detonation ?

[quint22cp]

After a 16 month rebuild I have finally reunited my car with it's rebuilt engine.

Firstly I'd like to thank all the guys on here who helped answer all my questions on rebuilding the engine with particular thanks going to Charles Navarro, Mike @ MBEngineering and John Midlton.

My engine mod's are many including a capacity increase from 3.2 to 3.5, and while I twin plugged the heads I am not yet running the second plugs as I haven't connected up the SDS system.

I want run-in the engine for a 1000 miles on the original Motronic before connecting the SDS system and getting it on the rollers and tuned.

With it's twin out Dansk exhaust, induction roar, the fan and all the noise from the valve gear how do I know if the engine is pinging (pinking) or worse still detonating ??

Is there a break-in procedure that avoids damage ???


In thanks, I have made all my own Porsche special tools and done all my own machining including DIY twin plug. If anyone needs help with tools or advice on machining I can gladly share my designs and experiences.

Pete

will post some pic's soon

[ChrisBennet]

The simple answer is no, you won't be able to hear the detonation.

Maybe you could have a custom chip made to retard the ignition enough to drive it easy, I don't know. I don't think you will be able to get away with just using the Fuel Quality Switch on the DME to retard the ignition but it might work if you just need to move the car in your driveway.

-Chris

[quint22cp]

Thanks for the reply.

I've read about the DME fuel quality switch somewhere in the past but now I can't find the thresd.

Where is it and how do I adjust it ?


Pete

[ChrisBennet]

Originally Posted by quint22cp

Thanks for the reply.

I've read about the DME fuel quality switch somewhere in the past but now I can't find the thresd.

Where is it and how do I adjust it ?


Pete

Steve Wong had it on his web site somewhere

http://www.911chips.com/


I know you are probably anxious to get your car on the road, but please, please get more info on this (from people like Steve Weiner) before you go tearing across the countryside destroying your newly rebuilt motor. This is not the sort of situation where you want to "wing it".


-Chris

[cnavarro]

Pete, congrats on the rebuild.

The direct link to the settings for the motronic on Steve W's site is http://www.911chips.com/fuelsys.html

What final compression ratio did you end up with and what cam are you running?

You could also run a true octane booster if you think you might detonate, just for break in:

http://www.torco.com/cart.php?m=product_detail&p=136

Were you planning on using knock sensing in the SDS? You could always hook up an msd knock indicator to at least get a visual on whether or not you might be detonating:

http://www.msdignition.com/tool_8.htm

Another excellent stand alone system which I would imagine would also work with the motronic would be the J&S Safeguard:

http://www.jandssafeguard.com/

[quint22cp]

Hi Charles,

Calculated comp' ratio to be 10.3:1 but it's difficult measuring piston dome volume on those JE's, plenty of opportunity for error.

I am on DC20 cams.

Here in the UK we get 98 (RON) gas so this should be suppressing knock.

Thanks for the links to the knock sensors I will see about getting one.

When I finally get the SDS connected, firing on all 12 plugs, and the car is on a rolling road, giving it's all, how do you know you've got detonation ??? when you see pistons !!!
Do the rolling road have a knock sensor ? never saw one on last time I was there.