Dynamic Compression Ratio Turbo
Dynamic Compression Ratio Turbo What's the general consensus for DYNAMIC compression with a Max effort turbocar, running an ethanol based fuel? or what would be considered a "High" dynamic compression? In conjunction with boost? over 200psi Cranking compression? Just thinking out loud..
Big ol can O worms about to get dumped out in this thread. Lol.JK
It just seems that dynamic compression is highly debated as to whether it even matters, especially in a max effort car. The only place in the engines power curve that's gonna really spike is the Tq peak and alot of max effort stuff never even sees the Tq peak at WOT. They blow past that on the brake.
i changed up to turbo, from a PUMP GAS Maxed out dynamic engine and personally tbought it was well worth the effort to reduce my dynamic from a 226 cranking compression to 170 by changing my CC size and cam dynamics.
i know...didnt answer your question or help in anyway. Just remembering all the brain twisting research i did on the subject and all the objections i got to any relevence dynamic compression has to do with WOT performance.
It just seems that dynamic compression is highly debated as to whether it even matters, especially in a max effort car. The only place in the engines power curve that's gonna really spike is the Tq peak and alot of max effort stuff never even sees the Tq peak at WOT. They blow past that on the brake.
i changed up to turbo, from a PUMP GAS Maxed out dynamic engine and personally tbought it was well worth the effort to reduce my dynamic from a 226 cranking compression to 170 by changing my CC size and cam dynamics.
i know...didnt answer your question or help in anyway. Just remembering all the brain twisting research i did on the subject and all the objections i got to any relevence dynamic compression has to do with WOT performance.
Really hard to say. I changed intakes , heads and of course, the turbo system was added, lol. I didnt do a comparison NA. The high dynamic setup was great NA. Power was always right there. No waiting for it to get up on the cam. Out of boost, the low dynamic is surprisingly strong too. I expected it to be noticibly sluggish at tip in, but it moves out strong. In the process of lowering compression, i did go from stock LS3 heads to a set of 317s i hand ported to 220ccs. So read that how you want to.
You talking for class limited stuff or just an “all out” personal toy with no restrictions?
For “race setups” you are aiming for high RPM and HP. As mentioned you blow right past this entire PK TQ range on most “race cars”. Talking Ferrari’s VS Semi trucks... I was under the impression most race aren’t concerned with the lost torque.
“Ethanol fuel” is a super general term and the knock threshold can vary a ton depending on the blend. Where and how much pressure the cam bleeds off is also a huge factor. Can’t see there ever being a cut and dry answer for how much cranking compression is wanted for a max effort ethanol fuel.
From what I’ve read mechanical compression is much less efficient than boost at making power. So you want just enough SCR/DCR to spool your setup quick enough for your application/tastes. Any additional compression will shrink the tuning window and be more prone to peaky cylinder pressures, head sealing issues, and part failures. High RPM helps get the heat out more quickly for each cycle. So in general the higher you can rev the better.
If you are class limited on turbo size you want to run as much SCR/DCR as possible to squeeze the most out of the setup
For “race setups” you are aiming for high RPM and HP. As mentioned you blow right past this entire PK TQ range on most “race cars”. Talking Ferrari’s VS Semi trucks... I was under the impression most race aren’t concerned with the lost torque.
“Ethanol fuel” is a super general term and the knock threshold can vary a ton depending on the blend. Where and how much pressure the cam bleeds off is also a huge factor. Can’t see there ever being a cut and dry answer for how much cranking compression is wanted for a max effort ethanol fuel.
From what I’ve read mechanical compression is much less efficient than boost at making power. So you want just enough SCR/DCR to spool your setup quick enough for your application/tastes. Any additional compression will shrink the tuning window and be more prone to peaky cylinder pressures, head sealing issues, and part failures. High RPM helps get the heat out more quickly for each cycle. So in general the higher you can rev the better.
If you are class limited on turbo size you want to run as much SCR/DCR as possible to squeeze the most out of the setup
Basically I shot for 12:1 (actually 11.93 :1) for SCR which puts me around 9.52:1 Dynamic ( a bit over 200psi crank compression) when taking the IVC of 65* into account.
E-85 will be used on low boost with Twin Forced Inductions GTR-88s (Garrett GT50-88s) on a 427 LSX. M1 methanol will ramp in on a separate set of injectors once boost surpasses a certain threshold. Ive just always been under the assumption that when running alcohol, you could benefit from the added compression. E85 in my area has been pretty dang consistent, Ive actually gotten E-94 consistently from a few local gas stations
E-85 will be used on low boost with Twin Forced Inductions GTR-88s (Garrett GT50-88s) on a 427 LSX. M1 methanol will ramp in on a separate set of injectors once boost surpasses a certain threshold. Ive just always been under the assumption that when running alcohol, you could benefit from the added compression. E85 in my area has been pretty dang consistent, Ive actually gotten E-94 consistently from a few local gas stations
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“E85” is the big factor as it can have 40% to 90% ethanol and they can use low octane crap blender fuel or they can use standard 87. Other times with barrel E85 they can use race fuels to blend with or 98% pure ethanol. So you’re knock suppression ability will be all over the board.
In your case I’m sure you’ll be fine at “Street boost levels” on typical pump blends from 60%+ ethanol assuming they don’t use super crap octane blender fuels.
Max effort to me means you have no set goal power wise. If you had a goal and could reach this goal on the fuel you choose at 12:1 then there’s absolutely no reason to run lower compression. You’re just leaving response on the table. If you’re goal is to really see how much you can squeeze out of an engine, lower compression is the way to go.
The way I understood it, there will alway be a point where the tuning window gets really small and you’re likely hood of lifting a head or damaging parts come into play. This is almost always due to heat. By running more boost and less SCR you are able to have more cylinder pressure with less overall cylinder heat. (this assumes the turbo system is up to the task)
In your case I’m sure you’ll be fine at “Street boost levels” on typical pump blends from 60%+ ethanol assuming they don’t use super crap octane blender fuels.
Max effort to me means you have no set goal power wise. If you had a goal and could reach this goal on the fuel you choose at 12:1 then there’s absolutely no reason to run lower compression. You’re just leaving response on the table. If you’re goal is to really see how much you can squeeze out of an engine, lower compression is the way to go.
The way I understood it, there will alway be a point where the tuning window gets really small and you’re likely hood of lifting a head or damaging parts come into play. This is almost always due to heat. By running more boost and less SCR you are able to have more cylinder pressure with less overall cylinder heat. (this assumes the turbo system is up to the task)
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