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The VE on any 3L 8V running a fixed amount of cam overlap is never going to be anywhere near as good as on even a bone stock 2JZ-GTE engine.
Considering how my GTX3576R performs, I am pretty confident that the potential additional top end of a GTX3582R is going to be close to insignificant on an 8V engine.
I would offer you one piece of hard earned advice - don't try making a 944 based engine run a 30 psi on the track, maybe for drag racing but not for road courses. Head lift is quite common at high boost due to the limited number of head studs and a 'flexible' head/block.
The unofficial magic number seems to be around 500-600 hp. Above that and the head gasket does not last long unless significant mods are made. A well built 16v 3.0 liter should make that power at 1 bar of boost.
I changed the cam gears because the stock system makes it a pain to adjust cam timing and the intake cam is driven by a chain with a nylon block rubbing on it for tension....not my favorite solution!
I have done 16v 3l with Darton sleeves, alusil and nikasil. all work when done correctly. Also used about all the rod combos you can think of - Carillo, Wossner, Arrows, Moldex, Pauter....all are good. and all stock rods are 30 years old - they have no place in a high performance engine!
The 16v head flows quite well as is, there are some gains with little tweaks but the base starting point is so good its hard to justify huge $ to make major mods. On the other hand the 8v head can be greatly improved with the correct head work and valve mods. Not your home made die grinder stuff - figure about $4k to get it done right.
Originally Posted by samiller
Chris, I know I am late to this conversation by almost two years but I wanted to help you make the point that the GTX35 is to small to run 30psi on 3.0l @ 7000rpm. When you posted the compressor plot and data points you did the calculation incorrectly! 0.00265lbs/liter * Liters/rev * RPM *pressure ratio = lbs/min at sea level (aka dense air). When you do this calculation correctly you will see that the GTX35 is perfectly sized for 10-20psi on 3.0l @ 7000rpm... It gives a little RPM to spare without dropping below the 65% threshold!... However trying to run 30psi on 3.0l @ 7000rpm puts you well outside the usable range of the GTX35. I have shown the 7000rpm flow requirement with an orange line for a 3.0l engine. I crossed out your points which were too low, and the new red point shows where the 30psi point would be for a 3.0l engine... it is clearly out of the range. So Thor was wrong, your plots just didn't help you prove that! This is why your practical experience is dead on correct... the math agrees when you do it right...
Ok now that that is out of the way let me say NICE JOB... You are world class and I am impressed with your build. I would love to know how it turned out... I also have a couple of questions since this is my dream build and I am hoping to do something similar...
1) Why did you choose not to use the factory cam gear setup? What are the binifits of your dual adjustable cam gear setup? And what did it take to achieve? Is it worth the time and money or can you still get 600hp with the factor cam gear variocam setup?
2) Can you discribe the internal engine build? Sleeves, rods, crank, pistons, oversized valves, porting,...?
Up until now I have been a turbo Supra guy but I have been in love with the 944/951/968 porsches all my life, and want to build a serious street car.
Seems like there are a lot of 968 turbo projects popping up...cool!
I have been working on my own for way too long, over the last couple of months I finally made some time for myself and my car projects - so the engine is ready to fire up now!
The shear quantity of custom fabricated parts in this project is ridiculous. I don't want to think about the hours spent making this the way I want it. For example you would think that adding a 951 intercooler to a 968 wouldn't be too bad since its pretty much exposed....nope. Had to cut away a lot of the stock cross bracing and make new sheet metal crossmembers under the intercooler, the intercooler mounts are machine billet aluminum parts, the stock hood latch is right where the intercooler is so more billet aluminum brackets were CNC machined to hold the hood pins (aero latches).
If you want to have fun look through the pics and see how many custom fabbed parts you can find!
Okay, finally got to read it all. Really awesome Chris, though I'm not surprised. BUT, you're using the wrong turbo and both you and Thom are wrong. What you need is a bigger spark on larger trunk monkeys! The more you spark em, the crazier they spool! I had a bunch of trunk monkey compressor maps, but the last two left over monkeys got out of the hood and ate the damn things, so you'll have to trust my real world experience, MY MONKEYS ARE BETTER!
Joe and Chris...rarely spotted birds around these parts for the last few years! Haven't seen CW around here for a while Joe. He's pretty spot on in what he writes above though. There's a few people that have built or are currently building some good 16v turbos. Best two recent examples are Thingo (Rod's) and Duke (Gustaf's) motors. Both with over 600whp. refresh951 (Shawn) is putting together a nice street/track motor currently. I'm not far off with mine too. Few more at it as well.
Joe and Chris...rarely spotted birds around these parts for the last few years! Haven't seen CW around here for a while Joe. He's pretty spot on in what he writes above though. There's a few people that have built or are currently building some good 16v turbos. Best two recent examples are Thingo (Rod's) and Duke (Gustaf's) motors. Both with over 600whp. refresh951 (Shawn) is putting together a nice street/track motor currently. I'm not far off with mine too. Few more at it as well.
Well, Joe is one of the first of them. Hey Joe, is yours back on the road? Did you sort out the tranny thing?
NO not THAT one! The one in your car. Wait not that one either, I mean the mechanical tranny.
11-29-2015, 07:22 AM
If you were a multi millionaire would you still be precious about using a 968 turbo RS as the factory intended ?
I mean the mechanical tranny.