ZCAT3

Bud makes a great point - the way the car is set up will play a big role. The boost in my car starts as early as 1500 RPMs or so, depending on conditions (i.e in 4th gear under load - like up a hill - will bring boost on this low) and hits full by 2500 or so. With that wide power band the 4 speed poses no issues in that regard. It still is a pain compared to a nice 5 or 6 speed in terms of ease of shifting.

rickc

Please...A Mack Truck is hard to shift. My 930 trans with the short throw is much easier and quicker to shift than my SC's 915. I don't see the pain. By the way, my K27 starts to build boost at 2,000-2,500 with full boost by 3500 at 1 bar in first through third gear. I typically run out of road to really need boost by fourth.
Rick
'78 930

dom4471

taking out of the equation performance and looking at fun element only, think we all agree accelerating through the gears ie reaching the end of the revs in one gear and changing up is one of the most pleasurable parts of driving. so would have to go with 5 gears and better 6

Geoffrey

I think I'm the one who mentioned about the GT2 Evo cams. Its not that unusual to see boost beginning to build 1-2psi by 2500rpm. Most of the larger Garrett turbos I've used or seen don't make full 1bar boost until 3500+. The very large Garrett on my car does build boost quite quickly, but it has a rather small A/R turbine housing and a lot of time and money was spent in airflow improvements in the heads and 3.2 Carrera intake.

When I shortened my gearset 5th from 205 to 175, then 2-4 shortened to match, my car feels like it has 100hp more. It was by far the best upgrade for the money. Sure, I shift a bit more on the track, but the engine is exactly where I need it to be. The longer gearset had me waiting for boost, the newer shorter gearset is great. In fact, I was working on collecting the parts to go to twin turbo so boost would build sooner. Now, I don't think I'm going to go that route because I don't need to.

My friend is working on getting the parts to convert his car to a G50/01.

Eric 930

The 930 was introduced because Porsche wanted to race a turbocharged car in the World Championships of Makes. These cars were designed to race. I don't think they planned on the car still being sold 14 years later but the public loved it and the sales were good so they kept selling. Over the years their weren't a lot of changes made to the cars. Buy the late eighties Porsche was making some attempts to
make the car more apealing to the average Joe and not just the die hard racers and Porsche enthusiest. This is the reason you saw power seats evolve and then later on a 5sd tranny and a hydraulic clutch. These changes made the 930 a little easier to shift thus openning the the doors to a little bit softer market of drivers that couldn't over come the harsh feel of the more durable type 930 tranny. Though the 5spd is hands down smoother, it doesn't make the car faster. I personally prefer the 4spd because it not only works better with the car but it also gives the car a nostalgic race car feel that the 5spd takes away.

Eric 79 930

Geoffrey

The 5spd DOES make the car MUCH faster, especially when geared properly. Porsche moved to a 5spd because it was the next evolution in the model line and because it was stronger and better matched to the engine.

Randy

In any vehicle, there is a point in engine speed where maximum torque is achieved. Some cars have a very peaky curve, some longer and flatter. Any vehicle will accelerate at it's maximum at the point of maximum engine torque, be it your lawnmower, or a super special hard edged wallet exploding 930.

When the boost comes on is a misleading argument because it's not necessarily indicative of or related to maximum engine output, and it's ability to accelerate optimally. Only in the case of the boost hit coinciding exactly with maximum torque that is completely flat until redline (not possible unless redline coincides with torque drop off)would a 4 speed be superior to 5 speed.

Now, in any transmission, manual or automatic, extra splits will keep the engine revolutions nearer it's max output, and will drop to a higher beginning engine speed between shifts. By definition a superior situation. There are countless real world examples that support these facts, from fire trucks to Porsche Fabcar to F1.

Now, in our 911 turbos, the issue has a variety of practical (and apparently emotional) matters that probably make the distinction less important. In the theoretical world more gear splits are superior no question.

JBH

I don't think anyone is listening to Geoffrey. The G50 variants from the 89-on turbos are stronger than the 930. It is a mistake to assume the 935 four speed is the same as your stock tranny.

This sounds like a group that is trying to convince themselves that old technology is better than new. I have a 5 speed and I wish I had a six speed - just for the reasons Geoffrey and Randy listed.

PT

Just add fuel to the fire...

I also agree particularly with Randy that having an extra gear "can" definitely make it infinitely easier to keep the car @ its torque peak. And I also believe Geoffrey's comment that the G50/50 is stronger than the 930 even though all indications are the 930 gearbox is plenty strong.

Haven't driven a 930 with G50/50 & based on my own experience with the 4 speed where my boost also peak around 3500-3800rpm, I can say that there are definitely corners on the track where I wish I have a closer ratio box. A prime example is the off camber at Watkins Glen where 2nd is way too low & I am a sitting duck in 3rd And I verified it with another instructor in our region with a 500hp+ 934.5 w/ EFI that he's in the same boat.

ZCAT3

It is interesting how people take their own experience and treat it as gospel. As a person that has both a 4 speed 930 and a 6 speed 993TT I can tell you that from my experience the 4 speed 930 gearbox can be made to fucntion very well in terms of the power band. Here is an example - look at the dyno sheet for my 930 (this is prior to going to 3.4 and twin plug, but it makes the point). I have over 350 ft. lbs. of torque from 3600 to 5500 RPMS. If I run the car to around 6000 and then up shift I will be around 4000 RPMs, in my prime power range, immediately.

<img src="http://boards.rennlist.com/upload/Old930Dyno.jpg" alt=" - " />

Eric 930

I think if you add up the extra time that you spend shifting a five speed it will be greater than the amount of time that you loose with a 4spd not being in its optimal power range. So at the end of the day you have two transmissions that perform great in there own way except one is harder to work on, more expensive to fix and less available if you need to replace it.
-------------
Eric

Randy

Look guys, this is really a silly debate, that has hung on because some of you feel that there is some insinuation that a 930 transmission is a p.o.s. Obviously it's not. It does the job very well with four ratios.

Yeah, a 930 4 speed "can be made to work" (better), but made to work like what, a G50/50 5 speed? And thanks for the laugh, you've got to be kidding about drawing a time comparison between shifting and not having to. And like anyone on this board cares what they cost to work on, judging by the lists of mod$. These all really just sound like excuses and justifications.

All other factors constant, the simple undisputable fact, and the answer to the original question is; a 5 speed G50/50 will outperform a 930 4 speed, in all ways except weight, period. More splits are always superior to fewer. In addition to it's superiority in this respect, it is also a better design and will live considerably longer under the same conditions.

This is not a personal opinion, it's a fact that can easily be substantiated by data. The thing is, who cares anyway? It's just a simple answer to the question that was asked at the beginning of all this, not a personal attack.

Is the cost and hassle of fitting one to your car worth it? Probably not for 98% of the 930 owners out there, and then only when you really need the value of proper gear ratios and the understand the application of torque multiplication.

Eric 930

Well since this debate is silly, the more splits the better, money isn't an issue and you don't loose any time shifting, why don't you quit debating, hire an engineer and built a 20spd and go shifting.

rickc

Actually it would be helpful to get an idea of the costs associated with buying and modifying a five speed. This in comparison to modifying a 4 speed. Any takers?
Rick
'78 930

Geoffrey

A G50/01 or 02 can be had for $2000 as a core. You then have choices, gearsets go used about $300 ea, new they are about $600 ea. Steel synchros are about $1,600 for the entire set and about 8 hours labor is required to rebuild the box.

I spent $4,000 on my G50/50 for 4 gearsets, steel synchros, and a couple of sliders that were worn and the labor to put it together.

You'll need to add another $1,200 to have it shortened to fit in a pre 89 chassis, replace the foot pedal assembly, purchase the hydraulic lines and slave cylinder.

In all, it is not cheap to convert, hence the answer to the original question. If it were me, I'd spend the extra money and purchase an 89, 91, 92, or 94 model.