I finally got out to the track to test out my 5/16" MD plenum spacer. My previous best with a Z-pipe and a slightly modified Power Duct was a 14.32@97.73mph with a 2.15 60' in density altitude (DA) conditions of around -30'. Today at the same track, the DA was 1,210' so unfortunately the conditions were far from ideal. The only changes to my car since last time out was:

1) MD spacer
2) Newer replacement Avon MS550 tires

The track setup was the same. No spare, everything out of the trunk, and a 1/4 tank of 92 octane.

Today my best run was a 14.42@99.87mph with a 2.21 60'. With a few other 14.4s@99.6+mph with low/mid 2.2 60 foots. So what I saw today tells me the DA definitely hurt my ET a bit, but my MPH was REALLY good. I almost cracked 100mph. I ran three 99.5mph+ traps. My prior best trap was 98.2mph. Unfortunately, it appears that the hacked Power Duct (cover that goes over the front of the airbox) teamed with the spacer, does impact sub 4000rpms performance. My car felt boggy as hell off the line and my 60 foots proved that. Sitting in long lines probably didn't help either. Regardless, the spacer did help and does work, but it does appear that at least with the auto cars, initial acceleration is hurt if you've modified the intake. I reinstalled my unhacked Power Duct cover and the lowend does feel better. I've known the throttle response was better the spacer and stock Power Duct cover, but I just love that sound of the hacked cover. I guess with the spacer and hacked cover, the MAF isn't very happy. I wish I had brought the stock cover with me to the track. Oh well.

Well there you have it. I wish the data was better and I wish I could say the spacer improved my ET, but the difference in conditions influenced the performance negatively. The good news is the spacer did improve topend acceleration by about 1.3mph to 1.6mph, even in worse conditions.

 

the z tube is not the hacked intake you speak of correct?

I am thinking of picking up an auto 2003 soon. and would like to do a few basic things. Possibly a test pipe/spacer/intake.


are you contemplating the 3.5 gearset?

 

Spacer or no spacer 14.42 seconds is a respectable time for a G35. Nice driving.

 

Correct. The "hacked" air box I speak off is a lid/cover on the G35 airbox known as the Power Duct (it actually says this on the cover). You can remove the cover and open up the airbox opening by about 30%. This yields a deeper induction sound, but it also exposes the airbox to engine heat and takes away the natural pressuraztion effect of the stock airbox.


Nope. I use to have a set a 23" tall DR radials left over from my Maxima that I used on my G35 for about 3 passes. On the same track day, I also ran my 26.3" tall OEM 17s. The 23" DRs gave my G an effective gear ratio of 3.55. What ended up happening was the shorter gearing forced a shift into 4th about 200 feet short of the finish line. The shift into 4th killed my MPH by about 1.5mph and ET by about .1. I came to the realization that the 3.5 gear set was not benefical to 1/4 mile performance. My 1/8 mile times improved, but my final 1/8 mile times were a bit worse.

 

I was wondering what is your fuel cutoff in manual mode? Mine cuts off at 6900rpm in manual mode vs the 6600 in auto.

 

I was tapping the limiter in 3rd gear just before I hit the finish line. It was indicating 6700-6800rpms; however, according to my data logs the tachometer is off by about 200rpms (reads high).