Best way to tune a boosted truck?
07-06-2005, 10:12 AM
#22
Originally Posted by DanaliHD
i haven't done so yet, but, it was suggested to me that i should cap off the vacuum reference. bad idea?
i think i'm gonna put a stock tune back in and start all over again.
i think i'm gonna put a stock tune back in and start all over again.
For boost, you want a boost referenced regulator, IMO. I guess I can see this method (capping the ref line) for really really huge cams were the vacuum is 'not good' ?
I didn't like the IFR method because it is just tricking the tune into running in a reasonable manner -- that method just tells the computer that the injectors are a different size than what they really are in order to match the inaccurate VE and relying on the MAF to make up for the problems that generates. But, there are points in the rpm vs. MAP range where the *VE* is ignored (like over 4000 rpm, and at 400, 800, 1200 rpms).
I dug into SD tuning because I was ditching the MAF sooner or later anyway and was tired of chasing it around trying to nail the VE table
These days, SD tuning is super easy. Both EFI Live and HPT do some kind of automation in the process that really makes it as easy as setting up to run open loop (assuming you have wbo2), logging, and right clicking.
Last edited by TurboBerserker; 07-07-2005 at 12:56 PM. Reason: drunk stupor
07-06-2005, 06:21 PM
#25
Originally Posted by DanaliHD
and the debate continues. lol
i'd just pay someone to tune it but can't find anyone locally who would know how.
i'd just pay someone to tune it but can't find anyone locally who would know how.
you have a wideband right? difinately learn to tune it yourself, with a wideband it is easy. i actualy enjoy the tuning part of my truck.
07-07-2005, 12:52 PM
#26
Originally Posted by parish8
i know the maf is not ignored above 4000rpm and i am 99.9% sure it isn't ignored in the lower rpms. if it was ignored above 4000rpm anyone with boost and a stock map would run blindly lean and that is not the case.
Oh and the RPM ranges are dependent on whether you've changed the MAP & RPM trim range or not (then use those values for the RPM thresholds).
That's all well and good if your MAF has a chance in hell of reading accurately. Otherwise, you're right back to trying to trick the truck into running correctly.
Edit: LOL I *must* stop posting it at work with 4 people talking to me. I wrote MAF in my original post instead of VE...
Last edited by TurboBerserker; 07-07-2005 at 06:10 PM.
07-07-2005, 01:18 PM
#27
Originally Posted by parish8
if it was ignored above 4000rpm anyone with boost and a stock map would run blindly lean and that is not the case.
That's only true if you don't create an accurate VE table to base the calculations on-- I ran significant boost (12psi) with an SD tune on the stock map for months with no trouble. That's one of the main reasons for doing an SD tune -- if your MAF fails (or if the PCM *thinks* it fails) you still have a chance in hell of running enough fuel not to blow up.
All the MAF does is give a reading for airmass into the engine. So does the VE table. Having a grossly inaccurate MAF (because its being maxed) and a grossly inaccurate VE table means the PCM has no idea how much air you are flowing and you have to trick it into giving enough fuel by using a really weird PE value (like 9 AFR when you want 12.5 *made up numbers!!*). Bear in mind that the MAF is inaccurate on it's face (even when its not maxed) by either +/- 5% or +/- 10% depending on who you ask.
Actually, anyone on significant boost (i.e. maxing the MAF) and the stock MAF is running blindly lean and relying on PE (and an exagerated PE to boot -- which is exactly why wbo2s are so vital to setting the PE for a MAF) to keep the motor from going boom.
Last edited by TurboBerserker; 07-07-2005 at 05:36 PM.
07-07-2005, 01:42 PM
#28
DanaliHD-
Some info from the EFILive site on the returnless vs. return (and vac ref'd regulator) issue:
So regardless of what you decide to do on the SD vs. MAF thing (and as long as your boost is going to be low I'd keep the MAF), I'd go back to a linear table. If you don't want to do SD, I would personally adjust the LTFTs using the MAF table and keeping the IFRs at their actual values rather than adjusting the IFRs since the airflow is what changed and since LTFTs measure how out of whack the VE or the MAF is, and so the PCM knows the size of the injectors and can perform its calcs with accurate info, but either one will work with enough blood sweat and tears.
Some info from the EFILive site on the returnless vs. return (and vac ref'd regulator) issue:
The IFR table tells the PCM how much fuel mass the injector flows as a function of vacuum (i.e. BARO - MAP).
Injector flow rate depends on the pressure difference accross the injector: on one side of the injector there is manifold pressure (MAP), and
on the other side is [constant] fuel pressure plus atmospheric pressure (since fuel pressure is measured relative to atmospheric pressure);
i.e. diff = FP + BARO - MAP, where FP = constant
At WOT, injector flow rate is less (MAP is high), and to spray a specific mass of fuel, the PCM needs to keep the injectors open longer;
At idle, injector flow rate is more (MAP is low), and to spray a specific mass of fuel, the PCM needs to keep the injectors open shorter;
i.e. time(s) = mass(g) / flow_rate(g/s)
Since the pressure regulator is not MAP referenced (in our case, "returnless system"), the PCM uses the IFR table to compensate
for the variation in injector flow rate caused by the variation of MAP;
But, if the pressure regulator were MAP referenced, the regulator would increase fuel pressure as MAP increased, causing the pressure
difference across an injector to always be constant regardless of MAP variation, and in this case the IFR table would be flat with no slope;
i.e. diff = FP + BARO - MAP, where FP = constant + MAP, so diff = constant + BARO
Injector flow rate depends on the pressure difference accross the injector: on one side of the injector there is manifold pressure (MAP), and
on the other side is [constant] fuel pressure plus atmospheric pressure (since fuel pressure is measured relative to atmospheric pressure);
i.e. diff = FP + BARO - MAP, where FP = constant
At WOT, injector flow rate is less (MAP is high), and to spray a specific mass of fuel, the PCM needs to keep the injectors open longer;
At idle, injector flow rate is more (MAP is low), and to spray a specific mass of fuel, the PCM needs to keep the injectors open shorter;
i.e. time(s) = mass(g) / flow_rate(g/s)
Since the pressure regulator is not MAP referenced (in our case, "returnless system"), the PCM uses the IFR table to compensate
for the variation in injector flow rate caused by the variation of MAP;
But, if the pressure regulator were MAP referenced, the regulator would increase fuel pressure as MAP increased, causing the pressure
difference across an injector to always be constant regardless of MAP variation, and in this case the IFR table would be flat with no slope;
i.e. diff = FP + BARO - MAP, where FP = constant + MAP, so diff = constant + BARO
The IFR table is simply the electronic equivalent of a vacuum line running between the intake manifold and the pressure regulator. Trucks have a vacuum referenced pressure regulator so the IFR table is a straight line.
Because the pressue reg is referenced to manifold vac this is what happens.
Lets say you have a fuel rail pressure of 350kPa.
Manifold pressure is 70kPa, the injector pressure will be 420kPa.
OR
Lets say you have a fuel rail pressure of 350kPa.
Manifold pressure is 50kPa, the injector pressure will be 400kPa.
So therefore the table compensates for less pressure at the injector due to manifold vac.
Note: Return systems do not need this table.
Cheers,
Ross
Lets say you have a fuel rail pressure of 350kPa.
Manifold pressure is 70kPa, the injector pressure will be 420kPa.
OR
Lets say you have a fuel rail pressure of 350kPa.
Manifold pressure is 50kPa, the injector pressure will be 400kPa.
So therefore the table compensates for less pressure at the injector due to manifold vac.
Note: Return systems do not need this table.
Cheers,
Ross
If you connect the vacuum line to the regulator (MAP referencing),
then the regulator will vary fuel pressure as the vacuum changes such
that there'll always be a constant pressure difference across the injectors
(i.e. the injectors will have constant flow rate regardless of MAP value).
[MAP referencing cancels out any MAP influence on the pressure difference across an injector].
In this case, the IFR table must be flat instead of sloped
(you don't want the PCM to adjust the flow rate in this case).
then the regulator will vary fuel pressure as the vacuum changes such
that there'll always be a constant pressure difference across the injectors
(i.e. the injectors will have constant flow rate regardless of MAP value).
[MAP referencing cancels out any MAP influence on the pressure difference across an injector].
In this case, the IFR table must be flat instead of sloped
(you don't want the PCM to adjust the flow rate in this case).
Last edited by TurboBerserker; 07-07-2005 at 06:09 PM.
07-07-2005, 04:48 PM
#29
Eric, i am concered that people who read this thread are going to get confused and be afraid to even try their own tuning. i am confused trying to understand what you are saying most of the time. it seems to me you are making things more dificult than they need to be. some of the parts of what you are saying that i do understand are not correct and that makes me wonder about the rest of what you are saying.
it is my understanding that there is no way to tune with the stock map and SD tuning, i tried not running the maf and no matter what numbers i put in the ve table i could not get enough fuel at wot.
hp tuners and the 2 bar set up is completely new to me and opens up a whole new tuning world that i have no experience with but i know how to tune for a stock map and boost right up till the maf is excessivly maxed out.
adjusting the ifr a little till the ltrims are correct is not a bad thing to do. there are things like injector offset and probably other things that we do not have acurate numbers for so a slight adjusment to the ifr to get the ltrims where you want them is no big deal.
from there you can either mess with the PE vs rpm table or mess with the maf table. either way you will get the fuel you need when you need it. the stock o2's and ltrims will take care of any minor fueling adjustments, thats what they are there for.
it is my understanding that there is no way to tune with the stock map and SD tuning, i tried not running the maf and no matter what numbers i put in the ve table i could not get enough fuel at wot.
hp tuners and the 2 bar set up is completely new to me and opens up a whole new tuning world that i have no experience with but i know how to tune for a stock map and boost right up till the maf is excessivly maxed out.
adjusting the ifr a little till the ltrims are correct is not a bad thing to do. there are things like injector offset and probably other things that we do not have acurate numbers for so a slight adjusment to the ifr to get the ltrims where you want them is no big deal.
from there you can either mess with the PE vs rpm table or mess with the maf table. either way you will get the fuel you need when you need it. the stock o2's and ltrims will take care of any minor fueling adjustments, thats what they are there for.
07-07-2005, 05:34 PM
#30
Originally Posted by parish8
Eric, i am concered that people who read this thread are going to get confused and be afraid to even try their own tuning. i am confused trying to understand what you are saying most of the time. it seems to me you are making things more dificult than they need to be. some of the parts of what you are saying that i do understand are not correct and that makes me wonder about the rest of what you are saying.
which I corrected). If I'm confused on something call me on it. You should know by now that if you're right and show me why, I'm the first to admit I was wrong about it.
Since I did 100% of my own tuning, and since our initial HP numbers are pretty close to same (I lump my better heads against your better turbo and think the rest is pretty equivalent), I think my method stands on its own just as yours does.
There is no doubt that doing an SD tune requires more understanding of the PCM and what it's doing, and has a steeper learning curve. There is also no doubt that plenty of folks have gotten along without it for a long time just by doing whatever someone on the forums told them to do.
Dan's initial question though is the prefect example of why one-size-fits-all-apply-this-spread-sheet tuning doesn't always work.
it is my understanding that there is no way to tune with the stock map and SD tuning, i tried not running the maf and no matter what numbers i put in the ve table i could not get enough fuel at wot.
All you need to do is make the 105kpa cells rich enough (and have the fuel pump and injectors to make it work - but thats true of MAF or MAFless) for your max boost and fine tune with the PE. Those are the cells you'll be in all the time you're under boost, so you have to run richer for lower boost than you absolutely need, but there's aboslutely no reason I know of why you can't do it. I'm not running a MAF now (although I recently added a 2 bar MAP) and haven't for about 10 months. Most of my tuning for the turbo has been SD and a 1 bar map.
hp tuners and the 2 bar set up is completely new to me and opens up a whole new tuning world that i have no experience with but i know how to tune for a stock map and boost right up till the maf is excessivly maxed out.
adjusting the ifr a little till the ltrims are correct is not a bad thing to do. there are things like injector offset and probably other things that we do not have acurate numbers for so a slight adjusment to the ifr to get the ltrims where you want them is no big deal.
adjusting the ifr a little till the ltrims are correct is not a bad thing to do. there are things like injector offset and probably other things that we do not have acurate numbers for so a slight adjusment to the ifr to get the ltrims where you want them is no big deal.
What I think *is* bad is using any method you don't understand. Whatever method you want to use, you should know what its doing and why it does it, IMO.
from there you can either mess with the PE vs rpm table or mess with the maf table. either way you will get the fuel you need when you need it. the stock o2's and ltrims will take care of any minor fueling adjustments, thats what they are there for.
As I said above - ltrims are a measure of inaccuracy in the airmass calc. You can either add more/less fuel and make that match the airmass calc or correct the inputs to the airmass calc (i.e. add more/less measured air reported). I don't see how that's confusing.
(Oh btw, I switched to EFI Live for the 2bar
)
Last edited by TurboBerserker; 07-07-2005 at 06:20 PM.
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