N51

Colin,

Considering all the highly modified turbos(from various tuners) running around with Motronics, can that be true?


Geoffrey and/or Colin(9M):

With Christer's latest build, I believe knocklink(sp?) was used. How would you assess its' effectiveness? If I understand correctly, unlike Motronics, it does not retard the timing but alerts the driver through a light system.

Christer

Hi

I wanted to chime in here, as someone's engine who has detonated through unintended poor fuel usage. I think I picked up some 92 Octane in Denmark or Germany even though I only use 97 or 98 octane as intstructed. It could also be that the OPC in Aarhus used 92 or 95 octane fuel when they were fixing an oil line - I have no proof though......

My input here is that anyone thinking of a Motec conversion MUST seriously consider a Knockink add on. In fact, I would urge Geoffrey and Colin to offer it as standard. I think Colin charged me around GBP400 fitted at the last full rebuild with new pistons etc. - much cheaper than GBP8K+ to fix serious engine detonation.....

I should also make it clear that I have never had any type of detonation under any driving conditions when the correct fuel type was used (and delivered!), there would indeed seem to be a healthy safety margin in the tuning.....

The Knocklink is there as a safety net, but a vital one IMHO....

38D

I am no expert in this area, but that information came directly from Jerry Woods, who has a bit of experience including racing efforts with 935s and 962s. He explained that while the sensor would be present, it wouldn't actually do anything on a modified engine because of this acoustic signature change. So I suspect that a modified turbo may have the sensor in place, but it doesn't actually do anything The only way to really test it would be to have someone fill up on 87 and then do some high boost runs -- I doubt there will be too many owners that want to do that!

Geoffrey

While Loren can be abrasive, some of his points are valid. I would never say that knock control is not as desirable for a street engine as not having knock control, however, I would argue that there are many different ways to solve the issue of preignition and detonation. I'm quite sure that the high school shop guys running Nascar engine don't run knock control on their engines, but rather take the same approch as I do. I would very much like to have a clientelle that would pay 40k for knock control to be implemented properly, and will gladly do it with the newest MoTeC ECU and their available knock control module. But I don't. Even if you employed a Motronic ECU, you still need to revisit the knock control since the engine has changed, and you still have other issues to deal with when trying to convert a street system to support a higher output racing type engine.

I'm not the only one who uses this approach either. Here is some text from an article in Race Engine Technology magazine where they have a detail look at the Judd 5.5 litre Le Mans Engine.

I believe I'm in good company and am comfortable with my approach. I have not yet had one failure due to knocking, including my past 911 turbo engine, the Grand Am engine I did for Mazda racing, the 996GT2 engine with variable camshafts and drive by wire, the dual VANOS BMW M3 S54 engine, Ferrari V8, Alex Job 993RSR, 993GT2s, Doran Daytona Prototype with 996tt engine, ETC...

Theory is one thing, cost constraints and the real world environment is another. This is the only comment I'm going to make on the subject of knocking. If someone has developed a Motronic solution with knock control etc, please start a thread on the before and after results. I'd be happy to see and discuss them. To date, I've not see them other than John Vitesse's MAF conversion.

DrJupeman

Damn, now I feel challenged to try to get you to make another comment about knocking.

NineMeister

I faced the realisation some time ago that if there is any thread on Rennlist extoling the virtues of a succesful Motec conversion of any Porsche, it is inevitable that Loren will throw in his "Motec does not have Knock Control, Motronic does therefore it's better" trump card. I'm not going to knock (sic) Loren for his beliefs and opinions as it is his right to have them, however, aside from the subject now being extremely tiresome, the facts are that for real world engine tuners (like me, Geoffrey & others) retaining Motronic is not a viable cost option with the type of modified engines that we work on. If it was, why would Bosch now go to the trouble & expense of producing their own motorsport ecu's when they could just write a software package to map the standard ecu? The real answer is that they have seen the huge potential sales of aftermarket ecu's and want a piece of the pie.

The Motec solutions we offer have no knock control, but since the engine (as Mr Judd rightly says) is tuned to avoid the onset of knock under all running conditions, the performance results achieved are no worse for this limitaion. As Christer rightly points out, once you chose the aftermarket solution, if you are worried about the lack of the safety net that knock control (in theory) offers, you could cheaply fit a rudimentary knock monitoring system that will at least warn you of a potential problem. We don't offer this as standard as the unit itself is a little ungainly and has to be sat in the line of sight on the dash.

warmfuzzies

As a rudimentary question then, would knock link or knock control be enough to stop or alert the driver to a detonation issue, If the wrong octane fuel had been inadvertanty used.

Kevin

shockm

Anyone know any good "knock knock" jokes?

Christer

I actually have complete faith in 9M's ability to tune the car to a safe level where *if the correct fuel grade is used* then there will be no problem. As I am not a racing team where the fuel can be precisely tested and verified prior to usage, I just go to a Shell station (or similar) like everyone else where the QC could be slightly patchy - and that is why I strongly recommend that Knocklink is used. I had some 25-30K miles of happy motoring before I hit some bad fuel, and a GBP8.5K bill became a reality. This was not 9M's fault - or mine for that matter - it was just that 0.5% chance of getting some fuel that is actually a few octanes lower than it should be.....

Colin, I actually think the installation on the steering column you did is not at all ungainly - I would still suggest you offer as standard - unless of course you think the Knocklink module is of no use - in which case perhaps we should be having a different conversation?

In any case, I don't want to be causing any doubt over the ability that 9M and Geoffrey have - its just that there are some factors outside their and our control that could affect your engine and I believe that it is at least *prudent* to consider it - even though I may have been monumentally unlucky to have hit some bad fuel.......or was I? How many cars are run without Knock monitoring system these days? Even my 1997 BMW can use anything from 91 to 98 Octane.....

Its just a heads up - and to point out that it is available if you want a safety net when tuning your car in this way.

springer3

I applaud Geoffrey for posting this. His dyno runs are credible, and a lot of great information got posted. He never concealed the fact that he would sell you one. Well done.

I have run into contaminated or low-octane fuel twice. The events were 20 years apart, but it does happen. With good 93 octane in the tank I drove with the Hammer counting knocks on a hot humid Atlanta day with the AC on full. I had to deliberately floor throttle at low RPM while climbing a steep hill before the knock counts went into the hundreds and the ignition retard activated. The car immediately became a slug. Knock was barely audible before the retard kicked in. That tells me that with good fuel and normal driving, the stock 964 does not rely on knock control. I am happy the knock system is there in case I buy bad fuel or someone stupid drives the car. I would not worry too much about the lack of knock protection, but I would keep my ears tuned and immediately change driving style if I heard any.

N51

Knock Knock.

Who's there?

Knock sensors.

Knock sensors who?

Knock censors dialogue.


Shockm,

All the best to you and an interesting build. Since your modifications, have you weighed the car?

NineMeister

In all honesty, for such a relatively low cost system I am truly surprised at how well the Knocklink works at giving an indication of the onset of knock when it is "tuned" to the noise of the engine. As mentioned, the only downside is that it is a small square box which has to be positioned in the normal line of sight so that you will definitely see the warning lights flashing if it detects additional noise, on the 911 this does not give you many options. The installation could be improved if we mounted an LED rail next to the rev-counter and remotely mounted the box, but that would cost too much in time to do on a one-off basis.

The reason we don't offer it as standard is that in 99% of applications it is not necessary, however the cynic in me also thinks that it some people would then infer that it as an admission that the system fitted is not up to the intended purpose, which is definitely not the case.

Lorenfb

"With good 93 octane in the tank "
"That tells me that with good fuel and normal driving, the stock 964 does not rely on knock control."

Right! And:

1. A fully stock engine, i.e. no high CR, no "pushed" timing, etc.
2. Using a higher octane than Porsche recommended (91 - R/M 95/85).
3. An engine management system designed and FULLY tested under
all possible driving conditions, i.e. An extensive Porsche/Bosch engineering
staff & equipment with a large development budget.
4. Normal driving (exclusive of the track)? But to a Porsche owner, what's that?
5. Good fuel? Always driving/staying close to a "good" known gas station.
When even that doesn't always guarantee "good" fuel.

Bottom line: An engine developed without knock sensors will basically never
produce maximum torque, i.e. because of the compromised tuning, and will
always have the risk of detonation.

shockm

Thanks, have not weighed the car yet. I'm guessing around 2800.

sturm

I think the possiblility of getting bad fuel has increased along with the prices of gasoline. Less people are using the expensive stuff (high octane). I took on a splash at a station and hit the freeway onramp hard and heard the pinging at full throttle. I've got stock Motronic (not a stock engine though) with a 2 yr old knock sensor.

So what happened? Did Bosch/Motronic fail me? Aftermarket chip not compatable with the knock control? Paid $4.70/gal for water?

Subsequent fill-ups have been fine; or at least I can't hear it!!

white rsa