Compression/boost/piston design - turbo 2.5 16v
02-06-2009, 05:41 AM
#46
Rennlist Member
+7psi = 200whp? In a game of Poker I'd call. 
That's if you're referring to the 800 as whp lol
I don't disagree with some of your points and can't see why Lorax shouldn't continue either. Sometimes though there might be some advice worth taking on board that might save him some time and money in the long run.
btw there are still plenty of us doing some decent builds that will comfortably be able to utilise a 4" exhaust.
That's if you're referring to the 800 as whp lolI don't disagree with some of your points and can't see why Lorax shouldn't continue either. Sometimes though there might be some advice worth taking on board that might save him some time and money in the long run.
btw there are still plenty of us doing some decent builds that will comfortably be able to utilise a 4" exhaust.
02-06-2009, 06:56 AM
#47
Nordschleife Master
The stock 2.5l 16v engine (944S) made top HP at a low 6000 rpm and rpm limit was set to 6840 rpm.
Set let's not get ahead of ourselves and consider the 2.5lv 16v engine to be a Honda S2000 equivalent!
For Lorax I would say that run the stock 951 pistons with valve reliefs cut out for the 16v head. The quench area is different because the valve locations and head combustion chamber is different so it probably won't be optimal. But hey, everything doesn't have to be optimal. To be honest, hardly anyone of us can afford to build an all out optimal 944 turbo engine. There's hundreds of things that isn't optimal on a stock 944 turbo engine...
If you're interested in performance and like to run your engine in the interval of say 4000-6800 rpm I cannot see any reason not to change to a 16v head if you have the chance.
Oh and I would guess my engine (Markus' old engine) produced about 650-690 crank hp and around 700-750 nm at 1.8 bar.
Set let's not get ahead of ourselves and consider the 2.5lv 16v engine to be a Honda S2000 equivalent!
For Lorax I would say that run the stock 951 pistons with valve reliefs cut out for the 16v head. The quench area is different because the valve locations and head combustion chamber is different so it probably won't be optimal. But hey, everything doesn't have to be optimal. To be honest, hardly anyone of us can afford to build an all out optimal 944 turbo engine. There's hundreds of things that isn't optimal on a stock 944 turbo engine...
If you're interested in performance and like to run your engine in the interval of say 4000-6800 rpm I cannot see any reason not to change to a 16v head if you have the chance.
Oh and I would guess my engine (Markus' old engine) produced about 650-690 crank hp and around 700-750 nm at 1.8 bar.
02-06-2009, 08:00 AM
#48
Three Wheelin'
I was referring crank hp. And as GT3582R doesn't run out of puff at that boost pressure (1.8bar), it ceratainly was at it's limits with that kind of flow. I still think that 0.5bars more than previously results around 170-180 more crank hp with this engine combo.
02-06-2009, 08:34 AM
#49
Nordschleife Master
570 / 2.3 (boost + atm) = 248 hp.
248 x 2.8 (higher pressure + atm) = 695 crank hp all things equal.
But ignition would need to be retarded at 1.8 vs 1.3 bar plus higher intake temps due to the higher pressure ratio.
So I would say around 100 more crank hp for 0.5 bar extra pressure to be on the safe side.
02-06-2009, 11:18 AM
#50
Race Car
Staying out of this, but can anyone answer the question absolutely, do they have to be flycut??
My assumption is yes. Not that big of a deal though.
If I were closer to this point I would just check it, I'm not, but would like to know
My assumption is yes. Not that big of a deal though.
If I were closer to this point I would just check it, I'm not, but would like to know
02-06-2009, 11:58 AM
#51
The Impaler
Rennlist Member
Rennlist Member
Thread Starter
Thanks for your response...
There is always someway you can do things "Better" or more correctly... There is ALWAYS someway to spend more money on a build!
At some point, you just have to put a line in the sand and decide how you want to do it, otherwise will probably just end up throwing tons of money at the car for no good reason.
Please keep me updated on your build!
There is always someway you can do things "Better" or more correctly... There is ALWAYS someway to spend more money on a build!
At some point, you just have to put a line in the sand and decide how you want to do it, otherwise will probably just end up throwing tons of money at the car for no good reason.
Please keep me updated on your build!
Thanks,
What I'm trying to say that this board needs more innovation and less nay'saying. In some aspects it's too commercialized (buy those things from this sponsor) but it's just my opinion, nothing else. Who needs 4" exaust on 951 (no pun intended on the vendor), really? There are less than handful of guys who are running this kind of power. Just an example.
Markus engine's limit was around 1.5bar (educated guess) and 1.8bar with 16v head means serious cylinder pressures. They don't even compare to 8v head cylinder pressures at the same boost pressure ratio.
Care to guess how much hp/tq Duke made with 1.8bar? My bet would be around 800/1000Nm.
Just a thought, maybe a bit trivial, but still: think outside of the box.
What I'm trying to say that this board needs more innovation and less nay'saying. In some aspects it's too commercialized (buy those things from this sponsor) but it's just my opinion, nothing else. Who needs 4" exaust on 951 (no pun intended on the vendor), really? There are less than handful of guys who are running this kind of power. Just an example.
Markus engine's limit was around 1.5bar (educated guess) and 1.8bar with 16v head means serious cylinder pressures. They don't even compare to 8v head cylinder pressures at the same boost pressure ratio.
Care to guess how much hp/tq Duke made with 1.8bar? My bet would be around 800/1000Nm.
Just a thought, maybe a bit trivial, but still: think outside of the box.
02-06-2009, 12:12 PM
#52
The Impaler
Rennlist Member
Rennlist Member
Thread Starter
I tried to make the questions as bold as possible.
Lorax, I'm building exactly the same type of engine (951 bottom end+944 S head) and I put the head to the block and rotated it. So far there was no problems but I have yet to try a plastiline to know exaclty where the valves will be (that on stock cams+stock size valves).
Why would one need to up the redline significatly?? With proper sized turbo the powerband will be broad and due to excellent flowing head you can use even bigger turbines and get less backpressure and more power. My plan is to use HX40 with 17cm2 turbine housing and full boost should be around 3400-3500rpm and I'm not planning to rev the engine more than 7000 rpm.
Here's my 2.5liter head (more pics and details here: https://rennlist.com/forums/944-turb...bo-engine.html ) :
