MatthewMenze

Hello all,

I just got my turbo installed, began street tuning from a phearable custom basemap. Car runs fine and pulls strongly, building boost smoothly up to wastegate pressure (5lbs), and holds it fine until right around the VTEC crossover, then it starts missfiring/backfiring. According to my wideband guage and datalogging my target AFRs are all pretty close (under 10% difference) and I am tuning them closer as I drive more. In short, everything appears fine and as expected except for the misfiring around the crossover.

Was wondering if anyone has had similar issues? I am also searching currently, but having trouble digging up this specific issue on my engine. I don't want to go much farther with tuning it until I determine it. Just seems so weird that everything else is 100% normal, apart from being rather rich.

Here is my setup:

D16Z6 (stock everything)
Skunk2 Pro Series manifold
65mm Skunk2 throttle body
Ram Horn turbo manifold
3 inch downpipe.
450cc DSM blue top injectors
NepTune RTP
t3/t4 .57 trim turbo

Thanks everyone!

TheShodan

iTrader: (14)

It's a basemap and wasn't meant to allow much boost or timing after VTEC.
This calibration is to get you to the tuner. No boost , no "romping", and running nice and rich..

Be patient, and don't try to "solve" this until its time to go to the dyno to fully tune the system, with engine management

MatthewMenze

Thank you for your advice, I am also thinking the issue is purely a tuning one. I am looking for advice on how to go about fixing it/possible causes.

Dynoing is not practical in my location (4-6 hour drive to nearest one) also this project is a directed study to learn about fuel maps, part of that is street tuning it.

This is meant to be a highly conservative street tuned build.

I am fully aware that the basemap is not a ready to romp item. I am working to street tune from that, following all the research and guidance I can. Right now I am looking to identify the problem so I can resolve it.

Another possible theory I have is that I may be over-running the injector drivers. I am using a stock DSM resistor box with 6.5 ohms resistors, yielding a total resistance of about 9.5 ohms. My research indicated that this is an acceptable, if low resistance. I am going to switch to 10-ohm resistors for peace of mind.

efhatchbackracer

Idk if this will apply but its an idea...the all motor b16 DA integra i built a few years back would break up really bad when it hit the crossover point n wouldnt engage vtec properly, it actually ended up being the ignition card in the distributor n the same thing happened to my buddys h22, maybe try that if u have a spare distributor layin around n c what hapns. Just an idea

TheShodan

iTrader: (14)

4-6 hours is still pretty reasonable for a distance to a tuner. That map can get you there is you drive easy and stay out of a lot of engine load..

But if you want to tune yourself, by all means.. Just get the rest of your software and have at it

preludeNApower

Detonating?

MatthewMenze

It doesn't seem like that at all, and doesn't make sense with low boost, on a extremely rich map, with conservative timing. I suppose it could be. It seems more like a misfire or fuel cut? But the AFR doesn't seem to change, it stays real steady in the low 11s.

Tony the Tiger

Troubleshooting this type of issue is really difficult on the streets.. If you are planning to learn about tuning anyway, you should really consider driving over to a dyno facility where you can make small changes, swap out one part at a time, and keep track of the results.

It could be misfire, improper plug gap, worn ignition components, or a poorly mapped VTEC cross over. Seeing that your setup is very common and with stock cams especially, it probably won't be tuning-related because Phearable's base map can't be that out of wack to cause a hesitation or misfire.

wantboost

iTrader: (2)

Yea plus it isn't safe on the streets to do so, higher gear pulls on a dyno allow the motor to stay in one cell on the map longer so you can "verify" the tune.

Normally initial tuning and wot tuning are done on the dyno to get the car running smoothly, then street tuning will be done for cruising, low load/partial throttle to get the car 100% tuned

sp00led

Yea, anytime I get what seems like ignition breakup I swap in a good set of .025-.028 gapped plugs. If that doesn't fix it then I swap a known good OEM dizzy.

MatthewMenze

Thanks everyone, turns out it was a burned out rotor! Odd, always ran perfect before hand.

Also put in two step colder plugs, and will re-wire injectors with 10 ohm resistors asap for my own peace of mind, and a cleaner install.

Thanks again!

wantboost

iTrader: (2)

A good set of iridium plugs will solve most ignition/breakup issues, as it takes less current to jump the gap, resulting in a much stronger spark and a more complete burn of the intake charge.

Tony the Tiger

I usually start tuning a car with regular plugs (like NGK V-powers) because they are much more forgiving. I can gap them down as low as it requires if I needed to combat against weak ignition components.

If you start with iridiums and the car still misfires, or perhaps the tune is still in its rough stages, you can blow the tip off and it can messed up quite a few things in the motor. I only swap to iridiums when the car has a fully clean tune on it, and then I worry about smooth idle and better response from widening the plug gap again with nicer plugs.

wantboost

iTrader: (2)

Yea I never thought about that before, the basemap and tuning process could actually lead to such high cylinder temps that it could destroy the tip, which for iridum is saying a lot, since the bulk of it on this planet came from meteors entering the atmosphere lol.

Based off the EGTs I've seen while tuning I could believe it, although I tuned my sr20det from start to finish on a set of Blitz Iridium plugs and they are still running strong to this day (tune was 06 lol)