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Post by tutulate on Jan 26, 2018 14:49:03 GMT -5
Hi Shannon, I wanted to move this to a more relevant thread, so here it is! I have been fighting the flu bug, and the info I posted in the "Catch Can" thread was wrong.
My 1986 SVO's build: Stock except for- 8UA eec-iv/ 3" Stinger exhaust with high flow cat and Spartan wideband/ Delta RR regrind set at -1* via NeedHP adjustable cam gear/ Kirban AFR set at 46lbs base/ Walbro 255lph high pressure pump/ Blocked off EGR/ Manual Boost controller set at 15lbs/ Stock head w/ new valve seals-Comp Cam 990 springs shimmed to 125lbs seat/ 2004R automatic trans w 3700 stall TC.
Conditions: Idle in park: 1200+ RPM/base FP= 46/ 39 with vacuum connected/ 19"hg = AFR bounces around 12 to 15 Idle in gear: 900+RPM/ 16"hg= AFR still bounces around. Vacuum gauge also vibrates +/-2"hg Vacuum at decel: 24"HG= AFR 20 Mild throttle: vacuum to 5 lbs boost= AFR 14.7+/- 5 to 10 PSI= AFR 12-13 15 PSI/WOT= AFR 11.5
When I originally set the Kirban, I used the Schrader valve at the firewall. It read a couple of pounds higher than today when I re-set it using the fuel rail Schrader valve. I increased the pressure accordingly.
Does all this look good? Is the base to vacuum-connected Fuel pressure drop ok? I am pretty sure the vacuum vibration at idle may be due to valve seat leakage, which I will correct when I rebuild my backup head that has been Mag'd without cracks.
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Post by Stinger on Jan 26, 2018 15:54:32 GMT -5
It all looks good except the idle AFR should only bounce around in the 14-15 range (average of 14.7:1), and of course the gauge shouldn't vibrate but you know that.
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Post by tutulate on Jan 26, 2018 15:57:06 GMT -5
Where should I look for the cause of the Idle bounce? Could it be a warm-up issue?
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Post by Stinger on Jan 26, 2018 16:04:26 GMT -5
If it's entering closed loop then you should notice the idle AFR go from being steady to bouncing when the temp gets above 170 or so. Open loop fueling is more stable while closed loop goes above/below the 14.7 target very consistently.
So first you need to determine if it's entering closed loop, then depending on if it is or not, move to the next step.
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Post by tutulate on Jan 26, 2018 16:06:01 GMT -5
How do I determine Open/Closed loop?
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Post by Stinger on Jan 26, 2018 16:29:19 GMT -5
Measure stock o2 voltage while at warm idle, or pay attention to whether it does what I stated above.
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Post by tutulate on Jan 26, 2018 17:34:28 GMT -5
DOH! Dumb me figured it out! When I first start the car, I get a solid, steady reading anywhere from 12.5 to 16. Usually it is 12.5 to 13.5. It stays steady at whatever number. Then, once the car warms up, the reading varies from 14.3 to 15.5. I was thinking it was a delay in the wideband reading the exhaust. It is the change from Open loop to Closed loop.
So,... in reality it doesn't vary between 12 to 15.5, but rather 14.3 to 15.5!
Thanks for your help, Shannon.
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Post by Stinger on Jan 26, 2018 21:13:08 GMT -5
There you go, sounds like it's acting as it should.
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Post by tutulate on Jan 29, 2018 18:19:40 GMT -5
I hope you don't mind, Shannon, but I have some follow-up questions about how to set the proper fuel pressure.. I am running an 8UA with the stock brown top injectors. The stock base FP is 38, and I increased the Kirban to 46 base. My mpg is down to 16 from the previous 20. Today I turned down the FP to the stock 38, and the WOT AFR( at 15 psi) was lean to the tune of 12.6. I then increased the FP until the WOT AFR is 11.5. That gave me a base FP of 44. Does this sound like the correct way to adjust the Kirban? Other than my enjoying my new found power, what could cause the mileage loss? I tried to check codes, but I get a communication error, so I think I may have a 5v reference, or ground issue when I swapped in the 8UA.
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Post by Stinger on Jan 29, 2018 20:53:39 GMT -5
Raising fuel pressure increases the effective size of the injectors. The ECU has no way of knowing you're increasing injector size/flow so it keeps on assuming they are stock. Once you get outside of the range that the ECU can adjust for via o2 sensor correction (10% I believe) then it can no longer pull enough fuel out of it to keep it at the proper AFR at idle/cruise and your mileage suffers. This is the same reason people who run 42lb or 46lb injectors with the stock ECU have the same issues. It works fine at WOT because the 02 sensor and VAM are ignored so you get a direct correlation between fuel pressure and AFR.
If you had a 5v or ground issue it wouldn't be running at all (or very poorly) as all of the sensors would be giving false readings.
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Post by tutulate on Jan 29, 2018 21:19:11 GMT -5
hmm... 1) What could be causing the lean WOT condition with 38psi base FP? 2) What could cause the 8UA to not send codes to the reader? "Vehicle not communicating" I am using an AutoX 7000
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Post by Stinger on Jan 30, 2018 1:14:11 GMT -5
Anything that increases airflow through the engine will lean it out. So in your case it looks like exhaust and the cam are the airflow mods. If you've got any other mods that you forgot to mention (cone filter for example), that would contribute to it as well.
The other side of it is old injectors that aren't flowing what they once did.
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Post by tutulate on Jan 30, 2018 10:56:54 GMT -5
NOW I get it!! So, in my case, due to the exhaust, cam, and KN filter, I have to increase the FP to get it to run right? This is because the 35s don't flow enough for the setup? The next move to regain the efficiency would be to use a PiMP or other ECC in order to change the the fuel table strategy? I also need the larger injectors which should will match the flow needs better. Would that improve the MPG?
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Post by Stinger on Jan 30, 2018 11:27:50 GMT -5
You got it.
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