Crowd sourcing a T4 turbo build

[kpick]

Hello all,

Thanks for the great site with loads on information. I’m new here and have spent too much time on this site.
I guess it’s time I jump in and start building my motor (I’m hoping with a lot of help from you all).

I titled my post "Crowd sourcing" because I'm wide open to advise and hopefully learn from other builds.

A little back story on my car and what I’m trying to do:
I inherited a Porsche 912 from my Uncle who passed away. (He was more like a father figure, so I really want to get this car on the road. It has tons of sentimental value).

I’m a college student with a limited budget (I know, sad story). I have a very good mechanic in my corner that will be helping with the build. He strongly suggested I ask lots of questions here as some people here may have built this same engine. “Let’s not reinvent the wheel”.

I’m hoping to learn from others and keep my mistakes and cost down.
I picked up an type 4, 1.7 engine from a Porsche 914.
The plan is to do a Turbo / EFI (micro squirt) build. I’m looking for a very streetable and drivable engine. Not looking for top horse power. Drivability and being able to do a 150 mile road trip is more important to me.

Now back to the “collage” student and budget. I need to keep cost down as best I can.

I have the engine and a very nice turbo (TD04L from a WRX). I’d like to have the input form the group on my build. So far I’m looking at:
Stock crank
Stock Rods
Possibly 93 or 94 dished pistons (8.5-1 compression or so)
Keep my jugs or purchase an AA P&C set from Aircolled.net?
Stock heads but 42x38 stainless valves with CB650 springs
Mild cam (maybe Web119?)
Micro squirt for the engine management
I am a bit confused on the cooling. Should I keep the stock T4 cooling, do an upright conversion or a 911 style fan? I really like the 911 style fan but again my funds are limited.

I’m hoping to start to amass parts (searching eBay, here, etc) and get to building this thing in the next few weeks.

I know this was long winded, but I hope to gain some knowledge form the group.
Anything you all would change?
Suggestions to save money?
Suggestion’s where to spend more money?

Thanks in advance and please drop some wisdom on me!
K.

[Rickster]

sounds like you and I are in virtually the same boat! Including the 912 from our Uncle...
After picking up an 1800cc T4 from a friend and running numerous rebuild scenarios with help from this forum, I have come to the conclusion that I will probably keep the stock rotating assembly. The only thing I will upgrade is the cam, and possibly go with a set of forged custom pistons. Custom, because I cannot find anything with the correct dish for my application in a 93mm piston.

AA sells a nice flat top set for the 1700cc T4 that should work fine if you plan to keep the boost down to about 10ish PSI. http://aapistons.com/collections/vw-pis ... -4-bus-914

With stock parts (including the 49-50cc heads) and a 0.030" copper head gasket your compression ratio should be right around 8.5:1. This will also give you a nice quench as well, the piston top being 0.050" from the head, assuming that the heads sealing ring has been removed and a 202.5mm deck height. Perfect for a lower boost turbo setup. Just tune it conservatively to avoid any detonation issues.

This should get you close to around 200HP at 6500RPM

Rick

[kpick]

Thanks Rick,

That's funny on the 912 front (let's race em'). Any idea on the cam you plan to use and do you think it's better to keep the stock jugs and have them worked on or just purchase a new set?

Also, I'm happy to keep the boot on the lower end. Again, drivability is my main concern. I'd be very happy with 200hp.

Kevin

[Rickster]

That kit I linked above comes with new jugs, I would use those as they are already honed to match the pistons. I was/am leaning toward the webcam turbo cam & lifters. Scat makes some cheaper stuff, but I don't believe those are nitrated? Being a hydraulic roller guy in the past, I am worried as hell about flattening the cam on break-in.

Rick

[Rickster]

Oh, you will likely want to swap 3-4-5th gears in your 901 transaxle as well. You can find used sets on ebay for around $150.00 a set

[Rickster]

At first I thought that turbo was going to be to small for you, but it looks like you will be flowing about 250CFM (0.12 cm/s) @ 6500RPM. Looking at that turbos map, it fits just right with peak efficiency just below 6500RPM.

With peak HP @ 193 - 6500RPM, and FWTQ @ 200 - 4500RPM (guestimates at 12PSI of boost)

Rick

[Clatter]

OG German cylinders are far better than China AA, FWIW.

[Piledriver]

Also note that head gaskets in any conventional form or material are not recommended on a T4.
Use cylinder base shims to set deck height.

The std AA pistons are hypereutetic (very high silicon content) and extremely likely to crack or shatter with any knock, even once.
Fine for NA use with reasonable compression/fuel, not turbo.

Mahle T1 94mm "A" pistons are about the right compression height, but the rods will need rebushed.
The std dual springs from CB or SCAT will be more than sufficient at the stated RPM and boost levels.

The T1 Mahles are good pistons and get used with ridiculous boost all the time.

AA makes T1 "true forged" 94s that might work but may not exist in the "A" compression height.
Same 22mm pin issue. These need .005" clearance.

The AA jugs have a reputation for being soft, and frequently are too long (3mm) and require machining.
Suggest buying them from EMW and merrily pay them to have them trimmed to the desired length.
Will be better and far cheaper than doing it locally unless you own the machine shop.

[kpick]

Thanks all...

I'll go with the Mahle T1 94mm "A" pistons and will be using copper gaskets.

It sounds like I can use the stock jugs and have them honed...is that correct?

PileDriver, when you state the "rods will need to be refurbished", is that in general or because I'm going with the Mahles?

Thanks again and please bear with me and my questions. (I'm still learning)

[kpick]

Oh, you will likely want to swap 3-4-5th gears in your 901 transaxle as well. You can find used sets on ebay for around $150.00 a set

Thanks Rick,

Can you give me a few more details on the gears? I will be rebuilding the unit that I have as the 1st gear syncro is shot. I've hear of using gears from a 914. Is that correct?

thanks again
K

[saltgrinder]

I'm running the AA 94's in my type 1 turbo at the moment ( thinking about using them for my type 4 turbo as well) they take a fair beating as far as detonation goes . Rattle a bit when cold but it makes you warm it up a bit, I used to run the AA hyperutectic 92's , I ceramic coated the tops and I ran them up to 20psi , they went really well but I leaned out once to often up top and melted one . Just saying you can get reasonable results from hypers just be careful on your tune and don't rev em past 6k

Richard

[Wally]

Thanks all...

I'll go with the Mahle T1 94mm "A" pistons and will be using copper gaskets.

It sounds like I can use the stock jugs and have them honed...is that correct?

Your stock cylinders are from your 1700 engine right? Those are 90,00mm diameter. Those cant be 'honed' to 94,00mm!
Honing is for keeping the existing bore. Boring is done to extent the diameter, then honing them to a finer wall mesh/pattern (wall structure for oiling) and size.

You could bore a 1800 engine (93.00mm Original size) to 94.00mm, but you have 90mm's...

Boring done well is expensive btw.
Using the Original cylinder is indeed best, but if your on a budget, buying a new set is more economical/safer imo.
If you're really on a budget (and with little experience in setting up a new custom EFI system on an engine), I would first test your current engine for compression and if its in good/reasonable shape, leave it. Buying new EFI parts is costly enough and getting the engine to run with is costs time (and motivation).

So, my move would be to better maybe try to get the engine to work and run as is (stock) with the new EFI system. Then, if it runs ok, add the turbo bits. Intercooling is very important and in a rear engined 912 you will better use all your creativity towards that first

BTW, stock T4 engine bits are pretty strong as is. I ran 220hp in turbo application with it pretty easily (but with a 914 2.0 engine as a basis, which is more powerfull to begin with). For up to 200hp and carefull tuning (most important part by far), the stock parts are fine.

GL!
Walter

[OriginalCustoms]

I took a bone stock, unmolested 1.7 and just added a K03 (off a modern VW/Audi 1. and MicroSquirt. Made my own exhaust setup using 914 1.8 'log' pipes.

Love the boost and despite not building up the motor, it's a ton of fun.
Don't break into the motor unless you have to fix something. Save the budget for building the FI and turbo setups. You can always dig into the motor later when funds allow.

[Piledriver]

The T1 Mahles have a 22mm pin.
The T4 rods have a 24mm bushing.

When you have the rods rebuilt, spec 22mm if you want to use the Mahle 94s.
The bushings are hugely undersized when installed and have to be bored to size anyway.

I fully concur that boosting a stocker (particularly a 1700 that you have) is a great way to start.