Fright! Now worried... Anyone explain?
Discussion
I had booked a Dyno session with my local Power Station on my modified LS7 based car, and all went according to plan.
Couple of runs, but we could not get the back strapped down hard enough to stop the rear tyres spinning above 4-5k. Very stressing seeing your hard work put under such load and revs...
Anyhow... two runs in, nothing extreme, just slow build up to 5 k and back down again through the gears... then idle for a few secs. All OK - then suddenly the oil pressure dropped like a stone to zero and it sounded like someone had thrown a handful of granite chippings into the engine, the revs climbed on their own to 1.5k revs, then back down all in a matter of a second ...before we managed to hit the STOP button!
The tester/driver was wearing knock stethoscope, but I was not and it was me that heard it first and signalled him to hit that stop button.
I shot out of the car, saw wisps of white smoke coming out of the air vent and then fearing the worst fell to the floor to view the oil slick with lumps of metal spreading all over the floor....
....BUT nothing! ...NADA . ...Ziltch ????? No sign of leaks, no sign of parts of my engine in places they shouldn't have been!
We both scratched our heads.... had a very close look around the engine bay.. waited for 5 mins, held our breath and fired it up again, expecting a loud clatter!...
..But NO.... It started like nothing ever happened! Good oil pressure, albeit it has always been higher than I would expect it to be (55 idle - 104ps 5k revs).
We did 3 more runs, but just could not keep the back down hard enough, so I will be back maybe next week and take the rear clip off to help them add more straps.
So... what happened??? The test engineer said that he did not hear anything unusual through the stethoscope when it happened, and only saw the red oil warning light come on that alerted him that something was not right... Me - I can still hear the ear-shattering noise in my dreams!
So we are stuck... was this a calamitous event? What caused it? And why did it not affect later starts?
Know anyone that might have experienced this before?
As you can imagine, I can't help worrying if it might happen again...
Couple of runs, but we could not get the back strapped down hard enough to stop the rear tyres spinning above 4-5k. Very stressing seeing your hard work put under such load and revs...
Anyhow... two runs in, nothing extreme, just slow build up to 5 k and back down again through the gears... then idle for a few secs. All OK - then suddenly the oil pressure dropped like a stone to zero and it sounded like someone had thrown a handful of granite chippings into the engine, the revs climbed on their own to 1.5k revs, then back down all in a matter of a second ...before we managed to hit the STOP button!
The tester/driver was wearing knock stethoscope, but I was not and it was me that heard it first and signalled him to hit that stop button.
I shot out of the car, saw wisps of white smoke coming out of the air vent and then fearing the worst fell to the floor to view the oil slick with lumps of metal spreading all over the floor....
....BUT nothing! ...NADA . ...Ziltch ????? No sign of leaks, no sign of parts of my engine in places they shouldn't have been!
We both scratched our heads.... had a very close look around the engine bay.. waited for 5 mins, held our breath and fired it up again, expecting a loud clatter!...
..But NO.... It started like nothing ever happened! Good oil pressure, albeit it has always been higher than I would expect it to be (55 idle - 104ps 5k revs).
We did 3 more runs, but just could not keep the back down hard enough, so I will be back maybe next week and take the rear clip off to help them add more straps.
So... what happened??? The test engineer said that he did not hear anything unusual through the stethoscope when it happened, and only saw the red oil warning light come on that alerted him that something was not right... Me - I can still hear the ear-shattering noise in my dreams!
So we are stuck... was this a calamitous event? What caused it? And why did it not affect later starts?
Know anyone that might have experienced this before?
As you can imagine, I can't help worrying if it might happen again...
My guess is that after the high speed run the bulk of the oil ended up at the bottom of the engine and the scavenge pump didn't keep up and get it back to the tank quick enough. It ran out of oil supply, unloaded the oil pump (hence the engine speed briefly increased) and then the scavanege pump manged to get some oil back to the tank. Maybe because the oil was low or the scavenge pump is on the way out?
Of course this is a total guess as it's not an engine I'm familiar with and assumes it's dry sumped!
Of course this is a total guess as it's not an engine I'm familiar with and assumes it's dry sumped!
fatjon said:
My guess is that after the high speed run the bulk of the oil ended up at the bottom of the engine and the scavenge pump didn't keep up and get it back to the tank quick enough. It ran out of oil supply, unloaded the oil pump (hence the engine speed briefly increased) and then the scavanege pump manged to get some oil back to the tank. Maybe because the oil was low or the scavenge pump is on the way out?
Of course this is a total guess as it's not an engine I'm familiar with and assumes it's dry sumped!
Yes it is dry-sumped... changed the oil a few days ago 7.5 ltrs 0-40 Mobile 1 ESP, and it has run on the road without problems for a few days...Of course this is a total guess as it's not an engine I'm familiar with and assumes it's dry sumped!
The engine has only done 500 miles from new.
How to prevent this happening again? Obviously something wrong somewhere?
I don't want to blow the engine....
Ideas?
Edited by 3Dee on Friday 6th September 12:34
I have nothing to compare it with TBH
The engine came from the States, was dyno tested on a rig to 7400rpm (peaking at 630bhp at 6800rpm) and has the following spec:
Mahle motorsports pistons were fitted by GM into a block that was honed .005" to 4.130 by them.
The entire rotating assembly was re-balanced by GM.
Rod bolts out to special ARP ones that we rework to fit the LS7.
The cylinder heads are modified, in the bowl area under the valve approx 20 cfm flow improvement in most areas.
Custom made Lunati camshaft to my specs. .612", .610" lift. 115 deg lobe separation angle. - 236 deg intake and 246 deg dur@.050 -
Gold valve spring upgrade to dual springs with a bit more spring pressure.
Machined off oil pressure sender boss from valley cover to allow flipping of intake, drilled tapped, plugged port.
Re-plumbed valve cover venting with hard line.
So.. not sure if:
1. pressure sensor is off
2. Gauge is off
3. pressure is as reported.
What to do?
The engine came from the States, was dyno tested on a rig to 7400rpm (peaking at 630bhp at 6800rpm) and has the following spec:
Mahle motorsports pistons were fitted by GM into a block that was honed .005" to 4.130 by them.
The entire rotating assembly was re-balanced by GM.
Rod bolts out to special ARP ones that we rework to fit the LS7.
The cylinder heads are modified, in the bowl area under the valve approx 20 cfm flow improvement in most areas.
Custom made Lunati camshaft to my specs. .612", .610" lift. 115 deg lobe separation angle. - 236 deg intake and 246 deg dur@.050 -
Gold valve spring upgrade to dual springs with a bit more spring pressure.
Machined off oil pressure sender boss from valley cover to allow flipping of intake, drilled tapped, plugged port.
Re-plumbed valve cover venting with hard line.
So.. not sure if:
1. pressure sensor is off
2. Gauge is off
3. pressure is as reported.
What to do?
Internal I believe - here is the spec:
Built by US supplier that has now been put on the road.. Spec is:
1. Mahle motorsports pistons fitted by GM into a block that was honed .005" to 4.130 by them. The entire rotating assembly was re-balanced by GM.
2. Rod bolts changed to special ARP ones rework to fit the LS7.
3. Cylinder heads modified in the bowl area under the valve approx 20 cfm flow improvement.
4. Custom made Lunati camshaft .612", .610" lift. 115 deg lobe separation angle. - 236 deg intake and 246 deg dur@.050 -
5. Gold valve spring upgrade to dual springs,
6. Machined off oil pressure sender boss from valley cover to allow flipping of intake, drilled tapped, plugged port.
7. Re-plumbed valve cover venting with hard line.
Running oil pressure way too high I think
Loss of oil pressure temporarily after dyno-run on idle. No problems seen after startup.
Built by US supplier that has now been put on the road.. Spec is:
1. Mahle motorsports pistons fitted by GM into a block that was honed .005" to 4.130 by them. The entire rotating assembly was re-balanced by GM.
2. Rod bolts changed to special ARP ones rework to fit the LS7.
3. Cylinder heads modified in the bowl area under the valve approx 20 cfm flow improvement.
4. Custom made Lunati camshaft .612", .610" lift. 115 deg lobe separation angle. - 236 deg intake and 246 deg dur@.050 -
5. Gold valve spring upgrade to dual springs,
6. Machined off oil pressure sender boss from valley cover to allow flipping of intake, drilled tapped, plugged port.
7. Re-plumbed valve cover venting with hard line.
Running oil pressure way too high I think
Loss of oil pressure temporarily after dyno-run on idle. No problems seen after startup.
Edited by 3Dee on Friday 6th September 14:01
What ecu are you using, and do you have any datalogs of the run, and are you recording oil pressure ?
If you arent, start doing so. You could also try and set up an engine kill if oil pressure falls below a certain threshold.
How are you reading oil pressure ? electronic or mechanical gauge ?
If you arent, start doing so. You could also try and set up an engine kill if oil pressure falls below a certain threshold.
How are you reading oil pressure ? electronic or mechanical gauge ?
If it was me, the engine would be out and I'd be inspecting the mains and big ends. That's inconvenient but nowhere near as inconvenient as it will be when the engine blows up. You are running on borrowed time after having no oil pressure.
I would check that the size of the oil reservoir is suitable for the application - it may work fine on the occasional drive down the road but I doubt that it ever really sees more than 4000 rpm for a few seconds at a time, masking what happens when you run far more than that for any sustained level of time.
You really need to try to get a camera on the dry sump oil level, or even better a level switch. Run the engine at various speeds when warm (does not need to be at load) and figure out what the dynamic level the dry sump tank sump scavenges and operates at - it needs to be engineered to have reserve and ideally some head between the tank and dry sump pump. When you know the level you need to run at, put a level switch in and link it to the ignition to protect the engine.
I'd contact the engine builder and ask for some advice as well.
I would check that the size of the oil reservoir is suitable for the application - it may work fine on the occasional drive down the road but I doubt that it ever really sees more than 4000 rpm for a few seconds at a time, masking what happens when you run far more than that for any sustained level of time.
You really need to try to get a camera on the dry sump oil level, or even better a level switch. Run the engine at various speeds when warm (does not need to be at load) and figure out what the dynamic level the dry sump tank sump scavenges and operates at - it needs to be engineered to have reserve and ideally some head between the tank and dry sump pump. When you know the level you need to run at, put a level switch in and link it to the ignition to protect the engine.
I'd contact the engine builder and ask for some advice as well.
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