TimZ Posted February 26, 2009 Share Posted February 26, 2009 ok, fair enough, I'm a dummy. I just have to learn for myself that in my case bumping from 7.8:1 to 12:1 is going to be insignificant. If you can still run the higher boost with E85 (and I think you should be able to) then that's a whole different animal, and the best of both worlds. My issue was more with severely limiting boost just to say you have a higher CR. That and the notion that the higher CR will make the turbo spool sooner - it won't. I think if you want really high power output, you'll still want to drop the CR back a bit, but you probably don't absolutely have to go all the way down to 7.4 with E85. Quote Link to comment Share on other sites More sharing options...
mobythevan Posted February 26, 2009 Share Posted February 26, 2009 That sounds reasonable. I don't think many of us are trying to build the kind of power you are building so some of our goals are a little different. Quote Link to comment Share on other sites More sharing options...
ktm Posted February 26, 2009 Share Posted February 26, 2009 Moby, there is a great article by Hot Rod magazine that has a table that shows the increase in efficiency, and hence power, of various CRs versus you starting CR. The OP stated his goal of more power using a higher CR and less boost. This is counter intuitive. Quote Link to comment Share on other sites More sharing options...
islanddozer Posted February 26, 2009 Share Posted February 26, 2009 If you ask me, stick with low compression and build your hp with larger injectors, fuel management, and intercooler etc. Helps to have an engine that lasts. Unless you like to tear your engine down Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 26, 2009 Share Posted February 26, 2009 The difference in thermodynamic efficiency (hence the power gain you could expect under ideal conditions) between 7.4cr and 10cr is about 10%. The L-series makes in the neighborhood of 100-120hp naturally aspirated when off boost (if this case probably up to ~3500rpm). Here in this statement alone the largest potential lies untapped. The horsepower numbers there are about HALF what a properly built L Engine will produce. Say an L28 should be making near 300HP in N/A trim with modest compression (I'm talking relatively...not 14:1 by a longshot). The difference between the 120 HP N/A L28, and the 300 HP L28 is flow..... You want more power in your turbo engine, make the head flow. For so many years people were drubbed by Dr. Bell into believing that 'you just add boost' and you amke horsepower. Sure, that's true, no denying it. But if you want to do it at a LOW boost level, then you have to take the same steps N/A builders have used since time began: Make the head flow properly, maximizing flow into and out of the ports and power will follow. I disregard most characterizations on 'spool' or 'lots' of hp as they're indefinite...they really mean nothing. What is 'lots' to someone may be paltry to another. Most of the time I have dioscussions with people regarding 'turbo lag' it's because they are driving below boost threshold...same as what happens in an N/A with a Cam, sluggish performance till it comes on! And because the boost makes such a difference the effect is much more pronounced! I have seen people take L-Race Heads that were on N/A's for years, and put them on a turbo motor with startling results. A cam change to proper valve event timing, and the flow is just waiting to happen. Power comes from flow. If you don't have flow, you can't make power. Boost is just a measure of restriction to flow... Quote Link to comment Share on other sites More sharing options...
TimZ Posted February 27, 2009 Share Posted February 27, 2009 Here in this statement alone the largest potential lies untapped. The horsepower numbers there are about HALF what a properly built L Engine will produce. Say an L28 should be making near 300HP in N/A trim with modest compression (I'm talking relatively...not 14:1 by a longshot). No arguments here, but I should point out that the 100-120hp number that I was referring to was for below the boost threshold for a moderately sized turbo (i.e. boost onset at 3000rpm or less), not for peak n/a power. So, I think my estimate isn't too far off for an unboosted L-series in the 1500-3000rpm range. Once the boost hits, added flow helps both cases. Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted February 27, 2009 Share Posted February 27, 2009 You're at a higher altitude. What is your reasoning for not wanting to run more boost? Why not just go for low compression and run higher boost? You must be at like 5,000 feet. They don't start well and mine at least is somewhat lazy. My art carr 4000 stall converter works very well though. I think torque is what we would be interested in with the CR bump. I am not saying that a high compression turbo engine is built for a race car, just like I wouldn't say that a low compression engine running 30psi boost would be fun to drive to work everyday. My point is that if a person wants a fun commuter car I believe high comrpession is one way to go, or a really small turbine so you build boost at low rpms. Either one should be fun to commute in, neither one will have a big horsepower potential. I am not guessing about it, I am building one up to see. Hopefully the original poster will do the same. Then we can be two more guys saying that high compression and turbos is good or not good for our driving styles. I am trying both, big turbine, 10:1 motor on pump gas intercooled. We will see how us high altitude guys fair in drivability and peak hp. Quote Link to comment Share on other sites More sharing options...
ktm Posted February 27, 2009 Share Posted February 27, 2009 Relative thermal efficiency is the same regardless of your altitude. You will still only see a small increase in power. I found the article again: http://www.popularhotrodding.com/tech/0311_phr_compression_ratio_tech/index.html Quote Link to comment Share on other sites More sharing options...
Ruiz Racing Posted February 27, 2009 Author Share Posted February 27, 2009 thanks guys!!! all of your input is great! keep it coming. i just can't get over my thought. to be put simply, if you put the same mount of gas and the same amount of air in a smaller space, you should have a bigger explotion. ie more power. what i really want is a high reving, high flowing n/a, and put a turbo on it. to be honest... i like blowing up my engine. its the only way i learn not to do something. i can swap out a tranny now in a couple of hours. it use to take a week. 4 hours for a head gasket. no one ever tought me anything about cars. i learn all on my own. then i foung this site. it helps to get advice from other z people. thanks guys. Quote Link to comment Share on other sites More sharing options...
Pyro Posted February 27, 2009 Share Posted February 27, 2009 first fix the turbo spool issue. should get full boost under 3000 rpm with a stock turbine, which makes lots and lots of torque. Quote Link to comment Share on other sites More sharing options...
islanddozer Posted February 27, 2009 Share Posted February 27, 2009 first fix the turbo spool issue. should get full boost under 3000 rpm with a stock turbine, which makes lots and lots of torque. I agree about the turbo spool and yes compression is great for a N/A motor but turbo motors need to worry about detonation. Search detonation and see the results from other people. Quote Link to comment Share on other sites More sharing options...
ozconnection Posted February 28, 2009 Share Posted February 28, 2009 thanks guys!!! all of your input is great! keep it coming. i just can't get over my thought. to be put simply, if you put the same mount of gas and the same amount of air in a smaller space, you should have a bigger explotion. ie more power. what i really want is a high reving, high flowing n/a, and put a turbo on it. to be honest... i like blowing up my engine. its the only way i learn not to do something. i can swap out a tranny now in a couple of hours. it use to take a week. 4 hours for a head gasket. no one ever tought me anything about cars. i learn all on my own. then i foung this site. it helps to get advice from other z people. thanks guys. If you can afford to regularly 'blow your engine up', send some of your money to me! It can help to pay for the mortgage and school fees, the rising cost of fuel and groceries and the plane ticket to your place so I can drink your beer and help you rebuild that L engine of yours! Sounds like a plan. Cheers!! Quote Link to comment Share on other sites More sharing options...
HCCAFan Posted February 28, 2009 Share Posted February 28, 2009 A small shot will get that turbo spooling! Quote Link to comment Share on other sites More sharing options...
Daeron Posted March 1, 2009 Share Posted March 1, 2009 A small shot will get that turbo spooling! *eRP!* Yesh, its *eRP!* willL!! EDIT: For the thinker out there, what REALLY makes this funny isn't the simple drunken humour, its the fact that the joke sets one to giggling......... giggle, laugh, small shot.. nitrous.. ah-HAH, now you see... THAT is comedy. Quote Link to comment Share on other sites More sharing options...
HCCAFan Posted March 1, 2009 Share Posted March 1, 2009 Derp? Quote Link to comment Share on other sites More sharing options...
mobythevan Posted March 3, 2009 Share Posted March 3, 2009 My 12:1 engine is up and running with 9psi boost on e85. Only got about 250 miles on it so far but no problems. Quote Link to comment Share on other sites More sharing options...
Ruiz Racing Posted March 6, 2009 Author Share Posted March 6, 2009 how did you do it? what kind of power does it make? Quote Link to comment Share on other sites More sharing options...
mobythevan Posted March 6, 2009 Share Posted March 6, 2009 Its not an L engine. It is a 4G63 in my Talon. I increased displacement and compression at the same time so I don't know how much power came from each one. I just know the car has more torque down low than it did before. No dyno yet. Hopefully I can get my car and my friends talon on the dyno and compare. He has the same setup I use to have. Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted March 21, 2009 Share Posted March 21, 2009 Its not an L engine. It is a 4G63 in my Talon. I increased displacement and compression at the same time so I don't know how much power came from each one. I just know the car has more torque down low than it did before. No dyno yet. Hopefully I can get my car and my friends talon on the dyno and compare. He has the same setup I use to have. If you have a built 4G with 10:1 and on E85, then turn the boost up. For God's sake, man, quit teasing the d@mn thing and boost it! Quote Link to comment Share on other sites More sharing options...
mobythevan Posted March 21, 2009 Share Posted March 21, 2009 I hear you, its actually built at 12:1 compression. I am running 14psi boost on it right now. Quote Link to comment Share on other sites More sharing options...
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