Talk me out of/into a Turbo conversion

[Raceboy]

Twin plugging is obviously beneficial to turbo engine. Where did you take it that turbo engine is low comp? Yes, low static CR but boost effectively making it very high CR engine and whatever type of pistons you have it still halves the time needed for the flame front to travel meaning you need less advance and you have much better resistance to knock (because knock treshold moves further from MBT).

IMO best bang for the buck mod for 3.2 is turbocharging it, no contest. As noted above the trick is to spare poor 915, you could do this by controlling boost electronically depending on gear to reduce torque in 1st and 2nd gears.
And no, there is no need to purchase EBC kit for that (along with WBO2 kit, EGT kit, knock kit etc) as you can buy VEMS PnP for the price of two or three of any of those mentioned and have it all in one box.

['76 911S 3.0]

Don't forget oil cooling upgrades if you do not have at minimum a Carrera cooler.

One of these days I'll get around to making a list of all the parts I required for the turbo build but I'm actually quite terrified at how much I have spent doing it (and that's on top of the almost $15k I spent on rebuilding the engine).

[75 911s]

Yes I have ER finned cooling lines and a widemouth carrera cooler with a relay/fan.

@Raceboy, my ignorance is exposed! Makes sense, I was looking at the static compression ratios. Like I said I have a lot of research ahead. Conversations like these help immensely because it gives me a framework to start with.

[quattrorunner]

As far as twin plugging NA: the dome of real high compression pistons have a bit of an problem to go around as opposed to a flat area free of angles or obstacles. Twin p[lugging puts a spark on each side of essentially two areas....

[RarlyL8]

The 915 is just fine paired with a mild turbo build, just as I did with the SC/930 in my signature line below. 350whp with short 915 gears, narrow body tires and a curvy road would be a riot! You also would not need a big oil cooler or intercooler. Go big and you need a 930 4spd and a lot of expensive add-ons to support the power. Both are great fun, which way you go depends on what you want out of the car and your budget.

[Mr9146]

Originally Posted by RarlyL8

The 915 is just fine paired with a mild turbo build, just as I did with the SC/930 in my signature line below. 350whp with short 915 gears, narrow body tires and a curvy road would be a riot! You also would not need a big oil cooler or intercooler. Go big and you need a 930 4spd and a lot of expensive add-ons to support the power. Both are great fun, which way you go depends on what you want out of the car and your budget.

We’ve been running non-intercooled turbo motors in our 75 Carrera for well over 20 years and hundreds of thousands of miles.

The current motor is a 3.2 with 8.5:1 compression, 964 cams, and a K27 backed by a euro 915 with LSD. Works great.

Before that it was a stock 3.0L non-intercooled motor...went about 150K miles on that one...daily driver...went cross country twice...never missed a beat.

I still think he’s be better off with a 3.6

[quattrorunner]

I agree with Brian, a mild turbo boost pressure engine with short ratio 915 gearbox is an absolute blast! However knowing that you can safely raise the boost for more power becomes an ever increasing reality that you want to realize after time. If you are diligent and can control your boostaholic urges, you can stay below 7 psi and the transmission will be fine. All that being said, I went through to 915 gearboxes at Stock 930 boost pressure (.8bar).

[Tippy]

Originally Posted by Mr9146

We’ve been running non-intercooled turbo motors in our 75 Carrera for well over 20 years and hundreds of thousands of miles.

The current motor is a 3.2 with 8.5:1 compression, 964 cams, and a K27 backed by a euro 915 with LSD. Works great.

Before that it was a stock 3.0L non-intercooled motor...went about 150K miles on that one...daily driver...went cross country twice...never missed a beat.

I still think he’s be better off with a 3.6

Sure, you can run without an intercooler, but your chances of detonation go up and you leave a ton of power on the table. Less timing and hotter, less dense air.

Intercoolers have gotten so cheap, that buying an eBay special and having it adapted to a 911 doesn't cost that much. Many here have done it.

[75 911s]

Originally Posted by flat6pilot

Parts list from my 1980 SC conversion. (360whp/324tq)



.

This is really helpful, thank you!

Originally Posted by LOWFAT

It can also depend on your driving style and the kind of roads you have available to you. Tight twisty roads staying naturally aspirated will be the better choice as the car is more controllable and more enjoyable. If the roads are a little more open with long flowing curves or a lot of highway driving the turbo wins hands down.

Looking back at the last 3 years it's been mostly freeway!

Originally Posted by RarlyL8

You could go a couple ways with a turbo build; keep the 915 and build an ultra quick spooling mild turbo engine that would be a riot to drive in the twisties or add a 930 tranny and build a yellowbird killer. Either way would be tremendous fun!

School me. What would be your cam, pistons, turbo etc setup for a "mild turbo"? Are you just saying limit boost via the Tial?

Tell me more about Vems.

My 915 is non LSD, what are the implications, if any, of that in terms of adding a turbo setup?

Originally Posted by quattrorunner

I agree with Brian, a mild turbo boost pressure engine with short ratio 915 gearbox is an absolute blast! However knowing that you can safely raise the boost for more power becomes an ever increasing reality that you want to realize after time. If you are diligent and can control your boostaholic urges, you can stay below 7 psi and the transmission will be fine. All that being said, I went through to 915 gearboxes at Stock 930 boost pressure (.8bar).

I don't understand the relation of the short ratio to boost pressure. Would this be trying to emulate a 4spd 930 trans? or what is the advantage?

For non IC setup, is it worse in extreme heat environments? I'm in Vegas and I drive my car in the summer months. Ambient temps can get to 110. I also sort of want to use the new wing I just installed. It's a glass whale grafted to a steel decklid, so no immediate room for an IC unless custom like some I've seen stuffed up into the top of the bay. I also like switching to my stock decklid since it's generally a better look with super skinny hips.

What 930 oil pump am I looking for? Are there core trade opportunities for my stock 3.2 pump?

When I send my case to Ollies, ( I spoke to Zack last week) I need to specify 930 squirters? Are they just higher flow? whats the dif? Any other case mods I should be aware of?

Is the scavenge line (like gravity feed on 3.0) strictly a 3.0 conversion thing? Does that relate to my build in any way?

This is exciting, I think I'm sold on the conversion. Now I just need to start my own sunglasses company to finance my new habit. *uhhh TurboKraft intercooler....DROOL..... I think I'll call my company Turbo Shades. How does that sound? :-D (Totally kidding - Ordered me some boosted shades last week!)

[Hill3312]

Originally Posted by 75 911s

Now I just need to start my own sunglasses company to finance my new habit. *uhhh TurboKraft intercooler....DROOL..... I think I'll call my company Turbo Shades. How does that sound? :-D (Totally kidding - Ordered me some boosted shades last week!)

- The best part is making a video series and writing off the entire turbo conversion as an advertising expense. Thanks for the support by the way, good luck on your journey!

[jsveb]

Originally Posted by Hill3312

- The best part is making a video series and writing off the entire turbo conversion as an advertising expense. Thanks for the support by the way, good luck on your journey!

‘Like your way of thinking.

[RarlyL8]

Mild turbo build would not require much more than an exhaust change and intercooler. You already have the SC /Carrera cams, Motronic EFI and C/R to create good torque and drivability. Add my tuned headers and a GT30 or like quick spooling turbo with large intercooler then tune the EFI with a chip and fuel pressure mod. Add posi, bearing retainer and HD side plate to the 915. Oil tank will need a mod if using a return line. That’s about it. Crazy fun. But if the big power bug hits you a tranny change will be needed along with suspension brakes and everything else to support the power.

[Carbster09]

tough choice ... my only comment is the boost is addictive. No doubt about it! I ended up with my boosted / modded 930 almost by mistake. A dude needed the cash and I bought it with the intention of flipping it for a tidy profit. Well, love the thing. If I don't get stupid and buy a GT3 ... I will be buried in this!

[quattrorunner]

Originally Posted by Carbster09

tough choice ... my only comment is the boost is addictive. No doubt about it! I ended up with my boosted / modded 930 almost by mistake. A dude needed the cash and I bought it with the intention of flipping it for a tidy profit. Well, love the thing. If I don't get stupid and buy a GT3 ... I will be buried in this!

I’ve recently driven a 991 gt3 and it’s great but our cars feel quicker with simple upgrades. At least till you go around a corner.

[75 911s]

So sounds like with my stock components on my car (ie manual brakes and 915) I might be best served putting the 3.2 back together fresh with existing Mahle 9.5:1 compression and running mild boost on that. Still a 8k proposition but better than 15k and no need to go power crazy on such a light car. Especially after coming off a tired old 2.7.

That could be the most economical approach. It's not future building though, so If I decide to increase boost I would need to later do a top end and swap out the pistons. Maybe I can preplan a bit and upgrade the case, pump and rod bolts/studs as planned anyway. Any problem with running a turbo pump in there on the stock pistons. By the way, I have no harness, no motronic, I suppose I could source a harness and stock manifold.

[quattrorunner]

Sense you’re already in there I’d go with lower compression.
Yes you’ll have a giant smile with only .4 bar compared to even an sc3.0

[sundevil64]

You should buy my 79 rebuilt turbo EFI motor and 4 speed that I have in my Carrera so I can put a 3.2 back in it.

[Raceboy]

Originally Posted by RarlyL8

Mild turbo build would not require much more than an exhaust change and intercooler. You already have the SC /Carrera cams, Motronic EFI and C/R to create good torque and drivability. Add my tuned headers and a GT30 or like quick spooling turbo with large intercooler then tune the EFI with a chip and fuel pressure mod. Add posi, bearing retainer and HD side plate to the 915. Oil tank will need a mod if using a return line. That’s about it. Crazy fun. But if the big power bug hits you a tranny change will be needed along with suspension brakes and everything else to support the power.

Why would it make sense to buy chips for Motronic, buy RRFPR and still have injectors totally maxxed out and AFM barn door complicating piping very badly?

One would still need WBO2 kit and when putting all things together it will almost make amount that you could buy VEMS PnP for and it already has WBO2, works on stock sensors and you can use proper injectors without any hack jobs.

What amazes me is that when it comes to building engine itself, people do not hesitate coughing up few thousand just to get 0.2 liters of more displacement (which is pintless performance wise) and yet trying to save few hundred when deciding whether buying proper ECU vs using Motronic with hackjob...Can you explain me this please?

[baloo]

Originally Posted by Raceboy

......
What amazes me is that when it comes to building engine itself, people do not hesitate coughing up few thousand just to get 0.2 liters of more displacement (which is pintless performance wise) and yet trying to save few hundred when deciding whether buying proper ECU vs using Motronic with hackjob...Can you explain me this please?

Yah, it's a peculiar, and predictable (!), process of thinking.
My favorite is the investment in titanium lug nuts to lose a pound in unsprung weight, but meanwhile, the driver gains 20lbs over the year.

We see it over and over in similar performance car forums -- where sinking $$ into rebuilding an engine "to be more robust" produces minimal improvements in performance, compared to relatively simpler changes.

Trying to find a human behavioral explanation for this, I think it has something to do with the satisfaction of knowing something is technically and engineering-wise more robust, and thinking that dollars-spent equates with peace of mind.

I admire the enthusiasm, thinking and planning that is being put into this.
Will be interesting to see where this project is in one year, or whether it succumbs to economics, job-related-requirements, relationship problems, newer shinier objects, or just project fatigue.

[75 911s]

Originally Posted by Raceboy

Why would it make sense to buy chips for Motronic, buy RRFPR and still have injectors totally maxxed out and AFM barn door complicating piping very badly?

One would still need WBO2 kit and when putting all things together it will almost make amount that you could buy VEMS PnP for and it already has WBO2, works on stock sensors and you can use proper injectors without any hack jobs.

What amazes me is that when it comes to building engine itself, people do not hesitate coughing up few thousand just to get 0.2 liters of more displacement (which is pintless performance wise) and yet trying to save few hundred when deciding whether buying proper ECU vs using Motronic with hackjob...Can you explain me this please?

I think he was just looking at it from a stock 3.2 standpoint with minimal addons to convert to a turbo setup. So in that scenario it would include motronic I guess. But you're right, after dropping thousands in pistons and other upgrades, it would be better served to use a proper ECU. As I mentioned, I don't have the stock harness or computer or intake, so unless I found a complete setup for pennies, I doubt I would go that route.

Originally Posted by baloo

Yah, it's a peculiar, and predictable (!), process of thinking.
My favorite is the investment in titanium lug nuts to lose a pound in unsprung weight, but meanwhile, the driver gains 20lbs over the year.

We see it over and over in similar performance car forums -- where sinking $$ into rebuilding an engine "to be more robust" produces minimal improvements in performance, compared to relatively simpler changes.

Trying to find a human behavioral explanation for this, I think it has something to do with the satisfaction of knowing something is technically and engineering-wise more robust, and thinking that dollars-spent equates with peace of mind.

I admire the enthusiasm, thinking and planning that is being put into this.
Will be interesting to see where this project is in one year, or whether it succumbs to economics, job-related-requirements, relationship problems, newer shinier objects, or just project fatigue.

Ha! Agree with a lot of what you are saying. I do a lot of lightweight mods for two reasons. 1. It's fun and it's tinkering and creative. It definitely brings joy in my life to work on the car. 2. It can lead to better performance, though the reality of it is very small gains probably.

Regarding gaining 20lbs..yes we all face that problem, the titanium lugs reference is funny. I actually rejoined the gym about 4 months ago and have been working on myself and I think working on my car inspired me to work more on my own body! :-D

Finally, I'm also fascinated by threads with big projects. I'm a forum junkie and It's crazy to check that first post date and see how long projects actually take. Many of course never get finished. I like bumping those threads and providing positive comments to see if I can kickstart them again. You never know how a small bit of encouragement can re-ignite enthusiasm.

In my build thread I talk about one of my core philosophies (regarding the car) is to keep it drive-able. No matter what mods I do, I plan out medium to small projects, complete them and then drive the car again. It keeps motivation up.

Buying this core was a great opportunity to keep my car running but to solve the long term problem of the 2.7 needing a rebuild. Though I can't predict what the future will bring, I think the main thing that will see the project through is the joy that I'm getting out of the whole process, whether it be building, research or just interacting with the community.

I came into my car project about 3 years ago with basic mechanic skills. I never thought I could rebuild a precision engine on my own. I've gained confidence in my skills by tackling various projects on my 911 of varying difficulty. This engine build will be the culmination in my mechanical skill set. Luckily I have a lot of help from you fine folks who have the experience I lack. :-)