Any given sunday....

[Gareth]

I agree with the theory of mixing fuel but...

Doesn't the injector fire before the valve opens?

Isn't the fuel shot at the back of the valve used to keep the valve temp in check?

Doesn't the fuel vaporize on contact with the valve and port walls?

Doesn't most of the mixing turbulence happen when the valve starts to open, when air speed is at it's highest?

Soooo...

If that's correct, whats the point of speeding up the air past the injector? It seems to be a restriction rather that a benefit, I had a look with my bore scope into the inlet of an alloytech this morning and it doesn't seem to have anything like this design in the inlet tract, infact the injector is shooting right at the back of the valve. The port is narrower near the injector but doesn't get any bigger past it (except in the chamber)

[antus]

I think the answer to that is that there is no 1 single answer. Ecotech is sequential, so most the fuel is meant to go through the valves. I cant comment on how right they got that, but I know the1's enhanced has the end of injection timing tables adde to make it tweakable eg for cam changes.

Fuel vaporise on contact with walls? Some of it. All of it? No. And how much? Depends on engine/air temp.

Turbulance? Probably a trade off with engine RPM.

The trick is to think of it as a whole, know all of these things, and design the package to do what you need.

Unfortunately for us, finding out the original reasons for the design would be hard if not impossible. In general I suspect more thought has gone in to these things than poeple realise, but the only way to verify that is to do our own tests.

Understanding the mesh on the MAF meters is there to smooth the airflow and improve the quality of the air flow readings was a real eye opener for me. I always assumed it was to protect the sensor.

[vlad01]

I always thought the mesh was for forming laminar air flow for consistent readings. I figured that when I saw how wind tunnels are built. They have a wall of drinking straw like tubes to make laminar air flow.

I guess I assumed correctly then.

[vlad01]

here is a mould of EJ25 SOHC which are the torqueier engines of the series.

similar thing going on here. Is specifies inthe SAE paper than this was done to give more low end torque, DOHC version was made with straighter ports and angle between intake and exhaust valves increased to have more direct path for emphasized high rpm performance.

[Holden202T]

you also have to keep in mind with all the engines, while we would all love to have a direct path from the butterfly to the valve tip there a lot of other factors that all go in to make it not so easy to achieve, the way the ecotec runner is compared to previous models probably makes its a better flowing runner, but it still has to contend with coolant passages, head bolts, injector/valve location as well as the spark plug while all fitting into a compact package! ... I have seen first hand inside pre VN buicks, and even VN 304 v's early 308's, they are all effectively the same motor, just gradually refined for better fit and function!

the alloytec is a good example of getting all the best features of past motors and R&D it all together to give a smaller capacity and more powerful motor as a result, I personally believe its only down fall is the heavy ass cars they put it into! (btw im not trying to start an argument on how good alloytecs are or aren't )

[vlad01]

alloytech are fantastic engines by design, like anything new people tend to give it a bad name at the beginning as all new designs are buggy at first.

later alloytech are great, and yes I agree. heavy ass cars do not allowed the potential to be utilized.


for example dropping an ecotec into an early car like VN that produces a very fast car due to great power/weight ratio.

Imagine an alloytech in a light weight vn/vp or similar.

[delcowizzid]

going from a smaller runner in to a bigger area in the bowl behind the valve slows air speed and backs it up behind the valve as it slows down making pressure its nothing to see 5-8psi behind the valve waiting for it to open and dump its load in the cylinder on an n/a engine its the ram effect of the long runner.when i built my flowbench it was easy to see where gains were the ports on buick are made for down low torque at the cost of topend power sharp short turn and the airflow hugged the port floor badly.didnt take much material removal to make the whole port flow pretty evenly.i made a heap of tool to see where air flow was and also bought a digital manometer to measure velocitys in the ports at varying locations.

[Holden202T]

alloytech are fantastic engines by design, like anything new people tend to give it a bad name at the beginning as all new designs are buggy at first.

later alloytech are great, and yes I agree. heavy ass cars do not allowed the potential to be utilized.


for example dropping an ecotec into an early car like VN that produces a very fast car due to great power/weight ratio.

Imagine an alloytech in a light weight vn/vp or similar.

i put almost 300,000kms on alloytec commodores and i can't say a bad thing about them! coupled with the 5 speed auto was a great package!

[immortality]

I think the only mistake GM made was going to the smaller displacement with the Alloytec engines. Not good in a heavy boat like a Commodore.

Missus drove a VE Omega Allotec with 4L60e and wasn't impressed and said she'd rather have here VS ecotec. The 5 and 6 speed transmissions are much better and I think this is where the biggest gains have been made in the last 10 years as the engines don't produce that much more torque (just more power via higher engine RPM's) but because the newer transmissions make much better use of the torque curve overall performance is better.

Just have a look at that comparison of a 3.0 Sidi Vs 3.5 Sidi Commodore around Mt Panorama. The bigger engine achieved better fuel economy simply because the smaller engine lacks the torque to drive a big car up those big hills and has to work much harder. I believe there is a Youtube video about it.

[Holden202T]

yeah there is a definite advantage to more cubes in a heavy car, but there is also a fine line between big enough and too big in the V6 market!