it never ends for me ..

 

looks like a may of blown a piston ...

 

soo its forged time looks like

but gonna be off the rd for a little time and going to

miss some shows looks like :(

 

any one got a good bottem end with forged parts they want to sell ?

piston?

piston / piston rings

part of your old tub somehow got into it?

Spoke to Turbo place and he explained how the oil can end up in the boost lines/exhaust with engine fail ...

he said if a piston had a Hole in it and turbo was on + boost this would pressurize the crank case and push the oil

back in to the turbo from the drain hole so oil is being forced from both ends of the tub so the only place for it to go

is though the shaft oil seal and in to the pipes ..

but hes all so said he would pick up and test and return the tubs for free

 

so as you can see cylinder 6 has melted and all so looks to be a small gasket leak

on from oil well to 5

 

sooo whats caused this ?

 

is it just the Temp of running the engine hard ?

the colour and carbon build up on all of the pistons would say are right ..

the bad piston/cylinder doesn't have scores on it but its transferred alloy from the piston

the ring looks intact but will know more when i strip lower block tomorrow

started at 6pm finished 9:30 taking it from Full engine to bare short block

what AFR were you running on boost?

 

Also, the oil would have come through the front PCV ports when the crankcase was being pressurised, so hopefully your turbo's are ok

AFR sits around 14>15 .... 16psi

 

thought about pcv valves but that wouldn't explain oil in the intercooler thats before inlet/pcv ...

AFR sits around 14>15 .... 16psi

 

thought about pcv valves but that wouldn't explain oil in the intercooler thats before inlet/pcv ...

 

no wonder it went pop, AFR should be 11-12 on boost

 

I referring to the ports on the front valve covers, connected to the IC piping

I may be wrong on that I will check tomorrow it could be 13/14 ... So u say its running lean if its not what u said .... So how

To get it to run more rich ?

no wonder it went pop, AFR should be 11-12 on boost

 

I referring to the ports on the front valve covers, connected to the IC piping

 

I agree James,that is a recipie for disaster,no wonder it went bang !! that piston has detonation damage for sure,if left it would have tracked down the side of the piston.The afr is well off.

Looks a bit better than mine did when it let go lol sadly nearly all pics of a fecked piston on here are from No.6, obviously on pre 94's.

Decent performing coolers keeping the intake charge temps down, good mapping or chip (such as JD) that runs a little richer when on boost will help prevent this kinda thing.

 

Bare that in mind when you do the rebuild and add N/A oil squirters too with using forged pistons and jobs a goodun.

 

Sadly a reflection of a 20 year old plus piston suffering on higher boost and not enough fuel.

smithy

Looks a bit better than mine did when it let go lol sadly nearly all pics of a fecked piston on here are from No.6, obviously on pre 94's.

Decent performing coolers keeping the intake charge temps down, good mapping or chip (such as JD) that runs a little richer when on boost will help prevent this kinda thing.

 

Bare that in mind when you do the rebuild and add N/A oil squirters too with using forged pistons and jobs a goodun.

 

Sadly a reflection of a 20 year old plus piston suffering on higher boost and not enough fuel.

smithy

 

Just to ask an obvious question that I'm sure everyone knows but me, how come pre 94's suffer from this issue with cylinder 6 but not post 94? What difference is there? I knew the injector rails were different but I thought that was all?

so just checked yes it was 14>15 on the AFR and that being limit of lean should be on around 11>12 like said before

but when i was doing some read ups it said 14>15 was normal for petrol cars ....

 

anyways so to get the afr right will need a remap right ?

 

and whats with the NA oil sprays thought the turbo ones was better ?

 

 

 

just found this info from this website

 

http://rusubaru.com/afrs-101/

 

 

 

AFRs 101

 

afrAFR stands for Air-to-Fuel Ratio, a mass ratio of air to fuel present during combustion and is measured by an oxygen (O2) sensor. It is extremely important to know what AFRs are and how they are used in tuning, or you will not be able to tune your car.

 

There are several common fuels used in automotive applications and each fuel has different properties. The properties you should know most about are the stoich value of the fuel mixture and Lambda.

 

Basically, stoich value is an Air-to-Fuel Ratio at which the given fuel undergoes complete combustion. This value also corresponds to Lambda value of 1.0 (Lambda 1.0 = complete combustion).

 

For example, gasoline has a stoich value of 14.7:1, this means that when 14.7 units of air get added to one unit of gasoline, that unit of gasoline undergoes complete combustion – when it’s done burning, there is no more gasoline left over. Lambda 1.0 for gasoline means that gasoline underwent complete combustion. Methanol, depending on your source, has a stoich value of 6.4:1 – it burns completely with only 6.4 units of air per unit of methanol.

 

Below is a table of stoich values for common fuels:

Fuel Stoich

Gasoline 14.7 : 1

Natural gas 17.2 : 1

Propane (LP) 15.5 : 1

Ethanol 9 : 1

Methanol 6.4 : 1

 

AFR values higher than stoich mean that you have a LEAN mixture, values lower than stoich mean that you have a RICH mixture. For example, for gasoline 16:1 mixture is lean, while 12.5:1 is rich. Leaner mixtures provide more power and hotter temperatures, thus increasing the chances to run into high exhaust gas temperatures (EGT), detonation and engine damage. richer mixtures tend to provide more torque and lower/safer combustion temperatures. Ideally, you want to run as lean as possible without running into high EGTs or detonation. Read more about EGTs

 

Side Note: At full load on a gasoline forced induction engine (without alcohol injection) an AFR reading of 12.5:1 indicates a leaner mixture, while 10.5:1 indicates a richer mixture. Good AFR for a forced induction engine at full load is 11.8:1.

 

Any fuel burning at its stoich understandably produces peak power, and generates a lot of heat. More heat than your engine can take at a full load. At full load you have to add more fuel than necessary for complete combustion – the extra fuel goes towards cooling the combustion process.

 

In forced induction engines under lots of boost and at full load, a lot of extra fuel has to be introduced to effectively cool the combustion process to sustainable temperatures. Exactly how much fuel you need to add for cooling is determined from your AFR readings.

 

On a forced induction gasoline engine you should be targeting 11.8:1 AFR for good power and efficient cooling. This 11.8:1 AFR corresponds to a Lambda value of 0.8 (think of it as 80%) – and this in turn means that at 11.8:1 AFR, 80% of gasoline undergoes combustion and 20% of the total gasoline injected into the cylinder goes towards cooling the combustion process.

 

With alcohol injection, you can use alcohol/water mix to replace those 20% of gasoline used for cooling. Alcohol/water is much more efficient at cooling that gasoline. Plus you’ll get a better fuel mileage. Read more about alcohol injection, tuning for alcohol injection and how much alcohol you can inject.

 

You cannot tune your car without knowing your AFR during the pull at any given point in the RPM range. Stock turbo Subarus come with a narrowband O2 sensor, which is only capable of reading AFRs from about 12.5:1 to about 15:1. In order to be able to tune your car, you will have to install a wideband AFR sensor, that will allow you to read AFRs from about 9:1 to about 25:1. Read more about the proper mod path.

 

To sum it all up:

 

AFR is air-to-fuel ratio

stoich value is an AFR at which the fuel burns completely

each type of fuel has a different stoich value

Lambda 1.0 means complete combustion for any given fuel, Lambda 0.8 means 80% fuel goes towards combustion, and 20% goes towards cooling the combustion process

alcohol/water mix injected into the cylinder provides much better cooling than extra gasoline

you must have a wideband oxygen (O2) sensor to be able to tune your car

Edited May 23, 201213 yr by MarkDerby

Injectors, fuel rail and lower plenum were changed. It was noticed the No.6 piston did not get quite as much fuel as the others. Nothing drastic that would effect a standard Zed, but once tuning running richer than norm would help compensate it.

 

N/A oil squirters direct the oil in a different direction to TT ones, given the design of forged piston tops, TT squirters do not direct the oil where needed the most. Again not a die hard thing you must do, but considering cost of parts and prolonging pistons and their performance, it is an ideal thing to do.

 

JD chips run richer than most when on boost to protect going lean and of course a custom map could be done to be even more accurate, knowing your intake charge temps is a massive bonus when using higher boost though and no using stock coolers with bigger tubs and injectors!

smithy

14.7 is good for NA's (or when turbo cars are idling/crusing)

 

This is the important bit from your write up

Side Note: At full load on a gasoline forced induction engine (without alcohol injection) an AFR reading of 12.5:1 indicates a leaner mixture, while 10.5:1 indicates a richer mixture. Good AFR for a forced induction engine at full load is 11.8:1.

 

In terms of chip, you need one for aftermarket turbo's that has maps to cover the extra airflow. Remember it's not the boost it measures, but the volume of air

understood .. i been waiting for JD to sort me a chip out ... abit more tailored to my car

but i know hes been away and biz but still waiting

any tips on how to get the Timing Belt Crank Sprocket Gear off ?

all the main crank pully is off doest want to budge

and i dont want to be wedging/prising against the oil pump

I had to grind a slot in mine, then chisel it and crack it, was a nightmare to get off, hope yours isn't like that tho, could try a bit of heat?....

had to cut and chisel it off ... but can swop it with another one ..

oh and i need a new oil pump i kinda damaged it :)

 

so here are some more piccys

 

Crank looks spot on No Marks on it what to ever

Beaings are good but worn out 2 are showing some brass

 

Piston 6 has a nice hole in it

Edited May 23, 201213 yr by MarkDerby

Jesus H!!! , that no6 is well fried!!! poor piston :(

can some one help decipher the main bearing sizes

as the main nissan one are done by each size but the acl are

done by one size

i worked out that my Rod bearings are all Standard size grade 0

 

 

http://www.twinturbo.net/nissan/300zx/FAQ/FAQpages/bearings.aspx

Edited May 23, 201213 yr by MarkDerby

List update

 

87.5mm Wiseco Pistons & eagle Rods.............................................. ..$1098

ARP Head/Main Stud Kit............................................... ....................$265

ACL STD Rod Bearings.......................................... ............................$55

ACL STD Main Bearings.......................................... ..........................$72

VTC Springs........................................... ..............................2x$18=$36

Full Engine Gaskets set inc Oil seals,valve seals and Cometic Head.........$355

Ring Comp.............................................. ........................................$17

PCV Valves............................................ ...............................2x$11=$22

Timing belt sprocket..........................................................................$24

OEM Oil Pump...................................................................................$170.56

NA Oil Jet's............................................................................3x$33..$99.00

 

Postal $170 with other parts in box

Total .................................................. ............................................$2383.25

 

Total UK .................................................. .......................................£1518.89

 

 

Main Block Rebore..........................................................................£180

Heads Skimming & Valve cut inc fitting all stem seals £100 Per Head = £200

 

 

Total Price up to date £ 1898.89

 

 

 

Mikey ( need to know Piston Size size )

Pistons are $595

egr delete $32

bit of p&p & duty if any

 

Gonzo ( need to know bearing size )

ACL Rod Bearings $55

ACL Main Bearings $72

bit of p&p & duty if any

 

Mikey, Gonzo i will be about ready to order by the end of the month

 

 

 

Is there anything more i should be thinking about ?

Edited May 23, 201213 yr by MarkDerby

Wow cant believe that piston! is the crank cracked too?

 

Mark you would benefit from a wideband and an Apexi SAFC2 so you can tweak the AFR to your requirements

crank is fine

 

 

u got one for sale ?

 

i have AFR wide band gauge ... but ..... i been reading it wrong :)

Edited May 23, 201213 yr by MarkDerby