Max rpm our 7.3's can effectively turn

[under pressure]

I'm confused on why the 7.3 is so much more different than any other motor produced?

Why can you take a 12v cummins that spins 2100rpms from the factory and spin 4-5k rpms w/ a simple GSK and springs.

Why can I take my 4k rpm 1.9tdi and make it spin 6k rpms with ease?

Why can a 6.0 powerstroke spin 4k-4500rpms w/ ease...

yet we cant give a straight answer on how many rpm's can spin? I realize that injection methods have a large part in this... but that cant be the ONLY reason why a 7.3 cant spin rpm's like the other motors?

Not trying to be dooshy, I just dont think I'm really getting my question out there properly.

So because you turn them that fast doesnt mean your making any more power there.
The 7.3 crank is huge and heavy, the stroke is long, there for rpms are short.
We can make the same power as others at 2700 rpm where others need 3500+ rpm.

My HP buddies cummins 12v makes all of its 450 hp at 2200 rpm. It stops pulling at 3000.

 

[Meniacal_Mark]

I'm out......

Hey now, I like reading your posts, you're straight and to the point.

 

[Hotrodtractor]

poor assembly...clearances not measured.

he had too little piston to valve (head, LOL!) clearance...too much piston protrusion...

probably used standard deck height pistons, and the machine shop took too much off the block, without addressing the piston protrusion...

could be a goofy combination of rod length, std height pistons, block surfacing...but at the end of the day...the pistons plain and simple...stuck 'up' too far...

about 40thou too far at least.

The piston protrusion on that engine was all over the place - but it mostly fell into the 0.035-0.040" range. I found an old email that had the info in it from when I disassembled it. I thought it was a little shorter than that from memory - but either way - it was too much.

 

[85_305]

Because we are trying to give you knowledge and advice that comes from the real world from the consequences of "Just slapping in some GSK and springs" and letting it hit 6K and blah blah blah.

You want to spin RPMs and do it SAFELY - your words not mine. If you just want to spin RPMs - then go have at it with what you have. Enjoy. If you want to do it SAFELY - then comprehend.

So basically the 7.3's have extremely tight tolerances, implying that the other motors, such as the cummins or TDI, must have lower tolerances to allow for the increase in power.

So because you turn them that fast doesnt mean your making any more power there.
The 7.3 crank is huge and heavy, the stroke is long, there for rpms are short.
We can make the same power as others at 2700 rpm where others need 3500+ rpm.

My HP buddies cummins 12v makes all of its 450 hp at 2200 rpm. It stops pulling at 3000.

the big crank and long stroke of the 7.3 makes sense... but in comparison to the 12v 5.9 the 7.3 actually has a short stroke...

Are you saying its beneficial for our 7.3s to make say, 600hp @ 2700 rpms vs 600hp @ 4,000rpms?

 

[Meniacal_Mark]

So basically the 7.3's have extremely tight tolerances, implying that the other motors, such as the cummins or TDI, must have lower tolerances to allow for the increase in power.



the big crank and long stroke of the 7.3 makes sense... but in comparison to the 12v 5.9 the 7.3 actually has a short stroke...

Are you saying its beneficial for our 7.3s to make say, 600hp @ 2700 rpms vs 600hp @ 4,000rpms?

The question is will you make the same torque numbers with that difference in peak hp/rpm?

 

[85_305]

Lower torque #'s with peaks higher in the rpm's keeps blocks intact... how would the torque peak impact overall performance of this setup?

 

[under pressure]

A couple coparisons..
Take your naturally aspirated chevy 350.... Say 375 hp at 4500 rpm.
Now stroke it to 383....... You make 400+ hp at 3800 rpm

Off the php dyno.

6.0. .... 520 hp @ 3300 rpm,
stroke 4.13"
bore 3.74"
7.3.......550 hp @ 2600 rpm,
stroke, 4.18"
bore 4.11"

Cummins12v... Stroke..4.72 and they make peak power even earlir than 7.3

 

[under pressure]

Lower torque #'s with peaks higher in the rpm's keeps blocks intact... how would the torque peak impact overall performance of this setup?

As far as torque goes, you need to move a 7000 lb vehicle, so street use, competition, all depends.....

If you want hp and torque deeper in the rpms, get ya 6.0 i guess.

 

[Arisley]

So I realize that rpm=hp, and hp= a good thing...

But what I'm saying is, the mathematical equation for horsepower is
hp = torque * RPM / 5252

Let me break this down real simple. RPM does not equal HP. Torque time RPM\5252 = HP

On our motors after a certain number of RPM's, (relatively low unless you do a lot of work. All of it very costly) torque goes down as RPM's go up. Therefore as the RPM number gets larger, the Torque number gets smaller, usually smaller enough that the HP number also gets smaller.

It is not as simple as saying RPM's = HP.

 

[under pressure]

I wouldnt be trying to run a certain rpm, just build to a power level, once you no whete your peak power is made, adjust your shifting to stay where the power is.

Tuned truck comparison..
Straight up race of similar hp, stretching out to 4000 will loose you the race is another way to look at it. Your faster putting peak power to the ground in each gear.

Put ur wheels on a dyno and log 1500 to 4000 rpm. Alot of this info will make more since.

 

[bruce]

This thread would be a lot better if everyone besides golfer and hrt would stop postin. They've forgot more than we all know

 

[Nobody Special]

http://kalecoauto.com/index.php?main_page=product_info&cPath=11&products_id=36

 

[under pressure]

Wth....lol

 

[powerstrokenstang]

I have solid lifter inserts and roller rockers can i make peak power at 8k rpm?

 

[Powerstroke Cowboy]

There is a reason that the 7.3l come from the factory limited to 3400 RPMs.

 

[lincolnlocker]

stock valve train. bent the first push rod in the winter driving down the road in a snow storm 1500rpm's... bent 7 more between 2500rpm's and 4000rpm's in the last couple years. .. all 8 pistons are cracked, and most have valve marks/indents in them... didn't even have a clue the pistons where cracked. took it in to the shop for comp 910 springs and had them take the heads off to go through the valves and make sure the valves weren't bent...

 

[Wes Lewis]

Let me break this down real simple. RPM does not equal HP. Torque time RPM\5252 = HP

On our motors after a certain number of RPM's, (relatively low unless you do a lot of work. All of it very costly) torque goes down as RPM's go up. Therefore as the RPM number gets larger, the Torque number gets smaller, usually smaller enough that the HP number also gets smaller.

It is not as simple as saying RPM's = HP.

This.

Ever looked at a torque curve? As Rpms go up it drops off right?

If torque was always a constant number then you'd be right. But it's not. After a certain rpm it drops off faster then the rpm rises. Therefore less horsepower

As for shifting, ever heard of "the perfect shift"?
Lets say your engine makes 400ft_lb of tq, @2000 rpm.
And to makes things easy lets say you drop 500rpm every shift.
The perfect shift would be shifting at exactly 2250rpm, then your rpm would drop to 1750rpm. Doing this through all the gears would be the fastest way to take off. Because your stayin at the peak torque of the engine for as long as possible.

Revving a motor to redline then shifting is not the fastest way to accelerate.

 

[Powerstroke Cowboy]

But it is the HP that get you moving faster... If you keep it in the max torque you will not take off as fast as keeping it in the max HP... Shift where your max HP is... IF you are racing or pulling.. If you shift where the torque is you will never be in the power band.

Torque is the lugging ability of the engine and HP is the acceleration of the engine..


There are no benefits with running high RPMs on a 7.3.. That is unless you have it built for sled pulling.. then RPMs are your friend

 

[lincolnlocker]

But it is the HP that get you moving faster... If you keep it in the max torque you will not take off as fast as keeping it in the max HP... Shift where your max HP is... IF you are racing or pulling.. If you shift where the torque is you will never be in the power band.

Torque is the lugging ability of the engine and HP is the acceleration of the engine..


There are no benefits with running high RPMs on a 7.3.. That is unless you have it built for sled pulling.. then RPMs are your friend

rpm's for pulling, as in wheel speed? the way i learned the concept of tq and hp is tq gets it there hp keeps it there...

for those that need an image of the two together.... solid line is hp and dotted line is tq

live life full throttle

 

[Dieselboy.]

I constanlty ask myself this question as I can change my WOT shift RPM.

Ive talked to Nate on what cc's my injectors flow at ____RPM/PW and realized there is no solid answer one tuner/mechanic can give me to the ideal RPM to shift at.

The best option in my opinion is to strap it to a dyno and see where she falls on her face and tune the shift to that rpm(slightly before)

If there is no power at 3800RPM why run it out that high ? Your truck us stock (mostly) so why the need to turn such a high RPM ? Ford slapped a sticker on the valve cover stating peak HP@____RPM. I believe its 2800.

OP, you are asking a question that has a combo of no right answer or 1,038,482 right answers.