Graphical differences between the VE Tables of two setups
 

Someone asked what the VE Tables would look like between say a Holley Stealth Ram on a ZZ4 with a Hot Cam vs a stock TPI setup.

Here is a graphical comparison between the two.

The first is the stock TPI

And this is what a ZZ4 with a Holley Stealth Ram with a cam around around 218-222 I/ 224-230E @ .050

Here is the "differential" between the two

Glenn, this kind of comparison is invaluable, thank you. On a related note: how do the timing curves for these motors compare?

Great graphs to show. You can really see how the TPI setup is tuned for that toque peak made from the tuned runners, and how it is so low everywhere else.

Cool beans baby....that HSR graph helps a lot. I am getting another cam soon and I will have to make adjustments on the VE tables. Thanks Glen. How high do the numbers go above 4400? Mine top out at 99.6@ 80% throttle. I think that's kind of high.

Thats one thing I love about SD is that the VE table really gives a good idea of what the engines torque band really looks like and how changes are effecting a setup.

:nod:

Glen could you post the lower end of the MAP too..Id like to see the idle differences

Seems to me the difference in VE tables is more a function of the power band of the Hot Cam vs the stock cam instead of the TPI vs SR setup. Granted, the VE tables would be different between the TPI and SR all things bieng equal (i.e. same cam, compression etc.) and the TPI torque peak would stick out, but the cam is the major determining factor of where the engine makes power requiring VE table change at higher RPM's. Just some thoughts. I could be FOS.

They both do the same amount, exactly. Helmholtz resonance tuning uses both cam timing (not lift) and intake shape (not flow) to determine the VE curves. It's unfortunate that 2 valve heads flow as poorly as they do on big v8's or you'd find the cam really doesn't "determine" the powerband, it just unlocks it. This is why combo's are called combo's and people that bolt tunnel rams onto a TBI motor aren't putting together a good "combo".

O.K., your reply sent me on a mission to better understand Helmholtz resonance and now I do. I can see how changing the carachteristics of the tuned runner and plenum can move the "sweet spot" of the VE curve up or down the RPM range and even alter the shape (peak) of the "sweet spot" where true resonance occurs and how a tunnel ram uses velocity rather than resonance and flattens out the VE curve. It is also clear why cam timing is critical to achieving that resonance for power and must be matched to the resonant "frequency" so to speak of the intake setup. What is still a little fuzzy is why with better flowing heads, the cam would "unlock" the power band instead of bieng a critical component in where it lies. I'm not trying to hijack this thread, just trying to gain some knowledge.

>They both do the same amount, exactly. Helmholtz resonance tuning uses <
.
I give up, what 'resonance' is being discussed here?
Note, it certainly isn't the intake of a tpi.
A 'quartewave resonant' pipe would be four feet long
at 5000 RPM. Overtones would be even longer.
.
The intake tract of a TPI is not 'tuned' in the sense that I
would use that word. The lenght of the intake tract; its just
what GM ended up with.

A tunneram style intake is as close to perfect as you can get for airflow. It still resonates but the "straight" shot is optimal for airflow.
Why you don't want to put a large intake on a small cam small motor: Throttle responce is junk and the cam and intake don't resonate together. The super small cam in a TBI motor resonates at a VERY low RPM and again at a higher RPM that's unreachable with the crappy heads (can't flow so can't rev). Basically you need to pick an engine powerband through gears, vehicle weight, average speed, and THEN get your displacement figured out, THEN the intake THEN the cam. But we're stuck with "small, medium, large" intakes for the majority off us, the tunnel rams being the best, trust me on this. I'm glad you did some research on Helmholtz so now you understand that cam timing works with the resonance of the intake shape.
Optimum research has a program called Virtual 4-stroke which uses flow and resonance to determine engine characteristics (powerband, efficiency, etc). It's EXTREAMELY accurate but the simulations take hours :( and the software is expensive double :( .

Here's a great graph to analyze. This is from a TPI with a ZZ-9X cam. I personally think the graph clearly shows this as "not a good match".

But the guy that owned it, wasn't actually out for power. He just wanted a car that sounded like it had a lumpy cam and made LOTS of low tq. He got it.

Believe it or not, the lower VE Map is not that critical - except idle. And, in my opinion, is the REAL purpose of the lower VE Table. Ultimately, you should tune it with a WB, but your engine, other than maybe cruising down the highway is seldom below 1500 rpm unless it is coasting to a stop or idling. But you can use the "non-WB part throttle tuning" method described in one of the tuning stickies.

To tune idle, you need to find out what the "kpa and rpm" (with a scan tool) operating range is for your typical idling during "warm up". (The kpa/rpm you idle at as it warms up through the various coolant temps).

Then concentrate ONLY on that area. If during "warm up" you car idles from 1200 rpm cold to 800 rpm hot, and 45 kpa @ 1200 rpm to 60 kpa @ 750, then concentrate on getting your fuel set in that range only (45-60 kpa and 800 - 1200 rpm). Then you can "gradually slope a line to the 1600 rpm line in you Upper VE Table from the 1200 rpm area. Below 800, just leave it the same as the 800 rpm line.

Too many guys try to tune a kpa/rpm range that will never happen...like 100 kpa @ 400 rpm or 20 kpa @ 800 rpm. If your engine is operating in those ranges, it's about to stall.

Now, you may have to play with spark a bit, and consider the "additional fuel/spark in the "cold start tables". But I've found this to be the best way to start with"idle".

I wish I could "overlay" these graphs (rather than just show the difference", so you could get a proper sense of "perspective".

TunerCat "colors" the graphs from "lowest to highest", but the "lowest" on one graph may be almost as high as a peak on the other graph.

The TPI graph has a much lower "low point" than the HSR graph. The TPI Graph has a range from 52 - 82, while the HSR graph has a range from 60-84.

And the "value of the 100 kpa@5,600" between the TPI graph and TPI/ZZ-9X combo show the same color, but the TPI/ZZ9-X is higher numerically...they just look the same base on the "color range" of TunerCat.

But it sure would be nice to do an "overlay" or have the "color range" the same kpa values for the two graphs so you would see one as almost entirely red, while the other was almost entirely blue. Maybe I'll ask Tunercat to consider it as a future revision.

Here is the lower VE Table of the TPI-ZZ9X combo. I primarily worked on the 750-1250 rpm and 45-85 kpa ranges. Below 700 rpm didn't matter, so I kept the same reading as 750. Above 1250, I just "smoothed" the curve to meet with the 1600 rpm starting point in the upper VE Table.

I just wish there was a way for me to "highlight" the actual area that I really worked on. Draw an imaginery box from 750-1250 rpm and 45-85 kpa. You would quickly see that everything below 700 rpm is just a copy, and everything below 40 kpa is just a copy until 1200 rpm. (Because the engine is seldom, if ever, operating in that area of the VE table...your tuning something that doesn't happen). ;)

And lastly, here is a lower VE Table for my TPI when I was anal and tried to tune every kpa value for each rpm range.

Yes, it found an interesting "secondary pulse" from the TPI @ 1200 rpm. But, the typical idle range is 600-1100 rpm and 40-55 kpa. It was while I was looking at this graph I realized that nothing matter below 600 rpm and belo 40 kpa (from 600-1200) rpm, and the line was fairly flat from 1200 rpm to 1600 rpm where it met the upper VE Table.

I could have 'guessed' from the majority of this table and it would look very similar EXCEPT for that minor secondary pulse wave at 1200 rpm.

Damn, forgot the graph.

Unless it is a stick tranny. Then the lower VE table is critical. With a stick trans hitting 400 RPM and 100KPa is childs play, too easy to do. And, we don't want the engine to stall. Yes, it is on the way to stalling, but it is important to set up the VE and SA tables to prevent that.

Nor do we want the stall saver to hit, pull the vehicle out, then decay out quickly , as that makes the car then slow down.

I think everyone should tune a vehicle with a stick tranny. Whole different world from the auto's. There are some interesting changes that help in these regards. Having done both auto's & stick's, the stick tranny vehicles are the toughest.

RBob.

Actually, the TPI-ZZ9X (first graph) is a stick and that was when I first tried this method with great results.

And is it easy to hit 400 RPM and 100KPa? Or even 500, 600 RPM and 100KPa? These areas are easy to hit with a stick trans and need to be properly tuned. Even with a engine that idles at 850 RPM. With an engine that idles at 550 RPM, more so. With an engine that idles at 1100 RPM, 400 RPM is too late. . .

RBob.

RBob, I am not going to argue the point further. If the engine is at 500 rpm with a stick and you are not either starting off or stopping, you got problems. That is not a "normal operating range" of a normal running engine in my opinion.

I personally think that if your engine is slowing down below 1400 rpm with a stick, you "shouldn't normally be there" unless you are coming to a stop. And if you're not coming to a stop, you better downshift to avoid lugging the motor.

Of course the more time a person is willing to spend on tuning their VE Tables, the better the overall tuning. I'm just giving people a "quick fast way" to tune the lower VE Tables with 90% of the results with the LEAST amount of effort. This really helps with the "initial hump" of getting "your new baby" started and you don't have a real "starting point".

From there, the guy can spend as little or as much time as he finds necessary. If the person finds a driveabilty issue (whether open loop or closed loop) - then they still need to work the VE Tables more. But if the car is running great, whether in Open Loop or Closed Loop, then move on to other areas. No point "fixing" what doesn't need to be fixed.

Now I understand what you meant by "unlock" the powerband, the whole thing, not just part of it. I guess a good analogy would be switching from 23 degree heads to 18 degree heads. Really fattens up the powerband of a good combo.

Quote:

---

Here's a great graph to analyze. This is from a TPI with a ZZ-9X cam. I personally think the graph clearly shows this as "not a good match".

But the guy that owned it, wasn't actually out for power. He just wanted a car that sounded like it had a lumpy cam and made LOTS of low tq. He got it.

---

The combo part was always clear to me. You gotta match the carpet to the drapes. It was the unlocking of the powerband that I was unclear about. Thanks to both of you guys for parting with these nuggets of knowledge.

I have a friend that has a 383 and t56. The other mods are l98 heads, GMPP cam 234/242*, miniram,38lb ijectors, 1-5/8 long tubes and a few other things. I tuned his VE tables really well. As you can see in the attached pic, it's more or less flat from idle(1000rpms) til 1600rpms. To me that confirms the above quote. I did have to do some VE tuning in crazy areas though. It has to do with low speed cruise in a high gear and stuff that an auto will never encounter....

To keep on topic here is a comparison to my lower ve table. It's from my 406 w/ stealth ram, 242/250* cam,30lb injectors, ported world products iron heads, 1-5/8 shortys...

It's a pity you can't rotate those diagrams. I find that "rotating" the graph can reveal some interesting information. On some fuel (or spark) maps, I find some "view" initially displayed by TC hide a lot of valuable info.

For example, it would be interesting to see that graph rotated 90* to the right on the horizontal plane.

It is interesting to see other combos. On the last one what was your "idle range & kpa range"? I wish I could have "highlighted" the boundary of the ranges I was looking at. I often print them out and then "highlight' by hand. It opens a perspective.

Tim, can you post the upper/EXT VE Table?

MS paint or any other program could be used to highlight areas you're talking about.

I'll first post both the VE tables from my formula. I'll cut and paste the mods. I would also like to add that my torque peak is at 3400-3600rpms(confirmed on the dyno). This is the car that has the 10" 3600rpm non-lockup stall. Here's the other info.........406 w/ stealth ram, 242/250* cam,30lb injectors, ported world products iron heads, 1-5/8 shortys, 11.3 CR, flat top pistons....




here is the lower ve hopefully from a better angle. You can see the idle spot by the "hole" in ve graph(850-900rpms X 60-70kpa). It's leaned out that much for two reasons, 1. to get rid of the nasty exhaust smell, 2. because my fuel pressure is raised at idle due to large cam and decreased idle vacuum. Right now idle a/f is at 15.6 or so....

upper VE...

Now for my friends 383....t56, l98 heads, GMPP cam 234/242*, miniram,38lb ijectors, 1-5/8 long tubes, at least 11.8 CR and a few other things. His car use to run 107-112mph with a custom hypertech chip. I finally talked him into letting me burn a chip for him. I've been at it for a year now and it has ran a best of 122mph on my calibration(no hard parts changed aside from 1:6 rockers).

upper VE for the same 383....

feel free to ask questions on why I made them that way...

Also have a SD bin I did for another friend if you want to look at that. It's a 355 with aluminum l98 heads, siamese runners, hot cam...

Do you have any wideband datalogs of that mini-rammed 383? That VE table confuses me unless you were tuned ONLY the VE tables and not touching the rest of the code. I can't believe that the setup has 3 tuning peaks, one at 2000rpm, another at 3400, and a last a 5000. You also have it "inverted" with different manifold pressures... again confusing me.
I understand the large cam is a tad funky but I just can't figure out why you'de ever remove fuel when the manifold pressure is higher. Could you explain you're tuning method so I can disagree more ;) .

Maybe its got VTEC. I thought the same thing but I guess if it turns in good results, AFRs, and times at the track it doesnt matter.

Ok, lets make it real simple. Take the ve table and circle the area you would like to discuss. We'll talk about changes to that one area then move on to the next. Sound good? Keep in mind that the VE table is a result of what the engine wanted, it's not a direct result of my tuning method for the most part....;)

One of the toughest things to tune IMO is the upper most VE area when you don't live at sea level. How can you accurately tune 100 kpa if you live in Denver, CO and your max kpa in WOT is under 80 kpa due to elevation? The answer is, you can't DIRECTLY.

You can make an good educated guess of what the 100 kpa area might look like based on the shape of the lower kpa values...but that's about it. You need to go to sea level and tune with a WB if you want to directly tune for 100 kpa. Or settle for a good educated guess.

So, if you never drive out your your state/province, it's relatively flat for hundreds of miles, don't ever plan a "cross country trip" and NEVER see 100 kpa, is tuning 100 kpa important?

To me personally it is, but its just my personal preference and I'm lucky enough to live where sea level to 6000 feet is only a couple of hours driving. But I wouldn't fault some one living in Nebraska where they never more than 90 kpa in WOT for not tuning 100 kpa. As I said, the best they can do is "guess" until they actually go to "sea level" and then tune there.

All the cars I have scanned hits 96-100KPA. I live about 500ft above sea level. The odd thing is with the big cam and stall I can hit 100kpa at part throttle. Same for that 383/t-6, his car hit's very odd spots in the VE tables.... I use datamaster's histogram to confirm where the engine is actually riding in the VE tables...

The little known fact is that you can check barometric pressure by scanning the ecm. With the key forward and engine off, you can read the map sensor. 100kpa= sea level. At least that's how I think it worked last time i checked. On the 383 car I was trying to nail inconsistencies . It led me to the baro table (8D)...

I've seen 102 at sea level (on a high pressure day). I usually start my engine before I turn on my scan tool. You can also check the "baro" if you after you turn off the engine, you immediately turn the key back to the "On" position (but don't crank).

Barametric pressure can be put into your aldl data stream if you want. It's in the ram, the ecms measure and store the baro when you do key-on and engine hasn't started yet. It'll also do readings of baro while you're cruising! I haven't looked at the code for very long but it it's there, requires a TPS threshold and I believe a few others.
I had a post up a couple years ago at least about how if you're throttle body is a restriction you'll notice a pressure drop in your MAP readings. It was when half the people thought TBI was an airflow restriction (isn't) and the other thought fuel. Baro was 100kpa on the dot the day I did the test and the pressure drop in 3rd gear at high RPM (WOT) was 97kpa. 3kpa restriction :rolleyes: ... can you say fuel delivery issues is TBI's major problem.
SO, definatly check baro but if you're reporting 80kpa and have tuned everything below that then it's rather easy to "assume" the 90 and 100 area's safely.
The biggest problem with baro is how it effects your TPS open and actual manifold pressure. This relation is what needs the most tuning and I know the TBI code has the following to help when you drive with varied baro;
There's also a table for PE SA vs Baro, Baro Correction vs Tps, BPW Injector Constant Mult vs Baro, Tps Mult vs. Baro, Position After Motor Reset vs Baro (IAC steps), and A/C requested additional steps vs Baro.
As you can see, Baro is used extensively in the TBI code. The only thing is that the injector constant (bpw) isn't modified with baro by default. I found it best to leave it off too. I've driven my car at least 50 times between NJ and OH recording elevations almost 6000', never really had much troubles since most of my tuning has been done between 200 and 800'.

FYI, the 95-100kpa areas in the ve tables I posted look messed up because I used afr tuner to tune WOT. Instead I should of adjusted the ve tables in those areas, then used afr tuner...

It also looks like AE was being tuned into your VE tables instead of with the actual AE tables.

The miniram has short runners, as you know effected the low end ve. So does the cam and t-56 . The cam doesn't "turn on" untill about 3000rpms . His rear gears are 4:56s, so it gets to 3000rpms really quick. This might explain why it looks that way to you...besides, his car can hit 95-100 kpa in the 2000rpm area durring part throttle. That is why I had to add fuel in what apears to be a WOT column...alot of load and high cylinder pressure needs the additional cooling fuel provides.

You’re kidding, right?

The TPI runners are a tuned length… the 4th harmonic falls around 3000rpm, the 3rd at around 3900, and the second at about 5300rpm

Could ypou explain more???

I think that may be the other way around. The fundamental harmonic is at the lowest frequency so the first harmonic would be at 3000 rpm, the second at 3900 rpm, etc.

The explanation is kinda complicated. If you search for 'pipe' and 'harmonic' or 'resonance' you should be able to bring up an article with pictures and other stuff somewhere on the internet.

http://www.fubini.swarthmore.edu/~ceverba1/Pipe.html

That looks like it has some governing equations and stuff to look at. Oh, and the magnitude, or the effectivness of teh resonance, declines sharply with each increasing harmonic so teh resonance effect is really only present with the fundamental harmonic.

Here's some thinking for all of you guys. Helmhotz resonance theory relies on the speed of sound. The speed of sound changes with temperature! So on a cold engine vs a heat soaked engine the VE actually moves up and down on the RPM scale.
11sOrBust, I really think your VE tables have a lot of AE in them. Looking at the lower VE you appear to jam a bunch of fuel in at the high MAP area's which can do 2 things, one it can be the same as your delta MAP AE or it can be suppresing too much timing from showing it's ugly head.
As for the upper VE table, the higher the pressure the more air, it's a simple equation. The rest of the curve depends on pumping losses and throttle body angle. Neither of which could cause your VE to go DOWN as it does.
My feeling is if you trimmed that VE table so that the value at every RPM increases based on MAP, and then you decreased the lower RPM high load areas, adjusted your AE to shoot more fuel in, you'd have a "scientific VE curve". Again, this is only how I'd do it because I love tuning for perfection. Some do it to tune the motor only in it's opperating ranges. Different styles.