3.8 Engine rebuild
04-27-2012, 08:39 AM
#31
Rennlist Member
Just drop the car and a check for $xx,xxx (I don't have a lb symbol) with Colin and tell him to do the most w/ that $ be and done with it. 
That is what I would do if I lived there.
That is what I would do if I lived there.
04-27-2012, 10:55 AM
#32
Nordschleife Master
On a more serious note, why wouldn't you go to 3.8 if you're rebuilding? I'm sure it has been discussed at great length before but it seems topical to this thread since the additional cost is little to nothing if the P&Cs are being replaced anyway?
EDIT: What I mean is Geoff can you explain this a little more for me please as it goes against conventional wisdom- "no replacement for displacement" and all that...
"I'd stay 3.6l for durability, and a properly built 3.6l piston will produce more power and torque than the RS 3.8 piston"
EDIT: What I mean is Geoff can you explain this a little more for me please as it goes against conventional wisdom- "no replacement for displacement" and all that...
"I'd stay 3.6l for durability, and a properly built 3.6l piston will produce more power and torque than the RS 3.8 piston"
9M and Racetek both have pistons in 3.6l that are lightweight, have a small ring package, and a digitally designed intruder to match either the stock cylinder head, or the 9M cylinder head. These pistons outperform the factory 102mm RS and RSR pistons by a wide margin.
In all of the sport engines I've done using MoTeC as the engine management system, the RS piston / RS camshaft produced the LEAST amount of Torque and HP at about 283rwhp on a Dynapack dyno. That same engine with the RS camshaft replaced by a Sport 2 camshaft produced 293rwhp. That same engine, rebuilt with 100mm Racetek pistons and Sport 2 camshafts made 306rwhp which has been in line with all the other engines of that type at between 301-308rwhp depending on intake, exhaust and fuel type (93 vs 91 octane) used. That same engine with open headers produced 320rwhphp, and the same engine with a varioram intake produced 308rwhp, but with significantly more midrange torque.
For comparison, all of the 964 Cup engines we were doing produced between 265-273rwhp depending on number of hours, blueprinted or not, and were all run with cat, primary, and secondary bypasses in place.
I hope this helps.
Last edited by Geoffrey; 04-27-2012 at 12:11 PM.
04-27-2012, 01:53 PM
#33
Drifting
Thread Starter
Thank you.
First and foremost, I would like to thank Rennlisters.
It has been difficult to decide what to do next - having your hand forced is never agreeable. If I hadn't discovered Rennlist my enjoyment factor regarding the car would be savagely less. I have learnt so much about my car and discovered truly great people. The relentless/ generous time and knowledge people give each other here is truly awe inspiring. I believe without a moments doubt that it is a testament to the soul that Porsche cars instil within us. I think we have all contributed in small and big ways to how great our cars are. If it wasn't for the kind support/ motivational feedback I have received here I wonder how long I would have kept the 964 for - I'd probably be a Saab owner ( I love Saabs too ).
To say I appreciate the aforementioned is a colossal understatement - thank you.
Back on topic. So what I'm still deducing re ITBs and above 7,000rpm:
• 993 valves are better performing.
• Cylinder heads – light porting, detail seatwork or 9M billet heads.
• 102mm pistons are less reliable but perform better.
• 100mm cylinders are thicker for reliability.
• Final compression.
• Thicker cylinders with a 109mm case spigot require machining of case.
• Camshaft – 9M, Sport 2.
How about RSR cams or are these the same as RS cams?
Thank you once again for your detailed answer Colin
Haha when I had a '57 Oval window that was an option many took as I'm sure you know being a past beetle man.
...and then talk to your chosen engine builder and, like Kai has done, make a decision not just about your engine, but also how and what you use the car for......
...The Hornet is definitely more of a track car than a road car nowadays.....and I always swore it wouldn't end up that way!
Absolutely - the use of the engine dictates all else.
So my vote would be to keep to a 3.6 and work out a plan to give you a 300 bhp engine e.g. a standard rebuild locally and then a trip to 9M for Colin to add some goodies like Motec, injectors and mods to the air intake system.
*I'll post a thread about this week's fun day out at Oulton when I get a chance.
Thanks for the feedback Steve - it's all helping weigh up the decisions. Do tell us about Oulton!
Thank you once again for your kind input - am extremely appreciative of all technical advice supplied.
It has been difficult to decide what to do next - having your hand forced is never agreeable. If I hadn't discovered Rennlist my enjoyment factor regarding the car would be savagely less. I have learnt so much about my car and discovered truly great people. The relentless/ generous time and knowledge people give each other here is truly awe inspiring. I believe without a moments doubt that it is a testament to the soul that Porsche cars instil within us. I think we have all contributed in small and big ways to how great our cars are. If it wasn't for the kind support/ motivational feedback I have received here I wonder how long I would have kept the 964 for - I'd probably be a Saab owner ( I love Saabs too ).
To say I appreciate the aforementioned is a colossal understatement - thank you.
Back on topic. So what I'm still deducing re ITBs and above 7,000rpm:
• 993 valves are better performing.
• Cylinder heads – light porting, detail seatwork or 9M billet heads.
• 102mm pistons are less reliable but perform better.
• 100mm cylinders are thicker for reliability.
• Final compression.
• Thicker cylinders with a 109mm case spigot require machining of case.
• Camshaft – 9M, Sport 2.
How about RSR cams or are these the same as RS cams?
These choices are all down to the tuner, it's where the synergistic approach comes into play. For instance, two different pistons may happily do the same job, but one could have a 12:1 compression and the other is 11:1, however if the 11:1 has a better squish design it may have a faster burn than the 12:1 which could make more torque. Lower static compression would also mean that the intake valve closing point would have to change to achieve the same dynamic compression ratio (based on piston stroke from IVC to TDC). But, a lower compression piston also leaves more space to cram in air/fuel mixture hence allowing a potentially higher VE (Volumetric Efficiency or cylinder filling).
In other words, it's a complicated, multi-variable equation and there is no "right" answer - so just go with the recommendation of your builder and use what combination they can guarantee will work.
In other words, it's a complicated, multi-variable equation and there is no "right" answer - so just go with the recommendation of your builder and use what combination they can guarantee will work.
...and then talk to your chosen engine builder and, like Kai has done, make a decision not just about your engine, but also how and what you use the car for......
...The Hornet is definitely more of a track car than a road car nowadays.....and I always swore it wouldn't end up that way!
So my vote would be to keep to a 3.6 and work out a plan to give you a 300 bhp engine e.g. a standard rebuild locally and then a trip to 9M for Colin to add some goodies like Motec, injectors and mods to the air intake system.
*I'll post a thread about this week's fun day out at Oulton when I get a chance.
All things equal, a 102mm piston will produce more torque and HP than a 100mm piston at about 200rpm lower peak value. My comments though were not based on all things being equal. The 993 RS (and RSR for that matter) piston is a heavy piston with thick piston rings and most importantly with an intruder profile (the part that sticks into the cylinder head) that is not optimum for profile of the cylinder head. This piston requires strong connecting rods when running higher RPM due to the weight, the piston rings tend to flutter due to their thickness at higher RPM which loses sealing, and because of the intruder profile, they are not very efficient at squishing the fuel / air mixture near the spark plugs for proper burn. In addition, for durability, you want the thicker cylinders that have a 109mm case spigot which requires machining of the case at additional cost. The 102mm cylinders are not as thick as the 100mm cylinders and they will tend to oval over time = less durability regardless of whether or not you use the 107mm or 109mm cylinders.
9M and Racetek both have pistons in 3.6l that are lightweight, have a small ring package, and a digitally designed intruder to match either the stock cylinder head, or the 9M cylinder head. These pistons outperform the factory 102mm RS and RSR pistons by a wide margin.
In all of the sport engines I've done using MoTeC as the engine management system, the RS piston / RS camshaft produced the LEAST amount of Torque and HP at about 283rwhp on a Dynapack dyno. That same engine with the RS camshaft replaced by a Sport 2 camshaft produced 293rwhp. That same engine, rebuilt with 100mm Racetek pistons and Sport 2 camshafts made 306rwhp which has been in line with all the other engines of that type at between 301-308rwhp depending on intake, exhaust and fuel type (93 vs 91 octane) used. That same engine with open headers produced 320rwhphp, and the same engine with a varioram intake produced 308rwhp, but with significantly more midrange torque.
For comparison, all of the 964 Cup engines we were doing produced between 265-273rwhp depending on number of hours, blueprinted or not, and were all run with cat, primary, and secondary bypasses in place.
I hope this helps.
9M and Racetek both have pistons in 3.6l that are lightweight, have a small ring package, and a digitally designed intruder to match either the stock cylinder head, or the 9M cylinder head. These pistons outperform the factory 102mm RS and RSR pistons by a wide margin.
In all of the sport engines I've done using MoTeC as the engine management system, the RS piston / RS camshaft produced the LEAST amount of Torque and HP at about 283rwhp on a Dynapack dyno. That same engine with the RS camshaft replaced by a Sport 2 camshaft produced 293rwhp. That same engine, rebuilt with 100mm Racetek pistons and Sport 2 camshafts made 306rwhp which has been in line with all the other engines of that type at between 301-308rwhp depending on intake, exhaust and fuel type (93 vs 91 octane) used. That same engine with open headers produced 320rwhphp, and the same engine with a varioram intake produced 308rwhp, but with significantly more midrange torque.
For comparison, all of the 964 Cup engines we were doing produced between 265-273rwhp depending on number of hours, blueprinted or not, and were all run with cat, primary, and secondary bypasses in place.
I hope this helps.
Last edited by Porsche964FP; 04-27-2012 at 03:36 PM.
04-27-2012, 03:54 PM
#34
Burning Brakes
You're still focusing on spec rather than what you want to do with the car....be certain of that first, then let the spec form from that....
...but at least you'll understand about what spec you need when you get there, which is more than me...I did it in reverse!
...but at least you'll understand about what spec you need when you get there, which is more than me...I did it in reverse!
04-27-2012, 10:58 PM
#35
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All things equal, a 102mm piston will produce more torque and HP than a 100mm piston at about 200rpm lower peak value. My comments though were not based on all things being equal. The 993 RS (and RSR for that matter) piston is a heavy piston with thick piston rings and most importantly with an intruder profile (the part that sticks into the cylinder head) that is not optimum for profile of the cylinder head. This piston requires strong connecting rods when running higher RPM due to the weight, the piston rings tend to flutter due to their thickness at higher RPM which loses sealing, and because of the intruder profile, they are not very efficient at squishing the fuel / air mixture near the spark plugs for proper burn. In addition, for durability, you want the thicker cylinders that have a 109mm case spigot which requires machining of the case at additional cost. The 102mm cylinders are not as thick as the 100mm cylinders and they will tend to oval over time = less durability regardless of whether or not you use the 107mm or 109mm cylinders.
9M and Racetek both have pistons in 3.6l that are lightweight, have a small ring package, and a digitally designed intruder to match either the stock cylinder head, or the 9M cylinder head. These pistons outperform the factory 102mm RS and RSR pistons by a wide margin.
In all of the sport engines I've done using MoTeC as the engine management system, the RS piston / RS camshaft produced the LEAST amount of Torque and HP at about 283rwhp on a Dynapack dyno. That same engine with the RS camshaft replaced by a Sport 2 camshaft produced 293rwhp. That same engine, rebuilt with 100mm Racetek pistons and Sport 2 camshafts made 306rwhp which has been in line with all the other engines of that type at between 301-308rwhp depending on intake, exhaust and fuel type (93 vs 91 octane) used. That same engine with open headers produced 320rwhphp, and the same engine with a varioram intake produced 308rwhp, but with significantly more midrange torque.
For comparison, all of the 964 Cup engines we were doing produced between 265-273rwhp depending on number of hours, blueprinted or not, and were all run with cat, primary, and secondary bypasses in place.
I hope this helps.
9M and Racetek both have pistons in 3.6l that are lightweight, have a small ring package, and a digitally designed intruder to match either the stock cylinder head, or the 9M cylinder head. These pistons outperform the factory 102mm RS and RSR pistons by a wide margin.
In all of the sport engines I've done using MoTeC as the engine management system, the RS piston / RS camshaft produced the LEAST amount of Torque and HP at about 283rwhp on a Dynapack dyno. That same engine with the RS camshaft replaced by a Sport 2 camshaft produced 293rwhp. That same engine, rebuilt with 100mm Racetek pistons and Sport 2 camshafts made 306rwhp which has been in line with all the other engines of that type at between 301-308rwhp depending on intake, exhaust and fuel type (93 vs 91 octane) used. That same engine with open headers produced 320rwhphp, and the same engine with a varioram intake produced 308rwhp, but with significantly more midrange torque.
For comparison, all of the 964 Cup engines we were doing produced between 265-273rwhp depending on number of hours, blueprinted or not, and were all run with cat, primary, and secondary bypasses in place.
I hope this helps.
04-28-2012, 06:24 AM
#36
Drifting
Colin,
How important do you place Knock control in the scheme of things, I know of one Rennlister who ran Motec and no knock, bought some bad fuel (allegedly) in Europe and ran into a rather large rebuild bill, circa 6k+ the after thought of showing knock control on the dash with a series of LED's seems primitive to my thinking, and bolting the stable door, is there provision at minimal cost? M800???
Kevin
How important do you place Knock control in the scheme of things, I know of one Rennlister who ran Motec and no knock, bought some bad fuel (allegedly) in Europe and ran into a rather large rebuild bill, circa 6k+ the after thought of showing knock control on the dash with a series of LED's seems primitive to my thinking, and bolting the stable door, is there provision at minimal cost? M800???
Kevin
04-28-2012, 07:10 AM
#37
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Frank -
I'm certainly not trying to talk you out of anything, but if you go 3.8, just make sure you are ready for the price tag - as someone said earlier, the engine itself will cost more (probably much more) than the car is worth. I certainly wouldn't do it from an investment standpoint - the incremental resale value over a 3.6 will be far exceeded by the additional cost of the rebuild.
I told you earlier by PM what my 3.8 roughly cost, and I can update you to say that the price has gone up even more since then as final bills come in. Like you, I spent a lot of time researching everything and getting quotes, and thought I had the price pretty well estimated when I went ahead with the rebuild, but I was still way off when the final bill came in - as you know it was mega. TBH, if I had known how much it was going to cost, I probably would have gone with a 3.6 with a choice few of the bits Colin described above. If you do go with the 3.8, it will be great, but just wanted to reinforce what others said before...
One last thing - you may want to drive a 3.8 just to see what the difference feels like before you pull the trigger. I'm going to try to make the meet next Sunday but am not sure - if I do we can find somewhere appropriate and I'm happy for you to have a go in mine.
B
I'm certainly not trying to talk you out of anything, but if you go 3.8, just make sure you are ready for the price tag - as someone said earlier, the engine itself will cost more (probably much more) than the car is worth. I certainly wouldn't do it from an investment standpoint - the incremental resale value over a 3.6 will be far exceeded by the additional cost of the rebuild.
I told you earlier by PM what my 3.8 roughly cost, and I can update you to say that the price has gone up even more since then as final bills come in. Like you, I spent a lot of time researching everything and getting quotes, and thought I had the price pretty well estimated when I went ahead with the rebuild, but I was still way off when the final bill came in - as you know it was mega. TBH, if I had known how much it was going to cost, I probably would have gone with a 3.6 with a choice few of the bits Colin described above. If you do go with the 3.8, it will be great, but just wanted to reinforce what others said before...
One last thing - you may want to drive a 3.8 just to see what the difference feels like before you pull the trigger. I'm going to try to make the meet next Sunday but am not sure - if I do we can find somewhere appropriate and I'm happy for you to have a go in mine.
B
04-28-2012, 07:38 AM
#38
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04-28-2012, 08:26 AM
#39
Burning Brakes
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Frank. Good luck with the engine project. Going to be great reading. Trying to think objectively.....sounds like the spend on the 3.8 and motec etc is an expensive way to get an extra 100BHP......maybe just get stock build which is bullet proof and spend the £15-20k you save on a supercharger later or another nice car. By time u are done you could have just had a 996GT2 and turn the wick up on the turbos (ok fair crack its not a 964 nor your black beauty but still). Just seems alot of mula to me.....
04-28-2012, 10:43 AM
#40
Drifting
Thread Starter
Colin,
How important do you place Knock control in the scheme of things, I know of one Rennlister who ran Motec and no knock, bought some bad fuel (allegedly) in Europe and ran into a rather large rebuild bill, circa 6k+ the after thought of showing knock control on the dash with a series of LED's seems primitive to my thinking, and bolting the stable door, is there provision at minimal cost? M800???
Kevin
How important do you place Knock control in the scheme of things, I know of one Rennlister who ran Motec and no knock, bought some bad fuel (allegedly) in Europe and ran into a rather large rebuild bill, circa 6k+ the after thought of showing knock control on the dash with a series of LED's seems primitive to my thinking, and bolting the stable door, is there provision at minimal cost? M800???
Kevin
Like you, I spent a lot of time researching everything and getting quotes, and thought I had the price pretty well estimated when I went ahead with the rebuild, but I was still way off when the final bill came in - as you know it was mega. TBH, if I had known how much it was going to cost, I probably would have gone with a 3.6 with a choice few of the bits Colin described above. If you do go with the 3.8, it will be great, but just wanted to reinforce what others said before...
B
B
Frank. Good luck with the engine project. Going to be great reading. Trying to think objectively.....sounds like the spend on the 3.8 and motec etc is an expensive way to get an extra 100BHP......maybe just get stock build which is bullet proof and spend the £15-20k you save on a supercharger later or another nice car. By time u are done you could have just had a 996GT2 and turn the wick up on the turbos (ok fair crack its not a 964 nor your black beauty but still). Just seems alot of mula to me.....
Thanks for the rationales Gents - it's all helping the long thought process on this one.
04-28-2012, 04:28 PM
#41
Why mess around with 3.8 if the p&c's are in good shape then re-use & if you feel the need for extra displacement / torque be a bit different, go all the way and do a tweaked 4.0 !!!
04-28-2012, 05:16 PM
#42
Three Wheelin'
Here's what I'd do: a 3.6 rebuild, pretty much factory other than some nice cams and upgraded valve train to the specification advised by whoever does the rebuild.
Stick with the factory Motronic for now and get a map from Wayne whatsisname.
Save up a year or two for a Motec / MBE / or something like a Link G4 (which comes with knock control).
BTW I think you've got the wrong end of the stick here:
Basically as I understand Geoffery's post, the standard 102mm (3.8) piston is just not a great design and a well engineered 100mm (3.6) piston will outperform it and be cheaper, regardless of the increased displacement, and also result in a longer lived engine.
Have you got a feel for the length of waiting list the engine builders are running? Would be great if you were running again at Donny
Stick with the factory Motronic for now and get a map from Wayne whatsisname.
Save up a year or two for a Motec / MBE / or something like a Link G4 (which comes with knock control).
BTW I think you've got the wrong end of the stick here:
Basically as I understand Geoffery's post, the standard 102mm (3.8) piston is just not a great design and a well engineered 100mm (3.6) piston will outperform it and be cheaper, regardless of the increased displacement, and also result in a longer lived engine.
Have you got a feel for the length of waiting list the engine builders are running? Would be great if you were running again at Donny
04-28-2012, 05:33 PM
#43
RL Technical Advisor
FWIW,....Motec M600 CAN be installed with knock control since we have done just that. I cannot tell you if M84 will do this as we have not tried it with that EMS yet since the majority of the cars we do are for the track.
We used a J&S knock controller, integrating that into the M600 and it worked very nicely.
We used a J&S knock controller, integrating that into the M600 and it worked very nicely.
04-28-2012, 05:37 PM
#44
If I were looking at dropping several bills on my 964's mill I would have a very VERY hard time not doing exactly that which was done to Kai's 'Claudia' recently. I would rather stick with a built 3.6 with bitch'n cams, trick intake and ITBs, and Motec - the performance of that mill speaks for itself.
Good luck with your decision, it'll be excellent whatever you do!
Good luck with your decision, it'll be excellent whatever you do!
04-28-2012, 05:41 PM
#45
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Colin,
How important do you place Knock control in the scheme of things, I know of one Rennlister who ran Motec and no knock, bought some bad fuel (allegedly) in Europe and ran into a rather large rebuild bill, circa 6k+ the after thought of showing knock control on the dash with a series of LED's seems primitive to my thinking, and bolting the stable door, is there provision at minimal cost? M800???
Kevin
How important do you place Knock control in the scheme of things, I know of one Rennlister who ran Motec and no knock, bought some bad fuel (allegedly) in Europe and ran into a rather large rebuild bill, circa 6k+ the after thought of showing knock control on the dash with a series of LED's seems primitive to my thinking, and bolting the stable door, is there provision at minimal cost? M800???
Kevin
You are correct though, Rennlister Christer had a 3.8 piston destroyed by detonation, but as far as I know this was the result of leaving his car under the supervision of a garage who mistakenly filled it with 95 ron fuel (despite the warning to use 98 on the underside of the fuel filler cap) and promptly "tested" the car to its demise.
The problem with standard knock control on a modified engine is that the whole noise signature of the engine will change due to cams, pistons or whatever, hence (for instance) causing piston-slap to be mis-diagnosed as knock. The knock indicator that Chrster employed was a precaution that he requested, I have to say that it seemed to work better than expected but only for audible knock. Motec do make an add-on knock control system for the M800 series but as yet I have not seen it in use. Some high end aftermarket ecu's have in-built knock control, but from what I understand the set up of these can be more difficult than mapping the fuel and ignition tables and they are still not infalible.