9m93RS Clubsport GT2 look: Engine
11-25-2008, 01:18 AM
#17
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For a pure street car that has occasional track use, at this time I would specify the standard length rod & skirt over the short slipper version purely on the grounds of longevity and noise. Reduced high rpm friction is the advantage of the longer rod and short piston, which is not as important a requirement for a street engine as a race engine which spends all its life above 6500rpm. Similarly, because the slipper piston is short it has to run thin rings in order to fit them into a smaller space, unfortunately the rings we can (currently) buy don't have the same life expectancy as regular ring packs. Geoffrey's engine is a case in point where the original Mahle pistons and rings lasted comfortably for 100 hours, whereas the expectancy of the slipper ring pack will be half that.
The second question is the more complicated one. The simple truth is that when you are designing any engine from a fixed set of components you have to evaluate the full potential of each component in the "system" that affects the efficiency of the engine, then design the engine around the limitations that you discover. In the case of the stock 993 Varioram manifold, with a few simple porting modifications we have found that it will comfortably support 3.6 and 3.8 engines at up to 360hp (with billet heads and sport cams). From my experience with the non-Varioram system I would say that, even after fitting a better exhaust system, to take these engines further would require longer duration cams and at this point you will probably hit issues with idle stability should you choose to run with more overlap (which is the usual approach), hence why I recommend ITB's as the next step. I dare say that given enough time and money we could design & develop a cam to max out the performance of the VR manifold but from what I can deduce the current 9m Sport cam is not too far away from ideal.
Does this answer your questions?
The second question is the more complicated one. The simple truth is that when you are designing any engine from a fixed set of components you have to evaluate the full potential of each component in the "system" that affects the efficiency of the engine, then design the engine around the limitations that you discover. In the case of the stock 993 Varioram manifold, with a few simple porting modifications we have found that it will comfortably support 3.6 and 3.8 engines at up to 360hp (with billet heads and sport cams). From my experience with the non-Varioram system I would say that, even after fitting a better exhaust system, to take these engines further would require longer duration cams and at this point you will probably hit issues with idle stability should you choose to run with more overlap (which is the usual approach), hence why I recommend ITB's as the next step. I dare say that given enough time and money we could design & develop a cam to max out the performance of the VR manifold but from what I can deduce the current 9m Sport cam is not too far away from ideal.
Does this answer your questions?
Thanks Colin. I'm looking forward to seeing how this project progresses and thanks for posting. I really enjoy these threads.
Cheers,
Doug
11-25-2008, 11:22 AM
#18
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When you say 100hours above, are you talking about stock engine or something else?
If one drives 100km/h for 100 hours, it equals 10,000km's. That isn't alot is it?
What kind of life expectancy would a completely rebuild 993 engine (stock bottom) with a healthy 9m top package (billet heads, cams etc.) have if driven 70% track 30% street?
Thanks!
Juha
If one drives 100km/h for 100 hours, it equals 10,000km's. That isn't alot is it?
What kind of life expectancy would a completely rebuild 993 engine (stock bottom) with a healthy 9m top package (billet heads, cams etc.) have if driven 70% track 30% street?
Thanks!
Juha
It is customary to life a race engine on the number of hours it can do flat out in the power band, which is the 100 hours that Geoffrey's engine has done to which I was referring. I would expect the short skirt piston to last 100 hours, but the rings will probably be tired after 40-50hrs and therefore should be replaced at that point - which is pretty similar to a 996GT3 Cup engine running similar thickness rings. In terms of road use this could easily be 50,000 miles or 10,000 miles, depends on how fast you drive it.
With respect to a street conversion, if we built a typical 9m 993+2 with billet heads, sport cams and new stock pistons & cylinders, the minimum I would expect the same life as a new standard engine - all things being equal. We found power from this combination with improved intake and combustion efficiency, so think about it in terms of less power disappearing down the exhaust pipe rather than pushing the engine harder. The only other consideration is that we use a rather special sintered material for the valve guides and seats, so we expect valve guide wear to be significantly reduced in comparison to the standard Porsche items. As proof in point, the first two 9m 993+2 conversions are still going strong 30,000 miles after the rebuild (one at 89k, other at 98k) and neither of these engines had pistons and cylinders, we just re-ringed them.
11-25-2008, 01:47 PM
#19
Burning Brakes
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Are these in the states? Any dyno results? Cost? turnaround time? Thanks
11-25-2008, 02:04 PM
#20
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https://rennlist.com/forums/showthre...=9m+993+billet
By all means come back to me with another thread or pm if you cannot find the info.
Meanwhile I'll be posting more photos of the assembled engine later tonight, I think you will all like what you see. Should be in the car and on the dyno sometime tomorrow or Thursday, so I'll also be posting the dyno results at the end of the week (I'm expecting 400+ at the flywheel on our rollers).
11-25-2008, 02:55 PM
#21
Nordschleife Master
Geoffrey's engine is a case in point where the original Mahle pistons and rings lasted comfortably for 100 hours, whereas the expectancy of the slipper ring pack will be half that.
I disagree with Colin that his slipper pistons would last 1/2 that, I expect 100 hours with a good cylinder. In my new engine build, I will be testing that theory since I will be running a version of his slipper piston in an effort to reduce weight and utilize a longer, lighter connecting rod. This should also fix the rod bearing wear.
BTW, the engine ran on 93 octane street fuel at 12.0:1 compression.
. I have plans for 9M heads.. Most likely, if I don't end up with a TT instead..
11-25-2008, 07:22 PM
#25
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Thanks for the thumbs up guys, hopefully you will all say the same when our 500hp n/a GT3 hits the road sometime next year?
Back to the plot, here are the photos of the remainder of the engine build, the only thing of note being the use of two dial gauges to set the cams more accurately. I always make a point of dialing in the intake and the exhaust lift at TDC simultaneously so that we can split the error of the cam. In this case I managed to get the left cam accurate to 0.001" on intake and exhaust (both +, inferring fractionally narrow lobe centres) whereas the right cam split the error at 0.0005" on each lobe.
Of course the other problem with having an engine in parts is that Marc and Miles (9m Panelcraft) get to rifle through the shelf and start painting anything that's not machined.... the colour is obviously Candy Apple Red, the same as the calipers and anti-roll bars.
Back to the plot, here are the photos of the remainder of the engine build, the only thing of note being the use of two dial gauges to set the cams more accurately. I always make a point of dialing in the intake and the exhaust lift at TDC simultaneously so that we can split the error of the cam. In this case I managed to get the left cam accurate to 0.001" on intake and exhaust (both +, inferring fractionally narrow lobe centres) whereas the right cam split the error at 0.0005" on each lobe.
Of course the other problem with having an engine in parts is that Marc and Miles (9m Panelcraft) get to rifle through the shelf and start painting anything that's not machined.... the colour is obviously Candy Apple Red, the same as the calipers and anti-roll bars.
11-25-2008, 07:41 PM
#27
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Next up is the 9m Individual Throttle Body intake system. This is true to form for 9m as the manifolds are CNC machined from billet so that we can get the optimum length and taper for the stack and location of the throttle plate, the throttle bodies also being internally tapered. On top are some rather attractive carbon air horns hidden under the foam filters, and if you look closely you should also note the 9m twin throttle cable bellcrank assembly mounted above the engine breather tower - the bracket incorporates holes to affix the wiring loom safely under the mechanism, takes the stock 964/993 throttle cable grommet mounting & cable end fixing.
On top of the heads we first fit CNC machined plates to insulate the intake manifold from the heat of the cylinder heads, in the photo of the engine with the single manifold fitted on number 4 cylinder you can see a haft sticking out of the top of the manifold. This is our tapered alignment tool to ensure a perfect alignment between the manifold, insulator and intake port.
The wiring loom is a stripped down factory engine loom, the superfluous injectors plugs, heater fan/resistor, secondary air pump, res flap & varioram plugs having been carefully removed and the loom rebound with the factory cloth tape. The injector wires are now carried in the car's new 9m Motec loom of course.
On top of the heads we first fit CNC machined plates to insulate the intake manifold from the heat of the cylinder heads, in the photo of the engine with the single manifold fitted on number 4 cylinder you can see a haft sticking out of the top of the manifold. This is our tapered alignment tool to ensure a perfect alignment between the manifold, insulator and intake port.
The wiring loom is a stripped down factory engine loom, the superfluous injectors plugs, heater fan/resistor, secondary air pump, res flap & varioram plugs having been carefully removed and the loom rebound with the factory cloth tape. The injector wires are now carried in the car's new 9m Motec loom of course.
11-25-2008, 07:47 PM
#28
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And here is the finished result, minus distributor, leads, exhaust and air cleaners. I get a sense of pride with every engine we complete, however I must admit that this one is a little bit extra special to look at thanks to the efforts of M&M and the owner who has given us the time to get it looking so sweet.
11-25-2008, 08:31 PM
#30
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Colin, you're brave leaving that distr hole sitting open... Or maybe you took the tape off for pics.
What do the high intake stacks do? Injectors are very high.
What do the high intake stacks do? Injectors are very high.