cobalt

Agreed that the old system is very limited especially with all the advancements over the past 5 years or so.

It is not a plug and play system and we are working through all of this now. There are many things I would tackle but this I need experienced help with. I am working with some young engineers at a local shop who do a lot of tuning on all sorts of cars obtaining safe high HP numbers. This is their first air-cooled so we are having some teething problems but minor and much of it comes from changing direction mid stream or compatibility issues. It all depends on how far you want to take it. Having fun with little things like having the tach power up on start up and run to redline each time. Many things that you can do however it requires the addition of sensors and or replacement of components that aren't compatible. In my case the 993 coils wouldn't work so we switched to the AEM units and working on controlling the fans for oil currently.

I will post more soon just taking longer than expected due to other life issues.

JasonAndreas

What advancements are missing that you are using in your build? Wideband O2? COP? Even the latest Bosch Motorsport ecu's (MS7.4) are physically (relative fuel mass) based ECU (like the 964/993) that don't bother with the torque model that was used in the street ECU starting with the 996.

ras62

I dont see any need to change from Motronic unless you want to use throttle bodies. This means having an engine built to rev higher than the stock rev limit at which point the gearing is too long. Motronic can handle bigger injectors so long as the maps can be changed by someone competent.

Spyerx

This is a very broad statement and not entirely accurate. Motronic can do a lot, and made to work, but, at the end of the day its a near 30yr old computer and the industry has moved on. Advanced spark, ignition, timing, fuel control are all options that the Motronic is limited in. All of these unlock power in the motor.

For those following this, I'm PROBABLY going to hold off on the computer for now - and just do a custom Wong tune (he's local to me) since my engine mods are mild. I'm a do it all right or don't do it sort of person.

Here's a ballpark of the ranges for those who care, assuming you buy kits, don't try to assemble yourself, and have a shop do the work. These numbers can be highly variable. But this will give you an idea of the cost ranges for this stuff:

"just a tune" - about $500 - advantages: cheap, cons: generic and limited
Custom tune with motronic - about $1000 - advantages: cheap, customized for your car, mods, etc. cons: limited in mods it can support
Plug and play stand alone - about $5,000 - advantages: fully customized, modern engine control, remove barn door, modern injectors, etc. cons: some limits on sensor inputs, support for
Fully customized stand alone - 10k+ - advantages: can do anything you want. full control. full support for modern ignition control, wide band o2, ITB, etc Cons: price! tweaky

wallra

I paid 6000 for everything complete kit plug and play and I've tune it my self but I just street drive not out for every thing I could get out of the engine. I mainly wanted to get rid of the distributor, ignition wires, air flow meter.

Spyerx

Thanks, seems to validate what I pasted above roughly. Do you have a link to the kit or supplier you used? Thanks!

wallra

I got it from clewett engineering he put it together for me. but If I did it again I would go with the kit you posted. I like the vw coils better just because the Porsche coil connectors for the harness side for the coils were like 48.00 each *12 , plus the Porsche coils need holders made to keep them in. the vw coils snap on to the plugs. the only problem is #6 coil is under the power steering pump so I had to remove the pump to install coil. I want to install an electric power steering pump so I can change the spark plug without removing power steering pump.

ras62

While its obvious that technology has moved on since these systems were built, it is not easy to improve on their performance or their reliability. Making sure components such as plugs, lead etc are all in perfect condition will show bigger margins than having a faster processor. Perhaps the biggest downside to the Motronic is the use of it hexadecimal system which few tuners can master but even here modern emulators offer a solution,
Marginal changes in fueling offer no real power gains over a fairly wide ratio, the power comes from timing changes. The guy who set up my car is acknowledged as one of the best in the UK and Europe. He says Motronic is far more capable than people assume and is very difficult to improve upon. This guy has used just about all the systems out there both road and race. Suggest to him that Motronic is inferior to Motec and you would be surprised at his reply. Or perhaps not after reading this

cobalt

Compared to the protomotive modified 1996 motronic unit I can control nearly every aspect of engine management, (spark, duration, fuel, boost, knock, how and how much to retard spark, redline, signaling to warn me of engine knocking etc etc) along with a multitude of aux functions. I will now be able to run comfortably throughout the entire rpm range using 93 and if I want in the future E85 (E80) etc. Cost is relatively inexpensive.

wallra

so Cobalt your running stock ignition with distributor and spark plug wires on this system? the only thing you changed is the stock computer?

JasonAndreas

ahh, so tun-ability, gotcha!


Historically COP have not held up very well on the exhaust side of the 964, outside of a DE queen or two. On a street car that see's any usage I would be really hesitant and I wouldn't consider it all if sticking with a catalytic converter or secondary muffler.

Lorenfb

Yes so true, i.e. the heat in the engine compartment of the last Porsche air cooled engine is problematic. Even the Porsche turbos of the eighties were a good example of that,
i.e. a high rate of CDI failures. This is more problematic for daily drivers. Remember, more engine power also results in more heat loss, i.e. the engine efficiency basically remains constant.

wallra

we will see how well they hold up on my car. right now over 1000 miles and no problems. I also have headers that move the exhaust out more from the coils. these things are made for heat. I did plugs to day on a 2014 Mercedes c300 and the coil are right above the exhaust manifold. think about it the nice thing about air cooled is we are blowing air around them.

cobalt

I considered making additional changes but this is good for now and hopefully will pay for itself quickly enough.

The car was producing a fuel rich conservative 450bhp on a mustang dyno at 2650 pounds which is more than I need for a track car with short gears. I expect we will find a few more ponies with this setup but my concern was both reliability and reduced running expenses. The prior tune was guzzling race fuel so roughly $60-80 in gas for a 30 min track session with two drivers at 8 sessions a day it adds up quickly. If I use the same amount of 93 it will save me $50-60 a session and possibly more assuming ability to tune for max efficiency. If E85 ever becomes available at track or I can find a way to transport a 55 gallon drum I can make adjustments easily enough.

I wanted the ability to set the AFR and the system will maintain it as needed. Also the control over cooling fans, over boost and over revving cutouts and knock control all sold me on this change. I have other changes I plan to do some day but for now this along with brake mods and electric power steering pump (which can be controlled to run at slow speeds and then turn off) should be enough to have fun with.

Some minor setbacks but should be on the dyno tomorrow and the track in a week where we will make the final adjustments.


While on the subject anyone have the resistance curve chart for the factory cylinder head temp sensor?

JasonAndreas

Here's the voltage drop linearization curve from the ECU. You should be able to fit a curve to it using the resistance values listed in the workshop manuals? If nobody else responds with exact values let me know.