Duke48

I will be ordering MAF kit and a chip, the chip has raised rev limiter to 6950, but I can order it with stock rev limiter. Here is the question is stock rev limiter very conservative and engine is designed to run fine with higher rpms or this is actually pushing its limits. I'm leaning over asking for stock rev limited, but wanted to know your opinion.

V2Rocket

once in a while - probably fine
but the 944 oiling system is flawed in design and higher RPM like that gets into the danger zone

the car doesn't make any more power at higher RPM though, unless you've changed cams, so all you'd be doing is going a little faster in each gear before shifting.

harveyf

I agree with Spencer. Personally, taking any engine up to a rev that engages the rev limiter is a practice that I avoid on general principles. My ear/brain is pretty much tuned to avoid getting into that territory. That is another way of asking just because the rev limit is raised, is it of any value to you? And as Spencer indicated, without commensurate improvements to the engine, you are not making good power at a higher rev limit.
As always, Google can be our friend. Here is a link to an ariticle, that although aimed at newer Porsches, gives you some insight into the risks of overrevs.

https://911virgin.com/engine-revs/

951Dreams

I honestly don't know what is different on the lower end from an 8V, 951, or S2. If they are different at all. I have my rev limiter raised to 7K on my 951, but I don't use it all. Ever. However, I rev about 200-300 RPM higher than where my old rev limiter was set sometimes. In 1st and 2nd I would bounce off the rev limiter from time to time if I wasn't watching closely. The 951 is geared differently, and I always felt I had to shift juuuusssttttttt before what felt right. ~6700 seems to be the sweet spot for me. But I'm in that ~200 extra RPM's for fractions of a second. I never go near that high in 3rd or higher. I can feel the power fall off above 2nd once I pass ~5500. Grain of salt, my tach seems to be a bit off. I hit the limiter (before) when my gauge read about 6200 (or maybe it was climbing faster than the gauge can keep up with?) I now shift (when really getting on it) when it reads about 6500.

My personal opinion is, if you use any of that extra margin, you must be extra vigilant with your oil. And keep it slightly overfilled. Does it help? Likely not. Does it make me feel better? It does. Opinions will vary, but my PERSONAL rule of thumb is to always change the rod bearings NO LATER THAN 140K on any 944. Period. Full stop. That's as long as I'd ever let one go before replacing them. 90-100K would be the really safe bet. Some might advocate every 50k. Every 100k is what I shoot for. My 951 is hitting 94K, I have it in my plans to replace them before the end of the year. That won't mean you can't still spin the #2 bearing, but letting them wear and having the extra clearance from worn bearings, IMHO, increases your chances of starving #2. And that will always end badly. You really need to do all you can to keep those bearings in the Goldilocks zone. I've heard some of the racers say they replace them AT LEAST once every season. Some do it more often than that! I'm talking street cars.

But it's just like with timing belts, you'll get all sorts of opinions. 30K/3Y, 30K/5Y, 45K/3-5Y. I'm at about 15k/6Y ATM, and I'm doing the belts in March or early April. Nothing gets more expensive than losing the belt or spinning a rod. If you want to own a 944, and keep driving it, you just have to deal with a little extra PM. Both systems are flawed on these cars. Can you go 300K on original bearings? Sure, it happens. Can you go 80K/15Y on a timing belt? People have. But that's really playing the lottery. Every start is rolling the dice, with decreasing odds, not in your favor.

The reason I bring up bearings is, once again just my OPINION, that's the greatest risk from higher revving on these cars. It's not the only one, but I honestly feel the 944 can handle it, with the bearings (because oiling) being the weakest link. Just because I do have a higher rev limit now, and I do sometimes use it (if not often) I'll adjust my PM bearing replacement schedule accordingly. I'm a 30K/5Y guy on belts. I'll adjust my bearing schedule to likely something around every ~75K. Not that I expect to ever hit 175K. I've owned the car 6 years and put 8K miles on it...

Keep in mind, just my .02 cents. And every 944 guy will have a different .02 cents to add.

GPA951s

944 turbo and S2 do have a different bottom end. Depending on what year of turbo the pan is different, the oil pick up is different from an early car.. and most important is the windows under the mains. Porsche changed the design because if oil frothing.. the turbo engines don't have much in the way of transferring the air behind the pistons to get to the adjacent one.. the air literally has to go through the oil via a “ bubble” .. just like blowing bubbles in your milk when you were a kid.. the S2 has ports that allow the air to move to the adjacent cyl via voids they machined under the mains.. when i build a turbo engine i machine out under cyl 1-2 and -3-4 to give the air somewhere to go… haven't lost a bearing yet.

walfreyydo

Id be more worried about the stress added to the whole cam chain and tensioner system. If you havent changed out the pads and inspected the chain then I would do that before messing with the rev limit.

Duke48

Guys, thank for the opinions. What is the stock rev limiter on S2? I am about to order the chip and want to verify if the prodicer/seller will set it correctly.

walfreyydo

~6300 rpm based on the tach

Dan Martinic

Porsche actually recommends the opposite... and so do I, sorry. Can't see how this is ever a good idea

Jfrahm

Doesn't the S2 and early 968 use the 1R rods? Those were related to mysterious engine failures in the 928GTS. I would not want to rev super high on those. I think they generally were OK in stock S2s but worrisome in the 968, there is a TSB to bin them if ever unbolted in a 968. I have them in my 968 and did replace the rod bearings but did not swap out these rods, but I try to keep it under 6200 RPM.

951Dreams

That came from me reading the racers talk in threads about the oil pickup problems. And how these cars can become oil starved in high G corners from the oil running to the outside walls of the pan, leaving none under the pickup. Hence a little extra can help, or so the theory I remember went. When I do the rods I was thinking of getting the baffles that help prevent that and maybe the modified oil pickup. I don't race or even autox anymore, but the bearings stress me out on these cars. I know others personally that have spun #2. My 87 got sold so they could use the engine out of it while they rebuilt the one with the spun bearing.

As for over filling, it's only an issue if your crank gets into the oil, as that froths it like a Capaccino. And frothed oil does not work at all well as oil. Or so I've always believed and been told. Are there other considerations? I've always checked to make sure I'm not getting frothing when I fill/top off the oil. I'm not talking a few quarts or anything. I mean just a tad over the fill line. Error on the side of more over less.

ealoken

Over filling the 944 wil make the crank whip the oil.
Not! recomended.

Qtrfoil

"Does it help? Likely not. Does it make me feel better? It does."

Some day I'd like to see a thread here on "Things I obsess about that probably don't make any difference." The thread will go right next to "Things I can smell while driving my car that dogs cannot," and "Things I can hear while driving my car that bats wouldn't notice."

Tom Pultz

Which MAF kit?