How high can we take compression on 93 octane?

I'll be doing the tuning myself so I'll be able to take the time to fine tune it. Can I safely run this much compression at 90+ degrees in during the summer?

If it's safe N/A, what about hitting it with a 100 shot (not sure if it'll be dry or wet)?

Thanks.

 

11.6:1 could be close. DCR has a lot more to do with it I think. 93 would probably be fine, may have to make some slight timing adjustments. But mostly it would depend on your valve events along with your SCR.

 

Worry about your DCR... I would stay around 8.5 DCR on 93 octane, I have run 8.6 without any issues though...

 

I used to have a web sight to figure that out, but my computer crapped out and I had to buy a new one. Does anyone have a link to posy?

 

http://www.kb-silvolite.com/calc.php?action=comp

 

I've been reading posts around here about DCR and they've been saying we can run around 9.0-9.1 for DCR due to the aluminum heads, combustion chamber designs, and computers. I'm still deciding on my cam though so until I make a final decision I won't know my DCR for sure.

 

Am i doing this right?
Im coming up with higher than expected

TR 224
stock bottom
61 cc afr
.054 MLS gasket
7.40 push rods
93 oct fuel

every others numbers are stock

??

 

9.0...

93 Octane gas??? Or, are you runnig something higher???

 

I get approximately 11.09 to 1, assuming .006 - .007 out of the hole. Cannot figure DCR with out all cam specs (lsa, adv, etc...). Push rod length has nothing to do with it, or are you talking about piston rod length???

BTW the calculator linked above does NOT take all the variables in . Here is the VEcalulator J-Rod built. BEST I have seen. Go to the DCR tab, fill in the bold green areas and all your specs are spit-out below on the same tab.

VEcalculator

 

my cam is on a 114 lsa I think it has 4 degrees advance but I can be very wrong

the push rod are 7.4

 

Much better calculator. I wish I knew my events @200, I only have .006 and .050.

 

So, are you OK now, Phil? J Rod's calculator from Side Step's link looks pretty straightforward and appears accurate.

 

I must be doing it wrong. I came up with 10.445

I dont know what my stock numbers are, and im guessing wrong

 

The one tricky bit is finding your Intake Valve Closing point. With a 244 degree @ 0.050" intake duration, which is what I believe you have, all you need is the intake centerline as installed, or the LCA and degrees of advance (if any, it's often 4) it's installed at. e.g.: 114 LCA, installed at 4 degrees adv, intake centerline = 110 degrees After Top Dead Center. IVC will be 224/2 or 112 degrees after the centerline, so 110 + 112 -180 = 42 degrees After Bottom Dead Center. Per the Silvolite instructions, add 15 degrees (I think this assumes a very aggressive cam profile, I'd be inclined to add 20 or more) and enter this value, 57, in the IVC box.

If your using the "VE Calculator", just enter 42 in the IVC box in the 0.050" duration column. When I tried your assumed cam IVC with it, and tweaked the specs to get a Static Compression Ratio of 11.06:1, the calculated DCR was 8.46:1

On the Silvolite site, after tweaking the specs to get an 11.06:1 Static CR, it came up with 9.306 Dynamic CR! I had to add 27.5* degrees, instead of 15 to the 0.050" duration (the addition is to simulate the 0.006" lift 'actual' duration), in order to get the same 8.46:1 DCR. I think it's mostly a matter of how aggressive an early lift rate the creator of the program assumes the cam will have. I'd say the best solution would be to get the "advertised" duration for you cam, and use the "VECalculator".
* I just realized the VECalculator re-computes the 'actual' valve events when you change the 0.050" ones. Sure enough, with 42 ABDC for the 0.050" point, it now shows 69.5 in the 0.006" column!

If the above doesn't help, why don't you post all the numbers you have entered in the (whichever) calculator and we'll see if we can scope out what's wrong?

 

Thanks, this has been very helpful. I just want to point out that in the DCR Comparison page the cells G 27 and I 27 need to be adjusted. Change the B's in the equations to G otherwise both DCR's are based on the first cam specs.

 

to much math for me
I was just wondering what my static would be

 

Did any of you guys determine the valve events for an f-13 (i believe this to be a cam My90Iroc is considering)?

So far Ive got the .050 events, I dont have the cam sheet in front of me, but i believe they are:

230/232 112 +4 108 ICL

IVO 7 BTDC
IVC 43 ABDC
EVO 48 BBDC
EVC 0 ATDC

It seems like i cant get dynamic compression without the specs at .006 and .200. Anybody know what they are?

 

11.2:1 Static Compression Ratio if it's a stock 346 block.