When to use a GT3 vs 930 pump?
 

Just curious as to what criteria are used when deciding when the cost of a GT3 pump is justified in a high HP build?

Obviously, the GT3 pump is the 'gold standard' but up to what power levels, engine size, etc can the good old 930 pump be used? What are the differences (flow rate, pressure, etc) between the two?

Also, what is the difference between the 3.2 Carrera pump and the 930 pump? Up to what HP is the 3.2 pump adequate?

Thanks guys!SmileWavy

BTW, you always hear only about the GT3 pumps... what about the standard 996 pumps? Do they suck or something?

IIRC, the standard 996 pump is a completely different beast that is not compatible with our engines.

Correct.

Sensei Kenik, when would u choose a GT3 over a 930 pump (if at all)?

BTW, what pump r u using for your small displacement turbo motor?

The 996 (non turbo and non GT3) are wet sumps, totally different animal.

Doug

930 vs Carrera
http://forums.pelicanparts.com/uploa...1276727219.jpg

GT3 vs SC
http://forums.pelicanparts.com/uploa...1276727290.jpg

GT3 vs 964/993
http://forums.pelicanparts.com/uploa...1276727335.jpg

Specs, sorry can't find the 930 scavenge side spec
http://forums.pelicanparts.com/uploa...1276727381.gif

the gt3 pump has 2 scavange sections the others 1

Turbo pumps and GT3 pumps have the same pressure side. So both pump the same amount. The GT3 scavange is slightly larger than the turbo and with the added pickup makes it the best you can buy for a reasonable price. They will produce more oil pressure than needed.

Both are suited for oil control @ higher rpms.

3.0 and 3.2 are a great overall pumps with the same pressure size as the early 959type oil pumps. They are excellent for hot street and moderate rpm racing engines. I only say this as the scavange is not as adequate as one could ask for for high rpm applications. Although they have been used succesfully in racing engines.

What Aaron said. :)

Also, as a general rule, avoid oil pumps made out of Magnesium. After a while, they distort and become difficult to turn...among other problems.

Given an option, I'd always go GT3. I regret selling mine at the loe point in the market, as they are much more expensive now. That said, I now have a 930 pump with custom flow work done by Aaron, so am more than content without the GT3.

As a side note a prepped Carrera pump or even a well prepped early aluminum pump can be made to flow well enough for high performance applications. Why more don't do it is cost of work puts you into the range of a 930 pump anyway.

Thanks to all!

From what u guys are sayintg, the 930 pump is sufficient in all but the most extreme builds.

Hard to justify an extra $1k expense unless absolutely necessary.

Good information.

Just thought I would resurrect this old thread with a little bit of extra information since I just tore my 930 oil pump apart.
Since the 930 and GT3 pumps have the same size pressure section rated at 83 l/min and gear pump output is essentially linear (with same size and number and diameter of teeth, but different length of gears), then based on 2.005" long pressure gears and 3.016" long scavenge gears, the 930 pump should be right at 129 l/min on the scavenge side.

it's my understanding that if you update to the gt-3 pump then the piston squirters have to be changed out to the later larger size. I read that on here posted by one of the shops but i forgot where.

Choosing the right Oil pump should always be based on the engine and its use.

If your use may include lots of directional changes, then maybe more scavenge should be considered. If its street use only, and the engine shows no signs of a scavenging issue, more will probably not be required.

However, I hold the premise that more scavenge is always better than less. More will not hurt you in these Porsche engines, only help. These engines can always do with more scavenging. If you are running additional cooling parts, then you may want to consider a pump with greater scavenging ability. It may not help get any more oil out of the crankcase, but could over come some additional back pressure pushing the oil through a cooler. This side of the pump sucks a lot of air as well, so more can only help.

The only time when it can hurt you is when the crankcase is in negative pressure and additional vacuum can pull oil away from parts needing oil. Piston pins often show up first in this situation. Limiting the vacuum with a by pass device is often used here. As these engines typically run above atmosphere pressure, you will not have this problem.

The gear design used in these pumps on the scavenge side is not the most efficient. The Spur gear design works Ok on the supply side, but a gerotor type on the scavenge side are a lot more efficient.

As these engines do not run in vacuum, the spur gear works ok, but without any sort of air separator, oil temps do run higher; hence the reason to carry a lot of oil. The spur gear design churns up the oil more and mixes air into the oil at a higher rate than a gerotor style pump gear does.

On the supply side, if the internal parts that require oil show no signs of starvation, then more will be by passed back to the front of the line. Where it could help is when you elect to run at a lower pressure or additional oiling needs. Increasing clearances to lower the oil friction would be a good reason, adding a 2nd piston oiling valve could be another and the like. More volume to fill, more oil supply required.

As for having to go to a larger piston valve because you chose to use the larger pump, that's backwards. Going to the larger valve should be the reason to consider the larger pump.