How to get more power out of NA, looking for 400hp ++
06-01-2011, 04:31 AM
#61
Pro
Thread Starter
Michael
DUMMY ASSEMBLY
A preliminary assembly prior to machining the deck surface allows a physical measurement of the piston to deck height.
The piston to head clearance is critical for quench and efficient combustion. Rod stretch at high RPM has to be considered, and experience dictates how close the piston can be to the head before contact at high RPM or during an over-rev.
Since the final compression ratio is affected by this clearance, it must be considered in the design stage, along with bore, stroke, combustion chamber volume, piston dome or dish volume, and head gasket thickness.
Once the preliminary piston to deck measurement is made, an exact amount of material is machined from the block’s deck surface.
The dummy assembly also provides an opportunity to discover any clearance or fit surprises in the rotating assembly, and to adjust the crank oil scraper clearance. This is particularly important with a stroker.
A preliminary assembly prior to machining the deck surface allows a physical measurement of the piston to deck height.
The piston to head clearance is critical for quench and efficient combustion. Rod stretch at high RPM has to be considered, and experience dictates how close the piston can be to the head before contact at high RPM or during an over-rev.
Since the final compression ratio is affected by this clearance, it must be considered in the design stage, along with bore, stroke, combustion chamber volume, piston dome or dish volume, and head gasket thickness.
Once the preliminary piston to deck measurement is made, an exact amount of material is machined from the block’s deck surface.
The dummy assembly also provides an opportunity to discover any clearance or fit surprises in the rotating assembly, and to adjust the crank oil scraper clearance. This is particularly important with a stroker.
06-01-2011, 04:34 AM
#62
Pro
Thread Starter
Michael
CYLINDER HEAD
There are a number of 944 4V heads to select among. The original 944S head had cracking issues due to a design flaw.
Although Porsche redesigned them, they kept the same part number. I don’t know how to avoid the bad ones but maybe someone on the forum can enlighten me.
The S2 head has moderate ports that flow quite well with minimum port work, better with larger valves.
An easy and effective upgrade is to fit 968 intake valves into S2 heads. The 968 head has larger intake ports and the largest intake valves.
A 968 head is being used for this effort since the intake port cross section is most suitable for the power level. Both intake and exhaust sides will be ported, and 41mm intake and 34mm exhaust valves fitted.
Caution here: Porting is a very specialized art that requires lots of experience and flow-bench testing. Performance can very easily be degraded with poor porting and/or low quality valve jobs. If you don’t have a flow bench or flow bench experience, best to leave them alone.
A custom billet cam “girdle” will be used to stabilize the valve train and protect the head. These are necessary with radical cam profiles and high RPM. Otherwise, the head will crack at the spark plug bore casting. This isn’t necessary with hydraulic camshafts since they typically don’t load the valve train as badly.
There are a number of 944 4V heads to select among. The original 944S head had cracking issues due to a design flaw.
Although Porsche redesigned them, they kept the same part number. I don’t know how to avoid the bad ones but maybe someone on the forum can enlighten me.
The S2 head has moderate ports that flow quite well with minimum port work, better with larger valves.
An easy and effective upgrade is to fit 968 intake valves into S2 heads. The 968 head has larger intake ports and the largest intake valves.
A 968 head is being used for this effort since the intake port cross section is most suitable for the power level. Both intake and exhaust sides will be ported, and 41mm intake and 34mm exhaust valves fitted.
Caution here: Porting is a very specialized art that requires lots of experience and flow-bench testing. Performance can very easily be degraded with poor porting and/or low quality valve jobs. If you don’t have a flow bench or flow bench experience, best to leave them alone.
A custom billet cam “girdle” will be used to stabilize the valve train and protect the head. These are necessary with radical cam profiles and high RPM. Otherwise, the head will crack at the spark plug bore casting. This isn’t necessary with hydraulic camshafts since they typically don’t load the valve train as badly.
06-01-2011, 04:35 AM
#63
Pro
Thread Starter
Michael
Oil to the lifter bores is blocked off since the solid lifters get plenty of oil from the cam journals, and we want to minimize oil in the engine that’s not lubricating something.
However, since cam chains have been known to break and make quite a mess of things, there’s an oil jet positioned to lube and cool the chain.
However, since cam chains have been known to break and make quite a mess of things, there’s an oil jet positioned to lube and cool the chain.
06-01-2011, 04:37 AM
#64
Pro
Thread Starter
Michael says
Excuse the soapbox moment: A good race engine is not a bolt-together project since appropriate tolerance is +/- .0002” (two ten-thousands)!
This can only be accomplished in a well-equipped engine machine shop with highly skilled machine operators.
Tools used for measurement alone represent many thousands of dollars, and the machines to create or correct dimensions are an investment difficult to justify outside of a very busy specialized engine shop.
Winning race teams and successful race shops very often farm their engine work out – even if they don’t always admit it.
Consider this before investing in engine modifications. Way too many failures result from fit or component issues that should be identified and addressed in the build stage.
At least let a competent specialized engine shop provide the machine work or perhaps provide a short-block and cylinder head.
Final assembly at that point is straight forward.
This can only be accomplished in a well-equipped engine machine shop with highly skilled machine operators.
Tools used for measurement alone represent many thousands of dollars, and the machines to create or correct dimensions are an investment difficult to justify outside of a very busy specialized engine shop.
Winning race teams and successful race shops very often farm their engine work out – even if they don’t always admit it.
Consider this before investing in engine modifications. Way too many failures result from fit or component issues that should be identified and addressed in the build stage.
At least let a competent specialized engine shop provide the machine work or perhaps provide a short-block and cylinder head.
Final assembly at that point is straight forward.
06-01-2011, 04:37 AM
#65
Pro
Thread Starter
Michael says
Enough for now.
I’ll update shortly and highlight additional areas:
Custom billet cams and followers
Dry sump oiling system
Intake manifold, throttle bodies, plenum
ECU – MoTeC
Tuning on the engine dyno
Maintenance in the field
Driver care
I’ll update shortly and highlight additional areas:
Custom billet cams and followers
Dry sump oiling system
Intake manifold, throttle bodies, plenum
ECU – MoTeC
Tuning on the engine dyno
Maintenance in the field
Driver care
06-01-2011, 06:29 AM
#68
That cam girdle is a very nice idea indeed.
I have far too many questions...
Will this build be using titanium valves and beryllium or powder metal valve seats? Ti valve springs?
Can you provide pics of the intake and exhaust ports from both valve and port side?
Are you using a gas-filled o-ring gasket?
What alloy are the rods made from? The pistons?
Have you done anything to improve cooling?
How long till we can hear/see this thing on video?!?
I have far too many questions...
Will this build be using titanium valves and beryllium or powder metal valve seats? Ti valve springs?
Can you provide pics of the intake and exhaust ports from both valve and port side?
Are you using a gas-filled o-ring gasket?
What alloy are the rods made from? The pistons?
Have you done anything to improve cooling?
How long till we can hear/see this thing on video?!?
06-02-2011, 02:30 AM
#71
Pro
Thread Starter
07-09-2011, 12:15 PM
#72
Pro
Thread Starter
Been quiet for a while, we (or better Michael Mount) is waiting for the itb's and inlet system. The dry sump is in, hope to make progress shortly. I'm waiting for Michael to give a bit more info on what's happening, but for now you have to do with a few pics.
Henk
Henk
07-09-2011, 12:54 PM
#73
Three Wheelin'
Wow! Just wow!
I have no doubt you will get the power you are after, as it sounds like it's almost as well planned as a NASA mission
I love how the motor literally has your name on it Henk
peace
Cyberpunky
I have no doubt you will get the power you are after, as it sounds like it's almost as well planned as a NASA mission
I love how the motor literally has your name on it Henk
peace
Cyberpunky
07-09-2011, 03:15 PM
#74
Nordschleife Master
