Engine damage

WideOpenThrottle · Post by **WideOpenThrottle** » Fri Dec 27, 2013 9:19 am

Pulled the head off a mates 1600 mx5 that had been running untuned from a previous owner.It suffered full loss of compression in #1 with partial loss of comp' in #3.
The oil in the other bores was put there to test how good the rings seal each piston as a guide to damage.
The pics says it all as there is evidence of detonation as well as the unusual smooth hole at the rear of the #1 piston where you can see the piston ring.
We are now looking at options of a rebuild or another good 2nd hand motor so if any one has one please let me know.Cheers.

4A-GE · Post by **4A-GE** » Fri Dec 27, 2013 10:01 am

My god, that poor car.

SLYDIT · Post by **SLYDIT** » Fri Dec 27, 2013 9:53 pm

Just chuck another engine in there. The 1600's are pretty idiot proof. No point 'building,' a 1600 up.

Mazda-mender · Post by **Mazda-mender** » Sat Dec 28, 2013 12:09 am

Agreed
Not worth messing with, just throw another low mileage enginge back, far cheaper in the long run.
M-m

Snapfrozen · Post by **Snapfrozen** » Sat Dec 28, 2013 7:48 am

For the flipside of the argument. If you know how to rebuild it, the head is in good Nick and the bores are fine I would rebuild it. It really only needs new pistons, rings, hg and any other maintenance items. If you're doing s full rebuild you've got a nice fresh motor. If you are buying another 2nd hand you've got no guarantees as to the quality of it other than visual external inspection

SLYDIT · Post by **SLYDIT** » Sat Dec 28, 2013 8:46 am

If its detonated that bad. I would bet that the rod and main bearings will be stuffed too.
Another engine with a new head gasket and cam belt kit before you drop it in.

Is it turbo or supercharged? If its just NA then drop in a 1800 NB ENGINE and retune

WideOpenThrottle · Post by **WideOpenThrottle** » Sat Dec 28, 2013 8:59 am

Another motor is by far the cheapest and easiest but I know from experience its hard to find one that you could honestly say is a good one.

#1 bore is a definite re-bore as it is quite bad and may be too deep in damage to re-bore as I believe the walls are quite thin in these engines.

Good point about the bearings too!

4A-GE · Post by **4A-GE** » Sat Dec 28, 2013 9:07 am

WideOpenThrottle · Post by **WideOpenThrottle** » Sat Dec 28, 2013 9:09 am

Yeah!...need something like that!

SLYDIT · Post by **SLYDIT** » Sat Dec 28, 2013 9:31 am

What's the ecu? What sort of boost level?

WideOpenThrottle · Post by **WideOpenThrottle** » Sat Dec 28, 2013 12:22 pm

Older link hoping for around 12psi boost but will be dependent on a dyno.

4A-GE · Post by **4A-GE** » Sat Dec 28, 2013 8:16 pm

WideOpenThrottle wrote:Yeah!...need something like that!

It'd be carnage, but at least you'd die happy.

SLYDIT · Post by **SLYDIT** » Sun Dec 29, 2013 12:40 pm

at least youll be able to get some good timing maps for that old link from Miataturbo.net or the other one. plenty of map sharing on there. if your gonna try for 12psi then get some 2002+ WRX injectors....better spray pattern for idle and yet they can deliver the goods. those crappy old RX7 injectors just dont cut it now days.

WideOpenThrottle · Post by **WideOpenThrottle** » Sun Dec 29, 2013 1:04 pm

Been told the injectors are 550cc RX7 ones so good for high boost/hp I should think.

SLYDIT · Post by **SLYDIT** » Sun Dec 29, 2013 4:48 pm

yes but they idle like crap and transition poorly compared to the new EV6 and EV14 injectors... some WRX sti pink injectors are a VAAAAST improvement. also the rx7 injectors are from the "hot" part of the engine, so life isnt great. if your gonna retune, get some STI injectors and reap the better idle and cruise.

WideOpenThrottle · Post by **WideOpenThrottle** » Sun Dec 29, 2013 5:39 pm

Is it just the RX7 ones that idle like crap? as I have some 550's in my car that I got from the states that Begi sells and they are smooth as silk.

The car did have a bit of a funny idle and was a bit smokey although compressions apparently were fine not so long ago.

SLYDIT · Post by **SLYDIT** » Sun Dec 29, 2013 7:08 pm

those old style 550's just cant atomise the fuel properly at low dutycycles. its even worse if you dont have your injector dead time setup or the injector timing setup correctly( not even sure if you can set injector timing in an old link??) the new EV6 and EV14 injectors have a far superior spray pattern and dead time characteristics... i am assuming the FM injectors are red denso injectors similar to the old mitsi 550's? those that have upgraded to the new style injectors rave about the smooth idle and low rpm response.

2low2c · Post by **2low2c** » Sun Dec 29, 2013 7:29 pm

i have been running rx7 550s for 12 years and always have a smooth idle and low end response is good

Teamjelly · Post by **Teamjelly** » Sun Dec 29, 2013 8:45 pm

Couldn't agree with Slydit's comments more
Many a time I've removed the old school RX7 550c (or similar) injectors due to having fluctuating idle, light load/cruise issues
Fitted new style plastic 425cc or 530cc injectors and made the world of difference
No more 12:1 Air ratios needed to idle smoothly
As a bonus they atomise the fuel much better that economy and power will increase.
It's evident in the injector opening/closing time, Old style metal body types (that's including NA6 injectors) need 0.9-1.2ms yet the slimline plastic ones can do it in 0.6ms
Which is why I just ordered 300 more of them.

At $60 each for a brand new 530cc injector with seal kit you can't really go wrong,

SLYDIT · Post by **SLYDIT** » Sun Dec 29, 2013 10:29 pm

ah and your in tauranga too.....may have to come pay a visit.

dian1111 · Post by **dian1111** » Tue Jan 28, 2014 1:14 am

This topic is very usefully for me

Thank you

Engine damage

Engine damage

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