r5baker
Probationary Member
- 4
- 0
- May 5, 2022
-
Blacksburg,
Virginia
No DSM here but this forum seems full of useful relevant knowledge. I have a '91 MR2 with a 2nd gen 3SGTE. For years I had a Garrett GT3271 on the car using a tubular divided manifold. Spool was very fast with this turbo and I had it pretty much maxed out at 25psi and 400whp.
The turbo was rebuilt once with a 360 thrust bearing but finally crapped out this year with oil coking up the bearings. For 'fun' I found an Ebay Garrett GT3782 that was on a Navistar DT466E and cut the exhaust housing flanges off and welded on a divided T3 to the T4 1.11A/R housing along with a 3" Vband. Nickel 55 rod with lots of preheat, post heat, and slow cool.
I put it on the dyno and it put down right at 500whp with very slow spool compared to the GT32 which I expected. Don't get me wrong, I like the additional power, but on the street fast spool is much more fun. The dyno plots below are both 3rd and 4th gear runs on the same plots.
I just swapped out the GT3782 project for a Tims's Turbos built HX35/40 with the 7-blade HX40 60x84mm compressor and the HX35 12-blade 70x60mm turbine. I have not returned to the dyno but spool is nearly identical with less top end. Any insight on whether this is expected with the Holset hybrid?
I am just puzzled that the 12cm^2 divided housing driving a smaller 70x60 turbine spools up nearly identically as the 1.11 A/R T4 housing driving a 72.5x66 turbine on the GT3782? In 4th gear datalogging shows only a 200rpm advantage to the Holset. In 1st through 3rd there is no advantage and like I said seems to run richer at the same boost 28-29psi with no fuel changes and speed density. Fuel is E85 (likely more like E50-E60) that I have not measured the percentage yet.
The turbo was rebuilt once with a 360 thrust bearing but finally crapped out this year with oil coking up the bearings. For 'fun' I found an Ebay Garrett GT3782 that was on a Navistar DT466E and cut the exhaust housing flanges off and welded on a divided T3 to the T4 1.11A/R housing along with a 3" Vband. Nickel 55 rod with lots of preheat, post heat, and slow cool.
I put it on the dyno and it put down right at 500whp with very slow spool compared to the GT32 which I expected. Don't get me wrong, I like the additional power, but on the street fast spool is much more fun. The dyno plots below are both 3rd and 4th gear runs on the same plots.
I just swapped out the GT3782 project for a Tims's Turbos built HX35/40 with the 7-blade HX40 60x84mm compressor and the HX35 12-blade 70x60mm turbine. I have not returned to the dyno but spool is nearly identical with less top end. Any insight on whether this is expected with the Holset hybrid?
I am just puzzled that the 12cm^2 divided housing driving a smaller 70x60 turbine spools up nearly identically as the 1.11 A/R T4 housing driving a 72.5x66 turbine on the GT3782? In 4th gear datalogging shows only a 200rpm advantage to the Holset. In 1st through 3rd there is no advantage and like I said seems to run richer at the same boost 28-29psi with no fuel changes and speed density. Fuel is E85 (likely more like E50-E60) that I have not measured the percentage yet.
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