (But minneapolis is a 10 hour drive) Calgary has one, but its 14 hours. Sucks to live in the prairies!


Kirk

KirkF

BTW:

I read in 911 & Porsche World that people in the UK will be able to get 102 octane fuel at BP filling stations. There is nothing even close to that here. I think the best I can do is 94 octane. Looks like DaveK is in luck.


Kirk