370 or 347 for TT BW S300's?
10-27-2013, 08:32 AM
#23
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Obviously there is only a small handfull of turbine housings, all T4
If you wanted say 1300hp but also fast spool.
Would the BEP T3 0.70 A/R open turbine housing be an option using the larger turbine wheel ?
10-27-2013, 11:15 PM
#24
I don't see you being able to achieve enough flow through that small of a turbine housing unless peak torque was moved to an RPM much higher than what you'd normally expect.
Meaning a smaller engine, 4 cyl, 6 cyl, small de-stroked V8 or 4.6 2v/4v type motor.
A larger displacement V8 with a longer stroke HAS MORE volumetric efficiency at a lower RPM creating much more torque. This will create more drive pressure as a by product. I just don't see a .70 housing with a T3 flange being adequate on anything larger than 310-320 cubes turning 7500+ rpm.
Even that IMO would be close to choking and/or choking with that configuration. It might do it under that RPM as I've never tried it and had first hand experience with it or had a customer try it.
DrTurbo would be a better person to ask.
Meaning a smaller engine, 4 cyl, 6 cyl, small de-stroked V8 or 4.6 2v/4v type motor.
A larger displacement V8 with a longer stroke HAS MORE volumetric efficiency at a lower RPM creating much more torque. This will create more drive pressure as a by product. I just don't see a .70 housing with a T3 flange being adequate on anything larger than 310-320 cubes turning 7500+ rpm.
Even that IMO would be close to choking and/or choking with that configuration. It might do it under that RPM as I've never tried it and had first hand experience with it or had a customer try it.
DrTurbo would be a better person to ask.
Last edited by Sales@Tick; 10-29-2013 at 02:58 PM.
10-28-2013, 06:51 PM
#27
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Ive got an iron 5.3 in the garage I planned to sell in order to afford the 370. But lets say in the end I decided to stick with it and bore it 3.90 for an iron 347 instead of buying a new 370. Would 900-1000 whp be possible with twin BW's on a 347 without it pushing water, and still be good on the street? This is in the back of my mind incase my budget gets really tight and I cant afford the new 370.
10-28-2013, 07:21 PM
#28
I run a pair of T3 61mm turbos on a stock 6.0 in my daily driver and its pretty stout. It shows no sign of tapering off with each pound of boost I put to it. It dynoed mid 900s in the summer on 17psi... Way nastier now with 40 degree cooler air and a few more pounds of boost. I'd run the smallest turbo you can to achieve your goal. It'll end up being a lot more fun on the street. I'd have run the s258s from borg warner had I not picked up the pair of GT35rs for so cheap. And don't worry about all that tech-talk...no engine "displaces volumetric efficiency" anyway 
10-29-2013, 03:58 PM
#31
Mind sharing a reference I can check out regarding a longer stroke having an effect on VE? I don't recall any VE equations mentioning stroke length at all... Usually just things along the lines of VE = (cylinder air density)/(manifold air density).
10-29-2013, 03:59 PM
#32
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Wow, I didn't think that would be possible with T3 housings.
Always happy when the knowledge police stop by ...I always take Martins word when it comes to turbo/cam selection. I know the 370 would be better for low end torque, and be capable of making more power more easily than a 347. But do you think I could still be happy at 900-1000 whp with the right twins on a 347? Or is going to be pushing the limits of everything too much (requirement for higher PSI with smaller displacement). FYI I also decided to keep my TFS 215's for the build instead of selling them (original intent was to help with the budget) and getting stock heads. So I should have good clamping force for holding down the higher PSI required with the smaller 347.
...I always take Martins word when it comes to turbo/cam selection. I know the 370 would be better for low end torque, and be capable of making more power more easily than a 347. But do you think I could still be happy at 900-1000 whp with the right twins on a 347? Or is going to be pushing the limits of everything too much (requirement for higher PSI with smaller displacement). FYI I also decided to keep my TFS 215's for the build instead of selling them (original intent was to help with the budget) and getting stock heads. So I should have good clamping force for holding down the higher PSI required with the smaller 347. Last edited by schmendog; 10-29-2013 at 04:07 PM.
10-31-2013, 11:59 AM
#33
Increase in torque at those RPM's, VE increases.
Seeing the HPT screen shot in your avatar I would think you'd understand this?
Turn your 364 into a 408 with a 4" stroke crank and 4.030" pistons. Leave your VE table untouched. Take it to the dyno. Longer stroke, more cubic inches will move more air mass. Especially at lower RPM's if the cylinder head, intake and camshaft are left alone from the smaller engine to the larger engine.
This will show as a leaner AFR at those RPM's than with the 364. To compensate for the added air mass at those RPM's, which is leaning out the current air fuel ratio more, we go into the VE table and we make the VE coefficients larger.
This gives the engine more fuel, as the increase in volumetric efficiency from enlarging the engine moves more air mass. In this case, going from a 347 to a 370.
I didn't say anything about a VE equation involving length of the crankshafts stroke. You did that. All I said was that a longer stroke or more cubic inches will add VE as a larger engine 9/10 allows for more cylinder fill, especially in the case of the LS engine and it's extremely high flowing cylinder heads even from the OEM. On an older engine with heads that do not have the cross section, valve area or flow that the LS cylinder heads do, this may not be the case or hold true.
Longer stroke, or bigger bore in the case of the LS engine 9/10 equals more cylinder fill. More cylinder fill means more air mass/density in the cylinder. This means more fuel is needed to be burned to achieve an air fuel ratio that is optimum for producing maximum power. When you have to add more fuel to achieve the same air fuel ratio you had before adding stroke, bore, cubic inches, a smaller cam, a larger cam, a larger intake port, larger exhaust port, larger intake valve larger exhaust valve etc. etc. etc. etc. etc. Whether it's at low RPM's or high RPM's, means the engine has more volumetric efficiency at that RPM.
I'm tired of playing this game Jake.
Last edited by Sales@Tick; 10-31-2013 at 12:11 PM.
10-31-2013, 12:01 PM
#34
Wow, I didn't think that would be possible with T3 housings.
Always happy when the knowledge police stop by...I always take Martins word when it comes to turbo/cam selection. I know the 370 would be better for low end torque, and be capable of making more power more easily than a 347. But do you think I could still be happy at 900-1000 whp with the right twins on a 347? Or is going to be pushing the limits of everything too much (requirement for higher PSI with smaller displacement). FYI I also decided to keep my TFS 215's for the build instead of selling them (original intent was to help with the budget) and getting stock heads. So I should have good clamping force for holding down the higher PSI required with the smaller 347.
Always happy when the knowledge police stop by
...I always take Martins word when it comes to turbo/cam selection. I know the 370 would be better for low end torque, and be capable of making more power more easily than a 347. But do you think I could still be happy at 900-1000 whp with the right twins on a 347? Or is going to be pushing the limits of everything too much (requirement for higher PSI with smaller displacement). FYI I also decided to keep my TFS 215's for the build instead of selling them (original intent was to help with the budget) and getting stock heads. So I should have good clamping force for holding down the higher PSI required with the smaller 347.
10-31-2013, 02:05 PM
#35
Volumetric efficiency is the actual cylinder air mass divided by the ideal cylinder air mass. For an increase in stroke, both the numerator and denominator in that expression increase. The net gain in VE is nothing. Torque is NOT equivalent to VE.
Last edited by smokeshow; 10-31-2013 at 03:54 PM.
10-31-2013, 02:53 PM
#37
10-31-2013, 03:53 PM
#38
Exactly. Increased displacement just changes torque and power output, not how efficiently the air is used to make that torque and power. How the existing camshaft responds to the displacement increase introduces some dynamics into that efficiency number, though. I sent you a pm.
10-31-2013, 04:31 PM
#40
I realized earlier exactly where I went wrong.
When I mentioned the longer stroke creating more VE, I was visualizing the VE table in HPT. Thinking that if I did nothing but add stroke and displacement I'd obviously have to add fuel to compensate which would give me an increase in the VE coefficient in this table.
What I forgot, was that HPT has a table for displacement and that it has to use this displacement per cylinder to calculate VE coefficients and I was leaving the change in cubic inches out of the equation. As Jake said there is a numerator and a denominator and I was only looking at the change in air mass and not the change in displacement as a whole in terms of the VE equation.
The larger engine would truly have to be more efficient for its volume(displacement) to have a higher VE% than the smaller engine even though it produces more torque.
One of those "light bulb" moments haha.
