Minimum Cross Sectional Area: Question

[randy331]

GaryC what is the comparison of angle mill to raise compression or as a after thought?

Steve, have you noticed those that build no actual real engines, or do any testing, and have no data of their own, are the most vocal opposition to those that do build real engines?

Randy

[LSP]

GaryC what is the comparison of angle mill to raise compression or as a after thought?

Steve, have you noticed those that build no actual real engines, or do any testing, and have no data of their own, are the most vocal opposition to those that do build real engines?

Randy

Be it on the dyno or the race track, the scoreboard holds no bias and tells the truth, why do they not participate?

[skinny z]

Torque Master is not a complete engine simulation program. There are a limited number of inputs.

If just CR is increased (and peak HP RPM has remained constant) the duration shown is reduced but the est HP still has increased.

For the program to want / show the same duration with the higher CR as it did with the lower CR the peak HP RPM would needed to be raised.

Stan

This is exactly how I'm learning the program works. And for my intents and purposes, it's giving me what I'm looking for with the engine parameters that I have. It's also interesting to see how one plays out against another. That's how the CR vs duration conversation came up in the first place.

Kevin,
What was the results from the other software that you used for recommended cam duration verses CR?

Stan

It's always been the case of of more CR equals more duration. Or more specifically, a later IVC. This was directly linked to the dynamic compression and that became the target value. This was irrespective of port flow or peak HP RPM.

[skinny z]

... I did a back to back raise the comp test. Same day on the dyno I pulled the heads and angle milled them enough to raise comp about 1 full point, put the heads back on and re pulled it. There was no noticeable change in where it made peak tq/hp at and there wasn't the power gain most think would happen with that increase in comp.

Randy

In my reply to Stan regarding virtual results from other software I mentioned that there's always a strong connection between CR and duration/IVC. Typically I can see this being the case but not always.
My question here is that did that bump in compression in the back to back testing (I wish I had an engine dyno) bring the cam spec more into line with what would be considered optimal or further away? If it was the latter, I can see how your results play out. This isn't a discussion about the effectiveness of angle milling before or after the fact but rather one of the increase in CR generally speaking.

[GARY C]

GaryC what is the comparison of angle mill to raise compression or as a after thought?

Their claims were angle milling the head after port work and valve job could show little to no gain and could actually hurt power, Judson said in one case they had to rework the chamber to get the power back and give up the compression?

Their consensus seemed to be that an angle milled head should be part of the original build design and testing, not sure if the cam would play into that, it was never mention that I remember.

[gmrocket]

I see the program works that way but in real life, does that work that way?

No it doesn't. I did a back to back raise the comp test. Same day on the dyno I pulled the heads and angle milled them enough to raise comp about 1 full point, put the heads back on and re pulled it. There was no noticeable change in where it made peak tq/hp at and there wasn't the power gain most think would happen with that increase in comp.

Randy

So this one test makes it conclusive?

SAM, BES, Wells and other Engine Builders have done similar test and concluded that angle milling a head as an after thought was not a good idea if one wanted to take advantage of an angle milled head.

you got links to any of that?

[steve316]

Gary C I remember Judson Massingill co-ower of SAM-tech making a statement saying that angle milling down to the seat could hurt the flow enough to actually lose power.

[GARY C]

No it doesn't. I did a back to back raise the comp test. Same day on the dyno I pulled the heads and angle milled them enough to raise comp about 1 full point, put the heads back on and re pulled it. There was no noticeable change in where it made peak tq/hp at and there wasn't the power gain most think would happen with that increase in comp.

Randy

So this one test makes it conclusive?

SAM, BES, Wells and other Engine Builders have done similar test and concluded that angle milling a head as an after thought was not a good idea if one wanted to take advantage of an angle milled head.

you got links to any of that?

Judson was the only one I read and all of his links are gone since changing their web page, Tony and Dennis told me when I was consulting them on engine builds.

[GARY C]

Gary C I remember Judson Massingill co-ower of SAM-tech making a statement saying that angle milling down to the seat could hurt the flow enough to actually lose power.

Yes that was my understanding on the valve seat part and milling into the topcut could effect pressure recovery I would think?

[gmrocket]

Torque Master is not a complete engine simulation program. There are a limited number of inputs.

If just CR is increased (and peak HP RPM has remained constant) the duration shown is reduced but the est HP still has increased.

For the program to want / show the same duration with the higher CR as it did with the lower CR the peak HP RPM would needed to be raised.

Stan

This is exactly how I'm learning the program works. And for my intents and purposes, it's giving me what I'm looking for with the engine parameters that I have. It's also interesting to see how one plays out against another. That's how the CR vs duration conversation came up in the first place.

Keep adding more compression and see what happens with the duration recommendation.

[skinny z]

Keep adding more compression and see what happens with the duration recommendation.

For the program to behave predictably, as in higher CR calls for additional duration and overlap, the other target values have to adjusted accordingly. It's easy to manipulate in the data fields.
I've tried many times with various inputs. The key here is to select an RPM peak, paired to an appropriate minimum port CFM and CR. If all of those are tailored to what you what expect to be a reasonable outcome, TM produces no surprises.
As an example: 383 SBC. Why would you have 11.5:1 compression and want to peak at 5500 RPM using heads that could supply to 6500? Doing that in TM yields the unusual results that have sparked some discussion here. The values above get you 276 on the intake on a 107 needing 270 min CFM. Overlap is 64. But the DCR is over 9:1. A terrible match in the traditional sense. Move that RPM up to 6500 and you get 296 on a 107 with heads requiring 300 CFM. Overlap 84. DCR is 8.4. That's a result you can work with.
Similarly, if only the CR is raised as suggested, dropping the above back to 10.5 but keeping the same RPM peak of 6500 nets 299 on a 107. Overlap 87. Drops the DCR to 7.6 while the heads need 286 minimum. It's easy to see that you need the duration to be able to run up to 6500. But the combination itself isn't well balanced. Take that 10.5 and dial back the revs to 6000 and now it's 289/107, 77 overlap and 7.9 DCR with 272 heads. Better collection of specs and results that make sense.
As DV mentioned once before, in computer-speak it's "garbage in = garbage out".
So, in the case of my 383, the fixed values I have are minimum CFM based on my as-is heads (255), the CR which will be 9.8 and the RPM in or around 5700 peak. TM spits out a 284/107 with a 8.1 DCR. Overlap 67. but it also indicates I would need 263 CFM at a minimum. I have only 255 so dialing back the RPM to 5500 gets 279 on the intake with heads needing 257.
So as a cam selection tool, I can see it's merit.
As for the original intent of this thread, TM falls right into it with the port CFM to MCA connection. A question I asked and has been answered in spades.
In the end, it's another tool to use should you be so inclined.

[Orr89rocz]

I have only 255 so dialing back the RPM to 5500 gets 279 on the intake with heads needing 257.

So we are back to the 280/230 deg lobe thats been done over and over again

[skinny z]

I have only 255 so dialing back the RPM to 5500 gets 279 on the intake with heads needing 257.

So we are back to the 280/230 deg lobe thats been done over and over again

Touché, Orr.
Well sir, it's certainly coming around that way. Perhaps a little tighter LSA than the norm.
Back in another forum I was trying to gain traction for "over-camming" the engine with respect to CR and peak HP RP and there was no contribution from anyone when I referenced a similar DV build with Edelbrock Performer heads and cams in the 284/240 range. The traditional approach was far too strong.
So, yeah, it may be I'll end up in the old school camp. Randy 331's thread, Pseudo racing engine surprise, is similar is some respects. CR is a little high and the RPM are also but still a fine example for me to duplicate (like many before).
FTR, best suggestion through TM is 284 single pattern on a 106 with 72 degrees of overlap or a dual pattern 284/288/106 with 74 degrees. That should make peak power around 5600 and use up all of my cylinder head capability. Decent DCR of 7.7 and cranking compression of 190+. I've built and tuned engines with that kind of spec so at least I've got that covered.

[gmrocket]

I have only 255 so dialing back the RPM to 5500 gets 279 on the intake with heads needing 257.

So we are back to the 280/230 deg lobe thats been done over and over again

Touché, Orr.
Well sir, it's certainly coming around that way. Perhaps a little tighter LSA than the norm.
Back in another forum I was trying to gain traction for "over-camming" the engine with respect to CR and peak HP RP and there was no contribution from anyone when I referenced a similar DV build with Edelbrock Performer heads and cams in the 284/240 range. The traditional approach was far too strong.
So, yeah, it may be I'll end up in the old school camp. Randy 331's thread, Pseudo racing engine surprise, is similar is some respects. CR is a little high and the RPM are also but still a fine example for me to duplicate (like many before).
FTR, best suggestion through TM is 284 single pattern on a 106 with 72 degrees of overlap or a dual pattern 284/288/106 with 74 degrees. That should make peak power around 5600 and use up all of my cylinder head capability. Decent DCR of 7.7 and cranking compression of 190+. I've built and tuned engines with that kind of spec so at least I've got that covered.

Are you aiming for some specific DCR?

[skinny z]

Are you aiming for some specific DCR?

Not specifically but I am avoiding those I've found too high and those that are too low.
On a dyno engine with the right fuel, some of the higher DCRs would obviously work. It's here that I'll have to admit that I have to consider the impact of that kind of result on the ultimate destination for this engine which up to this point I've deliberately excluded from the build process (and would like to keep it that way). As for the lower values, it seems there's always room for improvement there.