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Join Date: Dec 2004
Location: Danville - CA
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RPM Fuel Enrichment Trigger Installed

Works like a charm. Really great product and very good directions.

Unfortunately I didn't have a ton of time to play with the various rpm trigger points as the Fiance was not having anymore of me playing with my toys at the shop.

I know that you want to be in the low 12.0s at full boost and high RPMs but what is a reasonable AFR to be at in the 4k - 5k RPM range? I am seeing 13.0 right now prior to enrichment kicking in and it dropping down into the low 12s.

I need to play with the adjustable WUR this weekend but was curious whether or not slightly higher AFRs in the mid range was acceptable.

I think I may try adjusting the mixture screw on the fuel head first as it is easiest to get to... not sure if that is going to make a difference though.
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Rob Montgomery
'88 Blk/Blk 930 ('Lucy') - Not Stock & Not Running
Old 05-31-2007, 06:45 PM
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Crotchety Old Bastard
 
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What instrument are you using to measure your A/F ratios?
Do you have a precise way to measure and record boost vs RPM in all gears and situations?

The reason I am asking these questions is that in order to optimize the RPM trigger setting you need to know the absolute lowest RPM that your engine will see 0.4bar of boost. That RPM will change given variables such as ambient temperature, what gear you are in, and intercooler efficiency.

Once you know that target RPM you can set your trigger and lock everything down. It's a crude device but it does reduce the enrichment spike that can hit in the 10's for some engines.

To directly answer your question, 13.0 @ 4000 rpm is probably OK. That is where mine is at as well. By 5000 rpm you should be in the high 11's to low 12's and stay there to redline.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 05-31-2007, 08:02 PM
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You mentioned "adjustable WUR". Did you get that from Brian Leaske with the enrichment solenoid kit?

I think Brian Leaske sets the WUR boost enrichment trigger pressure somewhat higher than stock, the trigger point and the amount of enrichment are both adjustable on his modified WUR.

Please post detailed information about your experiences setting it all up, be very interested - my solenoid is in the car but not hooked into the WUR until the bottom end is completely run-in and I get it on a dyno and can monitor the AFRs properly/set it up.

+1 on the instructions being very detailed, well-written & illustrated.
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'77 S with '78 930 power and a few other things.
Old 06-01-2007, 04:21 AM
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I am using a permanantly mounted wideband in the dash to monitor AFRs. No good way of pinpointing exactly when I hit .4 B of boost.

I do have Brian's adjustable WUR which in and of itself made a huge improvement in a lean condition I had previously been experiencing at high RPMS (5.5k +).

The install was straight forward of the solenoid. Take your time cutting into the pre-existing wiring and know in advance that you need to pull off the intercooler to reach the mounting point for the valve and you are all set.

I took it out initially with the 4200 chip installed and found that I was dumping down into the high 10s when enrichment kicked in. Installed the 4400 chip and found slightly better AFRs but noticed that up until the point of enrichment I was running at 12.8-13.0 (maybe that isn't all that bad).

Car is DEFINITELY more responsive in the midrange. Previously I had to dump into the real low 10s somewhere in the high 3000 RPMs in order to maintain decent AFRS on full boost at high RPMS.
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Rob Montgomery
'88 Blk/Blk 930 ('Lucy') - Not Stock & Not Running
Old 06-01-2007, 05:25 AM
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Crotchety Old Bastard
 
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It sounds like you have adjusted the WUR pressures and are using the PRM trigger only to alleviate the enrichment spike. In that case it does not matter when you hit 0.4bar, that area is already taken care of.

Out of curiosity, why were you not able to smooth your A/F ratio throughout the RPM band by WUR adjustments alone?
How much power are you pushing and at what boost level?
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 06-01-2007, 10:27 AM
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Maybe just not enough fudging around with it but it seemed as though all I could do to get a reasonable mixture at full boost and redline was thicken it up to the point of low 10s at onset.

I would guess I am somewhere around 400hp. Running 1.0B.

CIS, 3.3L, cams (unsure of which), K27HFS, Kokeln IC, Fuel Head, Headers, Exhaust... normal bolt on stuff.
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Rob Montgomery
'88 Blk/Blk 930 ('Lucy') - Not Stock & Not Running
Old 06-01-2007, 01:19 PM
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Wow... after a little adjustment of the mixture this weekend and playing with the boost controller this morning... my car is running better than I have ever experienced.

Can't say enough about Brian's products. Watching the wideband through the RPM range is like night and day from where I started last spring.
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Rob Montgomery
'88 Blk/Blk 930 ('Lucy') - Not Stock & Not Running
Old 06-04-2007, 12:20 PM
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