max compression for pump gas?
09-07-2007, 09:43 AM
#1
max compression for pump gas? whats the max compression you can run on pump gas? looking at going from stock 10.5:1 and adding some 55cc heads (milled from 62) and wanted to know if i could use this and still run pump gas (93 in texas)
09-07-2007, 10:25 AM
#2
You need to supply more info to make an informed decision. The cam you are going to run will greatly effect your dynamic compression which is what matters when discussing what octane to run and if knock will be an issue. Also, what is your quench going to be? The closer the quench, the less prone to knock the setup with be. Next, if you are milling to get to 55cc from 62, how much was milled? This is important because it will definitely impact your PtoV clearance, especially if you go with a larger duration cam.
Check the sticky up top for more info. A dynamic compression of around 8.6-8.9 I would think would be pump gas safe as long as your tune is good, and the timing isn't too aggressive and you have a tighter quench.
Check the sticky up top for more info. A dynamic compression of around 8.6-8.9 I would think would be pump gas safe as long as your tune is good, and the timing isn't too aggressive and you have a tighter quench.
09-07-2007, 10:47 AM
#3
Originally Posted by The Alchemist
You need to supply more info to make an informed decision. The cam you are going to run will greatly effect your dynamic compression which is what matters when discussing what octane to run and if knock will be an issue. Also, what is your quench going to be? The closer the quench, the less prone to knock the setup with be. Next, if you are milling to get to 55cc from 62, how much was milled? This is important because it will definitely impact your PtoV clearance, especially if you go with a larger duration cam.
Check the sticky up top for more info. A dynamic compression of around 8.6-8.9 I would think would be pump gas safe as long as your tune is good, and the timing isn't too aggressive and you have a tighter quench.
Check the sticky up top for more info. A dynamic compression of around 8.6-8.9 I would think would be pump gas safe as long as your tune is good, and the timing isn't too aggressive and you have a tighter quench.
09-07-2007, 10:57 AM
#4
Originally Posted by xBROKEx
it would be a 224/226 113lsa, and it would be stock deck height and pistons on the block. The heads are dart 205's milled .050
09-07-2007, 12:46 PM
#6
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Well without knowing for sure what you cam specs are for IV and EV positions at .006, .05 and .200 lift my best estimate is that you would be in the area of 9.16:1 DCR with 55cc heads and everything else as stock (except the cam of course). That is to high. 59cc heads should be around 8.68:1 which is still getting close to the limits but that is actually what I'm trying to find out for sure right now....what IS the limit for DCR on 91-93 octane...
09-07-2007, 01:21 PM
#7
Originally Posted by aero_ub
Well without knowing for sure what you cam specs are for IV and EV positions at .006, .05 and .200 lift my best estimate is that you would be in the area of 9.16:1 DCR with 55cc heads and everything else as stock (except the cam of course). That is to high. 59cc heads should be around 8.68:1 which is still getting close to the limits but that is actually what I'm trying to find out for sure right now....what IS the limit for DCR on 91-93 octane...
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09-10-2007, 01:45 PM
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Originally Posted by 02TransAm/Batmobile
So what number would be too high in DCR/SCR's on 91-93 octane?
09-10-2007, 01:49 PM
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Compression is all about what you have in parts, entended application, and tuning. If you have the cam to bleed the cylinder pressure off, chamber worked over and run the timing low enough you can 13:1 so its all about the specifics.
09-10-2007, 02:16 PM
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13:1??? I sure hope you are talking about SCR and not DCR. Static compression ratio doesn't really mean anything. Dynamic CR is what matters and that is determind by the cam and when the inlet valve closes after bottom dead center. You could tech. have a setup with 10.5:1 SCR that can't run on 93 without knock and you could have another set up with a huge cam that could run 14:1 SCR on pump gas (you get the idea). Just depends on what the dynamic compression ratio works out to be and how much quench you have.
09-15-2007, 09:56 PM
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Originally Posted by aero_ub
13:1??? I sure hope you are talking about SCR and not DCR. Static compression ratio doesn't really mean anything. Dynamic CR is what matters and that is determind by the cam and when the inlet valve closes after bottom dead center. You could tech. have a setup with 10.5:1 SCR that can't run on 93 without knock and you could have another set up with a huge cam that could run 14:1 SCR on pump gas (you get the idea). Just depends on what the dynamic compression ratio works out to be and how much quench you have.
