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Does anyone know about expansion rate of cast vs forged pistons?
I'm just asking because I suspect Porsche ring gap on a 951 would be good enough for 18 psi, no?
I'm just wondering if the Rogue tuning car had a ring problem due to the cast piston itself expanding and the ring having no place to go.
Just trying to look from different angles.
Does anyone know about expansion rate of cast vs forged pistons?
I'm just asking because I suspect Porsche ring gap on a 951 would be good enough for 18 psi, no?
I'm just wondering if the Rogue tuning car had a ring problem due to the cast piston itself expanding and the ring having no place to go.
Just trying to look from different angles.
The Gap in the Rings should account for thermal expansion and cylinder pressure if the piston expands past the rings there would be damage to the side of the pistons where they made contact with the cylinder wall the grove in the piston for the rings are pretty deep just think about when you put the ring compressor on to install the pistons. https://forums.nasioc.com/forums/sho...20even%20close!
Quote from above website
For a long time, I've been a bit irritated by the explanation for the ten-fold increase in piston clearance given for forged pistons. A forged piston does not expand 10 times more than a dimensionally-identical cast piston at similar temperatures. In fact, it's not even close! (forged pistons often run cooler as well) You can check the data on various alloys for yourself at matweb.com if you like, but rest assured: there is no Aluminum alloy in existence that expands only 1/10th that of the 2618 T6 Aluminum JE forging alloy, and certainly no such amazing alloy used in-stock Subaru pistons.
This page seems to offer some good explanation, albeit indirect, as to why Forged pistons are given unnecessarily wider tolerances:
Quote:http://www.aa1car.com/library/2005/eb60522.htm
: Consequently, there's a common misconception that forged pistons always require greater skirt-to-wall clearances. This isn't always true because clearances depend on the type of alloy used in the piston, the design of the piston itself, and the profile of the piston. The coefficient of thermal expansion for some forged alloys is actually not much different than that of an ordinary cast piston. Consequently, thermal expansion can be controlled by machining the piston with a certain amount of "cam drop" so its shape conforms more closely to the cylinder bore as the piston gets hot. That's why all pistons (cast as well as forged) are slightly elliptic rather than round. The diameter of most pistons measures anywhere from .018" to .035" shorter across the wrist pin axis than along a line perpendicular to the pin. This compensates for the greater mass in the wrist pin area which causes the piston to swell sideways as it heats up. ^^^That leads me to believe that many manufacturers who recommend .0035" clearance for their 2618 forged pistons simply didn't design them as well as the factory designed the original castings, or have fallen prey to that common misconception. Either way, looks like bad juju to me, but maybe there is a good explanation? (problems with the Subaru blocks, machining limitations, sheer cost ... something?)
But what I really would like is for some vendors here to explain why they recommend a ten-fold increase in cylinder-bore clearance. What's the deal? If it's just too expensive to develop a piston-profile which can be given near-stock clearances, why not just duplicate the stock piston profile and use the stronger forging alloy?
Anyway, hope this has made for an interesting read ... if nothing else.
My NA is a '87 block, plan on using stock 87na rings just open the end gap to the max of what a turbo should be
I think your gap is in spec (as per Porsche 80's turbo spec) and you probably have proper turbo rings (based on my limited experience of disassembly of 1987 S and 1988 2v n/a). Personally, if you want to do this with cast higher compression parts, I'd just leave the piston rings alone. Keep in mind if you go overboard with filing gap, you can introduce other running problems.
Not bad mouth rouge but look at the blown-up picture there is no damage to the piston or compression of the ring groves I still stand by my assessment
that the added heat and pressure caused by pushing the stock rings 3+ times their design limit caused the rings to fail but the failure could have been avoided by opening
up the ring gap http://blog.wiseco.com/everything-yo...about-ring-gap
But thanks for posting the link it adds to my knowledge and anyone else that reads this that it is possible but you aren't going to build a hypercar with a stock NA motor.
I want a quicker car not, a HyperCar 600 HP 200 mph beast
Good article!
MO, I agree with your assessment of ring gap & suspect the latest Rogue article on the subject would be the most accurate.
It's interesting about the ring land chipping, though it appears (to me) to be a result of the ring bind.
Haha... Lets be honest, Rogue_Ant appears to be very power greedy with his demands of our cars!
But like the ***** or Samurai during wartime, a lot can be learned in their research.
Stage one complete
S2 flywheel bolted to 87 Na engine car starts and runs easily with diyautotune's S2 base map
but sadly don't I don't think this motor will be getting a turbo while I had the motor out dropped the pan
N found #2 rodend loose pulled end cap n found the bearing had spun replaced bearing because
I needed to get the car out of the shop and I have a work trip coming up.
But the engine runs on the new flywheel and the MS3Pro Module with my custom interface board
The setup:
MS3Pro Module ICV PWM, Single coil, external MAP for Alt correction knock sensor
Injectors: 4 Bosch 0-280-150-431 30 lbs/hr at 36.26psi.
Latency (dead time)@ 12volts=0.621 ms @ 13volts=0.506 ms @ 14volts=0.391 ms.
Crank Sensor Stock 944 Crank Angle sensor 110 deg
IAT Sensor Stock 944 Stock AFM barndoor locked wide open
TPS Sensor Stock 951
CLT Sensor Stock 944
KNOCK Sensor Stock 951
944 DME Male connector 825213-1 35 POS TAB HOUSING http://www.te.com/usa-en/home.html or https://www.connectorpeople.com/Conn...ITY/8/825213-1
Wide Band O2 Sensor Controller Spartan 2 OEM from 14Point7 http://www.14point7.com/products/spartan-2-oem
O2 Sensor Bosch LSU 4.9 Wideband O2 Sensor
Idle Control Valve Bosch 2 wire Idle Control Valve from a Volvo p/n GEGT7610-324
2nd Map sensor MPX4250A/MPXA4250A series piezoresistive transducer is a state–of–the–art
monolithic silicon pressure sensor
951 TPS connector TE Internal #: 282236-2 TE Internal Description: 6 POS. SPLASH PROOF CONN ASSY
Ignition Driver Bosch BIP373power transistor
The 2 prototype boards one for a NA only and one for turbo or NA back of dual board Will have Bluetooth and USB C also shows Dual VR conditioner board one input wired to Speed sensor other will be wired into the transmission speed sensor MS3 Pro mounted to Turbo board connector on the side if for the KLR plug Back of NA board showing USB C led for coil firing Map sensor and Baro sensor. the 2 green wires are the leads to injectors if using stock injectors I would need resistors installed.
Dwizle,
Cool of you to share & be so transparent with the details (no doubt other can benefit from your research).
Great to hear the car runs. The crankshaft is still okay?
In a bit of reading about oil pressure and bearing cap in our cars, I have read it's more of tendency for this type of failure from high rpm.
Dwizle,
Cool of you to share & be so transparent with the details (no doubt other can benefit from your research).
Great to hear the car runs. The crankshaft is still okay?
In a bit of reading about oil pressure and bearing cap in our cars, I have read it's more of tendency for this type of failure from high rpm.
Wouldn't be here if others hadn't shared their ideas their successes n failures especially their failures to me those are the best teachers.
Up date
To those who said just put the turbo motor in the NA......
So Plans changed got tired of looking at the turbo sitting in the drive way n the Na Motor ate another set of #2 bearings
the turbo motor now resides in the NA body
Specifics
88T motor
AFM still installed but fixed wide open anybody got a dead turbo AFM? so I can gut it hate to destroy a good part
S2 fly wheel and clutch
MSPNP2 using S2 Harness GM IAT plumbed just before throttle body 14point7.com Wideband controller and Bosch wideband sensor
Aftermarket header panel to aid in airflow to stock turbo intercooler along GTR style headlights
After market Oil cooler mounted in front of Radiator Things left to do: wire up Aux pump for turbo using a pump from a VW only $54 bucks but has a funky plug
Build My Digital dash either a pie dash or Realdash run on windows or android using a single board computer
will Swap in NA pistons at some point.
Drill holes in bumper around front Lic plate for additional airflow to IC
New question will a turbo Differential fit in a NA Transmission saw one for sale on eBay and I have blown up NA trans in storage So I was thinking??? Turbo Diff
Or My next Mod when the Stock NA trans takes a **** is a 6 speed from Boxster S
Car already has Volvo 4 piston front brakes thinking of plumbing in a turbo brake bias valve into the system
I am showing up to this thread late. I have done a turbo motor into NA car conversion before. I also have seen a NA engine get turbo'ed and blown up due to the high compression.
The turbo gear box will bolt right into your NA and it is beefier. The gear ratio works better for the turbo if you have the one out of the 88. I didn't read through all the posts but this is what you want.
The 88 turbo suspension/brakes/struts/sway bars transfer straight over to the 86. I have done that a few times. You will need the 88 rack or at least change out the tie rods.
If you get a car from the police impound and lost the paperwork, get a lien sale service company to come out and lien sale the car from your property. A lien sale packet supercedes a title and the only paperwork that supercedes a lien sale packet is a court order signed by a judge. You will need that paperwork even to scrap the 88 shell once you get done picking it apart.
I am showing up to this thread late. I have done a turbo motor into NA car conversion before. I also have seen a NA engine get turbo'ed and blown up due to the high compression..
How much boost were they running? was the car properly tuned? ` do you have pictures
Originally Posted by Legoland951
The turbo gear box will bolt right into your NA and it is beefier. The gear ratio works better for the turbo if you have the one out of the 88. I didn't read through all the posts but this is what you want..
I get That. I guess I asked the question the wrong way I meant the differential and pinion gear isn't that the weak spot for the na transmissions?
Originally Posted by Legoland951
The 88 turbo suspension/brakes/struts/sway bars transfer straight over to the 86. I have done that a few times. You will need the 88 rack or at least change out the tie rods.
If you get a car from the police impound and lost the paperwork, get a lien sale service company to come out and lien sale the car from your property. A lien sale packet supercedes a title and the only paperwork that supercedes a lien sale packet is a court order signed by a judge. You will need that paperwork even to scrap the 88 shell once you get done picking it apart.
Thanks for the info Keeping turbo body intact maybe do VW/Audi 5 cylinders swap n make it a race car
12-08-2020, 09:25 AM
(problems with the Subaru blocks, machining limitations, sheer cost ... something?)
