This came up in a discussion in the hustle thread and IMO merited a thread of its own because it's good info for most of the 5th gen forum (5.5s).

For the past nearly 2 years, I've had a vias delete (BOP) IM and UTEC extending the rev limiter to 7200. All this time, I had assumed revving out was the best way to get good times and that is exactly what I did for all my old PB runs.

Now I finally have dyno graphs of my car with the vias deleted stock IM and realize the folly in this.

6 speeds shift roughly 1500 RPMs down on each shift, so you're looking at a 1500 RPM zone when determining where you want to shift... These are both taken from the same dyno graph.

Well this is what I've been doing all this time. 5500-7k



And this is what I should have been doing. 5000-6500



As you can see, it drops off like a rock after peak... and holding out to around 6400-6500 RPMs is probably a good thing, but anything beyond that you're just moving closer and closer to that <200hp DE-K territory. ( sorry, I had to).

Moral of the story, unless you have a SSIM... don't worry about shifting at high RPMs. Shift a little over 6k and enjoy your wonderful midrange power.

 

Thanks for the info! I think it's common place to assume that extending the rev will allow for greater times. It just feels like the 3.5 wants to keep running and running. I'm glad you discovered the actual relationship between engine speed/gearing and peak interval under the curves. It's nice to see paper.

 

Nice job Sparks good info here.

 

With the BOP, 6500 rpm was perfect in my 4AT, ought to be just the same in my 6MT. Just need to order it....

 

4AT's have horridly longer gears, so this may or may not apply to the 4AT's, of course a personal dyno and further analysis should be required for quantitative proof.

I shift beyond stock redline because I can and because of this:

4AT w/my mods, 2nd gear vs 3rd gear.
I always put down less in 2nd But considering my cars mods, my HP @ 7100, you can see the downfall of the long AT gear. This graph shows shifts @ 7100, imagine a near stock AT shifting @ stock redline.


Also, for the elementary training for this:
http://forums.maxima.org/1-4-1-8-mil...nsmission.html

 

My car definately feels like the power drops off after 6200ish but the TS flash allows for SSIM in the future, should I decide to go that route.

Sparks...your new IM kind of makes this irrelevant for you personally now doesn't it?

 

But you have a SSIM! You certainly want to rev a SSIM'd car out to redline, a 7k one if possible

 

Here's the whole thing from 4k to 7k. I'd still think an auto without SSIM would want to shift at stock redline around 6700, but admittedly I have not done any testing with one. I would definitely do whatever I could to get a big plateau like mine ended up with on an auto.

 

Never seen the stock redline go to 6700

All of my dynos verified bouncing @ 6550 +/- 50


Here's fully functional VIAS vs tuned SSIM:

 

WOW, Sparks! That plateau is nuts, but does that plunging torque affect acceleration? 6500 rpm has 225 and it drops to 211 at 7000. I never truly grasped why/when horsepower "takes over" from torque to keep propelling the car forward.

An excellent brief, for sure. It provides hard evidence that the guys who wrote up the Optimal Shift Points FAQ knew what they were talking about.

Woah, just had a trippy brain thing: Is this where calculus comes into play, calculating the area under the curve? Figuring out which range has the peak power? At a glance, it would certainly appear that the 5->6.5K range dominates 5.5->7K, but for some builds, it might be close enough to demand actual calculations.

 

Can we not get into the HP formula, pretty please

 

I always thought you should shift a car at 6500 when racing at least. I race my father in laws 72 nova. This can be the difference in seconds at the drag strip.

Oh yeah the nova runs high 10's at capitol raceway. By far the scariest car I've driven

 

so you have a TS or you "plan" on it in the future... if so, where and who are you contacting to get this reflash???

 

i get confused everytime, you gotta at least tell me or us which is SSIM and which is VIAS

 

To make this short and simple without formulas, I'll just quote SGsash because he came up with a better description than I could have.

"Regarding torque/horsepower:

Torque and horsepower have a defined relationship. If you know either torque or horsepower, and you know RPM, you will know the other variable.

To get more horsepower, you need either more torque, or more rpm.


So to summarize:

290 lb-ft of torque at 5000rpm is no where near as good as 230 lb-ft of torque at 7000rpm. The graph to display that relationship, is called horsepower.

(290lb-ft of torque @ 5000rpm = 276hp)
(230lb-ft of torque @ 7000rpm = 306hp)"

It completely depends on your powerband. My father's 455 equipped '71 cutlass was best shifted around 5000 RPMs before the build, but now needs to be shifted at 7000 RPMs with big heads, cams, and headers.

The SSIM line is the one that stays flatter and is much higher near redline.

 

Nice info Sparks, so do you think it is a good idea to do the SSIM mod on a 4A/T without the extended rev limiter, since TS isn't doing them anymore?

 

Not IMO. I think the vias delete gives enough gains in the 3000-4500 territory over SSIM to merit keeping it. I did make 270 whp with the vias delete, after all.

 

As if sparks isn't credible for all of us here, I will this.

 

We're missing an important link to this equation. Each shift point will actually change depending on which gear you are in.

I think it's safe to say that in 1st and 2nd gear it makes sense to shift at redline. while the HP is low the height of the gear makes up for that, still allowing for a strong pull and little or no loss.

I think you would need a 3rd gear dyno (or know how to make an accurate calculation of hp in 3rd based on dyno in 4th and gear height) to determine when the best time to shift would be.

Theorhetically you would want the HP where you shift to match from to match the HP of where you engage the next gear.

 

When I shift at 7200 in 1st gear into second, It still lands at around 5700 in second gear. It's still obvious that a 6500-5000ish shift would be much better.

And as NmexMAX has stated, the stock redline is around 6600, so I'm still advising people to shift near the stock redline. If you read the title of the thread again, it might sink in better.

 

Or short and sweet with formulas (for those interested):

P = M*2*pi*n

where P = power [W], M = torque [Nm], and n = engine speed (rpm/60) [1/s]

Looking at the SI units, it is easy to see that torque is energy (1 Nm = 1 J), and power is energy per time (1 W = 1 J/s). If you are not actually doing engineering problems, use imperial units in:

bhp = (lb-ft)*rpm/5252

Pertaining to the original post, although shifting higher may result in marginally lower torque+power, it might be necessary for quicker times with a shorter final drive (which btw increases the torque at the wheels, improving acceleration) as shifts cost a lot of time. Interesting thread nonetheless. Good info, Sparks!

 

It's not marginally lower, it's 40whp lower than peak power when looking at 7k RPMs.

Now when it comes to a shorter final drive, it's a generally accepted fact that when shorter gearing does not necessitate an extra gear shift, it will improve track times, but it will also cause a decrease in measured power to the wheels. The reason for this is a reduction in efficiency (increased drivetrain loss) caused by the increased gearing down of the engine.

I believe I could see a benefit on the 1/4 mile track going to a spec V 4.1 FD, but could see a decrease in trap speed and dyno ***** numbers by as much as 2%.

Regardless, this thread is purely intended to illustrate that our intake manifolds in stock or nearly stock (deleted vias) form are midrange monsters and increasing the rev limiter could actually hurt performance.

In a roundabout way, it's also an argument for a SSIM to flatten/extend the powerband in conjunction with an extended limiter instead of having it plummet after peaking.

 

I got the Flash last summer. Likely one of the last ones, its been in my sig ever since.

 

Doesn't anyone('cept for sparks) ever read my dyno thread?

Here's SSIM vs stock (fully functioning VIAS) w/ stock rev limit.




Only mod was the SSIM. It does lose power if you don't know how to rock it.

 

Just bought an SSIM two days ago and now I see this. I need to do better research before I spend money on these things.

 

Before you put it on, do some supporting mods, unless you plan on keeping it simple.

If not, sell it, there are many on here with more ambitious plans, if you so do not choose to pursue what some of on here are.

 

This is how you rock it.



wait... something's wrong with that SSIM

 

That's not an SSIM, that's an SSIM^2 ... or S^3IM

 

I bought a Berk intake with it as well. My current plan is to go with a pop-charger for it. Am I on the right track?

 

So it looks like our cars need cams bad!

 

Well my dynos help to evidence that one primary restriction of high RPM power is the intake manifold. Cams will help too, though.

Jay_pee99 made some solid gains going to 264/264 duration 10.8/10.8mm lift cams.

I'm going for something a little extreme like 282/272 11.5/11.0, but won't be sure on that for a few months yet.

 

The most extreme cams I found were Brian Crower 272°/272°. sparks where are the 282's you are talking about at? The great thing about sharing a engine with a 350z is that there are plenty of internal engine goodies. I want that 4.1 stroker kit

 

Tomei makes 280 duration cams (which is a possibility, 280/11.3 intake, 272/11.0 exhaust), and GTM stage 2 NA cams are 282/272. GTM stage 3 are over 300 duration on the intake side!

JWT also makes C9s and C10s (C8s are 272/272 and 12mm lift) that require major head and valve cover clearancing because the lift is so huge on them. You have to call JWT to order C9/C10s because they refuse to sell them without talking to you about your goals and try to convince you to pick smaller cams first.

I would love to go with a stroker kit, but that is giant baller money there. I'm estimating to spend <3000 dollars for an entire built bottom end 11.5:1 compression, all machine work, ported heads (done by me), cams, and my new high RPM intake manifold. Just the stroker cranks alone cost nearly my entire build budget!

Going with wiseco/eagle (Adam at Z1 said he could swap the Z gasket get for a maxima one NP) with this setup:
http://www.z1motorsports.com/350_g35...oducts_id=4265

Only need a few minor things on top of that, plus the cams, and the engine is done.

 

Dang your car sounds like a beast. I would like to see what a 4.1 lt vq can do just NA.

 

Congrats

Very nice. And very nice results. I wonder if the RWD lower would be a better platform for a custom IM. With it you could have six symmetrical (and round) runners.

 

Thanks for the props! Yep that's exactly what my full custom UIM will be using is a RWD lower. Those ports are are very nearly round, and only need minor (1mmish) porting to be around 50MM completely round.

 

I thought this was as good a place as any to post this.

Here, you can see where the 4AT shifts at after the 1st gear shift. The RPM drop quantifies the shift from 7100 RPM. Of course, the RPM is a bit higher from the 2-3. And also, just for the hay of it, it also shows how long the actual shift takes w/ a II.5 VB mod. The X units are in hertz (0.1s).

 

I really want to understand your graph, but the provided info is making that difficult. I assume this is meant to show Engine Speed [rpm] v. Time [ds] (Y v. X). If the units are actually 0.1*s, then, yes, it would be deciseconds [ds], which is so far from a common unit... You do not mean hertz, as that is the inverse of time (1/s), which is actually more commonly used to refer to engine speed. It is helpful to label the axes in Excel, but I don't want to complain. The info is good, thanks.

And yet another great reason to drive a 6-speed.

 

Alright sparks how much will it cost to have my IM all shinny and ****. Peformance wise of course.

 

It's hertz, inverse of time(time^-1, or 1/time), because it is in "units" which are from my sheet, and it is in 1/60.