[flash]

a couple of tips that should be obvious:



regardless of who it is, unless you are willing and prepared to write off the cost of the kit, avoid at all costs a kit that requires you to do your own tuning - get them to do it, or provide it, but leaving it up to you to go and get it done only opens the door for them to blame problems on your tuning, and not on their kit - there is a lot of work and math involved in forced induction, and it is very easy to screw up



also, ALWAYS have a used turbo rebuilt before installing (i'm not a big fan of used compressors regardless, and will not use them in any car i am working on)



when factoring in your time, count the things you won't be able to do as a result, and the costs of that - for me, many projects are better served by farming it out - some things though i just plain like to do myself, so i consider that "vacation time"

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[xrad]

NO I did not contact them. Their price is pretty good. But I have to agree with Flash on the tuning. If they supply the kit, they should have already tuned one and can tune yours as well.



Of course, in MY build, I am combining some components to make it work. these components are fairly inexpensive. I do have some issues though.



1) lowering compression with "968" turbo mahle pistons and keeping the standard 968 crank OR using 944 crank. I chose 944 crank as I can increase RPMs slightly if needed. The "968" mahle pistons are offered by only one retailer(they hold the rights). However, you have to overbore the block to 100.5mm. I do not want to touch the block (as long as cylinders are within round limits and bores look good). Some things to think about with my choice: ~9mm shorter stroke exposes a portion of the cylinder to the initial combustion. Also, compression ration may be lower than i really want. But I can always increase boost......Time to break out the math skills...



2) I am using 944 exhaust technology. If I really wanted a racecar, I would have equal length exhaust manifold piped to the front right of the car, and a passenger side downpipe. and then the cool side would be in front of the engine. and there would be a wide open wastegate. I chose the 944 exhaust plumbing because I am lazy and it is easier and the parts are all over the place.



3) clyinders are alusil not nikisil. I don't want to have these bores refinished.



4)KISS principle: use readily available parts.



5) manifold: I chose to combine the 944 turbo mani with the 968. runner will not be optimal at low rpms.



6) My slightly used turbo will undergo a rebuild at a friend's turbo shop



So my ultimate BIG problem will be the manifold. it will have to be welded to combine the 944/968 parts and internally smoothed. also, I want to keep the 968 throttle body and will have to mount it to the 944 mani as well.

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[flash]

yup - projects like that are a mixed bag of nuts - fun, but complicated - but, you know that going in - it's different with a "kit" where you expect to just bolt it on and go



it will interesting to see this one as it develops - i love this stuff - i'm going through a lot of the same thing as i develop the chassis - clearly i need therapy

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[xrad]

Hey , anybody know the true cc's of the 968 head chambers???





from my calculations, if I use the 944 crank, i get an 89% stroke of the 968 crank which equals about a 2661 to 2679 cc displacement, down from 2990. However, CR decreses too much..somehwere down to 6:1...but I can't calculate it accurately without true chamber CC's.



Now, If I use the Mahle 968 turbo pistons with the 30cc dish, them CR comes out to ~ 8:1...that is driveable, much better than 6:1, BUT i have to bore the block .5 over and get it "alusiled" and rotating mass is near the same...



forget it, I just realized that I calculated the stroke difference with the decreased crank pin diameter and not the RADIUS, doh



Recalculated, the "De-stroker" 944 crank gives me overall smaller piston rise so this = about 38cc increased top end volume and a CR of about 7:1..that I can live with ...AND the overall cc's still decrease to about 2700 which you can't help (piston travel at both ends is less). with the turbo , the volumetric eff will jump way back up with 16valves and my effective ratio will be around 12-13:1 (what I am aiming for)



OK, so back on track..pheww, really did not want to bore block...

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[xrad]

just found out that Mahle makes STANDARD bore 104mm 8:1 comp pistons. Sold by Andial,,and they sell carillo rods as well for the 968. just need a set of rings...



won't have to bore anything out....

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[xrad]

looks like I don't have to go any further than Lindsey Racing. They have two types of pistons to choose from in 104mm size. The mahle's come with rings. there is a turbo set but it's another 800$ and 104.5mm. they also hav all the bearings, and carillo rods.



I think I can go with stock pistons and rings (Mahle w/chrome rings) for 1200$. carillo rods about the same $.



Now to the issue of the balance shafts?????? how do I balance this monster?? (of course i would have to worry less if i stayed with standard crank) anyone have any ideas? I could leave them alone or I could find a way to balance them.......

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[xrad]

spent some time on the phone with Mike of Lindsey racing. Very helpful!!



So the block is impregnated with silicon so it is an alusil block, not just lined cylinders. So boring the 4 holes is not so bad now, just have to get the right hone afterwards. That is good because then I am opened to a whole bunch of piston options. Even in standard bore, J+E pistons are availabe. Rings are tougher story. Some source say chrome, others don;t say.



HAstings makes diametrically close rings for stock bore, and of course, oversized bore fit is easy.



found out that head chamber volume is around 46cc.



However, since finding out chamber volume and using standard rod length:



944 crank 78.9 stroke 2.66L

4.5 mm below deck

0 deck clearance

1mm head gasket

J+E stock flat top pistons with coatings

46 cc chamber

104mm bore



8.22 C/R



stock 968 crank 88mm stroke 3.0L

0mm deck clearance (for ease of calcs)

1mm head gasket

50cc dished J+E pistons

46cc chamber

104.44mm bore



8:14 C/R



So now there is a much more driveable C/R at 8:1-2 as opposed to 7:1, but boost will have to be lower. do I really get higher rpms with shorter stroke, and are there balancing issues, and is there less stress overall???



I think if I balance the 944 crank and pulley, and add balanced sets of pistons and rods, it will work out fine for the de-stroke setup. Common practice is the opposite with standard stroke and dished pistons.....



any thoughts from you guys???

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[xrad]

I think I made up my mind....



944 crank, Mahle stock size pistons and rings, carillo rods. I am not looking for super power with this engine, just about 100 hp more.



not quite happy with my calcs...not sure if the chamber really is 46cc. anyone have a head laying around and can check cc's???

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[biotechee]

Dude-



You lost me as soon as you posted the title! I know nothing, seriously nothing, about how to build one's own turbo system! More power to you and I wish I had the knowledge to do things like this.... Maybe I need to stay at a Holiday Inn Express....



Good luck and I hope you keep us posted on your progress!



Jim

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[xrad]

it's all math right now. If i can;t get an accurate chamber cc's, I will have to wait on the piston/crankshaft selection until I pull the head and measure it myself.

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[saxman]

[quote name='biotechee' post='60463' date='Sep 24 2008, 05:45 PM']You lost me as soon as you posted the title! I know nothing, seriously nothing, about how to build one's own turbo system! More power to you and I wish I had the knowledge to do things like this....[/quote]





http://www.amazon.com/Maximum-Boost-Turboc...8536&sr=8-1

can't recommend this book enough

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[jlm968]

[quote name='saxman' post='60484' date='Sep 24 2008, 11:56 PM']http://www.amazon.com/Maximum-Boost-Turboc...8536&sr=8-1

can't recommend this book enough[/quote]



Per a phone call the other day..."Dude, I already have that book!"

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[Lonestar968]

X, I'm hanging on your every post. Seriously, I'm reading and re-reading everything posted on this thread. What you're doing is what I've been wanting to do for a long time now. Plus, I'm learning alot in the process. With that said... here's a turbo question for you:



Would there be any advantage/disadvantage to running two smaller turbos on our little 4 bangers as opposed to a single larger turbo? <img src="/forum/images/smilies/968/huh.gif" class="smilie" alt="" />

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[94'968]

ya ive always wondered that to. a twin turbocharged 968.... i think its a question of space though. theres barely enough room for one turbo! still a couple of 30mm turbos. that would be sik

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[xrad]

First of all: What is your purpose?



Track...where you plan to stay in the boost range, or road, where you need better low end characteristics.



there would be a slight advantage at the lower rpms using sequential turbos, but try to find the room for that setup....



If your single turbo is set up correctly (right flow characteristics and turbine/compressor wheel housings) ...ANd you have appropriate compression ratio ..say 8.0-8.5:1. you will still have pretty good bottom end power. I remember blowing off the intercooler pipe on a 2.0 turbo a few years ago, and it still moved out from stop OK w/8.5:1 comp. not great power, though.



Teaching point: intercooler is a misnomer. really, it's an aftercooler. an intercooler would be located between two compressors. any type of 'cooler' located before the intake is an aftercooler.



[b]Anybody have a 3.0 head laying around and can you do a chamber volume check??[/b ]



If Lindseys chamber volume number is correct, and I am pretty sure it is, then I actually can have with stock piston tops, normal length rods, and shorty stroke of the 944 crank and have 8.5:1 comp. BUT, No matter how I calculate the chamber volume from porsche numbers, I get about 60-65cc's. I really don't want to pull the head just to measure this.....





Easy cheaper route would be to clean bores, get a new ring set, use stock pistons and carillo rods, and 944 crank.....all depends if I really have 46cc combustion chambers

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[xrad]

a little trimming and welding and all will be well...

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[xrad]

found a throttle body that is an almost perfect fit (besides stock..which I don;t have)



1992 mitsu eclipse 2.0 65mm(ID) TB. 944 mani inlet is 63mm(ID). the holes line up if you use the porsche manifold bolt thread size. Also, the throttle cable setup is nearly perfect. I have already created a GM TPS mount on the opposite side so HAltech hookup will be straight forward. Idle control is possible with this TB, too. or I may just use the 968 idle motor hooked up to HAltech....

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[jlm968]

Lookin' good!

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[xrad]

Thanks. received the clutch cover today. In good shape but needs some cleaning. It is from a 944 S2. should be a direct bolt on but with much more room for exhaust plumbing....

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[xrad]

Parts are finding their way to my doorstep.



Regarding the clutch/bell housing: looks like the late 944, 951 and S2 housing are the same. The 944 flywheel is a little different than S2 flywheel. However, the S2 flywheel is the same as 968 in regards to the stepped sensor blocks and the 968 and S2 use the same flywheel position sensor. These will work with the Haltech.



I decided to go with the 944 S2 steel flywheel for several reasons:



1) it fits the smaller housing

2) they are available

3) being steel, I feel more comfortable with the higher clamping pressure plate forces on the screw threads

4) weight: stock is ~16lbs (from what I can find) this puts it right where I want it weight wise. Some lightened turbo 944 flys are as low as 10lbs and less.

6) there are at least 3 brands of increased clamping pressure plates available (steel) and one aluminum plate (and just as many choices of discs)



or I could go with a late 944 flywheel, have the same options, just have to change the sensor.....



BUT, you can not use the 968 flywheel in the 944 housing (as stated in other posts..and vice versa). This is for several reasons. The flywheel is thicker and holds the ring gear. Different throwout mechanism? and Ring gear is located on the pressure plate for S2 and 951, and 944. So it just won;t fit.



Whay am I not using the stock 968 flywheel and housing. Well, I could. And it has been done before with turbo conversions. But:

1) i want more room for wastegate

2) exhaust not right up against starter

3) the general availability of 944, 951, S2 cltuch parts form many vendors at reasonable rates



BUT remember, if you convert the clutch housing from 968 to 944 style, you will need the longer torque tube from a 951 or S2. As stated above, i was able to locate one with only 29,000 miles on it. There are plenty of these around and you can now get aluminum spacers and bearings for them.



http://cgi.ebay.com/ebaymotors/Porsche-944...emZ170265853684





here is the bell housing rebuild kit:



http://www.lindseyracing.com/mm5/merchant....e=944CLUTCHMISC





Starter: You will have to use a 944/951/s2 starter with the 944/951/S2 bell housing. these are 80$ rebuilt.







So the plan for the clutch setup is S2 flywheel, higher pressure plate and disc (yet to be determined), 944 throwout bearing, bellhousing rebuild kit 944/951

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