for street car maybe belt supercharged, but for serious performance gotta be turbo's.

quick pix of a lowly 4 cylinder chevy Ecotec,turbo.


over 50 psi boost. after the race they drove to a resturant for supper,pix.

 

count ,after some thought on the cam profile of .050 lift saying not much revelance!

it made sense when N/A engines were in vogue, because not much does happen because port velocity is so low at that point, not counting inertia movement.

but enter forced induction, and manifold pressure is already at 5/10 psi , then for sure .050 lift is an important event, air movement is higher!

what say you?

 

My experience disagrees.
The lower ramp heights of the AJV8 validation tests were carried out on a N/A engine- to a measureable effect. The Fact that GM and other domestic manufacturers changed their nomenclature also speaks volumes.
Its less to do with velocity and more to do with Exhaust residual flowing back into the cylinder due to low lift valve events, and low lift tuning implications. The Gen 2 Hemi (elephant/Legend) when first run in 1965 with mechanical tappets had collosal ramps- like 0.9-1mm tall! And they were slow opening. I'm sure this is to do with the valvetrain and perhaps them being cautious. When I tried to charecterise this engine- if I tried to assume DAMB style cams- the difference in low speed Volumetric Efficiency was HUGE- like 20% VE!




The Aftermarket is all too often stuck in the dark ages. They don't easily move on. Look at the engine masters series- they rip of the fuel injection systems of LS and Gen 3 Hemis and put on carbs and claim that they make more power.

 

Engine Masters is a very good program, and is sometimes amazing!

when 4 valve V8s (Ford) showed up they immediatly banned them, something been known for years .

John Kasse also amazing engine tech,(of course he has some amazing people working for him).

for instance , Roger Penske and his teams, Roger himself hasnt put a hand on a car in many years, but he is a pure magician when it comes to hiring the RIGHT people!

did you ever have the chance to read the book about his 1994 INDY 500 engine,
they banned it before the end of the race,he won anyway by default(sh*t happens).

engine was a simple 2 valve,single cam , push rod V8, but the guys that designed it in secrecy were from a different planet, yeah mostly from UK, course thats a differnt planet also!

if you ever get the book(i cant remember name, damn memory thing), the tech is like no other i have ever seen or heard about, but it worked, 30% more power than anyone else, and it followed the rule book to the letter(almost,LOL).

 

John Kassel is very good! Was that pushrod racing engine engineered in the U.K. An Ilmor? If so, I know it through a friend who worked on it!

 

I admit I know just enough about fluid modeling to ask dumb questions, but your statement here has been bugging me.

What about the cam style has anything to do with VE? Is it just the mass of the system and assumptions about what you can safely get away with for valve accelerations, etc?

Seems like if the timing, ramps and other parameters were the same that VE would be the same irrespective of the actuation type.

Here in the physical world those different valve systems have limitations of course, but from a strictly VE perspective, why does it matter?

 

>but from a strictly VE perspective, why does it matter?
- Remember that VE changes across the rpm range of the engine.

 

In the example I gave, the ramps didn't stay the same and therefore the actual off seat duration changed. If the valve doesn't close exactly as intended for the engine speed (and load) you will get reversion- that is, either exhaust flow back into the cylinder or fresh intake charge reversion back out of the cylinder into the intake manifold. That optimum point of valve closure changed with engine speed (and load- because even a partially closed throttle will cause a delta P that will drive different reversion dynamics.


You asked about the mechanical actuation- which is a different question- this also has an effect, but perhaps not as much. if you compare a pushrod valvetrain with a direct acting valve train, the flank accels can be designed to be much more aggressive on a direct acting system. This will make the valve lift profile more 'square' - or 'filled out', more area under the lift curve. You need to balance this however, as a pushrod system with rocker arm allows a rocker arm ratio or multiplier which can amplify your peak lift. However a pushrod system will often require longer and taller ramps- which will effect the on seat valve duration- which is where we came in

 

Hey Count. Any updates on your projects?

 

I'm using the XJR daily now. I want to get a baseline time before I do anything else while it's almost stock (except for the Torsen). Have found excessive play in the stub shafts out of the diff (all new components) I wonder if the side bearings weren't pressed in enough- will need to address before I take it to the track.

Have been focusing on cosmetic aspects to the Jag- such as the shifter and am trying to access the ECU. Not easy on an AJ27

 

Excellent! Very exciting! Now this is with the original engine still in place, correct? Have you discovered anything new about the project motor? In particular the oiling system

 

At the moment I'll be focusing on subtle performance mods with the current engine and using the M112. Next focus needs to be on building the 70 Challenger- not going to dismantle the Aston engine now!

 

Very cool. Glad things are still moving forward, no matter what the pace.

 

Shows modification effects- Bhp figures pessimistic compared to all the BS forum talk. PCP= Peak Cyl Pressure, EBP = exh back pressure, data is a combination of engine dyno and simulation projections from experience