HP TUNERS in DA HOUSE

[TurbochargedBerserker]

More info on the smooth/spikey VE table thing from Chris@HPT.

 

Smooth tables are not a necessity it seems, but keep the transient KR threshold at bay. Spikey tables are more accurate, but more susceptible to burst knock and transient throttle knock (which would need to be tuned out some other way).

 

Based on months of chasing transient kr, I'd still come down on the side of VE table smoothness. You might be a tad more rich in certain spots, but I'd rather be rich than lean going to WOT any day of the week.

[marc_w]

I've been an IFR tweaker since I got my software a while back here... I've been looking into SD tuning, but other points were brought up about modding the MAF table to match up the new airflow.

 

I got into tuning just after the "IFR method" came out. Previous to that, people were just hitting up the MAF and being done with the part throttle stuff.

 

Here is a type of post that I've seen a lot of in the past, that have kept me away from the MAF table.

 

I'm currently running all stock fueling tables right now. I'm at like, +7 at idle, and +3-4 driving. I'm REALLY up in the air as to which way to go with tuning.

[marc_w]

Also, watch for this.

 

http://www.ls1tech.com/forums/showthread.php?t=245518

[SSThunder]

Is this type of tuning better for the SS owners with knowledge? I have no knowledge of anything in this post so would a westers type PCM tune be better for me? Also how much is the software? If I could increase my knowledge I wouldn't care to tune my own, but I don't have many mods at this time(CAI and superchips hand held). Thanks for any info. Very interesting topic.

[TurbochargedBerserker]

Can't read the LS1Tech site atm, but here's the argument I have for changing the MAF table.

 

To borrow an analogy from Chris@HPT, let's talk about holding a sponge over the hood of your car. Pretend that the hose nozzle has a flow meter on it (analogous to the MAF) that correctly meters the amount of water leaving the hose. Pretend that its possible for the sponge to instantly wick up the water from the hose as long as it isn't saturated. As you turn on the water, the flow meter reports that water is going onto the hood, but in reality, no water is hitting the hood (it's all being wicked up into the sponge). As soon as the sponge is saturated, the flow meter becomes correct again, as all the 'new' water displaces an equal amount of water in the sponge, and the displaced water hits the hood. When you turn off the water, the flow meter reports 0 water hitting the hood, but until the sponge dries out, some water still drips onto the hood.

 

To accurately figure out how much water is hitting the hood in those transient periods (water on/dry sponge, water off/saturated sponge) we need some kind of calculation to accurately predict how much water is really on the hood. We can do it by weighing the sponge, etc.

 

In an MAF setup, the sponge is analogous to the intake manifold, water = air, MAF = flow meter. As you go from part throttle to full throttle, the manifold is in vacuum, and the MAF reports all the air rushing into the manifold, but that air isn't filling the cylinders yet (its filling the vacuum in the manifold). This results in a rich reading if uncorrected. When you go from WOT to part throttle, the MAF reports less air coming in, but the manifold is still chockablock full. If you just used the MAF reading, you'll end up lean.

 

VE is the calculation that lets us correct for these two transients in a MAF car. Stock VE tables are the most general, should work in most situations, settings there are. They are derived by some poor guy sitting on an engine dyno and figuring out the settings for each cell in the table. The MAF is a big generalizer in GM cars (Fords make the MAF much more important for correct fueling), that allows the VE table to work in every atmosphere and temperature variant.

 

GM pcms have three basic modes wrt fueling: 1) mostly VE, 2) MAF/VE mix, 3) all MAF. The Mostly VE cells are those low rpm, low airflow cells for which the MAF is nearly worthless (400, 800, 1200 rpm columns - stock, but this is tunable). The MAF/VE mix section is generally 1200-4000 rpm. In this section MAF readings are filtered by the VE calculation. The all MAF section is 4000 rpm and above.

 

A few important things come out of this: 1) the VE table is very dependent on engine set up, FI, freer exhaust, cam, etc. 2) VE is very important for correct transient fueling (and therefore getting rid of transient KR) as well as for proper part throttle tuning between, as is a properly tuned MAF, 3) MAF tuning is ultra important above 4000rpm.

 

On to the MAF... In my case, having the MAF in the pressurized intake tract changes the functioning of the meter. Same deal for draw-throughs I'd expect, although I think the effect would be lessened. In any case, the MAF function is meant to be a 'generalizer' for the SD VE table. Since the airflow is changed for anything that requires a change to the VE table, it stands to reason that the MAF is affected to some degree.

 

I might change my mind on that after reading those threads (404'ing from work today), but I've read many, many, threads about how evil the MAF is, etc., which leads me to believe the stock MAF function is less than optimal.

[TurbochargedBerserker]

I've been an IFR tweaker since I got my software a while back here...  I've been looking into SD tuning, but other points were brought up about modding the MAF table to match up the new airflow.

 

I got into tuning just after the "IFR method" came out.  Previous to that, people were just hitting up the MAF and being done with the part throttle stuff.

 

Here is a type of post that I've seen a lot of in the past, that have kept me away from the MAF table.

 

I'm currently running all stock fueling tables right now.  I'm at like, +7 at idle, and +3-4 driving.  I'm REALLY up in the air as to which way to go with tuning.

<{POST_SNAPBACK}>

 

NoGo:

 

One of these unseen side effects, which prompted people to stop using the MAF table, is transmission line pressure on automatic transmissions. If you use the MAF table to indicate less air then there actually is (lean your car out), the engine load calculation is shifted down. A reduction in calculated engine load means a reduction in transmission line pressure. The incorrect reduction of tranny line pressure will cause the transmission to shift lighter under heavy load conditions. This causes the transmission to slip. Many people's transmissions went to an early grave because of this. This is just one example of what can go wrong when adjusting your MAF.

 

This isn't actually true. You can run these trannies with a scaled MAF (hell with no MAF at all) and it doesn't affect line pressure. I know this for a fact -- I logged it.

 

NoGo:

 

The MAF reading is a prime contributor to the engine load calculation. The engine load calculation factors into timing, torque management, tip in, knock reduction, tranny line pressure, just to name a few. You can adjust fueling using the MAF table, but it is often going to bring with it an unseen negative side effects.

 

The problem with this logic is that it is incomplete. To say IFR only affects fueling is incorrect. To say that changing the MAF reading factors into timing is certainly true, as is the KR and tip in. Both KR and tip in are affected POSITIVELY by the scaling you will do the MAF after SD tuning. For timing, you just retune your timing table (which you would still do after adjusting the IFR).

 

These arguments are also over a year old -- from 8/2003 -- before the SD tuning method came to light. VE also factors into engine load. By adjusting one, and then scaling the other to match, any effect on load calculations should be minimal.

[zippy]

tuning using the IFR is a bad way to go. the only time the IFR is correct is at 0+ vacuum readings. changing the IFR shouldn't be done at all to correct part throttle conditions. the maf readings have more effect on shift points than they do line pressure although they do play a part in each other. most of the line pressure decision is made through the tps readings. if you remove the maf though, it will read off the map and tps for these conditions.

[marc_w]

Holy **** that's way over my head.

 

I'm pretty bitter towards the tuning thing right now. Tuning goes from, "change your WOT shift points and raise your speed limiter" to the masters-degree SD tuning, with little to nothing in between.

 

I still feel like I'm peeking through a keyhole into this world of tuning. I can't see the big picture.

 

I want my carb and distributor back.

[marc_w]

I have no side effects noticeable to me at all, by tuning with the IFR table. Mine is non-linear, if it matters at all. (I have no freaking idea). All I did - scale IFR, scale PE by same percent. Check 02's at WOT. Done.

 

What effect does the MAF have on shift points? What happens if I scale the MAF by 1.25? How do you guys figure this out?

[marc_w]

My question about the transient thing - how much of an effect on normal driving does it have? Is a transient problem enough to set KR off on a rampage?

 

I hear the STS people say it takes like, .2 seconds to pressurize the tubing from turbo to intake. It seems to me the much smaller volume we have between cylinders and MAF would take even less time. Would that be different under a vacuum?

 

What if we just moved the MAF to the TB?

 

EDIT:

 

I guess if the HPT guys went through the trouble to write software to fix this transient stuff, then it IS a big deal.

[TurbochargedBerserker]

My question about the transient thing - how much of an effect on normal driving does it have? Is a transient problem enough to set KR off on a rampage?

 

You've heard of tip in knock. Ussually 100% of the problem is transient throttle tuning.

 

I believe the average transient effect times I was seeing was 2-3/10s, but its been a while. That is with a PE delay setting of 1.00 (the 'do it now' setting).

 

I can sympathize with you on the bitterness. If you search for it, you'll find my post from a few months ago that basically said everyone on those other sites don't make any sense / use there knowledge as a 'better than u' stick, and Deezel, Zippy, BigTex, MN C5, and a few others on here were the only ones who really made sense to me.

[deezel]

I tend to agree on the IFR table. I have mine only scaled down a little at this point. I changed my MAF table from the '03 truck version to the '02 truck version after descreening it with positive results. Then I did a little more fine tuning on the MAF table to get a smooth response at the very low end of the operating range (idle and just off idle). The VE table is a good place to smooth out transients and handle changes to the effective engine airflow (true VE changes).

 

WRT trans line pressure, this should be increased for performance applications anyway. I suspect the early tuners had problems because some tried to lean out the mixture with the MAF table but didn't increase the line pressure to compensate. With these trucks, you typically need to richen the mixture with the MAF/IFR tables and lean out the PE. This does not have such a negative effect on the trans via the calculated load. If you program too much line pressure, you can hear the pump screaming in the trans.

[deezel]

Transient knock: for my setup it was almost completely cured with MAF and VE changes. Smoothing out the VE in the 1600-2800 rpm range (based on logs and analysis) helped a lot. Eliminating the PE delay and lowering the PE activation point also helped.

[zippy]

the .2 to pressurize the tube on an sts so far hasn't shown to be true. they are quick to fill when on a roll and already have some rpm and velocity moving. off idle 60' times from an sts truck will show that. unfortunatly for berzerker its turbo lag that makes tuning a turbo truck very difficult for the most part. gm needs to add positive pressure to show up on the map and tuning would be almost a breeze for them.

 

as for the IFR, the problem with tuning the IFR for your part throttle tuning is that the truck is equipped with a FPR. at higher vacuum situations the injector flow rate is much smaller. if you adjust the IFR for part throttle tuning, when you get into low vacuum situations you are going to have to compensate for being richer. if you want to tune with IFR, drive around with the fuel presure regulator disconnected and adjust it, the plug it back in and read your trims.

[marc_w]

I have a few more questions...

 

What's WRT stand for?

 

How do you know how much to increase line pressure? How do you know when it's too much (without breaking)?

 

My tranny whines in the first two gears, and it's 98% stock. I upped all my upshift pressures by "2", and didn't really notice much of anything. I think my tranny is very fragile now. I put ALL of my TM back in, and my shifts firmed up.

 

About the IFR - The way my truck is set up to see the IFR, is as if it has variable-sized injectors based off of vacuum.

 

At high vacuum, the IFR table is showing the injectors as being larger, because the vacuum is helping 'pull' fuel out of the injector. This tells the computer to hold them open for a shorter period (because they're "larger") to compensate.

 

At low vacuum, they're shown to be lower, because there is not as much vacuum to assist the fuel from being pulled out. This tells the computer to hold them open longer (because they're "smaller") to compensate.

 

I've worked with my VE table blindly. I'm currently running one that's been smoothed by about 6 clicks of the "smoothing" button in HPT. ;)

 

I'm not sure whether to do my own SD tuning, or wait for the HPT V1.6 to come out.

 

I've definitely had some tip-in knock, but I'm also getting a lot of false knock now. I'm running the bone-stock HO timing table. I'm seeing 8* of KR at 8* of timing at 4,000rpm with 900 on the 02's. If you want to hear something interesting - I'm scanning 100ft/lbs less power at WOT under these conditions.

 

I'll have to make up my mind about which way to go with SD before looking to desensitize the knock sensors.