I have had my Spoon header in for a week now and have noticed something that concerns me; Primaries 1-3 have turned a very dark purple/brown while primary 4 has turned a nice golden colour with only a hint of purple right at the first bend.

Obviously this means that primary 4 is running the coolest but why and has this been observed before?

Here is what I know so far:
- Car is a 1998 with about 40000km on it.
- Did a dry compression test (yesterday) and had the following numbers:
1:195
2:195
3:192
4:198
- Looked at the plugs and all 4 where identical.
- Engine pulls hard, I did a second gear pull from 2k against an unmodified R and gained about 4 car lengths.
- Car is running with the stock ECU.

Is it possible that the injectors are not matched to well? If so why would the plugs not show this? What else should I look for?

Thanks,
Doug

 

In theory, cylinder #1 will run the leanest (hottest) due to the nature of the air (fluid) flow in the intake manifold. The air is coming in at a certain velocity and has to turn 90 degrees to make it into the runners. Inertia of the fluid (air) will resist this turn and more air will tend to flow into cylinder #1. This assumption is made assuming all conditions being equal (i.e. amount of fuel entering each combustion chamber, etc.)

Case in point, when DOHC VTEC B-series motor waterlock which cylinder gets it the worst (indicated by the #1 rod punching a hole in the block)? The number one cylinder does. Out of the dozens of waterlocked blocks I have seen almost all of them that were severe had holes right where the #1 cylinder is.

I am probably overthinking this but it is a possibility. I would not worry about your header tarnishing at different rates in different spots. My Mugen header(s) have all done the same thing. #1 was the most purple and the amount of purple decreased as you went across the cylinders.

-kenji

 

Thanks for the info. These facts make me feel better. Has anyone tried experimenting with matching injectors for each cylinder? It would seem that this would be a better approach then getting a matched set.

Regards,

 

According to Larry Widmer of Endyn, #3 runs the hottest. This is because of it's location and the firing order. Cylinders #1 & #4 are at the ends of the block and therefore don't have cylinders producing heat on each side of them. #3 fires then #4 and #2 next which produces heat on either side of #3. Endyn actually runs #3 a little richer than the other cylinders.

 

Does selecting an injector with a slightly higher flow rate for #3 do this?

How well matched are the stock injectors typically?

Do you think I should be worried about #4 being so different then the rest based on the information I have given?

Regards,

 

I believe they can control the flow rates, individually, with the Motec management system.

How well matched are the stock injectors typically? I have no idea, you could always have RC Engineering test them.

Do you think I should be worried about #4 being so different then the rest based on the information I have given? Well running colder is better than hot. Have you used a good fuel injector cleaner?

 

But I don't have one of these

Where are they?

Not a bad idea since it has been a few years.

Thanks,
Doug

 

Dave SMSP,

Thanks for the info on #3 running hotter. I guess I never thought of it that way.

-kenji

 

I guess you were too busy thinking about Billy Ray Cyrus.

 

i also agree with Dave....when i did a quick test, sprayed some water on each of the, primaries of the header, #3 always evaporated quickest...also # 3 has lost some of its coating and #1 is most purple...

 

Put header wrap over the primaries - viola no more problem.....

 

Buhahahaha... man, i love your posts.... so simple, yet effective.

I've noticed that trend w/u.