breathegood

Specifically, the Diablosport Predator, but I imagine the other handhelds work similarly.

If I want to adjust fuel or spark advance on my Predator, do these changes only apply to open loop, or do they affect the closed loop tables as well?

I know that the tuner has full access to all of the MAF, fuel, timing, etc. tables to build a custom tune, but he also has software to make those adjustments that I don't have.

Before anyone asks "why do you want to adjust your custom dyno tune?", let me explain why I ask. I trust my tunner, and believe that he cut no corners in writting a very good tune for my car......on the dyno.

However, it has been my experience that the dyno is a great starting point, but does not necessarily yield the best performance on the street or at the track (real world driving conditions). It is my intention to do some data logging and adjust what little I can to make my tune a little more optimal for the street, but I'm not going to bother if all I am adjusting is open loop.

I have a truck with F/I and extra fuel delivery that requires a piggyback chip to be hardwired in and a laptop to be able to adjust the tune. Being able to flash the PCM with a handheld is quite a luxury to me, but I'm finding my Predator lacks the freedom I have with my laptop and SplitSecond software. I like to think I have a pretty good grasp of how to adjust fuel and timing tables. I have personally spent a lot of time datalogging and street tunning this truck with what I consider a VERY GOOD street tune, but on the dyno, it doesn't make nearly the numbers that it does when I load a dyno specific tune. The problem that I have on the street with my dyno tune is that the timing is too advanced and I get spark knock when under load. It simply does not run as stong on the street with a dyno tune. What seems to be the ideal tunning situation (for myself and others with similar vehicles) is a fair street tune followed by a dyno tunning session and finished with more fine tunning on the street that is somewhere in between. Typically, those that put their truck on the dyno again are making even more power than the first round on the dyno, especially in the mid range where the engine spends most of its time.

Like I said, I think the dyno is a great tool for tunning, but I strongly believe that it isn't representative of real world driving and a good tune isn't finished just because it's posted a maximum number on the dyno. I feel there are some areas were the tune on my Mustang could use some work, but I'm not going to ask a tuner to put the finishing touches on for the street if I can do it myself.

hammeron

all i know for sure, is that i don't know enough
yet to answer your question. i have my suspicions
but those are not what you need, you need
reliable feedback.

what i can say though, is you are a prime
candidate for custom tuning software. bite
the bullet and buy something like sniper,
HPtuners, SCT etc.

i say this because i think you want to do
more, than a handheld is capable of.

Nuke

I agree with hammeron. Based on your apparent knowledge, you definitely should look into the suggested software. The handhelds won't let you do anywhere near what you want.

breathegood

Thanks for the feedback Hammer and Nuke. I had suspected that a software purchase was likely going to be the ultimate answer for me. The engineer in me just doesn't feel good about the "black box" type of tunning we get from professional tuners. I understand that many professionals don't like to give away their secrets, with good reason, but whether I can fool with the tune or not, I like to be able to at least see the details and the process. Show me the mappy!!!

Hammer, your thread about VCT opened all kinds of worm-can questions about tuning for me. I just didn't want to clutter up your thread any more than I already have.

hammeron

hey breathegood, you really are the
perfect candidate, i can tell by the
questions you ask and what you
know already.


the other thread would be perfect for
tuning questions.....it's pretty much
run it's course and GT Bob gave me
what i was looking for.

you'll read that the learning curve is
steep for the tuning software and it
really is true. i've burned up countless
hours reading and re-reading....after
all that, i still know zilch!

breathegood

Yeah, I knew I'd be looking into tuning software as soon as I started up the Predator the first time and saw that you can't really manipulate the map tables.....but all the software options are $$$ that take a big chunk out of my engine build budget!!! Until I get a little closer to my ultimate HP goals, I suppose I'll just have to trust my tuner.

I did send an inquiry to SplitSecond to see if I can use their R4 software that I already have for my Taco to massage the tune on the Mustang. I think their software only works with their engine management products, but asking sure doesn't hurt, and doesn't cost anything.

And I wouldn't say you still know zilch after reading and re-reading.....I'm sure you've improved your reading skills, LOL!

BruceH

Have you thought about using a tuner who has a loading dyno to simulate motor loading?

hammeron

well maybe....

is it wrong to say the words out loud if i'm
reading by myself?.

breathegood

With the truck, it seems to make little to no difference. A member of my local 4x4 club with nearly identical mods to my own had a tuner tune his truck on a load dyno. He was pretty stoked about his numbers, and convinced he was golden, until he started seeing the same ping problem I and several others have when under load on the highway. A load dyno may be a better solution, but the real world is the only place to get a real world solution. I know I'm comparing a bulky, heavy, big tyred, low geared 4x4 to a relatively light, performance vehicle, but the tuning principals and dyno physics are still the same.

Dynos are a good start, but like many others on this forum have stated, timeslips and street performance don't lie.

Rubrignitz

dynos aren't a start, they're the end. unless you have available a/f setup on your car and a lot of interstate w/o cops.