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After much frustration, gnashing of teeth, rending of clothes, etc, I
finally installed the upgraded, rebuilt turbo in the Abbottized '97 900 SETC last Thursday. Stock unit is a Garrett T25. As you may recall, I killed 2 of those in a whisker under 60K miles, this second failure coming only 20K after the first. After receiving and contemplating making a T3 fit at great additional expense, what I finally landed on was machining the inlet and outlet housings of the stock Garrett and putting in bigger T28 wheels. Unfortunately, the bearing housing was also trashed due to the "massive thrust failure" (per my turbo guy) that croaked the stock turbo in the first place. So, new bearing housing, with 360 degree thrust bearing to go along with the better flowing exhaust side SHOULD improve the lifespan of the turbo.
The result: After a week of driving with the new and improved model I have
this to say
[Homer-esque] booost :))) booost :))) booost :)))
The butt dyno detects marginally more lag than before. It's there, but hardly even worth mentioning. More importantly, there seems to be
dramatically more torque from the mid-range all the way to the redline. In a straight line with foot to the floor in 2nd gear @ 18 lb of boost, when I
get to ~3900 rpm the chassis and tires are overwhelmed, and a drivewheel
loses traction. That's with the 215/45/17 Bridgestone S02's, the stickiest
tire I've ever drive. That didn't happen previously. Also, the Abbott poly
control arm bushings are again beginning to lose the torque steer battle as
traction varies from wheel to wheel due to pavement, weight distribution,
etc. I'm going to drop the front tire pressure 2 psi which should help. With the revs over 3K in any gear, touching the throttle produces prodigious amounts of torque RIGHT NOW. It's wonderful :) I'm trying to find someone nearby with a chassis dyno, to empirically see what I've got. But it sure feels like more than the 230hp/258 lb ft a Viggen has.
Opening up the exhaust side of the turbo has made a would of difference in
boost performance at the high end also. There have been a lot of jabs at
Abbott's tuning on TSN for the way they raise the base boost. I now believe
those criticisms are justified. The stock T25 turbo cannot flow enough air
on the exhaust side at high boost to allow the APC to do its job. With the
stock turbo, the calibrated boost gauge would stay planted at max boost,
with some efficiency loss falloff near redline. Now, I can see the APC doing its thing, as the boost wavers +/- 1 psi as the Trionic actually regulates the max boost, all the way to redline. The wastegate is actually varying its opening and closing to regulate boost, whereas it was stuck at max open (limited by the high base boost setting) with the lower flow exhaust side of the stock T25 turbo.
For now, I'm EXTREMELY pleased with the results of this upgrade. While
expensive for a rebuild at $830, performance and cost-wise, I think it's a
winner. A stock rebuild would have been ~$575 with the bearing housing I
think, so the incremental cost of <$300 is money well spent for the
performance benefit. However, the true test will come 20K miles from now and beyond...
Dan
posted by 24.147.56....
, Sat, 22 Dec 2001 10:51:22, Fri, 21 Dec 2001 09:20:34, Fri, 21 Dec 2001 10:59:57, Fri, 21 Dec 2001 12:57:19
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