Big Issues with Cylinder Pressure (DCR)

[mt-engines]

Just to prove a point, Honda once built an engine with a compression ratio of 25 that ran on 25 octane fuel.
Not hard if you know how.

Was this a 2 stroke?

[Nut124]

...look at an L86 engine in a Cadillac Escalade.. 11.5:1 compression, 100,000 mile warranty towing capacity of 8,000+lbs
Heck, I think it was 10 years ago when Mazda announced their Skyactive engines that run on regular pump fuel and is 14:1 compression.

Direct ignition? DI runs like a diesel most of the time.

A few years back I went to Europe w family, 5 of us plus tons of luggage. We rented a Skoda (VW) Octavia(?) station wagon. It was a direct injected turbo 4-cyl. Good power with full load it seemed. Ran it hard, often 90+mph on highways. After 2 weeks and 1500+ miles, average fuel consumption for the trip was 42mpg regular.

It sounded like a diesel.

[skinny z]

Injector timing, valve timing, ignition timing, combustion shape torque management etc.

Its amazes me how little people are willing to understand just to be stuck in the stone age. Thats why threads arent like they used to be. You get the same 5 people talking about 1980s technology when it comes to anything, changing peoples builds around that outdated information, and not wanting to listen to people that have real world experience.

I've run 12.5:1 with 25lbs of boost on non exotic fuels, but if i were to post the build sheet, and say im buiding a new engine i bet i would get about 3-5 people telling me to run a 115 lobe sep cam, 7.5:1 compression, tunnel ram with a 144 blower and 3 2bbl carbs.etc

look at an L86 engine in a Cadillac Escalade.. 11.5:1 compression, 100,000 mile warranty towing capacity of 8,000+lbs
Heck, I think it was 10 years ago when Mazda announced their Skyactive engines that run on regular pump fuel and is 14:1 compression.

But according to the speed talk know it alls, its not possible.

Lots of the knowledge here is still lurking around.. I speak to a few of them from time to time. And they just don't want to respond to help people because of how the posts end up going, or the fact that every other post is some imaginary build with a budget of only stuff they have sitting around.

I can appreciate every point in this reply.
For me personally, it's about incorporating "the stuff I have laying around" AND mixing it up with the current and more advanced thinking. This thread alone, which has contributions from the usual suspects, has shed some light on possible places where I might make progress while still immersed in the old school mechanical bits. (If that makes sense).
Take the OP's (remember him?) original post with regards to DCR . That acronym has elicited both ridicule and insight with regards to it's validity. I've taken from that what I think to be relevant and will pursue it (even if my build turns out to BE imaginary) and see where it takes me.
I'm one who appreciates all of the replies.
It used to be my job to source information. Now it's my job to take that information and assimilate it. 8.4:1 DCR and iron heads? Yesterday I'd say no way. Today, maybe not so much.

[mt-engines]

I can appreciate every point in this reply.
For me personally, it's about incorporating "the stuff I have laying around" AND mixing it up with the current and more advanced thinking. This thread alone, which has contributions from the usual suspects, has shed some light on possible places where I might make progress while still immersed in the old school mechanical bits. (If that makes sense).
Take the OP's (remember him?) original post with regards to DCR . That acronym has elicited both ridicule and insight with regards to it's validity. I've taken from that what I think to be relevant and will pursue it (even if my build turns out to BE imaginary) and see where it takes me.
I'm one who appreciates all of the replies.
It used to be my job to source information. Now it's my job to take that information and assimilate it. 8.4:1 DCR and iron heads? Yesterday I'd say no way. Today, maybe not so much.

Thanks, a big reason i don't rely on DCR as a thing is because it doesnt give me the information i need.
take a 632
16:1
4.6 bore
4.75 stroke
6.7 rod
102 ivc


now try a
598
14:1
4.6 bore
4.5 stroke
6.7 rod
76ivc

both cams are the same size, only difference is intake centerline. Could you load the 632 on pump gas?
why did the 632 make almost 300 more hp granted the dynamic compression ratio is junk?

[btwick]

OP here.

Wow. This forum has the brain power to light up a mid-sized city.

With confirmation of the 8.4 DCR (with Wallace/Pkelly calculators using the .006 lift Comp Cam ABDC numbers) which is OK, and clear understanding of tuning/octane etc. for easy adjustments, and more invasive options (cam, cam timing, heads, etc.) if needed, I have all the info was hoping for and more.

In fact, with the mention this is a 71 Vette, and the responses about air dam cooling, including the aftermarket extension to push even more air up into the radiator (which I had no idea existed), this is far more than expected. Keep the convo going, but just so you know, super appreciative of the people on this forum.

BTW.. Will run this motor as is and report back on this thread (thinking mid-Jan or so) as to how it was tuned, octane, etc. and the nature of detonation if any. Stay tuned...

Cheers,
Brian

[Belgian1979]

...look at an L86 engine in a Cadillac Escalade.. 11.5:1 compression, 100,000 mile warranty towing capacity of 8,000+lbs
Heck, I think it was 10 years ago when Mazda announced their Skyactive engines that run on regular pump fuel and is 14:1 compression.

Direct ignition? DI runs like a diesel most of the time.

A few years back I went to Europe w family, 5 of us plus tons of luggage. We rented a Skoda (VW) Octavia(?) station wagon. It was a direct injected turbo 4-cyl. Good power with full load it seemed. Ran it hard, often 90+mph on highways. After 2 weeks and 1500+ miles, average fuel consumption for the trip was 42mpg regular.

It sounded like a diesel.

DI is a different animal. Most are also turbo-engines these days.

[Nut124]

I think just about all new engines are DI. Including the L86 V8 in the Escalade. That's how they can run those high CRs on regular.

[skinny z]

Thanks, a big reason i don't rely on DCR as a thing is because it doesnt give me the information i need.

...both cams are the same size, only difference is intake centerline. Could you load the 632 on pump gas?
why did the 632 make almost 300 more hp granted the dynamic compression ratio is junk?

I'm going to noodle around with that data and see how it shakes out using the same methodology as my builds. About the only similarity though is that they're engines. At 14:1, I'm sure the dynamics are very different.
This is really just an exercise in keeping myself entertained while hoping for some progress on my own project.

[RevTheory]

Thanks, a big reason i don't rely on DCR as a thing is because it doesnt give me the information i need.

...both cams are the same size, only difference is intake centerline. Could you load the 632 on pump gas?
why did the 632 make almost 300 more hp granted the dynamic compression ratio is junk?

I'm going to noodle around with that data and see how it shakes out using the same methodology as my builds. About the only similarity though is that they're engines. At 14:1, I'm sure the dynamics are very different.
This is really just an exercise in keeping myself entertained while hoping for some progress on my own project.

Including the fuels used. We're talking about pump gas builds sitting in a hot engine compartment in this thread, right?

[skinny z]

Thanks, a big reason i don't rely on DCR as a thing is because it doesnt give me the information i need.

...both cams are the same size, only difference is intake centerline. Could you load the 632 on pump gas?
why did the 632 make almost 300 more hp granted the dynamic compression ratio is junk?

I'm going to noodle around with that data and see how it shakes out using the same methodology as my builds. About the only similarity though is that they're engines. At 14:1, I'm sure the dynamics are very different.
This is really just an exercise in keeping myself entertained while hoping for some progress on my own project.

Including the fuels used. We're talking about pump gas builds sitting in a hot engine compartment in this thread, right?

As far as I'm concerned and the end result, yes. Plus a less than a desirable IAT.
That said, what I've been doing is correlating that theoretical data with what works or doesn't work in my application. The notion of IAT, isn't part of the calculations I experiment with but it's come to light (for me), that this is a critical element is my success/failure rates. The one engine I can think of in particular may have come out on the winning side had I incorporated a CAI rather than an open element filter case sweating underneath the hood. How it would have behaved on an engine dyno probably would have yielded very satisfactory results.

[Dan Timberlake]

Hi mtengines

"........
[look at an L86 engine in a Cadillac Escalade.. 11.5:1 compression, 100,000 mile warranty towing capacity of 8,000+lbs

Heck, I think it was 10 years ago when Mazda announced their Skyactive engines that run on regular pump fuel and is 14:1 compression."
......................
Isn't the L86 DI / Direct Injection? With variable valve timing, and piston squirters/coolers?

I think Skyactive is by definition DI / Direct Injection.

What maximum mechanical/non-dynamic compression ratio do you think the OP should be considering with his combo, as described?

regards,

Dan T

[hysteric]

Actually you can run 87 octane with a lot more compression ratio than that, been sitting on that technology for years, unfortunately electric cars are likely to be the big thing going forward.......so a technology that will get buried.

Can you share what the technology is?

Injector timing, valve timing, ignition timing, combustion shape torque management etc.

Its amazes me how little people are willing to understand just to be stuck in the stone age. Thats why threads arent like they used to be. You get the same 5 people talking about 1980s technology when it comes to anything, changing peoples builds around that outdated information, and not wanting to listen to people that have real world experience.

I came here in the hope of getting out of the stone age.......

I don't consider what you've listed as "technology" per se but a different approach. What I was hoping for was a discussion on the science or more importantly a direction on where to find the relevant papers by those who have pioneered this work.

Not looking for an argument but some direction perhaps. Besides most people stuck in the stone age wouldn't feel compelled to reply to a topic they don't understand but only the few who feel threatened or inadequate.

[F-BIRD'88]

Keep it relevant to a Gen I cast iron block sbc with a carb and mech+ vac ad diz. In a 70's vette (with the base flat hood too)

Its not a aluminum block LS motor nor a Mazda etc etc.
Bragging about this and that without context adds no value.

[mt-engines]

Hi mtengines

"........
[look at an L86 engine in a Cadillac Escalade.. 11.5:1 compression, 100,000 mile warranty towing capacity of 8,000+lbs

Heck, I think it was 10 years ago when Mazda announced their Skyactive engines that run on regular pump fuel and is 14:1 compression."
......................
Isn't the L86 DI / Direct Injection? With variable valve timing, and piston squirters/coolers?

I think Skyactive is by definition DI / Direct Injection.

What maximum mechanical/non-dynamic compression ratio do you think the OP should be considering with his combo, as described?

regards,

Dan T

My 70 corvette with l46 ran great on non oxy premium. even at its rated 11:1 compression. I then upgraded to dart 200 iron eagles, victor jr, 850 annular carb, 1 3/4 headers, 255@.050 solid cam... Then SB2.2... i had way more fun with the car when it was stock. If i were to have done it again I'd say 10.5:1 and a mild 227/234 cam runs great for you daily driven muscle car if you dont need anything too rowdy. With some decent heads you shouldnt have a problem making 430hp and 430 torque even with an Edelbrock performer rpm non air gap.

depending on driving habits and tuning ability, you could go higher. but a lot of guys love to lug their engines in 4th gear at 1500rpm and stomp it.

[btwick]

Continuing on the topic of CAI and ambient temps, part of this build was ceramic coating the headers and intake man. Any thoughts on if this will actually do anything to reduce temps in the engine bay?