wanting to make a 3lt turbo

[PSH]

I did a lot of reading regarding which rods to use...I found that the general opinion out there was that the originals are hard to beat. I'm not saying that they can't be bettered, just that I haven't come across any that have failed even when power output had been greatly increased. I am of course referring to the original forged rods, not the later cast rods which have been known to fail. My own experience would back this up, the car had run for a number of years with a 75% increase in power without issue, she now has around 100% increase in power and still no problems. I would say though that it's important to have the wrist pins and bearings renewed in any rebuild, these can fail especially on No.2 rod. I would also suggest fitting a crank scraper, this reduces a lot of unwanted rotational weight from the crank giving a much freer revving engine, I have found that it has improved the driving experience greatly...

Pete

 

[blade7]

An engine builder told me the oil that's flung off the crank lubricates the cylinder walls and helps cool the undersides of the pistons....

 

[PSH]

An engine builder told me the oil that's flung off the crank lubricates the cylinder walls and helps cool the undersides of the pistons....

With all due respect, I don't think your engine builder understands the principles of crank scraper/windage systems, they actually reduce both engine and oil pan temperatures as proved on a dyno. Engine power is increased especially mid/top range and the engine has a much freer revving feel to it. My own engine was transformed, now it's difficult to say what made the biggest difference as let's face it just about everything was upgraded but I'm sure that the way it responds to the throttle is in part due to the crank scraper, makes the engine feel like it has a much larger capacity. BTW Ishihara-Johnson have continued with their development on the 944 engines and now have a very impressive windage system, if my sump gasket ever fails in the future I'll most certainly look at installing this latest development.

You'd be surprised at how many OEM crank scraper/windage systems are out there in every day cars and this is nothing new, for example the RR Merlin engine as fitted to the famous spitfire employed such a device.

Here's a little more info from the Ishihara-Johnson website, there is more there for anyone interested...


Quote:

What are some of the benefits?· Less rotating mass for the engine to accelerate because of the removed oil
· Less loss of power because of excessive drag caused by oil droplets in the windage cloud
· Helps reduce engine damaging oil-foaming both on the surface and bubbles deeper within the oil
· Helps avoid oil starvation by keeping the oil in the pan during hard braking and turning as well as during off-road driving
· Helps to cool critical engine parts by quickly returning heated oil to the sump
· Helps to prevent the cylinder walls from being overloaded with oil
· Can help with fuel efficiency

During normal engine operation a significant amount of oil adheres to the rotating assembly or becomes entrained in a "windage" cloud surrounding it. It should be remembered that the particular characteristics of oil adhesion and/or oil-in-air entrainment vary depending on the engine rpm and what the vehicle is doing at the time. How the oil droplets are kept and drawn into the tornadic windage cloud is explained by the phenomenon known as the Tea Leaf Paradox, which was first described by Albert Einstein in 1926. It is counterintuitive that oil droplets would be kept and drawn into ("entrained") rather than completely expelled out of the windage cloud due to centrifugal force.
When a portion of the total droplets are small enough in physical size the predominate influence on their behavior switches. Rather than just their momentum due to being ejected from or impacted by the rotating assembly they are guided by the air currents in the windage cloud.* This droplet behavior in a gas atmosphere, which is a type of "fluid", in the confined volume of the crankcase is what the Tea Leaf Paradox addresses. The oil droplets have a greater density than the gas molecules.
Remember that an "equilibrium" of entrained oil is reached for the particular operating conditions. This means that not all the oil is held but rather that the amount rises until a certain point is reached and then the extra is not taken in or it swaps places with oil already in the cloud that is then released. Generally the higher the rpm, the more oil that is held because of the higher pressure differential. It is not unusual for a quart or more of oil to be suspended in the cloud at high rpms in many engines.

end quote:

regards

Pete

 

[blade7]

If you're happy with the IJ scraper Pete that's fine. 5 minutes on google throws up differing of opinions about their benefits, particularly on relatively low reving engines with effective sump baffles, like later 944's. If you had fitted the scraper in isolation and reported the same gains I'd be mightily impressed, but for now I'm of the opinion for road use the gains are relatively minor. For the record the guy I mentioned earlier is well respected and arguably understands more about 944 engines than most on internet forums...

 

[blade7]

 

[blade7]

Double post []

 

[PSH]

If you're happy with the IJ scraper Pete that's fine. 5 minutes on google throws up differing of opinions about their benefits, particularly on relatively low reving engines with effective sump baffles, like later 944's. If you had fitted the scraper in isolation and reported the same gains I'd be mightily impressed, but for now I'm of the opinion for road use the gains are relatively minor. For the record the guy I mentioned earlier is well respected and arguably understands more about 944 engines than most on internet forums...

ah yes...there will always be differing opinions, alas most by those who have never experienced the subject for themselves, I think in general the opinions are more 'for than against' and as has been proven the collection of oil around a crank starts to develop at very lows speeds and just gets worse the faster you go . I do recall reading of one particular engine, (think V8) that at high revs the entire contents of the oil pan is suspended around the crank...makes you think doesn't it.... but yes I'm happy with the car, she is running better than ever before and I have no doubt part of that is due to the scraper. I seem to have found a perfect mix, or in as far as to what type of engine feel that I prefer personally. I'm also very glad that I didn't go the fully lightened flywheel route, my flywheel is slightly thinner than Porsche state as minimum thickness, iirc about 0.1mm less, so it is in effect lightened but not so much as to effect the torque in a negative fashion.....all good fun...


Pete

 

[TTM]

Square dash cars with the early style oil pick up tube use an oil sump with a moulded-in scraper, for what it's worth.

 

[blade7]

[] The opinions I found were mostly related to race engines in the US, usually backed up by dyno results. None said scrapers didn't work, just the gains were variable. As for the V8 with all the oil suspended around the crank I wonder how the top end was being lubricated ? Porsche modified the 2.7/S2/968 blocks with windage ports and plastic blanking plates in the crankcase area, I'm inclined to think this may have had just as much effect.

 

[PSH]

[] As for the V8 with all the oil suspended around the crank I wonder how the top end was being lubricated ?

I do recall reading that this was one of the issues facing dragsters...from what I recall there's a fine balance between how high you can rev an engine before all of the oil is around the crank and thus starving the top end, dry sumps are a non-starter from what I read. other comments such as, 'with a crank scraper fitted you don't need to top the oil up to it's manufacturers level', can't say that I'd want to play around with this but it's nice to realise that I probably have a larger safety margin now with the scraper fitted. Windage ports aren't going to do the same job as a scraper, I can see merit in their objective though...too late for me, I don't plan on stripping down this engine anytime soon if ever. SWMBO has been making nasty noises lately about selling the old girl while prices are good and buy a sensible low maintenance car....pure sacrilege sir, pure sacrilege ...

Pete

 

[blade7]

SWMBO has been making nasty noises lately about selling the old girl while prices are good and buy a sensible low maintenance car....pure sacrilege sir, pure sacrilege ...

Pete

I'm coming round when you're out and offering her some new washing up gloves and £5k cash for it .

 

[PSH]

haha...since I do most of the washing up around here , no prizes for guessing who gets the gloves and who gets the cash...

 

[blade7]

What no drying ? She's spoiling you [].