Rover piston melting point

mgbv8 · Post by **mgbv8** » Mon Mar 31, 2008 7:29 pm

Anyone know at what temp a standard Rover V8 piston will melt?

Post by **Coops** » Mon Mar 31, 2008 8:57 pm

about 200bhp nitrous Perry

volospian · Post by **volospian** » Tue Apr 01, 2008 7:36 am

or if most "pub experts" are to be believed... anything over 5000rpm

Post by **Coops** » Tue Apr 01, 2008 4:47 pm

volospian wrote:or if most "pub experts" are to be believed... anything over 5000rpm

Ian Stew and myself are well overdue a melted piston then

JSF55 · Post by **JSF55** » Tue Apr 01, 2008 7:24 pm

Aluminium will start to melt at about 630oC the compisitions used for pistons could see this go well up over 740oC befor any damage occurs, no idea how your going to be able to measure it though !

mgbv8 · Post by **mgbv8** » Tue Apr 01, 2008 7:42 pm

Just an idea I'm toying with for a safety cutout for the gas. EGT sensor in the front two (the ones that give up first on mine) to shut down the nitrous. Might not come to anything but you never know.

stevieturbo · Post by **stevieturbo** » Tue Apr 01, 2008 8:54 pm

Generally speaking, if you are seeing 950+ at the exhaust port ( or very close to it ) Id be pretty damn worried.

Both in terms of melting pistons, and burning valves.

That said, when I had mine on the dyno recently, highest I seen on the EGT gauge was about 800deg.

Not sure EGT alone, would be fast enough for a safety measure. Perhaps rate of change of heat via EGT might work, combined with actual temperature too.

Bit the damage can happen so quickly if things are wrong, that its hard to set up automatic protection.

If you have 1 cylinder that keeps doing it, monitoring AFR's on that cylinder, and EGT on a few might reveal some info as to why.
Also check injector flow, in case one is down slightly ( assuming efi )

mgbv8 · Post by **mgbv8** » Wed Apr 02, 2008 8:26 pm

Weber 500 Stevie with the smaller primaries mounted to the front.
I was thinking of EGT in the primaries on the front two.

stevieturbo · Post by **stevieturbo** » Wed Apr 02, 2008 8:32 pm

mgbv8 wrote:Weber 500 Stevie with the smaller primaries mounted to the front.
I was thinking of EGT in the primaries on the front two.

Innovate TC-4 does 4 thermocouples. SO if thats what you are using, it might be worth using all 4 ( or perhaps monitoring all 8 with a second TC-4 )

But if it was always one cylinder melting, Id be tempted to stick a wideband in that cylinder, before using EGT probe.

mgbv8 · Post by **mgbv8** » Thu Apr 03, 2008 9:43 pm

Sounds interesting Stevie. Got a weblink?

stevieturbo · Post by **stevieturbo** » Thu Apr 03, 2008 11:23 pm

Its just the Innovate TC-4. Same people do the wideband stuff.

Bill will be able to supply you one.

kiwicar · Post by **kiwicar** » Fri Apr 04, 2008 1:32 pm

Surly rather than shutting off the nitrous which is giving you power to get you down the track you would be better off cooling the pistons better and coating them with a ceramic barrier, this way you will go faster rather than going fast for 3/4 track then getting passed at the end. You could set up an external dry sump type pump to feed lots of oil (via an extra oil cooler to a gallery below the pistons and rig up jets pointing at the underside of the pistons. Have this controled by a solonoid that switches on the flow when you arm the Gas. If you want a second stage of back up then rig a water injection set up to come on when the gas has been on for say 2 or 3 seconds.
I think if you are relying on the rise in exhaust temp to tell you when to shut the NO2 off then it may all be too late, the combustion temperature rises often because you have localised burning of the ally in your pistons, for a given fuel and oxident (at a given pressure) the temperature of combustion is pretty constant, it is when the fuel changes from gasoline and ethanol to ally the temp goes up

.
Mike

stevieturbo · Post by **stevieturbo** » Fri Apr 04, 2008 4:05 pm

kiwicar wrote:Surly rather than shutting off the nitrous which is giving you power to get you down the track you would be better off cooling the pistons better and coating them with a ceramic barrier, this way you will go faster rather than going fast for 3/4 track then getting passed at the end. You could set up an external dry sump type pump to feed lots of oil (via an extra oil cooler to a gallery below the pistons and rig up jets pointing at the underside of the pistons. Have this controled by a solonoid that switches on the flow when you arm the Gas. If you want a second stage of back up then rig a water injection set up to come on when the gas has been on for say 2 or 3 seconds.
I think if you are relying on the rise in exhaust temp to tell you when to shut the NO2 off then it may all be too late, the combustion temperature rises often because you have localised burning of the ally in your pistons, for a given fuel and oxident (at a given pressure) the temperature of combustion is pretty constant, it is when the fuel changes from gasoline and ethanol to ally the temp goes up .
Mike

Oil jets, or ceramic coatings are not going to correct the fact, that either fuelling or ignition is wrong, causing the damaged pistons.

kiwicar · Post by **kiwicar** » Sat Apr 05, 2008 7:21 am

Very true Stevie, I was assuming this was not intended as a bodge to cover an incorrect mixture but an attempt to keep an engine on the ragged edge running with alot of Nos running through it.
I still think that shutting off the Nos because the exhaust gas temp has gone up will be too late to any good.
On a correctly set up mixture the piston cooling and coating should let you run more Nos for longer than without meltdown, you need to keep the piston surfaces (in the combustion chamber) below ignition temperature of the Ally and the only ways I see of doing it (if the mixture is correct) are to put less heat into the surface (coating) or less combustion (less Nos and power) or take the heat away as fast as possable (underpiston cooling). Actually there is also the water injection which does a combination of stabalising the combustion and moderating the rate of innitial of rise in combustion chamber pressure (and therefore temperature), but I no experience of using it with nitrous.
Mike

stevieturbo · Post by **stevieturbo** » Sat Apr 05, 2008 8:36 am

There are people firing 100, 200, 300 and larger shots of nitrous.

If the fuelling is correct ( ie even go nuts and make it mega rich ) and the timing is detonation free. Then I see no reason as to why piston damage will occur.

If you insist on running a huge shot, then get a good ignition system, and run AFR's into the 10's. It is very rich, but it should also be very safe. Get detonation cans on it, to listen for detonation, and make sure you dont have too much timing.

I dont have a lot of experience with nitrous ( very little in fact ). But I dont see it as being much different to running 30-40psi of boost. If any at all. ( or less boost )

The engines requirements for survival are still the same.