Applying the DV 128 formula on a Supercharged engine

[F-BIRD'88]

Think of it in terms of making big midrange torque vs big peak hp numbers.. On a low cr engine.
A low compression engine also has a low expansion ratio.

[GARY C]

If you want a simple method then just do what Richard Simmons does.... Use an LS cam. They are all blower cams, or so he says.

[F-BIRD'88]

These are not LS engines . These simple blown sbc 23 deg engines put the LS engines on the trailer.. (street stuff)

[Orr89rocz]

Any trend seen on the ls should still apply to other engines

Alot of his stuff shows na cam trends in power curve also show up in boosted applications. Ie power curve Shape is same but just moves up in power cuz of the boost

So yeah maybe tighter lsa’s can be used. My thoughts are depending how much power you are making and how much rpm you are talking about on a street sbc, the 112-114 stuff drives well and tunes easily and no need for tons of bottom end power with boost if you are just gonna over power the tires anyway.

Sure theres probably a correlation you can draw from similar sbc combos for similar sized blower setups using similar exhausts and intakes etc. Do the testing

[SchmidtMotorWorks]

Can you think of a system with hundreds of significant variables that can be simulated by a formula with three variables?
Any system in the world?

Hint,,,there isn't one.

[GARY C]

Any trend seen on the ls should still apply to other engines

Alot of his stuff shows na cam trends in power curve also show up in boosted applications. Ie power curve Shape is same but just moves up in power cuz of the boost

So yeah maybe tighter lsa’s can be used. My thoughts are depending how much power you are making and how much rpm you are talking about on a street sbc, the 112-114 stuff drives well and tunes easily and no need for tons of bottom end power with boost if you are just gonna over power the tires anyway.

Sure theres probably a correlation you can draw from similar sbc combos for similar sized blower setups using similar exhausts and intakes etc. Do the testing

Yes his LS, LSA test seems to follow what one would expect from a cam change but I think short of dyno testing a handful of cams for a given combo your not going to narrow down the perfect cam.

[GARY C]

Can you think of a system with hundreds of significant variables that can be simulated by a formula with three variables?
Any system in the world?

Hint,,,there isn't one.

Apparently cam shafts... Most go off of IVC and work from there, so I guess it doesn't matter where you start as long as you end up with whats needed.

[digger]

Can you think of a system with hundreds of significant variables that can be simulated by a formula with three variables?
Any system in the world?

Hint,,,there isn't one.

it is interesting that i did a study in ENGMOD4T a while back where i took a given engine and simulated various cam lobes and ran them on various LSA from 98 to 114 with no other changes and it showed that irrespective of the cam duration like 270-310 seat-seat the best average power and torque over like a EMC style rpm range 2500-6500/3000-7000 etc wanted the same LSA(i.e. ICL/ECL straight up install no split or asymmetry) regardless of duration. It wanted a much narrower lobe centres than what is normally on offer.

this does not prove nor disprove the 128 theory as normally if you run a cam with more duration you alter runner length, CR and perhaps duct sizes sizes to work optimally so in away the results are prejudiced but it suggests that that for a given combo there is some kind of relationship between phasing of inlet and exhaust processes when you want the system to work over a wide rpm. There are many applications where the rpm range is fairly narrow it probably isnt a useful or relevant . I don't agree that there is an LSA that makes most power everywhere.

obviously when you can vary ICL and ECL separately with VVT the optimum is not going to be one number but it does not preclude there being some kind of relationship between the inlet and exhaust centers with the centres remain static

part of the problem is that unless you are very very specific about the goal there is no such thing as a best cam.

Obviously the cam with best valve events for the application is best but that's just pointing out the obvious

[F-BIRD'88]

Can you think of a system with hundreds of significant variables that can be simulated by a formula with three variables?
Any system in the world?

Hint,,,there isn't one.

E=MC²

[gmrocket]

"ctually doing a lot of testing with crank driven superchargers is away from the traditional 112-114 LSA's and towards 108-110, or to phrase it another way, I see a trend towards increased overlap in blown applications"

In my brief limited experience I have noticed this trend on the street stuff I have done. Noticable difference in usable street car acceleration.

These are low compression ratio engines with relative modest cylinder heads.

Then give us the details on what you’ve done,,,any data ?

What’s the noticeable difference? Any track 60 foot or 1/8 numbers?

[F-BIRD'88]

Can you think of a system with hundreds of significant variables that can be simulated by a formula with three variables?
Any system in the world?

Hint,,,there isn't one.

Apparently cam shafts... Most go off of IVC and work from there, so I guess it doesn't matter where you start as long as you end up with whats needed.

I don't.. I used too. But studying what Harold Berkshire UDHarold shared with us about "when" with regard to valve events and relative pressures in and out on 4 cycle engine I now "start" at a different point.

[F-BIRD'88]

With respect to to what you are asking, no , no hard numbers on this, at the track specifically.
When I do get up there, you and I run at the same track.
Most of what I do is on the street, but the more aggressive stuff gets done at the track. Yes noticable trends in better acceleration performance. I do have a way of measuring...
Admitabily I don't get to the track near enough.

[SchmidtMotorWorks]

Can you think of a system with hundreds of significant variables that can be simulated by a formula with three variables?
Any system in the world?

Hint,,,there isn't one.

E=MC²

Fail^^^

[SchmidtMotorWorks]

Can you think of a system with hundreds of significant variables that can be simulated by a formula with three variables?
Any system in the world?

Hint,,,there isn't one.

it is interesting that i did a study in ENGMOD4T a while back where i took a given engine and simulated various cam lobes and ran them on various LSA from 98 to 114 with no other changes and it showed that irrespective of the cam duration like 270-310 seat-seat the best average power and torque over like a EMC style rpm range 2500-6500/3000-7000 etc wanted the same LSA(i.e. ICL/ECL straight up install no split or asymmetry) regardless of duration. It wanted a much narrower lobe centres than what is normally on offer.

this does not prove nor disprove the 128 theory as normally if you run a cam with more duration you alter runner length, CR and perhaps duct sizes sizes to work optimally so in away the results are prejudiced but it suggests that that for a given combo there is some kind of relationship between phasing of inlet and exhaust processes when you want the system to work over a wide rpm. There are many applications where the rpm range is fairly narrow it probably isnt a useful or relevant . I don't agree that there is an LSA that makes most power everywhere.

obviously when you can vary ICL and ECL separately with VVT the optimum is not going to be one number but it does not preclude there being some kind of relationship between the inlet and exhaust centers with the centres remain static

part of the problem is that unless you are very very specific about the goal there is no such thing as a best cam.

Obviously the cam with best valve events for the application is best but that's just pointing out the obvious

Having the opportunity to make unlimited dyno pulls on a Coyote with programmable cam timing and several exhaust systems and about 100 intake manifold variations, I can say with complete certainty that there is no simple formula that could point out all the local peaks that you can find at various RPM for a single design let alone an engine with many unknown variables.

And as you mentioned about application, the best dyno-tune for power will not be the best driving tune by a long shot.

[RevTheory]

We did one for an 8.5:1 350 with a 2.02 intake valve and 8lbs. of boost a couple of years ago using 128. We simply added 10* (if I remember right) to the opening side of the exhaust so it ended up being a 111 LSA but we left it on a 104 ICL which is probably more akin to a nitrous-style grind. I'd install it closer to straight up if I did it again because the back tires turned into skates.

It's not even in the ballpark of any sort of accurate test; I'm just throwing it out there in case you want to riff off the idea.