New car- Detonation - My story..

[totle]

Hi guys,

Some of you know this car, and some might have picked up that I had a detonation two days after I had it on the road.
Well here is my story.

Just want to clarify that I do not hold any responsibility towards previous owner, he has been really helpful in sorting out new parts etc.

Bought my car last year in the US. I was there to test drive and ship the car to Norway.
In January I picked it up at the port in Norway and transported it to it's new home.

Picture from the port when I picked up the car


Here is a couple of pictures in May before my detonation





During the winter month I had the front bumper and side skirts repainted due to some rock chips. I also mounted a roof spoiler with a 3'rd brake light.
Powder coated the rear calipers, fan and fan housing.

When I had the car on the road in May, I was really happy over my new car. I was holding back with boost until I was familiar with it.
I also tried to get familiar with the ECU software.
My plan was to take the car to a tuner that has a Dynapack and also are distributor of Vi-Pec EFI system. Vi-Pec is very similar to LINK that I have in my car.

On the second day I met up with a friend in his GT2 and we went for a trip.
After some time we switched cars and I was in his GT2 behind my new car.

The suddenly there was some black smoke coming out from my car. My friend turned over and said that he lost power.
He explained that he did a pull in 3'rd gear and when he went over to 4'th there was not much power.

I had my car towed home and after further inspection I found no compression on any of cylinder 1-3

Then I had to drop engine to do further inverstigation

First thing I noticed was that cam was out of position on cyl bank 1-3.


Then when I had removed cam tower I saw that on all of the three piston there was a bit fallen off.

[img]http://porscheentusiasten.com/images/bent_valves/Piston_cyl1.JPG
[/img]







Cyl 3 was the one that had the most impact, and probably caused the camshaft to rotate and shift postition due to that the piece of piston came between valve and top




After talking with Mike Bruns at JB racing he was sure this was caused by detonation.
He suspected that the right side was damaged as well, so I removed this side as well to find this.



The pistons are black due to that the engine was running some time with fat mixture due to that MAP pressure was way off and gave wring fuel table reading.

After inspection of turbo, I found that the turbine wheel also had suffered from the piece's of the pistons.

[img][/img]

Well this was not my plan to start the season in my new car.

I had to order new parts and do a rebuild.
If the engine was original, I could sort parts from my local dealer, but the engine is quite modified.


I talked with Mike Bruns again and he was really helpful in sorting out new parts.

New 98 8:0:1 JE piston was ordered (same as the engine had)
He ordered the new pistons with the top piston ring further down to get more strength on the top of the piston.

New custom valves from Xtreme cylinder heads ordered. The valves had bigger diameter that the original 930.
Cylinder tops had previously been ported and flow tested at xtreme cylinder heads.

New cartridge for the GT35r turbo was also ordered.

Instead of me having to deal with the different vendors, mike was so kind to be the interface towards the and collect the parts and ship them in one large box to me.

Can not thank enough for this good service from Mike and JB racing.

I also had some mail with Chris at Turbokraft and he suggested to do a full cleanup of engine and oil system.

While waiting for new parts, engine case was cleaned and oils system drained and cleaned.
I could not find any debris in the case or engine.

[totle]

Now while waiting for new parts, I had time to get my boat ready for the season.

I had my cylinders honed at a local shop. There was no mark in the cylinders at all.

The day was finally there when my box with the parts arrived.
Even though I know the contents of these boxes, it is more fun opening them than on christmas :-)
Yes, pure engine porn :-)




Next now was to go back to my local shop to have the piston rings gapped.

It is always nice rebuilding an engine with new and clean parts :-)

[slow&rusty]

So the problem was the EFI tune rather than the assembly of the build? Did the gauges not give readings of running lean at higher rpms and did you receive dyno read-outs and a full PPI when you bought the car.

We (sadly) all know the reputation of the shop that built the car.
Yasin

[totle]

Hi Yasin,

I suspect the EFI setup. My tuner started to build new fuel/ignition tables rather that editing the one in the system.
When he was done tuning, we compared the tables. Fuel table was too lean before and ignition table was too aggressive.
I have used the car all summer, even on some track events with no issues after the assembly.

When I used the car I was monitoring the AFR gauge closely, but could never see too lean. maybe because I was not pushing it too much.

[911nut]

Trond, I'm confused.
You never saw a lean condition while you were driving. So how did it suddenly go lean when your friend was driving? Is there a means to dial up the boost from the cockpit? Then the other bank was rich? How does that happen if you had a detonation failure?
Normally when there's detonation a localized part of the piston/head interface melts. I don't see that. I see what looks like a classic mechanical failure, where your camshaft shifted (guess we now know why the stock cam adjustment/indexing used holes and dowels vs. a slotted gear) and the valves made contact with the piston tops.
In any event, good luck with the rebuild. I suggest you source some stock camshaft cogs to prevent this from happening again.

[totle]

Hi Paul,
I was never pushing the engine too much. Told my friend not too either. Do not think he did, but hard to say what happened since I was not in the car.
I think too aggressive ignition could be the case here.
When we tuned the engine in the dyno, we saw ignition spike in the level lower that it was set originally.
It was a fixed boost spring on 1 bar

BTW Paul, I could not find any indication that the camshaft had shifted due to the adjustable cam sprockets

[totle]

here is a picture of the damaged turbine wheel

[totle]

After I got my piston rings back from "gapping" I started the assembly.

Pistons back on


Cylinder top with new valves


Engine finally back in the car :-)



My next stop now was for the Dyno and tuner.

[full quack]

Hey there,
I do not think this was caused by detonation either. Looking closely at the photo's, you can clearly see the scrape marks on the piston crowns, where the valve has impacted the piston.

Furthermore, you can see the outward crack progression on the intact section of the piston crown. There is no sign of detonation melting at all, all piston edges are still sharp, as are the edges of the fracture points. If nothing else, the fracture point edges should at least show some signs of excessive heat, but they do not.

I believe what you have here is a simple machanical failure, caused by cam index shifting, resulting in piston & valve contact.

I would at least drill & pin the cam sprockets, once proper timing has been established.

My .02 worth.

Mark

[totle]

More update..

Then it was off to the dyno and tuning.



The dyno guy was very careful when starting the tune since he knew the history of the engine.
We disconnected the hose between intercooler and inlet manifold, to start the tuning with less boost.
He started to build up new ignition/fuel tables. When he was satisfie with the settings, we connected the hose again to have boost.

We could not run that high ignition as before. We hit spike was before old settings.

As mentioned before, new tables was higher in fuel and less ignition.
I was happy with the result 505rwhp and 635 Nm torque at the wheels

[totle]

Originally Posted by full quack

Hey there,
I do not think this was caused by detonation either. Looking closely at the photo's, you can clearly see the scrape marks on the piston crowns, where the valve has impacted the piston.

Furthermore, you can see the outward crack progression on the intact section of the piston crown. There is no sign of detonation melting at all, all piston edges are still sharp, as are the edges of the fracture points. If nothing else, the fracture point edges should at least show some signs of excessive heat, but they do not.

I believe what you have here is a simple mechanical failure, caused by cam index shifting, resulting in piston & valve contact.

I would at least drill & pin the cam sprockets, once proper timing has been established.

My .02 worth.

Mark

I was not sure of this either, but right cyl bank has same issues, and this side the cam had not shifted.
I sent the pictures to different people, and they told me nit was caused by detonation.

Yes, after setting the timing, I drilled a hole and inserted a pin, just to make sure.

[TurboKraft]

Good dyno, Trond! Enjoy your Turbo. :-)

[totle]

I have used the car all summer with no issues.

Well one issue is that when I take it to the track, the engine is getting too hot.
I have good oil pressure all the time.
I have 2 oil coolers in front. One in each fenders.

I know they are getting oil flow, since I measured with a infrared thermostat.

Tomorrow I'm going to a track event again.
Any suggestions in why it is getting hot on track?

On regular roads it is constant right below 180.

BTW they are going to show the new Koenigsegg Agera :-)

[totle]

Originally Posted by TurboKraft

Good dyno, Trond! Enjoy your Turbo. :-)

Thanks Chris. I'm quite happy, but still far away from any of your builds :-)

[full quack]

Hello Trond,

Curious minds need to know......

I know you had bent valves from piston contact on the 1 side of the engine.

Did the other side of the engine also have bent valves on the cylinder that had piston damage?

The reason I ask, is that detonation will not cause bent valves, just burnt pistons.

So If you had bent valves on both sides of the engine, your problem was not detonation. It could only be attributed to mechanical failure.

Mark

[totle]

Mark, Just bent valves on one side.
Cam position was correct on right side.
Replaced all valves, since I was not sure if the part of the piston that came of had been stuck between piston and valve.

[jwasbury]

Originally Posted by totle

Any suggestions in why it is getting hot on track?

Yes...its an air/oilcooled turbo engine making 505whp and you are working it hard on the track.

Don't mean to be cheeky but more power = more heat = more cooling required. At that power level you may need to add another oil cooler to keep cool on track. Another Pelican who tracked his 930 extensively (Craig930RS) had 3 oil coolers on his car and he said he "needed all of them."

I have only 350-375 whp, just a fender cooler and I see 240 250 oil temps on track, thats with ambient air temps in the 60-70 degree range. Most people I have spoken with say that a Front Mounted Oil Cooler (FMOC) would keep my temps under control.

I've read where even liquid cooled Vette Z06s bake their oil on track...tough environment for any car, let alone air/oil cooled turbo porsches

[DSPTurtle]

That's not "cheeky"... that's just well said!

635ft/lbs of torque. OMG. That is freaking awesome! (oops... that newton meters. anyway, it's still pretty freaking cool)

[totle]

I have looked at the coolers,, and I feel that they can be moved further down to get a better flow

[911nut]

Originally Posted by totle

I could not find any indication that the camshaft had shifted due to the adjustable cam sprockets

Look closely at the adjusting slots on the sprocket pictured. There's witness marks where it was in one position and is now indexed a few degrees.
Also, you can clearly see the contact between the broken piston and the valve. There's a crescent shaped indentation on the piston top which should be a dead giveaway. Furthermore, the valve is bent from the contact.
You need to ask yourself how it was that the previous owner was able to drive the car and never blow up the engine if it was truly was too lean.
Not arriving at the right root cause may cause you to rebuild your engine more than once.