P5 1.8 coil swap project

[danielschweer]

1994 http://cgi.ebay.com/ebaymotors/ws/e...TRK:MEWA:PIC&viewitem=&item=8070523675&rd=1,1

http://cgi.ebay.com/ebaymotors/POWD...019QQitemZ290038385582QQrdZ1QQsspagenameZWD1V


i cant see the difference (uhm)

edit: oh, on the pass side-side, not the passenger side-top right?

 

[Dave_x]

edit: oh, on the pass side-side, not the passenger side-top right?

Yup, I think that's what makes the difference.

 

[Dave_x]

I now have all the pieces for the swap on order. I have a NAPA store a few miles away that sells the coil for $41. That's $2 more than the online price, but I'm sure shipping would have been more than that. Others might want to check out that option.

If you're looking for a 626 valve cover, I found a place called Quality Auto Parts that quoted me $95 delivered. 30 day guarantee.

I sent an email to the people selling the red powder coated cover asking if they offer any other colors besides red, but never heard back. $144 delivered sounds a bit much unless you have a red car.

 

[Kansei]

And yeah, on the side-side

the powdercoated red is such a loud red it makes my head explode

 

[pasadena_commut]

based on the above statement, different resistance will cause a different spark duration, which CAN cause bad firing.

Spark duration is not very important, what is important is the time at which the spark starts. When the spark first arcs the fuel mixture will ignite and burn outward from that point. (The gap is small enough to think of it as a point.) Once the fuel in the immediate vicinity of the spark has ignited it will matter not at all if there is still a discharge across the spark gap as there won't be anything there left to burn.

In the link he started with resistances similar to typical plug wires and went way up from there. The smallest he tested was 5000 Ohm. The nominal
resistance on the P5 long wire is 5.6-12.1 KOhm, on the short wire it is 1.9-4.0 KOhm. From here:

http://protege5.ugly.net/01-18.PDF

The take home message to me seems to be that minor changes in wire resistance aren't going to make any difference in how well the engine runs. Higher resistance may help reduce RF noise though.

 

[Maxx Mazda]

...The take home message to me seems to be that minor changes in wire resistance aren't going to make any difference in how well the engine runs. Higher resistance may help reduce RF noise though.

Amen to that. It's completely correct.

 

[Mr.Ames]

correct me if im wrong, but i thought it was the other way around? my dad said when ur plug wires start to go bad, u pick up noise on the AM radio cuz the resistance goes up as the plugs get older and rf noise goes up with the resistance? he's a telecommunactions electrician and certified sound tech, just incase you're wondering

 

[khaosman]

I sent an email to the people selling the red powder coated cover asking if they offer any other colors besides red, but never heard back. $144 delivered sounds a bit much unless you have a red car.

lol, I spoke with them as well. The guy I talked to, Steve, was super nice though and got back to me. Anyways, he said they had a blue one with cam position sensor bung. I do not know if that was in fact a 626 cover or not, as I didn't pursue it (don't want blue).

If I could ever find one of these valve covers, I'd send it there or to a place my friend showed me on Honda-tech. I can't think of what color I'd want though :/ Oh and $95 seems high. Surely you could do better a junkyard. I talked to one place but they failed to get back to me.

 

[Dave_x]

If I could ever find one of these valve covers, I'd send it there or to a place my friend showed me on Honda-tech. I can't think of what color I'd want though :/ Oh and $95 seems high. Surely you could do better a junkyard. I talked to one place but they failed to get back to me.

True, $95 sounds high, but it may be someone's last resort. I tried a bunch of yards around here and came up empty. Maybe Motown isn't the best place to find 626 parts.

 

[Kooldino]

the 1.8 coils are supposedly stronger / better with the stock ecu - aftermarket ecu, you want to stick with the 2.0 coils.

Why would you want to use the 2.0 coils for an aftermarket ECU and not a stock ECU?

 

[aMaff]

I found the right 626 valve cover at the yard down the road from my house. Rogue may be using it on his car. Not sure if the coils will fit properly there w/ the terblow. If they don't, they're all mine

 

[Kooldino]

Although you're correct, you thinking is flawed. Even though 2 of the cylinders may get less spark energy, it does not effect the actual burning of what's in the cylinder. Once it's ignited, the fuel / air mix will burn the same as in all other cylinders, regardless of how strong the initial spark was.

If what you were saying was true, then "spark would be spark", and gap, voltage, etc wouldn't matter so long as the spark jumped the gap. That's just not true.

 

[Maxx Mazda]

If what you were saying was true, then "spark would be spark", and gap, voltage, etc wouldn't matter so long as the spark jumped the gap. That's just not true.

What I was getting at was posted a few posts up. Once the fuel / air mixture has been ignited, more spark or a stronger or longer spark is not gonna make any difference.

 

[pasadena_commut]

If what you were saying was true, then "spark would be spark", and gap, voltage, etc wouldn't matter so long as the spark jumped the gap. That's just not true.

Well, it's pretty close to true with pristine plugs, which is what the link a few posts above this was testing. However in the real world crud builds up on the plugs unless they are kept at the right temperature (which is why heat range is important) and if the gap is too small that crud tends to short circuit the plug and result in no spark at all. On the other end, if the gap is too wide there may not be enough voltage in the ignition system to cause a spark to form. The plug gap opens up slightly over time due to wear (the spark is HOT and evaporates molecules off the surface of the electrode.) So setting the gap right is essential if you want the motor to run well for a long time.

My main point was that a little bit of resistance in the plug wires is irrelevant. The spark will form just fine if there are tens of Ohms (stock plug wires) or even as that experiment showed, much larger serial resistances. So the idea that getting rid of all the resistance in the wires is needed, or that resistances must match exactly, isn't supported by any experimental or observational evidence that has been presented in this thread.

 

[njaremka]

Well, it's pretty close to true with pristine plugs, which is what the link a few posts above this was testing. However in the real world crud builds up on the plugs unless they are kept at the right temperature (which is why heat range is important) and if the gap is too small that crud tends to short circuit the plug and result in no spark at all. On the other end, if the gap is too wide there may not be enough voltage in the ignition system to cause a spark to form. The plug gap opens up slightly over time due to wear (the spark is HOT and evaporates molecules off the surface of the electrode.) So setting the gap right is essential if you want the motor to run well for a long time.

My main point was that a little bit of resistance in the plug wires is irrelevant. The spark will form just fine if there are tens of Ohms (stock plug wires) or even as that experiment showed, much larger serial resistances. So the idea that getting rid of all the resistance in the wires is needed, or that resistances must match exactly, isn't supported by any experimental or observational evidence that has been presented in this thread.

then there would be no need for maintenance on the plug wires, or the need for a factory spec on resistance in the facotry wires, or no need to run any certain plug type (other than thread pitch), or any need for coil pack maintenance, etc., etc., etc.

 

[pasadena_commut]

then there would be no need for maintenance on the plug wires, or the need for a factory spec on resistance in the facotry wires, or no need to run any certain plug type (other than thread pitch), or any need for coil pack maintenance, etc., etc., etc.

Plug wires: the manual just tells you the nominal resistance values so that you'll know what normal is. If the values measured are way out of spec then you know there's something wrong with the wires and replace them. It isn't that the resistance may have gone from 10 Ohms to 100 Ohms, but that the wire may now be shorting or screwing up in some other manner. The plug wires may need to be changed for any number of reasons, including cracked rubber and corroded connectors.

Plug type: this matters not because of spark or no spark, but because the engine expects the start of ignition to be in a particular place in the cylinder. Also the heat range of the plug must match the engine spec or it will foul or wear too fast. That said, it probably is true that any plug that fit the threads would let the engine run - for a while, and maybe not very well if the geometry was way off.

Coil pack: There is no coil pack maintenance per se. It's not like you can service the interior windings. If the coil pack craps out it won't produce enough voltage and the plugs won't fire, so then it must be replaced. Sitting as it does on top of the motor it's apparently a lot more prone to failure than would be a coil located in a somewhat cooler and less vibration prone environment. Hence one good reason to do the 1.8 coilpack conversion.

Getting back on subject, I cannot recall a coil failing in any of the cars I've owned, all of which lived to a ripe old age and all of which used 4 plug wires. I did replace a few sets of plug wires, but we're talking cars that had been on the road 15 years and had 150k miles on them. Conversely, the P5 coil packs mounted on the motors don't seem to anywhere near that reliable. So mounting the coil directly on the motor doesn't seem to have been such a great idea to me. What exactly was the benefit of that supposed to be?

 

[Kooldino]

What I was getting at was posted a few posts up. Once the fuel / air mixture has been ignited, more spark or a stronger or longer spark is not gonna make any difference.

That's exactly what I'm disagreeing with. Granted, it won't make a huge difference, but for instance I've seen dyno tests that tested several different types of plug wires on stock Honda Civic, and there was something like a 7whp range between the best and the worst wires.

On top of that, I've changed different things on my car...plugs, wires, etc, and was able to feel the difference instantly. When I first upgraded to Sparkco wires back in the day, it smoothed out my idle. Different plugs with different amounts of gaps have different effects on the car.

Spark is not just spark. There are differences in gap size, heat range, voltage, etc, that will all effect the burn.

 

[Kooldino]

So mounting the coil directly on the motor doesn't seem to have been such a great idea to me. What exactly was the benefit of that supposed to be?

It was probably supposed to eliminiate the possibility of bad wires being as you're only using half as many now.

 

[Kooldino]

http://www.tprmag.com/issue/4/4_wires.shtml

 

[pasadena_commut]

http://www.tprmag.com/issue/4/4_wires.shtml

From that link

Resistance versus Performance

There is a great perception in the performance community that the lower the measured resistance of a wire than the higher the performance that the wire will deliver. As the results of our test show, this is not a true statement. The performance output of the engine was not a direct function of spark plug wire resistance. In fact, the used stock wire with the highest resistance outperformed one of the lower-resistance aftermarket wires. The bottom line is that spark plug wire resistance is really a marketing tool rather than a purchasing consideration.

It would have been nice if the dyno sheets all used the same X and Y scales. Unfortunately they didn't. Even so, the difference between the wires looks like experimental noise to me. For instance, the maxpower point cited is between 230 and 234 for all the wires, and the runs on the OEM wires covered that range all by themselves. That is, there's no evidence here that any of these worked better (or worse) than the others, at least in terms of dyno numbers. Given these graphs, how the OEM wires "outperformed" one of the other wires escapes me.