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So while I agree with you Dock that the car continues to "pull" until redline, there is definitely a drop-off in power and torque as is shown in the dyno graphs, and it is quite perceptible if you watch/feel for it.
I don't think there is that much of a drop-off in horsepower above peak torque. On the k16 chart above, peak horsepower happens above 6200 RPM.
My SOTP is pretty good, and there is not a "quite perceptible" decrease in acceleration above 4,500 RPM. I do not red line my Turbo in gears above 2nd, but WOT pulls in 1st and 2nd are "hard" to red line.
I would still like to understand, better, why the 996 has such a short torque plateau. The GT2 graph above is a little better, but the K16 graph is very abrupt.
Curious what you would recommend for a "mild" ~500HP build (e.g., exhaust, IC's, turbos, on stock internals). I don't plan to build the motor, and I don't want to chase the HP dragon.
Would you still recommend something newer/bigger than a K16?
Would you still recommend MAFless tuning?
It sounds like the answer is yes, just wanted to confirm since a lot of guys like me are on milder setups, and don't necessarily plan on ever ending up with a 3.8 or 4.0L.
Anything over 550 hp or so I would do mafless tuning....
Last edited by powdrhound; 12-11-2019 at 02:15 AM.
I don't plan to build the motor, and I don't want to chase the HP dragon.
Have you talked to Kevin?
While budget is always a consideration, I think that it's secondary after first determining what your objective is for the car. Once you decide on your target, then you can see if it makes sense to attain it based on what you want to spend.
As you are aware, modifying car engines can be a black hole. I think for many drivers, any new hp/tq power gains will eventually get "old" as what was fun/fast six months or a year ago becomes slow today as familiarity and exposure deadens some of the sensation.
I see that - I also see your torque plateau is quite flat and longer through the RPM range - so on the dyno plots earlier in this thread, do you have an idea of why the torque peaks abruptly and drops off? I always thought that with two turbos, one could sustain a flat torque delivery over a wider RPM range, more inline with what was shown on the link. Also, I thought there was enough flexibility in programming the Bosch ECU that you could smooth that torque to being absolutely flat in delivery. Very interesting stuff.
While budget is always a consideration, I think that it's secondary after first determining what your objective is for the car. Once you decide on your target, then you can see if it makes sense to attain it based on what you want to spend.
As you are aware, modifying car engines can be a black hole. I think for many drivers, any new hp/tq power gains will eventually get "old" as what was fun/fast six months or a year ago becomes slow today as familiarity and exposure deadens some of the sensation.
Thanks Dock, I have had the pleasure of speaking with Kevin a few times. Always helpful. I agree with the above.
For now (and thanks to advice from Kevin + others here), my plan is to stick with stock K16's and a tune (along with upgraded exhaust, IC's, clutch, 7GT2 1st-3rd gears & steel 3rd-4th synchros). I'm just thinking ahead to the day when my turbos need to be rebuilt, as I like the idea of updating to better technology when that time comes, and the rest of my setup should now support the additional power.
Thanks Dock, I have had the pleasure of speaking with Kevin a few times. Always helpful. I agree with the above.
For now (and thanks to advice from Kevin + others here), my plan is to stick with stock K16's and a tune (along with upgraded exhaust, IC's, clutch, 7GT2 1st-3rd gears & steel 3rd-4th synchros). I'm just thinking ahead to the day when my turbos need to be rebuilt, as I like the idea of updating to better technology when that time comes, and the rest of my setup should now support the additional power.
For now (and thanks to advice from Kevin + others here), my plan is to stick with stock K16's and a tune (along with upgraded exhaust, IC's, clutch, 7GT2 1st-3rd gears & steel 3rd-4th synchros). I'm just thinking ahead to the day when my turbos need to be rebuilt, as I like the idea of updating to better technology when that time comes, and the rest of my setup should now support the additional power.
I personally think that for street driving the limiting factor regarding how much hp/tq one shoots for is traction.
On stock wheel/tire sizes, even with 45 minutes of driving in the twisties today, my Michelin PS2 tires break traction briefly when the boost kicks in during WOT 2nd gear pulls starting at ~3,000 RPM. It is 48 degrees here today, but I have had this happen happen occasionally in both 1st and 2nd gears in the summer too (going up a road with an incline.) While bigger rubber on the back would help, if someone wants to stay with stock tire sizes (like me), and wants to stay reasonably within the speed limit, then something around 500-520 hp/tq at the flywheel is IMO a good upper level target. My Turbo is advertised to be 520'ish in hp/tq.
For those following this thread, you may recall that I've been chasing an overboost and evap leak code since I got the car. I FINALLY got around to doing a proper boost leak test and discovered that rascally #16 check valve was the culprit. I figured if I was going to be in there changing that one, I may as well change the #9 venturi/suction pump valve while I'm at it. Upon inspection, the #21 check valves were still holding up just fine, so I left them for now. I also took the diverter valves apart and gave them a good clean and lube. I also replace the fuel filter while I was in there. I'm finally boost least free and the car drives SO much smoother. I really should have done this months ago.
Speaking of the #9 (shown in the diagram below, part number 99611065270), let's talk about Porsche Tax. This part is currently $43, plus shipping, from Pelican. When I was looking at this part to order a new one, it looked awfully familiar to me. Sure enough, after some sleuthing I was able to determine it is in fact THE EXACT SAME part that Volkswagen/Audi used on the 1.8T engine from the same era, part number 058133753D. Available for $8 on Amazon, with free Prime shipping. It's the same part.
With that handled, I also received my tune loader from Markski and was able to send him a copy of the current file on my car. He found some interesting things in the current tune, namely that there isn't currently a tune on my car at all! This car is running FVD K24s with 1 bar waste gates on a factory file! Aside from the boost leak from the #16 valve, the other source of the overboost code is likely that the car is expecting factory boost levels, but with the 1 bar waste gates, it's getting 1.2 bar. Looking through the documents for the car, the original FVD tune got written over by a shop working on it sometime around 2013 when they were chasing some performance issues with the car. This would explain why I have dyno charts for the car that show it putting down only 400 hp at the wheels.
Now I'm really excited to get the new MAF-less tune on the car.
The car is essentially an X50. From the factory, it had K16s though. The first owner swapped those out for FVD Race K24s (https://www.fvd.net/us-en/FVD123023/...-left-new.html). Kinda old school, but they work and are still in really great condition, so I'm just going to maximize what I can get out of the car in it's current configuration. If I get the itch for even more power, I can always rebuild them into hybrids or something.
Markski says the factory K16 and K24 tunes are nearly identical. I guess the extra power in the X50 mostly comes from the larger turbos, not the tune.
And by "works" I guess the answer is yes, it does run and drive with no CELs (besides the overboost code). I'm really excited to get the new tune on the car though because it's really powerful as-is, so it should be a real hoot with a proper tune on it.
12-10-2019, 03:44 PM
