I finally got around to buying Engine Analzer from Performance Trends and have playing with some BB engine build-ups. This is a standard L-36 block, heads, intake etc. and I have been through several After Market cams and only one very expensive hydraulic roller grind has a slightly wider torque curve then the stock cam. A couple of other things that I have noticed is that the prgram does not predict any change in friction HP with use of a roller cam and that street exhaust systems really limit HP.

My conclusions so far is that Duke was right - there is no magic to after market cams, at least not for street driven machines and street legal exhaust system flow really limits HP. The program also predicts dynamic compression ratios which is useful for predicting engine knock.

I highly recommend this type of software for anyone contemplating engine mods. It has been an eye opener for me so far !
:eek:

 

About ten years ago I had a program like that, but it would also compute quarter mile times based on the car, set up, weather, tires, exhaust, etc. It helped me understand how changing various components affected performance or not, i.e. aluminum heads would not change hp, but quarter time was affected because of the weight difference. If something was too out of wack like a stock exhaust system on a hi perf BB, it would send up red flags to let you know this combo was definitely not compatable and was not recommended. You could change degrees on the cam and see the difference it made. Pretty cool.

 

i have the first engine analyzer i bought it about 10 years ago and i still use it.

 

You are correct about it helping to understand where the limits are. I also use the Performance Trends software.

A couple of years ago, had a friend who was really wondering what went wrong with his setup (54 Studebaker with 400 SBC, headers, Torker intake). After plugging in the numbers/components, we recommended changing from a 2" exhaust to a 2.5". Woke the engine up and dropped over a second off his quarter mile times. I would not of believed it, but I saw it happen with no other changes. And no, the 2" system was not plugged.

Plasticman

 

EA's handling of internal friction is fairly crude. You have a choice of piston and ring design (I use "production design" for cast pistons at tight clearance and "lower friction design" for forged loose clearance SHP pistons), and windage. I use "typical windage" for medium performance engines without windage trays, and "lower windage" for SHP engines with trays. The differences in these choices are not dramatic.

The friction HP computed by the program also includes the front end accessories you include. This and the ability to select exhaust system back pressure and use SAE net atmospheric conditions, gives you a reasonable estimate of the torque curve "as installed."

The Chevrolet engineers and techs who designed and tested those sixties vintage engines knew what they were doing!!!

BTW, valve timing should be the lash point numbers, not SAE J604d - .006" valve lift that DD2000 wants. Lash point timing is very difficult to determine with hydraulic cams and most aftermarket cams use the J604d timing points for "advertised duration". For comparing hydraulic cams, using the .050" lifter rise timing numbers is probably the best way to get an apples to apples comparison.

Duke




[Modified by SWCDuke, 9:23 PM 2/5/2004]

 

I am not an expert and probably have no idea what I am talking about, but I am trying to decide how to rebuild the 327 in my 1965 which is going through a body off. From what I can tell the advantage to a hydraulic roller is the higher lifter acceleration rather than a friction reduction. In fact with the higher spring pressures required for these cams, the power requirement to drive the valve train is probably higher.

The advantage is that due to the higher acceleration the valves open quicker and are effectively open longer for a given duration. An advantage of this is you can hold the exhaust valve closed little longer and still clear the exhaust gases efficiently. On the intake side there is presumably more potential flow.

One of the Crower hydraulic roller cams I am looking at (00466) requires 39 crank degrees to increase the exhaust the lob lift from .050 to .200 while the Duntov cam (GM 3734078) requires 56 crank degrees to do the same thing – not quite 50% longer. The penalty is about an 80% increase in required spring pressure for the Crower cam (say 175lbs to 317lbs open pressure).

Intuition says the roller should be better. Desktop Dyno suggests it is significantly better. Engine analyzer is not as optimistic (I am told - I do not have that software). I may have to build the d&^% thing to find out…

Again, this is just my 2 cents, I am not an expert.

Dave
:cheers:


[Modified by Dave McDufford, 7:18 AM 2/6/2004]


[Modified by Dave McDufford, 8:06 AM 2/6/2004]

 

This makes me curious: What package do you prefer for this kind of armchair analysis?

-Brian

 

DD2000 is the best for the beginner, and is relatively inexpensive. Engine Analyser is more sophisticated and has more useful outputs, but the average enthusiast may not know how to interpret all the output. It also has more flexible input, but, again, requires more data about the engine than the average enthusiast may to be able to measure.

Since I have a fairly extensive background in IC engine research, I find EA to be the best tool, however, depending on how accurate and detailed I want to get on a particular engine, I usually start out with DD2000 to get some "ballpark" feel for a given configuation, then move over to EA to get more granular view.

Last Saturday I spend a day with a friend working on his '88 Fiero 2.8L V-6 to see how much more power we could get within his budget for his next trip to Bonneville. We ended up with a 17 percent increase in peak power by retarding the OE cam 4 degrees, designing a tubular exhaust system, and designing a new airbox for the top of his TPI manifold, which also effectively shortens the runners. We tried an aftermarket cam both straight up and retarded, but it didn't do much, so he saves that dough.

He's a good fabricator, so most of the changes will be his own labor. The 17 percent increase in power should net him a little over 5 percent more speed. He won't be setting any class records, but he went away a happy camper with a good plan and won't end up spending time and money on mods with no payback.

The peak VE, inlet inertia tuning pressure, and exhaust tuning pressure all arrived in the 5000-5500 range, which is exactly where we wanted it with his gearing and tire revs per mile.

This was really and easy one, because, in this one case, the total focus was top end power. For a street high performance engine I concentrate on torque bandwidth, however, it was interesting that the improvement in power appeared to cost little torque until the engine is lugged down to 1500 revs, so the driveability and normal street driving responsiveness should be as good as before.

Duke