New engine hp cap rule


Has anyone studied why there is such a variance between East coast and West coast power? I don’t know if we are interpreting the rules differently, dyno’ing differently, or what - but the highest horsepower, most expensive, etc. (yet confirmed legal) motors I’ve encountered in the NE/MA/SE/GL are ~161hp tops. Yet out west it sounds like 161 would be a mid-pack motor? I know that motor building is probably more of an art than I understand, just curious why there is a ~7% disconnect when we’re building to the same rule book.


These motors were rated by the factory to be 168 at the crank. I know manufacturers are sometimes conservative, but how can they put that same amount or more to the wheels, with all the driveline losses?

Was the published amount all that lowball? I know of a KP guy who doesn’t have a lot more than 170 with cams, headers, chips, and offset cam gear, tested on the same Dynojet the SE SpecE30 guys use. I just don’t get it.

They sell the Dynojet, as I understand it, as an essentially repeatable standard. While that may not be good to the last HP, it should preclude the same car generating widely different numbers on a different dyno on a different day, should it not?


[quote=“ctbimmer” post=73606]
They sell the Dynojet, as I understand it, as an essentially repeatable standard. While that may not be good to the last HP, it should preclude the same car generating widely different numbers on a different dyno on a different day, should it not?[/quote]

This is what has me the most worried. The dynojet in Mid-Atlantic has proven problematic for the GTS guys. 10 HP variances, and plenty of sour grapes. I am most concerned about legal cars being unfairly DQ. Shy of totaling the car, nothing ruins a weekend more than an unwarranted DQ.



On a 155 hp motor, I would expect the variance on a Dynojet with PROPER SAE correction and smoothing set to 5 to be less than 5 hp.


As the series director for the PT series in the mid-atlantic region, we have had the same problem with the dyno at the track being inconsistent.

we have also had people dq’d for being one hp over several times…based on my experience, if I could magically dial up a number on my home dyno I would shoot for 155 whp or less on that dyno…anything above that on a bad day could be a dq…

most of the time the track dyno reads low…but it does have its days


Yeah, that’s why I’m surprised the number was so low. I’m all for a HP rule, but 155 seemed very low. I expected a 160 cap before penalties, or close. They talk about the factory rating, but then allow .020 overboring and aftermarket rockers.


And at 20lbs per HP penalty, that equates to about 100 lbs of variance.


After a few races they should be able to find those variances between dyno’s and compensate appropriately.

I think it’s a good rule. But to implement it before nationals is kind of ridiculous. It also seems short-sighted to only have a max horsepower number, and not torque also.


The DynoJet is probably has good repeatability, but temperature, humidity, the tires, and how the car is positioned & strapped down will all affect the results.

Factory engine numbers will usually be slightly conservative, if for no other reason than to account for manufacturing variations. And compared to others a Dynojet’s results are a bit optimistic. I suspect a hysteresis type machine will be a bit more accurate than an inertial, but neither may be as accurate as a water brake engine dyno. Other factors that affect the book numbers are the conditions the numbers are valid for. Whether the engine is fully dressed with accessories and exhaust matters.

It isn’t unusual to find more power by blueprinting an engine a mass production engine. So given a dyno that may be optimistic it isn’t surprising to see numbers that appear to be higher with drive train losses than the book numbers for the engine.


Also one wonders how much power can be had in a new motor vs. one that’s been broken in.


A couple of observations.

First…155 is too low. BMW basically guarantees a minimum of 168hp at the flywheel on any motor that comes off the line. SCCA racers are getting north of 180 with ALL stock internal parts except a .040 overbore, headers, and ECU.

Second…implementation…no other group EVER changes rules in the middle of the season. It just does not happen. If you are going to implement a HP cap, you better have a dyno at every track for free pulls for every SE30 car to prevent DQs. Spend the money to travel/enter, etc. and get a DQ because your dyno reads higher than my dyno would run me right out of the class!

Third…west coast HP numbers seem to be much larger than east coast numbers, and unless the ECU has been reflashed, west coast numbers are bullshit. I’ve built enough motors and made hundreds of dyno pulls to feel extremely comfortable with this statement.


[quote=“cwbaader” post=73617]A couple of observations.

Oh sh!t. I agree with every word of Chuck’s post. :smiley:


[quote=“JustinHoMi” post=73614]
I think it’s a good rule.[/quote]
Not really. The intent is good. The rule is awful.

To enact a rule that is not independently measurable AND repeatable is silly. Let’s measure track width with a bungee cord that we promise we don’t believe will stretch more than 4%.

The implementation is worse than awful.

Nobody has ever whistled a motor. I’ve never seen a valve cover off. To blow past those checks and go to a ‘measurement’ device with this much variance is surprising.


I agree that changing the rule for 2013 nationals is probably a bad idea so close to the event.

However, otherwise the rule is great for the series.

stock crank hp 168, assume 15% driveline loss puts wheel hp in 140’s, not the 150’s…assume some hp for the exhaust and whatever else guys are “legally doing” 155 is reasonable, os the range set by the spec e30 leadership sounds great…anything above 160 sounds fishy to the average guy wanting to enter the series…


i would like to state i left the rising cost world of PT, in order to join spece30 due to the directors’ goal at keeping cost to a reasonable minimum. that’s mindframe drew me in.


I agree with Chuck (and Steve). While I don’t claim to be an expert engine builder, I’ve built enough to believe that the West coast numbers are a measurement error or things done outside of the rules.


"Oh sh!t. I agree with every word of Chuck’s post. "

Hell has truly frozen over!!!


Steve, et al.

I can easily see your point and understand your position. Regardless
if I agree with it or not, I also see why the rule is in place and why
is was generated. People don’t want to show up with a knife at a gun

What I don’t see/understand is why the spirit of the rule is not the
focus of this issue. Carter’s statement about Spec E30 is basically
saying is that the series is about the drivers and the racing, not who
can find the loopholes and create an unfair advantage by way of more
HP and/or TQ. The idea is to take a street car, put some safety gear
in it and go racing. Not to build and spend more on an engine than
the value of the car itself. The rule is there for one reason…to
level the playing field.

That being said, let’s talk about the elephant in the room. Just
about all the racers who don’t spend a huge amount of time and money
on “development” would love to understand how someone has a legal
motor that has 2 more hp at the wheels than a brand new motor does at
the crank. I will say what the others are thinking…“Huh? How the
hell is that done? Where is the traditional 10-15hp that is lost in
the drive train when it is measured at the wheels? I would love to
have that kind of power.” I would sure like to know…so explain it
to everyone. If it is all legal, and I am choosing to believe you at
this point, I think it would help to explain how this is done since
nobody seems to be able to figure that out.

Now you could say “Why would I disclose my advantage?” The answer is
simple, go back to the spirit of the series and understand the idea
that having that kind of HP advantage diverts from that spirit.
Remember, this is suppose to be a driver’s series, not a builder’s
series, and that is why the rules are written in a way to attempt to
take away both real and perceived performance advantages. I get that
every racer wants to have a competitive advantage, but when it comes
by way other than the driver or at it being cost prohibitive to the
masses, that is where the rules are (at it’s core) being broken. So
if you want any kind of change in the rules, or allowance for
Nationals, I would think this would be a great way to make it. Then
you can say, there you have it and anyone can do the same. If it is
all within the rules, perhaps you will be granted your request. But
make sure you don’t limit the explanation to the engine because there
is more to it than that.

You see, all drivers would like to be rewarded when they do well and out drive the other guy. If they have a slightly better line through the corner or are smoother through the corner, even with the same entry and mid-corner speed, they don’t want that to watch the other guy walk away. That being said, I agree with C. Buzz in that I feel most drivers under estimate the value of their set up and what the skill of a great driver is worth. They simply just chalk it up to HP and wonder why their car won’t do that. Well, sometimes it’s the indian, not the arrows. But then again, there is still something to be said for a sharp arrow.

Just my .02


[quote=“Fooshe” post=73625]I will say what the others are thinking…"Huh? How the
hell is that done? Where is the traditional 10-15hp that is lost in
the drive train when it is measured at the wheels? I would love to
have that kind of power."2[/quote]

I am absolutely confident that the manufacturer-rating is a red herring in this argument. That number was selected to avoid lawsuits from some lawyer prick who ended up buying a “bottom 5%” powerplant off the showroom floor.

It is absolutely possible to build an entirely legal 165-170 hp motor. Everything has to be optimized. When I built my 2011 motor, I paid for a damn good 020-over rebuild. I got lucky as all hell. That motor was a beast! Completely legal. And a one-in-a-million motor.

With about 4 events left in the season I had it refreshed after a couple overrevs and for whatever reason it was never the same. Same builder, same stuff bolted to it, same stuff inside it. Still strong, good enough to win the Southeast championship, but not great.

Folks, this is still racing. The most time, talent, money, and luck will determine the front runner. Until you spec a budget…

Just for giggles, take a look back a few years at this dyno discussion. I still think this could work (in spite of Jim’s counter-argument). Dyno everyone who shows up. If someone is a statistical outlier, they get bounced.

Could someone with a legal motor get DQ’d? Yes. Just like the new rule. Show up at a big show with big power and everyone else does? No DQ. This makes the playing field level at the low-buck local level OR the national stage.
IndyJim Wisdom From 2009


I would agree with you Steve in that if the MFG was slighting the number, than this whole HP rating is based on a lie. However, it seems that VERY few people are able to achive numbers that high at the wheels with legal parts. Are they all otimized?..I have no clue, but suspect not. All that being said, I doubt the MFG was off by 32hp on their rating. The entire automotive world would have been all over that. If my math is right, the M20 would have had to put out 200 hp to make 170 at the wheels if you are loosing 15% in the drivetrain. If 10% was lost, that number would be about 190, or so. I just don’t see that kind of delt as being possible on a mass produced engine with thousands of them put out. But then again, stranger things have happened…yes.

But let’s look back to what the spirit of the series is. It’s not to find the most power to be used as an advantage. It allows for a relatively easy and common achived HP number to be the limit and make it more about the driver and his/her ability to work with their car more efficently since the suspension is spec’d.

Even there, you will find those who are so competitive that they MUST slight the rules to their advantage as some have been found to have illegal shocks. They found a way to revalve the shocks without any signs that could be detected from the outside of the assembly. Again, lots of money spent for a false victory.