SC Turbo Shakeout Issues

patkeefe · 05-26-2011, 06:58 PM

I have the engine done and the new turbo bits in. I have driven the SC a few times in the past couple of weeks. Today, I put about 100 miles on it, to start shaking it out.

I have these few issues:
I have a diverter valve,which starts whistling at about 2PSI boost. It is a replaceable spring model, and I tried all three springs...maybe I just need a stronger spring. I will think of the manufacturer in a minute. It did the same thing with my Bosch Audi diverter valve, but it did not do this with the old Rajay turbo setup. That freaking whictling is annoying.

I have a severe lack of decel. I am guessing vacuum/boost leak (which could also be the source of the whistling above). If I put the clutch in, the revs drop off to about 1000 RPM (idle), but if I simply stay in gear, I don't get any engine braking, which Iwould expect to have.

Otherwise, the Borg Warner turbo is good. Not digital like the old setup, this just produces power over the entire band, it seems. The thing makes boost as soon as it sees load. One other issue: my Tial 38, which has a 5.8 PSI spring in it, will allow me to keep boosting to almost 10PSI. I think the wastegate may be too small, although I believe this BW turbo, a T04B, is very similat to the old Rajay.

The BL WUR is very touchy, and temperature dependant. The entire CIS is just so finicky, bu, I have an SC setup, and not a 930 setup. Fundamentally the same.

Pat

drmatera · 05-27-2011, 09:58 AM

can we see some pics of wastegate location..? Have you verified that the spring is infact a 5.8psi? pop the top off the gate and let us know what color spray paint is on it. Also Tial serial numbers all their stuff so a quick call to them will get you all the details unless someone has been inside it already. I sell Tial stuff, if I can help you indentify anything let me know

patkeefe · 05-27-2011, 05:57 PM

I bought this new a few years ago. I will look at the spring this weekend, but I am quite sure it is a 5.8, which should be the smallest pressure spring I could get from Tial. I have these headers now, prior config was with stock SC heat exchangers and WG was located on the cat delete tube on the way to the turbo. This configuration is not a real straight flow to the WG.

drmatera · 05-27-2011, 11:00 PM

That looks similar to the factory 930 wastegate routing so I don't think that's an issue. I would wait to verify the spring before anything else. Does the boost continue to climb as rpm goes up or does it level off ?

Homegrown · 06-01-2011, 03:18 PM

Hii patkeefe!

According too the pics above it seems that the WG just evacuates exhaustgas from the left cylinderbank, either move wg till joint at turbo or put another on the right pipe too.

Best regards Stefan

patkeefe · 06-01-2011, 06:02 PM

Stefan:
That is not a really great photo. It is like a 930 exhaust in that it is routed the same/ It gets both banks of cylinders. Lawn tractor rebuild has interfered with the turbo issues!

drmatera, I have been looking at the old maps, and determined that my old Rajay T04B V trim has just a tiny bit less mass airflow capacity than this BW T04B H trim. The BW has .70 A/R on the turbine side. I also have an analog SW boost gauge, with a tube run up to the dash. It also now has a tee in the line so I can get boost pressure to the MSD Boost Controller, which may affect the readings. Like I said, the tractor is in back of the car with no carb; the car been down for 30 months, and the grass is relentlessly growing.

drmatera · 06-01-2011, 08:01 PM

That's not a chambered muffler ie: flowmaster is it?

Changing turbine housing size may cause a slight change in boost but should be minimal. Sounds like you have the right tools in place for diagnosis. Good luck with the mower too

patkeefe · 06-02-2011, 02:21 AM

Flowmaster series 44, I believe. I didn't want to cut up my piping with the M&K welded in, in case I ever sell the old setup. Is the Flowmaster not a good selection? I got it because it fit, and was 3" in and out.

drmatera · 06-02-2011, 03:26 PM

chambered mufflers and turbos are not a good match. I've seen 500hp turbo cars pick up 40+hp by going to a straight through design (DynoMax Ultra-flow or Magnaflow) muffler.

patkeefe · 06-12-2011, 07:56 AM

drmatera:
I finally had a chance to get at the Tial. The spring is 3-1/4" long, and seems pretty stiff. The diaphragm was pinched a bit in two spots; I may have done that myself a couple of years ago, but I can't remember (memory is the second thing to go!). The diaphragm seems intact and not punctured. I would appreciate your thoughts.
Thanks!
Pat

drmatera · 12:15 PM

Pat, Thats a "small red" spring. According to Tial it's 5.8 psi but in my experience they rate them a bit low so it's possible to see 6-7 psi with that spring.. Now with that said I think the pinched diaphragm could be your issue as it's may not allow the valve to travel its full range which in turn could cause boost creep. If the dia is not punctured reassemble the gate carefully and see what you get. If you need a replacement diaphragm I have them here

JFairman · 06-12-2011, 12:40 PM

If you put it back together with that diaphram, a little silicone grease smeared on the side of the now semi folded diaphram will help it slip up into the bell while you push down on it to compress the spring and get the bolts started.

good luck with it.

patkeefe · 06-12-2011, 04:08 PM

Thank you, gentlemen!