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Post by noddle on Aug 15, 2009 16:39:42 GMT 10
This is what happens when you having fun I was busy doing some high RPM pulls tuning my Megasquirt system, and pop.. Attachments:
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Post by noddle on Aug 15, 2009 16:41:27 GMT 10
I though I had blown the exhaust gasket, but once I pulled it down, this is what I found Attachments:
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Post by Datsunreal on Aug 18, 2009 11:39:24 GMT 10
is that a bit of head gasket hanging out of it? thats too bad
is that an N47 head with the steel exhaust liners? did you do any work on that head? i would have thought its a bit High comp for the turbo, unless its one of the higher volume L28 ones.
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Post by scando on Aug 18, 2009 12:32:55 GMT 10
Those exhaust ports have been a touch on the warm side of things
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Post by noddle on Aug 19, 2009 10:05:47 GMT 10
Those exhaust ports have been a touch on the warm side of things My understanding on the liner, are that they are suppose to get red-hot, to help burn any unburnt stuff, for emissions, I'll be installing my EGT probe when I put it back together, then I'll know for sure what temp it's running as for the N47 head, the piston are dished, and I believe the P90 heads (turbo heads) are similar shape, small cc Nigel
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Post by scando on Aug 19, 2009 13:26:55 GMT 10
I haven't used one of those heads with the liners in them before but we work on the theory that unless the exhaust ports have got a bit of black colour too them it's too lean What compression ratio does the N47 give you?
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Post by Datsunreal on Aug 19, 2009 15:49:28 GMT 10
yeah those liners get real hot and burn off unburnt hydrocarbons ect. with a standard l24E the N47 should give over 9:1? i know my early model L24E with E88 gives 8.9:1. from the manual you can spend hours dicking about with online compression calculators! www.ozdat.com/ozdatonline/enginedesign/ this is awesome, fours and sixes Nigel do you know the volume of the valve cutouts on the head of an L24E piston? i need to find out so i can spend even more time dicking about with compression calculators and work out how much if any to shave off my N47 to give me about 9.5:1. your K is really coming along now! keep us posted
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Post by noddle on Aug 19, 2009 21:40:49 GMT 10
Nigel do you know the volume of the valve cutouts on the head of an L24E piston On my L24 (240K) and the L24 engine I took the head off (MR30), both have dished pistons, not flat top, Attachments:
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Post by noddle on Aug 19, 2009 21:49:13 GMT 10
I haven't used one of those heads with the liners in them before but we work on the theory that unless the exhaust ports have got a bit of black colour too them it's too lean I'm running a AFR gauge, you need this when tunning, otherwise you burn holes in pistons, here's my AFR table to give you some idea on what I'm doing. Nigel Attachments:
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Post by Datsunreal on Aug 20, 2009 7:53:05 GMT 10
nice, does it have an instant readout on the dash or do you have to datalog it and look at it afterwards? this is what my pistons look like. with "valve reliefs"
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Post by noddle on Aug 20, 2009 9:02:24 GMT 10
nice, does it have an instant readout on the dash or do you have to datalog it and look at it afterwards? this is what my pistons look like. with "valve reliefs" High compression, no turbo on that, not without issues anyway, my AFR is real time, I have a gauge under the lip of the dash, this is what I'm using 14point7.com/Widebands/NAW_OEM/NAW_OEM.htmalso I can log everything with Megasquirt Nigel Attachments:
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Post by Datsunreal on Aug 20, 2009 11:45:28 GMT 10
ive got no pans for turbos, its going to be N/A all the way. maybe i wont need to mill anything!
discrete A/F readout, i had to look hard to see it! ive got a similar device yet to be installed. i cant run closed loop with the wideband as well as the A/F meter though, its got a seperate 3 wire sensor for that. does the megasquirt have a closed loop function?
good to see youve still got the original "Wood" steering wheel!
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Post by scando on Aug 20, 2009 13:58:24 GMT 10
My A/F ratio is around 11.0-11.5 right through the part of the fuel map that I regularly use. Anything higher than 11.5 and it looses power and melts the exhaust manifold. For a budget turbo L-series build I would just use a standard N42 block/N42 head combo from a 280XZ. They have 8.3:1 compression so you should just be able to pick one up for a few hundred bucks bolt your bits on and go for it This is what my car originaly had and was good for 174rwkw and a truckload of torque on 10psi at 15 deg timing advance on 98 fuel. I assume the Megasquirt is fuel and ignition? So you could run more advance through the low load parts of the map and get even better results. I've since swapped to a P90 head and forged pistons which give a compression ratio of 8.0:1. On the same boost and timing it was a slug. But I can now get away with running more boost to make up for it and a bit more.
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Post by noddle on Aug 20, 2009 19:22:00 GMT 10
does the megasquirt have a closed loop function? Yes, I turn this on once I get the tune very close, My A/F ratio is around 11.0-11.5 right through the part of the fuel map that I regularly use. Anything higher than 11.5 and it looses power and melts the exhaust manifold. For a budget turbo L-series build I would just use a standard N42 block/N42 head combo from a 280XZ. They have 8.3:1 compression so you should just be able to pick one up for a few hundred bucks bolt your bits on and go for it This is what my car originaly had and was good for 174rwkw and a truckload of torque on 10psi at 15 deg timing advance on 98 fuel. I assume the Megasquirt is fuel and ignition? So you could run more advance through the low load parts of the map and get even better results. I've since swapped to a P90 head and forged pistons which give a compression ratio of 8.0:1. On the same boost and timing it was a slug. But I can now get away with running more boost to make up for it and a bit more. I do have a L28, but I believe it has flat top pistons, this would give to compression of about 9.7ish which would be to high, but I do need to pull the head to check, as for a P90 head, I can't say I've every seen one up close, I suppose that's because Turbo L6, were never sold in Aus. this is my spark table, but I think I will need to pull a few degrees up in the 6 - 7 K range Nigel Attachments:
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Post by scando on Aug 20, 2009 21:12:25 GMT 10
%#@*!!!! You're running some serious timing advance there! So in these maps the % figure up the side is your manifold pressure? Or something else? Do you have some kind of knock sensor you're using while tuning it? What boost pressure are you running? You'll probably find that if you back the maximum advance back to about 30 degrees it'll still go just as good. You get to a point where adding advance just gives detonation with no gain in power. Have you had the head off the engine yet to check it out? Like I said, I'm running a P90 but I don't think they're as good as people say. No reason why you can't make good power with a standard 280ZX or Patrol L28. Normally the worst point for detonation is where it first reaches full boost. If it were me I'd pull the advance back a lot through the 2000 onwards part of your map. You can start to creep it back up higher in the rev range but only a few degrees. Or just to get the thing going, just set your entire map at 15 degrees. Richen the fuel map up to around the 11-1 mark and see what it does. I reckon you'll be plesantly surprised
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Post by bluerat on Aug 20, 2009 22:16:30 GMT 10
Howdy Noddle, Being in Burnie, I'd pop out to Southside Performance, see Darren and get him to run it on his Dyno, he could help with the tune, he's done a few over the years. It's a lot easier to do on a rolling road, than on the real road.
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Post by scando on Aug 20, 2009 22:25:41 GMT 10
Howdy Noddle, Being in Burnie, I'd pop out to Southside Performance, see Darren and get him to run it on his Dyno, he could help with the tune, he's done a few over the years. It's a lot easier to do on a rolling road, than on the real road. That's an even better idea. Could save you a lot of $$$'s in the long run.
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Post by noddle on Aug 21, 2009 8:58:06 GMT 10
Do you have some kind of knock sensor you're using while tuning it? What boost pressure are you running? I'm running 15 PSI, it starts to build about 2.5K, by 3.5 its about 10, by 4k it's maxed out, and no, no knock sensor You'll probably find that if you back the maximum advance back to about 30 degrees it'll still go just as good. You get to a point where adding advance just gives detonation with no gain in power. to be honest I didn't hear any pinging, but at 7K you don't hear much Have you had the head off the engine yet to check it out? No, I don't have a real shed, so I have to work around the weather, and since I'm not as young as I was, I don't work in the cold very well Normally the worst point for detonation is where it first reaches full boost. If it were me I'd pull the advance back a lot through the 2000 onwards part of your map. You can start to creep it back up higher in the rev range but only a few degrees. Or just to get the thing going, just set your entire map at 15 degrees. Richen the fuel map up to around the 11-1 mark and see what it does. I reckon you'll be plesantly surprised You probably right, once I get it running again, I'll pull more timing from 4K and up. About my spark table, any thing above 100 (on the left hand side) is boost Howdy Noddle, Being in Burnie, I'd pop out to Southside Performance, see Darren and get him to run it on his Dyno, he could help with the tune, he's done a few over the years. It's a lot easier to do on a rolling road, than on the real road. I will go see him, but I wanted to get something close, I did see on another website where he had a 'tuning day', but I didn't see till a week later and missed out, Nigel
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Post by scando on Aug 23, 2009 12:52:00 GMT 10
Yeah, definately not the time of year to be working outside Normally by the time you can hear pinging in a turbo engine without knock sensors it's too late. If you're running 15psi with about 8.3:1 compression I take it? And on pump fuel? I'd definately knock the timing back a fair bit. You might be able to do a basic fuel map then get the timing map done on the dyno to save a few $$$'s vs getting the lot done on the dyno. But definately richen it up a lot. It's hard to do a timing map on the road cause in 2nd and 3rd it goes through the rev range too quick to tell if you've got it right and in 4th and 5th you're pushing 200km/h!
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Post by noddle on Aug 24, 2009 9:24:39 GMT 10
If you're running 15psi with about 8.3:1 compression I take it? And on pump fuel? Correct (if the engine calculator is right, and my figures are correct) 7mm dish, 40-41cc head, L24, comes out to be about 8.4:1 I'm also running E10 fuel, I stopped using av-gas years ago on my bike. Nigel
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