jason_guy_yeah
New Member
I've turbo sized my engine for a GT4038 or T61. (Forged internals, for 400bhp) But, I've got High cp Je pistons. I'm assuming the equations are based on 9:1 cp. In other word, what size turbo would I get?
Need help factoring in 10.5:1 in turbo sizing
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jason_guy_yeah
New Member
Ok, I redid the calculations. And a 16G or GT3076 was ideal. But, with the increased CP, do I drop down in turbo size?
theshodan
Turbo Design Specialist
There are over 30 sizes in between the 16G and a GT3076. What are you doing to "calculate" what you're trying to achieve here?.
You don't necessarily drop down turbo size, you want to be able to calculate at least through about 4-7 general rpm points, and make sure that at the pressure ratios that you plan to use that they are inside of the "surge line".
But you also need to look at the turbine wheel that you plan to use.
Many of these turbos can make 400whp, its really a matter of HOW you want the power. A 16G must be pushed HORRIBLY past its supersonic point (where only hot air is coming in) to make 400whp, as opposed to a GT3076R (Don't forget the $200 in waterlines and fittings that you need to make it work.)
Your static compression ratio only really needs to be taken into account to help with your effective compression. If you want acceleration to be key, which is what great static compression is used for, look at the turbochargers that use lower pressure ratios to ensure you get the power you need. You may have a nick in your calculations. Trust me, been doing it over 8 years, and I'll still never give that secret totally away.
You don't necessarily drop down turbo size, you want to be able to calculate at least through about 4-7 general rpm points, and make sure that at the pressure ratios that you plan to use that they are inside of the "surge line".
But you also need to look at the turbine wheel that you plan to use.
Many of these turbos can make 400whp, its really a matter of HOW you want the power. A 16G must be pushed HORRIBLY past its supersonic point (where only hot air is coming in) to make 400whp, as opposed to a GT3076R (Don't forget the $200 in waterlines and fittings that you need to make it work.)
Your static compression ratio only really needs to be taken into account to help with your effective compression. If you want acceleration to be key, which is what great static compression is used for, look at the turbochargers that use lower pressure ratios to ensure you get the power you need. You may have a nick in your calculations. Trust me, been doing it over 8 years, and I'll still never give that secret totally away.
dc2GS-R
Super Moderator
If you have an ultimate HP goal then the key is to plot your volumetric flow rates along with your RPM and pressure ratio on different compressor maps to find the ideal setup. The way I picked my turbo out was to have my desired pressure ratio at my torque peak right in the most efficient island on the compressor map and to pick a turbo that also holds on to that high efficiency all the way to redline.
jason_guy_yeah
New Member
Hey check this link out and the #'s I put in. Tell me what you think.
http://www.squirrelpf.com/turbocalc/index.php?target_peak_power=400&engine_disp=109&target_af=12&bfsc=0.60&max_ic_loss=1.7&rpm_redline=6800&rpm_peak_power=6800&rpm_max_boost=6800&rpm_min_boost=4000&vol_1=99&vol_2=99&vol_3=99&vol_4=99&intemp_1=90&intemp_2=130&intemp_3=130&intemp_4=130&pre_company_id=1&pre_family_id=2&calc=yes&company=1&family=2&product=6
http://www.squirrelpf.com/turbocalc/index.php?target_peak_power=400&engine_disp=109&target_af=12&bfsc=0.60&max_ic_loss=1.7&rpm_redline=6800&rpm_peak_power=6800&rpm_max_boost=6800&rpm_min_boost=4000&vol_1=99&vol_2=99&vol_3=99&vol_4=99&intemp_1=90&intemp_2=130&intemp_3=130&intemp_4=130&pre_company_id=1&pre_family_id=2&calc=yes&company=1&family=2&product=6
jason_guy_yeah
New Member
I took in consideration of low preasure ratio and I got:
http://www.squirrelpf.com/turbocalc/index.php?version=4&target_peak_power=420&engine_disp=1.8&engine_disp_factor=0&target_af=12&bfsc=0.60&max_ic_loss=2&rpm_redline=6800&rpm_peak_power=6300&rpm_max_boost=6800&rpm_min_boost=4000&vol_1=92&vol_2=92&vol_3=92&vol_4=92&vol_1=92&vol_2=92&vol_3=92&vol_4=92&intake_temp_1=90&intake_temp_2=120&intake_temp_3=135&intake_temp_4=140&map_sel0=38&map_sel1=58
http://www.squirrelpf.com/turbocalc/index.php?version=4&target_peak_power=420&engine_disp=1.8&engine_disp_factor=0&target_af=12&bfsc=0.60&max_ic_loss=2&rpm_redline=6800&rpm_peak_power=6300&rpm_max_boost=6800&rpm_min_boost=4000&vol_1=92&vol_2=92&vol_3=92&vol_4=92&vol_1=92&vol_2=92&vol_3=92&vol_4=92&intake_temp_1=90&intake_temp_2=120&intake_temp_3=135&intake_temp_4=140&map_sel0=38&map_sel1=58
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jason_guy_yeah
New Member
I did some more research and I thought 92% would be more relistic. But, I'm taking a wild guess on max air temp.
dc2GS-R
Super Moderator
92% VE is still no where near right. I assume it is asking for your engine VE and NO engine comes close to that. Even compressor VE for a turbo in the prime of best island of a compressor map won't pull 80%. But either way....it's telling you 42 psi......lol. I'm not sure I would base my calculations on that. Real math works better. BTW.....wouldn't you want max boost at a lower rpm...alot closer to where you are spooling up at and creating positive manifold pressure?
jason_guy_yeah
New Member
uppyeyes ...the equations from turbobygarret. And the ones I've searched up, keep giving me high psi. ahhhg, this is frustrating.:evil:dc2GS-R
Super Moderator
Now do this using the info I pm'ed you. ^^
Yes it will take awhile lol, you don't have to do it all in one sitting. Just work on it a little each day and before you know it, you'll have a properly sized turbo instead of something that someone "claims" is good. Just give yourself some headroom to go for a little more power since most people naturally will want to later down the road