Turbo B16 Build, Help wanted with turbine selection. (Warning: Long Post)
03-16-2007, 01:46 AM
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Turbo B16 Build, Help wanted with turbine selection. (Warning: Long Post)
***I know this is long, I'd appreciate any positive commentary, and please read the entire post before responding. Thanks in advance for your attention***
Lately some friends and I have been thinking about putting together a turbo setup, after some consideration we came to the conclusion that the best candidate for the project would be a B16, the reasons for this also explain the primary goals of the setup.
As the B16 has a stroke length considerably shorter than the B18, but has a (relatively) long rod length, the motor can be spun to much higher speeds more comfortably. As both 1.6 and 1.8 liter applications are very low displacement numbers (compared with other forced induction applications for example the 4G63 with 2.4 crank or a G64 with the 4G head for a full 2.4, 2JZ, EJ257, etc.) generating large amounts of power requires taking advantage of the B16's internal design.
Taking full advantage of being able to spin a motor very fast will require a comprehensive build using quality parts, I know this will not be cheap.
I know that many people are familiar with the workings of rod and stroke lengths, but I'd like to elaborate a little further on why I feel the B16 is a better choice. If you already understand fully, go ahead and skip this part. The stroke length of a B18C is 3.433, The rod length 5.433. The B16's Stroke is 3.047, its rod length 5.290.
This represents about an 11% reduction in stroke, with only a 2.6% reduction in rod length. The reduced stroke results in significantly reduced piston speed -- the importance of a rod that is now perportionally even longer is the resulting decrease in piston forces on the cylinder wall, an issue which increases in importance with engine speed.
Thats the short version, but I think it covers the important parts. Someone please correct me if my analysis is incorrect.
With the B16 selected as the motor of choice, I would like to see a maximum RPM of 10,000. I'll take input on if thats a reasonable number to shoot for. I definitely want this to be a daily drivable car, and I don't expect 10,000 rpms to be a daily occurance, but I'd like to build a setup that can take alot of punishment in terms of engine speed.
The items I would like the most input of relate primarily to turbine and compressor sizing. I’ve been looking for a suitable compressor from the Garrett family. In addressing the cold side, I’ve done the basic numbers for airflow with correction and the motor should consume the following numbers at 1.5bar (2.5 pressure ratio) and at 85 degrees air temp.
RPM LBs/Min
10,000 50.616
9,000 45.55
8,000 40.489
7,000 35.42
6,000 30.36
After looking at compressor maps for various Garrett GT series turbos, it became immediately clear that a very large compressor is required to flow both 30 and 50lbs at a 2.5pr. Using a GT4082 (52mm inducer 82mm exducer, 50 trim) at 2.5PR, 50lbs/min lands in the 76% efficiency island. That’s decent. At the lower end the efficiency doesn’t look too bad either – plotting the points looks like a pretty good match for the desired flow range.
I don’t realistically expect the turbo to make 22lbs of boost much before 6,000, so I haven’t considered flow numbers at an unknown pressure ratio. This is of course related to hot side specifications and turbine wheel size.
What I really need help with is determining what exhaust configuration to run.
Garrett offers the GT40 compressors mated to a variety of exhaust side configurations. In all cases, Turbine Wheel Diameter is 77mm, trim is 78. The available aspect ratios are: .85 .95 1.06 and 1.19.
I do not know which is most appropriate for the application – essentially, which is the smallest size that will not choke the motor at 10k?
Further, can anyone offer input about where the boost threshold might be with each of the different aspect ratios?
As it is of relevance in answering the above question, I’m thinking of using 8:1 pistons, maybe 8.5:1.
I’d like input on whether or not I’ve done a decent job matching the compressor, and if not, what you might suggest.
As earlier stated what I need most is guidance on properly configuring the exhaust side.
Any input is appreciated.
Lately some friends and I have been thinking about putting together a turbo setup, after some consideration we came to the conclusion that the best candidate for the project would be a B16, the reasons for this also explain the primary goals of the setup.
As the B16 has a stroke length considerably shorter than the B18, but has a (relatively) long rod length, the motor can be spun to much higher speeds more comfortably. As both 1.6 and 1.8 liter applications are very low displacement numbers (compared with other forced induction applications for example the 4G63 with 2.4 crank or a G64 with the 4G head for a full 2.4, 2JZ, EJ257, etc.) generating large amounts of power requires taking advantage of the B16's internal design.
Taking full advantage of being able to spin a motor very fast will require a comprehensive build using quality parts, I know this will not be cheap.
I know that many people are familiar with the workings of rod and stroke lengths, but I'd like to elaborate a little further on why I feel the B16 is a better choice. If you already understand fully, go ahead and skip this part. The stroke length of a B18C is 3.433, The rod length 5.433. The B16's Stroke is 3.047, its rod length 5.290.
This represents about an 11% reduction in stroke, with only a 2.6% reduction in rod length. The reduced stroke results in significantly reduced piston speed -- the importance of a rod that is now perportionally even longer is the resulting decrease in piston forces on the cylinder wall, an issue which increases in importance with engine speed.
Thats the short version, but I think it covers the important parts. Someone please correct me if my analysis is incorrect.
With the B16 selected as the motor of choice, I would like to see a maximum RPM of 10,000. I'll take input on if thats a reasonable number to shoot for. I definitely want this to be a daily drivable car, and I don't expect 10,000 rpms to be a daily occurance, but I'd like to build a setup that can take alot of punishment in terms of engine speed.
The items I would like the most input of relate primarily to turbine and compressor sizing. I’ve been looking for a suitable compressor from the Garrett family. In addressing the cold side, I’ve done the basic numbers for airflow with correction and the motor should consume the following numbers at 1.5bar (2.5 pressure ratio) and at 85 degrees air temp.
RPM LBs/Min
10,000 50.616
9,000 45.55
8,000 40.489
7,000 35.42
6,000 30.36
After looking at compressor maps for various Garrett GT series turbos, it became immediately clear that a very large compressor is required to flow both 30 and 50lbs at a 2.5pr. Using a GT4082 (52mm inducer 82mm exducer, 50 trim) at 2.5PR, 50lbs/min lands in the 76% efficiency island. That’s decent. At the lower end the efficiency doesn’t look too bad either – plotting the points looks like a pretty good match for the desired flow range.
I don’t realistically expect the turbo to make 22lbs of boost much before 6,000, so I haven’t considered flow numbers at an unknown pressure ratio. This is of course related to hot side specifications and turbine wheel size.
What I really need help with is determining what exhaust configuration to run.
Garrett offers the GT40 compressors mated to a variety of exhaust side configurations. In all cases, Turbine Wheel Diameter is 77mm, trim is 78. The available aspect ratios are: .85 .95 1.06 and 1.19.
I do not know which is most appropriate for the application – essentially, which is the smallest size that will not choke the motor at 10k?
Further, can anyone offer input about where the boost threshold might be with each of the different aspect ratios?
As it is of relevance in answering the above question, I’m thinking of using 8:1 pistons, maybe 8.5:1.
I’d like input on whether or not I’ve done a decent job matching the compressor, and if not, what you might suggest.
As earlier stated what I need most is guidance on properly configuring the exhaust side.
Any input is appreciated.
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