Show full size
Discussion Forum of
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
 Technical FAQ924 FAQ (Technical)   Technical924 Technical Section   Jump to   Jump to PCA 924 Registry924 Registry

Warm up Regulator (rebuild and making adjustable)

Post new topic   Reply to topic Forum Index -> How-To
View previous topic :: View next topic  
Author Message

Joined: 02 Oct 2006
Posts: 47
Location: So Cal

PostPosted: Wed Oct 25, 2006 12:29 am    Post subject: Warm up Regulator (rebuild and making adjustable) Reply with quote

I found this page by accident and it was too good to not post...

67 912 2.0 Type 4
94 968 Cabriolet
82 924 Turbo
Back to top
View user's profile Send private message Visit poster's website
SoCal Brian  

Joined: 11 Nov 2005
Posts: 16
Location: San Diego

PostPosted: Sat Nov 18, 2006 4:57 am    Post subject: Reply with quote

Thanks for that great post! I was tired of my 80 924 idling like a top fuel dragster when cold so I removed the WUR and cleaned it according to that article. It was a total success, car runs perfectly cold and has a normal warm up cycle now, Thanks again...
Back to top
View user's profile Send private message

Joined: 01 Oct 2004
Posts: 15542
Location: Woodstock IL

PostPosted: Sat Feb 24, 2007 5:42 am    Post subject: Reply with quote

I'm pasting the contents of the link here, just in case that URL ever goes away...


The article on making the WUR adjustable is by Jay Pineau, Ark-La-Tex Region, PCA, in Volume VII, pages 116-117 of Up-Fixin. In case you don't have that, here is the text:

"An engine equipped witha Bosch CIS (K-Jetronic) fuel injection system depends on the accuracy of the control pressure for starting and drivability performance. If during a system pressure and performance test it is determined that the warm-up regulator is at fault, you are faced with an alternative: replace it (list price now about $280) or attempt to repair it.

The regulator is a fairly simple device which varies the control pressure with temperature (both engine and self-induced via an internal heating element). There are two main causes of malfunction: heating element failure and foreign material in the metering chamber.

A quick check with an ohm meter will determine if the heating element is defective. It should read 18 to 22 ohms resistance (I didn't get this exact reading, but it wasn't an open circuit). If the element is faulty, the regulator must be replaced unless you can locate a replacement heating element from a used regulator.

If satisfactory, the regulator can be carefully disassembled and cleaned. Take care that the two small orifices are completely clear. If the diaphragm shows any wear, flip it over at reassembly. (Be careful here--the diaphragm is VERY thin metal. I didn't disassemble the bimetal spring, just pushed it aside to remove the diaphragm.)

After reinstallation, it may (WILL) require readjustment to obtain correct pressure relationships. (These pressures vary with the year of the car and the part number of the WUR. You can find them in the shop manual. If you don't have them, I can xerox and snail-mail)

Bruce Anderson described in PANORAMA (October 1984) how this adjustment can be accomplished by "knocking the plug". The only problem with this procedure is if you "knock" it in too far, you must remove and reassemble the regulator to "knock" it back (indeed true, I tried this method). By the time you have obtained the best cold and hot values, you may have to do it several times.

The unit can be modified to provide for external adjustments by the addition of a pull-out screw and nut which permits very accurate movement of the plug."

The article also includes a diagram, but essentially you drill and tap a 5mm hole about 10mm deep into the center of the plug. Then drill a second 1.5mm hole in the crack between the plug and the WUR body. Put a 1.5mm roll pin in this hole and tap it down flush with the body (the idea is to keep the plug from rotating when you move it up and down with the pull-out screw).

Put a 5mm allen-head screw, with a washer slightly larger than the plug, and a 8mm diameter nut, into the 5mm hole. Keep the nut backed off, and gently tighten the screw until it bottoms in the hole. Now, to raise the plug (higher control pressure), hold the screw with an allen key and tighten the nut (it's a tight fit, but an 8mm box-end wrench should fit over the head of the screw). To lower the plug (lower control pressure), hold the screw, back the nut off, and then tap the screw (I use a brass drift and it takes a fairly hard whack).

Of course, while you are doing any adjustments, you need to be looking at the control pressure. I bought a CIS gauge from J.C. Whitney for less than $60. Be sure that the electrical connector to the WUR is disconnected when setting cold control pressure, and that the engine is dead cold. To get the fuel pump to run, jump terminals 30 and 87a on the fuel pump relay socket (on my 83, it is the red relay in the luggage compartment).

If your car doesn't have an O2 sensor, you are completely dependent on correct fuel pressures and mixture setting to get the engine to run correctly, so the WUR is important. After I did the WUR modification, I am confident that I can set my engine up properly, and it starts and runs perfectly, cold or hot.

I hope this helps--if you want the diagram of the modification, send me an SASE at 30822 Alta Mira Drive, Redlands, CA 92373.

Bob Tindel

75 Fiat X1/9 | 80 US 931 '941' | 78 Poli-Form
Back to top
View user's profile Send private message

Joined: 29 Sep 2013
Posts: 2596
Location: MI

PostPosted: Sat Jul 11, 2015 7:52 am    Post subject: Reply with quote

Great writeup on rebuilding a WUR with great pics..

I may add more information sources here as I come across good ones.. I'm in the WUR research mode..
80 Turbo - Slightly Modified
Back to top
View user's profile Send private message Yahoo Messenger

Joined: 01 Oct 2004
Posts: 15542
Location: Woodstock IL

PostPosted: Sat Jul 11, 2015 1:46 pm    Post subject: Reply with quote

Thanks for the bump on this post. It got me to searching after reading a couple of the above referenced threads. Here are a few more references worth noting:
First, a line drawing of the modification described in the Bob Tindel method:

And the actual Pelican post where he and others comment on the method and results:

More pix of the Tindel mod:

Note to self: make archive copies of pix
75 Fiat X1/9 | 80 US 931 '941' | 78 Poli-Form
Back to top
View user's profile Send private message

Joined: 29 Sep 2013
Posts: 2596
Location: MI

PostPosted: Sat Jul 11, 2015 3:30 pm    Post subject: Reply with quote

Something else neat I found...

the best things you can do for your CIS equipped car
relay the fuel pump.

raise the fuel pressure, make absofrickenlutely that your rest pressure does not exceed that of the injector open pressure. dont guess, check it! *slaps you on the head*

New injectors.
Balance the flow.
DO IT IN THAT ORDER *slaps head*

those looking for a real upgrade. go find a wrecked 4000/5000 with CIS+E get its fuel regulator and all the piping for it. retrofit your CIS+Lambda head to accept this external pressure regulator that has (OH MY GOD!!!) the capability of load sensing. Like our 931 boost sensing WURs I think
the second cool bit of smarts this has, your rest pressure is now independant from your main pressure.
YES you heard it. the old style shuttle regulator had a failing! every time you raised your operating pressure 1 psi, so did your rest pressure. for those of you lazy bastards with leaking injectors this means even more leaking! for those of you with a good set of injectors but you never checked the pressures.... this means leaking injectors. good luck starting. hope your piston rings enjoy rough dry sex.
I imagine that means raising how much the boost sensing part lowers control pressure, I wonder how to do that..

if you managed to keep with me this far here is your formula

Relayed fuel pump
new injectors
flow balanced
modify your ecu's chip to max out the frequency valve under load.
raise your operating pressure to about 95-105 psi with the regulator at atmospheric reference.
drive the car in 2-3 gears at wot. measure how high the airflow meter goes.
if the airflow meter tops out before the rev limit, increase the control pressure so it just tops at 6000 rpm
measure your air fuel ratio with a good wideband 02 sensor.
if you are around 13:1 success! you got lucky.
if you arent, raise or lower fuel pressure as needed, do not exceed 115 psi unless you have 2 pumps in series.
set your idle c/o
go for a cruise, you should be able to stay in closed loop, if you disconnect your o2 under cruise and its too lean, ease off your control pressure slightly, if you are too rich, slightly increase control pressure.
set your idle c/o

fact. your idle c/o adjuster does next to nothing anywhere else except at idle. dont try to use that as a "richen me up" screw.
fact. your control pressure regulator is 100% adjustable if you know how to do it, and its fricken hammer simple.
fact. your max fuel flow is set by main pressure, your fuel curve is set by the airflow meter cone, your location at any point in the cone is set by airflow vs control pressure, and your idle mixture is (omg!) set by the idle c/o (mixture) adjuster.
fact. the frequency valve is only along for the ride as an emissions device. It can be utilized to richen things up but only marginally. unless you can burn eproms forget about using it for any sort of tuning, its output is mostly fixed at WOT and along for the ride.

CIS is simple as a carburetor, you just need to know what your main jet, low jet and idle mixture adjusters are. i just told you so dont nag me for more information. cis is setup reverse of a carb, you set your main/high jet first, then your low jet and then your idle mixtures, then for shits and giggles you check and adjust it again 3 times more just to make it pretty.

last. dont go tearing apart a cis distributor unless you have a spare or picked up a junk one to learn from. once you crack that thing apart you ruined a very hard to make laser cut seal by covering it with your grummy finger prints and dust. i could tell you what sealants work for re-assembly, but i dont wanna, thats my secret.
any adjustments you do to balance the thing is done entirely externally anyways, so stop poking in there, its like a kid poking the guts of a vcr, your only gonna make it worse.

I really like that idea about relaying the fuel pumps so they draw there power from a bigger/newer/more reliable source with less voltage drop from old wiring, my battery is right there by my pumps so that would be an easy wire job to use there OEM relay power to flip a big new relay that powers them straight off the battery for some rock solid +12v..

And my WUR today, now squeaky clean, 3.9 bar warm control pressure, I'll test it every time I open the hood
Loving my permanent gauge..
System pressure 6.0 Bar, might bump that up a touch some time..

I guess I didn't get a pic of the valve body part open and all the pieces in line, thought I did, anyway I had that all apart too and blew it all to kingdom come with compressed air and brake parts cleaner, being very careful and gentle with the perfect looking steel diaphragm of course.. Pics are from disassembly.. I didn't open the vacuum port part of it, held vac just fine with my tongue over it..

Header wrapped my upper charge tube in titanium tint today too but you can't see that until it dries and I trim the clamps..
Stainless steel "zip-ties" are a joke BTW, too much backlash before they grab, had to use more hose clamps..
Actually I ordered titanium and got black, then got a free roll of titanium, so I have 25' of black and plenty of leftover titanium to do my lower charge tube after I get it welded for porting, thinking about using the black to wrap my exhaust manifold, I have a scheme for its odd shape..
80 Turbo - Slightly Modified
Back to top
View user's profile Send private message Yahoo Messenger

Joined: 01 Oct 2004
Posts: 15542
Location: Woodstock IL

PostPosted: Sat Jul 11, 2015 11:19 pm    Post subject: Reply with quote

Did you find a replacement for the main rubber gasket that seals the two halves together?
75 Fiat X1/9 | 80 US 931 '941' | 78 Poli-Form
Back to top
View user's profile Send private message

Joined: 29 Sep 2013
Posts: 2596
Location: MI

PostPosted: Sun Jul 12, 2015 2:55 am    Post subject: Reply with quote

No, it was in good shape, like everything else, so it just went back together clean and I smeared some axle grease around it where the 2 halves come together..

It's not like that square cord O-ring type gasket really seals anything, the housing area it seals has a vent to atmosphere to it anyway..

You know ideola if you have a spare 931 WUR laying around in questionable condition I wouldn't mind taking a whack at making an adjustable one out of its top housing core with the Bob Tindel method..
If it turns out well I could put all my good WUR guts in it if its guts are shot and do some testing..
I have the time, equipment, and ambition but I don't want to hurt my good WUR experimenting with it.. If I can turn out one I can turn out many..

But I believe the key would be to make the boost/vac sensing part of the WUR adjustable..
To be able to adjust warm control pressure separately at vacuum to maintain good drivability, and be able to adjust how much it drops warm control pressure when boost/pressure is applied to the vacuum diaphragm for WOT enrichment without having to skew cold control pressure adjustment...

Adjusting the bimetallic strip position as in the Bob Tindel method to change warm boost control pressure would also change cold control pressure, and vac control pressure. Your changes would be all encompassing throughout vac/boost changes and you would still be at the mercy of however much its vac/boost sensing part drops control pressure as is in relation to wherever you change its bimetallic spring position/pressure to..

Like say you want to lower your on boost control pressure to richen the mixture, or raise it to correspond with raising system pressure for maximum fuel flow, the Bob Tindel method would raise your on boost control pressure just fine but it would also raise your cold control pressure, and raise your vac control pressure possibly having a negative effect on cold starting and warm VAC control pressure for cruising and general drivability purposes.. Conversely equal for lowing control pressures with this method, it would effect everything everywhere..

Now if you could find a way to adjust the boost/VAC diaphragm part of the WUR you could adjust your cold control pressure via the Bob Tindel method or just knock around the standard plug, and then separately adjust your warm VAC control pressure for cruising and drivability purposes, and also separately adjust your on boost warm control pressure for WOT/boost/accel AFR purposes because we are running at higher boost than the WUR is designed to compensate for..

That would be the cat's ass and have you boosted CIS car running like a raped ape everywhere not just on boost sacrificing starting and general drivability.. Who knows how high the limits of max HP on CIS could be extended if you could really adjust all your pressures all independently..

Imagine bumping your system pressure to 100psi or so for maximum flow, then being able to adjust your cold control pressure for good starting at 100psi system, and adjust your warm VAC control pressure for cruising and drivability at 100psi system, and adjust your warm boost/accel control pressure for WOT AFR at 100psi system all separately to get the best of all worlds..

If I could get my hands on another 931 WUR to play with without fear of damaging it and another WUR line to simplify testing procedures it would be mad scientist time for sure.. I would also need a wideband to put it into practice actually running the car with changes..

Maybe some day, I have enough trouble budgeting all the pans I have on the frier with my 931 already..
A lot of pans on the frier at the same time keep me occupied though even if I can't drop the cash for all at the same time I have something to work on at all times to keep me occupied and out of trouble..
80 Turbo - Slightly Modified
Back to top
View user's profile Send private message Yahoo Messenger

Joined: 29 Sep 2013
Posts: 2596
Location: MI

PostPosted: Mon Jul 13, 2015 4:26 pm    Post subject: Reply with quote

At this adress
There are a bunch of K-jet pdf's on the left you can download and read, they only work for me if I "save as" and then add ".pdf" to the file..

The one pdf entitled there as "K Jetronic book", the top one, is of particular interest. It is actually a Bosch manual with the title "Technical Instructions - K Jetronic".. If you want to know K-Jet I highly recommend reading it, or at least having a glance at its excellent illustrations nicely labled..
But reading it all leaves me with more questions, as always..

Particularly its section on load sensing WURs, and how in Fig 34 the vacuum connections are labeled..
In Fig 34 it shows item 3 "vacuum connection" (pretty much post TB)..
Also item 9 "to atmosphere pressure"..

According to this the vac line on my car to my WUR is backwards, the car came to me with the OEM cloth vacuum hose to item 9 in that diagram and that is the way I have it hooked up now..

see here in this picture you can see item 9 coming out on the top left there, what a nice nipple for a vacuum line, seems meant to be..

And see here in ideola's picture item 3, not quite as nice looking of a place to put a line to me.. My WURs item 3 connection/vent was definitely just a vent with a spiderweb/dust bunnie in it as I received it, I specifically remember cleaning it out..
And look, item 9 in this pic has a line on it..

But by way of logic it would make total sense for item 3 to be the boost/vac line.
Pulling up more control pressure helping the center spring with vacuum for leaner running..
And pushing down on the lower diaphragm vs atmo with boost to reduce the center springs effectiveness lowering control pressure for richer running/WOT/boost enrichment..

I am going to try to find a trusted source to see where the porsche vac line is supposed to be connected to the WUR, something is amiss here, I need to get to the bottom of it..
Anyone know??

Ok this is going to make for a long post but also this section on cold control pressure and the bimetallic strip..

This shows the bimetallic spring having no contact, and therefore no effect on control pressure when in the warm state..

If this is the case then how would the Bob Tindel method posted above by ideola be an effective means of adjusting anything other than cold control pressure? It doesn't look like it would to me..

I need to find out about that item 3 vs item 9 vac connection thing.. It's stumping me right now..
80 Turbo - Slightly Modified
Back to top
View user's profile Send private message Yahoo Messenger

Joined: 21 Jan 2005
Posts: 8653
Location: Romania

PostPosted: Mon Jul 13, 2015 4:59 pm    Post subject: Reply with quote

Rasta, does your UT WUR still work?
That thing was a very clever idea..
Back to top
View user's profile Send private message Visit poster's website Yahoo Messenger MSN Messenger

Joined: 29 Sep 2013
Posts: 2596
Location: MI

PostPosted: Mon Jul 13, 2015 5:13 pm    Post subject: Reply with quote

Heres some more cool stuff for this thread.. Credit to jrcook320, I think I will compile the information I find useful (a lot) from him in this post..

Now this looks like a good and easy to make way to adjust warm control pressure, but he says there's an even better way on out 931 WUR's under that gold colored hat covering the bottom of the boost sensing part..

It's a press fit. Moving it requires a great deal of force. Either a hammer to move it down, or tightening the nut to pull it out.

The notched spacers are doing the same thing, just provide leverage for the bolts to press on the housing to pull the main valve body out. Knowing what I know now, I would only ever use this setup on a non vacuum or non-boost sensing WUR (such as the stock e21 WUR). The boost sensing WUR showing in the pic has an adjustable spring perch easily accessible by drilling a hole in the lower diaphragm stop on the bottom of the WUR.

And NEVER plumb a wur up the way I did in that pic. It doesn't work well, just run a single line to the top port, forget that check valve nonsense. (you live and learn..)
Last edited by jrcook320; 05-08-2011 at 11:24 PM.

""""" If you use the Volvo setup, you need to use the audi 5000 S or volvo WUR. If you use the Porsche setup, you should also use a Porsche WUR. You will save time in tuning in the long run. They are constructed differently, function differently and are plumbed different. I could go into enough detail on this to start a whole other thread (Which I plan to do).""""

Maybe I can find that thread on how a 931 WUR is built and plumbed so different..

Awesome CIS testing procedure video by jrcook320, he has a permanent CIS tester installed much like my own, imagine that..

Video of his BMW 320 running 13.92 in the 1/4 beating a mustang..
80 Turbo - Slightly Modified
Back to top
View user's profile Send private message Yahoo Messenger

Joined: 29 Sep 2013
Posts: 2596
Location: MI

PostPosted: Fri Jul 24, 2015 4:34 pm    Post subject: Reply with quote

Engine Management

Volvo / Bosch E-ZK Ignition
Engine management - The ECU featured a 14 sensor based programmable engine management system (includes 'knock sensor') modified for more map points. Volvo were one of the first companies to use programmable engine mangement in GpA.
A second ECU - termed WT (Water ,Turbo) controlled boost pressure, water injection, knock control (to retard ignition timing down to a single plug/cylinder), and later rear-wheel slip. The later ECU engines were 20% more fuel efficient than earlier mechanical K-Jet CIS engines.
Interactive telemetry for remote tuning
Electronic Traction Control (ETC) - Wheel speed sensors monitor rear wheels relative to front. Any difference results in a reduction in boost pressure, then followed by a cut in fuel supply to middle cylinders 2 and 3. This system was built in new 1986 RAS cars for Peggen Andersson and Mauro Baldi. The car was tested but never raced as it was brand new and there was a risk of "child problems". The 'traction control car' (see pic below) was faster than the racecar during testing before the race, and again on the test on Monday after the race. [tested at 1986 ETCC round at Estoril, Portugal ] This racecar #605 stands in the Volvo Museum and features the developments of front suspension and an LED display "inspection system" dashboard.

Rare pic of the final works RAS Sport special ETC 'electronic traction control' 240RXT - during testing at Estoril, Portugal, 1986.
Chassis #605 (pic VMS archive) - Note the single fuel receptacle in the rear panel.
Fuel Injection
Bosch K-Jetronic CIS
Continuous injection, mechanical
8 chamber aluminium fuel head, 4 outputs blocked. Click pic to enlarge

Injectors: Group A (K-Jet mechanical), Bosch 'Gold' injectors, were a race spec injector made for Volvo and not possible to obtain for many years now. 530 ml/min on 1, 2 and 4th cylinder, 580 ml/min on the 3 cylinder), (magnetic valves on 2 & 3rd injector to serve as a antispin system - cuts fuel when spining). Reportably they were made of a Porsche shell with Volvo turbo core. They have a opening pressure at 3 bar (43,5psi) and give about 600ml/min at 8bar (120psi) pump pressure.
Air sensor plate with changeable cones - to run with optimized control pressure and air/fuel ratios at all revs, and to suit different race tracks

Water Injection
Water spray mist was used to increase engine efficiency and to cool exhaust valves. System components were a modified Bosch Jetronic fuel injection (with airmass meter or map sensor, high pressure pump and four "yellow" Bosch EFI injectors). Water injection was also sequential, meaning the injector only sprays on the intake stroke when the valve is open for minimum water use. The amount of water injected is around 10% of the regular fuel, the solution being a mix of water, alcohol and cutting fluid, the latter used to save the injectors from rust.

Pic is of SAM supplied water tank. It attaches at the start of the chassis arc before it curves up over rear axle.
Sold out.

Fuel tank - 120 litre safety tank (Group A regulations), * Quick fill system
Two pre-pumps feeding catch tank, plus two high pressure main pumps (serial or parallel connected)

Short History - Volvo 240 Turbo Group A
FISA Group A homologation - 1 March 1982
80 Turbo - Slightly Modified
Back to top
View user's profile Send private message Yahoo Messenger

Joined: 02 Jul 2018
Posts: 281
Location: Poland/EU

PostPosted: Mon Apr 18, 2022 7:56 am    Post subject: Reply with quote

I think I need a golden shovel for digging in a thread that is 16 years old, but...

Anyone has tried relocating the WUR?

Adjusting it in factory location is just pain in the... nutshell.

I'm just thinking about the GTS location. Thought the stock mount near the firewall allows to warm up together with the engine. But on the other hand the thermo time switch warms up the WUR anyway, so in theory the location shouldn't make a difference, right?

'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)
Back to top
View user's profile Send private message

Joined: 10 Dec 2006
Posts: 921
Location: Noosa Heads QLD Australia

PostPosted: Mon Apr 18, 2022 8:48 pm    Post subject: Reply with quote

Hiya Kondzi
Some 25 years ago I relocated the WUR to a somewhat similar position as the GTS has.
Simply had a small alumimium plate welded to the top of the #1 inlet runner, and then drilled and tapped two holes to mount the WUR. You will need to refab the two fuel lines, or in my case I simply bought some braided line and fittings to complete the job.

I'm happy to send you piccies if you provide your email address.
80/81 932/8 ROW
Back to top
View user's profile Send private message Send e-mail

Joined: 29 Sep 2013
Posts: 2596
Location: MI

PostPosted: Wed Apr 20, 2022 6:44 am    Post subject: Reply with quote

CarreraRSR did

WUR tuning is so course though..
You know what I would do..
80 Turbo - Slightly Modified
Back to top
View user's profile Send private message Yahoo Messenger
Display posts from previous:   
Post new topic   Reply to topic Forum Index -> How-To All times are GMT + 10 Hours
Page 1 of 1

Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

Powered by phpBB © 2001, 2005 phpBB Group