Performance Improvements for All Porsches
 

There has been a lot of discussion about performance improvements the result
of performance chip installations. Many have indicated that a noticeable
improvement occurred to the throttle response with an idle increase. It's a
fact and no mystery that small increases to the ignition advance timing will
make small but noticeable performance increases whether it be a 911 3.2
or an earlier 2.2 engine. These increases could hardly be called dramatic,
though.

Any engine will show an improvement in throttle response, if the ignition
timing is advanced over the stock specifications. All performance tuners
know this. As an example, a 911SC with a conventional distributor advance
curve will show an improved throttle response with a 3 to 5 degree increased
ignition advance over the stock setting. There is a tradeoff, though, as you
might expect. As the ignition is advanced, higher octane levels are usually
required to avoid pinging especially in hot weather and under heavy loads,
e.g. hard acceleration. That's why all Porsches beginning with the 964
have knock sensors to allow for max timing without pinging as different
grades of fuels are used under different driving conditions. Furthermore,
pinging/detonation is not always perceptiveable to the driver.

As a personal example, I've increased the advance timing on my Nissan V6
about 5 degrees over stock. The engine does feel a little more responsive,
but not a dramatic improvement. The bad news is that I have to use a 91
octane fuel, especially in the hot weather. In the winter, I can use a
89 octane without a pinging, but there's still a little pinging with
the engine under heavy loads.

Most Porsche DME ignition maps are very close to the max allowable ignition
advance without pinging under all load and weather conditions. It's very
questionable whether a small 3 to 5 degree increase in advance timing
can be achieved without a resulting octane increase either by a higher
octane level, e.g. 93 to 100, or an octane booster and still avoid pinging
and notice an improvement in throttle response. Therefore, each small
increase in advance ignition timing will require higher levels of octane rating.
This is of a lesser problem for lower compression engines than for Porsches,
as is the case for my Nissan V6 versus my '88 3.2.

The bottomline is that all Porsche engines can be advanced in ignition
timing to achieve a performance improvement. To do this is no great
accomplishment over what Porsche/Bosch programmed into the DME or
determined for the mechanical advance curve on the 911SC. Porsche/Bosch
did not leave any "undiscovered areas" to be "tweaked" by performance
chips. It's just a matter of what tradeoffs you're willing to make
for that small improvement.

Here it goes again :D .........

Some Info on Engine Management and Chips...
 

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...

-Wayne

Great information!
 

I think what Loren has written here is top notch. Its informative and factual. I never thought about the pinging issue (although I run 91 or better octane anyway). It makes sense that if you are running a performance chip you prolly want to run high octane to get the performance you just paid for.
It might be a wise thought to ask people who make performance chips (you know who you are) to put a "warning label" to explain this info to the buyer. Sorta like the label that comes with the toaster that tells you not to use it in the bathtub...

P.S. If you run a chip on a 3.6, there is very little chance that you will harm the engine, as these engines have knock sensors that sense detonation. The computer will then realize that your gas isn't good enough, and back the timing off, saving your engine from further detonation. The Motronic 3.2 system does not have this capability.

-Wayne

Loren,

This is an excellent thread. Great post. It's intelligent, informative, and helpful without one word of condescension. Keep em coming!

When I was researching my conversion, I had considered adding an SOK supercharger to my 3.2. A shop in Knoxville mentioned a marine knock sensor that could be installed on a 3.0 or 3.2 to prevent detonation when running a supercharger without lowering compression. I wonder if this is a viable option for 3.2 owners that want to run more aggressive timing curves? Maybe another new product for the catalog Wayne?

Loren, please proceed and explain for the newbies: what should a "Chippie" look/listen for that will tell them that they have a detonation problem that will hurt the motor?

Has the consistent quality of pump gasoline improved in fifteen years?

Unfortunately, on these noisy 911 engines, it's sometimes very, very difficult to hear and/or tell. I have trouble listening for it on some engines...

-Wayne

From what I've read, the amount of energy in a given quantity of gasoline has steadily decreased over time.

I'm not familiar with what they are talking about. Even if you were able to install a knock sensor, the computer doesn't have the programming to accept and monitor the signal.

On the 3.6 engines, the knock sensor is a vibration sensor that sits on the top of a bar that is attached to the tops of the cylinders. Supposedly, this arrangement doesn't work too well though, and the bar sometimes breaks from vibration fatigue. On the 933 airplane heads I had (from a 3.2) there were knock sensors installed into the head themselves. However, since Porsche went with the bar system on the 3.6 engines, I would suspect that the internal knock-sensor inside the head might not have worked as well as they thought.

Come to think of it, those airplane motors were turbocharged CIS systems, that cannot utilize a knock sensor. I wonder if it was simply tied into a warning light inside the cockpit - I don't know...

-Wayne

Although I'm not a gasoline expert, it is my understanding that higher octane fuels have a lower energy density (not sure if that is the right term for gasoline) than lower octane. The higher the octane, the greater the "pre-burned" fuel. The higher octane fuel with lower energy, ignites and burns slower (what you want) for better and more consistent, even combustion pressures in your combustion chamber over the burn cycle.

-Wayne

Mike, can you check on it? If you want, give me a number and I'll call them and see what that is all about.

Por_sha991:

Thanks for the feedback.

Wayne has basically covered all the caveats, not much more can be added.
If I had purchased a chip, I would closely monitor the engine:

1. listening for pinging during hot weather and under hard accel
2. possibly moving up in an octane number
3. checking plugs for abnormal mixture or white particles (metal)

It's not easy to detect a pinging/detonation. Just be aware that it MAY
occur.

J&S make some impressive knock/ignition control units. They are used on some top flight race cars.

They can be tailored for individual cylinder ignition/knock control, and let the engine run at advance settings at the limit, while detecting and controlling detonation

no affilitaion yadda yadda

Thanks Loren and Wayne for some excellent information! I've always understood the calculated risks us "chippers" were taking but concluded that I would always run 93 octane (as I always have in my sports cars), and take my chances. Thanks again for the 'tone' of this post...quite refreshing :)!

Re: Some Info on Engine Management and Chips...
 

Dude, what exactly are you trying to say?

And what's with all the spiders on the bbs all the sudden?

I had Tyson check my timing on my SC and he said it was advanced less than two degrees.
But I have a habbit from driving a big diesel of not slipping the clutch at start off. I just let it out with out to much RPM and I have heard a ping then once in a while.
I aways burn at least mid grade and use to just burn nothing but high grade so maybe I'll go back to Hi or change my habbits. I never hear it ping on a grade under full power.

Here's octain if you need it


http://forums.pelicanparts.com/uploa...1074127537.jpg
This pump was at Mitchels Pit Stop in the city of Orange $495. for 110.
The little readout screen on the pump had a 911 on it.

Hmmmmm....I didnt realize that running none premium fuel was even an acceptable option for a non-chipped car. The owners manual for my '87 recommends 92 Octane. In Houston we have 93 octane, so that is what I use.

Glad to see that Wayne has chosen to make Steve's Chips available through Pelican Parts. There are quite a few performance chip manufacturers on the market. It says alot about Steve's talents that his product was chosen.

I would have to say that the single greatest influence that lead me to purchase a performance chip came from Waynes engine rebuild book. To quote,"If you are running a stock 3.2-liter engine with the stock Motronic injection and exhaust, the best upgrade you can perform is to install an after-market DME chip." The paragraph goes on to warn about potential detonation as stated in this thread.

Very:cool:thread!

An ECU managing spark and boost control could make use of it.

Loren, a much better post I must say!

Jeff

Good point - those motors did indeed have eletronic ignition and two separate ignition systems (mandated for airplane engines).

Pinging can often be heard under load at WOT throttle, not necessarily off-the-line acceleration...

-Wayne

So in relation to this I'm thinking about installing an ECU for ignition on my Hi compression 2.4. I've heard that aircooled engines are "noisy" and won't work well with the detonation sensors. How well would a ECU with anti-detonation control work with this motor?

A very good post and is one of the reason I hope to go with an ECU for ignition.

I've given a little thought to the preignition issue myself, particularly in light of the louder intake/exhaust on my car. While I don't think I've ever heard the car knock, I'm not sure with those mods I would. I am religious about using 91 or 93 octane and not using large throttle imputs at low rpm/high gearing.

This post is one of the reasons that this forum is so great.

The effectiveness of your system will depend entirely on the effectiveness of your knock sensor. Tim is right - it's difficult to sense knocking on these engines. You might want to ask Rick (www.clewett.com) what sensor he uses on the earlier cars - I don't know the answer to that off the top of my head.

-Wayne

If you rely on your ears to detect detonation (sub-audible or the audible kind), your bank account is at serious risk. :)

I cannot tell you how many SC, Carrera, and Turbo engines I have opened up to find broken rings and trashed pistons from detonation. The owners' all told me they NEVER heard a thing.

Air-cooled engines require a margin against detonation as that threshold is dynamic, not static.

Amen, a well written, informative thread.

As Steve has said, a "MARGIN" is required. This means that you just can't
"push" timing arbitrarily to get a desired throttle response. For those that
fail to understand, I'm sure he'd be more than willing to re-do those motors
that had lacked the "MARGIN".

Even better, in the case of the NBD 3.6 chip, is that you can move between stock settings and performance settings by reaching under your seat and toggling a switch. That way, if it's hot or you're running plain old 91 octane gas, you can run on the stock setting. But on days where you want more, you can mix in five gallons of 100-octane, and switch over to the more aggressive side of the chip. I think it's a smart way to engineer a performance chip, since it adds a little insurance on top of the knock sensor.

Great thread, by the way. :)

i'm a little confused here guys so help me out. i thought this was common knowledge.

i thought the whole point of the aftermarket chips was because usa cars and row cars ran different chips and some gains were there to be made. i also thought they were used to match engine mods to fuel/ignition - like swapping out the cat or something.

Well, the USA and European cars did run different chips. Why? The only reason I know of is because of smog regulations. So, whereas the European chips were designed and mapped with a less restrictive set of requirements, the USA chips had to restrain the engine under certain circumstances in order to satisfy smog requirements.

You're right - there are gains to be made by switching, however, they are somewhat minimal in the grand scheme of things. You're forgetting on the 3.2s that the Euro Pistons & Cylinders were higher compression than their USA counter parts. While not a major difference, it does help account for HP differences between the two types of engines.

On your second question, you're also right. The chips can be used to modify the computer to match certain modifications to the engine, like changes in the exhaust. However, again, these gains are many times incremental, not monumental. Most chips get most of their "throttle response" from advancing the timing, which then (as we have mentioned) increases the risk of detonation.

-Wayne

wayne, thank for that. yep, i unknowingly bought a usa spec car - in europe!!

noone has claimed monumental increases in hp with a chip. i would think anyone that has taken any interest in the chips on pelican would have realised that the gains came from ignition and fueling changes. surely its down to the chip supplier (their responsibility) to ensure that detonation/pinging isnt a problem, and to advise if high octane fuel is required.

i am sceptical of "seat of the pants" claims made by a lot of people around here (but if they feel it good luck to them!) but still dont see anything new here.

There is a tremendous leaning towards the placebo effect when you measure by the seat of your pants. I've sold Bursch mufflers to 914 owners who swear their car is 15 HP faster with it installed. In reality, the muffler is heavier than stock and offers no performance improvement (beyond a better sounds). But I don't try to convince them otherwise.

I once tried to explain the truth to a friend of mine who insisted that his car was faster on a full tank of gas. Technically, it's the other way around, but the mind is a strange thing that way.

-Wayne

Wow, what a revelation.
You mean to tell me that if I advance my timing I will get more horsepower but I'll have to run a higher octane? Who would have thunk.

Am i also to understand that instead of an engine running between 14.6 and 15 to one air to fuel ratio by weight I can get more horsepower if I map the fuel injection so that it goes closer to 12.8 to one at full throttle but my fuel economy will suffer?
That is just too much to absorb. How come no one has ever come up with this information before now? (yes, I am being overly sarcastic, it's been a long night shift).

I once listened to a guy who tried two different grades of gasoline while his 3.6 was on a dyno. Predictably, the engine made a little more power with the high-octane gas. His conclusion was that high octane gas releases more power. More BTUs. I did not have the heart to tell him that the additional power came from the increased ignition advance that the engine automatically applied when it noticed that the high octane fuel was more detonation-resistant.

Another reason the stock Euro chip is different from the US chip is that in the 80's high octane gasoline was not as readily available in the US as it was in Europe. Porsche dialed down performance to account for the probability that high octane gas would not be used.

Running a stock chip with a stock exhaust on 91 octane or lower makes perfect sense. The factory did their homework to achieve performance in this scenario. The point of changing a chip is to recognize the fact that 93 octane is now readily available in most places (allowing for changes in timing as the risk of detonation decreases) and to match engine characteristics to other modifications (i.e. exhaust).

Factories have to produce a one-size-fits-all solution, tuners don't. I appreciate the friendly tone here, but hasn't this all been covered here before?

An additional "danger" with some of the aftermarket chips is the less than responsible rev limit reprogramming. I've used a few different chips over the years and some chip makers actually eliminated the limiter. Not good.

Some posters consider this thread somewhat trite info. The reason for initiating
this thread was to inform the many, it appears, that really don't understand the
basis for the performance improvement from most performance chips and the
caveats associated with those chips.

Most may think that Porsche/Bosch lacked the wherewithal to really gain max
performance and some computer whizs have been able to "hack" the DME
and "discover" some hidden horsepower. As this thread should now convey,
this is not the case. For those that already had this insight, I apologize for
posting something that seems obvious to others.

Not more peak HP, just more lower end torque, or throttle response...

-Wayne

With more torque comes more HP, as HP = Torque X RPMs. If at the same RPM
the engine produces more torque, you get more HP at that RPM. We're all basically
talking about the same things and trying to apply a little reality to performance
improvements.