Anyone running high compression that can vouch for whether or not 12.89:1 static should be doable on a hybrid build with a massive cam and ECM tune?
Maverick swears up and down its not feasible, but I just don't believe that, would like some other opinions on the matter to be certain.

 

I've heard some people on 60degreev6.com say that they've run high (11-13) cr on pump gas with a large enough cam without problems but I'm still cautious. I decided on 9.5 cr on my own build so 1) I'm not compression limited (so turbo or nitrous is still on the table) and 2) long term carbon deposits don't send it into detonation. But in response to your other thread here's a couple links for you to read through. Here and here.

 

I have slightly over 11:1 <> I run 93 Octane my final lift is .544 / .571
13:1 might be a lil high for that octane

 

Well, there's 2 things that increase with CR... Cylinder pressure and cylinder temperature. Both of which only go higher with Forced Induction. The more air you compress in the chamber, the hotter it gets (which is how diesels are able to run using compression ignition as their CRs are generally around 24:1, IIRC, have to look in my notes from class). As cylinder temperature rises, so does the possibility of spark knock and detonation. Especially with an improperly tuned system. It MAY be possible to tune this out, but you'll have a much easier time tuning with the right engine compression ratio in the first place. Also, if you notice, most of the turbo hybrid guys are running 3x00 pistons to get the CR down.

Have you ever seen a drag race where the engine blows itself apart? That's the result of high CR plus bad tuning.

:edit: In conclusion, looking at the other posts, it MAY be possible to leave your 2.8 pistons and run the hybrid heads, but when you go FI, you WILL need to swap the pistons. And, you will probably end up running super unleaded gas with the stock pistons.

 

I know I have to do it for turbocharging, I don't doubt that at all, but thats a long ways down the road, so for the moment I'm looking to maximize N/A potential, I did find one interesting thread about using E85 though, its something like 100 octane, so I figure if I'm getting detonation on premium I'll try that, don't you also have to retard the timing some? And I know cam has a lot to do with it, as thats a huge part in the actual dynamic compression from what I read, and I'm getting a solid flat tappet from crower with a 3-7k powerband and 8k+ redline. 248* int and 250* exh @ .050 lift, and .501 gross lift on intake, with .511 exhaust. I'll see if I can hunt down a dynamic calculator online..

 

"Intake Closing Point (degrees)ABDC @ 0.050 lift plus 15 degrees" How do I determine that to calculate dynamic CR, is it just simply the intake duration @.050 lift+15?

 

Go over to kb-silvolite.com and use their cr calculator. That's a big cam, make sure you have a combination that needs it.

 

My power goal is 300 N/A, and at least 500 once I turbocharge, so yeah, I'll need it...And that is the calculator I used, but I'm not quite sure what I'm supposed to plug in for "Intake Closing Point (degrees)ABDC @ 0.050 lift plus 15 degrees"

 

your going to raise your compression 11-13 on a NA <> you will need to undo everything you have when you switch to Forced induction sounds like a good plan

 

Only things I will need to change when I turbocharge it, is pistons and crank, which is irrelevant because I still have stock, the only part I'm going to buy that will be replaced when I turbocharge is the headers, or I suppose you could argue the valvetrain on the heads, but they're hard enough to find with stock valvetrain let alone without.
Unless you mean tearing the engine down again, but that's still a fairly moot point, because I don't want to throw 500+hp at a car that hasn't been driven for the better part of 11 years, I'm building a nice, decent power level N/A v6 compareable to stock v8s, so that I can have the car running and work on everything else that needs work, before I start seriously mashing down with power output, if I had 500 hp in it, I would at very least need a rebuilt transmission, new driveshaft, and new rear end to handle it, way too much money at once to do that, you don't build an engine past your stock drivetrain, you build it up to that if you really want more power, then you modify the drivetrain before throwing an engine in that it can't handle...

 

Add 15* to your intake closing point and plug that in. IMO, above 10:1 dynamic is pushing it on pump gas.

 

I never did fully understand cam specs, so bear with me, but what defines the intake closing point, and in what format would such a specification be in?

 

The closing point of the intake valve. It should be listed with the other cam specs. If not call the manufacturer.

 

I ran 10.75:1 for a few years. Its doable but can be a pain! I ran 93 octane all the time. Sometimes when I went to the track, I'd put a couple of gallons of 110 in with it. Atleast I didn't get spark knock then. I would get spark knock pretty regularly under certain situations. When the motor was hot and I'd try to restart it, it wasn't uncommon for it to be very draggy while cranking. I ran a big cam, also. I don't recall the exact specs right now. I liked it, it wasn't tooo bad for street use. Later, I put a bigger cam in it, I hated it. Power breaks acted funny, idle was goofy. I typically couldn't run the ac while idling. This motor was built properly. It was built for high compression. It wasn't a "well, I don't want to pull the motor out to build it so here's what I'll have..." Not trying to slam anyone, just saying I've been there and done it. I will offer advice if you have anymore questions on it or want to take advice.

 

Can I get some thoughts on the possibility of running E85? its something like 100 octane I believe...

 

I ran 10.4:1 on 89 octane E10 for a year without issues. Still got great mileage and very little carbon buildup.


With E85 you'll probably have to get your fuel rail hard anodized and get E85 approved fuel lines and Orings. A lot of local guys are using it with great results.

 

Any idea what kind of availability E85 has in terms of gas stations?

 

you'll have to look around you...

I'm in Cornville but there is only a handful that sell it close enough to me. It's easier for me to get real race gas then E85 right now.

 

Looks like I'll have a static CR of 12.89 and dynamic CR of 10.28-anyone know stock dynamic CR for comparison? Cause I have no idea how high or low that DR is...

 

Stock is pretty low... like 8.3. 10.28 is alot but not unuseable. Premium.