thoughts on bumping up compression

The bearings were not coated. We were running standard 15w40, but have since changed oils.
 
Hamilton Cams said:
There are some definite positives with upping compression. The down side is that is a totally different school of though on engine design and it requires different settings on timing and a cam that can bleed off a little bit of compression on the bottom end and then continue gain captured intake flow as rpm rises by closing the intake valve more degrees after BDC. I am glad to see so many people finally playing with different compression ratios stroke and rod length. Making cleaner power should be one of our top priorities if diesel is to hit more of a mainstream audience. We are working with quite a few people upping compression ratio and looking for custom cams to compliment them. THis next race season will change a lot of peoples minds on what the "ideal" way to make power is. In a drag race situation there are lot of benefits.

Zach
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Couldn't agree more. Banks has the worlds fastest diesel drag truck and it doesn't produce a molocule of black smoke so why does every other diesel performance vehicle have to?
 
Big Swole said:
I love a good STORIE!!


lol


Just messin with ya Wade!! :)
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Dynamic compression is how much Compression ratio the engine is making while running.

Factors include

Bore
Stroke
Rod length
Static compression
camshaft intake valve closeing ABDC
Boost psi
and even altitude plays a roll here.

Completely explaining this would get quite lengthy and im short on patience.
 
I have no clue what banks is doing. I have heard that they run a good bit of squeeze which definitely helps with smoke control in addition to whatever engine internals they have.

I guess my point which I should have come out and said is that running an intake profile that closes the valve soon after BDC will capture a great deal of air at low rpm, create a lot of cylinder pressure and give great spoolup. THis kind of cam will not do as well above 4k though.

The flip side which I was hinting at is that higher compression ratio will help push the chargers a bit harder and give better spool. In this case you could run a larger intake profile that closes more degrees after BDC. THis would bleed off some of the cylinder pressure at lower rpm. As the piston is on it's upward travel while the intake valve is open, instead of starting to compress at low rpm it will be pushing air back into the runner. High compression would offset this effect and still give great bottom end spool. The benefit comes in that as RPM increases you can not adequately fill the cylinder so the larger intake lobe will in effect be able to capture more air as the rpm increases.

A lot of the pullers run large intake profiles that bleed of a lot of cylinder pressure at low rpm. Combine this type of cam profile with low compression, and it dictates ether be used to help create enough cylinder pressure at low rpm to fire. THese engines hardly run until rpm reaches the point that enough air is trapped to fill the cylinder and enough combustion gasses are present to light the chargers.

This is okay for pullers but not for street use. You can use high compression to either run a larger cam that in effect becomes more efficient as rpm increases or to light a bigger charger that will also run progressively better as rpm raises, but not so well at low rpm that it creates catastrophic cylinder pressures. I guess what I am saying is that if you run high compression, you wouldn't want a small , high torque cam and a 62/12/65. Cylinder pressures down the highway would be crazy. Bleed it off a little with a larger intake profile or run a larger charger so that you would'nt overspeed it by 1900 rpm.

Just some thoughts. Do not mean to disagree or negate what others are saying.

Zach
 
you can change the dynamic compression by different cam designs cant you? is there any valve overlap in diesels, or other forced induction cam designs?
 
chris lang said:
you can change the dynamic compression by different cam designs cant you? is there any valve overlap in diesels, or other forced induction cam designs?
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Of course, and certainly - although it's typically positive only at seat timing... OEM & most aftermarket grinds run from N15*-N34* overlap @ .050".

Blower cams are different than turbo cams - really pretty similiar to NO2 lobes.

Don't forget overlap, duration and even lift numbers don't explain the most important part of actual engine performance - valve event timing is the most accurate indicator and should be matched to the exact parts combo.
 
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