Crank cross drilling, case oil mods, 3.8L, welding heads?
05-21-2006, 11:48 PM
#1
Crank cross drilling, case oil mods, 3.8L, welding heads?
Ok, am rebuilding the engine, may be reusing the stage2 turbos (w/ either 500 or 550hp programming), may go stage 3 if they sell.
Engine mods are for a 50% daily driver, 50% DE w/ Hoosiers.
Given the above, what are must haves and what are nice-to-haves for a 680NM vs 800NM engine.
1)Crank cross drilling
2)case mods-oil, maybe shuffle pin
gt3rsr oil pump-(whoops, already bought this one!)
3)carrillo rods vs arp bolts w/ stock rods
4)3.6 vs 3.8 p&c's
5)arp head studs
6)flame rings
7)head welding
8)aase springs/retainers
9)special vs stock valves
10)dual ignition
11)evo vs rs cams
12)different rockers
13)different injectors
An example of the reason for this post: While folks like Andial say cross drilling the crank isn't necessary, other tuners do-what's up with that?
I need to decide on all the above in the next couple days so any insight is appreciated.
Thanks for your time.
Engine mods are for a 50% daily driver, 50% DE w/ Hoosiers.
Given the above, what are must haves and what are nice-to-haves for a 680NM vs 800NM engine.
1)Crank cross drilling
2)case mods-oil, maybe shuffle pin
gt3rsr oil pump-(whoops, already bought this one!)
3)carrillo rods vs arp bolts w/ stock rods
4)3.6 vs 3.8 p&c's
5)arp head studs
6)flame rings
7)head welding
8)aase springs/retainers
9)special vs stock valves
10)dual ignition
11)evo vs rs cams
12)different rockers
13)different injectors
An example of the reason for this post: While folks like Andial say cross drilling the crank isn't necessary, other tuners do-what's up with that?
I need to decide on all the above in the next couple days so any insight is appreciated.
Thanks for your time.
05-22-2006, 09:22 AM
#2
Nordschleife Master
I would not cross drill the crankshaft in your engine. By cross drilling the crank, you are forcing oil from the main bearing into the center of the crankshaft to assist with the oiling of the #2 and #5 rods. With a low RPM engine <7000-7200, I have found it isn't necessary. Further, it is my opinion that it isn't required for higher reving engines and PMNA did not do this oiling modification, nor does Aase Engineering or some other successful names. When you cross drill the main bearing, you are also grooving the center bearing which means you lose some amount of bearing suface area and I'd rather have the surface area for crankshaft stability.
Case modifications are recommended. In the 964 Cup engines that I've done, there is clear evidence of the case walking from stress. Shuffelpinning the case cures this problem and is an inexpensive modification with all things considered. The windage modifications which consist of boattailing the case and eyebrowing the cylinders should help with airflow inside the case. I haven't done back-to-back tests with these modifications to know how much they improve performance. I have heard 10hp, but who knows. The mods are cheap.
Carrillo rods are much stronger than the stock rods, and I'd replace the stock ones with them. I've also found that the rod side clearance of the 993 rods is much tighter than in the past. I believe this may be a contributing factor to the increasing number of 993 N/A engines with bottom end problems when tracked. I have increased my rod side clearance to help with oil temperature control.
I very much dislike 3.8l engine size for turbo engines. They have less surface area and do not seal as well. Yes, shops with big names use them successfully. I just think the value, or return on the expense is just not worth it. If you do it, you'd want the bore in RSR cylinders which require case modifications. Don't use the slip in 3.8RS cylinders as they are weak on the case spigot size.
ARP head studs are good although I'm not so convinced that the 993 steel head studs aren't very, very good either.
Flame rings = good for higher boosted applications >1bar
Head welding gives the heads structure on the sides between the first two cooling fins. The 9M heads come with this section not machined so it adds considerable structure to the heads.
Technically, you need to design your cam, or pick an off-the-shelf camshaft and then combined with the valvetrain mass have it run through a camshaft/valve acceleration/force program to determine the correct seat and nose pressure for your application. If you don't want to do that, the Aase springs work for most situations and they can handle about .510" of lift before coil bind at the factory installed height. You'll find that many of the aftermarket springs out there are way too stiff for the application. This hurts performance and if too stiff will begin to wear cam lobes prematurely.
I'd use a good stainless steel aftermarket valve over the Porsche valve because they are lighter and have a better finish and improved shape that promotes flow.
Twin plug and associated ignition equipment is an improvement.
I personally like the GT2 Evo camshafts for street engines. That is the only off-the-shelf camshaft that I recommend any more for EFI 911 Turbo engines. Alternatively I have custom camshafts ground and they are less expensive than the factory GT2 Evo camshafts and are built off chill cast cores which are stronger than welding/regrinding and other forms of cam blanks.
If you go with a performance camshaft, you'll want to switch from the hydraulic rockers to mechanical rockers. There really isn't a good option here. Realistically, the Motorsport rockers are the ones to use but they are $200 Each. Alternatively, you can use the older rockers which should be fine, but their width varied and I have had difficulty installing them in 993 cam towers without machining. I'm working on the parts to convert 993 rockers from hydraulic to mechanical followers, the same as the Motorsport ones.
You'll definately need larger injectors. At the stock fuel pressure, the 44lb/hr injectors are good for about 480hp, 55lb/hr are good for about 560hp, an 72lb/hr are good for about 750hp.
You'll of course need programming or a different management system for this combination to work.
Case modifications are recommended. In the 964 Cup engines that I've done, there is clear evidence of the case walking from stress. Shuffelpinning the case cures this problem and is an inexpensive modification with all things considered. The windage modifications which consist of boattailing the case and eyebrowing the cylinders should help with airflow inside the case. I haven't done back-to-back tests with these modifications to know how much they improve performance. I have heard 10hp, but who knows. The mods are cheap.
Carrillo rods are much stronger than the stock rods, and I'd replace the stock ones with them. I've also found that the rod side clearance of the 993 rods is much tighter than in the past. I believe this may be a contributing factor to the increasing number of 993 N/A engines with bottom end problems when tracked. I have increased my rod side clearance to help with oil temperature control.
I very much dislike 3.8l engine size for turbo engines. They have less surface area and do not seal as well. Yes, shops with big names use them successfully. I just think the value, or return on the expense is just not worth it. If you do it, you'd want the bore in RSR cylinders which require case modifications. Don't use the slip in 3.8RS cylinders as they are weak on the case spigot size.
ARP head studs are good although I'm not so convinced that the 993 steel head studs aren't very, very good either.
Flame rings = good for higher boosted applications >1bar
Head welding gives the heads structure on the sides between the first two cooling fins. The 9M heads come with this section not machined so it adds considerable structure to the heads.
Technically, you need to design your cam, or pick an off-the-shelf camshaft and then combined with the valvetrain mass have it run through a camshaft/valve acceleration/force program to determine the correct seat and nose pressure for your application. If you don't want to do that, the Aase springs work for most situations and they can handle about .510" of lift before coil bind at the factory installed height. You'll find that many of the aftermarket springs out there are way too stiff for the application. This hurts performance and if too stiff will begin to wear cam lobes prematurely.
I'd use a good stainless steel aftermarket valve over the Porsche valve because they are lighter and have a better finish and improved shape that promotes flow.
Twin plug and associated ignition equipment is an improvement.
I personally like the GT2 Evo camshafts for street engines. That is the only off-the-shelf camshaft that I recommend any more for EFI 911 Turbo engines. Alternatively I have custom camshafts ground and they are less expensive than the factory GT2 Evo camshafts and are built off chill cast cores which are stronger than welding/regrinding and other forms of cam blanks.
If you go with a performance camshaft, you'll want to switch from the hydraulic rockers to mechanical rockers. There really isn't a good option here. Realistically, the Motorsport rockers are the ones to use but they are $200 Each. Alternatively, you can use the older rockers which should be fine, but their width varied and I have had difficulty installing them in 993 cam towers without machining. I'm working on the parts to convert 993 rockers from hydraulic to mechanical followers, the same as the Motorsport ones.
You'll definately need larger injectors. At the stock fuel pressure, the 44lb/hr injectors are good for about 480hp, 55lb/hr are good for about 560hp, an 72lb/hr are good for about 750hp.
You'll of course need programming or a different management system for this combination to work.
Last edited by Geoffrey; 05-22-2006 at 01:11 PM.
05-22-2006, 09:59 AM
#3
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Brad
You should trust your builder with these decisions, otherwise look for another one. Just be very specific with what you are trying to achieve and leave it in his hands, or else who is to blame when/if things go South?
You will get 100 different opinions from 100 different posters, if you are ready to take the advice of the posters, then you should build your engine with them. Geoffrey has offered a very in-depth opinion based onhis experience, if your builder has a different one, who would you believe?
Think about it
You should trust your builder with these decisions, otherwise look for another one. Just be very specific with what you are trying to achieve and leave it in his hands, or else who is to blame when/if things go South?
You will get 100 different opinions from 100 different posters, if you are ready to take the advice of the posters, then you should build your engine with them. Geoffrey has offered a very in-depth opinion based onhis experience, if your builder has a different one, who would you believe?
Think about it
05-22-2006, 12:13 PM
#4
RL Technical Advisor
Originally Posted by Jean
Brad
You should trust your builder with these decisions, otherwise look for another one. Just be very specific with what you are trying to achieve and leave it in his hands, or else who is to blame when/if things go South?
You will get 100 different opinions from 100 different posters, if you are ready to take the advice of the posters, then you should build your engine with them. Geoffrey has offered a very in-depth opinion based onhis experience, if your builder has a different one, who would you believe?
Think about it
You should trust your builder with these decisions, otherwise look for another one. Just be very specific with what you are trying to achieve and leave it in his hands, or else who is to blame when/if things go South?
You will get 100 different opinions from 100 different posters, if you are ready to take the advice of the posters, then you should build your engine with them. Geoffrey has offered a very in-depth opinion based onhis experience, if your builder has a different one, who would you believe?
Think about it
05-22-2006, 12:46 PM
#5
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I like what Geoffrey has said. Some people like the 102mm upgrade, some don't. The only thing that I disagree with is the X-drill subject. I think that Geoffrey will/would move toward drilling the crank if the engine redline was moved toward 7500, and when combined with Carrillo's. I think that you must also have to X-drill when you add the extra weight of the 102mm Mahle's. It's a situation where you are damned if you do and damned if you don't. What is the lesser of 2 evils when you look at the dollars spent in an uprated engine. For engines running greater than 1.2 bars I would not take the chance of using the stock 993 head studs.
In the end when you start to add up the monies that you have to spend in these engines. One has to move into a "risk reduction" type of thinking. Or moving the statistics more favorable if, situation. If you build your engine as a street use only with stock redline, and 1bars of boost. One can follow the factory parts schedule. However, if the car hits the track, you need to build "risk management" into the build.
In the end when you start to add up the monies that you have to spend in these engines. One has to move into a "risk reduction" type of thinking. Or moving the statistics more favorable if, situation. If you build your engine as a street use only with stock redline, and 1bars of boost. One can follow the factory parts schedule. However, if the car hits the track, you need to build "risk management" into the build.
05-22-2006, 02:18 PM
#6
Thank you for the detailed explanations-I've already learnt some new things.
When ya get 10 radiologists reading one MRI you get 10 different readings. Just looking for a consensus and being an educated consumer. Nothing wrong with that I think.
For instance when Toby harshed a tuner for promoting mechanical lifters-it was good to hear both sides of the argument and be able to make an informed decision. I can see Jean's point though as well.
When ya get 10 radiologists reading one MRI you get 10 different readings. Just looking for a consensus and being an educated consumer. Nothing wrong with that I think.
For instance when Toby harshed a tuner for promoting mechanical lifters-it was good to hear both sides of the argument and be able to make an informed decision. I can see Jean's point though as well.
05-22-2006, 03:11 PM
#7
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Eh my two cents, not that anyone cares... and Geoffrey you know I defer to you and admire your knowledge immensly! and know Kev knows his stuff too.... 3.8 slip-ins are a no-no for NA IMHO... but in a TT I think they provide a reasonable $ to preformance increase..as long as ringed... linear displacement usually equals linear power and not a changed power band all things being equal...
... and crank work... we'll I dont love the lower pressure.. and the decreased bearing patch.. but help me out here guys.. on Porsches.... I have seen quite a few bearings scored/spun on normal cranks.,.. but never on a modded crank... with HP up to the 900-1000 range... guess time will tell.... i probably have about as much torque low and as low a pressure as I have ever seen at 3500-4000 rpm.. hope I'm right...
.... but to Jean/Steve's point.... integrated packages (non 'hard' parts need to be carefully integrated.... and if not you will spend a ton(or your tuner) will spend a ton of time makeing sure they work together... but I personally would rather have a tried and true, frequently used config... or a lower power varient of aknown config.... e.g my rig and Jean's are virtually the same except for snails and MAF versus MAP and a hundred or two horsepower :-).... but I would be very comfortable converting to his rig since I know the bottom end is config'd for that... again to point above or 'margin'
JMHO
Although for flame propogation I hate to see one plug fire a bigger cylinder... so more dollars there.... I have had pretty gopod luck with MSD or Crane rigs on single plug but want the retarded timing afforded by twinplug...
... and crank work... we'll I dont love the lower pressure.. and the decreased bearing patch.. but help me out here guys.. on Porsches.... I have seen quite a few bearings scored/spun on normal cranks.,.. but never on a modded crank... with HP up to the 900-1000 range... guess time will tell.... i probably have about as much torque low and as low a pressure as I have ever seen at 3500-4000 rpm.. hope I'm right...
.... but to Jean/Steve's point.... integrated packages (non 'hard' parts need to be carefully integrated.... and if not you will spend a ton(or your tuner) will spend a ton of time makeing sure they work together... but I personally would rather have a tried and true, frequently used config... or a lower power varient of aknown config.... e.g my rig and Jean's are virtually the same except for snails and MAF versus MAP and a hundred or two horsepower :-).... but I would be very comfortable converting to his rig since I know the bottom end is config'd for that... again to point above or 'margin'
JMHO
Although for flame propogation I hate to see one plug fire a bigger cylinder... so more dollars there.... I have had pretty gopod luck with MSD or Crane rigs on single plug but want the retarded timing afforded by twinplug...
