Cams for Turbocharged Engines

[kce]

If it hasn't been posted already, I thought this was a pretty cool article:

 

http://www.hotrod.com/pitstop/hrdp_1011_cams_for_turbocharged_engines/index.html

[hoov100]

I hate to say it, but that article is fairly useless from a technical stand point.

[TimZ]

I hate to say it, but that article is fairly useless from a technical stand point.

How so? I thought it did a pretty good job of outlining the basics regarding unique aspects of cam design for turbos. Were you expecting it to tell you exactly how to design a cam profile for your engine?

[cygnusx1]

Pretty cool article that should be a sticky here.  Not only about cam selection but about boost, porting, flow, and other commonly asked questions.

[Tony D]

I posted a reply similar to TimZ's when this was posted originally...apparently it was expunged. (?)

[hoov100]

How so? I thought it did a pretty good job of outlining the basics regarding unique aspects of cam design for turbos. Were you expecting it to tell you exactly how to design a cam profile for your engine?

 

Thats the thing, it barely outlined the absolute basics of selecting a cam and constantly quoted a 3'rd party. I know the best cam is one that is custom ground to the motor and conditions the motor is used in, but they could have atleast given more detail into what it takes. /rant. Maybe I am expecting to much from people now days..

[Tony D]

Most people reading those magazines wouldn't get use from the information.

 

There are some technical-driven car mags with really in-depth articles. They cost upwards of 44$US standard delivery for 6 issues a year. Most people who buy hotrod or carcraft aren't in that league of inqusitiveness.

 

Then, there's always a subscription to SAE papers which will give you access to a mind-boggling array of technical papers beyond your wildest dreams.

 

Again, this costs money and provides depth of knowledge most people don't want to hear.

 

If it's that important to know how that stuff interacts, talk to Ron at Isky Racing Cams. He can go on for an hour till your head hurts specifically on the dynamics of the L-Engine Camshaft. Then go on for another hour contrasting that against what a SBC cam is supposed to do, and how the Datsun differs from a BMW OHC which looks amazingly similar but does not use an assymetric profile.

 

And there I go referring you to a third party as well. If the information you want isn't there, THAT'S THE BEST THING TO DO. They have a limited space for editorial content, and for all the people they satiate with in-depth technicalarticles, they alienate the core base of subscribers who are there for glossy photos, semi-hung jugs obscuring the paint job, and technical puffery good for benchracing with the guys over beers at the local car club. If you truly are interested, you will seek out the information. They have given a source. To complain about it won't change it, they didn't need to credit a source, they could have left it with the basics.

 

Anybody wanting to learn about cam dynamics in the L-Engine should simply look up the Racer Brown Articles. The Engineering Basis for what is in them has NOT CHANGED since they were written in the early 70's. They likely are the definitive published piece to be referred to when discussing L-Engine Camshafts. But that's not what that article was, it was technical puffery on camshaft basics for the teenagers out there who wonder what is inside that lump of iron in dad's Impala out back.

 

For those wanting more, there are two good 3rd party sources referenced. If you still have questions after reading Racer Brown, talk to Ron. I can't imagine not understanding or being completely versed on the dynamics after a visit to just those two reference points in regards to an L-Engine Camshaft. You want to learn about SBC's, then there are other places to look... It's all out there. That someone tells you where to look is not a bad thing.

[BLOZ UP]

What I heard once, was that high overlap cams aren't always automatically "bad" for turbo cars. If you have a relativity high flowing turbine, you can start to get wild with overlap and get good results. So this cam guy who worked for some race team said. I can't remember, I was about 18 at the time and just started working for a performance shop. There was only so much new information that I could fit in my little brain.

 

What it boiled down to, was that there are too many variables to always claim that cams are bad for turbo cars. Unless we are talking about OEM turbos.

[roger280zx]

Turbo cam technology has changed considerably in recent years with both the advancement in turbos and the availabilty/affordability of stand alone efi. If you look into both drag and roadrace builders you will see the trend leaning more and more towards more overlap. The overlap can also extend the life of the bearings in theory. Full disclosure: I'm no turbo guru, but this is based on research of guru's. I'll post links if time permits.

[Tony D]

I don't think turbo cam technology has changed at all. Read the Racer Brown articles from 1972 and be amazed at how many people come up with a 'new idea' straight out of those technical papers...published nearly 40 years ago!

 

Physics doesn't change. And engineered cams were always taking physics into account in the design phase!

[roger280zx]

Well you definitly know more than I do. Maybe it took 40 years for the knowledge to transfer to "popular" application. Then maybe I'm totally off base (it wouldn't be the first time!).

[Tony D]

Define 'popular application' Racer Brown cut cams not only for Datsuns but American Iron as well.

 

So many cam manufacturers copy someting done by someone else, they really never DEVELOP the stuff on their own.

 

Talk with Ron Iskendarian and you find their first offering (when Racer Brown was offering Assymetric Cams) was basically a BMW Profile. And to this day many of the 'other' Datsun profiles are out there that retain that original BMW profile!

 

It works, but not as well as what they did in the mid-late 80's after shadow profiling and reverse-engineering the cam!

 

Ron actually kind of laughs when he says "you can profile them today, it's an exact copy of what we offered originally just to be in the marketplace!"

 

Very few innovators, many (too many) immitators. Who is John Galt?

Edited October 22, 2010 by Tony D

[roger280zx]

I digress

[Tony D]

Precisely...

 

What gets me is Ron's honesty: "We just did a BMW Grind to have something to offer. People were happy, but it wasn't right. We learned a lot working with Electromotive. And we incorporated what we learned and did all our cams for Datsuns over based on what we learned! There are still people who want those original grinds, they made power, but the stability wasn't there like the later grinds. It's funny to see our original stuff still being sold, they do make power (shakes head) but what are you going to do (chuckles)..."

 

Paraphrased

"We kinda screwed up just to be in the market. We learned to do it better. We made it right. People ripped us off then, and are still selling that old stuff, even if it isn't right!"

 

What a breath of fresh air.

[Bino_5150]

if you're looking for a custom cam grind to match your engin and setup, you can holla at my buddy Geoff over at Colt Cams. He's a good guy that really knows his stuff, and takes the time to personally answer your questions and explain everything to you, and help you get the best cam grind for your application.