Question For Hotside Owners

[BlownMX5]

I have a '94 Miata, BRP MP62 hotside, no I/C, no 5th injector, 105/65 6-rib FFS pulleys (~7psi max), recently cleaned and tested stock injectors, 190lph fuel pump and good fuel pressure, PC-Pro, fresh engine. I'm getting some ping above 6000 RPMs in spite of < 12:1 a/f ratio. Experience has shown that if I put about 3 gallons of 100 octane in the tank, the ping goes away. So my question is, with the above configuration, should I have to pull any timing to avoid ping on 91 octane Cali gas? It would seem that my current setup is "tame" enough that it should run fine at 10 degrees. Can anyone confirm or dispute this?

Thanks,

Pat. (the other socal Pat ;))

[Tom @ Fast Forward]

Pat,

I sent you an email on the idle issue. Possibly the TPS switch is not set properly and the ECU does not know it is time to go to it's idle settings.

On this issue, when you test 100 octane and the problem goes away, try the BKR7EIX plugs. Could be that you just got a tank of bad gas. Over here, if I buy Shell, I can't accelerate at all until the tank is replaced with decent gas. Even some 101 doesn't help. I think their "Special cleaning formula" is to add water to the gas. ;)

[Serpico]

with no intercooler or fifth injector to cool the intake air temp, you are pumping a lot of hot air into your engine.

I would think you need one of the above or even a water injection system.

How are your coolant temps? Does the pinging only happen when the engine temps are high or do you hear the pinging regardless of the engine temps?

[BlownMX5]

Coolant temps are good. I've had the reroute done and the gauge goes right up to the normal position (11:30) and never moves from there. The fans come on and go off. Also, there are never any "hot" symptoms like, you know it's hot from the way it smells or signs of coolant getting pushed out of the overflow, none of that. So yes, it does it all the time, although I'm certainly going to let it heat up before approaching redline.

I'm really just looking for anyone with a setup similar to mine being able to run with 10* of timing and not get ping on 91 octane. Or, someone that can definitely say "I had to retard timing this much".

Pat.

[cmetzner]

I get more ping in the winter than the summer, here with Calif gas. The only way that I get rid of it is to add some 100 octane.

You can see my car set up at the bottom of this posting.

If I add fuel through the PC Pro with the first 3 modes to reduce ping, my mileage goes to 17mpg. Which means that I must be extremely rich on fuel.

I have just purchased the recommended BKR7EIX plugs and will install them this week and see if it helps.

The only way I ever eliminated ping was to use an FM 02 clamp.

Tom - I know that the PC Pro approach to fooling the 02 reading must be better for most but does not seem to work as well for me. However, I am not your standard set up. I use the stock TB not the BTB and I am using a 115mm pulley not 105. So, I am spinning the blower faster and pushing perhaps less air than your standard set up.

[cmetzner]

Tried to edit but was not able -

The stock knock sensor on the 99 pulls 4* of timing. My SS controller pulls an additional 8* depending on boost. I can still get some ping on tip in.

[BlownMX5]

The stock knock sensor on the 99 pulls 4* of timing. My SS controller pulls an additional 8* depending on boost. I can still get some ping on tip in.

I only get ping at high RPMs. It occurred to me that many of you have knock sensors and although you may be set at 10* at idle, the sensor could be pulling timing up top. But, when I spoke to Tom on the phone last night, he said that the knock sensor stops listening above 6000 RPMs and releases any retarding of timing it might be doing. If that's true then it kind of shoots my theory in the foot.

[Tom @ Fast Forward]

Chuck,

I don't fool the O2. I go for the TPS. It should work on any 99 that makes over 2PSI boost. Any idea what A/F you are running?

[cmetzner]

Tom - not a clue.

[cmetzner]

Tom -

I mispoke. The FM method is to fool the ECU about the 02 reading and then the ECU stops pulling fuel.

The PC Pro sends a 100% throttle position signal and so the ECU goes to a map. Does the PC Pro then alter the signal from the ECU to the injectors?

For whatever reason, I get some ping on tip in using the TPS method. When I adjust the PC Pro map to reduce the ping, my mileage goes into the toilet.

Yes, I know the right way is to spend between $500 - $1,000 on gauges and a dyno tuner to get it just right.

[Silverstreak02]

Tom -

I mispoke. The FM method is to fool the ECU about the 02 reading and then the ECU stops pulling fuel.

The PC Pro sends a 100% throttle position signal and so the ECU goes to a map. Does the PC Pro then alter the signal from the ECU to the injectors?

For whatever reason, I get some ping on tip in using the TPS method. When I adjust the PC Pro map to reduce the ping, my mileage goes into the toilet.

Yes, I know the right way is to spend between $500 - $1,000 on gauges and a dyno tuner to get it just right.

Chuck

I had mine tuned within one hour at the dyno and it cost me $100. It's well worth the money.

Jeff

[cmetzner]

The tuner I went to said he would not tune with the 02 sensor behind a cat converter. So, I will pull the precat on my 99 Calif car; replace the exhaust manifold with a 2001 manifold. He has already welded a bung in the 2001 downpipe.

Then to get the car back to smog legal, I reverse the process.

[chuckerants]

The tuner I went to said he would not tune with the 02 sensor behind a cat converter. So, I will pull the precat on my 99 Calif car; replace the exhaust manifold with a 2001 manifold. He has already welded a bung in the 2001 downpipe.

Then to get the car back to smog legal, I reverse the process.


WTF does he care whether a car is smog legal or not???

Did you take it to MD Automotive in Westminster?

[99mx5]

Ive been reading about widebands and think another possible way to tune would be to replace the primary O2 sensor with a wideband sensor and use the Nernst Cell sensor emulation (narrowband output) to connect the sensor to the stock ECU and simulate the O2 heater circuit on a four-wire sensor with a 50 Ohm 25W power resistor. Of course, A/F datalogging would be necessary. This way you can street tune the car and not have to worry about your A/F ratio. If you must know the power output then you either simulate with software datalogging or go to a "real dyno". ;)

I like your method, I think its worth it to use that hunk of power-robbing hunk of iron for the test and replacing it afterwards. I had an 03 header on my 99 and nobody noticed it. A header would stick out like a sore thumb if you're concerned about roadside checks.

[99mx5]

...I like your method, I think its worth it to use that hunk of power-robbing hunk of iron for the test and replacing it afterwards. I had an 03 header on my 99 and nobody noticed it. A header would stick out like a sore thumb if you're concerned about roadside checks.

I think I mistook you, you use the tubular header to tune and go back to CARB legal after testing.

chuckerants, I think that tuner wants to get a more precise reading when tuning and cmetzner wants to be CARB legal.

( If I call either of you guys Chuck, then it will be like a "who's on first" type of deal :) )

[Tom @ Fast Forward]

You are correct. The PC-Pro sets the TPS to full and then alters the injector duty cycle as needed.

I'll be curious as to the results with the BKR7EIX plugs. Without knowing the A/F it is hard to guess at where the problem lies.


Tom -

I mispoke. The FM method is to fool the ECU about the 02 reading and then the ECU stops pulling fuel.

The PC Pro sends a 100% throttle position signal and so the ECU goes to a map. Does the PC Pro then alter the signal from the ECU to the injectors?

For whatever reason, I get some ping on tip in using the TPS method. When I adjust the PC Pro map to reduce the ping, my mileage goes into the toilet.

Yes, I know the right way is to spend between $500 - $1,000 on gauges and a dyno tuner to get it just right.

[chuckerants]

chuckerants, I think that tuner wants to get a more precise reading when tuning and cmetzner wants to be CARB legal.

I don't buy that explanation Ari. Arizona Dyno Chip never even brought up having to tune a car and neither did MD Automotive in SoCal.

I think Chuck should take his business elsewhere - so sayeth ChuckE. :)

[chuckerants]

Also Chuck, the Zeitronix WB WITH the ability to log AFR vs RPM is only $300. This is THE cheapest WB to give you the ability to log AFR against RPM. Of course this does not include a gauge, but I use a laptop when I need to check the tune.

[99mx5]

I don't buy that explanation Ari. Arizona Dyno Chip never even brought up having to tune a car and neither did MD Automotive in SoCal.

I think Chuck should take his business elsewhere - so sayeth ChuckE. :)

Youre right about that, ADC doesnt have a problem hooking up the A/F sniffer. They just say the A/F may be off by a half point.

[Tom @ Fast Forward]

Actually, they will tell you that it is typically richer by only ~0.2 A/F from what the tailpipe reads. Most tuners don't care much about 0.2.