IPSC

I did a dyno run today. I mixed up my fuel some 93 some 100 to come up with about 97 octane to try some 18 PSI runs. At 15 and 16 PSI the indication was completely solid. At 17 to 18 PSI the boost gauge fluctuated about 1 PSI so adjusting was a bit of a chore. One of the guys at the shop said every boost gauge he had did that.

Now here is the weird part (and NO I don't have the charts to post yet and yes they would help a great deal) there was fluctuation to both the HP and TQ lines... in 4th gear AFTER the 3700 rpm mark to redline. 3700 is where Tq maxed out.

I did a pull in 3rd gear (just because the Dyno shop guys wanted to see) and it was smooth... Of course I was running out of time and did not watch the damn boost gauge on that run so I am not sure if it fluttered then as well. Afterward I backed it back down to 15 PSI (we only have 91 here in Idaho and I was nearly out of my 97 mix) and back to a solid indication.

Anyway, I made 298.4 HP and 305.7 TQ. AFR still a bit rich in the 11.1 to 10.9 range. OF COURSE my fuel pressure gauge **** the bed on me just after the first run so any adjusting of the fuel pressure would have been a shot in the dark.

Any ideas?

IPSC

Chris Prack

What is on your engine? It could be as simple as wastegate is fluttering. Do you have the OE style bypass valve or are you running a blow off?

IPSC

Oh a bit of background would help wouldn't it.

Engine mods:
993 Billet diverter valve,
LR vacuum lines,
AFPR, Rail Mounted Fuel Pressure gauge,
LR Hard-pipe,
Stage 3 Saikou Michi 951 Catch-can,
Tail 38mm Wastegate, (run in single port mode)
Bleeder valve MBC (Inline Pro)
3 inch exhaust with Spintech muffler,
Vitesse MAF,
Vitesse supplied 72lb injectors with Ballast Resistors,
Vitesse STAGE 3 TURBO,
Vitesse Chip Board.

When I pull the intake I plan to check all the grounds as you suggested.

IPSC

special tool

Wow - this is TEXTBOOK single-port Tial problem.

Put a dual-port MBC or EBC on your Tial, and that will stop.

Also - you should put a heavier bypass on the car with that turbo.

IPSC

Ahhhh So the Tial really needs to run in dual port...

Will the boost sciences "Black ****" MBC work in dual port with the Tial?

Suggestions on a replacement BOV? Is this one so small that I am (shudder to think) back pressuring the turbo?

Thanks,

IPSC

xsboost90

im running that wg w/ a black **** lindsey MBC and it has no flutter at 18psi in dual port.

JE_951

same. Tial 38, LR black **** with rock solid boost at whatever its set at (10-20psi)

xsboost90

what does the boost science MBC look like - isnt it like this one? This one looks just like my Lindsey unit.