.8bar Tial with B&B yields .8bar

[rooked 930]

Hey all,

Trying to stay on the safe side of life, I just replaced my stock wastegate (w/1bar spring) with a Tial (w/.8bar spring). I've read a seasoned Pelicanite's multiple posts regarding the results of running a Tial with B&B headers as causing higher boost than the Tial's spring is rated.

Before installing the Tial, I testing it on the bench and it seemed very accurate at .8 bar.

Results: Running a fair number of tests with the new Tial, the stock boost guage flys up to .8bar and sits there. Solid. Not even a flash past .8bar. With the stock wastegate, I would see the needle fly a little past 1bar and then sit at the 1bar mark. The seat-of-the-pants test also tells me that it isn't quite the same as before.

I know that the stock guage isn't considered particularly accurate, but this threw me a little. I don't think investing in a more accurate 935-style vac/boost guage is a bad thing, but I didn't plan on it right now. However, changing to a 1 bar spring without better data/detection bothers me a little as well.

Anyone else get similar results? I think my setup is fairly common.

Here's the gear:

K27-7200
Tial 46mm wastegate w/.8bar spring
Kokeln I/C
Zork tube
Stock boost guage

Cheers,

Rob
79 930

[930LDR]

If by stock boost gauge you mean the one built into the tach... then I wouldn't feel too confident with your preliminary observations. Those stock gauges are notoriously inaccurate. I'd install a 3" gauge in place of your clock before passing judgement on either setup.

With my K27HFS and B&B headers... .8 B spring in my TiAL was earning me plenty more than 1.0B. I finally installed a .5B spring and an EBC and have been able to dial in perfect boost.

[David]

I'm running a Tial 46mm with a .6 bar spring and B&B exhaust. Before I got my boost control valve working, I was seeing 0.7 bar from my MAP sensor, so the wastegate and B&B could bleed enough to get down to .7 bar.