XRTypeRS

Just something I've been mulling this over in my head from time to time. It seems to be there are currently 3 ways to "mod" a KE Jet equipped car (i.e. RST) for more fuel:-

1). Standard "screw" adjustment of black EMFPR module on side of metering unit to increase fuelling over the entire rev range - this is what is done when a car is "chipped". Obvious downsides are wasted fuel at part load and there are limits to how far the screw can be turned!.

2). Supplement standard (adjusted as in (1)) KE with a 5th injector. Downsides are more plumbing, wiring, expense for the driver etc and potentially imperfect / unbalanced fuel distribution to each cylinder.

3). "Secret" metering head mods - I can only assume these are some "mechanical" mod inside the head itself (maybe to the diaphragms themselves or some internal passages?) as the EMFPR is a sealed unit and nobody has ever mentioned a "fuel box" mod - apart from the usual rev limit capacitor change obviously. How these mods can increase fuelling only at full load is a mystery - and Im sure the people that know will keep it that way.

I will ignore the "magic pipe" for now - having read an earlier thread on this I agree with the NMS view that the theory doesnt hold up for anything but wide open throttle.

However it has occurred to me that the standard KE system might have some scope to provide extra fuel simply by making some electronic mods to it - and im very surprised that it seems nobody has ever really mentioned this avenue - all the solutions seem to be "mechanical" in some way.

There seem to be a couple of obvious avenues :-

1). An old trick listed in some books is to alter the resistance of the temperature sensor feeding into the KE control box. This attempts to fool the box into believing the engine is starting from cold and so throwing in a lot more fuel. In theory it might be possible to connect some circuit in theory which would affect this sensor value dependant on engine RPM and manifold pressure to give more fuel. However ive also read some KE systems "sense check" inputs from external sensors to eliminate rapidly changing sensor values (which this mod would cause to the temp input). Does anybody know if the RST KE box is so equipped??.

2). Alternatively we could tap directly into the EMFPR current drive output from the box and change this dependant on revs and manifold pressure to again increase EMFPR current and enrichment. I believe the "milford K-star" system worked in this way but as these are NLA (maybe indicating that they didnt work??!) I cant be sure.

Has anyone else had similar thoughts to this??. anyone got a circuit diagram for the KE control unit??! - obviously the best solution would be "proper management" but we all know thats expensive - im just very surprised more people havent tried to mod on the very crude yet reliable KE as it does appear pretty simple electronically (just looking at the components in the box!).

Any thoughts any one?.

Stu

JesseT

The fact is, that tampering with the EMFPR current will make the air-flow measuring disc go down with less resistance. This will give more fuel per air mass flown in. So everything seems ok untill you reach a flow level that makes the disc bottom out in the measuring head. Now having had the EMFPR current modified, it will bottom out SOONER.
So, what limits the fuel flow is the disc bottoming out. The air-flow meter is then "wide open". No electric mods can make it provide more fuel after that.

Having said this, the S1 metering head opens much more before bottoming out. Has anybody ever tested if it's capable of supporting more power then?

Stu @ M Developments

iTrader: (12)

This isnt quite true, the ultimate fuiel flow is conttrolled by the differential pressure.

Someone somewhere modifies the black box with 2 internal screws to control

1) part load fuel
2) full load fuel.

But ive only seen it once and have no idea who does it

MikeyXR2i

seeing as its been mentioned, is there any differnece between a S1 and S2 metering head? They look identical.

XRTypeRS

Hi Jesse, glad you replied

I cant see why this would be as in KE the control pressure which is what acts against the KE plunger is the direct feed from the fuel pump, it does not get effected by the EMFPR - the EMFPR effects fuel flow by changing the pressure differential between the upper and lower chambers in the head so changing diaphragm flex and hense fuel flow.

You are correct the once the flap is fully open the slits do not open more but its the pressure differential that makes the difference - hense why an RST on WOT (whent he switch on the TPS makes contact goes a lot more rich (mine jumps from about an AFR of 12.7 when on full boost but just with the throttle just off the WOT position down to about 11.3 when the switch makes). This is totally due to more EMFPR current changing the pressure differential.

Have you seen the KE book by Probst?, its not the best book but after reading it about 10 times I just about understand how KE works at at basic level !!

Never seen an S1 meter head, you think this might have more flow possibilities?? - I suppose the motorsport S1s had to get their fuel from somewhere!!

DazC

iTrader: (1)

You still are limited by the flow through the EMFPA which is why it has to be adjusted in the first place. If it has been adjusted to it's maximum then how can you get any more out of it by foolinf the coolant temp sensor? All that will do is make the black box tell the EMFPA to allow more fuel through.

What about fuel pressure

XRTypeRS

Theres only one screw in a standard unit isnt there stu??, so someone drills a hole in it and taps it and adds a screw??, dismantles the whole thing??. Facinating!

That book I have has a pic of a EMFPR that has been chopped in 1/2 so you can see the plate, I cant see how you could add another screw to effect fuelling in the way you describe?, at the end of the day it only seems to be a sprung plate??, the standard adjustment screw just appears to twist the whole assembly closer to the ports hense increasing the "at rest" pressure differential?.

I'll scan the pic if anyones interested

Stu @ M Developments

iTrader: (12)

Hi Pal,
No sorry, by black box i meant to say The Fuel ECU

XRTypeRS

Daz the fuel flowing though the EMFPR doesnt go to the injectors, infact to increase fuel delivery to the injectors you reduce fuel flow through the EMFPR to increase differential pressure.

XRTypeRS

No probs Stu! - I assume when you say screws you mean potentiometers?? - changing the value of some resistances? - seems to make sense

Dont suppose you took a picture of the mod....

JesseT

Just as you think you undestand KE somebody comes and says your wrong Propably true then. Glad I got the discussion started anyhow. I'm even more glad that I don't have a KE anymore

I once designed a plug-in device that gives crude adjustment to mixture. It consisted of disconnecting the plug from the EMFPR and connecting the plug to a 30 Ohm resistor instead (~=resistance of EMFPR). Then the voltage is read and a little is added to it by using a MAP sensor and evenly spaced adjustments. Then the voltage is supplied to the EMFPR. I never got around to actually building it though as i went for the Megasquirt route.

XRTypeRS

I know what you mean, its a very clever system really - it took me several readings of the book to get it clear in my head and I still have to re-read it every time I think about it!!

This is the sort of thing I was considering too - question is what effect would your added volatage have back upstream at the "black box" on the bulkhead??. I believe the milford system would have effected the same mod but probably isolated the output from the black box from the rest of the circuit so preventing any weird "loading" effects on the standard control box??

DazC

iTrader: (1)

Yes, The EMFPA is used to control the differential pressure between the upper and lower chambers so one you reach the limit of the EMFPA, how can you make it flow more to the injectors if all that the CTS will do is control the EMFPA is what I am trying to say...

XRTypeRS

I can see what ur saying Daz - so if the EMFPR current was totally maxed (I assume this max current value must be what could be measured when the engine is cold cranking) this is the max fuel flow as adjusted by the EMFPR- I suppose Im just speculating that the this flow is greater than what is possible when the normal "EMFPR screw adjustment" as obviously if you overdo this you toally wreck your part load economy to a level that the car would not be reliable due to plug fouling etc.

This is all just guess work - I would have to run some tests, i.e. measure cold cranking current, measure WOT full boost current etc - might be interesting.

Anyway, best go outside now before it rains and check her over anyway, MOT next week.

DazC

iTrader: (1)

Yes, all I am saying is that the limitations to how much KE can fuel may not be down to electronic control of the EMFPA but from a physical sense that it simply cannot create the difference in pressure to allow more fuel out to the injectors.

essexrsturbo

interesting

rsrob

dont know if this helps but it has a few ideas

http://www.escortrsturbo.co.uk/commu...showtopic=5754

XRTypeRS

Not sure about the Audi injectors mate - to be honest all ive read says that the standard RST injectors are not a limitation, they will flow a lot more. The metering head / electronics is what limits it.

As for the magic pipe, there is a multipage heated thread somewhere on here where Karl and various others argue the toss over this. Having read the KE book I have to side with Karl. Yes the magic pipe will give you more fuel on WOT enrichment but it will lean you off if your just outside the WOT zone - this could be dangerous if your running a blt close to the melt zone at this point. Karl seems to like to play safe and who can blame him.

DazC

iTrader: (1)

I am pretty certain the injectors are not the restiction also. The restricion is further back down the line. Injectors can flow what you want them to but if you can't get the fuel there in the first place then they will only flow the fuel that you can give them..