Maximum boost for autocross on stock 1.6
#23
If you dont use torque at the wheels then youwill make 1000ft lb+ in 1st gear on a stock na6 because it has like 150 ft lb, and then thats multiplied by 5 in 1st gear and another time multiplied by 4.3 at the differential.
So you do a pull, find the point where it makes peak torque, and then you use a basic online calulator for hp/torque/rpm, input the rpm it makes the power at and the power and you find the torque.
This is torque at the engine, after driveline losses.
This sheet has both HP and AFR and RPM, but no engine torque shown.
You can see that peak torque is going to be at around 5000rpm because its the top leftest part of the curve, however for safety on your own car pick a few points.
For this example ill use 5000rpm, which looks to be around 300hp.
Using this calculator : HORSEPOWER TO TORQUE CALCULATOR
This is 315ft lb.
If we go to redline and calculate (im using 317hp, 6600rpm) we get 252ft lb, meaning he is leaving 65 ft lb on the table, which would equate to 395rwhp.
So by controlling his boost while carefully monitoring peak torque, he could pick up 50whp peak (about 100 at redline) and a LOT of area under the curve, all the while never exceeding the torque (and therefore piston, rod, crank, clutch and driveline stress) he is already producing.
The above is an NA with a 5 speed I recently tuned, with careful VVT control, timing and boost we have kept torque almost dead flat from onset of boost to redline, but have kept the torque at a safe level of just 240 ft lb odd, and holding this to redline gives us much more HP than most stock engine/5speed safe setups. Go ahead use the calulator and check for yourself what the torque is, and yes the car has been raced at this level a few times now. Also see how the Dyno shows a bit over 1000 ftlb of torque, thats 240x4.3 (the diff ratio).
Dann
Last edited by nitrodann; 03-21-2015 at 12:18 AM.
#29
mkturbo.com
iTrader: (24)
Join Date: May 2006
Location: Charleston SC
Posts: 15,176
Total Cats: 1,680
I autocrossed for several years on my SR20 setup with some stupid tune mistakes and never had an issue. Braineack also ran around 240hp at 15psi or so on his 1.6 and autocrossed with me with no blown motors. A 1.6 and a 2554 will not blow things up if he has a decent tune.
#31
Okay, so by this thread, a 1.6 at around 240 hp is close to the limit of the rods......im running a t28 at 14-16 psi and am around 250-260 WHP and obviously judging by the comments am closer to the limit than i knew.
So moving forward, If my new engine build has suitable rods (949 rings and pistons already) ...what is the next performance step failure point...(motor only)... ???
So moving forward, If my new engine build has suitable rods (949 rings and pistons already) ...what is the next performance step failure point...(motor only)... ???
#32
Senior Member
Thread Starter
iTrader: (3)
Join Date: Oct 2008
Location: Indianapolis
Posts: 610
Total Cats: 12
Okay, so by this thread, a 1.6 at around 240 hp is close to the limit of the rods......im running a t28 at 14-16 psi and am around 250-260 WHP and obviously judging by the comments am closer to the limit than i knew.
So moving forward, If my new engine build has suitable rods (949 rings and pistons already) ...what is the next performance step failure point...(motor only)... ???
So moving forward, If my new engine build has suitable rods (949 rings and pistons already) ...what is the next performance step failure point...(motor only)... ???
#33
Okay, so by this thread, a 1.6 at around 240 hp is close to the limit of the rods......im running a t28 at 14-16 psi and am around 250-260 WHP and obviously judging by the comments am closer to the limit than i knew.
So moving forward, If my new engine build has suitable rods (949 rings and pistons already) ...what is the next performance step failure point...(motor only)... ???
So moving forward, If my new engine build has suitable rods (949 rings and pistons already) ...what is the next performance step failure point...(motor only)... ???
Forget the peak HP. What's the peak torque and the peak rpm.
Below 7500rpm and 250tq? Good to go.
Dann
#37
What I have found however is I am faster with more torque available than I can use over a wider rev range. Throttle response and being able to use rear tires for attitude control with some skill makes the car faster.
When I put in my stock internaled junk yard backup 1.8 motor I believe it makes around 250 ft-lbs with the turbo setup maybe a bit more. haven't bent a rod with it even on large tracks with top speeds ~140mph and a full throttle RPM sweep in top gear however. Ring and cylinder wall wear seem to be the worst thing that happens pushing a stock motor that hard with good tuning. I broke a valve once however on the backup motor.
#39
I think I have made it pretty good by having excessive amounts of torque and tailoring gearing to my torque curve aimed at autocross. At 4000 rpm and above there is no response lag and there is enough torque that the right pedal is an instant attitude control device rather than just a go pedal.