Rob Edwards

Stock motor + Slicks = Anderson kills the motor in the 1st session

Stock motor + R888's = Edwards kills the motor in the 2nd session.

mark kibort

unknown motor gets unknown reason for failure.

Anderson has driven my car and didn't break it for a session.
remember, you have seen the videos......6 racing seasons! 1000s of laps, and 1000s more on the holbert machine. pro races, SCCA, PCA, TCCRA, Time Attack, etc etc. Never a problem! get a known engine that has no issues to start and you will be FINE!!

mark kibort

I run a dipstick oil temp sensor from VDO. it seals fine, no leaks , which would be an issue if there was too much crankcase pressure, which there is not. oil temps get to about 250F on a very hot day at the races . no worries as Amsoil doesn't seem to break down as much as other oils in extreme conditions.

mark kibort

listen to this motor puuurrrrrrr!! no regard to rpm limits. push push push. no issues.

123quattro

I think a lot of it depends on the track as well. If there aren't any long high speed corners you'll be a lot better off.

The one car that really amazes me is the Viper. We beat on our development cars constantly. Never once have we had an engine failure and they get a ton of track use with R compound tires. We've broke diffs and transmissions, but never an engine.

danglerb

I think I agree with Kibort, lot of 928 engines have unknown history, and likely have half a dozen "minor" problems, put them on the track under high stress and minor problems may add up to major failure.

docmirror

Of course just one data point for me. I expected the engine to live up(or down) to it's hype. There's a red line on the tach for a reason, and I used the car at the track as if it were a competitive event(it was). So - yes, I went over 6000RPM, just like the designers intended. If they had not built effective oiling to 6600RPM, then they red line should have been 6000, or 5800 or 5400.

To me, it's like the old 'pop goes the weasel' deal. You don't know when or how, but eventually the weasel is going to pop out and surprise you. The faster you turn the crank, the faster the weasel will pop out. But make no mistake -- the weasel will always, always pop out eventually, then race day is done, and it's time for the checkbook.

lol...

linderpat

that was freakin freaky

The Fixer

This was so good i thought why not re-post it and ask..

Hacker,
Is there any chance you could take a photo of your buddy's perfected Euro crankcase breather set up and post this?
Or even a sketch from memory.

Reading docmirrors post above ^ made me think how many tachs way back when (including Porsche)
had a graduated graphic which was a warning that you were approaching redline. That is how i see rev limit,
stay away from it.
Many very good mechanics i know never red line their Porsches.
They really think about how much is going on in there as i do.
I am sure Greg Brown's 'gears' are turning in his head when at high revs.

Not even Porsche can ensure each (production) motor has the exact same quality and/or tolerance for track abuse.
It's probably better than most and very close though.
I.e; couldn't there be some forged cranks which are not as good as others?, imperfect castings, oil pumps could vary a bit , and so on.

Norman singer discussing the 917 motor, telling his Drivers how to use it;

Singer pointed out it red lined at 8400 rpms (IIRC) and at 8500 it blew up.

If i were ThetaTau87, i wouldn't beat on that beautiful '87 S4.
The 1.6L Ford i-4 motor has just about anything available you want to make it go and stay together.
They can make big power for their size. Everything is available for these little Ford motors,
dry sump it and beat the snot out of it.
I'd like to buy a Lotus (Caterham 7) with a little Ford motor and have a blast abusing it.
While my beautiful 928 remains beautiful in the garage.


-Matt

docmirror

Well, a red line is what appears on my 928, and my 968, and I had one on my 914, and one on my 944, and on my other 914. If there was a Porsche with a yellow band, or line I never saw it, not that it doesn't exist. Also, I've heard that the GT engines(which I have) are specially selected and hand tuned carefully to be the best of the production line. Not sure if it's true, but makes sense.

Aircraft sometimes have a yellow band on them, or other restriction such as; "2650RPM for 5 min, 2400RPM continuous rating". If Porsche wanted a section to avoid continuous operation, they could have put it in. Same with the red line on the oil temp, water temp, and oil pressure. We've heard reliably that the oil pressure sense job is substandard, and I think the oil temp and sump appear to have some failings. But the red line is the red line and unless or until Porsche deviates, the engine should operate within stated parameters up to that point until it is electronically limited. As I said, if they wanted a 6k red line, then put it there. If they wanted a 5800, or 5600 then put it there, or put a yellow arc. Absent those factors from the mfg, I presume they did their due diligence. I run my Ferrari up to the 6800RPM redline sometimes, and don't worry about it.

MGW-Fla

These threads just seem to depress me the more I read of them, yet I cannot get enough of them. Have read them all I think, but the more I read, the more things I wonder about.

I have DE'd my US auto '85 32v just 2-3 times a year the past two years. Hope to do the same this year, starting in a month. The track I've gone to so far is Roebling Road, just west of Savannah, Ga., 2.1 miles of basic road course. I am no demon on the track. Compared to most everything else on the track, my 928 is fat, old, 'n slow,.......like its owner! Top speed for my shark down the front straight at Roebling is under 120. I am like Courtshark in that I am trying to learn & enjoy my shark, not promote up the ladder with intent to race, instruct, etc. I am happy to be in Blue Solo & don't care if I ever even make it to White. I don't want to hear about switching to a Vette or anything else. I love my shark & I want to continue to track my shark. But I also don't want to take it home on a trailer, ever! Neither my bank account nor my marriage would sit well with engine failure, much less my state of mind.

I'm assuming that most discussions regarding red lining your 928 would more likely apply to a 5 speed on the track as my auto rarely gets near red line. I keep it mostly in 3rd, & I believe only at one spot on the track does it ever shift at red line. I switched from Mobil 1 15/50 to Royal Purple 20/50 last year. I've done Porken's chip with the hotter plugs, X-pipe, koni's & hypercoils(400/600), nothing too special so far. This thread had me calculating my "DE hours", which is just under 13.5. My car has never run hot & never shown any signs of any problem. I have been running street tires, was thinking of switching to the R888s, would that be advised not to do?

I know I need to add some mods to ensure that I don't kill my engine. OB pan, old style pick up tube, & a spacer? Would an OB pan & old style pick up tube require any other mods to my '85, like an S4 would? Eric, can you give more info on type of temp gauges you use/recommend, & a bit more specifics on the install? What is a "gotta do" in the next few weeks prior to my DE the 1st weekend in April? What is a "would be best to have" list for my '85 auto?

The Fixer

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

docmirror

One of the reasons for the GT higher rev limit is the changed cam profile. That's also why it idles higher due to overlap and aggressive ramps. I don't want a higher red line, I just want the engine to work at the red line the designers set up. Again, in aviation I can run the engine at 75% power for hours on end. One of the reasons is that the engines are very conservatively rated. The GT is around 1HP/Cu In which in it's day was a high output engine. But, if you look at the cooling system, including the oil radiator you can clearly see that there is no way it will dissipate that kind of energy for very long. The GT is even more strained as it produces more HP but the radiators are the same as the non-GT.

There's a lot of things that one can do to the engine to improve longevity. I was under the impression that Porsche did all their testing before issuing the car. The small details that take a while to develop like the drive shaft migration are a teething issue. The oiling fault is pure design related and has nothing to do with time in service. Someone at Porsche should have discovered this oiling problem based on the history of the 944 track work long before the 928GT came along in 89.

Now - I'm starting to whine about it, so I'll stop here. But - along with the FMS issue on the Boxter engine makes me wonder about Porsche. Combine that with what I know about their disaster into the aviation engine biz, and there are some real engineering CFs involved.

123quattro

I don't think it's any secret that Porsche engines blow up. It just that Porsche owners think they have race cars and that's part of the deal so they put up with it. Boxsters and 996s are some of the worst, but pretty much everything except for 911 GTx cars are susceptible. This isn't new news.

hacker-pschorr

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.