My Road Trip Motor Progress
rick m:
Took the chop out tonight for the Last Supper of the 20 year old WOLFSBURG REGISTRY VW CLUB. This is one of the oldest VW clubs in Arizona and it has a long running tradition and has had many great members. Will miss the club but will still have some great and lasting friendships from our association with them.
The chop ran awesome. Smooth, driveable 2275 torque and horsepower...right where I wanted it.
Rick M
Dalland:
I have been following this thread from the start and first of have to say hats of to Rick who has gone against the main stream thinking in the vw community and actually let us bullying him for what he does and believe. ;D
Now a days we are talking much shit about the old hemi style heads, but I think that is mostly because not many people know about those few good things there is with doing the hemi style.
First of, when the hemi style came to America the fuel prices was low and fuel consumption wasn't on anyones mind.
At that time power was everything and to get more power they started pushing the compression higher.
But with higher comp you always get the risk of hotspots and self ignition, and here comes the hemi style into the picture.
When building an engine with the hemi style the bigger bowl will lead to a more balanced air temperature in the chamber so there is less change of self ignition.
So this way they could get higher comp on the same octane, and thereby more power.
Also known is that the good old American engines are low rpm engines and thereby flame speed is not an big issue.
But now a days with the fuel prices and climate changes we care more about the fuel efficiency and also VW engines are small high rpm engines.
This is where the hemi style is rubbish, the hemi style gives a bad concentration of the mixture and so a lower efficiency, also the flame has to travel further, something that is very difficult at higher rpm. So the solution is to introduce squish, this gives a better concentration of the mixture, and much more turbulent air.
That gives a faster flame front, faster explosion, higher efficiency.
But as we see in this thread, not all people is known with the good and bad things in the different designs and thereby judge by what they have heard from other people.
I shouldn't need to say it, but of course there is many more factors that I haven't mention and probably many more that I don't know about. :)
So for a low rpm engine where torque are more interesting than MPG, this may still be a way to go.
I wouldn't do so, but I'm not an American. ;D
rick m:
Dalland....
My motor's rpms will not do much past 5000-5500. However, I knew that going in and that is where I chose a cam design that would work there. Tuche' on your understanding of how the squish and the turbulence work with this chamber design. I have one other advantage...larger valves (intake and exhaust) are allowing more air/fuel at a lower RPM. Ever looked inside a big block Chevy intake/exhaust port and the size of their valves? Guess what? The valves on a 454 and the ports are pretty big but the cams are not. They build truck motors for TORQUE and not drag racing. The idea of making more torque down low is nothing new and it is very drivable power.
I followed the cam advice of a Chevy engineer who suggested smaller overlap and closing the valves sooner. He stated dynamic compression would work with my combustion chambers and the size of the valves and air flow at lower RPM would offset the smaller lift and help make fun, drivable power down low. GUESS WHAT? It worked! Again, am not trying to get into the 100mph club or have an 11 second street car. However, I can tell you that for stop light fun and drivability....this combination has been a lot of fun. It is not a slouch. I just have to shift at a lower RPM to stay in the power band. I do not need killer spring pressures which means less wear and tear on the cam and valve train. I do not need to buzz it to rpms between 5000 and 7500 to feel it pull hard. I just learn to drive it a little differently.
Rick M
Brian Rogers:
Have you driven it enough to get a feeling for fuel mileage ? I'm interested in doing something similare to what you' ve done.
rick m:
Brian....to be honest with you I have been flogging it so much it has not been a good way to determine mileage. I will drive it a little more conservatively and then give you an idea. It is such a fun motor....I guess I have not thought much about the mileage factor. I will be doing some road trips soon and will give you an idea after that measure.
Rick M
Navigation
[0] Message Index
[#] Next page
[*] Previous page