Type4 turbo build advice

[Andy Somogyi]

Hi All,

I'm planning a type 4 turbo build for a 912.

I'm looking for three things: (1) reliability, (2) decent power (160-200 HP), and (3) affordability.

I'm a physicist as my day job, and in the past, I've worked in German car shop, and have built a number of T1, T4 and Porsche flat 6. This combination basically means three things:

• I'm poor
• I know physics, so I can talk about things like thermodynamics, fluid dynamics, heat transfer, heat capacity, all that fun stuff.
• I'm not bad with a wrench and TIG, and I can easily fabricate a turbo manifold.

I'm well aware of Jake Raby's excellent work, but sadly his engines are way, way out of my price range. Plus, I like building things.

I'd like to go turbo because under non-boost, the engine is less stressed than a comparable high-compression NA engine, and under boost, the engine's cooling system has to dissipate less heat than a NA engine producing the same HP. Plus, with a turbo, very fancy headwork is not nearly as important as an NA engine.

I'd also want the engine to look reasonably period-correct, I'd like to build a 912e turbo as Porsche would have done it in 1976.

So, here's my list of components that I'm considering:

• start with a builder 1.7 from a 914, but when I install it, I'll use the 912e engine tins.
• I'll mount the turbo down low, in the 930 location, air cleaner in the engine bay, and use the 911 engine mount holes for the turbo air inlet/outlet.
• Heads: AA Pistons ported 1.8 heads, with plugs at the 2.0 location, 44X36 valve size, $ 1,755.90. Seems like a good choice because of the extra material around the exhaust port, and the small-ish valve sizes.
• Cylinders / Pistons: AA Pistons biral 98 mm cylinders with forged JE pistons: $850. Nickies would be nice, but WAY out of my price range. I've worked some very rough calculations, with a 200 HP engine, I'm not sure the Nickies are required in terms of heat transfer.
• Crank: JE Pistons 78mm forged, chrome moly crank, ~$600
• full dynamic balancing by a reputable shop.
• oil system, undecided, might go dry-sump with a 911 oil tank and CB performance pump??? ($50 - $1000)
• piston oil squirters -- definitely case installed style.
• turbo: used Mitsubishi probably, I prefer the internal waste-gate style, electric scavenge pump.
• intercooler: Subaru WRX.
• injection system: Megasquirt full-sequential, wideband O2, boost control, with coil-pack spark control (engine management electronics is something I know extremely well, I've modified D-jetronic fuel maps in high school, and I work a LOT with control systems).
• rods: forged H-beam

This should make a 2353 CC engine, plan to set the compression around 8.0:1. I'm estimating that the airflow from the stock cooling fan might be enough for 200HP turbo engine, considering that the intercooler will also prevent a lot of heat from entering the engine.

So, questions...

Any experience with the AA pistons biral cylinders? Are these the spun-cast or sleave press-fit style. Any experience with the AA pistons forged chrome-moly cranks?

I've looked at the QSC nikasil cylinders, but can't seem to find much info on who's used them, what pistons/rings to use with them. The nikasil coating process is not that hard of an industrial process to do. Just not sure why I can't seem to find much info on who's actually used these in practice.

Any advice on who to use for a machine shop, to install the oil squirters, balancing, etc... I'm in Indiana, so local would be better, but I'm perfectly fine mailing the parts somewhere else.

Note, I do have access to the university machine shop, so I can easily check all of the specs on every part, and can do some machining myself.

Thanks

[Andy Somogyi]

Oh, and I'm also planning on having the Megasquirt control the cooling flaps, replace the thermostat with a stepper motor, whereby I control the flaps directly from the head temp readings.

The first engine I built, about 20 years ago now, a VW type 3, I made the mistake of not installing the thermostat, and the engine would never heat up. I've learned a thing or two about operating temperatures since then

[Clatter]

Wow.
Sounds like a great project.

A whale tail for the intercooler I presume?


I'd only have a couple of thoughts:
Many who build turbo motors go with larger exhaust valves, not so big on intake.
Maybe smaller on both to keep material in the heads and help sealing?

If you have access to a prototype machine shop, I'd be doing as much of the machine work as possible,
Including the squirters.

China birals are presumably less risky than China nickies, as the coating coming off inside the nickies causes more damage than the sleeves coming loose with the birals.
Don't hear too much about these because so many are scared..
You go first.

Crankshaft shops that do V8s and other such 'murrican cranks can usually do dynamic balancing,
Probably your best bet to stay local..

Stepper t-stat sounds cool for sure.

Make sure to post up a build thread when things start happening..!

[Andy Somogyi]

Oh no, absolutely no whale-tail. Sorry whale-tail fans, but I utterly hate the looks of them. My goal is to have something that literally looks like Porsche engineers could have made it in 1976, much like the 924 -> 924 turbo. I really want it to look 100% factory on the outside, the only thing I'd add is a tiny "turbo" from a 924 right under the 912e badge.

There is plenty of room in the engine bay, using the factory injection manifold for an intercooler. I plan on making some tins that divert the air from the decklid intake up through the intercooler and place a few electric fans behind the intercooler.

I work at the university physics department, so I do have access to the machine shop there. The shop is very much a conventional machine shop, as such, does not have any specialized equipment for automotive machining such as bore hones and so forth. But, do have the standard stuff like a mill, lathe, so yeah, I can machine fittings for the piston oil squirters.

I've also found Mahle biral cylinders for the Type 4 that are really cheap. I think I read somewhere that Mahle birals are spin-cast, but I'm not sure about the AA Pistons biral cylinders. I need to give them a call and ask them.

I'm also going to have the piston crowns, combustion chambers, and exhaust ports ceramic coated. Turns out, the ceramic coating is really cheap and is exactly what I'll need to help keep head temperatures down. Oh, what fun it is looking at all the heat-flow issues in an air-cooled engine.

I'll also need to check with AA Pistons to see if their 2.0 converted 1.8 heads have the proper 2.0 exhaust style, where the exhaust port is bored out, and the exhaust header fits pretty deep in the head. This very smart way of doing things, as it prevents a ton of heat from going into the head, and lets the heat straight out the exhaust.

But yeah it's just weird that there is literally no information on anyone who's used the QSC nikasil cylinders, no info on head studs, torque specs, pistons Almost as if QSC just lists them for sale, but no ones ever bought or tried a set. At least with the birals, they're pretty standard, and you don't need special head studs or different torque specs.

[Andy Somogyi]

Just heard back from AA pistons, and their biral cylinders are the spun-cast style, where the iron liner is first cast, then the aluminum fins are spun-cast around them. This is great news, because the risk of separation is WAY lower than the press-fit style birals.

Also, their 1.8 -> 2.0 914 heads use the Porsche style exhaust ports. This too is great news because it means that a very large amount is heat is NOT transferred into the head with the long bus style exhaust port, i.e. the header stick deep into the head and acts as a heat shield which helps to reflect the heat back into the exhaust pipe.

[Clatter]

QSC just makes things and lists them for sale.

Any/all QC/Testing/Trials/QA/Analysis is entirely up to the customer.

[Clatter]

With China parts, there is the additional task of verifying everything dimensionally.
Can add up to more than you save, if paying for this labor..
(not counting the costs associated with failures, of course)

With the metallurgy, all you can do is pray.

I have a set of AA P&L here on my bench that shipped with .0002" clearance - two tenths.

[Andy Somogyi]

With QSC, how the hell can you sell a product without testing it???

Anway certainly sounds like a company to avoid like the plague.

I've been in contact with AA pistons, and they really know their products, we were talking about heat conductivity in their biral cylinders, and they certainly know what they're talking about.

With AA, I get the impression that they do sell a number of Chinese products, but they do some pretty thorough testing of them.

Anyways, I need to make a few engine models in SOLIDWORKS to get a better idea if 96 vs. 98 mm biral cylinders are the way to go. The 98 will transfer heat better, but the 96 have a higher heat capacity, so could be more thermally stable. Not sure at the moment.

LN's Nickies would obviously be the best, but they're way out of my price range.

[wreck]

Ring Jorge at European Motor Works , they offer QSC Nikasil cylinders with matching JE pistons and rings that they have QA'd , it would be interesting to know if they get any life out of them .

[Clatter]

A 'number' of Chinese products?
I'd say that was the number of products they sell...

My AA P&L here, with no rings on, will sit vertically without sliding through.
The pistons are a 'light press fit' into the cylinders.

Get a set of those in an inspection room, with a digital height gauge, granite surface plate, etc.
Tell me what the tolerances are on the overall length, how square the cylinders are to the deck.

Send them back, try again.

I feel like such a sucker for even taking the bait on that garbage.
And to think there are still some Brazilian Mahles around...

AA selling so many P&L sets says more about the aircooled VW hobby than it does about AA.

You might be very surprised.

I say might, because, sometimes, they are actually pretty good.
Sometimes..
Just enough to make a liar out of you if you say they are all junk.

The manufacturer typically has no relationship with the designer, distributors, or end user.

[Andy Somogyi]

Would you guys recommend buying from European Motor Works instead of AA?

AA's heads do seem to be pretty decent. And yeah, whatever parts I get will have every dimension thoroughly measured on a granite table. I've got access to some pretty nice measurement equipment.

[bj]

at the hp levels you're looking for...you should research Wally's 2.0 stock turbo build...he hit 300-ish HP.

just another alternative to hit your mark and save some money.

BJ