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Old 08-24-2004, 03:22 AM   #1
waploom
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Default OK, UTEC dyno tuned, runs great, still hesitation though

OK,
Had the sti dynoed. All that's on it is a perrin short ram. First thing, the car is running great. The car feels ridiculously powerful. Running at around 18.5 psi, the car screams on throttle. I am a bit concerned however, because the hesitation problem, while diminished greatly, is still happening at lower rpms when im cruising around town. My question is this: Is this simply a flaw with the UTEC? Or can the hesitation truly be tuned entirely out of the car? If anyone is curious, the car ran 215hp stock and 253 hp after dynotuning.
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Old 08-24-2004, 07:20 AM   #2
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post a log.

Russ
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Old 08-24-2004, 10:56 AM   #3
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don't have one. All I have are graphs my tuner gave me after the dyno tune.
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Old 08-24-2004, 12:40 PM   #4
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get a laptop and then plug it into the utec and then post a log.

the hesitation issues can be addressed with some tweaking, but you have to have the tool (laptop) and the data (logs).

ken
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Old 08-24-2004, 01:31 PM   #5
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Post the map.
I will bet that the tunner did not tune the low load sites and only tuned WOT in the Utec. I see it all the time people pay good $$$$ for a "pro" to tune thier car and end up with a map that is the same across all the load coloums.

TMS
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Old 08-24-2004, 01:51 PM   #6
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That hesitation can be tuned out for about 80% of the time. The other 20 you will have to live with. You are trying to mate up static timing values with active timing values in the factory ECU. Not sure who tuned the car but they should have spent some time on the lower load columns. Post the map and I can help you smooth it out.

C
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Old 08-24-2004, 02:46 PM   #7
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I've seen this alot as well.

The truth is that you can tune out just about every bit of the hesitation with enough effort, but if you try, you'll probably be able to make it happen. Despite the dozens or hundreds of hours spent tuning my car, and doxens more on other people's cars, I can make a hesitation happen. However, it's not the kick-in-the-ass hesitation most people get - I can just barely feel it, and passengers can't feel it at all. In addition, it only happens when I try to make it happen.

Here's the issue: the ECU interpolates timing between load sites. So does the UTEC. However, neither of them have the programming to interpolate the OTHER'S timing. Obviously, only the UTEC could do this, but the programming isn't there.

Post a map and a list of mods, and I'm sure we'll all try to help.

-Sean
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Old 08-24-2004, 04:01 PM   #8
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Quote:
Originally Posted by big_adventure
Obviously, only the UTEC could do this, but the programming isn't there.
future product software update?

(wink wink, nudge nudge)

txs, are you listening??

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Old 08-24-2004, 10:43 PM   #9
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hmm, not to sound stupid, but how do I go about gettin the map log via laptop? Likewise, if I did and got suggestions, how could I input them in to the car (what software) under another map setting (don't want to touch my tuner's maps.) Thanx
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Old 08-24-2004, 10:47 PM   #10
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just had my 04 sti utec tuned by godspeed.
he dyno & street tuned and eliminated as much hesitation as he could.
it's barely noticeable. mostly around 3500 rpm's. feels like a weak hiccup.
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Old 08-25-2004, 01:05 AM   #11
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On a basic TXS stage 2 setup, I have my 10-20 load zones tuned to about 14.0:1 up until 4000 rpms (30 load zone is a bit richer), with ECU-matched timing, and FWIW, I still get a light hesitation from time to time. Undoubtedly, there are people far wiser and far more experienced in UTEC tuning than I who also have the same issue.

AZScoobie himself states that the hesitation can only be tuned out about 80% of time. Most of us on this board are perfectionists when it comes to our cars, and to me, 80% of the time is insufficient. I demand 100%, so to me, the hesitation is a shortcoming that needs to be addressed.

Sure, leaning out the lower low zones and matching timing with the ECU is a work-around, but is it the ideal way to tune the car? I don't know enough to answer that question, but what I do know is that when I lean out the 30 load zone too much, I start to get mild knock, and I have to dumb down timing in that area, making the car somewhat slower. Better than hesitation, though.

Last edited by peterex; 08-25-2004 at 01:13 AM.
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Old 08-25-2004, 01:15 AM   #12
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On another note, does anyone know if this hesitation we are experiencing is measurably bad for the car? Do the EGTs shoot up when the car has a lean-induced hiccup? I know that my gearbox probably isn't happy when I go hard part throttle in 1st gear, only to have the engine hiccup for a second before full power returns. So I don't do it any more. I'm either completely under the TPS threshhold in 1st, or flooring it. It's the only way to "resolve" the issue.
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Old 08-25-2004, 01:27 AM   #13
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Another person in another thread, said he eliminated the hesitation issue by letting the ecu running the timing all the way up to 5500 rpm. Maybe it's easier to tune around the ecu timing to avoid the hesitation? Is this an acceptable solution? I'm a little concerned about the hesitation, what is the official word from turboxs? I know all solutions have their pros and cons, but I almost rather have any other solution (and spend more money) than to have have hesitation that can't be tuned out. I currently have the STI Utec on order, but may cancel if this is really an issue.
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Old 08-25-2004, 09:00 AM   #14
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AZscoobie came to Austin and tuned my car 2004 STI with UTEC. I had bad hesitation. Now, I have no hesitation at all. I am very pleased. My advice is to sign up for AZscoobie if he comes to your hometown or just post your logs and he can help you.


CP
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Old 08-25-2004, 09:39 AM   #15
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Quote:
Originally Posted by peterex
Sure, leaning out the lower low zones and matching timing with the ECU is a work-around, but is it the ideal way to tune the car? I don't know enough to answer that question, but what I do know is that when I lean out the 30 load zone too much, I start to get mild knock, and I have to dumb down timing in that area, making the car somewhat slower. Better than hesitation, though.
i have an 03, and like your 02 it does NOT have the slow closed->open loop ECU fueling transition issues that the later models have. as a result, i have enabled open loop fueling, but i have retained my crossover point at 60%. i have no reason to do otherwise, after all. i have an mbc, but i have worked around PTFB issues. i like to save gas and nothing beats the ECU's stoich fueling for that.

this has improved drivability of my car quite a bit, and i didn't have to spend so much time tweaking in the lower load columns--i just set them to be around stoich and ramped up fueling to 10.8 in the 90-100 ranges.

i should point out that every once in a while i do get a little hiccup, but it's pretty minor, and it only occurs around the tps crossover point.

jm2c
ken
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Old 08-25-2004, 12:11 PM   #16
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It's not always, or even usually, a lean-induced problem. Originally, with 4.1 and earlier UTEC versions, rich-outs caused a lot of the hesitation, but TXS modified the basemap and code for 4.2 and this alleviated most of this. Here's what happens when you hesitate:

You are cruising. The ECU is in charge of timing and fuel, and perhaps boost.

You start to step into it, lets say to pass. The values in the ECU start changing, but it's a smooth change. You can change 10 degrees of timing in half a second, but it's smooth, because the ECU interpolates the values the entire way through. In other words, if you are at 0.5psig and 3600rpm, the ecu takes the timing values from (for example), 0psi at 3500 and 0psi at 3750 and 2psi at 3500 and 2psi at 3750, and plots the timing at that exact instans to the middle of those 4 values, weighted for where it is. In this case, it will be a little closer to the values for 3500 and 0psi than 3750 and 2psi, because .5psi and 3600 are a little shy of the mid points. This happens every time the ECU sends a spark signal to a coilpack. Thus, even if, for example, the two values at 3500 were 13 deg and the two values at 3750 were 19 degrees, the feeling passing between them would be mostly smooth, because the individual changes would be minutely tiny thanks to interpolation. This also happens on fuel and boost control.

The UTEC takes over timing, fuel and boost suddenly. Now, the car was cruising along at 36.3degrees of timing and the UTEC has 34.5 at that point. Even though this is a fairly small change, it's instantaneous. The UTEC does not interpolate from the ECU, AND it does not interpolate when it hands control back to the ECU. 2 degrees over 2/10th of a second with 24 intermediate points (3600rpm * 2 spark signals per rev = 7200 sparks per minute or 120 per second) can be smooth, but 2 degrees over 1 intermediate point feels like a kick in the teeth.

This is also why the hesitation mostly happens at low to mid throttle, like easy-does-it accelleration or slow, controlled passing situations. All it takes is hitting the cross-over point, especially just barely. Especially because the hesitation will often cause your foot to jerk, leading you to bounce back and forth across the cross-point, causing a LOT of hesitation.

Your goals should be this:

1. Find the optimum crossover point for your driving style. I've run everywhere between 21% and 37%. This will just take practice.

2. Take logs and logs and logs from your UTEC. Remember how you made the hesitation happen, and try it and get it on "paper" several times. If possible, get it in different conditions - when the car is cool (not cold), after a long highway cruise, after sitting in traffic - try to get a number of situations.

3. Edit timing and, if necessay, fuel maps to make sure that massive changes are not occuring at the crossover point.

-Sean
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Old 08-25-2004, 01:13 PM   #17
mick_the_ginge
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Mick's Method

This method seems to work pretty well for the stage 2 STi's. Use ECU timing in some of the lower load columns. You still have to tune the transistion from ECU to UTEC but it's way easier to do it at the high load columns as the ECU's timing is less erratic at the higher loads. The problem of tuning the 10% column to do this is that the ecu uses massively different timing depending on the situation. It makes it hard to find the close to perfect value.

Tuning out the transition in the higher load columsn IMO is just easier.

I have left a set of values in the transitions points that are usually pretty close. Obviously all the other timing is car dependant.

A fix from TXS would be nice. They just need to ramp up or down the timing during the transitions.

One other point to metion. Have a look at the injector duty cycle at the transition points as well. A large leap in injector duty cycle usually means a fueling based hesitation. Large being over 20%

Do not use this method if you have a BigMaf. With a BigMAF you have to use UTEC timing. No longer will the ECU timing work, even in the lower load zone.

Code:
Timing Map
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Old 08-26-2004, 08:39 AM   #18
Abe Froman
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So you stick with a low cross-over point(25%?) with this method but let the ECU control timing in the lower zones? I'm assuming you keep the fuel in UTEC control?

Without info you're flying blind so you definitely need logs. I did logs of my ride back and forth to work, hours worth of logs, over several days. The cross-over point is easy to find and you can just compare the timing values, you can see the stock timing varies quite a bit so it's very difficult to get the static values close to it. BUT the really helpful thing I got fromt eh logs is that I noticed that I rarely go above 30% TPS unless I'm really getting into it. I'm either below 30% or above ~70% so I raised my cross-over to 30%, haven't noticed the hesitation nearly as much, I might just call it a day.
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