Good morning all! After a week away visiting Mildura where my Z is I've finally been able to drive it after 14 years since buying it. It's been a journey so far to get it from having a dead engine to a rebuild to having it on the road a couple days ago. I'd like to run the engine in but unfortunately, I'm getting a noise that comes on when I give the throttle a decent poke that sounds like either lifter tap or possibly detonation. The noise seems to only come on during faster acceleration, it's not as present if I accelerate slowly and it can't be heard if I'm sitting at constant RPM. Since having the engine out I've changed a LOT, slightly biggers turbos, AMS exhaust manifolds, bigger SMIC's, enlarged throttle bodies, underdriven crankshaft pully, Apexi pod intake, AMS downpipes, deleted systems such as EGR, AIV.. etc. I'm trying to work out how I should progress from here, my current thinking is "Maybe, since I changed a lot, it's not getting the right air/fuel ratio under acceleration from the factory ECU map which is causing detonation under acceleration? Therefore, I should get the noise diagnosed and get some sort of base tune in the event that the noise is the result of needing a tune up". If the tuner I took the car to determined that the the noise wasn't related to needing a tune I could go down a different route (If it's diagnosed as sticker lifters for example), but I figure seeing as I changed a lot of parts a tune would be the next logically step anyway. Has anyone been through a similar process or how would you proceed given the context above? Would changing a lot of parts like this possibly result in detonation if I hadn't had the car tuned since changing them?
Bigger turbos - what are you boosting to? I mean yeah detonation is certainly possible if it's leaning out. No mention of fuel system upgrades?
I would be seriously considering something tuneable. You wont get the max use out of the mods without it. Turbos might make the same boost, but move more air. If the fuel map cant add enough fuel, you wont have a good time. See if you can get a run on a dyno or at very least a wideband O2 in the exhaust to see what the ratio is. If you are running stock injectors, you are going to max them out super quick too.
Yeah, haven't changed anything with the fuel system except for putting in new OEM injectors and a fuel filter. Haven't set the boost yet though it's got a Turbosmart Eboost Street 40. I should probably investigate that and set up a mild boost level while I run it in. Of the 90kms I've driven it since the rebuild I got it to about 3psi at the most as I haven't been driving it too hard til I work out what this noise is.
Thank you for your recommendations, I'll have to see if I can get a hold of a wideband O2. I was a bit worried about running stock injectors, though I knew if I upgraded them it'd definitely need a retune. I was hoping the factory ECU would compensate for a little extra air so long as I didn't crank the boost sky high just so I could get it running.
You should, larger turbos will have lower exhaust backpressure than the stock turbos even at lower boost. Less backpressure means an increase in volumetric efficiency so the same boost on a bigger turbo can make more power. Nistune as a minimum, link or haltech would be better.
If you have only pushed it to 3psi boost, it shouldn't be knock (detination) unless the engine is running really lean. Have you pulled the plugs and taken a look at them? This might give you some clues. Are they the plugs the correct heat range? What's the engine comp after the rebuild? Is it possible your fuel is off having had the car off the road for yonks? Are the cams setup correctly? Lots of things need to be checked and ruled out. Having said that, a tuneable ecu is a good investment to look after your new engine. I would be going for a Haltech.... so.. so easy to setup and tune
- Just pulled 3 of the plugs out now to have a look and all 3 have a bit of white/grey on the spark plug head. - The spark plugs are iridium NGK's BKR6EIX. - Not sure on engine compression after the rebuild, haven't tested it yet - Siphoned out the fuel tank when we had the fuel pump out and couldn't see any stale fuel left, since filled it with 98 - I guess the cams are set up correctly. How would I know if they're not? Here's a video of my engine and the noise it's making. I'm pretty sure it's not VTC related either. The noise seems to originate from the rear of the engine on the passenger’s side. After collecting a couple of opinions from the engine builder and a tuning shop I’ve been told the engine is mechanically sound and that the noise is coming from exhaust gas passing by a gasket either between the turbo and the manifold, the manifold and the block or between the turbo and the dump pipe. The advice I’ve been given at this point is to replace the gasket from the aluminium covered fibre type to a multi-layered steel type as the steel type resists blowing out better. However, the OEM style gasket is the fibre type… So it should be adequate?? I'm still sort of on the fence about it being the gasket. So thought I'd throw a video up here to get a few more perspectives.
Re gaskets the best you can use are the OE type for the applications you have listed. The manifold to head are a composite type, but the manifold to turbo and turbo to downpipe should be a single layer pressed steel gasket. All of that said that does not sound like an exhaust leak to me. I'm always somewhat reticient to give opinions on video as it gives no indication on where the sound is coming from etc, but that sounds like more like a stuck lifter. If you've paid to have that motor rebuilt I'd be goint back to the builder...
My opinion also, sounds like a lifter. (your car sounded normal to me) For me though it happens after oil change and takes a little a day or two to silence. Maybe give you car a bit of a drive, if you haven't done so already.
Thanks guys, appreciate your feedback. The guy who built the engine has come around and had a listen to it and seems to think it’s mechanically good and potentially the problem is to do with how the ECU is handling everything. It’s been driven about 150kms since the rebuild, which I’ve been hoping might free up a lifter as you were saying - in the case it’s a lifter. Would there be any harm in trying some sort of lifter cleaning oil additive, or trying something like heat range 7 spark plugs instead of 6’s?
Without knowing anything about the build or the builder... What exactly is it about the "way the ECU is handling everything" that he thinks is leading to that noise? I mean to me that sounds like a collapsed lifter. But please don't take that as shit canning anybody; as I said I don't know anything about the build or the builder and at the end of the day they are the one that should know the car, not some bloke on the internet lol. A lower heat range plug won't have any effect on the lifters or an exhaust leak (referring to your original diagnosis). Generally speaking no I don't think there would be any harm in a cleaning additive, however as I gather it's a fresh build I would speak to the builder before doing so as they may have a preferred "run in" procedure and you don't want to jeapordise any future warranty support.
I guess to him the ECU is a bit of a black box, same with me. We're not sure how it's handling slightly larger turbos, intercoolers and throttle bodies. That's why he wanted me to take it to a place that deals with ECU's and tuning to make sure it's not running lean and the air fuel ratios are right. The car is located in Mildura which is fairly rural, so it's a challenge getting anyone to take a thorough look at it as most places seem to not want to touch 300ZX's. Engine rebuild was 6 years ago, so I'm not really sure if the warranty still applies. The heads would've been reassembled with the original lifters, which in hindsight I should've replaced at the time. I think I'm leaning more towards it being a lifter now than it being an exhaust gasket. It can be driven around gently on the accelerator and not make the noise at all, it's only when you give the accelerator a stab that it'll rattle. In any case, it'll probably be easier to remove the timing belt, pull the plenum and check out the valves than it will be to swap out the exhaust gasket between the turbo and the engine. And, I've got a set of heads sitting around I can take the lifters out of too. Might just be a case of opening it up to inspect them. Though it's a bit sucky not knowing exactly what the issue is before commencing work to fix it, and the lifters potentially not having been inspected when the engine was reassembled.
If its a lifter problem, then you can easily determine this. Drain 1L of oil and add a bottle (1L) of Lucas Heavy Duty Oil treatment. This is great stuff, but not cheap. I can assure you it will quieten down any engine noise. I had a cam bridge failure on my Audi that would cause a top end noise when hot and on occassionaly bring up the oil warning on a very hot days. This stuff fixed the problem for a good 20,000kms. If I didn't add the Lucas oil at oil changes the noise was present. Finally traded the car with the problem masked. This stuff will shut up most engine noises and won't hurt the engine. I run about 1/2L with every oil change in all my cars.
Might be a case of trying the Lucas Oil out then. And I think pulling the lifters out will be on the cards too. I’m back in Melbourne now so I have some time to prepare before I go back to Mildura to try get it passed a roadworthy inspection (only thing stopping it passing last time was the tick). What things, if any things, need replacing along the path to reaching the valves? I’m thinking things like rocker cover gaskets are fine to reuse since they’re new, same for the plenum gasket.
