Just out of curiousity.. BTM? Prom tuning? '749?

I'm trying to figure out what i need to do with my timing on the 3.1, with the MAF setup. Also, for you FI MAF guys, How far from the turbo is your MAF? Mine's hooked almost directly to the turbo - and I think it's messing up my air flow through the MAF...

 

I have two turbo Chevys.

My TT 89 L98 has base timing set to +4°, with an MSD BTM set to pull out 3/4° per pound of boost (on 93 pump gas anyway). I will probably reduce the boost retard if I ever run race gas. It uses a MAFS mounted far aft the turbochargers. The turbos pump into IC cores mounted down in front of each front wheel, then they system Ys together to enter the MAFS just before the TB (its hard to explain- see the attached pic). My MAF is pressurized, as you can see from the pic.

My turbo 2.8 in my 89 Z24 has no timing mods. I figured since GM tuned it to run on low octane fuel, it should handle 6psi without detonation if I run premium pump gas. No detonation shows on my data-logging scan tool at 6psi. However, I have a second stage of boost (10psi) that detonates slightly at the very top end of the powerband (5500rpm). I ran the stage 2 boost at the local track and got a 13.9@99. I was happy with the results, considering the engine (and the rest of the car for that matter) is totally stock with 178k miles!

 

As long as your on the low pressure side of the turbo you shouldnt have any problems getting good data.

 

Why must you be on the low pressure side of the turbo?

 

'89, which maf are you running? the stock plastic one? I didn't think they'd handle being pressurized....

 

Stock plastic MAF. It has held up to several test runs at 10psi with no problems. I was unsure myself if it would work, but it appears to be fine. I had approx 5k miles on my turbo system before I started the restoration project.

 

Ive seen mafs operate improperly due to the heat on the pressure side of the turbo.

 

Fortunately I havent had problems yet. Maybe since my system is intercooled and the MAF is far from the compressor outlet. I also haven't removed the heat-sink from inside the sensor to improve flow like some guys do- so that may be a benefit as well.

 

Ive seen mafs operate improperly due to the heat on the pressure side of the turbo.

ATI's design on a third gen places the MAF on the pressure side. I have not had any problems in three years.