Since 1st dyno I have put winter tires (Blizzaks 22) and CrawfordZ cats.


Weather conditions in garage were similar but outside temperature was ~6 F colder today then two weeks ago. I expected to run leaner with cats, but am I too lean now?


What I did not expect was to loose power. I haven’t felt much difference on butt dyno except maybe little quicker rev. After reset, I tried to keep ECU from slipping into granny mode. Did 1 A/F leaner ratio caused loosing 8+ ponies? Or could it be something else?

Thanks

 

what was different on the car between these two dynos?

 

winter tires and cats

 

ic, so on the first one, the car is in the same same state as on the linked one? Also, how do the winter tires be affect the dyno?

 

Yes, same car same state but with cats. I dont think tires had affect.

 

From what Ive read . The going to a softer tire like the winter tires you have on [ and they are reaaaaal soft ] it may effect the rolling resistance on the dyno roller . Did you have stock cats on before ?

 

Yup, stock cats before.

Tires? I don’t know. What I am guessing is that running leaner sets ECU off to different mode. But I don’t know if nor when nor how does ECU tries to protect engine.

Questions that I have is would 15+ A/F trigger ECU and would one step colder spark plugs (NGK LFR6AIX-11 ?) help, or should I take it to dealer and ask them to retard timing 1-2 degrees?

Flushing is not an option for me at this time.

 

you may just got a bad tank of gas . Or maybe the first batch of winter blend . i would fret it much right now . Let it adjust and check it when you have new gas in it

 

Dovla where were you guys.
I went to the shop and no one was there.
was there at 9am and then again at 10:30am when i hgad my appointment.

 

Dovla... i have learned from personal experience that the more you open up the breathing of the motor (especially on the exhaust side) the more you lose low end torque, but whatever you lose in the low end you gain back even more in the upper rpms.

my AFR with the Z-tube, Popcharger, headers, cats, and y-pipe was around 14.2... yours seems to be much higher, especially in the low rpms where it spikes to like 16.2. if my AFR was spiking into the 16's i'd be alittle concerned. you should PM or call MRC Motorsports... they're very helpful and they know the VQ35 inside out... they might be able to shed some light on the situation.

sometime in the next few months i'm going to be going with the UTEC to try to smooth out my AFR and gain some more power. my car dyno'ed at only like 230 (granted it's a 5AT but it had a bunch of mods so i expected at least 240-245).

what kinda gas do you get? like what brand? around here i won't get anything but 93 octane from BP/Amoco, Mobil, or Sunoco (some sunocos have the 94, i get it when i can)... the rest of the gas stations may say "premium" but their gas is far from it. (my friend filled up his stock supercharged F150 HD edition with 93 at a crappy gas station, and he was actually getting serious detonation)

 

Yes, you are too lean. 13.1 is about optimal for power at WOT. Above 14, you are probably getting a little ping that the sensor is detecting and you cant even hear. It will then trim back your timing a bit. You need a reflash or a piggyback of some sort to tune it into range with your mods.

 

Glex25,
I arrived at 10:30AM, there was some Eclipse chick there and very young mechanic? saying that Matt? (dyno operator/owner) called at 10 and that he is on his way. There was only one car before me (GTO making 330HP) and none after me. My 11AM scheduled dyno was done at noon and I left steaming shortly after.

SI_G35Coupe,
Mostly Shell, sometimes Exxon, 93. On the way home before ECU reset, at 5K+ rpm I heard pinging kind of sound but wasn’t sure if it was coming from engine or OEM cats in trunk net hitting each other. After reset and old cats out of trunk next day, sound was gone and bad smell as well.

I have been following UTEC & MRC thread(s), but UTEC is too expansive for me. I might get Chiper from UpRev if/when it comes out and then monitor AF, in meantime I will contact MRC for opinion. Thanks

ballisticus,
So up to 14 is safe A/F on NA. Are there any cheap ping or wideband sensors for carputer on the market? Should I put OEM cats back on the car until AF is somehow made richer or just keep rpm below 4K? Thanks

 

With an A/F that lean,your on your way to a disaster...There is something wrong with that A/F ratio and if the cars were the last thing you changed that is your problem.Your flowing freely now and leaning out your A/F mixture ALOT for some reason and most likely on winterized gas you are experiencing some knocking that you can not hear. I would either get those cats off and see what the stock ones look like,or take it to a different dyno to confirm their O2 sensor is not bunk. The only other option for you is to add some fuel by means on tunning.I like to see N/A cars in the 13.5 range all the way to redline. You also added a mod thats supposed to add HP and it cost you hp in the process which confirms my theory of proper tunning being the key.We had a N/A car running at almost 300whp 2 years ago on a piggyback we were playing with.. We will be getting our dyno in Feb if you could wait,however I would not drive the car like that too long..Also if you can hook it up to an OBDII and see if your getting any codes,you may have a bad O2 sensor..

 

The crawford cats are good, so leave them in. But MRC is right, take it to another dyno to be sure. A wideband will not help you since WOT is in openloop anyway. Your flow is just outside the window of adjustment. Unless you have run leaded gas or some weird gas additive through there I doubt your O2 is bad. Those things are pretty tough. If you confirm the lean A/F on another dyno, a reasonable solution is to send the ECU and the A/F graphs to Technosquare for reflash. They will adjust through the RPM range, bring up the rev limit to 7100, and keep the TB open 100% all the way up. OEM program trims it back as redline approaches. I think they can get the unit back to you in around in 3-5 days.

 

Or he could buy a UTEC and be able to tune his car as he mods without sending his ECU across the country and getting a pretty generic reflash that may not help him...I still think he has a problem with his car, I would like to run a diagnostics on it...Call me this week man..We know the G35's inside and out..