11-23-2012, 02:36 PM
Now that I finally finished off the Stage 2 SC Kit, I can finally concentrate on my own car. This has been an incredibly long journey, that began 9 years ago when I first got the car. I knew then that I had a long row to hoe, but I was confident that I could end up with what I wanted.
I got there with the suspension and brakes. Interior came together quickly. Creature comforts and features came along well too. What was lacking was power. None of the bolt on components got me near where I wanted to be. I wanted that magic 10lb per horsepower. So, the SC kit was the obvious project. That did very well, but was still short of my mark. Then came Stage 2. Again, very nice, and gobs of torque, but the bragging rights still weren't there. I had surpassed the power of the Turbo S that porsche spent millions on, only to build little more than a dozen. I made the 10lb/hp goal at that point, but felt there was still more on the table.
As a part of developing the kit, I found the limits of the stock engine. The rods were incapable of handling 7lbs of boost, and the intake system was very limited. I ended up bending rods and really buggering things up. Then came the rebuild. Deciding how far to go was a real issue. I could just put it back together, and live with the power levels I had reached, or I could go deeper, and build it up to handle more boost, and thereby get more power.
I still wanted to run on 91 octane fuel, and pass California emissions tests. I still wanted the reliability and drivability of a stock car. This is a tall order, when factoring in that I wanted to hit about 325hp. So, the building began.
In the bottom end, coated bearings were a must. They can't handle the pounding of high revs, even in normally aspirated mode. If you are building up a motor for high revs (over 6k) then this is a must. The rods are also a problem, whether you have the early 1R or the later 2R. The reinforcing they did is not in the area of failure. Higher levels of boost, and higher rpms dictated a better rod. I went with Carrillo. Larger pistons were also chosen to resolve the damage done when the rods bent. The block got a kiss to clean things up, as the higher boost would find any anomalies and blow a head gasket. The rest of the bottom end got a complete balance and blueprinting procedure that ensured that every component was exactly the same.
For the top end, everything needed to open up. The OEM layout cannot flow enough air to make safe boost. Yes, you can cram it in there, but the temps really start to climb, and the efficiency goes way down really fast. So, the head was ported and polished, the valvetrain was changed, the intake was cleaned up, and a few other changes were made, to open up the flow and allow for more boost. I had to be careful though, because if I opened it up too much, the bottom end torque would go away, just like it would normally aspirated. Porsche did a heck of a job on the intake design. It resulted in a very flexible ability to produce torque across a wide band. They gave up some upper end ability, but not that much. It didn't take much clean up to make it flow well enough to make a lot more power, without giving up the low end. The head was also kissed for the same reason as the block.
The results were a disturbingly smooth engine, and a very thirsty one. The larger pistons and slightly higher compression needed more fuel. The opening up of the intake really made it thirsty, but opened the door for more boost too. I had to add almost 10% more fuel than the Stage 2 kit, just to get things even. This resulted in more torque, and much better throttle response, but I did not have nearly enough fuel to feed it with the stock injectors.
Then it came time to start opening things up and seeing what I could get. I was out of injector, so I had to start figuring that out. I looked at the 4 pintle misting type, and sourced one that flowed slightly better than stock, but they actually made things leaner up top, and by a wide margin. Between the valve pattern of the head, and the dead time and spray pattern of the injectors, the motor just wasn't happy. I tried some bigger ones of the same pattern, and got the same results. So, I had some custom injectors made. Bingo.
As soon as I opened up the SC a bit, and let it make a bit more boost, I immediately went past my target of 325 and hit 340, in the first pass. I had not even begun yet to tune things, or even to seek more boost. After a few passes I got things looking a lot better, and ended up with over 350hp! That's more than Porsche managed to do, with their millions of dollars of budget, on the one and only Le Mans prepped Turbo RS.
I went back a couple of days later to clean up the torque curve, and got things a lot better. The car is ridiculously fast now. I picked up a couple of foot pounds, and got a better mixture across the board. Boost is now up to about 7lbs. There is still no intercooler, and no need for one. As a result of modifying the supercharger itself specifically for this setup, intake temps are now DOWN from the Stage 2 kit.
I'm still not done, and am going back on Monday to fiddle with a few things. I expect to pick up another 4 or 5 horsepower, and a few foot pounds of torque. I'm pretty sure it won't be a lot of an increase, but more importantly, what I have planned will lower intake temps further, making it even safer to run. I still have quite a bit of mid-throttle tuning to do, but it's getting pretty close. Really it drives very well, but I can see by the air/fuel meter that I can get a whole lot more part-throttle torque by cleaning it up. Assuming I don't end up having to go to an even larger injector, and I really hope to not have to do that, as the very bottom end of running will be very hard to tune, I expect to be done with all of it by mid next week.
Here are a couple of charts, just to give you an idea of where I am right now. I'll post more charts after I get back on Monday.
Readings are taken at the hubs!!!!
I got there with the suspension and brakes. Interior came together quickly. Creature comforts and features came along well too. What was lacking was power. None of the bolt on components got me near where I wanted to be. I wanted that magic 10lb per horsepower. So, the SC kit was the obvious project. That did very well, but was still short of my mark. Then came Stage 2. Again, very nice, and gobs of torque, but the bragging rights still weren't there. I had surpassed the power of the Turbo S that porsche spent millions on, only to build little more than a dozen. I made the 10lb/hp goal at that point, but felt there was still more on the table.
As a part of developing the kit, I found the limits of the stock engine. The rods were incapable of handling 7lbs of boost, and the intake system was very limited. I ended up bending rods and really buggering things up. Then came the rebuild. Deciding how far to go was a real issue. I could just put it back together, and live with the power levels I had reached, or I could go deeper, and build it up to handle more boost, and thereby get more power.
I still wanted to run on 91 octane fuel, and pass California emissions tests. I still wanted the reliability and drivability of a stock car. This is a tall order, when factoring in that I wanted to hit about 325hp. So, the building began.
In the bottom end, coated bearings were a must. They can't handle the pounding of high revs, even in normally aspirated mode. If you are building up a motor for high revs (over 6k) then this is a must. The rods are also a problem, whether you have the early 1R or the later 2R. The reinforcing they did is not in the area of failure. Higher levels of boost, and higher rpms dictated a better rod. I went with Carrillo. Larger pistons were also chosen to resolve the damage done when the rods bent. The block got a kiss to clean things up, as the higher boost would find any anomalies and blow a head gasket. The rest of the bottom end got a complete balance and blueprinting procedure that ensured that every component was exactly the same.
For the top end, everything needed to open up. The OEM layout cannot flow enough air to make safe boost. Yes, you can cram it in there, but the temps really start to climb, and the efficiency goes way down really fast. So, the head was ported and polished, the valvetrain was changed, the intake was cleaned up, and a few other changes were made, to open up the flow and allow for more boost. I had to be careful though, because if I opened it up too much, the bottom end torque would go away, just like it would normally aspirated. Porsche did a heck of a job on the intake design. It resulted in a very flexible ability to produce torque across a wide band. They gave up some upper end ability, but not that much. It didn't take much clean up to make it flow well enough to make a lot more power, without giving up the low end. The head was also kissed for the same reason as the block.
The results were a disturbingly smooth engine, and a very thirsty one. The larger pistons and slightly higher compression needed more fuel. The opening up of the intake really made it thirsty, but opened the door for more boost too. I had to add almost 10% more fuel than the Stage 2 kit, just to get things even. This resulted in more torque, and much better throttle response, but I did not have nearly enough fuel to feed it with the stock injectors.
Then it came time to start opening things up and seeing what I could get. I was out of injector, so I had to start figuring that out. I looked at the 4 pintle misting type, and sourced one that flowed slightly better than stock, but they actually made things leaner up top, and by a wide margin. Between the valve pattern of the head, and the dead time and spray pattern of the injectors, the motor just wasn't happy. I tried some bigger ones of the same pattern, and got the same results. So, I had some custom injectors made. Bingo.
As soon as I opened up the SC a bit, and let it make a bit more boost, I immediately went past my target of 325 and hit 340, in the first pass. I had not even begun yet to tune things, or even to seek more boost. After a few passes I got things looking a lot better, and ended up with over 350hp! That's more than Porsche managed to do, with their millions of dollars of budget, on the one and only Le Mans prepped Turbo RS.
I went back a couple of days later to clean up the torque curve, and got things a lot better. The car is ridiculously fast now. I picked up a couple of foot pounds, and got a better mixture across the board. Boost is now up to about 7lbs. There is still no intercooler, and no need for one. As a result of modifying the supercharger itself specifically for this setup, intake temps are now DOWN from the Stage 2 kit.
I'm still not done, and am going back on Monday to fiddle with a few things. I expect to pick up another 4 or 5 horsepower, and a few foot pounds of torque. I'm pretty sure it won't be a lot of an increase, but more importantly, what I have planned will lower intake temps further, making it even safer to run. I still have quite a bit of mid-throttle tuning to do, but it's getting pretty close. Really it drives very well, but I can see by the air/fuel meter that I can get a whole lot more part-throttle torque by cleaning it up. Assuming I don't end up having to go to an even larger injector, and I really hope to not have to do that, as the very bottom end of running will be very hard to tune, I expect to be done with all of it by mid next week.
Here are a couple of charts, just to give you an idea of where I am right now. I'll post more charts after I get back on Monday.
Readings are taken at the hubs!!!!
94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com
"It isn't nearly as expensive to do it right as it is to do it wrong."
(This post was last modified: 11-23-2012, 02:37 PM by flash.)
