BruceH
BBB Big Bore Boss 322
Josh, have you had any issues with your current 11:1 motor, boost, and e85?
Fuel's Winter Project: Build It Before It Blows
- Thread starter JoshK
- Start date
No, I have not. The only issue that I ever had with the 11:1 engine were the two cam followers that broke. My car never has been and never will be a DD. I have taken it to a few cruise nights and have had no issues what so ever with just putting around town at 15-20mph.
BruceH
BBB Big Bore Boss 322
I had a thought that maybe my experience has been an exception rather than the rule. I couldn't recall anyone having issues but thought I'd ask anyway.
My first turbo setup that I pieced together did have overheating issues. But that's long since been fixed.
When I first built the motor and it was na it made 332rwhp and 310rwtq iirc with 9:1, I noticed zero difference in feel or power from the stock compression and it drove great and hauled ass for an na car of its weight.
I'm making more power per boost then most ported head high compression builds and it's my preference so I just don't see the reward for the inherent risk with higher compression for a reliable street setup. And again I emphasis my views are based on longevity and reliability for a regulary street driven car.
I built the motor with boost in mind and it has worked out great even with e85.
Check out the table in that link above its a good reference, haven't seen it put like that before. Roughly it says I can add 4lbs of boost to get the same effective compression which would equate to the same effective compression as having 1 point higher static compression (add 4 less psi). When it comes to making power 4lbs of boost will give me more power than the 1 point of compression by a long shot, with an overall same effective compression ratio in the end. Goes back to that old saying boosted cars don't need higher compression to make good power.
I like to see that on that chart at 9:1 and 16psi I have roughly the same effective compression as I would with 12psi and 10:1 static compression. So when you look at it like that in this case the higher boost lower compression motor is capable of more power at the same overall effective compression.
I can see the argument for a belt driven blower where its a set max boost level most of the time. But for a turbo car build I just don't see the benefit or need at all. We can add boost without affecting iat's as drasticly. More air and more fuel is more power. Instead of trying to get some power by adding heat and pressure to the combustion chamber all the time from the get go. My 2 cent ramblings lol
When I first built the motor and it was na it made 332rwhp and 310rwtq iirc with 9:1, I noticed zero difference in feel or power from the stock compression and it drove great and hauled ass for an na car of its weight.
I'm making more power per boost then most ported head high compression builds and it's my preference so I just don't see the reward for the inherent risk with higher compression for a reliable street setup. And again I emphasis my views are based on longevity and reliability for a regulary street driven car.
I built the motor with boost in mind and it has worked out great even with e85.
Check out the table in that link above its a good reference, haven't seen it put like that before. Roughly it says I can add 4lbs of boost to get the same effective compression which would equate to the same effective compression as having 1 point higher static compression (add 4 less psi). When it comes to making power 4lbs of boost will give me more power than the 1 point of compression by a long shot, with an overall same effective compression ratio in the end. Goes back to that old saying boosted cars don't need higher compression to make good power.
I like to see that on that chart at 9:1 and 16psi I have roughly the same effective compression as I would with 12psi and 10:1 static compression. So when you look at it like that in this case the higher boost lower compression motor is capable of more power at the same overall effective compression.
I can see the argument for a belt driven blower where its a set max boost level most of the time. But for a turbo car build I just don't see the benefit or need at all. We can add boost without affecting iat's as drasticly. More air and more fuel is more power. Instead of trying to get some power by adding heat and pressure to the combustion chamber all the time from the get go. My 2 cent ramblings lol
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BruceH
BBB Big Bore Boss 322
My calculations when comparing stock 9.86 to 11 compression and boost were roughly 3psi. It was like my motor was making 3psi more boost due to the higher compression. 3psi of free boost is a good deal imo.
If you find yourself with free time try some e85 white paper searches. A few universities have done extensive testing that is very interesting.
If you find yourself with free time try some e85 white paper searches. A few universities have done extensive testing that is very interesting.
The majority of your power comes from the air and fuel you can move through the motor. So I see the equation the other way around from how you describe it. If a point of compression is worth roughly 10-20rwhp and a widely accepted rating for superchargers is 20rwhp per psi. Then you could drop your compression 1 point and loose say 20rwhp. But then add 3lbs of boost to get the same overall effective compression you had before, but now you picked up 60rwhp for a net gain of 40rwhp (you have more air and fuel in the motor at the same air/fuel ratio) and your end result is the same final effective compression ratio with more power. But like I mentioned if you just running the same pulley belt drive power adder setup, then higher compression can be effective at getting some more power but I can't see it ever really outweighing putting more air and fuel in the motor. (which is safer/easier with lower compression)
I run pump gas more often still as its more practical for a car I like to drive to and from work a lot. Actually haven't put e85 back in the car since my last track outing.
Once my new setup is up and running and off the dyno and warm weather is around I will run e85 more often I suspect.
I run pump gas more often still as its more practical for a car I like to drive to and from work a lot. Actually haven't put e85 back in the car since my last track outing.
Once my new setup is up and running and off the dyno and warm weather is around I will run e85 more often I suspect.
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The fuel is going to be the same no matter the compression for x amount of HP though right?
I am still not arguing directly in either direction. My engine at 12.7 should require less lbs/min to make x HP than say a 10.5:1 with the 11cc pistons right? Th engine itself is compressing more air by itself so it isn't Dependant on the turbo to force or flow the air for it. Thus making this turbo more capable? Is this completely off base? This is the idea I was asking about when I made the Compression vs Boost" thread a year or so ago.
I am still not arguing directly in either direction. My engine at 12.7 should require less lbs/min to make x HP than say a 10.5:1 with the 11cc pistons right? Th engine itself is compressing more air by itself so it isn't Dependant on the turbo to force or flow the air for it. Thus making this turbo more capable? Is this completely off base? This is the idea I was asking about when I made the Compression vs Boost" thread a year or so ago.
BruceH
BBB Big Bore Boss 322
I've been daily driving mine since the spring. Running 92 octane just fine. The only e85 station I have is 10 miles away so it's also more practical for me to use gas when daily driving.
BruceH
BBB Big Bore Boss 322
one eyed willy
Pizzle fo shizzle
I think you need to find out the efficiency range of the turbo you just bought. No point in running high compression just to run that turbo at 10psi. I think either combo will get you to what you want, since you just bought the turbo, and that's probably not going to change....start there and work your way back.
How much boost are you wanting to make? What feels comfortable to you? What's the HP goal? Are you dead set on the boss block? What compression will it take to get you there?
How much boost are you wanting to make? What feels comfortable to you? What's the HP goal? Are you dead set on the boss block? What compression will it take to get you there?
Compression wise yes to a degree, but its still a ratio, so when you add air you have to add fuel to get the same ratio. More air and fuel in the combustion chamber is what makes the power.
I'm not arguing its really a moot point. As you can see on the forum you can make power either way. I just see this trend that you have to have higher compression to make power and that I just don't see. When I first built my motor on this very forum I got ridiculed for building a 9:1 motor and that it would be a dog and not make any power.
If its an e85 setup and not a daily driven car, fuck yeah throw some compression at it and let it eat.
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Yes Bruce, but my turbo is rated at, let's say 100lbs/min of air. If the engine itself can compress that air more, then the turbo should be higher HP capable on a higher compression engine right? What do your catalogs show on the volume of air your engine takes in now compared to the lower compression engine.
I know you're not arguing Jeremy. I am enjoying this conversation for its volume of ideas.
Paul, I bought the turbo with the goal of 1000whp in mind. I want the dyno sheet. Realistically I want to run in the 800whp range. I am set on the big bore as I believe Bruce on the advantages of unschrouding the valve to promote flow and want to stay with as close to a square engine as possible but add cubes.
Paul, I bought the turbo with the goal of 1000whp in mind. I want the dyno sheet. Realistically I want to run in the 800whp range. I am set on the big bore as I believe Bruce on the advantages of unschrouding the valve to promote flow and want to stay with as close to a square engine as possible but add cubes.
one eyed willy
Pizzle fo shizzle
Unlike a supercharger set up, cylinder heat will play a pretty big part. That forward facing setup you are wanting will add some heat and back pressure so keep that in mind.
Look at what JPC does, they make great power with a similar set up you are wanting to go with, what comp do they run on their cars.
I'd personally step up to 10.1 possibly if I ever rebuild, but I've been happy with 9.5. I'd personally never run more than 20psi-25psi, just because I don't want to deal with the hassles of pipes blowing off.
Just figure out the parts of the equation that are already set, fill in the blanks from there.
Look at what JPC does, they make great power with a similar set up you are wanting to go with, what comp do they run on their cars.
I'd personally step up to 10.1 possibly if I ever rebuild, but I've been happy with 9.5. I'd personally never run more than 20psi-25psi, just because I don't want to deal with the hassles of pipes blowing off.
Just figure out the parts of the equation that are already set, fill in the blanks from there.
Very good point Paul. You will need to be at a higher pressure ratio to get a larger turbo into the sweet spot/efficiency island without getting surge and making heat. (turbo is flowing more air than the motor can move at that rpm and doing more work/making more heat)
Bobby's setup for example. At 13psi he made 735rwhp, he added 2psi and made 778rwhp at 15psi, thats only a 43rwhp gain with 2lbs of boost, not bad, but with 3 more psi for a total of 18psi he made 875rwhp. That's almost 100rwhp gain with 3psi as the turbo's final got to a high enough pressure ratio to put them in a more efficient island on the compressor map, moving more air easier while generating less heat means more power.
When it comes to a turbo if you need 60lbs of min of flow from it to get the power you want, you don't need/want a turbo that flows 100lbs/min.
This goes back to sizing the turbo just big enough to make the power and flow you want.
Like the twin 62's on my car, they are too big for my power level as they wont start to shine till 800rwhp+.
I debated going to a 76 just to do it but something in the 70mm range is much better paired for my max power goal of 800rwhp.
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Why would the forward facing add back pressure? That would be the same as S&H's new setup having higher back pressure, which we have seen flows very well. The exhaust gasses are going to get to the turbo sooner and have a bigger downpipe so they will get away from the engine sooner. If you look at the yellowbullet turbo 101 threads they would recommend I use 2.25 pre turbo pipes instead of the 2.5 I am doing
Less volume of piping between the head and the turbine. Less volume to fill means higher pre turbine pressure which is good for spool, but yield higher pre turbine/back pressure at the head. Hence why we stayed with 2.5" piping pre turbine that increases to 3" at the merge (on the single kit) and why we put the cutout on the downpipe standard.
Look at a sts turbo setup, a lot of exhaust volume to fill pre turbine so less pre turbine pressure and heat. So they spool up slower more like a 1:1 setup but are very easy on the motor.
Look at the 2.3 ecoboost. Turbine housing built right into the head, they have inconel exhaust valves due to the heat and back pressure it will see.
Look at a sts turbo setup, a lot of exhaust volume to fill pre turbine so less pre turbine pressure and heat. So they spool up slower more like a 1:1 setup but are very easy on the motor.
Look at the 2.3 ecoboost. Turbine housing built right into the head, they have inconel exhaust valves due to the heat and back pressure it will see.
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Hopefully it will spool similar to your old setup moving it closer, but you did go up quite a bit on the turbine wheel size. That smaller compressor wheel than turbine wheel will help spool some as well. I was talking to Joe about that the other day, when you go bigger on the turbine to get the flow and rpm you want you can go smaller on the compressor to get some of that spool back. Ie a 70mm compressor with a 75mm turbine. I believe that's why they recommended the 78 over the 80 for you.
I am very anxious to see this new setup come to life Josh!
I am very anxious to see this new setup come to life Josh!
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Mentioning my old setup I bought from Paul and spool time. When I pulled the engine, 4 of 8 exhaust ports showed that it had blown out the exhaust gasket and were leaking. The godspeed WG was also black from it leaking on the v-band.
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