Today there was an import event at my track so us local Maxima owners decide to make a showing. Weather, once again, is unseasonably hot with temps in the 80-90 degree range and 60% humidity from 1130am on when we started racing. My first run was against ShortChaz's G35. I ran a 15.1@92 with a 2.3 60' to his 15.0@95mph with a 2.3 60'. After that run I realized my VI didn't open. I lined up again and ran a 15.1@94mph with a 2.3 60', then a 15.1@94. My 60's were all 2.3s. The kicker, Soon2BMax (Trevor), beats me in his 96 with a y-pipe, catback, intake, and ACT clutch. I got 15.2@94mph to his 15.0@92mph. Granted I had put all my tools and spare tire back in the car and aired up my tires because I had thought I was done racing, but that shouldn't affect my ET that bad. I left the track severely disappointed in my car. My VI was set at 4800 intially and I lowered it to 4600 with no change in ET/MPH. I would have thought for sure that when I reprogrammed my VI, I would have seen at least a .2 drop to go with my gain of 2mph in the 1/4 mile

I compared my runs today with the runs I did back in August in the same kind of weather. That time I was getting 14.9-15.0@94+mph with 2.3 60s. Comparing the slips, my car today was .2 and 2mph slower in the 1/8th than it was in August? Was my VI not working all day? Has it been working? I was beating Trevor's trap speeds by 2mph and I was slower than him in the 1/8th too. Man I'm ****ed. I rearraged my vacuum lines and cut ~1' of unneeded vacuum line in an attempt to maybe help increase the vacuum surge. I'm also raising my RPM switchover to 5000rpms because I think that when it's hot out, there is a bog if you set the VI too low My vacuum is still a perfect and steady 20 Hg and there are no codes to be seen. We'll see what happens. That redesigned WRX is looking even more appealing right now.


Dave

 

When we dyno'd Bags533's car a couple weeks ago, there was a distinct lag in the HP curves when the VI was set below 5000. We finally got the best results with it set to open at 5200.

Give it a try...

 

check your exhaust leak too; i told you how bad i was running last weekend when i had a leak....hopefully it helps out somewhat.

 

hey do not kill me i am just asking what a VI is and why it was not opening, yeah i just got my car out of the shop need a tune up and all new seals, running twicwe as fast,when is the next time the track will be open i want to see what i runlike i am saying not trying to start stuff just want to see, I am getting springs,intake, exhuast,and short throw.so what are you runing Dave B, and Soon2bmax,

 

VI is a variable intake manifold that you can set to open the valves to a different path so it can breathe better at higher rmps

 

iansw, and now u Dave. Why are all the VI owners complaining about having slow cars? hahaha j/k, i know, weather, and u don't have it set right

 

I'm complaining because of the fact that I have 267fwhp, and still only a 14.7 1/4 mile with a 2.1 60'. That's why. It makes no sense.
My MEVI gave me .4 seconds on the 1/4 mile when I was NA, so I have a totally different problem than this guy does.

Setting the RPM to 5000-5200 will probably solve his problems.

IanS

 

Ian & mzmtg-

Earlier in the week I had calculated the shift points and VI activation RPM for a 5 speed VI using Mr. Cranman's dyno. I just realized that since he has the JWT ECU, he's probably got a bit more midrange power than myself with the stock ECU. Orginally I thought the 4600-4700rpm switchover was ideal, but that might just be for 5 speed guys with the JWT. I think you guys might be right about setting the VI switch to 5000-5200rpms. Neal reported similiar feelings about the 5000 switchover. I removed some of the excess vacuum line and I raised set the switch to 5100rpms. I went out and tested it for about 30 minutes. I did run thru 1st, 2nd, and 3rd. When I hit 3rd, I chirped. I haven't chirped 3rd for quite a while. I went back and it chirped again Maybe my car is running better. It feels like it has a better punch from 4500-5000rpms now. I guess I'll have to wait and see now.


Dave

 

Strange indeed, but 94mph traps are not bad considering you were beating an I/Y/E by 2mph. That tells me that your track is really really slow. Between the conditions, elevation, and maybe being slightly uphill (just a guess). I say this because 92mph traps for an I/Y/E 4th gen 5spd are very slow, which you already know.

What was the breakdown of your timeslip vs trevors? In fact what were the breakdowns of all your timeslips.

Changing the switchover point made the car feel smoother, but I think its effect is almost negligable. Lets say that at 4600rpm switchover you are losing 8hp with the VI open compared to closed. By using a 5000rpm switchover, lets say you gain that 8hp back from 4600 til the new 5000 switchover. In reality, that is only a FRACTION of a second that you are making an extra 8hp, thats not going to show up in timeslips. Gaining 8hp throughout the entire RPM band is borderline noticeable, gaining it in a small 400rpm window between 4600 and 5000rpm is not going to be noticeable at all considering that variation you can see in timeslips from run to run.

 

lets make sure its gonna be cooler before we go out again


Trevor

 

Here's my worst run of the day and it was against Trevor's 96:

Me Trevor

2.33 2.36
6.462 6.378
9.868 9.732
72.32 73.37
12.764 12.604
15.207 15.052
93.50 92.00

My best run:

2.30
6.390
9.790
72.43
12.681
15.117
93.67mph

My best run in August (same weather):

2.301
6.390
9.633
74.61
0000
14.95
94.57mph


What's ironic is that I was faster in the left lane which has a history (for me) of being .2-.3 and 2-3mph slower than the right lane. I raced once in the right lane today and got a 15.1 (VI not working) against the G35. I don't know if Trevor raced in the left lane today or not. Oh well, the my car's a dog and lacks the ability to accelerate hard in the low rpms. It's no frustrating because it runs like new, gets 25-29mpgs (even going WOT regulary), and shows no codes. I'm going to have a VERY hard time justifying putting anymore money into this car if it keeps performing like it does. When it cools off and I run in 60 degree weather, I'd better be seeing at least 14.5s or I'm buying myself a nice Christmas present.

As for the track, the annual Grand Prix Gathering was held at my track last weekend and all the Michigan, Northeast, and Texas guys were ~.5-.8 slower than thier bests at their tracks. The weather was nice and in the 60s and 70s. It's probably a slow track, but it still doesn't help me figure out why my car runs no stronger than Trevor's. Yes, the track is slightly uphill. Three modified WRXs were pulling off 14.7-15.0s@92-94mph today. The only ITR there and with A-LOT-O NA toys (adult driven) was getting 14.6-14.7@96mph with drag radials.


Dave

 

i drive a 95' dave! hehe i never did get into the left lane but i did notice that they sprayed the left lane with VHT twice today and i never saw them do it to the right lane


Trevor

 

Ahhh yeah the slow max blues. I too have been disappointed when I've gone to the track. My intake, Ypipe, B pipe car has never trapped over 93.8 mph. I dont have a VI though.

 

My car is still trapping out far higher than it ever has in hot weather after getting the VI, but seeing Trevor run 15.0-15.1s, it makes me a little disappointed. Trevor's Maxima went 14.8s@93mph (his best ever to date) with just a catback and intake which is wicked. I consistently hit 14.7s@96mph with a intake, y-pipe, b-pipe, and UDP. Maybe there really is something better about the 95 4th gens

I've changed some things around and have fixed/will fix some things. Yesterday I made my runs with the stock 15s and 7 year-old bald RSAs because one of my front 16s got a nail the night before. I put my 16" K1s back on and I never realized how much heavier the stock 15s are vs my K1s. I fixed two exhaust leaks (one at the cat and one at the muffler), removed excess vacuum line, and raised my VI to 5100rpms (feels a lot better). My next order of business is to replace my HKS air filter which is currently grey-green and filthy (normal is bright green). Hopefully this will help things. The car has always felt very strong on the street, but lately when I've run at the track, it's a dawg. I'm not racing again until it's deep in the 60s. Enough with racing in hot and humid weather. I'm also thinking my knock sensor, even though shows no codes, might be overly sensitive to the heat. For the past two years, my car is .5 seconds slower in 80 degree weather vs 60 degree weather.


Dave

 

Traction has never been a problem in the left lane (I always get similiar 60 foots), but the lane just seems to always be slower. I've got numerous slips from the same day and with the same 60 foots showing my car .2-.3 and 2-3mph slower. It's strange. I can remember the same thing happening to me 5 years ago when I had my Z28.


Dave

 

On a side note last I saw, mardigras had his VI set at 5500/5600

Just something tothink about since you both are on boost

Also, you may have heard this 1000 times, check you y-pipe flex section lately?

 

I believe MardiGrasMax set his to 5600 because of worry that having SC+NO2+MEVI would cause detonation problems. I don't believe he ever tested at 5000 for this reason.

 

ah ok..just putting it out there..and I did just read your post about the vaccum problems

 

have you tried lowering your tire pressure?? the last time i went to the track i ran a 2.3 60' with normal tire pressure. when i lowered the fronts to ~28 psi i got my best 60' ever, a 2.19. this helped me achieve my best ET.

 

All my running on street tires has taught me that tire pressure doesn't make one bit of difference in traction, at least it never has in my case. I've pulled 2.1s at 20psi to 35psi, at many different tracks.

 

Ouch. That too much hp to run those times. I'd think you'd be low 14s or even high 13s with that hp.

 

Yeah, I know!

BUT I think my problem at the track may have been that my bleeder valve on my FMU had a bad check valve, causing the BOV to blow off too early because it sensed a vacuum when the bleeder opened.

I fixed it, but won't really know for sure if I'm faster because th tracks are closed for the year.

I do hit 8-9PSI more reliably now, however.

IanS

 

turbo97se, MardiGrasMax, me. Who's slow?

 

this has not been my experience...but if it doesn't make a difference why do so many people lower their tire pressure? are there any other benefits to be gained??