915 for 300 hp upgrades?

[ghost1001]

Hi All,

I have searched and found a few threads on the subject....most were older. I am seeking advise on modifications to a 1982 915/63 trans.

I have the trans and it needs to be opened to address 1st and 2nd syncros at the least. The motor will produce approx. 305 hp and 290 lb ft. The car will be right around 2000# (hopefully) and be primarily used on the street.

The car will not be abused but it will be driven. Putting cost aside what would be the best modifications. I have read about the following:

fluid cooler, advise, links, kits, etc?
LSD, which one, what ratio?
Everything Wevo...any advise or experience, they seem to have the most fully developed "package"

Thanks for the help

as she sits...
Kevin

[Steve@Rennsport]

Kevin,

290 lbs-ft is a LOT of torque for a 915.

At the very least, I would install a cooler & pump, billet sidecover, Wevo bearing retaining plate, and a good LSD such as either Guard, OS Giken, or ZF.

Naturally, careful & proper assembly is critical for durability.

[Joe Bob]

WEVO has a number of upgrades. The bearing brace after you confirm that the bearing shell hasn't ovaled out in the intermediate plate. Mine went after 30K miles and took out 2nd gear.

The gated shifter is a good idea as well.

[kenikh]

What about the Wevo oil spray system? Seems that this dramatically helps with temps and lubricationat the mating points. Seems that this would be very desirable.

The Wevo side plate is nice because it uses the larger 930 bearing and the LSD helps since it distributes the torque to two axles for less torque shock of the internals. I have been thinking a lot about the OS Gikken since it seems to be the only clutch type LSD that offers fully progressive lock up, from zero to 100%.

Steve, what is your experience regarding the primary failure mode in these high HP applications? Upgrades that support these seem they'd be the best upgrades.

[Matt Monson]

I would add a new billet mainshaft to the list at those power levels.

[ghost1001]

What do you guys think about a 930 trans? Will that bolt up in '76 chassis?

[Matt Monson]

Tell us about this engine. Is this is 911 engine? Where does it make those power numbers? Is it peaky or is it a big torque engine with power all over the place?

[kenikh]

Originally Posted by ghost1001

What do you guys think about a 930 trans? Will that bolt up in '76 chassis?

I think it is a 4 speed. Strong, but LAME.

Originally Posted by Matt Monson

Tell us about this engine. Is this is 911 engine? Where does it make those power numbers? Is it peaky or is it a big torque engine with power all over the place?

This is a great point; if your torque peak is 300 lb/ft @ 4200 RPM, it is a much different dynamic than if it is 300lb/ft @ 2700 RPM.

Originally Posted by Matt Monson

I would add a new billet mainshaft to the list at those power levels.

What's the $ hit on one of these? Similar to a 904 mainshaft (~$800)?

[ghost1001]

Here are a couple of dyno sheets...let me know what you think.

Please keep in mind that this is somewhat of a theoretical discussion....I have a 1982 3.0l sitting on an engine stand in my shop that will most likely get built.
I am looking for possible options for my project (outside the box).....drum roll please:

2008 4cyl 2.5l turbo subaru boxer engine.....don't abandon me yet!!!! Putting all of our “Porsche pride” aside for a second it seems that this engine in particular deserves some consideration/scrutiny. I have not found many cons yet, other than Porsche did not build. However, I have not found anyone who actually drives a car with one in it either. I am VERY reluctant to start a Subaru thread!!!

[Matt Monson]

Originally Posted by kenikh

What's the $ hit on one of these? Similar to a 904 mainshaft (~$800)?

I'd love to find an $800 904 mainshaft. That's less than we pay to make them. The 915 mainshaft with a 1st gear ratio of your choosing is $2300. The gear is $750 of that price.

[Gunter]

There are a few threads on how people busted the 915 adding that kind of torque.
Also, the '82 still has the smaller CV-axle shafts which Porsche enlarged successively over the years as power increased. I wonder why Porsche did that?
And also changed to the Getrag transmission.
I wonder why?

[Matt Monson]

Originally Posted by ghost1001

Here are a couple of dyno sheets...let me know what you think.

Please keep in mind that this is somewhat of a theoretical discussion....I have a 1982 3.0l sitting on an engine stand in my shop that will most likely get built.
I am looking for possible options for my project (outside the box).....drum roll please:

2008 4cyl 2.5l turbo subaru boxer engine.....don't abandon me yet!!!! Putting all of our “Porsche pride” aside for a second it seems that this engine in particular deserves some consideration/scrutiny. I have not found many cons yet, other than Porsche did not build. However, I have not found anyone who actually drives a car with one in it either. I am VERY reluctant to start a Subaru thread!!!

You won't see me being the one bagging on this. Not only did I get my start in this industry playing with Subarus, I still play with them. There are 3 Porsches and 3 Subarus in my garage these days, and one of those Porsches is getting a JDM 2.0 STi swap put into it.

Do a search on the subject. Last year (or was it two years ago) a member put a Subaru H6 into his 911. Absolutely beautifully done install. It's a great thread over a dozen pages or more. It will inspire you further.

[ghost1001]

Matt,

I have the thread bookmarked!!
putting a 3.3 in my SC

My idea, if I go this way, will be to do a very professional job to high standards….this will not be a hack job and I would try to do most without any cutting which I think is very possible.

Tell me more about your project...is it the 914?

What do you think of the 2.5l turbo in the 911....will the trans play along or go to pieces? You build these things (transmissions), no?

[ix0ifan]

The first graph just isn't correct as the crossover is at about 3800rpm so someting is wrong with the zero.

The second curve shows the crossover at the correct rpm (5252) but the torque should be 300 lbs ft and the HP 270.

I am, of course, assuming that torque is always a larger number than HP until 5252rpm and that HP is always a larger number than the torque after 5252rpm.

[wesayso]

Originally Posted by ix0ifan

The first graph just isn't correct as the crossover is at about 3800rpm so someting is wrong with the zero.

The second curve shows the crossover at the correct rpm (5252) but the torque should be 300 lbs ft and the HP 270.

I am, of course, assuming that torque is always a larger number than HP until 5252rpm and that HP is always a larger number than the torque after 5252rpm.

Check out the different numbers left and right of the first graph... the crossover still is at 5252 rpm, the scales are just different on torque and HP.

[ghost1001]

sorry for the dyno sheets...I pulled them off the net....and yes they are laid out different and from 2 sources.

[Matt Monson]

Originally Posted by ghost1001

Matt,
Tell me more about your project...is it the 914?

What do you think of the 2.5l turbo in the 911....will the trans play along or go to pieces? You build these things (transmissions), no?

It's not the 914 in my signature (the Porsche purist in me considers it a sin to do something like that to a Can Am LE 914). But it is my '73 914.

To be honest I go back and forth between ripping the 2.5l NA engine out of my daily driver (225chp/240tq) or using the JDM Ej20G (250chp/240tq). I am probably going to end up with the 2.0l because I want to rev it and feel that it's more "correct" for how an old 914-6GT would have been set up. 7500rpm redline just seems right in that chassis.

I think the Ej255/Ej257 engines are a great option for a 911 swap. Just don't go too overboard on the power mods. It's pretty easy to retune them and have them at 400chp without a lot of effort. If you go with the OEM ECU you'll want an 04 or 05 engine and ECU because of the security system. The later canbus ECUs require the steering column and laser etched key to get around the lock out feature to get the car started.

However there are plenty of aftermarket standalones out there. I've got a few friends running Hydras on their car. We run the Vipec on the racecar that I am affiliated with. We found if had better resolution and have a local tuner who knows the unit well.

Gearboxes are my business. We don't really do much building in house. We're primarily a manufacturer of the parts. On my personal car I will be using all new gears, ring and pinion and mainshaft. The modern metallurgy is just better, and if cost is no object there is strength to be had there. I am also planning on using straight cut gears, because they are stronger. I am doing a "916" conversion on the car with the engine. I do think the 901 gearbox is questionable for what I am doing and how I intend to run the car.

For whatever reason, straight cut gears have never been really popular in Porsche circles. In fact, it's only been in the last 5 years or so that Porsche has been putting them into Cup Cars. We are now making 915 gears in straight cut in limited ratios for some of the more popular positions that guys break. They are starting to catch on and people are starting to use them. I think over time this will become more of the norm and we'll expand our offerings of them for both 901 and 915. But as much as you can afford to replace in the gearbox with new I would recommend. New stuff is stronger than 30 year old Porsche stuff.

Above you asked about an LSD. If it's a street car you don't need a true LSD with clutch plates. Get a torque biasing differential (TBD). It will get the power to the ground under acceleration, be service free, and save you money over an LSD.

But the bottom line is I will tell you what I tell the v8 conversion guys. The 915 will hold together if you drive it like an adult. No hard launches. No Saturday night trips to the 1/4 mile. No slamming 3rd gear downshifts to get ready to launch out the other side of a corner. Treat it with some respect and you'll be fine.

[Bill Verburg]

When I had my 300+ hp 3.8RS engine hooked up to a 915/67 the side plate would distort and weep if you got on it hard in the lower gears.

That can't be good for the internal alignment of the cwp

[safe]

I'm abusing my -77 unmodified, but rebuilt, mag cased 915 with 265hp and 240 ft lbs. It has over 220 ft lbs from 2000 rpm. Not sure how long it will tolerate this treatment, but I am (or try to be) gentle on 1st gear.

[mike the snake]

My race car has about 350 horsepower and uses a WEVO equipped 915 box. The car has been raced for a long time with this box. It has custom gears and the WEVO internals but stock side plate.

I plan to install a pump and cooler plumbed into the fill and drain plugs as a first stage, maybe go to the internal sprayers someday.

Keeping the gearbox cooler is crucial to making a weaker box hang with big power.

Somewhere I was reading specs and just the addition of a pump and cooler upped the torque ratings by quite a bit.