Kris H

Hello everyone!

I've been reading this board for a few years already, and I've been bugging some of you by private messages a lot. Since I am at a point of to many technicalities which I am not able to solve myself, the time has come to create a thread about my extremely slow progressing project. I do believe people on this board and your knowledge are uncontested and I hope you'll help me make some good decisions.

My name's Chris and I come from Poland, I am the same model year as my '86 951 I do also have a '91 944s2 for a daily driver. I'm working for the aviation navigation industry and that's probably it as far as short intro is concerned.

First of all, big thanks to all of you who already helped me throughout the years!! Oh my - to many to list, but each and every one of the people I have succesfully contacted helped me a lot. At the same time - sorry for all the silly questions I asked about in the process.

Ok, let's get to the point.

Ta-daaam:





I bought my 951 5 years ago IIRC, and it was my first own car. I've been driving a couple company cars before, but nothing special.. some toyotas, opels, a jeep and whatnot. When I bought my porsche, I was completely out of my mind. Seriously. It has over 300 000 miles on the clock, and it's condition was literally begging to take the car to scrapeyard. I was crazy enough to decide to drive it as-was on a daily basis until i saved enough money to try and slowly build a DE car from it. The engine compression was stock, the engine sounded a bit wrong, but it seemed to "go" well, did not require any oli refills or such, so I went with a simple timing maintenance inspection, and started doing the interior:

I threw away the original ugly dashboard, as it was not only burgundy, which i ehmmm.. dislike, but it was also cut and torn all over (to this day i have not seen worse one (in any car including 924 and other transaxles which are by far more prone to cracking the leatherette), I bought new all-black dash, gearlever panel and door panels, and finally took all the carpets off, as they smelled funny, and were far from acceptable condition, to see this:


Then took it to a friend of mine to (after fair few days of hard labour) transform it to this:




in order to install a simple rolcentre.com rollcage. Then I swapped some new suspension (based on a yellow koni, stiff swayaway bar, stiffer springs and larger stabs), new brakepads, the ventilated zimmerman rotors were in great condition so i left them, and finally changed the stock geometry to something a bit more track oriented (some negative camber etc.)


I was really happy with the results, got used to the noises, and surprisingly still used the stripped DE car, as a DD




until..


one day..


sadly i went off the track on our autoX training damaging my rear quarterpanel..


To fix it, I would probably go to my fellow's bodyshop, but the crash revealed extensive putty everywhere on the panel, which made me wanna swap it for fiberglass instead. I decided to build a steady 3.0L turbo motor and fabricate some GTR bodypanels in order to take the car one step further..
I started to shape the pattern, but due to tight budget changed my mind halfway through, and bought fiberglass stock-shaped elements.





I also have all the windows (except for the windshield) made of Lexan. A friend of mine baked the rear hatch, I made the rest (those are easy, but it's so much fun to do anything for the car by hands). BTW the car is actually so light, I can easily put it by hand on a chair true story



Now to the build: for the same reason and because i was offerred a very cheap, yet good condition 944s long block, I decided to build a 2.5L (or 2.8 stroker) 16v motor instead of the big bore 3l. The goal was to give me solid 350rwhp, with a potential to go further (eventually to 400-450 region i guess).

I bought some goodies:

turbocharger which was supposed to be Holset S40, but I've no idea if it isn't the regular HX40 on B8674M compressor wheel.. (I attach an image of the compressor map i made based on HX40-B8574M Map from the internet and my guesstimates of 16v 2.5 revlines)





VW/audi/Bentley W12 coils:


A standalone engine management unit:


And some other goodies like big oil cooler, 3.8bar fpr, egt sensors, wideband o2 sensor, all the gaskets, rollers, bearings and other obvious build-related stuff..

The bad news were about to come, when we finally opened the 951 block-donor engine. The cylinder bores were very very very badly scratched:


All my hopes were laying in the 944s engine, which' condition was a complete mystery:


I don't want to worry TO MUCH with the chain maintenance, so I'll either want to build it as a non-interference (is it even possible?) or i'd want to go with double cam gear setup similar to the photo below (image found on https://rennlist.com/forums/924-931-...s-mod-2.html):



fortunately the alusil bores in this engine turned out to be good enough:


but then again - bad news were about to come. I took it to a machine shop so that they could restore the alusil to a perfect condition, and they did, however they measured the ovalization of the bore, and it is 0.08.. Seems very high considering the assembly tolerance. For the time being it will have to do though. In the long run, I will build a hybrid stroker based on the 951 block (it'll get sleeved etc, but i don't want to go that route just yet).

The next weeks I'm going to paint the car, and I'm 70% decided to make a "Lowenbrau" color scheme, very similar to what somebody painted on a GTR (wasn't it andial?). Unless one of you guys comes up with a nicer color scheme to paint..


yes, there is a QR under the steering wheel - it's supposed to help me with getting in the car (i'm rather tall and the front of the cage is just disassembled, but it exists)



Ok that was the story behind my project so far, but the problems I have at the moment are:

I think the most reasonable boost for this engine build considering longevity would be somewhat between 1.3-1.6bar (19-23psi) which with my assumption it is not Super40, but a regular HX40 charger, would put me on full boost by 3-3.1k rpm, and keep me in pretty amazing compressor efficiency zone (70%@3500 up to 75%@4100 up to 77%@4600-6000 and then depending on boost, lower or higher but still over 70% till ~7000-7500rpm). I do believe my math here is wrong though, as I have done such calculations for the first time in my life The question is: How wrong am i?

What hotside would you recommend? I guess I'd go for 10cm twin scroll plus we'll fabricate active streaming valve, so that early on whole exhaust volume would blow on a single canal, and after starting to get pressure a valve would open so that both twinscroll pipes would spin the turbine wheel.

What to expect? I don't mean output, but rather longevity..

What clearance would i need to get and how to achieve it in order to make the timing non-interferent?

What compression ratio to go for? At first I wanted to go higher than stock - maybe 9:1, but my engine builder talked me out of that idea, and suggested sticking to 8:1 region.

How to achieve the compression ratio I should go for.. ..on a budget. (keep in mind i will build a proper MID-sleeved short block with all aftermarket internals in the meantime, so i don't want to buy custom pistons etc for the 2.5L build) I'd rather have the stock ones machined and ceracoated or buy a thick copper gasket as an adapter, if the cylinder float and clamping force would be sufficient..

What other while-I-am-at-it things should i not forget to do?



Thanks for all the feedback, and boy I hope somebody will read all of what the noob of me has written..

blown 944

It is the higher flowing hx 40. It would have 8 blades if it were the std unit.

I have the 6 blade pro wheel and yours flows just slightly less than this one. It's a good compressor.

I'd have to get back on here to comment on the other aspects of your build.

Kris H

Nice. Definitely looking forward to your input.

I don't know the exact difference between a 7-blade HX40 and a S40 - all i know is that my serial number is not one of the two numbers you'll find on holset website for super40s.. But it would be nice if it turned out i had the super40 after all. Maybe it's rebuilt to Super40 specs. no idea.

I found three compressor maps for HX40 blowers, and in the calculations I used the one for B8574M compressor wheel, which is the midrange 7-blade one.
The others are indeed for a big 6-blade and smallest 58mm 8-blade comps. So you may be right these are actually for HX, Pro and S40..

BTW - for the guys interested:





Small update - one of my seats and the lexan hatch. I have to respray the frame first before glueing the polycarbonate, so it's bare yet. It's not perfect, but it was hand- and home-made so it's good enough
My inner pedantic spirit will probably switch it to a perfectly shaped one after some time, but I don't care yet

DLS

nice parts
Have you had any experience with the ecu master emu before?
it looks to be a great standalone for the price.
Are you going to run stock trigger (132 teeth or will you run 60-2 trigger) ?

Kris H

Takk!

I have no personal experience with EMU, but a lot of 1st hand opinions, and they are most often positive. Furthermore I have some friends who are experienced in tuning this system which is good.
Plus - it's a domestic product here, with tons of support from the development team, so combined with its capabilities and the pricetag I could not go any other route.

I have no idea which trigger wheel will I use. I don't know neither pros or cons of either.
I think we'll settle that when we'll finally decide on what to apply the timing gears and belt from for the dual camgear setup unless fellow r-listers help me on the subject

BTW - we have some issues with the fiberglass quarterpanels, but they almost fit now, and the car starts to look like a .. car There's still a few small rusty spots here and there to fix, but I can't wait to start painting..
I wonder if we'll manage to properly paint the livery. I have never done anything like that before

333pg333

Great start to an interesting project Chris! You might need to get a 'chopper wheel' at the front of the motor to run that ECU. I might even have one of these lying around somewhere in the shop. http://www.clewett.com/index.php?mai...products_id=30

Keep us posted in your progress.

reno808

keep it up

Kris H

Thanks guys. Patrick - thanks for the info I still have some hope we'll be able to use the stock one. BTW I'd definitely prefer to fabricate the wheel instead of buying an aftermarket piece (it hurts me to pay so much money for something as simple as that gear)..

The body currently got the doorsills worked on due some rust "infection" there, as soon as it's finished, i get the car out of the shop and we will start to paint it.

Today I bought my buddy's steering wheel. Used, but completely reupholstered, so it's almost as new.. not to mention the price was best deal ever. The only downside of the visit at his place is that I got in love with his Ducatis... again.

333pg333

Most aftermarket ECU's have an issue with running off the stock crank sensor and have to compromise with a front wheel. If you find that you have to go down that path let me know and I'll see if I can find that wheel in the shop.

Kris H

Sure, I will let you know, thanks Patrick.

rluciano

Well, since no one else has weighed in on your compression ratio question I will

In my 3 liter (968 block and crank, Carillo rods and customMahle pistons) I have 8.7:1 compression ratio and I am very happy with it. I run 1 bar of boost on pump gas and 1.5 bar on race gas. No problems.

Raceboy

With good engine management I would not go below 9.0:1 on street-driven 2.5 or 3.0 16v.

Regarding stock crank trigger, most of good ECU's cope with the 951 stock trigger without any issues and it is quite accurate.

Kris H

Big thanks guys for sharing the info.

To clarify - I would love to use E85, unfortunately it is no longer sold in Poland, so I'm deemed to tune the engine for pump gas of octane rating RON98/AKI93 which is the "premium" fuel available all over the country.

Dutch944

You could go with VEMS, it accepts the 133tooth starter wheel!

Kris H

Bas, the computer is already here next to me, yet thanks anyway - the tip can be very valuable for other people who read this.