A Bad Day In CA18DET Land

Discuss topics related to the CA18DE and CA18DET series engines.
Buddyworm
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float_6969 wrote:I had just done a pretty long WOT stretch when this happened. Like 4k-8k in 2nd, 3rd, and 4th and was at about 6k in 5th. I've never had any hints of detonation or knock. The total timing under load is 27deg. That's not an arbitrary number, but was set on the dyno with a detonation microphone to ensure there was no knock. This is only 12-13psi of boost and about 320whp. EGT's never exceeded 1300F. I'm on E85 with an actual ethanol content of 85%. The issue is isolated to this cylinder. I had plug issues on the same cylinder with the last rebuild. The porcelain cracked and a piece came off and scratched the cylinder wall. The only thing that would effect this that was the same from the last build is this cylinder head. the entire intake manifold is different, the turbo is different, the cams are different, fuel injectors are different, pistons are different, and compression ratio is different. I didn't know that there was a helicoil in it the last time. I didn't even know about it until recently when I went to check the plugs after dyno'ing it and that cylinders spark plug felt funny when it came out, like it was steel-on-steel threads. So I stuck a magnet down in there and it stuck to the threads. Then I got a flashlight and realized it had a helicoil in it. I have read in the past and heard from engine builders that a helicoil in an aluminum head doesn't allow the plug to dump heat as easily as the original aluminum thread because the steel doesn't conduct heat away from the plug as well as the aluminum does. In high performance applications, this can require the use of a colder plug on that cylinder to prevent this exact situation. If you don't do that, it can cause the exact situation that you're describing, but it wouldn't be due to ignition timing, but instead, the plug it self not being able to conduct heat into the head like it's supposed to.

I'm pretty confident the plug overheated from the helicoil, but I'm never one to say I know it all. I'm going to do a compression test and go from there. If the compression is low I'll start inspecting the engine more closely.

I glossed over the helicoil part. I wonder if anybody's done any legit testing on that effect. I can see how the coil would affect heat flux, but I was also under the impression that the majority of heat transfer through the plug was through the seat rather than the threads. :gotme



The thing with EGT's is that a low reading in the runner/turbine/exhaust pipe may not be telling the whole story. If you've only got one sensor in the turbine, say, it's only reading an average temperature through the pipe. I don't think those sensors respond quick enough to allow us to observe temperature variations cycle-to-cycle. If only Cyl. 4 is suffering you probably won't see it.

To add to that, preignition and detonation are characterized by an excess of heat transfer into the physical engine components, which is why you see melted plugs and pistons in an engine suffering preignition. All else equal, increased heat transfer into the engine itself would mean less energy going out the exhaust and a therefore lower EGT reading.


It's a good sign the engine fires up and runs ok though! Might have caught it before major badness went down.


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float_6969
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From what I read, most of the heat on a spark plug is transferred through the threads. The seat is mostly for sealing purposes. I wish I could find the article again. Anyway, there compression test will tell me a lot.

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float_6969
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Well I did the compression test tonight. The results are... weird.
cly test 1 test 2
1 135 122
2 160 145
3 123 110
4 117 105

Obviously 4 is low, which is the cylinder I was worried about. But 3 isn't that far off and 2 is WAAY higher than the others. I'm not sure what to make of this. Regardless, I think I need to pull the engine and tear it down an inspect it. Not too excited about this, but I feel like whatever is wrong must be minor.

Buddyworm
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Did you happen to compression test it when it was in good running shape so we can see if there was an imbalance right from the start?

Will you be posting pics of what you find on teardown? Very curious to understand this mode of failure. You'd expect #4 to be the hotter cylinder (even without the helicoil'd sparkplug hole) but I'm surprised #1 and #3 seem to have suffered as much as they did.

Maybe leakdown test before teardown to get an idea if it's valve seal or ring seal?

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float_6969
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I could swear I did a leak down, but I can't find it with the other info I have in this engine. I'm thinking I may not have as I usually keep pretty good track of stuff.

Leak down is next to see if there's any valve issues.

Will definitely be posting pics if the tear down

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Dayum Ryan, we're back at square one, I see! Although i can appreciate trying to develop this engine with modern tricks of the trade, but i too have learned that this baby is old-fashioned and doesn't like too many tricks done to it. What I'm saying is, regardless of what fuel and compression ratio you run, the design of the head and it's chamber/quench pads suggests that we do not get too cute with timing or risk catastrophic results. Off boost, I'll bring in some good timing, but on boost, I go back to the land of safety thus minimizing my losses in the name of some extra pony power. Simply put to all of you, the engine does not like too much timing under load; it just does not.

I'm sorry your engine is going through hell right now, but the one thing that bores is me the most is working on my own car because of something I did wrong. I've learned to get acceptable torque and power off-boost with simple tuning techniques and properly matched equipment. I wanted to see if I can tune a CA18DET with high compression pistons, but I'm in no rush as I am way too busy for that experiment. I'll stay tuned to see how this turns out because I know you're an old school super trooper and will be determined to make it happen. :dblthumb:

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float_6969
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I understand that this engine doesn't like a lot of timing, and I didn't think 27 degree's was all that much. I've tuned other engines that wouldn't tolerate so little timing. I still don't think it was ignition timing. I actually drove the car for a bit a few days ago and it seems fine. No oil smoke, no noises. I still need to do a leak down test. I'm still pretty confident this issue has nothing to do with ignition timing, but with that heli-coil that's on that spark plug. It's the same plug I had issues with in the last build and it had the same cylinder head. The other 3 plugs look fine, though it's hard to read plugs on E85 because it burns so clean. I think the compression ratio difference may be my fault. I ground the piston rings myself by hand. I'm wondering if I didn't have the gaps set equally somewhere. I know I didn't grind the rings all at one time and I'm wondering if I screwed something up there. I'm going to pick up a leak down tester this week and see what happens.

bentvalves
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Hi Ryan,

always something with these damn cars isn't it?

sick numbers on such low boost though, must feel insane!

did you do a wet compression test to keep things simple?

leak down test is only going to tell you rate of leakage over period of time, not where its going. You need to regulate air pressure into each cylinder at TDC and "listen" to where the air is going to determine if its rings or valves. I'll get real in depth with a detailed procedure over the phone. If your interested, PM me your number.

:whistle:

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I often joke and say, "What's the fun in having a car like that if you're not 100% sure you're going to actually get to where you want to go?!?" LOL!!!

It's a lot of fun right now, even at only 12-13psi. 25-30psi will just be insane. I got in a little on-ramp race with Mazdaspeed 3 a month ago or so, and at just 12psi I was WAY faster than him once boost came on. He started to pull away when we first hit it, but only for a couple of seconds. Once I got up to around 3500 he stopped gaining, and once I hit 4000 I had to pedal it while I was waiting for him to get out of the way, LOL!

I warmed the engine up to NOT, hooked up my jumper cables to my work truck (Chevy with old 6.5 Turbo Diesel. It has two batteries and a high current alternator), pulled all the plugs, and then started the compression test.

The only way I know how to do a leak down test is to hold the engine at TDC on the compression stroke of that cylinder and then listen for where the air is going. Obviously the percentage of leak down is important as well, but where the leakage is going is just as important. I have a mechanics stethoscope that I always use to listen with.

bentvalves
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rotate the motor by hand with pressure being bled into the cylinder. you'll hear valves opening, closing, sealing etc. makes it way easier to figure which cylinders are sealing well cause when they are the ratchet will start to fight you a bit.

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float_6969
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I haven't updated this in a while. I did a leak down test and the results are basically terrible. They follow the pattern on the compression test. Cylinder 2 is the only one with acceptable leak down. The other 3 leak way too much and the percentage of leakage follows the compression test. I'm pretty sure the head gasket is blown between cylinders 3 and 4 as well. It's also started smoking on start up, so I think this block is done. I'm already at 84.5mm on the bore, so there's no room to take it out another .5mm and put new pistons in it. Fortunately I picked up a couple of spare engines, a DE and a DET, plus a spare transmission a couple of years ago for $250. They were in pieces, but mostly complete. I tore them down to short blocks last weekend and got the crank pulleys that were stuck on both off. I'm going to take them both down to my machinist and have him pick the best parts from both blocks, order some parts, and have a new short block. Then I can just do a quick short block swap and not have the car down forever again. I haven't driven it much, just enough to keep the injectors from getting fouled up and the fluids circulating. It still runs great, but I know it's not OK.

As a little teaster, I think I'm bringing the high compression back. I miss the off-boost performance I had with 10:1 compression.

bentvalves
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so where is the air going?

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float_6969
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On 3 and 4 there was air going into the PCV system and into the adjoining cylinders, hence the blown HG. Cylinder 2 was fine, and normal leakage pas the seals. #1 wasn't all that bad. I think when I filed the rings, I over-gapped them. I was really worried about it being too tight, so I think I erred a little too far towards loose.

I've ordered pretty much everything I need to build another short block. I ended up having some spare time this last weekend and tore both the DE and DET short blocks down. The DE was in WAY better shape. I'm going to use the DET block, and DET rods, but the DE crankshaft. The DET crank journals were in way worse shape, as well as the bearings all the way around. The DET engine had obviously had a rough life. I was surprised to find the DE had a main cap girdle though. That DE engine had signs that it didn't exactly have an easy life though either. That thing had seen A LOT of revs at some point from the look of the bearings. I think the rod bolts were stretched as well. Anyway, once I get the block down to the builder, I'll find out how much needs taken out of the cylinders to make them ready for new pistons and then get some pistons ordered. I'm hoping it's not much and I can just get the pistons made at .25mm over and keep extra meat in the cylinder walls.

bentvalves
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get standard bore forged pistons if there is no ridge in the top of the cylinders.

chances are good that a few thou will need to be honed out of the cylinder to get desired piston to wall anyway and that will give you a nice brand new bore without going oversize.

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float_6969
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There's a pretty bad ridge at the top, so that won't work. I could probably pull it off with the DE block, but the cylinders in the DET block are too worn for that.

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I've got at least one mint standard bore DET block in a shed in Alabama you are welcome to. I would offer to ship it/them to you but I now reside in Utah so the logistics would be a bit of a nightmare. If you still need it in September I can facilitate shipping.

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float_6969
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While I would totally take it off your hands for a spare, the spare DET block I have didn't end up being in that bad of shape and will easily handle a .5mm over piston. I could have actually gone with .25mm over, but nobody makes an 83.25mm ring set, so I was stuck with 83.5mm. The pistons have already been ordered, but they're a custom piston (10:1 compression) and even with a rush fee I won't see them for a couple of weeks. I have everything else I need either on order, or setting in the garage as a spare.

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Man, I hate that you are going through these problematic episodes, but on a side note, I have never seen a ridge on anyone of the 62 CA18s I've opened up before. Developing a ridge means massive wear as a result of piss-poor maintenance or an already inferior oiling system. Your total timing seems a bit high for the comp ratio you're using, even with the E85. But for the amount of boost you're pumping thru your engine, it also seems safe and doable as well. Just strange IMPO :crazy:

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float_6969
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Yea, I have a bore gauge and actually checked it and the wear was only .0008" at the most, so not bad at all.

27°on E85 and 8.5:1 compression and 12psi seems high? I think that's low. On an interesting note, the engine didn't seem to like less timing than this from 7psi all the way up to 17psi. There was never any knock. When I backed it down to 25°power fell off by about 5%, EGT's went up, and the engine didn't sound "right". Out of curiosity, I added 2° and it didn't make any change to anything. EGT's may have dropped a little, but it was such a minor amount, that I'm not even sure about that. Maybe it's the 4 port head wanting more timing? Cams? Cam timing? I also have a pretty big exhaust housing on the turbo, AND it's twin scroll, so I'm not going to get much reversion. Anyway, I think I'm going to pull the head today to see what's going on in there. Happy Father's Day to me LOL!

bentvalves
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so if taper was no more than "8 tenths", then....there is no ridge.

i dunno. I just put standard bore pistons in 1.6 toyota engine, and I had to hone something like .008" to get those f*ckers to go in the hole.

food for thought.

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yea big turbos and aftermarket cams depending on LSA etc are going to require their own unique timing maps. ask the engine what it wants on the dyno and your golden.

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Yea, I really considered having them just made at 83mm, but custom pistons are WAY more expensive than standard pistons. Plus they take 6 weeks to make them. I didn't want to risk them being too loose in the bore... Yea, that's basically what I do on the dyno. The dyno operator is an experienced tuner was well and he basically said my tune was pretty good.

dash
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I found a ridge on all of the few CA18s I opened up, moreso on a side of the bore
Several times the topic was discussed on forums.
'sidewaysdanny'(ca18 sxoc diehard) says he sorted threw quite a few blocks to find one without a ridge
CA18 always stuck me as unrefinded & trashy running (worst vs BP, 4ag, 4g63). Smooth idle tho
Both uk and oz/nz boards discussed the half-counterweighted crankshaft inherrit design flaws in depth
.....explaining the balance, harmonics and deformation characteristics
same dude had to design that oil dipstick :chuckle:

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float_6969
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How much of a ridge did they find? When I initially thought there was a ridge, I realized what I was feeling was oil coked up at the top of the bore where the rings and piston never touch. Once I cleaned that off, there was no perceptible ridge anymore. When I talked about it being worn out to .0008", it was actually near the middle of the stroke, so the cylinders were "barrel" shaped, which is pretty typical wear.

It seems like the UK guys have more issues with these engine than the Aussies or the few of us in the US do. Weren't the UK engines built in a different plant than the JDM engines? I've wondered for a while if they weren't produced as well.

Compared to newer engine designs, I'm sure the CA is unrefined. What people often seem to forget is that this engine was developed in the very early 80's. It was also Nissan's first timing belt engine. The fact that you can make 5 times the power that it was originally designed for with a stock crank and rods, minor port work, cams, and supporting turbo/fuel/spark, is impressive IMHO.

That being said, the half counterweight crank isn't ideal, obviously, but doesn't seem to be too terribly limiting unless you're trying to make huge numbers. Once again, not bad for an engine designed over 30 years ago and also Nissan's first timing belt engine.

Let's not forget the damn thing is TINY! There's a reason it's a common engine swap candidate for old vehicles. Many other engines simply won't fit without firewall or core support modification.

dash
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Only compared the CA to other 80s powerplants. CA noticably physically bigger than BP & 4A
BP, 4/7A, 4G all made equivalent big power per cc

Uk & OZ been hammering CAs for years, many in various competitions.... hill climb, drift, drag, circuit, etc
Those ol' dawgs posted interesting data exposing CA18 weak links/downsides/limits/fixes

Iirc the later 4 port had issues with a run of inlet valves

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float_6969
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Hmm, I've had various B series engines over the years (B6ZE, B8, & BP), though the BP was more of an SR era engine than a CA era one. Regardless, it's certainly not any bigger than those engines. The intake manifold might be bigger on the CA, but that's not really something that's a part of the engine itself. Obviously the 4G is a well known engine and does make good power. I didn't mean to sound like the CA was something special as far as power production goes. I've never thought that. I think it makes about the same power per cc as any of it's counterparts.

Yea, the Ozzies especially have really been taking the CA to it's limits. It's fun to see.

Yea, they did have inlet valve issues. They also used larger head bolt threads in the block. They also had some issues with core shift in the castings. That would cause you to cut into the water jacket when you tried to bore the engine out for larger pistons.

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Who's tuning your set up ryan? Is 5th gear still around there in peka?

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float_6969
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I'm tuning it. 5th gear is still there, but sold the dyno.

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So have we pulled/inspected pistons and bearings yet?

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Not yet. I'm still waiting on pistons for the new block, so I haven't torn the old engine out yet. The oil looks completely fine and it runs fine, albeit slightly smoky on startup. I wanted to keep driving it some to keep the injectors from fouling up and to keep the rust off of the rotors on my brand new BBK, so I haven't torn it down yet. I have another block ready to go to the machine shop, so once I get the pistons, I can take it down and have it built. I'm hoping to re-use the head again, but only if I can get that steel helicoil out and replace it with an aluminum one.


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