Carpokes Porsche Forum

My car is a 1986 US spec Turbo that has been standing still since 2018 when it broke down with its 3rd engine due to cylinder wall scoring . I Left the car for a while and long story short more or less the whole front end got stolen before i transported the car car home and started a slow rebuild.

Initial plan was to build another turbo engine with one of my engine blocks i already have. With flanged sleeves and custom JE pistons. I thought it would best to get everything else up and running while slowly building the turbo engine i could drop in an NA engine and enjoy the car sooner. Also i suffered setbacks during covid trying to order JE pistons while they had severely limited their production.
I spent some time in a tiny garage at home and got the front lower end rebuilt with a strange combination of early and late offset components . Suspension i choose was a set of lightly used Gaz gold coil overs. I converted to a mechanical steering setup and Late NA spindles and hubs. Since i no longer had any front brakes i got some cayenne rotors and big reds mounted with some adapters i made. The car got moved to a bigger garage were more serious work could be done more easy.
I bought a "good" used 85 NA engine and that turned out to be a faulty engine luckily it was really cheap and when parted out i got my money back. I was a bit torn but found another 2.5l NA engine but this time a 16v unit. The 16v engine had a lot of work done to it by its previous owner since he had to source a good block and have it rebuilt plus only run a few thousand miles before having sealing issues with the valve cover gasket. New piston rings, New bearings and freshly rebuilt head . And all documented work done to it. He then found a used turbo engine and converted he's NA car to turbo. I picked up this engine and inspected it when i got back home to find out it was indeed in a very good mechanical condition . Leaking oil from everywhere yes but internally very good . I did see the protentional in this engine and while it did start and run with the stock ecu and s2 intake i played around with the thought of converting it to an ITB setup.

This is when i got into talks with Danst Engineering in the UK and not long after i did order their ITB kit.
The last year since getting the ITB has been fixing odds and ends on the rest of the car. New brakes in the back . New brake and clutch lines. New fuel lines and allot of rusted hardware was replaced .Exhaust is for now a 3" SFR catback and custom 3" front section. I am now getting close to the point were i can finally drive this car again .
The new Intake and Fuel setup really cleans up the whole engine bay. 1 vacuum line going to the booster and a nice new plug and play wire harness is going in. Balance shaft delete will be done to further remove parasitic loss from the crank. I had to remove the AOS and oil filler neck as this hits the ITB manifold. Also since there is now no vacuum being pulled into the intake from crank case ventilation i opted to vent the top aos port and camcover with filters. I will eventually install an electric vacuum pump and route it all through a catch tank unless this solution is acceptable.

Next up is changing the timing belt and replacing a few more seals as well as the waterpump before loading it up with a base map and starting it up . Cams have been timed correctly and should be fine .

After getting the car operational i intend to install a set of big cams and dual camgears before once again hitting the dyno.

Hats off to you for the hard work and progress you've made so far. Perseverance!

Nice work. Looking forward to hearing how it runs. What size ITB did you choose?

Thanks guys .

@Thom

I went 50mm after looking at other 4 cyl engines with simmilair head flow .

50mm is too small for 37/7mm S/S2 inlet valves. Calculate the equivalent area of the valves...

It is unclear to me what makes you think these are to small. If anything they may actually be oversized for the application and the goals for this engine.


42mm 304cfm 70Hp 450-600 cc/cyl

45mm 362cfm 83Hp 550-700 cc/cyl

48mm 408cfm 94Hp 650-800 cc/cyl


The is just no way I will be able to outflow a 50mm itb with a stock 300cfm head

As I said calculate the equivalent area of the valves and you will understand. I'm not saying they won't work but they are not the best size.

https://racehead.com.au/designing-perfo ... uld-i-use/

I think i understand what you are trying to say that combining 2x 37mm intake valves gives you a bigger flow capacity than 50mm First hint is air velocity. I am afraid its not quite that simple and you also have to take into consideration the mid end when choosing carbs or ITBs. Sure if the powerband was designed for 9000rpm 60mm ITBs would be beneficial.
2.5l\4=0.625 x 9000 =75√ x0.8 =60

There are a ton of examples and ï will use the popular k20 head for this comparison they use 36mm intake valves and flow about 320 CFM stock @ 28" on Superflow 600 flowbench where the S head flows i believe from memory around 314 stock .
The S2000k flow 400cfm and rev to the moon and with 52mm itbs normally put down 250whp

The k24 is usually paired with a set of 44-52mm ITBs and has been proven to show great gains. Those engines usually spin faster than the poor m44 engine with the stock oiling system.

In my case the more realistic figure is more towards keeping the midrange where the car will probably spend most of its time while still being able to have an improvement in the top end. Remember the 968 had a single 60mm throttle body and made 240hp with the 3l engine. This is a 2.5l engine And if i will probably keep the rev limiter @7k I could change the ITB barrels at a later stage if needed but i think 50mm will be sufficient. They can also be bored out I think almost 4.5mm

My expectations are 180-200rwhp from this engine with this setup and a set of more aggressive cams. Also clear goals for the build has yet to be determined I have to tune it first then drive it and then decide if further development is desired

I only reason in terms of maximum flow. Who cares about mid range with ITBs? BMW drivers perhaps?
... Joking.

I don't think the 968 engine is a reliable engine to extrapolate from because as a compromised street engine with a wide powerband it was never designed to maximise the potential of the head. It would be interesting to measure a 968 intake on the flow bench and check if it flows the 330cfm of the head.

Getting ready to fire up my car done going trough the base map and calibrating the sensors Trigger in sync as shown above. Only now to find out my 044 pump in the back is now broken (probably due to alcohol content in the fuel.) This was a new pump purchased last year as the one before that got stuck as well due to long storage time and I didn't drain the tank. Guess i will have to head out tomorrow and get a pump.

Lesson learned .

So far i am happy with the Motorsports Electronics ECU . The ME221 is easy to setup and configure and has a great manual. The wire loom it came with is good quality with great labels. And to me seeing people paying 1700usd for a wire loom for a 30 year old ECU when you can get a brand new ECU ,injectors and a factory crimped loom for the same price is mind boggling. As far as i can see the only missing connector on it was Knock sensor I will splice in knock sensor before i start tuning- Do think i will change for a modern sensor though. The MAP sensor plug will not be used yet maybe later for barometric correction but i mainly drive close to sea level so we will see. Another issue i had was to find the correct calibration chart for the IAT sensor after manually plotting 5 different charts it shows real temperatures tested with an electric fan oven that can adjust cold and hot on a knob and a handheld thermometer with a probe dangling next to the IAT sensor