Injector change questions

Pitch those 4 point plugs, they actually hurt flame propogation.
They are not good plugs.

Standard Autolite pulgs are pretty dang good for the Fox. Yes, I do mean the cheap ones.

If you want to find a better plug than that, look for a finer base point. It seems the smaller the base point, the better the flame propogation.


Always start with fuel pressure at 39psi. Don't change it unless there is a problem that you can't correct for otherwise.

Low or high pressure can cause fuel metering issues at low engine speeds, like idle.

Pull your codes to see if your computer has any complaints. Your fuel economy is way too low.
My 408w hit 17 easily, and that was with 3 bores scored to hell from a HG.
There is something wrong, but you may have to look pretty hard to find it.



On the subject of the C&L...
You need to verify that the calibration is correct.
What computer do you have? A9* ?
What sensor are you using? F1SF ?
What size is the sample tube in the MAF? Don't assume the color code is correct.
You will need to measure the sample tube at both the inlet and the outlet, as some of them taper front to back.
Hopefully the calibration was off, and that was causing the poor economy.
(I have listed most of the common C&L sample tube diameters on my website)



Good Luck,
jason
 
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i have an A9P ecu and the MAF sensor is numbered F1ZF-12B579-AA. The meter is (was) an 80mm, supposedly with an orange tube for 30# injectors. It measures .658" inlet and .547" outlet. No codes except constant 67 and intermittent 31,63 (meaning about once a week). Would Bosch single platinum be ok? I think they have a really small tip (like a pencil point).
 
i have an A9P ecu and the MAF sensor is numbered F1ZF-12B579-AA. The meter is (was) an 80mm, supposedly with an orange tube for 30# injectors. It measures .658" inlet and .547" outlet. No codes except constant 67 and intermittent 31,63 (meaning about once a week). Would Bosch single platinum be ok? I think they have a really small tip (like a pencil point).

The MAS is correct for the A9*.
The tube is a little tougher...

From my site
Green .6500" .4850"
Black .4880" .4880"
Red .6570" .5125"
Purple .6500" .5400"
Blue .6500" .5550"
Clear .5650" .5650"
Orange .6500" .5700"

According to C&L's site...
http://www.cnlperformance.com/calibration.html
The 80mm is correct for the A9* ecu, 30lb inj, and Orange tube.

The dimensions you gave for the sample tube were a little off from the Orange tube specs, but I am not sure how that will affect the accuracy of the meter, and I am not sure how accurate the specs I have on my site are.
This variation is one of the major complaints folks have about C&L.

I can't say if that is the issue or not :shrug:





As for the plugs, I was hoping some one else would chime in on the material question...
From a thread several months ago, the concensus seemed to be that the platinum and iridium plugs offer a higher resistance than what the stock 5.0 ignition system was designed for. That is why the cheap Autolites are so heavily recommended.

There is an add in the Dec issue of MM&FF for Autolite XP Iridium plugs. They mention a .6mm 'fine wire' tip.
This add stuck out in my mind because I had just read an SAE paper...
"The Effect of Sparkplug Design on Initial Flame Kernel Development and Sparkplug Performance" written by an independant research outfit; Southwest Research Institute.
SAE will nail you for about $12 to order the paper, but it is an interesting read.

I am considering this plug once my 408w is rebuilt, but I haven't decided yet. I don't even know if they are available for the TW head.

The main advantage for Iridium and Platinum plugs is longer plug life. For folks who don't take their car in for maintenance that is an issue.
However, most of us will change the plugs for kicks on a Sat. afternoon.

Just my opinion, I would like to hear what other have to say.



jason
 
I thought the 4 electrode spark plug might have some benefit when combined with the multisparking feature of my ignition box. BTW, I did have FP set correctly with the 30's - at 39 psi with the hose off.

And yes, the tube WAS for 30's. When I ran that meter with my 24's, the car backfired a lot. Then I unplugged the meter, and it ran rich (thinking it had 19's installed, and a little richer still, to compensate for not having an accurate measurement of incoming air).
 
I thought the 4 electrode spark plug might have some benefit when combined with the multisparking feature of my ignition box. BTW, I did have FP set correctly with the 30's - at 39 psi with the hose off.

And yes, the tube WAS for 30's. When I ran that meter with my 24's, the car backfired a lot. Then I unplugged the meter, and it ran rich (thinking it had 19's installed, and a little richer still, to compensate for not having an accurate measurement of incoming air).

Well, the spark will always follow the path of least resistance. This usually means the shortest gap (assuming all 4 arms are the same).
This means that no matter how many paths you provide, the arc will always jump the shortest gap.
This could be compared to digging 4 ditches branching off of one mud puddle; 3 of which are at an incline (upward slope), 1 which is at a decline (downward slope). Water will always flow down the path of least resistance. The other ditches will remain dry, and useless.
The advantage of multiple point plugs is that as one tip wears, other tips can fall in with minimal loss of spark performance.
Most of us change our plugs often enough to where this is of no concern.
A second concern is that it can be pretty tough to properly gap a 4 point plug. Plug gap can't even be verified sometimes.
Also, from the pics in the SAE paper, it appears that the flame front created by a multi-point plug will not propagate as quickly as a single point plug. The theory is that the 'extra' points physically get in the way of flame propagation.
Small diameter single point plugs performed the best, by a significant margin.

I apologize, but I now have no idea what your 'old' MAF setup was compared to your 'new' MAF setup.

jason
 
I see. Well let me explain the whole MAF situation better, then.

Old:
C&L 80mm MAF
30# tube
30# injectors
39 psi fuel pressure

New:
C&L 80mm MAF
30# tube
24# injectors
39 psi fuel pressure

On the weekend, it will be:
C&L 76mm MAF
24# tube
24# injectors
39 psi fuel pressure
 
I have also always ran just the normal cheap copper plugs. Once I ran some platinums and it made my car detonoate. I went right back to some autolites and never had another problem. I am currently running some NGK's and they seem to be a very nice plug as well. I too have heard that the platinum's and Iridium's may give some more life to the plug but honeslty how hard is it to change plugs for us? I can have all the plugs changed out in 15 minutes or so. Plus the plugs are only like a buck a piece instead of like 4 per plug. I stay stick with the autolites or NGK standard copper plug.
 
you are right about the plugs it seems. i got mine free O:)

I think Free is a good price. :nice:



Obviously the 'New' combo you have listed is going to cause some issues.

You should see a good improvement after the swap of parts this weekend.


If you still have low economy, start another thread with your codes and all.


Good Luck






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