Thickcajun Posted May 2, 2014 Report Share Posted May 2, 2014 Alright I have a chance to get my hands on a solid built lq9 with fast 102 goodies on top...massaged heads and cam.. my motors okay so I have time to think about this build... first things first 408 stroker kit comes to mind. Should I just be happy and build a 11.1 all motor or drop down the compression and do a turbo? This will be my daily driver not a track truck. By the way I hate what this site has done to me haha. Quote Link to comment Share on other sites More sharing options...
Blown 346 Posted May 3, 2014 Report Share Posted May 3, 2014 If you go boosted lower the compression as much as you can. typically people go start with 8:5.1, then once boost is in place the compression will bump up to around 9:5.1. The nice thing about boost is your not making the engine work for air. You dont put stress on the motor until you are in boost. You get the benefits of being to daily drive it, get decent gas mileage until you are in boost. My corvette that is pro charged gets 35 MPG on the highway and 28 or so in town just normal cruising. You do have to think about the cost going turbo, it can be far more than a blower. Depending on single or twins can be thousands of a difference spent. Quote Link to comment Share on other sites More sharing options...
AKSSS Posted May 3, 2014 Report Share Posted May 3, 2014 (edited) If you go boosted lower the compression as much as you can. typically people go start with 8:5.1, then once boost is in place the compression will bump up to around 9:5.1.I tend to argue with this. But this is just my opinion. As I am in the middle of building my new motor for my pickup, I will tell you my experience with my dd turbo'd truck. My motor was pretty much stock except for a set of diamond forged pistons that dropped the compression to 8.8:1 static. I had a stock cam and stock truck intake. I hated how my truck would respond with the low compression with no boost. It is very doggy just cruising around town. Don't get me wrong. I had a 3k multi disk converter so when I stomped on it, it would spool very quickly and responded well to boost. I personally think you need to decide on power goals first. If you want 500hp with a mild motor build, you can probably achieve this with 10psi. You can run 10 psi with 9.5 static compression. And the motor will be way more responsive just cursing and actually will spool the turbo sooner. Now I fully think if you were shooting for 20psi on pump gas then you would want the low compression. I just don't think that would be the right route for a dd. My current build is a 408 with 9.3 static compression and I am going to spray meth with 2 large nozzles. I am probably still going to get my boost levels up to Around 18 psi to achieve around 1k hp. But when I'm not racing I will probably only run around 8-10 psi on just 90 octane for the street and it will be very responsive still even with out the boost. Still, this is just an opinion. It is my opinion, but like buttholes, everyone has one. Edited May 3, 2014 by Aksss (see edit history) Quote Link to comment Share on other sites More sharing options...
Blown 346 Posted May 3, 2014 Report Share Posted May 3, 2014 I dont see how you dont agree. Lower compression is only to be on the safe side with boost. Now I have seen people with higher compression motors at 11:5.1 or 12:1.1 with boost. But those cars are making big HP and have thousands in the motor meant just for racing. My current car has 11:5.1 with the blower. Thats just due to the internals and heads still being stock. Would I lower it if I had the money for pistons and head work, yes. In my experience with blower cars, even with lower compression in the 9:1.1 range, I havent seen a issue with boost lag or it being doggy around town. Yes its not going to kick you in the pants cruising in vacuum. Once you hit the gas thats a different story. Boost and high compression dont mix too well. I will say this, the lower the compression the better for the engines sake of lasting. I wouldnt go any higher than 10:5.1 with the blower being accounted for. A blower and turbo are two different animals and both respond differently to boost. there is more lag with a turbo than a blower. Quote Link to comment Share on other sites More sharing options...
AKSSS Posted May 3, 2014 Report Share Posted May 3, 2014 I was getting at for the DD. I don't think I would go any lower than 9.0 on a dd. I just think that it is more pleasurable to drive when they aren't slouches in town. And either way. I love the way the turbo feels when it hits with low compression. It is insane how hard it comes on. Quote Link to comment Share on other sites More sharing options...
Blown 346 Posted May 3, 2014 Report Share Posted May 3, 2014 I do agree as well. My main point in saying to go with 8:5.1 all motor, then once boost is added the compression normally jumps up one full point to 9:5.1 Quote Link to comment Share on other sites More sharing options...
Thickcajun Posted May 3, 2014 Author Report Share Posted May 3, 2014 I do agree as well. My main point in saying to go with 8:5.1 all motor, then once boost is added the compression normally jumps up one full point to 9:5.1 With that being said what would be wrong with building the motor at 9:5.1 then boosted be 10:5.1? Or am I missing something. Quote Link to comment Share on other sites More sharing options...
Blown 346 Posted May 3, 2014 Report Share Posted May 3, 2014 With lower the compression you dont have to worry about detonation and blowing the motor under boost. When higher compression is used, people either use E85, race fuel of 110 octane or higher, or methanol to avoid detonation. In my experience with having 2 Pro charged cars and working with them and tuners over the last 11 years, lower the compression, you get a safer boosted situation and less room for detonation. Quote Link to comment Share on other sites More sharing options...
Thickcajun Posted May 3, 2014 Author Report Share Posted May 3, 2014 Well said guys thanks for the input and taking me to class so to speak. Quote Link to comment Share on other sites More sharing options...
AKSSS Posted May 3, 2014 Report Share Posted May 3, 2014 (edited) With that being said what would be wrong with building the motor at 9:5.1 then boosted be 10:5.1? Or am I missing something.Nothing. If it is tuned properly. By the dynamic compression will be way higher than that typically. Every single person that is running a stock motor with a supercharger is starting with a 10:1 cr. Just something to think about. With my stock lq9 cam. And my 8.8:1 cr, my dynamic compression at 10psi was around 13.8:1. If you wanna go play with this a little bit. Here's what you need. Go search for a dynamic compression calculator. Then use these specs. This is with the stock lq9 can though. If you had the intake valve close abdc degree of a different cam you could figure out the dynamic on it also. So just find one of the calculators online and put this in 8 cylinders (duh!) 4.000 cylinder bore ( if you building it probably 4.030 3.622" stock stroke (408 stroke is 4") 6.098 stock rod lenth 408 is 6.125) Static compression (pick your compression) Stock cam intake abdc 34 degrees You projected boost level And your altitude. Play around with it a little. Kind fun. Edited May 3, 2014 by Aksss (see edit history) Quote Link to comment Share on other sites More sharing options...
Thickcajun Posted May 3, 2014 Author Report Share Posted May 3, 2014 Nothing. If it is tuned properly. By the dynamic compression will be way higher than that typically. Every single person that is running a stock motor with a supercharger is starting with a 10:1 cr. Just something to think about. With my stock lq9 cam. And my 8.8:1 cr, my dynamic compression at 10psi was around 13.8:1. If you wanna go play with this a little bit. Here's what you need. Go search for a dynamic compression calculator. Then use these specs. This is with the stock lq9 can though. If you had the intake valve close abdc degree of a different cam you could figure out the dynamic on it also. So just find one of the calculators online and put this in 8 cylinders (duh!) 4.000 cylinder bore ( if you building it probably 4.030 3.622" stock stroke (408 stroke is 4") 6.098 stock rod lenth 408 is 6.125) Static compression (pick your compression) Stock cam intake abdc 34 degrees You projected boost level And your altitude. Play around with it a little. Kind fun. Gotta love math Quote Link to comment Share on other sites More sharing options...
AKSSS Posted May 3, 2014 Report Share Posted May 3, 2014 I love conversations like this. Lol. There is always more to learn! This is the kinda thing we use to talk about all the time years ago. Blown 346 has lots of experience and know how. So conversations like these are entertaining and helpful. I miss having other peoples opinions or options because everyone is scared of getting attacked. Lol! Building a new setup is fun and scary at times. Try to plan ahead like you are doing. Also talk to your tuner about what you are doing. They often can help with a lot of questions too! Quote Link to comment Share on other sites More sharing options...
chawkins6789 Posted May 4, 2014 Report Share Posted May 4, 2014 I need the boost. But my options to stay legal are a 112 or Whipple 140. I love these threads. A lot to learn and they are interesting. Quote Link to comment Share on other sites More sharing options...
Thickcajun Posted May 4, 2014 Author Report Share Posted May 4, 2014 Guys I can't tell you how much I've learned in the short period of time I've been on this site...it's actually turned me back into a gear head junkie! I'm a fabricator by trade so I just go back and forth looking at pictures. If any of you guys ever have drawings or a sketch of something you want made let me know. I have buddies in the industry so I have access to lasers, water jets etc..The hardest part for me is finding the time.. Quote Link to comment Share on other sites More sharing options...
fast4popper Posted May 8, 2014 Report Share Posted May 8, 2014 Quick reply. Forged 408. Static compression at 10.5:1. D1SC pro charged at 12psi... Runs like a raped ape. Quote Link to comment Share on other sites More sharing options...
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