Dave B

I'm am terribly confused by the performance of my Maxima with the VIM manifold. Before the VI, I was running consistent 14.7-14.8s@95-96mph. With the VIM I'm running consistent 14.7-14.8s@95-96mph at the same track. How is this even possible? My dyno clearly shows my car making a butt load more power from 5500-6500rpms, yet I'm no faster or quicker. I just don't get

What are your results? Do you really see a true .2-.3 drop in ET and a gain of 2-3mph? I'm just not seeing it even though on paper and the dyno, this thing hauls butt.


Dave

Soon2BMaxed

maybe you're out of blinker fluid



Trevor




seriously, im curious about this also.

SteVTEC

Maybe your butt dyno is tricking you out into thinking you're going a lot faster than you really are because it's used to that dead zone above 5600rpm on the VQ that you no longer have because of the MEVI.

Since the MEVI causes a LOSS of low/mid-range power, it's possible that what you lose in that area it just makes up for at the top-end, and that the net result is that you gain nothing, at least as far as 1/4 mile runs go. On highway drags you'll still have better performance than the stock manifold, though.

Post up that screen shot you have of your VI vs non-VI dyno again. The only thing you changed in that dyno was just the MEVI, right? I'll save it and then when I get a chance I'll dump it into my Excel dyno comparator and try to see exactly what's going on.

mtrai760

iTrader: (19)

Are you sure your VI is working all the time? (rpm switch)

ericdwong

i dont have one but am curious- do you change the driving style/shifting any?

Dave B

I'm also curious to why you are substainally slower with a Y-pipe. 14.8 without a y-pipe and then 15.0s with a y-pipe? It just doesn't make sense. You think the track timers are off or something since you put your y-pipe on around the same time as I did the VIM? (for everyone else, Trevor runs at the same track)


Oh yeah. It's definately working. I can hear it loud and clear in 2nd and 3rd.


I understand what you are saying, but when you're shifting at 6500rpms in every gear, you land at:

1-2 @ ~3800
2-3 @ ~4800
3-4 @ ~5400

On my car, the VIM makes less power from 3200-4700rpms. At WOT, this lower power is really only a factor in 2nd gear for about 900rpms. I'm not considering 1st because I can come off the line ~3500-4000rpms and the amount of time it takes the engine to go from 3500-5000rpms in 1st is incredibly quick and won't effect much. With the VIM, my 330' is in the 6.20-6.25 range (with 2.2X 60') which is actually slightly better than without the VIM so obviously 1st gear and the early part of 2nd gear isn't a problem.

I may follow Mardigras lead and raise the VI swithover from 5000rpms up to around 5400rpms where my pre-VIM power peak was. We'll see what happens. I think you really need a 7000rpm rev-limiter to take full advantage of this manifold. I feel like I'm driving a Spec-V Sentra (ie the fun gets cut short to early).

Here's the graph:

http://home.earthlink.net/~thunderlt...s/DCP_0014.JPG


Dave

Nismo87SE

Is your 1/8 ET/trap the same too, how about the 60' times? Are you finishing the 1/4 in 3rd or 4th gear? I did a cartest sim of a I/Y/E car vs I/Y/E + VI. If the non VI car stays in 3rd gear I get a 96mph trap, however if it shifts to 4th I get a 94mph trap. The VI car gets a 96mph trap too. However in the 1/8 the VI is 1-2 tenths quicker with +1mph too. Now if your running out of 3rd gear with the VI, cartest shows a loss of almost 2mph with a 6300-6400rpm 3-4 shift. Remember even with 6500rpm shifts your still landing between 4200-4500rpm. Based on your own dyno you made more power from 4000-5400rpm without the VI than with.

Also I did some 75mph accel tests with the USIM vs MEVI. The results show that from the start the USIM is faster than the MEVI till 4.7sec have after the roll. However concidering your 1/8 is around 9.3-9.4 that means that after 14sec the MEVI finally catches up. In cartest at the 14.0 time the car is approximately 80-100ft from the 1320' mark. Another odd thing is given a 75mph roll both IMs produce the same 660' ET although the MEVI is 2mph faster. The 1/4 ET is basically the same with simular trapspeed . I guess j00 get owned by area under the curve or the average of the power band . BTW the USIM has a faster 75-140mph ET than the MEVI by almost 4 seconds .

Soon2BMaxed

you know....i was talking to someone the yesterday from KC (Dester223 from kcsr.org) and he agreed with me when i said that i thought kcir's timing was always varying.....

Nismo87SE

You need either more tire or more rpm. Since more rpm is probably not easy to do, I vote for taller tires.

Dave B

My 60', my 660', my 1/8 mile, etc are all the same ET/MPH wise with or without the intake manifold.

With the USIM, I shifted the 3-4 at 6000rpms and consistently got 95-96mph trap speeds. At sea level, it would be 97-98mph trap speeds. If I held 3rd, I got 94mph trap speeds.

One thing I did notice is that the VIM manifold starts following like the stock manifold at around 4800rpms. However, once the butterflies open at 5000rpms, the power goes flat and doesn't recover until 5500rpms. This is why I'm thinking on raising the switchover.

By having a 7000rpms rev-limiter, I'll be grabbing each gear 500rpms higher.

1-2 4300
2-3 5300
3-4 5900

This is significant because the I would be riding a much more powerful curve.

I don't think I believe that the USIM is faster from 75mph to 140mph over the VIM though. You're talking about 3rd gear, 4th gear, and 5th gear which can make more use out of the VIM. Steve ran a test and it showed the VIM Maxima bus lengths ahead by 140mph.


Dave

Dave B

It would be nice it that's the case. Let's see, you run 14.83@93mph with an intake, muffler, and some B-pipe work. Now you run 15.0@91mph with the y-pipe yet you dyno 178fwhp and 190fwtq?!?!?! You're making only 5 fwhp and 3 fwtq less than what I made prior to the VIM. I ran 14.68@97.79 with that setup.

What was Charle's best today in his G35 sedan? Something like a 14.85@94-95mph? Isn't that slow for a G35?

Dave

Dave B

I thought I'd also add that last weekend I tried shifting at my old shift points prior the VIM and I was .3 and 3mph slower. I went from 14.8s@95 to 15.1s@92mph which was right in line with what Trevor was running in his 96 SE 5 speed, ACT, Y/I/E, USIM.

Dave

Nismo87SE

I agree that makes a bigger difference.
Notice time to speed was faster however in distance vs time the VI is still ahead. From a standing start the VI walks the USIM no doubt. I just put in your dyno into cartest and came up with these #s below. However this assumes your were at sea level though.

2.26' (60')
6.16 (330)
9.4 @ 76mph (1/8)
14.5 @ 97mph (1/4)

However I get these #s without the MEVI
2.28'
6.26'
9.59 @ 75mph (1/8)
14.8 @ 94mph (1/4)

Dave B

Jesus, I'm like Russ posting multiple times in a row

Anyways, I did some calculations. What I'm showing here is TQ in a each gear computed from my dynos with and without the VIM. The goal of determining shift points is to land at an rpm is the next gear at the same TQ as you shifted from. The reason you don't shift the non-VIM at redline is because you'll be slower. These shift points are IDEAL. Don't let anyone tell you that shifting a non-VIM at 6500rpms in every gear is the best for performance. The numbers speak for themselves.

Stock Manifold

1st 6500rpms 345tq
enter 2nd @ 3800rpms 323tq
2nd 6200rpms 237tq
enter 3rd @ 4300rpms 231tq
3rd 6000rpms 173tq
enter 4th @ 4500rpms 182tq

VI manifold

1st 6500rpms 496tq
enter 2nd @ 3800rpms 320tq
2nd 6500rpms 279tq
enter 3rd @ 4600rpms 231tq
3rd 6500rpms 192tq
enter 4th @ 5000rpms 167tq

As you can see, gearing is flat out ideal for the stock manifold. You can also see how much more powerful the VIM is over the non-VIM in the upper RPMs. For the VIM, the stock gearing is horrible. The only way to overcome this is to increase the redline. It appears that the gearing is ~14-17% below ideal. A 7000rpm rev limiter would help things out ~8-10% and a 7500rpm limiter might be ideal. Too bad the engine can't handle it.


Dave

SR20DEN

iTrader: (7)

It has to be the shoes.

Nealoc187

iTrader: (23)

I ran times consistent with my USIM times, at trap speeds consistently 1.5mph higher, on my street tires. I only went to the track once or twice with street tires and MEVI compared to 8-10 times with the USIM.

When I dyno'c my car, I lost a 18ft lb of torque at peak. It would be interesting to calculate the area under the curve that is USED for each gear, and see what sort of differences there are between MEVI and USIM. Keep in mind though my dynos were done on different machines at different facilities, however it was actually colder (but very humid) during my MEVI dyno.

AntGVR4

Sounds like your car wants to join SMC Racing.
The more mods you put on it, the slower it gets.

Ant

I30tMikeD

iTrader: (8)

This is discouraging and confusing. At first the VI was the best thing since sliced bread. Now many are seeing no gains for a $600+ mod in the 1/4 mile.
Neal, I thought in a post last week you said runs between you and brian showed a big advantage to the one with the VI? Is it that it's just not playing a role in the 1/4 mile? Brian told me in a email he saw .2 sec gain.

Nealoc187

iTrader: (23)

Thats why I put the disclaimer that I'd only been to the track once or twice with the VI on street tires. My car is noticeably faster with the VI but it is alot better at higher speeds than you typically get to on the track. Brian's times aren't terribly accurate because I don't think he EVER got a good clean run in decent weather with his car fully modded but without the VI.

The fact remains that I ran a best of 14.41 @ 96.5 without the VI and best of 14.45 @ 96.7 with the VI (street tires), but my traps usually were around 94.7-95.5 without the VI. A 96+ mph trap is rare without the VI for me but with it, it's the norm. Almost every single run was between 96.3 and 96.7 that day that I was at my local track. Next season I'll be making some more runs on street tires and I'll have more data to compare.

Nealoc187

iTrader: (23)

My runs are also much more consistent with the VI. A typical day without the MEVI would have times from say 14.65 @ 94.5 to 14.45 @ 95.7. With the VI I run consistent 14.4s and 14.5s at 96+.

I've got a spreadsheet of the breakdown of every single run I've ever made in my car, so you can compare average times with each mod, incremental times, best times, etc. I haven't updated it since like July so I've probably got 50 runs to add to it. I'll do that this week and post it so people can see it.

deezo

iTrader: (3)

How does the VI feel on autos? Does it feel less powerful than the stock VI util the switchover?

iansw

iTrader: (7)

I gained +.4 Seconds and +3mph when I was not boosted yet with the VI.

Everything i hear about Autos suggesst vast improvements - maybe not so much with 5spds?

Although the numbers are there - 5spds should be faster....

Of course, I ran the track with the VIM installed, just didn't have the switch activate the first run.

Speedtrip Dynoed without then with the VIM installed. I forget his numbers exactly, but they showed a healthy improvement.

IanS

I30tMikeD

iTrader: (8)

Thanks Neal. If you go out to Byron in the spring let me know.

96sleeper

iTrader: (4)

My VIM feels great...maybe it makes a bigger deal on autos because we stay in each gear longer. I went from a best of 14.9 to a 14.7, but the conditions were worse on the day I ran a 14.7, so I am gonna say that it is probably good for 3 tenths on my car. I also picked up alot of mph in the 1/8th mile, from about 73mph to 77+mph. 1/4 mile mph improved as well, from about 90-91mph to consistent 93+mph, all of this on a less than perfect day. I plan to go to the track again shortly, so I will be sure and post my results. I felt no loss of low end btw, but I do have a g-force ECU.

iansw

iTrader: (7)

Dyam. Those are awesome times for an NA Auto.

My best time at the track with the VIM and the SC was 14.7!

Then again, I had a boost leak and no exhaust at the time....

Still.....sick.

IanS

I30tMikeD

iTrader: (8)

I thought autos stay in each gear shorter???????

iansw

iTrader: (7)

Nope - longer. 4 gears vs the manual 5 gears.

96_vqmax

iTrader: (16)

so is that mean the auto should see a gain of .2-.3,i hope it does since mine was auto, so is there any auto out there running with jwt ecu that has go to the track,what are your time vi vs usim?pls post your time and rpm switching point,thanx!

I30tMikeD

iTrader: (8)

Ahhh, I was thinking of it as a 5-speed can shift closer to redline. As apose to an automatic that shifts a little earlier.

Dave B

BSwithTF has the JWT with his VIM-equipped auto. Unfortunately, he's no quicker or faster with the VIM either.


Dave

BSwithTF

iTrader: (8)

I've only equaled my best time. I can say this though, I ran my best non-VI times in the winter (about 50 degrees) and I was getting the same times with the VI in the summer heat and humidity, so I do think it's helping. I should be able to get to the track this Sun. and run in the colder air and see if I can do any better. Hopefully it'll make a difference.

Dave B

Us Kansas and Missouri guys must be cursed with slow Maximas

I thinking about coming down to Mo/Kan either the Dec 1s or the Dec 8, weathering depending of course.



Dave

dwapenyi

iTrader: (3)

Maybe you need bigger tires. Get the usual 15" rims, but instead of getting the right size tire for them, get a tire that is slightly taller, not necessarily wider. That way, the final drive changes and stretches out each gear just a wee bit more. I know that 1st gear can use considerable dilution of power. Also, another benfit to a taller tire would be that you could finish the 1/4 mile well into 3rd gear, not that in-between 3rd and 4th gears that usually happens.

DW

96sleeper

iTrader: (4)

You have the right idea, you just have it backwards. On an auto, you want to lower the gearing with a smaller tire, not raise it with a taller tire. That is why several of us run a tiny 205/50-15 sized tire, it lowers the gearing and allows me to finish the 1/4 mile deeper into 3rd gear, instead of the beginning of third.

dwapenyi

iTrader: (3)

Actually, I was thinking more in terms of the 5 speed manual, but I forgot to mention that In a 5 speed, 1st gear is almost useless on any max with a few mods. It's like slam, spin, next gear! I agree with you, in an auto, the smaller tire will help more.

DW

96sleeper

iTrader: (4)

sorry..I didn't even notice that you were talking about a 5 speed, you do have it right.

BSwithTF

iTrader: (8)

Hopefully the weather cooperates for the rest of the season. Let me know if you decide to come down.

96_vqmax

iTrader: (16)

BSwithTF,pls keep us update with the result,thanx bro, peace.

Nealoc187

iTrader: (23)

Taller tires on the MEVI 5spds are the way to go if you still have a 6550 redline. With a JWT ECU 7000rpm redline this might not apply... I'll let you guys know

maxfreak_98

This is really some disappointing news, fellas . My VI just arrived yesterday and I was really looking forward to having it installed and seeing some good gains. Compared to the rest of my mods, this one "seems" to give the least "bang for the buck".
I guess I'll just go ahead and install it and see what my results are. I should be going to the track either this Saturday or next week.
I'll let you know what my results are.