Stop Using SAE J607: Why “STD” Dyno Numbers Have No Place in Modern Harley Performance

In an industry built on measurable performance, credibility depends on one thing above all: honest, comparable data.

And that is exactly what is lost the moment SAE J607—commonly labeled “STD”—appears on a dyno sheet.

Let’s be absolutely clear:

SAE J607 is not an alternative standard.
It is not a legacy option.
It is not a different but equal method.

It is an invalid, canceled standard that has no legitimate role in modern engine testing—period.

A Standard That Was Never Meant for This Industry

SAE J607 was created for a completely different world:

• Engines under 50 cubic inches
• Output below 20 horsepower [saemobilus.sae.org]

That’s lawn equipment territory—not modern Harley-Davidson engines producing 100+ horsepower and displacing well over twice that limit.

Even if J607 had never been retired, it would still be technically inappropriate for this application.

But it didn’t just become outdated—it was formally eliminated.

• Canceled: August 25, 1988
• Replaced by SAE J1349 [saemobilus.sae.org]

In engineering, “canceled and replaced” is not ambiguous.
It means the standard is no longer valid for use.

Not discouraged.
Not optional.

Invalid.

The Industry Already Made the Decision—Decades Ago

SAE J1349 exists for one reason: to fix the shortcomings of earlier methods like J607 and establish a single, credible baseline.

It is now:

• The standard used by OEM manufacturers
• The reference point for published horsepower ratings
• The only widely accepted correction method for modern engines

This is not up for debate within engineering disciplines.

So when a shop chooses J607 today, they are not “choosing a different standard.”

They are stepping outside the standard entirely.

What J607 Actually Does: Inflate the Number

There is only one consistent, measurable effect of using J607:

It makes the dyno number bigger.

That’s it.

Its correction assumptions are more favorable:

• Cooler air (60°F vs 77°F)
• Higher pressure
• Perfect, zero-humidity conditions [chevelles.com]

The result:

• Typically 2–4% higher reported horsepower than SAE J1349 [university...otousa.com]

Same engine.
Same dyno pull.
Same day.

Different number.

That difference is not performance—it is math.

Let’s Call It What It Is: Non-Comparable Data

Once J607 is used, the number produced is no longer directly comparable to:

• OEM specifications
• Other reputable dyno shops
• Industry benchmarks
• Any data generated under SAE J1349

That breaks the entire purpose of standardized testing.

And without comparability, a dyno number loses its meaning.

At that point, it stops being data—and becomes presentation.

There Is No Technical Defense for Using J607

Every legitimate engineering justification collapses under scrutiny:

• Accuracy? J1349 is more representative of real-world conditions
• Consistency? J1349 is the universal reference
• Relevance? J607 was never intended for engines this size

That leaves exactly one outcome:

A higher number on the printout.

And that outcome comes at the cost of:

• Transparency
• Comparability
• Credibility

The Reality the Industry Doesn’t Like to Say Out Loud

The continued use of J607 persists for one reason only:

Bigger numbers are easier to sell.

Even when not explicitly stated, the effect is predictable:

• A build appears stronger than it is
• Gains appear larger than they are
• Comparisons skew in favor of the presenter

This works because many customers assume all dyno numbers are measured the same way.

They are not.

And using J607 depends on that misunderstanding.

The Inch Analogy—And Why It Matters

If a shop claimed an inch was now 1.05 inches long, every measurement would suddenly look bigger.

Nothing in reality would change—only the scale.

That is exactly what J607 does to horsepower.

It doesn’t improve the engine.
It changes the ruler.

The Line That Should Not Be Crossed

In any technical field, using a canceled standard to produce more favorable results is not a minor choice.

It is a fundamental break from accepted practice.

And once that line is crossed, the data cannot be considered:

• Equivalent
• Comparable
• Or fully honest in representation

The Only Standard That Matters

There is a simple rule that eliminates all ambiguity:
If it isn’t SAE J1349, it isn’t a valid comparison.
Everything else is, at best, non-standard.

At worst, it is deliberately misleading.

Final Word

This issue is not about preference, tradition, or “how things have always been done.”

It is about whether performance data reflects reality—or distorts it.

SAE J607 was retired nearly four decades ago for good reason.
The engineering world moved on.

Any continued use today doesn’t preserve history—it undermines credibility.

And in a performance industry built on numbers,
credibility is everything.

 

I've always said there are two reasons tuner show numbers in STD

1) they dont know better
2) they know better but count on their customers not being aware.

Pick one. Neither is good.

 

AI spammer

 

Oh. Right. 😬. But I stand by my post.

 

Nothing AI or spam about me. And everything above is backed up by documentation by SAE International. All you have to do is read them for yourself. SAE J607 and SAE J1349.

 

Ok well you get the award for best cut and paste article then...

 

You think, I fed AI the documentation to create an article stating nothing but facts. You seem to have an issue with that. AI just another tool in box, not a be all end all.

 

Well at least you can take it into account when it's shown, but it's conveniently obscured a lot of times. What isn't discussed enough and can really make them fly high is when some make loaded runs, and others don't. There are no magic cams pipes or tuners- it's pretty easy to discern when a shop is being deceptive.

 

"Well at least you can take it into account when it's shown, but it's conveniently obscured a lot of times. What isn't discussed enough and can really make them fly high is when some make loaded runs, and others don't. There are no magic cams pipes or tuners- it's pretty easy to discern when a shop is being deceptive.?
Agreed! There's a lot of noise out there and many times many absolutely deceptive practices come into play other than correction factors!

 

The problem is that people have lost site of the truth. I've been telling people for years that STD is nothing but garbage and everything stated above is completely true. The Game playing has gotten to the point where many so called tuners spend more time trying to find ways to fake the dyno numbers than they do, really doing the job of properly tuning. There are so many ways to trick the dyno it's not funny and they get used more and more these days.