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I would just raise the shift points to 6600 right now. Too bad he let up and did not see it carry. It might be fine up to 7200 as it sits. I would upgrade pushrods as a precaution to 11/32.
I would just raise the shift points to 6600 right now. Too bad he let up and did not see it carry. It might be fine up to 7200 as it sits. I would upgrade pushrods as a precaution to 11/32.
What's the point when peak power drops off at 6300? You can see it on the dyno sheet. If peak power carried on longer then of course.
If we rev it out another 500rpm I bet there will be hardly any torque.
These engines, there are so many variables...
What's the point when peak power drops off at 6300? You can see it on the dyno sheet. If peak power carried on longer then of course.
If we rev it out another 500rpm I bet there will be hardly any torque.
These engines, there are so many variables...
The reason for pulling higher is shift recovery. In drag racing with a 3 speed for instance, you would calculate the RPM the engine falls to when you hit third gear. If this is 4500 for instance, you would plot out your upper shift point to have the most average horsepower over the third gear span.
Below is a visual trying to show it. People always talk about "power under the curve"... Which one below has more power under the curve? Discalimer, these are NOT my dyno's, but I used them when explaining this exact same thing to someone else.
Mathematically, here's how it works out. Engine in the below example peaked at 519/441 at 6850 rpm. Torque peak was ~5300 rpm
MPH...…..RPM...…...Engine Torque......Gear...…...ratio...…...rear gear...…...RWTQ...….Engine HP
80...……..7500...…….~315...…………….second......1.78.. .…….4.11...………..2304...…..449
80...……..5656...…….~420...…………….third...…….1.33... …….4.11...………..2295...…..452
Shifting 700 RPM past peak power, and the upshift was almost break even. Net loss of ten pounds of torque at the rear tires.
Same engine shifted at peak power:
MPH...…..RPM...…...Engine Torque......Gear...…...ratio...…...rear gear...…...RWTQ.....Engine HP
72...……..6800...…….~400...…………….second......1.78.. .…….4.11...………..2962...….519
80...……..5090...…….~440...…………….third...…….1.33... …….4.11...………..2405...….426
Shifting at peak power results in an immediate LOSS of 560 lbs of torque at the tires. So the car in first will accelerate faster from 72-80 in second vs third. You can repeat this exercise for every gear, and it's basically the same. Even though the engine dropped over 70 HP and 80 lbs of torque from 6800 to 7500, the car is still faster in the lower gear due to multiplication
Now, here's how it goes on the street. I lined up against a 530 HP boosted car. From the hit to his shift, we were basically even. When he shifted, I lurched forward, and from there on it was over. I pulled a car length on him almost instantly on his upshift. Then he stayed about a car length behind, maybe lost a little ground, until he upshifted to third and fell another car length or so behind while I stayed in second.
Bottom line, the car makes more power from 6800-7500 RPM than it does from 5000-5600 rpm, so it goes faster, even though it peaked at 6800.
Below is a visual trying to show it. People always talk about "power under the curve"... Which one below has more power under the curve? Discalimer, these are NOT my dyno's, but I used them when explaining this exact same thing to someone else.
Mathematically, here's how it works out. Engine in the below example peaked at 519/441 at 6850 rpm. Torque peak was ~5300 rpm
MPH...…..RPM...…...Engine Torque......Gear...…...ratio...…...rear gear...…...RWTQ...….Engine HP
80...……..7500...…….~315...…………….second......1.78.. .…….4.11...………..2304...…..449
80...……..5656...…….~420...…………….third...…….1.33... …….4.11...………..2295...…..452
Shifting 700 RPM past peak power, and the upshift was almost break even. Net loss of ten pounds of torque at the rear tires.
Same engine shifted at peak power:
MPH...…..RPM...…...Engine Torque......Gear...…...ratio...…...rear gear...…...RWTQ.....Engine HP
72...……..6800...…….~400...…………….second......1.78.. .…….4.11...………..2962...….519
80...……..5090...…….~440...…………….third...…….1.33... …….4.11...………..2405...….426
Shifting at peak power results in an immediate LOSS of 560 lbs of torque at the tires. So the car in first will accelerate faster from 72-80 in second vs third. You can repeat this exercise for every gear, and it's basically the same. Even though the engine dropped over 70 HP and 80 lbs of torque from 6800 to 7500, the car is still faster in the lower gear due to multiplication
Now, here's how it goes on the street. I lined up against a 530 HP boosted car. From the hit to his shift, we were basically even. When he shifted, I lurched forward, and from there on it was over. I pulled a car length on him almost instantly on his upshift. Then he stayed about a car length behind, maybe lost a little ground, until he upshifted to third and fell another car length or so behind while I stayed in second.
Bottom line, the car makes more power from 6800-7500 RPM than it does from 5000-5600 rpm, so it goes faster, even though it peaked at 6800.
Very interesting information.
When my new cam gets installed I will surely request higher shift points.
What would be the appropriate shift points with a larger cam? Surely around 6800rpm or so.
I am also thinking of trying out those FAST mid length runners.
Does anyone know if these would lose low and mid range torque on a stroker motor?
The reason Darth was missed with builds spoke of.....i just imagine higher compression and playin with camming. I know of Darth cam spec' ing abilities. 2 choices in blocks re sleeve or dart very big bore. Know of once he was within 1 degree on a cam by a major cam maker. I pick lobe size and let the Man work.
The reason Darth was missed with builds spoke of.....i just imagine higher compression and playin with camming. I know of Darth cam spec' ing abilities. 2 choices in blocks re sleeve or dart very big bore. Know of once he was within 1 degree on a cam by a major cam maker. I pick lobe size and let the Man work.
He specified me an alternate cam for my build.
It was right on the money in terms of valve events
I would run the dyno out to at lest 7200. Then use your torque curve to do the calcs and figure out your shift points. Very Likely 7000 will be about right.
Mid length might show a slight torque loss on the low end but you will not feel it. How often you got WOT at 1500? You downshift do go WOT.
Great explanation about shift points and recovery. I will add that it works that way for a manual transmission. An auto with a loose converter can throw that off a little bit. My converter only drops 800 rpm on the shift. The theory still applies however.
I would run the dyno out to at lest 7200. Then use your torque curve to do the calcs and figure out your shift points. Very Likely 7000 will be about right.
Mid length might show a slight torque loss on the low end but you will not feel it. How often you got WOT at 1500? You downshift do go WOT.
True.
Will the mid length runner lose and torque in the mid range you think?
Ebay have a special on those runners for 400 posted.
Might be worth getting them.
I wonder if you can mix and match them.
True.
Will the mid length runner lose and torque in the mid range you think?
Ebay have a special on those runners for 400 posted.
Might be worth getting them.
I wonder if you can mix and match them.
Any torque lost above 4000 RPM on a Stroker with appropriate Heads & Cam will
PALE in comparison to the HP gained from 5500-7000+ RPM!
Get the Mid -Lengths, easy enough to switch out and compare.
Couple threads in Dyno section with comparative results on Strokers.
Any torque lost above 4000 RPM on a Stroker with appropriate Heads & Cam will
PALE in comparison to the HP gained from 5500-7000+ RPM!
Get the Mid -Lengths, easy enough to switch out and compare.
Couple threads in Dyno section with comparative results on Strokers.
Can you please give me the links of these threads?
I cannot find them?
I found one post in these forums but that was with LLSR camshaft
03-14-2019, 09:21 AM
