Hey guys. I had posted a Q as to why my car (92 300E) was faster after a cold start in the tech help question, and what I got back was something along the lines of added fuel from the cold start valve. Ive been looking for ways to speed up my benz short of spending major cashola and as you guys all know... have ended up with almost nothing. Then I got this cold start idea. Does anyone know what controls the cold start valve? Or how it even works? I want to use it to enrich fuel under full throttle, basically wire in a couple of switches similar to a NOS system. Where I can activate the system with a button, and then once activated, the car would enrich the fuel when the acc. pedal hits another button on the floor. Even if this yeilds an extra 5hp under full throttle, I think it would be worth it, as it would hopefully cost next to nothing. Any ideas? (And yes, everybody has already told me performance = fuel+air, and im not an idiot, that is kinda obvious, so don't restate the obvious please... I am hoping that with my sawed off air intake, I will have enough air passing through to be able to use the added fuel.)

First of all, the cold start valve wasn't really designed to act as a full-load, fuel enrichment device.

Second, it may not distribute an equal air/fuel ratio to all the cylinders since it injects from a single location.

If you really want to learn about your fuel injection system, I would suggest you purchase, "How to Understand, Service and Modify Bosch Fuel Injection & Engine Management" by Robert Bentley. It covers the design, operation, and theory behind all the Bosch fuel injection systems.

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Glen Tokuhara
Beauty & the Beast and the wagon that could!

I agree..... that book is great! well worth the 20-30 dollars.

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Current Stable:
01 ML55 AMG
92 500E (a few mods)
87 300E (lots of mods)
00 Chevy 3500HD Diesel Box Truck
68 18' Donzi Marine
06 GT i-Drive7 1.0 Mountain Bike (with GPS!)

PREVIOUSLY OWNED:83 300SD, 87 420SEL, 88 420SEL, 90 420SEL, 86 560SEL, 86 190E 2.3-16V AMG, 94 E320

sweet. Thanks guys. Yea, I had sorta "gleened" that the cold start valve was just a single valve on cylinder 5??? I wasn't sure of this. Since it is true, this method just wont work, because you would have 1 cylinder with more "bang" than the others, producing lots of shaking, and probably doing a whole heck of a lot more damage under full throttle than a nos system would....

Suppose the cold start valve were distibute an even amount of fuel to all the cylinders, and you could rig it up to a switch. It would still not do a single thing for power.

The limitation to power does not have to do with the amount of fuel that can be put into the cylinders, it has to do with the amount of air. You can squirt as much fuel as you want into any of the cylinders, NONE of it will burn since there is no extra air to burn it. No more power will result, all you will get is a rich mixture.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

Yes, I know you need more air. I was hoping that the ECU would be able to compensate. I use the performance under cold start situations as my example. The valve should be open, and because the car performs much better, more air must be flowing through the engine. (Now, I could be wrong as the "cold start" valve being the cause of increased performance, but nobody has been able to propose a plausable explanation)

Even after the cold start valves injection the other injectors add extra fuel to warm the engine. what i do to keep my mixture constantly rich is put a resistor in conjunction with the one of the temp sensors. ( not the engine temp sender for your guages. ) Most techs don't like this type of mod because of enviromental reasons. I noticed a substantial differance after preforming this modification.
Adam

sweetness... that was the exactly the mod I was looking to do. But, instead of having it run consistantly rich, I think I will wire the resistor onto a swtich, so I can "activate" it when wanted (Stop and go trafick doesn't merit more performance) So, could you give me some details on what type of resistor you used and where you attached it to? Thanks!

Yes, I know you need more air. I was hoping that the ECU would be able to compensate.






The electronic control unit cannot add more air to the engine in any way. How can a computer possibly change the physical structure of the engine? Air flow is 100% mechanically controlled. What you are describing will not work. It defies the laws of physics. If it would, then you would be able to get more horses by unplugging the O2 sensor, start with that and see if you like the performance.

All you will get is bad gas mileage and fouled plugs.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

alright, once again, im not trying to do anything that Mercedes hasn't already done. If you notice, upon a cold start, the benz is fast. Faster than at any other time. Now, this could either be due to A.)Magical teutonic hp gnomes that nobody can explain... or B.) Some type of fuel enrichment that nobody cares to verify ... It is not due to, as other might think, to tranny starting in first gear (My car does that normally), air temp being cooler (In my short life, I have never had the air change 30 degrees in 15 seconds), or me making everything up (Hey, I might be tired in the mornings, but im never drunk) Now, since I have never seen magical teutonic anything...(My mercedes is amazing, but not magical) I would have to go with fuel enrichment. And since the car came with the ability to enrich the fuel automatically from the factory, and produce a little extra hp, I can therefore safely conclude that the ability is there. All im wanting to do is turn this feature on after I have been running the car for more than 30 seconds. Im not asking for a magical *add a resistor gain 500 hp* thing, I just want to see what my car is truly capable of. Im am quite frankly just curious. I am not going to perpetually run my car in rich mode, thereby destroying my cats and my o2 sensor, but will rather use this feature once in a week... tops. Now, for everyone concerned about my car's "well-being" Im sure she thanks you, but you must realize that what im trying to do is similar to turning my car on in the morning, and I don't think any benz ever died from being turned on too much....

badinfo,

i'm curious to see how this works out for you. do youself a favor though and install a fuel/air meter. they're inexpensive, easy to install, and will help you determine exactly what mixtures are giving you the best power. then you can post back here and tell us how it worked.

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dew
86' 190e 2.3L 16v

Adam, where are ya man? This fuel enrichment thing has got me all excited, and I need your help!!

Badinfo,
I found the info you wanted,
Snip the wire to the injection system engine temp sensor B11/2 (rear of cylinder head on left side) - it is a green wire with a red stripe. Then splice in a 470-ohm resistor in series. This has the effect of telling the injection computer to enrich the mixture just a bit at idle. Putting a switch in parallel with the resistor will give the adjustabillity you described previously. I leave mine resisted constant. It dosn't seem to effect emmission controls or the cat.
also the engine controls are driver adaptive so, constantly switching it on and off may fool the controler into operating rong.
Either way have fun experimenting!
Adam

does anyone know how to do this type of hookup with the 2.3L 16 engine. this would prove very useful in allowing me to dial up the boost when i get the turbo buildup completed.

thanks

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dew
86' 190e 2.3L 16v

Hey, thanks a bunch adam, im gonna wire it in this weekend. Do you know what resistance tells the computer what temp it is? Could you put in a varistor and perhaps adjust for more fuel? Just an idea...