Spark mod changes on DIY's Site - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 12-30-2008, 08:17 PM   #21
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Quote:
Originally Posted by Joe Perez View Post

This mod will be of theoretical benefit to everyone. It's quite possible that the variance in igniter performance is not just from year to year, but from car to car. When I scoped mine, the actual dwell wasn't being severely affected, but there was some measurable effect.
Come scope mine

Did I mention I ripped the caps off my harness after performing this mod. They are useless as well.
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Old 12-31-2008, 11:25 AM   #22
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Originally Posted by kenzo42 View Post
So do 1.6 users need to modify this as well? Or just 1.8?
We're currently using this sort of mod across the board in the MSPNP lineup.
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Old 12-31-2008, 08:36 PM   #23
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I have one of the really early mspnp's. I'm about to drop $600 in dyno time for my car. Do I need to go get it and send the computer back to DIY to get this **** fixed, or not? I just paid for COPs, so I don't really know what to do here. I'd like to dyno the car once because I'm hardly rich.
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Old 12-31-2008, 08:42 PM   #24
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You're planning to dyno tune the car just prior to making a significant change to the ignition system? Fail.
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Old 12-31-2008, 08:51 PM   #25
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You're planning to dyno tune the car just prior to making a significant change to the ignition system? Fail.
I didn't think the cops were going to get made this year.


I have the car at BEGi, Stephanie is going to strangle me.
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Old 01-01-2009, 12:07 PM   #26
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Last night my car started in 10F without a single hiccup. CRAAAAAZY.

-----------

Deleted to avoid confusion and further questions or concerns.

Last edited by Saml01; 01-01-2009 at 07:03 PM.
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Old 01-01-2009, 01:23 PM   #27
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Originally Posted by Saml01 View Post
Anyone wanna take a guess why my AFR readings are ridiculously rich across the table now?
Because too much fuel is being injected into the engine to achieve stiochometric combustion with the amount of air present?
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Old 01-01-2009, 01:31 PM   #28
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Deleted to avoid confusion and further questions or concerns.

Last edited by Saml01; 01-01-2009 at 07:03 PM.
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Old 01-01-2009, 05:22 PM   #29
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I'm going to be so pissed if I can run 18 psi of BOOOOOOSTTTTTTT with my stock coils after doing this mod.

I'm going to have to destroy some nawzz spraying saturns in the name of Joe Perez just to make things right.
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Old 01-01-2009, 06:42 PM   #30
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LOL'ed at "nawzz spraying saturns".

Nothing is wasted, my friend. COPs are cool in their own regard.

EDIT

Everything I had here before was wrong. I assumed that DIY was populating lower value surface-mount resistors into the R58 and R60 position on the main 3.57 board, however as it turns out they are leaving those at 1k and instead installing a second set of pullup resistors on the daughterboard. For the 9093, these are R1 and R2. You can't see the labels with them installed, but here they are:



The brown-black-brown code indicates that these are 100 ohm resistors. The fourth (gold) band is a tolerance indicator, it merely means that these resistors are guaranteed to be within 5% of rating.

These are taking +5 from the Vref pin coming across the DB37 and using it to pull up the spark output lines directly at the daughterboard. This is fine- it's basically the same as doing it on the mainboard. With the 100 and 1k resistors effectively in parallel, the resulting equivalent pullup is 91 ohms, which is just fine and dandy.

If your daughterboard has different values in this location, you might benefit from replacing them with 100s if you are having trigger problems or unstable dwell.

Last edited by Joe Perez; 01-02-2009 at 01:24 PM.
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Old 01-01-2009, 06:51 PM   #31
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Joe, once again, you are the man. Thanks to Sam for bringing this up.

Yo G wach out fo da naws SaturnZ. They$ stoopidz fa$T. Youz need 30 turboz of boostz fo sho.
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Old 01-01-2009, 07:05 PM   #32
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Hey guys, disregard all my concerns with the richness after the mod(i also deleted those posts).

Im stupid and changed my injector opening time, didnt realize it right away and have been running around with the wrong value.

All is well and the car runs like a swiss clock now, better then it ever has. <knock on wood>
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Old 01-02-2009, 11:51 AM   #33
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Joe, we actually put a second set of resistors in parallel on the mainboard - the MSPNP does not have those resistors swapped out. The changeover happened before we even brought out the MM9495, so all '94 and later ones are using a lower resistance value, and so do most '90-'93 models. The highest total resistance we've ever used on an MSPNP is 500 ohms.
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Old 01-02-2009, 01:11 PM   #34
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Ah ha. You guys are installing additional pullups on the daughterboard. Silly me, I figured they'd have just put lower values on the main board.

The unit in question is a 9093. Through a little reverse-engineering, it appears that R1 and R2 are the pullups, as the DB-37 side of each show continuity to 1G or 1H which are the ignition triggers. The other side of R1 and R2 (the side facing the ECU connector) both show continuity to pin 26 of the DB37, which is the Vref +5 supply. You guys are using Vref to do the ignition pullup?

Anyway, these resistors are both 100 ohm, so I guess I didn't need the pullups I installed across R58 and R60 on the mainboard. Damn, I drove 30 miles to buy those things...

Oh well. With your circuit (1000 and 100) the effective resistance is 91 ohms for If = 55ma on the drivers (plus the LED). So there you are, folks. It's safe to use astoundingly low value pullup resistors on your ignition trigger.
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Old 01-02-2009, 01:14 PM   #35
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Quote:
Originally Posted by Joe Perez View Post
Ah ha. You guys are installing additional pullups on the daughterboard. Silly me, I figured they'd have just put lower values on the main board.
Just easier for us to get all the V3.57s set up the same way.
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Old 01-02-2009, 01:22 PM   #36
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Makes perfect sense from a manufacturing standpoint. Minimize the number of hand operations required on the mainboard and let the pick-n-place robot put the pullups on the daughterboard.

The above writeup has been amended.
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Old 01-03-2009, 12:21 AM   #37
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So I did the resistor mod today. Seemed like a good idea even though DIY hasn't tested it on NB coils (nor do I know if MSM coils differ from ordinary NB '01+ coils).

Then I went for a long drive and datalogged. When I got home and did the VE analysis in MLV, I decreased the minimum RPM from 1800 to 500, to see if the resistor mod would have any impact on my car's idle (where I often get misfire CELs). Analyzed on the "hard" setting.

Attached are before-and-after MSQ files.

The car feels much better with this mod and the new tune! It started quieter and more easily. Also, before with the frequent misfires, if I sat for a few minutes at idle, I could distinctly feel serious vibrations through the shift **** and even through the damn steering wheel sometimes. AFR at idle was too rich, around 10.5, because the car was way too rough at 11-12. Now, after doing the spark mod, the car idles in 11-12 almost as smooth as when it was bone stock! So I'm very happy about that. I also did a 50 to 100 pull (don't tell the police in Millburn, N.J. ) at full 15 psi and the car felt as smooth as it ever has. Nothing but constant torque. Now I'm wondering how much I can increase the spark plug gap and still not have resets (currently it's at .020) .... I guess I'll keep things as-is for now, then try .025, watch that for a while longer, then .030, etc.

I'll also have to keep an eye on cold weather starts to see if it now has too much fuel.

Bottom line, here is one DIY customer who'll be going to sleep happy tonight.

Thanks also to Sam for bringing this up.

PS - My car and I have a long history of declaring problems "fixed" based on short-term results, and then having the problem come back worse than before. So we'll have to see what happens ..... I hope this is as good as it seems though!!
Attached Files
File Type: msq evan_hr_27.msq (35.1 KB, 47 views)
File Type: msq evan_hr_30.msq (35.3 KB, 40 views)
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Old 01-03-2009, 02:41 AM   #38
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Awesome thread, thanks for the heads up joe et al.
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Old 01-04-2009, 10:24 AM   #39
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yes joe, thanks again. You are the wind beneath my wings.
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Old 01-04-2009, 09:31 PM   #40
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Update .... yesterday afternoon I drove 2 hours on the highway to visit a friend for the weekend .... got there and then drove another hour to show off my car's latest mods to the friend .... then drove 2 hours back home tonight ..... and all's still great with this spark mod.

I only had one CEL yesterday - P0507, "RPM higher than expected". Indeed, sometimes my car's idle hangs around 1,500 for a few seconds when I bring the car to a stop, before settling down to normal idle. But the good news is no misfires. So there really is a stronger spark. Both car and owner are giddy.

Threadjacking: I've heard of the "hanging idle" problem in Miatas before but I never saw any authoritative fix. How do I make the idle settle down more quickly without changing the idle RPM itself?
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