Michael - I hear what you're saying but trust me, when you take the cats out, the 02's heat up MUCh faster than they normally would and reach a higher overall temp. This is the very reason that most OBD2 equipped cars throw a CE light for cat efficiency when you remove the cat(s) and install test pipe(s). Not only do most ecu's measure the temp the 02 sensors reach, but also the rate they reach that temperature in. This does not happen in WOT conditions, when the car is in open loop mode. In open loop, the ecu runs one of its several preprogrammed maps. However, cars tend to throw the CE light for cat efficiency when highway crusing - when the car is in closed loop and the ecu is monitering all sensors to try and maintain a stocih mixture. We do not have 2 pairs of cats - we have one pre cat cat per cylinder bank (consider it in the downpipes) and one main cat between the straight portion of the "Y" pipe and the cat back. The 02 sensors are heated, so they heat up very quickly.

I am very surprised by what your claim about the knock sensors are - any proff to show this is in fact how they work?

An engine at 14:1 under all load conditions is just plain scary and dangerous in terms of longevity ....even on race gas. Under light throttle or light crusie, 14:1 is perfectly fine....but once TPS reaches around 50%, regardless of the gear, the car needs to run rich....the level of richness will depend on several factors and thats what the ecu is there to compensate for. The datalogging I have done with my own car so far shows an average A/F ratio of between 11.8:1 (higher rpm ranges) and 13.5:1 (lower rpm ranges) under most accelerating driving conditions (over 50% TPS) regardless of the gear I was in. Anything less that this, and you are simply not getting max spark advance, which causes all sorts of problems. I would not adbise you run 14:1 unless you plan on runnign on alcohol all the time.

There is a split second between the time the knock sensor picks up knock and timing is cut - you can clearly se this on the datalogger. No amount of detonation is a good thing. Detonation is simply unacceptable in any application, at any rpm range. While the car might be able to get away with low knock counts without inducing a timing reduction, detonation is to be avoided at all costs - advising people otherwise is beyond misleading - its plain wrong. Not sure who taught this method to you, but its a recipe for disaster every time.

Try it out sometime - using whatever form of fuel control you typically run (SAFC, Emanage, SAFR, etc), and leant eh car out across the board. Compare your timing maps under these conditions to the stock timing cirve of your car and you'll immediately see what I am talking about. This does not mean there is not room to lean teh car out - as we know, nearly every stock car runs ecessively rich from the factory for reasons I have already mentioned. As we lean the car out a bit to optimize the A/F ratios, you'll also find that the ecu responds by giving a bit more igntion advance. however, go too far, and the ecu will kick things back - again, the datalog will show you this (not by knock counts since most OBD2 based loggers will not show "knock" as a paramter, but you can see it as a strong dip on the timing curve). This tells you you have gone too far, and the ecu knew it, and replied.

 

Since all the gear heads are here posting technicals, I have a couple question. Sounds like you guys know your stuff! TS
did my flash with the Procharger on and everything else except the RT Cats.

I do not think I need a reflash based on what I see and how my car runs for the *RT Cats alone.* My car runs and sounds great, guages are in spec and it pulls like a rocket. When I left TS with my Procharger and semi wide open exhaust (with stock cats) I was 11.5 measuring just before the cat in the pipe with a test cat of theirs they use. My bung is located in the new RT Cat pipe just after the header but before the cat. This is how it was before and this is where the muffler shop kept it. Most Dyno Jet locations (very popular nationwide for tuning and dyno's) use a tail pipe sniffer to test your A/F and you get a 2 page print out. I remember when my car was N/A at 246 rwhp I did see some high 13's and almost 14's on the printout. If I am at 13 at the tail pipe does the *real* number (at the pre cat location, like TS measures at and where my bung is) read richer? In other words, as the exhaust travels farther out the exhaust does it read leaner? The reason I ask is most people here go to dyno jet locations and use the sniffer route for A/F and the new fear everywhere I read now seems to be everyone is running lean. If I am at 11.5 at pre cats am I also at 11.5 at the tailpipe on the Dyno or in real life? If not the Dyno Jet is useless for tuning on FI accurately isn't it? All FI apps should be tuned at the precat for pin point accuracy?

Second question, I flashed at TS on stock platinums stock heat range plugs, of course my timing was changed for the ATI. I am changing my oil Tuesday and now I want to switch to the recommended one heat range colder NGK's recommended by ATI. Will this effect my current TS flash (changing plugs heat range?) I hope not and I know it sounds like a dumb question but the Ultimate Z car with my exact setup flashed with the stock NGK plats and later went to add the NGK colder Coppers and the dang thing wouldn't even idle right. He had also added a JWT flywheel that lowered his idle too low and he had to raise it to like 900 so I am hoping that mine will be ok with these RT cats *and* when I switch plugs! Bottome line is the TS best feature was changing my timing and I am trying to avoid a reflash because it is an expensive two day trip for me and I am very busy with work. The quote I got from the Ultimate Z car owner was "it doesn't even run right, we put the platunum stockers back in and it ran perfectly." This seems odd to me, is this what I should expect?Thoughts or advice?

 

OBD-2 equipped vehicles have an oxygen sensor in front of the cat (upstream) and an oxygen sensor after the cat (downstream) -- in the case of the 350, there are 2 upstream (1 per bank) and 2 downstream (1 per bank after the first set of cats). Then OBD-2 monitors the readings from the o2 sensors and if the downstream o2 sensor reading is the same as the upstream o2 sensor reading, then a MIL is thrown and fault code is set.

I don't know of any factory vehicle o2 sensor that returns more info than your basic 0-1v reading.

I shall defer you to the FSM, page EC-316 where there is a diagram that shows (and labels) 3-way cat 1 and 3-way cat 2. The diagram also shows the upstream o2 sensor ahead of 3-way cat 1 and the downstream o2 sensor between 3-way cat 1 and cat 2. The y-pipe does not house a cat.

I know this applies for the VG30DE[TT] (unsure about VQ35DE). The detonation sensor is a vibration sensor that detects vibration from detonation. Nissan has determined that normal engine vibration is too great at higher rpm to distinguish between normal engine vibration and detonation, therefore, the detonation sensor is "ignored" after 3500rpms. My source: http://www.twinturbo.net/ttnetfaq/ap...tonationsensor (FAQ contribution from Kyle Puckett of SGP Racing) If you also search the technical forum, then you will find people that have read the ecu code / map in regard to the detonation sensor involvement.

The stoichiometric mixture for gas is 14.7:1. It is the ideal mixture for complete combustion. Anything above is lean and anything below is rich. 14:1 should be ok (I remember reading the Audi S4 guys posting 14:1 a/f ratio bone stock!), but I understand your concern if you are worried that a/f may suddenly jump over 14.7:1 (why I personally prefer 12.5:1 for FI application). However, you do not want to run too rich as that will certainly damage at least the o2 sensors.

Michael.

 

12SecZ:

The a/f reading would be more accurate ahead of the cats than out the exhaust pipe (Consider that the cats "clean" up the exhaust gas). However, I do not know the difference in accuracy -- YMMV. I know some dyno shops recommend drilling a hole in the exhaust pipe ahead of the cats for a/f reading, then plugging it w/ a bolt. If you're completely straight through, then it shouldn't matter as much if you're reading from the exhaust pipe.

Regarding colder spark plugs, there are pros and cons. Colder plugs will remove heat from the cylinder quicker (than hotter plugs) and help prevent detonation, however, colder plugs require more time to reach operating temp and will idle crappy until then. Spark plugs are also self-cleaning when they reach operating temp and if your colder plugs rarely reach operating temp, then they'll end up fouling w/ carbon deposits. And those carbon deposits may heat up and promote detonation.

I'd recommend reading your current spark plugs. If they "read" ok and you don't drive like a madman (i.e. staying at high rpms frequently), then stick w/ the normal range plug. If your plugs look like they're overheating (NGK's website has good pics on how to read plugs) and/or you LOVE the sound of 6000rpm, then colder plugs may be worthwhile.

My other recommendation if you're concerned w/ detonation (and you should be!) is to watch your engine coolant temp. Detonation is a seemingly neverending cycle of heat. Detonation likes heat and detonation creates heat. So if your temp needle registers higher than it normally should, then that oughta be your cue to take appropriate action.

Michael.

 

Thanks for the great advice. I am constantly checking all my guages now while driving and my coolant temp is good. I can also stay off boost whenever I want by watching my boost guage. I love my setup. It's winter here so I will "read" them like you said, continue to watch my guages and then swap them out in the spring when it warms up for the next track season. Thanks again!