993 engine case with 3.0 crank, have someone done that before with turbos?

[parts4porsche]

Hello guys!

I had post this thread in the 993 forum, but maybe the correct place is here on the engine rebuilding forum...

I was wondering if someone had experienced to built a 993 engine with 3.0 crankshaft before. Just like the famous 2.8L engine that Henry loves to make, but one step further.

One of my reason to do that is to lower the compression ratio, for turbo. second is to rev more since the rod x stroke ratio is better.

the parts for this engine I have are:
GT3 crank and the 3.0 one
GT3 ti rods MK-1 127.8mm, maybe change to longer 130mm to match the 3.0 crank
102mm JE forged pistons
DC43 cams for turbo
ni-rings on the heads
RX-6 F-1 twin turbos
protomotive headers
custom intake ( I also not decided to ITB or just two throttles one for each bank of 3)
heads port and polished

looking to make 800HP @ 1.2 or 1.4 bar

Iīm open for new ideas and opinions, please post any information regarding this engine project

thanks for looking
Tadashi

[YTNUKLR]

What are you trying to use the engine for?

Yes, the combination will work - you can put a 3.0 crank in a 993 case.

A nice benefit of a turbocharged engine is it makes a lot of torque at relatively low revs - which means you can make quite a lot of power and reduce the stress of high rpm. However, turbocharging a very oversquare engine such as this will alleviate the issues with compression ratio these engines seem to have (compression ratio too low without a turbo).

Putting a short stroke in there will reduce displacement somewhat (3.6L->3.3L, 3.8L->3.45L) although it will improve very high rpm durability.

My feeling is this could make sense if you have maximized all other aspects of the engine for top-rpm usage - 7500-8200rpm. It doesn't quite sound like you have given your spec. list. It is almost there but what you're talking about is a very extreme turbo engine -- getting to 800bhp is possible at a lower rpm but if you can spin it to 8000 (and that is going to be where you actually *USE* the engine)...then you only need to make 525 #-ft. of torque at 8000 rpm, and you will have 800hp. To make 800hp at 7000 rpm, you need to increase bmep, and make 600 #-ft. @ 7000. That means you need even more boost (and everything to support more boost).

On one hand, the engine is going to see greater stress from the increase in thermal and pressure load -- boost, combustion heat, displacement, etc. On the other hand, you can reduce these demands with an increase in rpm range, however, the loads associated with rpm grow much faster, due to the kinetic energy equation for massive objects (KE=0.5mv^2). Also, notice that as you reduce the 'torque' requirement for a high-rpm engine, you are still requiring your configuration support relatively more boost, because you are reducing the displacement!

Given the capacity of a Porsche aluminum motor, I would shuffle-pin the case, use Supertec studs, flame rings and Nickies cylinders, a large oil pump such as a 930 iron unit or GT3 unit, utilize the GT3 crankshaft and impose a 'reasonable' rev limit of about 7500rpm, and set the compression ratio and boost coincidently to make absolutely as much power as possible, while keeping the displacement as large as possible and keeping the revs only as high as necessary. The effort required on an engine such as this justifies the custom pistons in order to make this work.

My 2cents.

[parts4porsche]

thank you for the info.

this engine is street use and some track days.

I will stay with gt3 crank. better make more low end torque than big power on high rpm. The 800hp is a good number, but can be less.

I still not decided with injection to use yet. I have the original TAG tronic 3.8 and AEM universal. the problem with tag is to tune it, I donīt have the program of it. do you know who can help. I found a guy in UK that call oldtronic. he could help, but the price is prohibitive, around $5k just for the program and reset it
thank you
Tadashi