Horse Power

[Cranky]

Russ, would you expect the trap speed to remain very close if one run was made with a hard launch resulting in a good 60’ time and then have quick power shifts down track......... and another was made with a very soft “walk it out” launch and granny shifts down track?

I wouldn’t, but that’s just my gut feeling.
Be fun to have someone do the test.

Supply the car and I'd be more than happy to test! On my old car, if I left at an idle, it ran a 10.69 but leaving at 4500 stall, it would go 10.68 and only a very slight change in MPH....a couple of ticks slower. On the 4 speed car that a buddy and I ran, it was always faster leaving at 6k than say 4 but was always power shifted. Just never thought about shifting it any other way....

 

[PRHeads]

To put a little perspective to the apparent discrepancy between Al’s “expected” power output(what you’d see on the dyno) vs the on track performance........
On a day where Al had his car at the track, one of my customers was also there with his 4 speed equipped car.
Both BB powered with 6bbl induction.

Looking at the speed vs weight....... and I’m assuming Al’s car is about 350lbs heavier....... the numbers indicate a difference in power of about 100hp....... with my customers car showing the higher number.

My estimate for my customers car is that the motor in it would have dynoed at about 550hp, compared to the predicted 600-ish for Al’s.

I guess what I’m saying is........ I don’t see any way there would be 100hp difference between those two motors...... the wrong way ........if you ran them both back to back on an engine dyno......... without there being something mechanically wrong with Al’s motor.

The track results show the motor that should have come out on top at the engine dyno....... is down nearly 100hp to the other one.

My position is....... it’s being lost in the car set-up, the launch, and driving skill.

“If it were me”........ I’d take it to a chassis dyno and see if the numbers make any sense.
No launch technique or shifting prowess needed on the chassis dyno.

 

[Cranky]

Sometimes stuff like this makes me wonder if everything in the car is aligned right. I've seem some bad run out when the bell housing was checked with a dial indicator before. Even a bad pinion angle can rob a good amount of HP.....

 

[PRHeads]

Unfortunately, without dyno numbers....... it’s really just a guessing game.

I know what Al’s motor “should” make(I’ve tested one that was pretty close to his combo)......... and his track numbers don’t even come close to that.

My guess is...... that’s what sparked the original post.

Edit......
Through the years Ive had the opportunity to test several motors taken out of cars where the owners were struggling with the performance of the car.
Sometimes the motors were underachievers(not really making what they “should”), other times the motors weren’t the problem at all.
Then sometimes there was the situation where the motor made what I would have “expected” out of it........ but that number was a fair amount lower than what the owner was told it made.
And occasionally in those cases....... the car is going as fast as it should....... based on what the motor is actually making.

 

[BSB67]

That’s pretty much my take on it as well, only maybe even more detrimental than the loss of “length”, since on the granny shifts you are(can be) slightly decelerating during that time, and you have to overcome that when you’re finally back on the gas.

You know how it is during the in car camera footage...... where the upper body is seen swaying for and aft during the shifts.

Agreed. The definition of a granny shift certainly changes the answer too. I think a good 4 sp operator would consider my shifting granny shifting. If the car noses down, that pretty slow even by my standards.

 

[BSB67]

My position is....... it’s being lost in the car set-up, the launch, and driving skill.

And, the performance of the motor is, at best, the sum of its parts. Often times that is not the case. Sometimes not even close. This is what I observe more often than not, particularly with folks that are not into the technical weeds and don't spend a bunch of time under the hood. Sometimes they seem to loose 50 hp going from the dyno to the car

 

[oldbee]

I'm thinking a lot of people don't know what a power shift really is. Your whole body is trying to break the shifter (heck with the drivetrain)

 

[PRHeads]

I'm thinking a lot of people don't know what a power shift really is. Your whole body is trying to break the shifter (heck with the drivetrain)

I don’t know....... I’ve seen some in car shifting action on video where the drivers are pretty fluid.
Sure, some look like they’re trying to rip the shifter off the trans, but other make it look like they’re driving to the store.
When it’s really done right, you don’t even see anything going on with the car.

 

[BSB67]

When it’s really done right, you don’t even see anything going on with the car.

I know. It's crazy.

 

[Cranky]

I'm thinking a lot of people don't know what a power shift really is. Your whole body is trying to break the shifter (heck with the drivetrain)

I've seen that too and it makes me laugh to see someone trying to yank the shifter out of the car lol....but to me and this is what I grew up with....a power shift is shifting as fast as you can without lifting off the loud pedal IE, shifting with it matted. Quick or speed shifting is doing the same but 'blip' the loud pedal for each shift. If you're good at power shifting, the car should sound like it has an automatic trans in it and one that ain't slipping lol. Speed shifting should sound nearly the same though.

 

[biomedtechguy]

The et might change a full second or more due to the launch

That's good news for me, and what I suspected...
I know both the Roadrunner and GTO have what it takes to cut faster 1320 times, it's getting the launch down and the 60 ft times that is where we are going to find the greatest reduction in ET. I have my HitMaster, and I've ordered a Hydramax hydraulic throwout bearing for the GTO, in anticipation of it working well to get those 2 factors closer to where they should be before I change tires.

 

[oldbee]

I've seen that too and it makes me laugh to see someone trying to yank the shifter out of the car lol....but to me and this is what I grew up with....a power shift is shifting as fast as you can without lifting off the loud pedal IE, shifting with it matted. Quick or speed shifting is doing the same but 'blip' the loud pedal for each shift. If you're good at power shifting, the car should sound like it has an automatic trans in it and one that ain't slipping lol. Speed shifting should sound nearly the same though.

I remember way back when a truck mechanic demonstrated how to downshift(going uphill) in a loaded semi, so you wouldn't lose speed. Usually you blip throttle to to match rpm's to the gear you we're heading for( it is a 1000# trans after all); blipping and such you lose speed right away, just power shift that thing as hard/fast as you can(throttle on floor).Always loved to show new guys that trick, sounded like a TF shifting!

 

[Cranky]

I remember way back when a truck mechanic demonstrated how to downshift(going uphill) in a loaded semi, so you wouldn't lose speed. Usually you blip throttle to to match rpm's to the gear you we're heading for( it is a 1000# trans after all); blipping and such you lose speed right away, just power shift that thing as hard/fast as you can(throttle on floor).Always loved to show new guys that trick, sounded like a TF shifting!

Guess I should have said 'quick lift' of the throttle when speed shifting instead of a quick blip. Never really let totally off on a speed shift but it wasn't matted during the shift as you would do when power shifting. And I wouldn't think you could power shift a big truck trans lol

 

[33 IMP]

The "blip" in the middle of a shift is usually for a double clutch shift, for a trans with no (Or bad) synchros. I have to do that in both directions in my 33s to avoid gear clash. No synchros at all.

 

[Cranky]

The "blip" in the middle of a shift is usually for a double clutch shift, for a trans with no (Or bad) synchros. I have to do that in both directions in my 33s to avoid gear clash. No synchros at all.

Ran a large lathe at work where you had to gear up if you wanted to keep a good finish as the tool got closer to the center of the part on a last cut. Doing that with one of those was usually hit or miss....mostly miss and clash!

 

[oldbee]

Guess I should have said 'quick lift' of the throttle when speed shifting instead of a quick blip. Never really let totally off on a speed shift but it wasn't matted during the shift as you would do when power shifting. And I wouldn't think you could power shift a big truck trans lol

If ur fast enuf, it'll work! Showed it off more than once, I was a stupidviser among true truck techs, but I had automotive creds. Learned from them(much) , they learned from me. Crank, only missed one time!

 

[al383]

As you discovered, it can be a challenge to get a street car with a stick to work well at the track.

No substitute for testing and practice.

It can take a lot of runs to get a combo like that sorted out.

And don’t take this the wrong way...... but that track outing is the poster child for why “the track is my dyno” argument doesn’t really work at all in many cases.

What your motor would make on the dyno has almost zero correlation to what your car ran at the track.

Unprepared manual trans street cars almost always show way way less power from the calculators than what the motors actually make.

Have you seen the videos?

can you send me the link so i can see them

 

[al383]

To me it’s obvious when you watch a car like that.
It’s harder to get the car to a point where you can side step the clutch on the line at around 5k and have that yield a positive result....... one that rivals what a car with an auto and a good converter would put up for a number.
Then, there are 3 shifts to make going down the track....... at high rpm, with a trans that’s often set up less than optimally for power shifting.
And then on top of that, there is a certain amount of skill involved to quickly and efficiently making those 3 shifts....... and it seems that not everyone can do it like Ronnie Sox.

So, the auto car is more or less fool proof.
Stick it in “D” for drag........ mash the throttle and enjoy the ride.

I’m not saying the streeter stick car can’t run the number it “should”...... I’m just saying my observations are that they rarely ever do.

Again, not picking on Al here....... but so far at least, his car falls right into that category(for all 3 of the reasons I mentioned).

Of the runs of his car I’ve seen(and I’m acknowledging there may have been other trips to the track where better results were achieved. I’m basing this off about 1/2 a dozen passes on one day)..... assuming a race weight of around 4000lbs, using the Moroso calculator, the best one I saw shows a number about 150hp lower than 10% off what I’d expect to see for STP power on an engine dyno for his motor combo.

The on track performance is a reflection of the complete package....... not just the engine output.

In this particular application, compared to how the car was being run on the video I saw, there is no doubt in my mind that if you swapped the 4 speed for a nice 727 and a good 9.5” converter the numbers would make it look like the motor picked up 100hp+.

true i'm not the fastest shifter for sure and yes i know a auto trans is faster but i'm keeping the car stock 4 spd.

 

[PRHeads]

true i'm not the fastest shifter for sure and yes i know a auto trans is faster but i'm keeping the car stock 4 spd.

I’m not at all suggesting you put an auto in the car.

I’m just pointing out that there can be(most of the time) more challenges to overcome in getting a 4 speed equipped street car that’s had a healthy amount of added power transplanted into it.......than what you’d typically have to deal with to get the same car to work pretty well at the track if it were utilizing an auto trans.

In most cases, if the trans is functioning 100%, about the only thing you’d normally upgrade with the auto is the converter...... and add some sticky tires.

 

[al383]

I know I have a lot to work on, pinion snubber, shifting etc. after that date me and a friend took off rear and fixed pinion angle hope that helps some this yr. I like to hear all the feed back even if i feel that i'm not doing that car any justice