Engine failure - swap compatibility?

[Skifey]

Hey hey everyone,

Your local muppet here again with a wonderful new situation!

For anyone who knows my car history; yes, this is the same Mx5 that has been overheating for over a year now. This I believe is a whole new issue. I had tappet noise for a month or so during February/March but didn't deign to change/flush the oil - not enough time amidst work and the usual life dramas. March 24th I believe, I started her up and she made a odd rattle for maybe 1 or 2 seconds; sounded a bit like something bouncing around inside a can. Returned to the normal purr and I drove to work no dramas (~35km). Finished worked 10 hours later, started her up and it did the EXACT same thing so I drove her home and parked it for the night. The following morning!... I start it up, it makes the same 'ball-in-a-tin-can' noise for a bit longer than the previous 2 times and the engine stalls abruptly. I try starting it up again and it made some lovely cranking, tapping, banging noises and refused to crank properly. Just makes a whirring noise like the battery is trying to push the starter motor but nothing is happening.

Suspicision
I've spoken to 3 mechanics and they all concur/guessed the same.
It's dropped a valve or something else wonderful into the cylinder. It's bounced around and ruined any and/or all of the following; cylinder head, piston, rod, valve seat, valve rod. Engine's gonna have to come out to inspect or have the head removed and something's gonna need serious work. I'm expecting a necessary engine rebuild or replacement. Correct me if you think I'm wrong, I'm begging you!

Moving forward, assuming I'm correct is my suspicion even to the smallest degree, I've been led to believe it's going to be MORE cost effective to simply rip and replace the existing engine with a secondhand or refurbished one as opposed to rebuilding the current one myself. Cheapest refurbished I've been able to find was 4k + freight + exchange of existing so NOPE. I've been able to source a BP-Z3 from Melbourne, it'll cost me 2k totat and that to me sounds like a better option. Got ~110,000km on it apparently.

My questions;
- Given the symptoms is it worth confirming the damage to the current engine before I jump to conclusions? If so, how would you do this? Another consideration is that this is my daily and I need transport again asap.
- If I buy the BP-Z3, is the swap even compatible? For exact car details that I'm sure you'll all ask, I'll leave details below.

As always, any help and advice is greatly appreciated! Questions; fire away!

===CAR HISTORY & FACTS===
- 1990 Mx5 NA
- Was converted from 1.6 to a 1.8 in 2013 so already has all the necessary electrical and mechanic bits swapped over to cater for the BP1.8-4W
- Has a megasquirt installed but not tuned well by the previous owner

[hks_kansei]

The fastest and cheapest repair will be to just swap a running engine into it.

To properly rebuild an engine will cost you a few thousand.
There's about $1k in machining work for the head and block, and that's for a head that's just needing a freshen up.
If yours is mangled from a dropped valve (probably) then you'll likely need a replacement head anyway.

Then there's a few hundred on top in new pistons, more for gaskets, etc etc.


A secondhand engine that runs fine is in the $1000-2000 range.
Plus, it can be installed in a weekend, rather than the usual week or two turnaround for a machine shop.



Since you have a standalone ECU you can really put in anything, but if it's not the same as what you had in before you'll need to re-tune.
And obviously you'll need to make some minor changes for different plugs etc on the new engine.



So far as pulling the old one apart, i'd certainly do that after it's removed.
Both for curiosity, and also to gauge the damage so you can sell it if you have no use for it.

You can also buy/borrow a borescope and pop it down a spark plug hole to see inside and spot a potential cause.
if it did drop a valve you'll likely see either the end of the valve, or smashed bits of it. and a LOT of chips/dents/marks where it's bounced around and hammered into stuff.

[hks_kansei]

Short answer.

Since time/money is a factor, buy a secondhand engine that is ready to run and throw that in.



Also, organise to have it tuned properly.
if the tune sucks it can cause damage, if it's been knocking that can do things like bend a rod, or if it's too lean it can run wayy too hot and burn valves (which can increase the risk of one breaking), too rich it can wash the oil film off the bore and cause the rings to chew out the cylinder walls, etc etc.

Replacing an engine and leaving a rubbish tune on it would be like having a heart attack, then having a triple bypass and walking straight from the hospital into the nearest bottle shop to grab a slab of beer and a pack of smokes.

[manga_blue]

You could do a bit more diagnosis by putting an endoscope down each of the plug holes and having a look around - but I don't think it'll tell you anything you don't already know.

New motor is the fastest and cheapest way forward. Then you can salvage and sell bits from the old motor at your leisure.

[Skifey]

Already having received your two responses I'm leaning towards the rip and replace option as it seems like the most cost and time effective solution. Let's assume I do this. The engine in question is a 1.8L BP-Z3 from an NB 2001 or 2002 model. I've spoken to seller and he's been super helpful in answering my questions. He thinks it should be a relatively simple take out and drop in swap. He said he's done the swap himself in the past on a previous Mx5 he owned. The only question being as to whether or not my Megasquirt ECU will run the VVT on the engine. I'm not fussed about that as it should still run regardless. Granted I'm going to have to download the software and give it a half decent self tune or take it to a tuner because it would be stupid not to.

What I AM fussed about is not being compatible with other electrics, fueling and anything else I can't think of. Is it perfectly fine to swap in this exact engine model without dramas?

It also doesn't come with an AC compressor, an alternator, a clutch and the exhaust. I should be fine to reuse my existing ones right? I've done digging across the net for these questions but I can't seem to find any threads anywhere that reference this exact engine going into a 1990 NA.

I'm a bit scared; it all sounds a bit too simple and I'm worried that I'm underestimating or overlooking potential difficulties

[StanTheMan]

I’d pull the head off & check before you remove the whole engine


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[StanTheMan]

Ms2 will not run VVT by itself
MS3 will


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[hks_kansei]

It also doesn't come with an AC compressor, an alternator, a clutch and the exhaust. I should be fine to reuse my existing ones right? I've done digging across the net for these questions but I can't seem to find any threads anywhere that reference this exact engine going into a 1990 NA.:

Clutch will fit, since all you need to keep matched are the flywheel and clutch, both need to be either 1.6 or 1.8 sized.
as long as you keep the two together either will fit on the engine.

Exhaust will bolt up to the engine fine, NA8 right through to NB8C had the same exhaust ports etc.
SO long as you keep your current headers and everything it will be fine.
EGR likely wont fit, but since you're using a megasquirt it can simply be blocked off and not used (and may already be)




so far as VVT etc, double check your megasquirt version since I think the earlier ones didnt have the ability to control VVT (not sure if that means they wont run, or if it just means the variable bit of the VVT doesnt vary)

[StanTheMan]

Ms2 does not have vvt controll. You will need a seperate box which controls the VVT. It can be piggy backed on the MS2


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[Aiming Faster]

I installed VVT head onto an NB8A, the oil line takes up space behind the head (to firewall). I got VVT coils to fix that. If your oil guage was 'real', reuse the sender from the old engine too.

[project.r.racing]

I would confirm what the issue is before taking the next step of buying a whole new engine.

BP engines are not known for dropping valves into the piston chamber. I am not saying a retaining clip breakage cannot happen. But if I went to a mechanic and has dealt with old Fords and Holdens most of their lives, then that is the standard response I would assume I would get.

[Skifey]

I’d pull the head off & check before you remove the whole engine

I would confirm what the issue is before taking the next step of buying a whole new engine.

My only qualm is the time and effort (I've never taken a head off myself) involved in doing this versus the likelihood I know that the BPs are pretty solid and like you said, aren't known for this sort of thing and I concur. I also have to consider the fact that my engine has been running hot for a year or so... god only knows what components I've worn out by doing this.

Ms2 does not have vvt controll. You will need a seperate box which controls the VVT. It can be piggy backed on the MS2

Ah, this one is my crux. I cannot seem to identify what MS I even have. I've got a photo of it which I'll drop below. It's just a black box; possibly the logo has been rubbed off over time? Let's assume I have a MS2 or earlier, where do I get this 'seperate box' that you speak of and does it have a part name?

Along the same vein, is there a place in which I can source base maps/tunes for the megasquirt? My googling has given me little reliable answers. I understand that if I go doing this I need to be using a map based off as close to the same configuration as possible. I.e. same engine, same injectors, same everything

[StanTheMan]

Google VVT control box.
or go to https://www.diyautotune.com/product/vvtuner-valve-timing-control-unit-assembled/

or open your current MS box.....maybe there are some hints. coiuld also be a DIY unit. If you have Tuner studios perhaps this will also give you a hint.

MS2.png

look right at the top. In my case there is MS2 Extra

[StanTheMan]

I know its your Daily.

dont rush into this. You will need some research especially how to intsall & make the VVT control box work. Its not going to be a weekend job.

I'm not suggesting you are like me....
when I decided to refresh, Port & Polish my head....I extpected 3-4 weks.
It took me 3 months.

When I did a BP4W NA6 Chassis conversion total head rework & lots of other stuff I figured 3-4 months. Itr took me 15 months.

lots of sh*t happened between drinks if you get my drift.

Talking the head off is relatively easy....but time pressure in these things is not good. Shortcuts happen....Rushing & taking shortcuts is a recipe for disaster
unless you can find something similare on the local market.....the VVT box will take 2 weeks by itself....and thats only if your research leads you to this box
not suggesting you should plan 15 mths. I suggesting to do it right....even if you get someone else to install the engine....it's going to take 3-4 weeks.

[Skifey]

I know its your Daily.

dont rush into this. You will need some research especially how to intsall & make the VVT control box work. Its not going to be a weekend job.

Ahh mate, trust me I really don't want to rush into this and I'm trying to be as forward thinking and calculative as possible but my options here are limited - the usual 'life' stuff is forcing my hand more than a little.

It does seem though that the biggest concern for me if I go ahead with this will be the VVT compatibility?

Am I right in thinking this is the part I'm going to need if/once I confirm that my Megasquirt isn't going to support my VVT? Serious question before you even answer that though; Is there any major problem with simply not running the VVT? Won't I just not have variance?

https://www.diyautotune.com/product/vvt ... assembled/