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Lorenfb 01-27-2004 08:05 PM

Porsche 3.2 DME Performance Mystery

There has been some confusion as to what the basis is for performance
improvements on the Porsche 3.2 from '84 to '89. Some think that Porsche
was very conserative in programming the fuel and ignition maps and didn't
maximize the 3.2's performance. Others think that Porsche lacked the
wherewithal 20 years ago to properly program the DME and left unknown
areas in the maps which could be "harvested" or "hacked" to achieve
dramatic performance gains.

This thinking has lead to the sales of performance chips based on claims
without dynamometer test data and subjective reviews which indicate
a perceived performance increase. As a result, the issue arises as
to whether there truly exists a real performance increase and if so
what is the basis for it. The more key issue is whether Porsche failed
to fully optimize the 3.2 DME for maximum performance.

Published Data:

The Porsche Carrera Workshop Manual page 0.2 (Technical Data) indicates
two U.S./Japan/Aust. models; 930/21 & 930/25. Model 930/21 was produced
for years '84 thru '87 and had a max torque of 185 ft-lbs & a max HP
of 207, requiring an octane of 91. The Model 930/25 was produced in '87
thru '89 and had a max torque of 195 ft-lbs & a max HP of 214, requiring
an octane of 95.

Porsche had three basic DMEs for those years; 911 618 111 05 for '84 thru
'86 which had a 16K EPROM, 911 618 111 14 for '87 which had a 32K EPROM,
and the 911 618 111 20 which had a 64K EPROM. These are all U.S./Japan
type DMEs. These different DMEs are the only major changes Porsche made
which account for the performance difference.

In the Technical Specifications ('84,'85,'86) booklet on page 106,
Porsche indicates an ignition timing change for cars beginning since
11/1986. The timing change (+.5 degrees) increased the idle 80 RPMs.
The max advance remained at 26 degrees at 3800 RPMs, but no in between
values are given.

Test Data:

In an attempt to gather more data, I performed tests on my '88 3.2 using
three different DMEs; a stock 911 618 111 05, a stock 911 618 111 20,
and a 911 618 111 20 with a Hypertech performance chip. The tests
consisted of checking the ignition advance at various RPMs. Each of
the DMEs were tested with and without Pin 10 grounded which retards
the ignition when grounded for NOx reduction.

In doing the test I used a Snap-On MT1261 digital timing light which
provides a digital indication of the ignition advance. Also used was
a digital tach to monitor the RPMs.

The following are the data in degrees:

..........911 618 111 20........... 911 618 111 05..........911 618 111 20 (Hypertech)

RPM.....Adv-W.. Adv-W/O....... Adv-W...Adv-W/O.........ADV-W
1500.......7..............9...............6....... ....7....................9
2000......15............16..............13........ .14..................14
2500......21............21..............19........ .22..................21
3500......28............28..............25........ .26..................30

W - with Pin 10 jumper connected, W/O - without Pin 10 jumper connected


One can basically conclude from the Porsche Published data that the
ignition timing maps were changed beginning in '87 as indicated
(TecH Spec - pg 106) and inferred from the octane increase from
91 to 95 on pg 0.2 of the Workshop Manual. One can also arrive at
the same conclusion from a review of the test data. Therefore,
this modified advance curve accounts for the increased torque
(10 ft-lbs) and HP (7) which can account for a perceived increase
in performance of the '87 and later cars compared to the '84-'86

As a result, it appears that Porsche may have been a little
conservative in the early 3.2 years, i.e. '84 - '86, but decided
to "push" the advance curve with a corresponding increase in the
octane requirement to offset any potential for detonation. So if
Porsche had wanted to, they could have "pushed" the advance curve
further requiring 98 octane as with the 911 Turbo (ROW).

So there is an obvious relationship between torque changes and
small changes to the ignition advance curve and the resulting
octane requirement to avoid pinging. There's no "mystery" to
performance enhancements. Performance tuners have been modifying
the advance curves since "day one". It's also fair to conclude
that Porsche didn't fail to maximize or "harvest" all the potential
performance gain, as there would have been further increases
in octane requirements to levels considered impractical for a
regular "everday" Porsche.

Therefore, performance chip suppliers can always "push" the
advance curves and squeeze that little extra torque that "feels"
better, but what's the cost in potential damage, e.g. broken rings,
from detonation and having to find the next higher level of octane.
These performance chips may "feel" better, e.g. for '84 - '86 cars,
but as can be determined from the Bruce Anderson performance chips
evaluation (Porsche Excellence Magazine), very little if any overall
performance gain really results when checked on a dyno.

Beethoven 01-27-2004 08:20 PM

Before the flames start, let me just say that--in my admittedly very limited knowledge about P-engines--this seems to make a lot of sense to me. I find it hard to fathom that, emission controls notwithstanding, Porsche engineers would leave that much performance on the table.

Por_sha911 01-27-2004 08:24 PM

Lets all just smile and go read something else. Remember, some of us just like to argue.

dickster 01-28-2004 05:03 AM

all very interesting but what about emmissions? - the main area "chipping" makes gains over stock?

Wavey 01-28-2004 05:11 AM


Originally posted by Lorenfb
I'll have to setup my schedule, but I'll go back. If you don't have a 28 pin DME
I'll bring one and a Hypertech chip (one of the better chips) & others, e.g.
Autothority, Porsche Club Sport, & Ruf.

Ill post more details later.

How's that schedule lookin', Loren?

304065 01-28-2004 05:31 AM

Nice writeup Loren. It's nice to see some empirical data rather than subjective impressions.

This whole debate calls to mind the paragraph in Bruce Anderson's book where he says that he has been trying to get more power out of Porsche engines for most of his adult life, that the engine is basically an air pump with heat exchange capability, and that performance gains generally result from making the engine a more efficient air pump.

It seems reasonable to me that Porsche left some ignition advance on the table, as your test shows, and that the aftermarket chip takes it one step further. And I think it's axiomatic that increasing total advance reduces the detonation safety margin, just the same as if you turn the distributor too far.

I would be interested to see a test of the '14 control unit. The front windshield seal on my '88 leaked pretty bad, and one morning after a rainstorm, I went to start the car, not realizing that the control unit was submerged in water. I asked my mechanic if he could find me a used control unit for the '88, and his response was, "No, they are nearly impossible to find used, the Club Racers snap them up." This is because our stock class rules prohibit changing the chip. As somebody posted, there's little doubt that you could program a chip to match the settings in the '14 box and realize a performance increase as long as you were willing to use higher octane fuel (nobody uses catalytic converters) but the point of stock class rules is to limit the amount of money we spend, and also probably save some racer from himself if he decides to program in 40 degrees total advance in a misguided effort to take the pole.

I appreciate also the tone of your post, it is in keeping with the spirit of the board.

old_skul 01-28-2004 06:27 AM

Heh, Loren, you're just on a mission, aren't you? :D

Post away. Let the flames begin. This thread should grow to 5 pages within the day. Steve Wong in 4....3....2....

This space for rent!

Wil Ferch 01-28-2004 07:17 AM

What you say is absolutely true...but I fail to see the " Aha! " factor that you imply we've all been missing. Chip tuning is just the electronic equivalent of what hot-rodders have been doing since day one...changing the fuel delivery and advance curves to gain more hp...if all other mechanical aspects stay the same ( CR of the pistons, valve timing, etc). Going "too far" or "too aggresive" has always been a problem, and is not confined to Steve's or anybody else's chips.

What amazes me is that Steve W...your apparant pretty much saying the same thing and has been saying these things all-along. You BOTH seem to agree that these changes can produce results. You BOTH seem to say that if you harness only "chipping" ( electronic) expertise...and if the tuner doesn't know much about how IC engines work..that can lead to disasterous results. So can going the other way ( knowing engines but not being so good on knowing the TOTAL effect of chip code changes). It seems to me that Steve W has done specific and empirical testing on his own 3.2 car over a ten year period...and has come up with a reasonable compromise (between offering one generic Weltmeister and Autothority...and doing a car-specific dyno run to "match" the mods to the chip). Namely...that he has about 4-5 chip programs that fairly well match the 4 types of external engine mods people are likely to have ( SSI exhaust...stock, etc). So in essence...I continue to fail to see why the bad blood between you two guys..other than the vile rhetoric that inevetably occurs when differing viewpoints are aired.

I think there is also a strong implied position from both of you that Porsche has a different ( more restrictive) set of parameters to deal with, including emissions complinace over the LIFE of the vehicle ( or at least the first 50K miles, including the effect of parts-wear), the need to comply with and respond to warranty claims, and to deal with all types of weather conditions and variability on fuel quality. People who do chips will understand the need to always feed proper fuel octane, and to generally keep "on-top-of" issues and keep their cars in a sharper state of good condition.

So Loren, what new findings does this post provide the reader who avidly follows this stuff ?? Unless I am very mistaken....not much new here. What am I missing?

Wil Ferch :)

RickM 01-28-2004 07:22 AM

For the record: Autothority has many chip programs for their customers. They will also custom tune it to local owners....for a price of course.

Jeff Alton 01-28-2004 07:23 AM

Wil, once again, very well said!


Wavey 01-28-2004 07:40 AM

Yes, Will, right on! Loren has been conveniently ignoring that fact that almost everyone makes exhaust changes along with the chip, or eventually. The scenario that he's argueing about, in which only the chip is changed, hardly ever happens! He's also only looking at maximum horsepower gains, and ignoring the greatly improved driveability of the car over the entire RPM range that is provided by one of Steve's chips. So Loren is right, but only within the tiny little universe to which he's trying to restrict the discussion.

BGCarrera32 01-28-2004 07:50 AM

Loren's world...

Wil Ferch 01-28-2004 08:08 AM


If I may....

Loren has some very valid points to bring forth, and we'd be as guilty as he is, if we continue with this ( ahem) "theme"...

I'm trying to facilitate Loren's views with others such as SteveW's, so let's try to be on our best behaviour...who might rub off ! :)

I think Loren's views also deal with unsubstantiated claims by *many other* chip manufacturers...and certainly that point is valid. Steve W has decoded a number of competing chips and has highlighted that some go to overly-aggressive advance curves that will *only* work with US grade 93 fuel..something of a rarity on the West coast, I'm told. Can also be a problem if you track the car on "hot" ambient days. So the point has merit. If you ask ( like I did) for Steve to provide a slightly "dialed-back" proposition, to optimize on US 91 Octane ( not 93 octane) fuel, then that would be a degree of additional conservatism that one can you go "more aggressive" than stock. The chip I ended up with actually is coded much like the "Club Sport" or "Cup" chip that was offered by Porsche in Europe. Oh...and you can go conservative or aggressive on rpm limits, too. I opted for 6720 instead of the 7000+ limits set by many other generic chip manufacturers.

BTW...for our international readers..keep in mind the octane rating system used in North America yields numbers about 4-5 digits lower than comparable gas rating systems used in Europe.

---Wil Ferch

Early_S_Man 01-28-2004 08:15 AM

Great work, Loren!

You are, however, wasting your time with a bunch of these guys that think their cars with Bosch Motronic (DME) don't need to have an O2 sensor hooked up! Don't try to convince them with quotes from Bosch factory publications, or Porsche publications, either!!!

dickster 01-28-2004 08:20 AM


You are, however, wasting your time with a bunch of these guys that think their cars with Bosch Motronic (DME) don't need to have an O2 sensor hooked up!
i think you'll find loren said just that in one of his posts........

Magnus Rostadmo 01-28-2004 08:43 AM

Wil , very well said indeed and I totally agree with you in your good "summary" !

.............and let`s all not act uncivilized and throw more flames at Loren to just to punish !

I think Loren has brought up some valid and unknown (to most of us i`ll guess) data.
I also pretty much have to agree in Loren`s (and Wil`s) "summary" of Porsches choices when programming their chips.
As I`ve said before i think Loren knows this stuff better than most of us and now has a fine tone in his informative post.

I hope you will continue with this lightened tone Loren, and hopefully you can provide more of this is valuable info.

Loren !
Do you have readings for the 930/20 ROW and its chips / trim-chip as well ?
If so, that will be a good answer to my Q to you in the very long "string of flaming tales"
You all have to excuse my poor English. I hope that you guys in the US understand my writing.

Peter Kelly 01-28-2004 08:56 AM


What load factor where those timing readings taken at?
Looking at a stock 1989 ignition map I would guess that your load was pretty light (25% ant most), so how is this data relevent to PERFORMANCE?

To me, performance (and improvements to PERFORMANCE) should be evaluated at WOT.

Wil Ferch 01-28-2004 05:34 PM

Good point...but let's look at this from more than one angle. WOT is great for ultimate performance verification..and chip ( or other ) upgrades can be easily seen. Let's say a 3000-6500 rpm pull in 3rd gear at full throttle. Inertial dyno.
This test, however, would tell you little about part throttle drivability...and whether "tip-in" from any cruising speed on the street would induce a smalll stumble ( say)..or not. A lot depends if the focus of the effort is a racing or street scenario.
---Wil Ferch

Wayne 962 01-28-2004 05:51 PM

I think I need to quote myself from an earlier thread:


Actually, I just read Lorenfb's complete statement, and I just about agree with almost everything he says. I have discussed this issue with Rick Clewett many times (one of the experts on Engine Management systems, and an advisor to the Engine Rebuild Book). He has thousands of hours of dyno experience programming the TEC-3 Engine Management system, and the stock Motronic system. He has told me flat out that the Motronic system is pretty darn good, and installing a TEC-3 on top of a stock engine will not buy you much at all. This statement comes from hours of comparisions on dynos. You'll be able to run more advance, if you install a knock sensor on the 3.2 and have it read by the TEC-3. This is a way to advance the timing without the fear of detonation due to poor quality gas. However, truly significant horsepower gains cannot be achieved without changing some mechanical components of the engine.

Now, changing the chip map (i.e. advancing the timing) will indeed sometimes give you more low-end torque (what is commonly perceived as throttle-response). Also, changing the air/fuel mixtures and ratios according to perceived mechanical changes in the engine (i.e. exhaust systems) and climate will allow you additional room for increases. A California car does not need to be optimized for cold weather conditions and thus can be programmed to run within a specific moderate temperature range. I'm certainly not a super-expert on programming these units (Rick is), so I'm not sure exactly what gains can be achieved from tweaking. However, Rick has stated that they are very minimal. You want to go with an aftermarket engine management system when you make major mechanical changes (i.e. displacement, cams, etc.) to the engine, so that you can custom program the system to adequately match the new configureation.

It's also a misnomer that these EFI systems require hours of dyno time. Rick has repeatedly discussed with me the 'baseline' performance of these systems. With his pre-programmed units (again, based upon his library of programs from hours of dyno time on customer's cars), he can achieve about 95% of the peak horsepower with a TEC-3 system right out of the box (no dyno time). To get that last 5% - yes, you will need several hours on a dyno, mixing and matching the exact parameters to fit your particular engine.

On the other hand, the chips do work. However, as Lorenfb has mentioned, there are tradeoffs. Increasing the timing can lead to detonation --- detionation that if not closely monitored can really destroy your engine bit by bit. The chips work partially because they cut the operating margin (between complete combustion and detonation) a bit thinner than the factory did. You must make sure that you run only high octane fuel (sometimes the CA fuel just isn't good enough) and keep a close watch for detonation when you're driving your 911. Failure to do so can hurt your engine. However, the increased timing can give you more "feel of the pants" acceleration off of the line.

Some chips also work by richening up the mixture at certain points, so that the cars no longer fit an appropriate smog profile. It's no secret that manufacturers have had to make their cars run poorly in the past in order to have them pass emissions. Some chips change this profile to favor performance over emissions. However, my original statement is still true - you can't get truly significant gains without changes to the mechanical components of your engine (early exhaust may help, but it's not really what I'm referring to here).

The bottomline? There is no such thing as a free lunch in this world. You do drugs, and your body/mind will pay for it later on. You add a chip to your car, and you will get slightly better performance, but you'll have to fill up with premium all the time, and you may risk detonation while driving. That said, SteveW's chips seem to get high marks from satisfied customers - we will be carrying them in the catalog in the very near future. For the price, a chip replacement is still one of the best ways to increase off of the line performance. BUT, you're running your engine closer to the edge, which will cause increased wear and possible damage.

There was a previously heated thread debating some of these issues. I didn't quite read it all, but these are the facts of engine life, pure and simple...

I'm not sure what all the fuss is about here. SteveW's chips obviously have many satisfied customers. I'm sure that these customers also know the increased risk that it brings to their engine. Happy customers, can't be too much wrong with that - that's why we decided to carry these chips.


Paul Franssen 01-29-2004 02:55 AM


Originally posted by Wil Ferch

BTW...for our international readers..keep in mind the octane rating system used in North America yields numbers about 4-5 digits lower than comparable gas rating systems used in Europe.

---Wil Ferch

Thanks Wil, I understand that statement to be very true. So, our (mandatory for UNCATALYZED ROW Carrera 3.2 liter) "98" octane is in fact similar to the U.S. "93" ... In other words, as soon as the government starts reducing the max. octane to "Euro-95" (the "green" stuff), wich would mean abt same as the U.S. "91" (maybe "90"?), we will NEED a new chip DOWNTUNING our engines...

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