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Controlling the boost on set to the WUR



I own a 1992 964 turbo. Basically stock. It has a cat delete and manual boost adjuster. GREEDY. I had my WUR Rebuilt to stock specs. My AFR's at onset boost is to low and to rich through the rev range. it dips down to 10.1 afr at boost onset and only gets to 11's at higher RPM's. I'm running 0.9 bar boost.

I know the I could tap in the brass disc under the WUR and by doing that I could affect the WCP. which is a PITA taking all the stuff to get to the WUR to make adjustments on a stock 964 turbo. I have this Idea, not sure it would work. and I would like your thoughts, please.

I was thinking I could use and manual boost controller on the vacuum line going to the WUR to control the pressure going to the WUR just a tad. they for less pressure less onset boost and a little leaner at onset enrichment. Do you think this would work?

Helio

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1986 944 turbo -first car
1997 993 Cab 6 speed-sold
1992 964 C2 turbo
SOLD, 911GT ,CIS, 428 fwhp 450 trq, Carrillo rods, 964 cams, TT retainers,7.5 comp 1.1 bar boost 320 ml black fuel head 009 injectors, 044 pumps, 60-1 T4/T3 dual scroll turbo

Last edited by heliolps2; 10-10-2020 at 09:38 AM..
Old 10-10-2020, 09:33 AM
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Several folks have used a Zeitronix to trigger a pierburg solenoid to do what you’re talking about. Brian Leask makes a RPM switch to hold off boost signal to the WUR until a set RPM, usually 4000RPM or higher. Google that kit.
I’m sure a MBC could be configured to do the same somehow. The issue though is you might full boost at 2600 and still not want the WUR enrichment yet... the MBC doesn’t have a RPM reference.
You’d be in the minority though of folks who use these without an adjustable WUR in the first place. Twiddling with the adjustable WUR can really add a level of driveability you haven’t experienced yet.

And yes it sucks to get at the WUR.
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Old 10-10-2020, 10:47 AM
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Short answer is yes.
I've used manually adjustable boost controllers for this purpose. Extremely simple and cheap. Tuning is the same as you've done with your old adjustable WUR, monitoring fuel pressure and AFR. Setting at 0.6bar seems to be a good starting point. The problem with this method remains that the fuel dump is not actively adjusting to the needs of the engine, but it does help. The time spent at this boost level is typically brief. Also there is a slight enrichment in the absence of vacuum which helps the transition.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 10-10-2020, 01:08 PM
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Quote:
Originally Posted by RarlyL8 View Post
Short answer is yes.
I've used manually adjustable boost controllers for this purpose. Extremely simple and cheap. Tuning is the same as you've done with your old adjustable WUR, monitoring fuel pressure and AFR. Setting at 0.6bar seems to be a good starting point. The problem with this method remains that the fuel dump is not actively adjusting to the needs of the engine, but it does help. The time spent at this boost level is typically brief. Also there is a slight enrichment in the absence of vacuum which helps the transition.
Hi Brian,

Thank you. I just wanted to add 12 inch piece of vacuum hose and put the manual adjuster with out having to take everything apart, If this helps things, I would need the Wur on set enrichment boost adjusted, I'm sure that it was set on the rich side when it was rebuilt,

Do you mean absence of pressure right ?
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1986 944 turbo -first car
1997 993 Cab 6 speed-sold
1992 964 C2 turbo
SOLD, 911GT ,CIS, 428 fwhp 450 trq, Carrillo rods, 964 cams, TT retainers,7.5 comp 1.1 bar boost 320 ml black fuel head 009 injectors, 044 pumps, 60-1 T4/T3 dual scroll turbo
Old 10-10-2020, 02:27 PM
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you need to check the fuel pressure on boost.
with gauges connected and pumps running, put 15psi into the WUR.

you could have an air leak on the pressure side.
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Old 10-10-2020, 06:05 PM
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I actually did mean absence of vacuum. There is a slight enrichment when the engine goes under load and the vacuum signal decreases going to zero. Assumption is that you have checked the vac/boost port and it is functioning properly. OE specs are on the rich side.
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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 10-11-2020, 04:27 AM
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Quote:
Originally Posted by RarlyL8 View Post
I actually did mean absence of vacuum. There is a slight enrichment when the engine goes under load and the vacuum signal decreases going to zero. Assumption is that you have checked the vac/boost port and it is functioning properly. OE specs are on the rich side.
Hello turbo friends,

Brian. The factory calls for idle to be set citing the old fashioned parameter of 3% CO at 950 rpm with the O2 narrowband sensor unplugged and the air pump defeated.

The factory calls for those values with cat installed, How much would the afr's readings be affected with the cat deleted? I would assume it would read richer without a cat. The last time I checked my AFR's was a couple of years ago with my cat installed, If I remember correctly the idle and warm cruise AFR's were around 17.1 with the 02 sensor plugged in and with the air pump plugged in as well. My memory is foggy but I believe that the AFR number might have been even higher. Like I mentioned before I don't have a full-time AFR gauge. Today I did some tests. the car was cold not driven in a couple of days.

1. The car has no cat. Fabspeed bypass
2. K&N air filter
3. adjustable manual booster set at .09 ish bar
4. RPM's 950
5. I unplugged the 02 sensor
6. Unplugged the air pump.
7. I hooked my handheld Innovate AFR meter.
8. Cold start. began with 10.9 the quickly rose to 13.5
9. Warm cruise with 02 unplugged. it was between 14.1 to 14.5
10. Once warm idle was 13.6. I went for a drive and I did third gear pull on the 66 hyw. The AFR's went from 14.5 to 11.5 to 12.8 AFR's at 6500 rpm's then down to 12.2 when shifting to 4th gear the AFR's began to raise slightly. I let off at that point. II didn't want to go to jail.

I went home and plugged the 02 sensor back, but I left the air pump unplugged.

A. Warm Idel now at 14.7 AFR
B. Warm cruise 14.5 to 14.7 depending on load
C. went for another spirited drive. again in third gear, cruising at 3000 rpm's. At full throttle, the AFR's went from 14.7 to 11.5 to 12.8 AFR's at 6500 rpm's then down to 12.2 when shifting to 4th gear the AFR's began to rase slightly.
D. Now I did this in fourth gear cruising at 3000 RPMs. I got on the throttle and the AFR's dropped to 10.9 for a second and the AFR's quickly raised to mid 11's into the 12's and let off.
E. No signs of black smoke.

My conclusion is, All is normal Unless someone has a different opinion. I welcome your thoughts.

Helio

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1986 944 turbo -first car
1997 993 Cab 6 speed-sold
1992 964 C2 turbo
SOLD, 911GT ,CIS, 428 fwhp 450 trq, Carrillo rods, 964 cams, TT retainers,7.5 comp 1.1 bar boost 320 ml black fuel head 009 injectors, 044 pumps, 60-1 T4/T3 dual scroll turbo
Old 10-17-2020, 07:40 PM
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