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Fuel control via WUR + rpm boost switch
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1970
Location: Somerset, UK

PostPosted: Tue Jul 19, 2016 12:41 am    Post subject: Reply with quote

CÚdric wrote:
Nice solution, do you have an afr curve for a full load run?


I do need to do a 3rd or 4th gear run from low rpm to max. Anything specifically you are looking for as I am limited to road and the logging software. Its also likely to be too warm this week, 30deg+ temperatures and on holiday next week.

Unlikely to get properly dyno'd for a while due to time. I ideally want to go back to the same dyno I used back in May for a direct comparison.
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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: 1970
Location: Somerset, UK

PostPosted: Sat Jan 21, 2017 5:39 am    Post subject: Reply with quote

For the turbo owners with thermal management be it intercooled or chargecooled and retaining the CiS fuel control, I cannot recommend any more highly the need to use a boost enrichment switch to help lean off the mid range fuel delivery. It gives far crisper throttle response, lower initial EGT's which is kinder to the manifold, the turbo and the engine bay temps and will return far better mpg which is a nice by product from better performance.

There are several ways to control this whether an S1 or S2. Brian Leask's kit is an easy buy but can be bought separately as I did as I did not need the MSD rev controller. I used my Zeitronix to control my solenoid switch but there may be other options out there which I dont know about.

The only time I now see a super rich 10 AFR's is on full boost above 4800rpm. All other times I see 14.7AFR on cruise, 13AFR when initially accelerating and high 11's before the solenoid switch kicks in. Spark plugs look great, I did go colder than stock.

So there you have it. Add this to your modification plan if not going down the EFi and/or standalone ecu route.
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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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CÚdric  



Joined: 27 Aug 2004
Posts: 1973
Location: Sweden

PostPosted: Sat Jan 21, 2017 6:16 am    Post subject: Reply with quote

Hmm, it was a while ago, i don't remember what you are actually controlling with the switch, blocking wur line to lean out?
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1970
Location: Somerset, UK

PostPosted: Sat Jan 21, 2017 7:20 am    Post subject: Reply with quote

Zeitronix is switching a solonoid boost valve. When under 4800rpm the valve is closed and not allowing the boost to reach the WUR, therefore not enriching the fuel. After 4800rpm the valve is opened and boost hits the WUR and full fuel enrichment is triggered. Works exactly as the Brian Leask system. His uses an MSD rpm controller. I'm using the same Pierburg solonoid valve used on a number of turbo cars including Panamera. That's it. Simple but effective

Solonoid valve next to WUR

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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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CÚdric  



Joined: 27 Aug 2004
Posts: 1973
Location: Sweden

PostPosted: Sat Jan 21, 2017 7:49 am    Post subject: Reply with quote

Very simple solution, as long as overfueling is the issue. Pretty interesting, at the boost levels you run i would have thought the 931 cis starts to bottom out, not the opposite. But it obviously have much harder to control afr when you push the system. It should be doable with a cheap rpm switch as well, or a rpm based boost controller ideally. Seems like I don't have to worry that much about my future upgrades then, will be solvable

The actual max power level of the 931 system has been discussed so many times, it really do seem to have quite some margin..
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1970
Location: Somerset, UK

PostPosted: Sat Jan 21, 2017 8:18 am    Post subject: Reply with quote

What we do know is that my fuel distributor is the later higher flow version. It was also refurbished prior to my purchase. So whether it has been improved upon again I don't know. The company which carried out the refurb offers a further increase in fuel flow for motorsport and high perfermance applications. Maybe my car has been blessed and therefore why I haven't gotten close to the fuel limit. I don't think I will until I change the compressor wheel.
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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: 1059
Location: The Netherlands

PostPosted: Sat Jan 21, 2017 4:41 pm    Post subject: Reply with quote

Maybe a stuppid question, but why a RPM switch and not a boost controlled switch ?

Maybe a stuppid question, but why a RPM switch and not a boost controlled switch ?

http://www.ebay.co.uk/itm/BOOST-PRESSURE-SWITCH-NOS-WATER-METHANOL-INJECTION-/142051890034?hash=item2112f3d372:g:k2wAAOSwU9xUQrJO

http://www.ebay.co.uk/itm/Sub-Zero-Boost-Pressure-Switch-To-Fit-Turbo-Water-Methanol-Injection-NOS-/252560679628?hash=item3acdca22cc:g:m8MAAOSwLnBX66SF
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Forge recirculation valve + boost controller
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1970
Location: Somerset, UK

PostPosted: Sat Jan 21, 2017 7:38 pm    Post subject: Reply with quote

The WUR is a boost controlled switch. Already dumping in full fuel in from circa 2500rpm when full boost is achieved and making the mid range rpm over rich with 10AFR's. which is fine when the stock car has no thermal management and you need the fuel to avoid detonation.

RPM triggered solonoid valve is trying to stop this until you hit an rpm level where you need the fuel. Thermal management means you can run leaner mid range rpm without fear of inducing det, ideally high 11 to 12AFR.

It's a trick the 930 guys have been using for years with the Brian Leask kits.
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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: 1059
Location: The Netherlands

PostPosted: Sat Jan 21, 2017 9:06 pm    Post subject: Reply with quote

thanks, I also want this upgrade, only need te find a affordable rpm switch
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937 trackday car
Series 2 engine
951S turbo and intercooler
937 DITC
Fast road camshaft
Forge recirculation valve + boost controller
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1970
Location: Somerset, UK

PostPosted: Sat Apr 25, 2020 7:29 pm    Post subject: Reply with quote

Dutch924-racer wrote:
047 is series one ROW, 096 is series 2 ROW



Anyone know what the 928/Merc/Carrera GTS fuel metering head flows? Believe the part number is Bosch No 0 438 100 027
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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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gegge  



Joined: 27 Jul 2007
Posts: 1075
Location: Sweden

PostPosted: Sat Apr 25, 2020 9:02 pm    Post subject: Reply with quote

Goole trnaslate "Fun with a K-jet discussion.

I myself have spent some time with the spray and thought to share with me my experiences.

A standard B21ET fuel head Bosch 0 438 100 115 with 7 kg system pressure (adjusted according to Volvo's B21ETL Group-A 225 hp instruction) flowed just over 300ml / min when I tested which is good enough for this effect but no more than that.

Also test flowed an MB V8 aluminum fuel head Bosch 0 438 100 068. It came from an early Group-A car.
The first Group-A cars went with MB 068 head and Porsche 928 air wave Bosch 0 438 120 049. The fuel head was bridged with short teflon hoses, ie two outputs to a spreader. The system pressure was around 7 kilos and it flowed 530-580ml / min with Gold Sprayer which was the amount of Volvo drove with. The higher amount of 3rd cyl. when it went hottest. Do not think that the fuel head was sparked, but it flowed so much bridged. That syringe is now sold.

The sprayer I now have is a genuine Volvo Group-A Racing sprayer which is basically an MB V8 fuel head but race prepped by Bosch.
Porsche used it on their Turbo 934 RSR race cars hence the nickname "Group-A Porsche sprayed"
These fuel heads have special Bosch numbers. Everyone I've seen has different numbers. Everyone starts with 4250 / XXXXXE.
My fuel head has no. 4250 / 21950E

Just as Lundin says, it is possible to change the air cone (Switching cone) on the air wave which has a different casting than those that sit on ordinary passenger cars. My airwave has no. B 438 120 363 928 001.
The same one they dare I have looked at has all different no. WEIRD!

Here it happens a bit when you sample flow. This fuel head has 4 outputs plugged. With 8.5 bar system pressure at closed flap, it flows 600ml / min per diffuser ...: thumbright: Which is enough for over 400Hp.

Can also add that Volvo drove with a control pressure as high as 3.8-4.2 bar otherwise the monkey went ...: wink:"

http://forum.savarturbo.se/viewtopic.php?t=39368&start=180

With 3/8" ID fuel lines to the injectors this setup flows 800cc/min/injector at wide open flapper (before it has to feed into an inlet manifold at turbo boost pressure), so I hope my fuel flow problems in the restored 240T Gp-A are nearly over..."

https://forums.turbobricks.com/showthread.php?t=318880&page=7&styleid=6
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