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So after reducing the second motor in my '86na to scrap earlier this year #2 bearing failure at hi speed...
I decided on doing a hybrid stroker engine similar to refresh951 based on Blown944's design https://rennlist.com/forums/944-turb...ker-build.html
Build Specs
Pistons: Speed Pro hypereutectic 383 stroker pistons - H860CP. +30 bore. -5cc
Rods: 2G DSM 95 - 99 Mitsubishi Eclipse OEM Connecting Rod 4g63T Turbo.
Sleeves: LA Sleeve p/n FL3209
Cometic Head Gasket C4273-040; MLS Stainless .040" 103.0mm bore.
83-89 Porsche 944 Crankshaft Crank Shaft - 2.5L Non-Turbo
Using the same calculator Refresh951 used on eagle rod dot com http://www.eaglerod.com/index.php?op...tpage&Itemid=1
with almost the same number as Refresh951 except I will have -5cc flat top piston vice his dished piston n not sure on the head cc but I should have a 10.58-1 to 10.09- 1 compression ratio
deck height and piston volume might change if machine shop cut the valve reliefs deep enough to make it a non-interference engine n the whole rotating assy balanced
will Be ran with MS II or MS III stand-alone or the F9tech dme http://www.ftech9.com/new-products/porsche-944-dme
So question what kinda Hp or Torque gains might I expect? IF ANY?
Just get another engine and then dry-sump it..Should eliminate #2 bearing problem. Save some $$...You might even consider (OH horrors!) an external oil line to feed just #2 bearing since the oiling system is somewhat suspect in these motors. just a thought.
The (snarky) answer to the hp and tq question is 0 and 0 without a cylinder head and camshaft��
Seriously though, to reap the benefit of increased displacement, especially without forced induction, the air flow in and out of the engine are the most critical variables to be solved.
The (snarky) answer to the hp and tq question is 0 and 0 without a cylinder head and camshaft��
Seriously though, to reap the benefit of increased displacement, especially without forced induction, the air flow in and out of the engine are the most critical variables to be solved.
Not really so snarky, there is no way to answer OP's question without knowing info about camshaft and recalculations due to rod angle/stroke/piston speed. etc., xx power level requires xx cfm support, etc., etc., etc.
Just get another engine and then dry-sump it..Should eliminate #2 bearing problem. Save some $$...You might even consider (OH horrors!) an external oil line to feed just #2 bearing since the oiling system is somewhat suspect in these motors. just a thought.
There have been so so many "theories" as to the #2 problem there could probably be a book written about it.
Your idea of an external line isn't so crazy.
Most people just state vaguely that "oil system sucks" or "pump will never work past 6000 rpms", etc., etc.
If the main source of problems would be the pump, then the farthest journal from the pump would be the one failing, not #2.
you're adding ~12% more displacement so you should reasonably be able to expect~12% more torque and maybe 12% more power, if the cylinder head can still feed the extra displacement at higher RPMs.
"technically" keeping the head/valves the same size with more displacement underneath should lower the max RPM range but i don't know that the 944NA is near its limit regarding valve size or not, i would think not.
it might be like the Ford 4.6 vs 5.4 (2-valve) engines...they used the same heads and cams and pistons, but the crank/rods/block were "bigger" to suit the 5.4 stroke....end result the 5.4 made proportionally more Torque than the 4.6 but they made right about the same HP overall.
The (snarky) answer to the hp and tq question is 0 and 0 without a cylinder head and camshaft��
Seriously though, to reap the benefit of increased displacement, especially without forced induction, the air flow in and out of the engine are the most critical variables to be solved.
Originally Posted by 951and944S
Not really so snarky, there is no way to answer OP's question without knowing info about camshaft and recalculations due to rod angle/stroke/piston speed. etc., xx power level requires xx cfm support, etc., etc., etc.
T
Stock Cam with a 4 deg advance I have a turbo header a friend gave me or maybe an aftermarket header but start out a stock one n maybe finish the Mustang TB install. With MS system the biggest limiting factor to airflow in the system is removed the airflow meter.
Max Rod angle 16.68deg
Rod Ratio 1.74:1
Mean Piston Speed @ 7000 rpm 65.8fps
I have roughly $1800 into it right now $1000 to the machine shop to start work and orders sleeves.
Pistons: Speed Pro hypereutectic 383 stroker pistons - H860CP. +30 bore. $176.99
Rods: 2G DSM 95 - 99 Mitsubishi Eclipse OEM Connecting Rod 4g63T Turbo. $135.00
Bearings /Misc: Cometic Head Gasket C4273-040; MLS Stainless .040" 103.0mm bore. $87.09
Porsche 924 944 Turbo REINZ Engine Block Gasket Set $149.70
MAIN BEARING SET STD. GLYCO Part# 944-101-901-00-AM $240.69
Haven't ordered rod bearings until machine shop says what size to order then will have them coated prob around $150
If I can get it done for less than the $3500 Refresh951 says it can be done for on a turbo it's worth it for me..
For those that say why not get another engine or why spend the money to keep it na. well I did get another engine that the PO says was rebuilt pulled to do an LS swap
had a shiny paint job on it that the balance shaft belt let go and wedged itself between the timing belt and the water pump 2 weeks after I installed it
and bent 3 out of 4 exhaust valve n 2 intake valves. $1000 for that motor #3 So if this works and I eliminate two of the Achilles heels of this motor I think its worth it.
If it was about the money most of us would have gotten rid of these cars a long time ago
Represh951 build numbers just that mine has a flat top piston so it has -5cc piston dome n 68cc head not sure about that. n divide engine size by 2 the calculator was set up for a V8 http://www.eaglerod.com/index.php?op...tpage&Itemid=1
you're adding ~12% more displacement so you should reasonably be able to expect~12% more torque and maybe 12% more power, if the cylinder head can still feed the extra displacement at higher RPMs.
"technically" keeping the head/valves the same size with more displacement underneath should lower the max RPM range but i don't know that the 944NA is near its limit regarding valve size or not, i would think not.
it might be like the Ford 4.6 vs 5.4 (2-valve) engines...they used the same heads and cams and pistons, but the crank/rods/block were "bigger" to suit the 5.4 stroke....end result the 5.4 made proportionally more Torque than the 4.6 but they made right about the same HP overall.
People are building 5.9 liter 928 engines with the same size valves making well over 400 crank hp. You can get 400 hp easily with just 5 liters in a 928 so a 200 hp NA build would be fairly easy for the head to deal with.
The AFM is the main restriction anyway, going with a MAF conversion or a MAP sensor on a standalone would make the biggest difference to flow.
11-09-2018, 03:07 AM
Hybrid NA motor build
