Bringing the Offy into the 21st century

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CamKing
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Bringing the Offy into the 21st century

Post by CamKing »

The Offy is the winningest engine in IndyCar history. It's roots go back to the Miller engine, that won the Indy 500 in the 20's/
The Offy won Indy 500's, in the 30's, 40's, 50's, 60's, and 70's. It qualified for it's last Indy 500 in 1980.
Thru-out most of that time, the best Offy cam designs came from Ed Winfield. My father was good friends with Ed, and when my dad started working designing cams, Ed Winfield made my dad a bunch of masters, for some of his most popular lobe designs.
By the time, I took over, the Offy was no longer a winning race engine, so the only Offy cams we made were for vintage racing, and we were grinding them to the old Ed Winfield profiles.

In all my decades of designing cams, I had never designed a profile for an Offy, until now.
For fun, I wanted to see what a difference it would make, to make a modern version of one of the old Winfield profiles.
I decided to add .025" lobe lift, reduce the seat duration by 4 degrees, reduce .050" by 2 degrees, keep the .300" duration the same, and increase the .400" duration by 10 degrees. This should be much more responsive, and make more power, without incre3asing the RPM.
Here's the part that impressed me.
With what most would call, a much more aggressive cam profile, opening max acceleration was reduced by 38%.
Closing max acceleration was reduced by 44%.
Opening max Jerk was reduced by 52%, and closing max Jerk was reduced by 62%.
The end result is a cam that has much more area under the curve, but much easier on the valvetrain, and requires a lot less spring rate.
offy pick.jpg
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Re: Bringing the Offy into the 21st century

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BTW, the point I was trying to make with this is, there's no reason to ever buy an old, outdated cam design.
I see posts all the time, where people are recommending some antique cam, like the Duntov 30-30, and saying it's better then modern cams, because it'll RPM with less spring pressure, or something along those lines.
What I've shown you above, disproves that fallacy.
With the technology we have today, we can design cams that make more power, are more efficient, and require less spring. A lot of times, we give up the "Less Spring" part, to make more power, but we don't have to.
The post above, proves that. With very little effort, I took a cam design that was decades ahead of it's time, designed by a person that was regarded as the best cam designer of his lifetime, and made a new cam that will out-perform it everywhere, and be much easier on the valvetrain.
I'm nowhere near as smart as Ed Winfield was, but the technology is so much better now, there's no comparison in the end product.
With all the money and time you spend, building an engine, you deserve better then yesterday's technology.
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Keith Morganstein
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Re: Bringing the Offy into the 21st century

Post by Keith Morganstein »

Do you have a graph of the cam motion , old vs new?

I’ve always been a fan of the Miller / Offy Engine. The way I remember things is that the rules were changed to favor the Cosworth DFX and put the Offy out of racing.
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Re: Bringing the Offy into the 21st century

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Keith Morganstein wrote: Fri Jul 12, 2019 9:28 pm Do you have a graph of the cam motion , old vs new?

I’ve always been a fan of the Miller / Offy Engine. The way I remember things is that the rules were changed to favor the Cosworth DFX and put the Offy out of racing.
I don't have an easy way to graph the valve motion for the Winfield cam.

Yes, you are correct. It wasn't the Cosworth that killed the Offy, it was the reduction in boost, and the mandated minimum fuel mileage.
The Cosworth could never make as much power as the Offy. The Offy in qualifying trim, is still the most powerful engine to ever run at Indy.
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Re: Bringing the Offy into the 21st century

Post by MadBill »

Can you approximate how much more power your new cams added Mike? (Or was the only goal Vintage racing durability?)
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Re: Bringing the Offy into the 21st century

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MadBill wrote: Tue Jul 23, 2019 11:12 pm Can you approximate how much more power your new cams added Mike? (Or was the only goal Vintage racing durability?)
It's hard for me to calculate, because the Winfield design is so much different from mine.
I don't know if they will dyno the cams or not. I will find out.
When I designed it, I designed it to make a small increase in power, without increasing the RPM, and to be much smoother on the valvetrain.
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