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aerochip aerochip is offline
Registered User
Join Date: Jul 2012
Location: Park City, UT
Posts: 79
Tuning, AFR, Altitude and More Questions

Iím trying to get my car dialed in while not blowing it up after last yearís top end rebuild. I am having two issues:
First is that I canít seem to get consistent AFR readings and second is that it wonít build more than .6bar boost.

Car is setup as follows: 1985, black fuel head, stock 3LDZ turbo, stock waste gate, stock intercooler, stock heat exchangers, no emissions including no catalytic on what I believe is a Borla exhaust. Included in the pile of money I sent to Pelican, I replaced all vacuum lines, replaced injector blocks with stock due to cracks and erosion, rebuilt stock bypass valve, installed aftermarket PLX boost sensor on intermediate manifold (used port where decel valve used to live) and PLX wideband AFR gauge approximately 18Ē from end of tailpipe. I also have some kind of adjustable WUR - it was there when I bought it.
Black Euro Fuel head at 6.5 System Pressure (up from 5.9)
Cold Pressure: 2.1bar at 75 degrees
Warm Pressure: 3.4bar
Cold start: Idle AFR at 10.4 on start and rising to 14.7 on warm engine
Enrichment: Full boost of .6bar yields 10.3 - 10.8 AFR
Cruise: 70-75mph, slightly in boost, .05 - .1 bar, 14.2 - 14.5 AFR
Warm idle: 14.5AFR
Decel from cruise: 15 - 16 +AFR.
Correct me if Iím wrong, but these numbers seem okay. Where I get confounded is when I park for pretty much any length of time and the motor heat soaks, I start it back up and it idles rich again at +-12AFR and sometimes with an idle speed of 1200 RPM. As I drive it again, it seems to run a bit leaner with the idle AFR eventually running over 15 and the cruise AFR 14.5 - 14.8. Enrichment still runs into the 10ís and boost is remaining at .6bar.

Some of my thoughts:
Iíve checked and believe I have sufficiently tight intake and exhaust systems without any leaks.
My Ďadjustableí WUR has been very finicky. I can tap or back off the pin on top to get it to an exact warm measurement and when I test it again, the measurement is different. Maybe this is the culprit? Would a rich AFR on a hot engine cause the idle to run high? Iíve tested the AAV and it appears to work as its supposed to, but should I pinch this off to take it out of the equation?

I believe my timing is correct, but if the distributor wasnít advancing/retarding as it should, would this cause any of these problems?

Regarding the .6 boost issue. The waste gate is consistently gassing off at .6bar in every gear. I didnít have the PLX boost gauge prior to the rebuild but I thought I made closer to .8 per the stock gauge, which reads pretty much identical to the PLX gauge, just not nearly as instant. Would I be crazy to cap the waste gate to intercooler for testing purposes to see if I can carefully make .8 bar? Are there real performance gains to be had from .6 - .8bar?

One closing question. I live in Utah at 7,000í feet and frequently run this car between 4,500' and 8,000í and sometime up and over the Continental Divide at 10,000í. Iíve read somewhere about an altitude compensating WUR and was wondering if I should consider this or if it doesnít matter because I am theoretically running consistent air volume via boost? Come to think of it, the last question may only be true when running on boostÖhmm..

And a final piece of information regarding the PLX system; their Kiwi wifi system is pretty slick but not perfect. I show boost and AFR in one handy iPhone screen but it cuts off if you run bluetooth for music of phone calls in the background, which is annoying. I was hoping to have an all-in unit information and entertainment unit. I replaced an AEM-Xwifi unit because I wanted both gauges in one iPhone screen. The AEM unit would run the bluetooth in the background; they just didnít have a boost gauge to integrate into the system, which is more important to me than the entertainment. Let me know if anybody wants the AEM - Iíll make you a great deal on a unit that has been used less than 500 miles.

I appreciate any input from the experts and canít say enough good things about the Pelican community, esp this 930 board.

Old 05-28-2014, 04:08 PM
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