Thread: gpopshop.com Big T28 Upgrade

yeah but to me it looks like those wheels are 2871r wheels, and he has a new center section too (is it a ball bearing one?) Therefore its basically a 2871r in a t25 housing if i am not mistaken.

Eric set me up with some time at Dyno4mance a couple of weekends ago. Andrew did a great job, the car feels awesome. Dyno4mance uses a Dyno Dynamics (the heartbreaker), so on Friday, I took it to Air Cooled Classics for a few runs on the Dynojet to satisfy my curiosity.

The ACC guys were pretty cordial, but at the same time it was clearly a get on-> get numbers-> give us our money-> GTFO operation. I was in and out in like 20 minutes, lol. They f'd up the RPM scaling (I was running to 7k and I know the tach isn't that far off) and I don't know WTF was up with the wideband. I'll trust that Andrew's A/F numbers are correct.

Dyno4mance (Baseline)- 216whp/187wtq
Dyno4mance (+boost/tuning)- 231.4whp/208wtq
Air Cooled Classics- 258.87whp/255.3wtq

Overall, I'm really pleased with my tiny turbo. I was hoping for 250-275 whp and I ended up with almost 260. The T25/T28 with the bigger wheels still seems to drop off boost just about as bad as a normal T25, likely just the limitations of the housings. If you look at the HP/TQ/Boost/AF overlay, peak whp is actually at ~12psi or so. Even though it loses boost, it's got a really nice power curve.

I must have missed it? How many psi were the runs done at?

I spent $50.00 more then Swiss did on the same rebuild, but I got mine back the same week. I really didn't want to wait. So he's not the only one who may of overpaid.
Swiss the turbo looks very good. My car will be dyno'ed this coming monday so I'll post up some graphs.
Now thats its a t25 with t28 internals, can't you run more boost? I have had my t25 at 10psi, I plan on taking the hybrid to 15psi.
BTW the white b14 in the pics is looking so sweet and clean.

It's on the second and third charts in the post above. The third chart is just the first and second charts superimposed on one another. Nothing was changed for the Dynojet runs. Edit- fixed the size, so they are a little easier to read.

My baseline was at 10-11ish and we turned it up as Andrew started tuning. We ended up with it spiking to 14, but falling prety quickly to 12. It doesn't hold 14 very long, so peak power was made with the turbo at about 12psi. Andrew (the Dyno Dynamics guy) uses 3rd gear, but the shop where I did the Dynojet runs uses 4th gear. It holds boost a little better in 4th, so you can see it makes more torque on those 4th gear runs.



I've always heard that when the torque starts catching up with the hp, you should back off. On the Dynojet runs (4th gear), my torque is right up there with the HP. That was at 14psi then trailing off. Give 15 a try, but if you find you're making more torque than power, I'd back off.

What do you use to set your boost? NIce numbers though with what your working with!

It's just a Hallman MBC. I accidentally bought a non-RX which sucks. If you're going to buy a Hallman, always pony up the extra dough for the Pro RX. It's got a better spring and lightweight ceramic ball.

If you look at the boost chart up there, on the baseline it's got a really jagged line. Bruce at the shop figured out that the crappy metal ball in my non-RX was sticking. When it gets too hot, it expands and the ball gets sticks. The ceramic ball doesn't have that issue. We moved it away from heat (from the radiator support to behind my air filter) and that solved the issue. Notice on the final run, the boost line isn't jagged.

I could probably get a little better control with a fancy electronic boost controller, but I’m pretty sure it would still drop off in the higher revs anyway.

Good advice, I may buy a used hallman boost controller, is thier anyway to tell the difference between an RX and non-RX?

I don't think there's any way to tell from the outside, but if you take it apart, you can tell the ball is ceramic.