Hello fellow enthusiasts I am hoping someone with some experience could tell me what could be the issue of this bad misfire I'm having when I took my car to my local tuner located in Columbus. I had Xavier of ZN Performance (Prior tuner for Rx7Store) attempting to tune the car, but heard from a few member afterwards that he probably didn't exactly know what he was doing even though having as much experience as he did. I'm attaching a mod list at the bottom on this thread!

HERE'S THE PROBLEM:

The car started breaking up and misfiring pretty bad around 6psi of boost, even before my water/methanol system kicked on. It was on and off before this happened and got progressively worse towards the higher RPM's. I pulled two plugs and checked out how they were doing (NGK BUR9EQP's) and they had checked out fine. The tuner rechecked the mechanical timing and had reset it. Checked the GM 3 Bar map sensor and replaced it with another from another Rx-7 in the shop. Car still ran the same. We couldn't find the root of the issue at the tuner and decided to pack our bags and head home.

The next day I checked out the TPS and it was off around +250 Ohms of resistance (Needs to be set at 1k Ohm). I'm gonna pull the wires and coils and check to see if they could be the cause. The tuner was thinking that the problem could be the Low Impedance injectors with the OEM resistor. I HIGHLY doubt that this is the issue.

If anyone could point me in the right direction of what could be the possible issues to check for I would be grateful.

1987 Mazda Rx-7 Turbo II

Engine:
• S4 Block All Original Internals (85k Miles)
• OEM Seals, Stock Ports
• Polyurethane Motor Mounts
• TDX61R Turbo W/ 1.00 A/R
• PTP Turbo Blanket
• SS Braided Lines for Water and Oil Feeds/Returns
• Watercooled TiAL 44mm Wastegate
• OMP Blocked, 75:1 Pre-Mix Ratio
• All Emmisions deleted and Welded Shut on Intakes
• HKS SSQV
• 50/50 Water/Methanol Injection with 550cc Water Injector (AEM System)
• Odyssey PC680 MJT
• FD Alternator
• 4 inch Custom Intake with HKS Mushroom Filter


Exhaust:
• Diamond Fab Manifold and 3inch Downpipe (Heat Wrapped)
• Diamond Fab 4 Inch Exhaust
• Vibrant 4 inch OD Mufflers


Cooling:
• Modified Samco Hoses
• Godspeed Radiator
• Black Magic E-Fan
• GReddy TB Elbow
• GReddy FMIC and Piping (T-Bolts)


Transmission:
• Illegal Garage Clutch
• Act Pro-lite Flywheel
• Polyurethane Transmission Mounts
• Mazdatrix Short Throw Shifter
• Mazdatrix Shifter Bushings
• OEM S4 Clutch Type LSD


Engine Management:
• Apexi Power FC for FD3S
• Banzai-Racing Adapter Harness (No Resistors)


Fuel:
• Marren 1000cc Primaries
• Marren 1680cc Secondaries
• S4 Fuel Rails Series Set-up
• Walbro 400lph pump
• OEM 5/16 Fuel Line
• Sard FPR (Set at 40Psi)
• JEGs Fuel Pressure Gauge


Ignition:
• OEM S4 T2 Coils
• Modified Trailing Coil Pack for Banzai-Harness (Second Igniter Wired In)
• Racing Beat Ultra Wires
• BUR9EQP Plugs in Leading and Trailing

 

Also:

I plan on adding on 10 heat range plugs along with an HKS Twin Power before attempting to tune again.

 

im expecting that excessive water injection has cracked the plugs down in the insulator at bottom of the well

back off the water , lots
,,, also cut back on the premix .. 75:1 is possibly knocking down your fuel octane

have a minimum of 9 in the trailing ( 10 for high boost ) and have spare plugs at hand ready to go next time you get a miss

suggest BR10 EG ( with turned down plug socket ) as a cheaper consumable alternative while you go through set up

 

PS.. second guy this week with the double igniter trick for trailing coils with unexplained miss

would suggest you go for the FD or a 3 or 4 channel igniter and **** off the complication of that double ignitier trick setup



just saying .. i would not want that **** on my car
.. no matter who told me so..
.. that is a potentially dangerous mod for your engine , i simply would rather prefer no trailing spark at all

the law of redundancy says that it will eventually go bad
,, and when it does, it will be wasting spark only to one trailing coil .. , and this will cost engines

it only has to lose sync or continuity for a fraction of a second to make a bad cycle and you may not even pick it up fleetingly on your tacho or commander

when an FD igniter goes bad.. you just lose a spark.. not gain an extra one on the other trailing coil

 

quad spark by megasquirt is just $90 and will allow 3 or 4 channel operation and allow you to run as three or four coils
( the leading will still wastespark if you twin the signal out to two igniters and run two trailing coils )

this avoids any risk with the old flop relays and igniters
and frankly is not much more money than purchasing that second set of trailing coils just for its internal relay and igniter

at that price then there is no practical reason to still continue with the twin igniter trick trying to save a buck but put everything at risk

 

You clearly do not understand how the dual trailing igniters work. There is no opportunity for waste spark, since there is no toggle function. There are individual PFC signal wires for T1 & T2 that trigger individual igniters. If one of the igniters fails then just one of the trailing coils stops firing, it does not fire the remaining coil twice. It is the equivalent of running two smart coils with built in igniters. The only way for the T1 coil to ever see the T2 PFC signal would be if the wiring was done incorrectly.

What you are describing has a higher likelihood with the stock ECU and trailing coil pack.

 

I'm having same problems slight hesitation broke a ra super seal then a s5 rear iron and another s5 rear iron in 2 days on low boost and low timing . **** sucks .I was Running 9s all around last time stock wires and coils . ***** getting expensive and I think it has todo with trailing coils and the cas sensor . I'm gonna try FD ignitor and FD trailing coils. Maybe FD front cover . and running too rich don't think will break irons that fast would kill plugs before that. Not saying banzai wiring don't work my Car runs beautiful besides that . might just get an adaptronics and stop this power Fc crap

 

I'm not sure how sensitive the PFC is to EMI, but with my Megasquirt ECU, I was getting noise in my crank angle sensor signal that was being misinterpreted as extra teeth. This made the ECU momentarily see a much higher or much lower RPM, dumping or cutting massive amounts of fuel. I looked at data logs and its very clear to see. I will heave a spike in RPM (very very brief) and my AFRs will jump drastically and then recover. I have seen it drop as far as 17:1 at 8psi and I'm running 9.7:1CR and 93 octane! I'm not sure if this is even a problem with PFC, but many encounter it with Megasquirt and an easy fix is to switch to the FFE trigger kit.

 

Trash the PFC, don't try to save money on a MegaSquirt, just spend the ~$1200 on some sort of standalone that has software that isn't awful.

-David Guy

 

Power Fc is awesome on FD but Fc idk works fine till u try to get performance outa it. . I'm having hard time deciding between adaptronics and haltec sprint re

 

Use the PFC then use an ECU with real support, and software designed well, then come talk to us!

-David Guy

 

So let me get this straight you call me too tune your car and you stated that everything was working properly. You bring the car there with the timing never set on the motor you bought and install, I spend 1.5hrs taking off your wategate to change 22lbs spring you installed. I told you that 22lbs of boost was too much to run on an S4 block, you want to take it down to 17lbs spring which I also warned you was too much. And I Quote you stating (I came here to make 500hp plus, if it blows it blows). I tried too tune the car and it was miss firing at 6lbs of boost, and running lean. I tried to add fuel and it didn't change anything, I went thru your car and found no resistor on your low impendence injectors which the PFC need to read High impendence. So I informed you that we are done with trying too tune your car. So you decided that you don't feel like you should have to pay for the dyno time of trying too tune your car. I had to argue with you that it is not my fought that the car can't be tune and had too settle with you on a $100.00 with 5 hrs of my day wasted. Next time when you tell a tuner that the car is ready to be tune make sure it's ready.

 

This isn't a posting regarding our tuning session or what it was comprised of. If you have something to add that's on topic feel free to share.

Also, the motor you were tuning on was an original motor, not installed. It was factory timing. The low impedance injectors have the OEM resistor pack which is required for the injectors and ECU to function properly. I could argue back and forth about your tuning capabilities, but it wouldn't really help or change my situation at all.

 

So now you no how to tune, that's funny didn't have a problem with the car I tuned after yours. It did make 542rwhp, I explain too you what I thought the problem was. You are the one who decided to get on the forum stating I didn't know how too tune your car.

 

As someone who works in the industry, zayrx7, you're not making yourself look any better. He made a statement to the effect that he tried to hire you and after the fact found that OTHER folks on the forum found you lacking.

If he was a poor customer, that sucks, but being a child right back isn't the best thing to do. In my opinion.


To the original poster: Sounds to me like you may have gotten yourself in over your head, I think you probably need to take the car to someone who can go over it with a fine tooth comb.


-David Guy

 

I always thought the factory FD injectors are High Impedance. Can anyone confirm that?

 

Yes, FD injectors are high impedance.

PFC in a TII works fine in my experience. 460rwhp @ 16psi with a 63mm BW300SX. 4x FD trailing coils, B9EGV plugs, and pump gasoline.
Your problem does sound like it could be an injector problem. I've seen a similar thing when trying to drive too many low imp injectors off one driver.

 

Yes! factors fd injectors are high imp, he is running low imp injectors with no resistor on the injectors.

 

I'm pretty sure he did some research on who could tune cars, before he decided to give me a call to too tune his car. I'm not acting like a kid, when he states that (I didn't know what I was doing). I have every right to defend myself. The car couldn't be tune because of other issues unrelated too tuning. I went out of my way to try and see if we can get the car tuned, without even charging him for the 1 hour plus for removing wastegate spring, going thru the car to try and source out what the problem might be. Keep in mind that this was not at my shop but at a local dyno shop, I have a real problem when I spend 4 plus hour on a car and the customer feels like he shouldn't have to pay you.

 

Right from banzai racings site, I'm running the OEM resistor box

 

Early build T2's had a resistor box located in the front passenger fender area.

 

did you check to see if it's working

 

I dropped it off at my fabricator the day after we finished our session to get some vibrant mufflers welded in so I haven't had a chance really to diagnose. I'm picking it up today though so I'll try to get an update up on that. The car was running on 12psi on an S5 turbo utilizing Low Impedance injectors prior with the OEM resistor box and Rtek 2.1with no issues so I don't see a reason why it'd just conk out. I'll test it today just to verify.

 

check all your grounds on the car, it should not be breaking up at 6lbs of boost

 

I'm running my OEM resitorbox . I'm daily driving my car Now . just scared of this stupid detonation .