# mercedes fuel injectors?



## kindalikeroadkill (Jan 29, 2017)

Has anyone run these on their 1.8 8v or similar? Someone on the forums here mentioned they are a drop in replacement but the thread was pretty old. I went ahead and ordered a set since they are less than half the cost of the part spec'd for my 1984 GTI.

Bosch PN 62274

I can't find a spec sheet for it online, but it was used in Ferraris and Mercedes of the same vintage.

Has anyone tried running these? Thoughts?

FYI I'm running a big throttle body, ported intake, 10:1 pistons, a TT 268 cam, 4-1 header and 2" exhaust with cat delete.


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## 80s_carsorgfto (Sep 6, 2017)

I was at the junk yard the other day and remember them looking alot smaller but I didn't give it much thought. If they're made by Bosch there's a good chance. Maybe just check the flow rates


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## Butcher (Jan 31, 2001)

As a Mercedes mechanic for 30+ years I do know a bit about Mercedes and their CIS systems. There is just a few differences about the injectors that Mercedes uses vs VW. The main difference is that it has a higher opening pressure so the injector has a finer mist. The added bonus is that it's a bit better to prevent vapor lock too. The injector housings are made of a brass [or some other shiny gold metal] but the injector tip is still steel. There is also a seal at the bottom of the injector that helps with sealing.

As with all CIS systems, the fuel injector has no control over flow. There is no such thing as a 'high flow' CIS injector. The flow is controlled by the fuel distributor. People seem to really get mixed up with this and that usually effects they thinking about how to diagnose CIS issues.

There are a couple different injectors for a Mercedes. The differences is the thread pitch where the fuel line attaches to. There is a fine and coarse pitch. Make certain you get the right pitch.


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## kindalikeroadkill (Jan 29, 2017)

*They work fine so far*

Thanks for the feedback, nice to know I'm not totally crazy. 

Received and installed them today and they seem to work fine. Same length, fit no problem with the same rubber seals. Did not resolve my hot start issue but you can't win 'em all 

It might be running a hair better, but hard to tell. 

In any case, I found these all over the internet for <30$ so seems like a win. Thats $200 less for a set vs the VW part.


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## Peter Tong (Jun 17, 1999)

Yes, they will work just fine  i tested them back when i was testing all kinds of CIS injectors to find the ones that flow the max.

Top end flow isn't quite where the stockers were but i highly doubt this will be an issue unless you are really pushing the envelope of NA performance.

Might as well remove the air shrouds if your head doesn't have support for those as well.

PS: just for fun recollections sake, when all was said and done i was getting 420cc/min worth of flow per injector out of my modified Volvo 240 turbo CIS setup. Fun memories 




kindalikeroadkill said:


> Thanks for the feedback, nice to know I'm not totally crazy.
> 
> Received and installed them today and they seem to work fine. Same length, fit no problem with the same rubber seals. Did not resolve my hot start issue but you can't win 'em all
> 
> ...


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## Peter Tong (Jun 17, 1999)

hi,

Believe it or not, i thought the same as you... until i started testing lots of injectors and taking notes of the flow rates. There are CIS injectors that flow 30%+ more, and with some tricks you can get them to flow 50%+ more. With the smaller pulleys on my twin screw supercharger setup i was running lean at the top end. Higher flowing injectors fixed that problem.



Butcher said:


> As with all CIS systems, the fuel injector has no control over flow. There is no such thing as a 'high flow' CIS injector. The flow is controlled by the fuel distributor. People seem to really get mixed up with this and that usually effects they thinking about how to diagnose CIS issues.


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## Butcher (Jan 31, 2001)

If the injector is the bottle neck in the fuel system, yes a different injector may flow more fuel. But rarely is that the case. Of course, your engine is one of those rare cases. 

The main point that is not understood enough is that the fuel distributor controls the amount of fuel going to the cylinder and the injector just sprays the quantity supplied.


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## ny_fam (Apr 3, 2004)

While we are talking about getting more fuel, I'm interested in better understanding how to modify and then tune the CPR, to get more air past the flow plate.
My current understanding is that the bimetallic strip inside the cpr when cold reduces the control pressure- making the flow plate easier to raise, thus allowing more fuel.
SO if you have a way to control the heating of that bimatallic strip you can allow the flow plate to move more easily, and get more fuel. I think in my case I have enough fuel as I have the CIS-Kjet controlled by a wide band controller. I would like to make the flow plate easier to move allowing more air flow into the NA engine. 
So what happens when the control pressure is always low and the engine is hot, with all that extra fuel - does it just go back to the fuel tank? 

BTW -I've been using the Mercedes CIS injectors on my MK1 for years. No issues.
Cheers NY_FAM


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## rabbitnothopper (Oct 19, 2009)

x2 i have 8 mercedes injectors. no problems.

yes the fuel distributor has a return line on the back
the system pressure regulator controls how much fuel returns to the tank vs how much pressure is built into the distributor head


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## Butcher (Jan 31, 2001)

@ny_fam, Your theory is flawed.

The air flow meter is like a teeter totter. The amount of air that pushes/pulls the lever on one side is the exact ratio of the fuel that is delivered on the other side [very simple explanation]. Changing that ratio would be difficult to keep the right fuel ratio since the Germans did a pretty good job the first time around. 

You are correct that if you remove that restriction caused by the air flow meter, the engine will such more air, but you need that restriction so the proper fuel is delivered. 

I'm certain my explanation is not the best.


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## ny_fam (Apr 3, 2004)

@Butcher
Thanks for the instructions. 
Perhaps I just need to check the air/fuel ratio and see where its at and make minor adjustments as needed. Per http://www.timbox.net/technotes/setting-airfuel-ratios/
I suspect the CPR will compensate for temperature in the environment better than a modified CPR.
Cheers


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