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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Sat Jul 02, 2016 7:39 am Post subject: Fuel control via WUR + rpm boost switch |
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Looking for some advice in tuning the fuel delivery. Running way too rich at WOT with AFR's in the high 9's and low 10's. Cruise and idle is in the 14's, usually bang on 14.7. Mid throttle and mid boost of 0.6-0.7 bar sees mid 12 AFR. So looking to lean off WOT without affecting the other results. Suggestions please as Google searching this forum has come up blank so far. Thanks _________________ 1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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Last edited by Carrera RSR on Mon Jul 18, 2016 5:52 pm; edited 1 time in total |
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Rasta Monsta
Joined: 12 Jul 2006 Posts: 11723 Location: PacNW
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Posted: Sat Jul 02, 2016 9:31 am Post subject: |
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Adjustable WUR? _________________ Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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morghen
Joined: 21 Jan 2005 Posts: 8868 Location: Romania
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Posted: Sat Jul 02, 2016 3:52 pm Post subject: |
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I have the same issue. WUR's natural responce is that it enriches too much on higher boost. All that fuel will actually cause detonation. This is the limit of the CIS. If UTCIS would have worked as intended we would all have very good control over the mixture..but it just does not.
In a month or so I will test out a modified S1 WUR with adjustability added. The way i see it, that screw will limit the amount of fuel the WUR will provide.
If it does that, i might just keep CIS for a longer period of time. _________________ https://www.the924.com |
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Sat Jul 02, 2016 5:31 pm Post subject: |
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Rasta Monsta wrote: | Adjustable WUR? |
And..... _________________ 1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Sat Jul 02, 2016 5:41 pm Post subject: |
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morghen wrote: | I have the same issue. WUR's natural responce is that it enriches too much on higher boost. All that fuel will actually cause detonation. This is the limit of the CIS. If UTCIS would have worked as intended we would all have very good control over the mixture..but it just does not.
In a month or so I will test out a modified S1 WUR with adjustability added. The way i see it, that screw will limit the amount of fuel the WUR will provide.
If it does that, i might just keep CIS for a longer period of time. |
Whilst a rich mixture is said to cool combustion and avoid det, it can also increase the risk as well. Too much fuel can also increase EGT's. So I'd like to get AFR close to 12 on WOT. I have a Bosch manual. It explains all the CIS parts but not how to control fuel. FSM's and forum threads discuss fuel pressures to factory settings. I cannot find any discussions on pros / cons for turbos in getting fuel control on modified turbos across the throttle and boost range . So I'd like some further learning before I go down this road. _________________ 1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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Cedric
Joined: 27 Aug 2004 Posts: 2600 Location: Sweden
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Sat Jul 02, 2016 8:37 pm Post subject: |
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Thanks Cedric. This is the reason for my post. Adjusting control pressures via the WUR appears to move the curve up an down the Rev/boost range. Leaner at the top means very lean at the bottom end. So just sounding out the theory and experiences here _________________ 1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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morghen
Joined: 21 Jan 2005 Posts: 8868 Location: Romania
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morghen
Joined: 21 Jan 2005 Posts: 8868 Location: Romania
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Posted: Sat Jul 02, 2016 10:10 pm Post subject: |
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Anyway, now thinking about another way to control this.
The thing you have to do is lift up the bimetal so more fuel goes to the tank instead of staying there to make the air plate lift higher.
So...boost pushes the bimetal down...(if no boost is applied no enrichment).
How about an inline boost controller to limit the boost that the WUR gets?
Say you're runin 1bar at the manifold and 1bar at the WUR means 10AFR.
Well lets try to reduce 1bar at the WUR to 0.8bar.
So we need a pressure restrictor inline between the manifold and the WUR.
EDIT -Here is what i'm thinking:
idea by m0rghen, on Flickr _________________ https://www.the924.com
Last edited by morghen on Sat Jul 02, 2016 11:13 pm; edited 1 time in total |
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Sat Jul 02, 2016 10:55 pm Post subject: |
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Makes a WUR which isn't boost controlled to one that is. We have this in our WUR's already and leaning out too far. Would work in conjunction with the AFR guage
Every thread I am reading is trying to richen the mixture at 1.0bar plus, not lean it off. I've run my car upto 1.3bar and still get 9.8-10 AFR. I also get det easier without octane boosting.
Quite like the idea of bleeding off boost to the WUR to limit the boost enrichment. I only sold a turbosmart boost controller last year damn it. Could rig up another boost gauge to ensure I avoid cutting off boost completely.
Some days I wish I did go EFi. _________________ 1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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morghen
Joined: 21 Jan 2005 Posts: 8868 Location: Romania
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Posted: Sat Jul 02, 2016 11:27 pm Post subject: |
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Or a simpler one i think: a small flow restrictor that bleeds out the boost before the wur.
Ofcourse bleeding boost = enriching but since the WUR responce isnt linear this should still be effective.
idea2 by m0rghen, on Flickr _________________ https://www.the924.com |
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morghen
Joined: 21 Jan 2005 Posts: 8868 Location: Romania
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Sun Jul 03, 2016 7:32 am Post subject: |
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Is the solution throwing Brian Leask $600 for a modified adjustable WUR and rpm enrichment device?
If so I'll be looking for a stateside buddy to sell me and post a WUR direct to mr Leask on my behalf in the near future. _________________ 1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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Dutch924-racer
Joined: 23 Jul 2007 Posts: 1076 Location: The Netherlands
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Posted: Sun Jul 03, 2016 3:16 pm Post subject: |
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you might contact Mittelmotor, I asume they run above 0.9 bar with their GTS replica.
Or convert to KE jetronic:
_________________ 937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller |
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Sun Jul 03, 2016 6:15 pm Post subject: |
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I have already contacted Mittemotor for their suggestions. Awaiting a response.
I'd bypass the KE and go full EFi if I wanted the to go through the pain of converting to anything. The romantic in me wants to keep CIS and the original look. The head wants more control, cleaner burn and more reliable hp. _________________ 1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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