Bearings - Fuel Starvation is BAD!

[inastrangeland]

Brendan,

Take a hard look at the cylinder wall and move the piston up and down. If you see a vertical scar on the cylinder wall, odds are you collapsed a piston. I had this exact situation where the dome of the piston looked OK. The vertical scar comes from the top ring protruding due to the collapsed ring land.

[Brendan]

There are small surge tanks you can install inline. Here's an example:

http://goodsie.com/store/gutenparts/fuel-reservoir-e30

I do think the stock location is ideal, but it is subject from damage from below there (Not sure about yours, but my tank has a big dent). Mounted in the rear is a crumple zone, but with a real fuel cell with bladder, I don't think this should be an issue. Did you see the pictures of the rear end of the Bimmerworld car that went into the wall at 100 mph + with a trunk mounted cell? I figure if the pros mount it there, I shouldn't be worried about it. Check it out:

http://www.atlinc.com/racing.html

Regarding your warning light - I should check my logs, but I thought my fuel pressure dropped to below 35psi every time the throttle closes (due to the vacuum reference). Also, in terms of not getting starvation - what are you running for tires? I never had a problem before running RA-1's, but my car has gotten progressively lighter, I was running new V710's, and I have an AST coilover suspension. I would suspect you're fine until you get to a certain point where the G-forces you're making cause the issue.

[Brendan]

Brendan,

Take a hard look at the cylinder wall and move the piston up and down. If you see a vertical scar on the cylinder wall, odds are you collapsed a piston. I had this exact situation where the dome of the piston looked OK. The vertical scar comes from the top ring protruding due to the collapsed ring land.

It looked fairly mild - but I'll check it out. Thanks for the heads up.

[christsay]

The accumulator Guten is selling is a standard VW part:
533 201511a
http://www.rmeuropean.com/Part-Numbe...N_A58C52C.aspx

RM Euro is out of stock, I like the guys at Guten but $70 is a big much...

-chris

[Ironhead]

Regarding your warning light - I should check my logs, but I thought my fuel pressure dropped to below 35psi every time the throttle closes (due to the vacuum reference). Also, in terms of not getting starvation - what are you running for tires? I never had a problem before running RA-1's, but my car has gotten progressively lighter, I was running new V710's, and I have an AST coilover suspension. I would suspect you're fine until you get to a certain point where the G-forces you're making cause the issue.

Well, I am running a 4-bar FPR, so 35 PSI works as a threshold for my warning light. Obviously the ticket is to set the warning light just below the lowest fuel pressure you see when the motor is running.

I am currently running Toyo R888s.

[Jake]

I always assumed a mid mounted fuel tank also had less affect on handling variation as fuel level changed compared to mounting it further away from the CG.

Jake

[Brendan]

This forum has me obsessive compulsive. The good news, pretty sure my engine is fine now, there's just one scratch I wish wasn't there. The bad news, made a bunch of extra work for myself by pulling the cylinder head after work last night.

http://www.smugmug.com/gallery/24913853_q8Xp4L







Cyl #2


Cyl #1 - the one scratch I was concerned about through borescope. I can barely feel this with my finger.


Super-size link to cyl #1 picture
http://photos.smugmug.com/photos/i-S...SCvhPSQ-X3.jpg

[inastrangeland]

Well, at least you know now. How does the piston look? As long as the ring lands are in good shape, no problem. That is the main concern. I lost a block due to that and I'm glad you didn't.

Also, as another idea, can you rig the MS to cut ignition when the fuel pressure drops below a certain level? That would certainly be a nice safety net. We do this with nitrous. Have lots of nitrous and no fuel is a real big problem.......

[Brendan]

Well, at least you know now. How does the piston look? As long as the ring lands are in good shape, no problem. That is the main concern. I lost a block due to that and I'm glad you didn't.

Also, as another idea, can you rig the MS to cut ignition when the fuel pressure drops below a certain level? That would certainly be a nice safety net. We do this with nitrous. Have lots of nitrous and no fuel is a real big problem.......

I did not pull the piston out of the bore and reinstall, but looking down along the edges with a flashlight, examining the piston and the ring that I can see, everything looks fine. And the one scratch doesn't look "repetitive" like I'd expect from a damaged ring land or ring. it's pretty minor and I can barely feel it, so, I think I'm good.

Actually, yes, MS does have this feature and I didn't really realize it until recently (Would have been nice if I'd realized it because it would have prevented this). The implementation is a little different - It is based on AFR not Fuel Pressure, you can configure a "delta" from your target AFR that is acceptable. That "delta" is based on a TPS x RPM table. Once you go outside the delta on the lean side, a warning light goes off immediately. Then, after a set amount of time, the engine kills spark and then fuel until you fall below a pre-configured RPM.



Needless to say, I'll be configuring this, along with dual knock sensors and the onboard/integrated knock sensing chip that was just released and integrated into the firmware...

[indie_wannabe]

Brenden,

Where do you plan to mount you knock sensors? For now, I'm just planning to install one knock sensor with my megasquirt. I'll be putting it on the block where the plenum support arm attaches. This seems like a good location for one sensor since it will be centered between the pistons (between cylinder 2 & 3). I assume if you installed two sensors, you'd ideally want one centered between cylinder 1 and 2 and another centered between 3 and 4.

I know there are a lot of threaded holes on the exhaust side of the block, but I worry that the heat from the header will hurt the longevity of the sensors. There aren't as many threaded holes on the intake side. What's your plan?

Next time I visit my engine at the machine shop, I'll have to scout for knock sensor mounting. If MS3 will accommodate multiple sensors, I'd love to run more than one. I'm sticking with MS2 for now, but I'd like to have a location picked out for the knock sensors when I upgrade the megasquirt.

Glad you engine damage wasn't more serious!

Brad

[Brendan]

Brenden,

Where do you plan to mount you knock sensors? For now, I'm just planning to install one knock sensor with my megasquirt. I'll be putting it on the block where the plenum support arm attaches. This seems like a good location for one sensor since it will be centered between the pistons (between cylinder 2 & 3). I assume if you installed two sensors, you'd ideally want one centered between cylinder 1 and 2 and another centered between 3 and 4.

I know there are a lot of threaded holes on the exhaust side of the block, but I worry that the heat from the header will hurt the longevity of the sensors. There aren't as many threaded holes on the intake side. What's your plan?

Next time I visit my engine at the machine shop, I'll have to scout for knock sensor mounting. If MS3 will accommodate multiple sensors, I'd love to run more than one. I'm sticking with MS2 for now, but I'd like to have a location picked out for the knock sensors when I upgrade the megasquirt.

Glad you engine damage wasn't more serious!

Brad

There are two raised spots in the casting on the driver's side, right below the cylinder head. One centered directly between 1/2, one centered directly between 3/4. Both are right at the top of the block. I am going to drill / tap. The forward one is smaller, and the knock sensor looks like it will be bigger than the "pad" but I'll let you know how it goes. The software has the ability to adjust gain per cylinder, so I think it should work.

These might interfere with some stuff no longer mounted on my engine (ICV?), but picture here:



I have the knock chip, so am hoping to get it installed and configured over the next couple weeks before two days at Watkins Glen.

[Dietrich]

Brendan,
I don't know how I missed this thread until now. Sorry to hear about your troubles, but it sounds like you've got a viable plan to get back on track with improved safety systems in place. As always, thanks for keeping the rest of us informed.

Best,
-Dietrich

[TR-Spider]

Brendan

this is where my engine builder put the M8 thread for the knock sensor .
the hole is 16 mm deep.

HTH
Thomas

[///schwartzman]

Actually, yes, MS does have this feature and I didn't really realize it until recently (Would have been nice if I'd realized it because it would have prevented this). The implementation is a little different - It is based on AFR not Fuel Pressure, you can configure a "delta" from your target AFR that is acceptable. That "delta" is based on a TPS x RPM table. Once you go outside the delta on the lean side, a warning light goes off immediately. Then, after a set amount of time, the engine kills spark and then fuel until you fall below a pre-configured RPM.



Needless to say, I'll be configuring this, along with dual knock sensors and the onboard/integrated knock sensing chip that was just released and integrated into the firmware...

So I should ditch the J&S??

[inastrangeland]

Brendan,

Sounds like you could start a new thread on installing and configuring knock sensors..... Just a thought.