The post about Casper's demise has me a little freaked out.
03-12-2014, 09:08 PM
#46
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doc,
you are probably right in that the red line on your tach is an economical red line decided on by the factory for warranty purposes. there is probably another 12% of rev before things could get expensive if you were to over rev briefly..valves floating most likely. Then dollars.
In the olden days the most important factor was considered to be piston speed which most engine designers kept well under 5000 feet per minute even when the highest quality materials were used. Today even NASCAR American V8s run higher piston speeds. As time went by more effective ways of strengthening the crankshafts, crankcases, and other components have been developed.
I worry about the 928 crank at high speeds personally. You would think it could get wavy in there under sustained high rpms. But what do i know.
To go higher with your redline you would need to do some of the following..
shorten the stroke
stronger crank and rods and pistons
stronger crankcase
more controlled valvetrain
better cylinder head breathing: this is something that many do not take
serious enough imo. Good venting = less blowby and higher HP as you know.
I will design a passive system for my RS when i replace my cast iron logs
and remove the Y pipe.
The answer to the question of red line is best found on the dyno. As stated here before i am sure, there is no point going much past the rpm of peak horsepower. In general driving your shift point should place you around the rpm of peak torque as your starting point for the next gear. If you find that your 928 is making peak horsepower at 4900rpm then you can start shifting at 5200 and have better performance than if you shift at 6000rpm anyway.
doc, this is the type of tach graphic i mentioned..this is a 356 tach. the 356 can whirl past 5500 and be fine as our 928s probably can do the same. 356s only have 3 mains and they can rev to 7500 and be fine. i just personally would rather drive than pull my motor out of the car.
I always enjoy reading your posts doc very much!-Matt
you are probably right in that the red line on your tach is an economical red line decided on by the factory for warranty purposes. there is probably another 12% of rev before things could get expensive if you were to over rev briefly..valves floating most likely. Then dollars.
In the olden days the most important factor was considered to be piston speed which most engine designers kept well under 5000 feet per minute even when the highest quality materials were used. Today even NASCAR American V8s run higher piston speeds. As time went by more effective ways of strengthening the crankshafts, crankcases, and other components have been developed.
I worry about the 928 crank at high speeds personally. You would think it could get wavy in there under sustained high rpms. But what do i know.
To go higher with your redline you would need to do some of the following..
shorten the stroke
stronger crank and rods and pistons
stronger crankcase
more controlled valvetrain
better cylinder head breathing: this is something that many do not take
serious enough imo. Good venting = less blowby and higher HP as you know.
I will design a passive system for my RS when i replace my cast iron logs
and remove the Y pipe.
The answer to the question of red line is best found on the dyno. As stated here before i am sure, there is no point going much past the rpm of peak horsepower. In general driving your shift point should place you around the rpm of peak torque as your starting point for the next gear. If you find that your 928 is making peak horsepower at 4900rpm then you can start shifting at 5200 and have better performance than if you shift at 6000rpm anyway.
doc, this is the type of tach graphic i mentioned..this is a 356 tach. the 356 can whirl past 5500 and be fine as our 928s probably can do the same. 356s only have 3 mains and they can rev to 7500 and be fine. i just personally would rather drive than pull my motor out of the car.
I always enjoy reading your posts doc very much!-Matt
__________________
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
03-12-2014, 10:48 PM
#47
Drifting
No way 7500 rpm as a usable red line with stock components, absolutely no way.
Even with the best components they cannot sustain 7500 rpms, some special
motors with all the goodies can and have done more. But no way stock.
In good tune with better components i would say a usable 6000 rpm red line is realistic with the 356 and some try for 6500.
03-13-2014, 04:06 PM
#48
I "think" this is the plug I'm using. I need to find my notes on that but I'm 95% sure this Subaru drain plug is the same as ours:
http://www.wrxtra.com/catalog/produc...products_id=29
I have this sender mounted in it:
http://www.autometer.com/cat_accesso...il.aspx?vid=36
This works with any of the Autometer Full Sweep Electric Temperature gauges. I went with this setup since the plan is to have 4-5 of these senders around the engine with only 1 or two gauges with toggle switches. They will also be wired to a data acquisition box recording all of them.
http://www.wrxtra.com/catalog/produc...products_id=29
I have this sender mounted in it:
http://www.autometer.com/cat_accesso...il.aspx?vid=36
This works with any of the Autometer Full Sweep Electric Temperature gauges. I went with this setup since the plan is to have 4-5 of these senders around the engine with only 1 or two gauges with toggle switches. They will also be wired to a data acquisition box recording all of them.
So can someone tell me regarding an OB pan, and pan spacer; do I need to make any other alterations to my '85 auto? And do I need both, one or the other?
03-13-2014, 06:01 PM
#49
Drifting
Greg,
this is an outfit that builds amazing 4 cyl air cooled Porsche racing engines that will spin to 9000 rpm:
http://www.aircooledtechnology.com/
this is an outfit that builds amazing 4 cyl air cooled Porsche racing engines that will spin to 9000 rpm:
http://www.aircooledtechnology.com/
03-13-2014, 06:17 PM
#50
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Matt those are VW motors......have nothing to do with Porsche. 914s were sold as VWs everywhere but in the U S market... and the 912E was made to use up excess inventory 914 engines and pawned off on the US market ONLY !! .
Gregg was building his own VW motors in high school
Gregg was building his own VW motors in high school
03-13-2014, 07:20 PM
#51
Drifting
Matt those are VW motors......have nothing to do with Porsche. 914s were sold as VWs everywhere but in the U S market... and the 912E was made to use up excess inventory 914 engines and pawned off on the US market ONLY !! .
Gregg was building his own VW motors in high school
Gregg was building his own VW motors in high school
But is used extensively in 356 track cars and it's very much like the 356 motor Jim, as you know.
The same can be done with a real Porsche 356 motor with the same
attention to detail.
I wanted people to see how they dynamically balance these motors
for higher rev capability. Anyone balanced their 928 motor?
Like Greg and many other Euro car enthusiasts, my Brothers and I probably had over 25 air cooled VWs and learned about motors on them. They are so easy to rebuild. Frank and i could neatly weld in new floor pans and bolt the body back on in 3 days comfortably. Our first beetle was black and we glued black gorilla fur in for a head liner..tasteful.
Frank my older brother had a 1956 convertible beetle he found in a barn, and i had a split window with retractable semaphores.
I had a really fast '64 convertible Karmann Ghia in beautiful sea blue (also a Porsche color) with a white top that could easily do 110 mph.
I bet you had a few VWs as well Jim!
Last edited by The Fixer; 03-13-2014 at 11:51 PM.
03-14-2014, 02:52 AM
#52
Racer
Thread Starter
don't let my issues jdiscourage you.....on street tires things are MUCH different...for example my old lemons racer.....using only an OB sump and 3/8th spacer with crankcase vented to atmosphere through a K&N it ran for about 125 hours on track why I owned plus another 50 for current owner....under race conditions, BUT shifted at most 6000rpm (I usually told the guys 5500 for the whole 1st day) and was on STREET TIRES.....maybe 1.2g.....not the spikes of 1.9g and constant 1.5g plus our racers see on slicks...
At a minimum for your S4 given your goals....OB pan and 3/8th spacer and carefully watch the temp of the oil...only run quality RACE oil.... a real outboard oil cooler and accusump is ideal....
This is what will be on Casper V2.0 in the next couple weeks....
At a minimum for your S4 given your goals....OB pan and 3/8th spacer and carefully watch the temp of the oil...only run quality RACE oil.... a real outboard oil cooler and accusump is ideal....
This is what will be on Casper V2.0 in the next couple weeks....
The GT has an oil cooler in the radiator end tank. My cooler developed a leak and needs replacement. The cooler is not available separately. Hans was going supply me a good oil cooler from one of his leaking radiators, but now I'm thinking an external oil cooler would be the way to go rather than replace the original. Adding an oil temp gauge would be part of an oil cooler upgrade plan.
I'll also plan on adding a spacer and OB pan. Is a smaller starter motor the only other modification required to run these? Does the belly pan still fit with the spacer installed? Ballpark cost for these parts?
I'll have to do some research on the breather system to come up with a plan to modify that.
With all that done I'll see what oil pressure is like on the track and determine if an accusump is needed. Sound like a solid plan? Replacing my engine is NOT something I want to deal with. I just finished that job in my Audi and I don't have the bank account left to even think about replacing a 928 GT engine.
03-14-2014, 03:21 PM
#53
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Greg,
this is an outfit that builds amazing 4 cyl air cooled Porsche racing engines that will spin to 9000 rpm:
http://www.aircooledtechnology.com/
this is an outfit that builds amazing 4 cyl air cooled Porsche racing engines that will spin to 9000 rpm:
http://www.aircooledtechnology.com/
The original subject is what should someone do with their stock 928 engine, to survive track days.
And it was mentioned that a 356 engine could spin to 7500 rpms.
My point was that was true, but not with stock pieces.
I was simply making an "apples with apples" clarification.
03-16-2014, 11:23 PM
#54
Rennlist Member
No freak out here... Back from another DE weekend, running on R888s, oil pan spacer, early pick up, new radiator, mostly water for coolant, BG 20w-50 oil, and shifting below 6k = trouble free car for the entire weekend. Roughly 3 hours of track time, spread over two days. Burned just a touch of oil this time. Will update the Kraken thread tomorrow with video. Flatout. (It's all one word now).
03-16-2014, 11:36 PM
#55
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No freak out here... Back from another DE weekend, running on R888s, oil pan spacer, early pick up, new radiator, mostly water for coolant, BG 20w-50 oil, and shifting below 6k = trouble free car for the entire weekend. Roughly 3 hours of track time, spread over two days. Burned just a touch of oil this time. Will update the Kraken thread tomorrow with video. Flatout. (It's all one word now).
You are on the edge!
Keep an eye on your gauges you're a stiff sway bar and a stiff set of springs/ shocks away from your first blown engine.
I wish you continued success, enjoy it, but be vigilant. Keep an eye or both if possible on that oil pressure gauge.
03-16-2014, 11:43 PM
#56
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Congratulations!
You are on the edge!
Keep an eye on your gauges you're a stiff sway bar and a stiff set of springs/ shocks away from your first blown engine.
I wish you continued success, enjoy it, but be vigilant. Keep an eye or both if possible on that oil pressure gauge.
You are on the edge!
Keep an eye on your gauges you're a stiff sway bar and a stiff set of springs/ shocks away from your first blown engine.
I wish you continued success, enjoy it, but be vigilant. Keep an eye or both if possible on that oil pressure gauge.
It's a lot easier to pull the pan and roll in a set of rod bearings than fix an engine with a rod trashing the entire bottom end.
03-16-2014, 11:49 PM
#58
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This is good advice. It saved me an engine when I first made the move to R888's in my street car.
03-17-2014, 07:10 AM
#59
Rennlist Member
Lol re sway bar... I've got Carl's big one up front, and the Devek half cage acts as one for the rear. Ticking time bomb aparently.
I will definitely check out the filter here shortly. And I do glance down at the oil pressure gauge during the run from time to time. I also have my GoPro inside the cockpit so I should be able to see the gauge. I plan to add bigger gauges to the A pillar shortly. I have room for 3. I'm thinking oil pressure, oil temp, and engine temp. Ideas?
I'd also like to add an external oil cooler. What are you guys using?
I will definitely check out the filter here shortly. And I do glance down at the oil pressure gauge during the run from time to time. I also have my GoPro inside the cockpit so I should be able to see the gauge. I plan to add bigger gauges to the A pillar shortly. I have room for 3. I'm thinking oil pressure, oil temp, and engine temp. Ideas?
I'd also like to add an external oil cooler. What are you guys using?
Last edited by Courtshark; 03-17-2014 at 07:34 AM.
03-17-2014, 10:29 AM
#60
Drifting
No freak out here... Back from another DE weekend, running on R888s, oil pan spacer, early pick up, new radiator, mostly water for coolant, BG 20w-50 oil, and shifting below 6k = trouble free car for the entire weekend. Roughly 3 hours of track time, spread over two days. Burned just a touch of oil this time. Will update the Kraken thread tomorrow with video. Flatout. (It's all one word now).
regarding your oil consumption, have you made efforts to improved crankcase
ventilation with your track car? I noticed an easy passive way with my '83 yesterday and it's breathing much better.