pete95zhn

The source I was recalling was Corky Bell...p.79...: " The plenum volume should be a function of engine displacement-in general, 50-70%. "

If there's other sources and opinions, I'm happy to see and read, I'm just planning my own system.

TRP951

I dont know if you checked out this thread but here it is https://rennlist.com/forums/showthre...ight=16v+turbo
the guy who started it has 968 headers cut at the flanges and the 951 crossover flange cut off and v bands put on so they fit together

Markus951

Yes I know this project.. I have taken some ideas for my self from that thread..

But is here anyone who have upgraded the engine breating system..

Double the horsepower double the breathing system because the 4cl 3.0 engine gets really pressurised..

Those stainless steel braided hoses and reservoir tank are for extra breathing right? Intresting is it somehow hooked back into the front of turbocharger what would help to reduce the pressure by sucking it off a little.


Anyway what are the points in our 4cilinder engine what needs pressure relifes most?

1st from stock oil catch tank to the turbo.. with 15mm hose

2nd from the cilinder head to the separate catch tank (as shown on the picture) and from that catch tank to in front of the turbo (vacum)

catch tank size in liters? and hose diameters at least ?

I noticed with my last engine how much it breathed on dyno.. I could see the air puched out from the cach tank. I assume I did use too small cach tank and hose diameters to get that pressure out of the engine..

How many of you have are wenting it straigth to atmosphere?

Markus

Markus951

little update..

I am putting the engine back to the car today, tomorrow.. This is my formula to 16 valve turbopoject:

54 000 km stock 968 engine what I did open up to check the condition - so to say not even the piston rings have been seal totally... you can see that 1/3 of the ring working surface has been broke in (it shines, the other 2/3 half from the rings does not shine). Since everything is as brand new on this engine/block I dicided not to sleeve it and keep as many stock parts as I can.. When I opened up the engine it looked so clean inside that did not had to clean it at all - no burn oil, as I said as brand new..

Con.rods - I got an engine with cast con.rods - and i find it really hard to belive that PORSCHE ever put those into the powerfull car like 968.. Anyway I replaced the con.rods with genuine porsche 951 items (103.4 RARST units) 951 con.rods where 120 gramms heavier then the 968 units.. and ALOT beefier.. -

Pistons -where cleaned and checked - after cleaning pistons and con.rods with dedication everything went into balance with 0,1gram accurancy.. My 93.8 yearmodel 968 had forged pistons in stock.. I measured the dome area and my impression is that you should NOT modify them to get lower compress ratio due to the fac that rings are too close dome + the thickness of dome area is something like 8mm only.. So yes.... I am keeping the stock 968 forged pistons!

All the piston/rod combos from cilinder 1-4 where exacly the same weight before installing them to the engine..

Head studs - So far i am keeping the stock units, as I am planning to run 1.1-1,2 bar over - If it does not hold together I will change them since its not so big of deal to remove head!

Head gasket - Custom cometic unit with 3.2mm thickness. My calculations show that this should bring down the static compress ratio from 11:1 to 9.5:1 using stock pistons. Witch is perfect for low boost application what i am running.

Cilinder head : Stock, not ported, stock valves etc.. I had it cleaned and checked and valves cutted. Valve springs I did change.. They are too weak IMO and did not cost that much.. I used WV GOLF 8 valve crane aftermarket valve springs withc are exactly the same diameter but 2mm shorter then stock ones.. To compensate that -2mm I did made cusom washers into the lower end of the sping seat. I did use stock retainers. New spirngs are + 20% stiffer then stock ones when pressed to 5mm.. and nearly 45% stiffer when pressed to 11mm (witch is valve lift in stock 968 camshafts)

I am keeping the stock valves since I found it hard to belive that those will brake in first place I am installing EGT probe and I have quite a big turbo and hotside so i doubt my EGT will run sky high and damage the valves..

Exhaust manifold - I am using 968 exhaust manifold and 951 crossover pipe.. I have to say... flanges and angle of 2 manifolds are a bit diferents, so what I did i cutted the flanges in stock 951 exhasut manny and and weld them to right angle etc to stock 968 manifold on the crossover side.. Same goes to the turbo side of the crossover pipe.. I had new flange made and welded to the crossover pipe.. After that everything in exhaust manny got termotaped..

And as promised some photsos

Turbo

Stock 968 piston



Stock 968 Con.rods


951 con.rods.


PT 1000cc low impedence Injectors:


Material and trumpets for intake manny..


Termotaped exhaust manny and cometic MLS custom

333pg333

Looks great Markus. Some of those original components look almost new. I wonder even at 9.5.1 cr if 1.3psi may be too high? What ems are you using to control it all?
Also does anyone have the link to the video or Zoran's car? It was on hear last year sometime I seem to remember.

Markus951

Hey

I am using TATECH 5 fuel management what is able to control variocam, been fully sequential and also I will use coilpacks instead of distributor ignition. From last year I am using 12 trigger ignition so it is pretty accurate.

As far as the stock parts are concerned, yes they look brand new.. interior, seats steering wheel on that 968 where brand new.. the car even smelled new inside! And as it had driven tiptronic whole 54thousand kilometers it certainly had not been abused at all.. So I think my setup is pretty good..

Variocam I will try out.. i think that extra 12 degrees advance in intake side should improve spoolup and low end torque dramatically.. Drove one naturally aspirated 968 cabrio the other day - it did not feel fast at all.. but maybe something was not working right on that particular vehicle..

I think limitation for the boost in this case will be power this engine will produce.. I think past 550 hp it starts to lift the head off... but will see. - many high hp cars here have this problem and its not boost what is doing this but power

I think it should easily produce somewhat 520 -540 hp wit 1.2-1.3 bar - detonation is not that big of the problem since 968 uses pentroof design burn chamber and 16 valves on head! It would be a problem in 8 valve head but not in 16 valve head!

At the moment Id like to get the car running.. will see - many similar projects out there but all of them are a bit different..

One more thing I forgot to mention is separate exhaust pipe and muffler for wastegate as I am running GT35/40R 0,82AR spoolup is quite essencial here..

Markus

TRP951

nice job markus it seems like a couple of the people who havnt posted in a while have come back with bigger setups

nick_968

Looks and sounds excellent Markus, keep up the good work. I am following your progress closely as I still have my 968 engine complete and with Motec it is easy to switch to 16v with Variocam. If your engine works well I may sell my 8v turbo and do the same as you.....

Markus951

Thanks guy's.

At the moment things look like this that the engine will go into the car tomorrow. I had the valve cover also respraide to bright red. So it looks nice and clean now.

Can someone tell how much you can torque stock head studs.. i know that acc manual it should be 90NM but is that the limitation?

The last project will be now the intake manifold! will see Hopefully It will turn out good and 150mm runners with 50mm diameter and full radius trumpets will work out..

Markus951

Some photos of the process..





thats a phone taken picture, so excuse the quality but IRL it looks really great..

Valve cover..

Painted same colour as brake calipers!


Little extra breathing..



Markus

Duke

Great progress Markus!
I really, really like the approach of this project. I also suspect this engine will surpass many of the more conventional (and more costly) 3 liter engines..

Markus951

Well, thanks Duke.. Will see..

THere has been alot of discussion of general point of building mulitple valve 3.0 liter engines if you can reach the same amount of power with 2.5 liter! I find it interesting and to be honest 16 valve in my case was the most logical approach.. since I had all the parts from my last 2 engines and now the 968 engine what I had to purchase together with the car itself. Also we all know, and what ive learnd with 3 years of owning porsche, how the stock aluminium sleeves are affraid of detonation and heat - here where the main difference will come out from the 2.5 liter vs 3.0 liter, 16 valve

With 3.0 to reach lets say 500 hp.. you have to run:

Less boost..
Have less EGT
Have more efficent engine..
Have better low end torque
16 valve head is not tend to detonate as much as 8 valve head..also its ALOT more efficent..
You can run higher compress ratio (bigger hotside on the turbo, bitgger turbo)
Have better low end because of variable cam timing..



Bottom line is.. same max hp.. more reliable.. more streetable...better low end to match long gearing of stock 951 tranny..

Of course we dont know how reliable it is but I hope really that this year i can do more then 4500 KM..

markus

Markus951

Hey

Some photos from todays situation

fun car and company car!




Intake manifod material


engine bay, as you can see the cooling pipe are on the way for intercooler piping so:


..so I might concider something this, rerouted intercooler piping;



Custom bracket for coilpack:

[IMG]

Inside:


Check out the diameter size of stock runners


When making new intercooler piping what should be avoidaded? 90 degree bends?

Markus

pete95zhn

Yes, every 90 degree bend cuts 2-4% hp. And pipe's ID should be so large that flow's velocity stays below Mach 0.33 .

NZ951

I love you Pete, but i think your mean CFM, not HP

Actually as long as you dont press bend (i.e. Mandrel bend), the loss isnt massive. A 90 degree mandrel bend will flow about 0.6% less than the same length straight pipe.