[Elarson]

A recap of Bowling Green and what we've learned.

Run #1...6.241 record. Lit on all 8 cylinders but detonation in cylinder #2. Burned the ground electrode off the spark plug but it was still firing. So the MSD 44 amp mag can jump at least an effective .135" gap. Bent the wrist pin (1.095 pin diameter). Looking back at the data, I can see that we were losing more oil pressure than normal, late in the run. It's normal to drop off some due to warming and diluting the oil with fuel.

Run #2 Oil pressure was lower than normal after firing the engine. In hindsight, we should have aborted the second attempt. In the future we'll know that we HAVE to have 150 psi at idle or else we don't run.

Car launched as hard as the first run, lit on all 8.
At 0.53 seconds, cyl #6 drops.
At 1.05 seconds, cyl #5 drops.
Somewhere around 1.2 seconds, rod bearings #5 and 6 spin and rip the caps off the connecting rods. Shrapnel begins to fly around crankcase.
At 1.29 seconds, a chunk of shrapnel wedges a cam lobe against the block, shears cam key, engine quits running (but is still windmilling). Some intake valves now hung open.
Next revolution, the mag fires and the spark in the cylinders with open valves burns up into the intake and bangs the blower.
At 1.39 seconds, blower explosion pressure peaks at 69 psi.
Blower case is broken into 4 pieces
Note that the whole failure sequence took less than 1 second.

Now the good news.

Pistons in the other 6 cylinders have no skirt cracks, validating that looser piston-to-wall clearance was the right move.
Iron IA-2 block looks like it needs cleanup in the 2 scuffed cylinders and it's probably still useable. That will be a winter project.
If we wouldn't have been detonating cyl #2 in the first run, it would have been even quicker than 6.241.
SFI 14.3 blower restraint contained the blower explosion; preventing launching the case sides thru the body and into the grandstands.

Eric

[Kevspontiacs@aol.com]

Wow. Talk about data acquisition.
Glad it wasn't worse.

[GTOGEORGE]

Originally Posted by Elarson

A recap of Bowling Green and what we've learned.

Run #1...6.241 record. Lit on all 8 cylinders but detonation in cylinder #2. Burned the ground electrode off the spark plug but it was still firing. So the MSD 44 amp mag can jump at least an effective .135" gap. Bent the wrist pin (1.095 pin diameter). Looking back at the data, I can see that we were losing more oil pressure than normal, late in the run. It's normal to drop off some due to warming and diluting the oil with fuel.

Run #2 Oil pressure was lower than normal after firing the engine. In hindsight, we should have aborted the second attempt. In the future we'll know that we HAVE to have 150 psi at idle or else we don't run.

Car launched as hard as the first run, lit on all 8.
At 0.53 seconds, cyl #6 drops.
At 1.05 seconds, cyl #5 drops.
Somewhere around 1.2 seconds, rod bearings #5 and 6 spin and rip the caps off the connecting rods. Shrapnel begins to fly around crankcase.
At 1.29 seconds, a chunk of shrapnel wedges a cam lobe against the block, shears cam key, engine quits running (but is still windmilling). Some intake valves now hung open.
Next revolution, the mag fires and the spark in the cylinders with open valves burns up into the intake and bangs the blower.
At 1.39 seconds, blower explosion pressure peaks at 69 psi.
Blower case is broken into 4 pieces
Note that the whole failure sequence took less than 1 second.

Now the good news.

Pistons in the other 6 cylinders have no skirt cracks, validating that looser piston-to-wall clearance was the right move.
Iron IA-2 block looks like it needs cleanup in the 2 scuffed cylinders and it's probably still useable. That will be a winter project.
If we wouldn't have been detonating cyl #2 in the first run, it would have been even quicker than 6.241.
SFI 14.3 blower restraint contained the blower explosion; preventing launching the case sides thru the body and into the grandstands.

Eric

Well my wife and I saw both passes sounded great ......looked awesome! For a PONTIAC!!! LOL! Great talking with you guys.......we had FUN!



GTO George

[Gary H]

Sorry for all the damage. Glad it didn't totally destroy the engine though. Will you miss Norwalk?

[Elarson]

Trying really hard to be ready for Norwalk. New aluminum engine should be ready but we also have repairs to the body and tin that we're dependent on our chassis guy to fit in to his schedule. Lots to do and the calendar is whipping by fast.

Eric

[Elarson]

Originally Posted by GTOGEORGE

Well my wife and I saw both passes sounded great ......looked awesome! For a PONTIAC!!! LOL! Great talking with you guys.......we had FUN!



GTO George

Really enjoyed talking to the (2) of you.

Eric

[Bob with the 66]

Originally Posted by Elarson

Trying really hard to be ready for Norwalk. New aluminum engine should be ready but we also have repairs to the body and tin that we're dependent on our chassis guy to fit in to his schedule. Lots to do and the calendar is whipping by fast.

Eric

I hope you get the Boss Bird back together for Norwalk, your part of what makes the event great. Really fast Pontiacs!

[JSPONT]

Awesome info, I know it helps for the next time. Why do you think only #2 cylinder had detonation?

[Elarson]

Originally Posted by JSPONT

Awesome info, I know it helps for the next time. Why do you think only #2 cylinder had detonation?

Most of the work on the tuneup centers around getting the cylinder stagger correct. Our tuner has had the overall engine fat to be safe. Run #1 was a bit leaner (overall) than the previous run and cyl #2 was a bit too lean. We richened that single cylinder for run #2 and no more detonation.

On this engine and the Grocery Getter engine, cylinder #2 has always wanted to run lean; due to acceleration moving fuel toward the back of the plenum. We have WAAAY bigger jetting in that one and we were only a couple sizes away from being spot-on.

Eric

[JSPONT]

Originally Posted by Elarson

Most of the work on the tuneup centers around getting the cylinder stagger correct. Our tuner has had the overall engine fat to be safe. Run #1 was a bit leaner (overall) than the previous run and cyl #2 was a bit too lean. We richened that single cylinder for run #2 and no more detonation.

On this engine and the Grocery Getter engine, cylinder #2 has always wanted to run lean; due to acceleration moving fuel toward the back of the plenum. We have WAAAY bigger jetting in that one and we were only a couple sizes away from being spot-on.

Eric

Just trying to learn a little more, since most engines are "blue printed" why do you think some cylinders run leaner than others with the same charge going in. On a small scale I have to tune to my leanest cylinder and let the others run fat. I have a blow thru carb set up.

Good luck with the new set up!! I guess it's all one big learning curve.

[GTOGEORGE]

Originally Posted by Elarson

Most of the work on the tuneup centers around getting the cylinder stagger correct. Our tuner has had the overall engine fat to be safe. Run #1 was a bit leaner (overall) than the previous run and cyl #2 was a bit too lean. We richened that single cylinder for run #2 and no more detonation.

On this engine and the Grocery Getter engine, cylinder #2 has always wanted to run lean; due to acceleration moving fuel toward the back of the plenum. We have WAAAY bigger jetting in that one and we were only a couple sizes away from being spot-on.

Eric

On my engine the back cylinders run lean......no 7 being the worse.



GTO George

[Tom Vaught]

Originally Posted by JSPONT

Just trying to learn a little more, since most engines are "blue printed" why do you think some cylinders run leaner than others with the same charge going in. On a small scale I have to tune to my leanest cylinder and let the others run fat. I have a blow thru carb set up.

Good luck with the new set up!! I guess it's all one big learning curve.

Unfortunately it IS NOT "the same charge going in" in reality.

Blower configuration and manifold can have an effect on which cylinders get less fuel vs others. In George's case with carburetors above the supercharger he is forced to accept that some fuel from #7 Cylinder will be robbed by the #5 cylinder unless he has a Ford Firing order on his engine. Considering that he hates Fords that is a possibility.

In Eric's engine case they have Nitro Injectors that are close to the inlet runners of the head. In their case they can tune the injection closer but that still does not account for some fuel cross-talk between the cylinders and the fuel from the front of the engine moving toward the rear of the engine under acceleration.

So it depends on the induction set-up, the way it is tuned, the fuel used, and other things.

We have some cool real time video of how fuel (even with port injection) moved around in the induction system. Direct Injection is a better deal BUT DI injection currently has limits on how much fuel you can run thru a DI injector.

Sorry to hear about your latest situation but congrats on 6.241 et run.

Tom V.

I told a Chief Engineer "Big Boss" (vehicle program guy) "The engine is trying to tell you something! Are you willing to listen?" "...or are you going to roll the dice".

[mike leech]

Sorry to hear. Hope you guys make norwalk!

[Elarson]

A few interesting pictures. One during the blower explosion, one immediately afterward and what's left of #5 and #6 rods.

Eric

[Tom Vaught]

A little JB Weld and some decent Bubble Gum and you will be right back in business again.

You guys are really pushing the limits, for sure. Hang in there, Guys!

Tom V.

[Elarson]

It's an awesome science project and hopefully other folks can get some inspiration and learn some things from us stretching the Pontiac envelope.

Eric

[67GTO4SPEED]

Originally Posted by Elarson

A few interesting pictures. One during the blower explosion, one immediately afterward and what's left of #5 and #6 rods.

Eric

Man! That first picture with the body all distorted is wicked! That must have a scary moment inside the car!


I have to say I appreciate your and Mike's updates and the detailed journey of running the Boss Bird. I hope it is back together for Norwalk.

[Elarson]

Controlling that monster is a busy job. No time to be scared regardless of banging the blower, setting it on fire etc.

One of my other goals with all the explanations is to give everybody a better understanding of how a nitro engine works. I want you to be smarter than your Brand X buddies when they want to talk about the Big Show cars.

Eric

[Tom Vaught]

Thanks very much on the free lessons, Eric.

Tom V.

[twooldgoats]

Originally Posted by Tom Vaught

Thanks very much on the free lessons, Eric.

Tom V.

Free to us, anyway.

Jim