Note: this isn't a question. People have been very helpful on here and so I just wanted to pay it back sharing my experiences in case someone can learn from them.

O.k. Here's the scoop. Before my newest additions I had the Nismo CAI/Headers/Exhaust, with that setup I pulled 246. My latest mods were Crawford plenum and cats, and UR pulleys. With those additions I pulled a mere 249. But many lessons were learned.

1) After I did my latest mods I drove the car for a couple of weeks, I had NOT reset my ECU though. When I did my first pull it showed I LOST 20+ HP ACROSS the rpm spectrum Sorry I don't have an image of this pull. Needless to say I wasn't too happy. We couldn't figure out what the hell happened but then I remembered all of the Motordyne spacer tests and they say they reset the ECU between each time they make a mod. So we rest the ECU and voila found some power. But only at the low end. More on this next.

2) As you can see from my pulls I had solid gains at the low end, but not at the top. When you look at my AFRs you'll notice at around 5K my AFRs drop through the floor. I'm in the 10's to redline. Eeeeewwww. No, I don't have a tune. Yes, a UTEC will be my next purchase.

3) I have done a total of three different dyno pulls in this car. 2 with 93 octane gas, and 1 with 100 octane gas. In BOTH pulls with the 93 octane gas I have severe drop-off in HP above 6.5k. Most likely knock sensors kicking in and pulling timing. Why, I have this problem even with 93 octane is still a mystery. I may just have a crap engine that's sensitive to knock. I don't really know. When I get the UTEC though we plan to take some timing out of the high end and see if we can preempt the knock sensors and keep the power. I really don't feel like filling up with 100 octane all the time. It's not exactly cheap

So here are my pulls, one is HP/Toqure, the other HP/AFR.





BTW I know the text is small, but what I was trying to point out were the lines that were baseline (CAI/Headers/Exahaust) and then with new mods (plenum, cats, pulleys). If you can't read it baseline were the lower torque and HP, but higher AFR lines.

Lessons learned.

1) RESET your ECU after doing any breathing mod, don't assume the ECU will just re-learn.

2) You just don't know how your car is going to respond to multiple mods (note I've done everything going in and out of the engine now). I would've expected to be too lean, yet I'm rich and leaving power on the table. Although the car sounds totally different, very badass But I didn't spend this much money to have all bark and no bite.

3) These cars come pretty well tweaked stock, they didn't leave much power back at the factory. Expect to have to purchase a way to tune if you do more than a few air mods, otherwise don't expect big gains.

Feedback is welcome, if anyone has comments, questions, or things I may have missed. Also, these have just been MY experiences and lessons learned, your's may be different, and I welcome hearing them. Thanks.

Matt

 

Your baseline A/F looks good but what the heck happened after that?
Something is really wrong if your A/F when to 10 after adding breather mods.

Somehow, either more fuel is being flowed or less air is being flowed... Can you make any guestimates on which it is?

And with a A/F of 10, there should be no ping...

Trouble shoot the problem before hooking up a UTEC. At this point, a UTEC would only be a bandaid on a deeper problem.

 

On second look at the power graph, it really is something much more than regular ping.

The curve fell 100 HP after ~6300 RPM!

Something is really not right. Do you hear any vibration on the exhaust system or any other place on the engine?

 

Maybe a blown cat? that causes the restricted airflow?

 

Hydrazine, thank you for the inputs. I have no idea what's wrong at this point. The only thing I do know is that i saw the same severe fall off at ~6.5K on a previous dyno pull, and the only time I didn't see it was the one pull I did with 100 octane. The first time I did a pull there was severe audible detonation, so that time I attributed it to bad gas. This last time there was no audible knock or vibration. At least none that I heard.

The cats are brand spanking new. I'd be surprised, but could they be defective and restricting air flow? I would think this would be the least likely culprit. My previous pulls the AFRs were good. The only thing new this time around were the plenum and cats. Could the MAF sensor readings be causing the ECU to overcompensate and inject too much fuel now?

I guess I'm wondering do folks think both the AFR and knock issues really are a physical problem (restriction, vibration), or is it more likely an ECU/electrical issue?

Thanks again for any insights.

 

My first guess is there is an intermittent mechanical vibration somewhere on or close to the engine setting off the knock sensor. Check all the bolts on the plenum and exhaust. Make sure they are all tight.

But that still doesn't explain the low A/F... Can you put your stock air box back on?

Try taking it to the dyno again (with normal gas) to see what happens and post your results. Your Z may have been having a bad ECU day?...
Tony

 

yea i would refrain from doing pulls on the engine and get it check for service. YOu dont want to contribute to the problem by stressing it as much as its been without finding whats wrong. I acutally believe the nismo intake btw isnt helping the numbers aswell do to teh 06s already having velocity stacks and already being a great system as is.

 

Sup matt good luck on your mods i hope everything works out. I stilll have the wheels in my closet there almost comming on .

 

Matt, did you ever get the headers checked to make sure they are tightened all the way down? I am thinking one of the headers is loose causing the knock sensor to go off. Just my guess.

 

When Ross and I did the cats the headers didn't feel loose, but this was also between my 2nd and 3rd dyno runs, after we thought the HP falloff was due to bad gas. So we didn't give the headers a real good shaking to make sure, but while attaching the cats they didn't feel loose. Plus they're such a b*tch to reach I'm not sure we could easily hand check every bolt, but may have to.

 

Good luck with finding the issue. Could be a bad knock sensor?

 

Def find the problem before a Utec and tune, good luck

 

Thanks for all the inputs and advice. I have a question back to anyone that might now. If I do go with the UTEC what kind of data logging can it do? (I know i need to search this, I will). But will it let me know if the knock sensors are in fact kicking in and how how many "knocks" it's counting? Then if I do a pull, have a fat AFR (to ensure it's not detonation) and the UTEC can still "see" the knock sensors kicking in that would almost certainly point to a mechanical noise of some sort, right? Does that seem like sound logic?

Likewise if I see the HP fall off but the knock sensors are NOT kicking in then... well, I'm not sure what that would tell me :-)

Just a shot in the dark but the fall off does tend to happen around 6600 rpm the same rev limit as the non rev-up engine. I'm not even sure what to ask here, but could my rev limit be set to 7k (since I have the rev-up), but something else in the ECU is set to 6600???