Hey guys. I still have the FMU on my car that came with the supercharger. I backed the pin out to 2 1/2 turns after I changed the fuel pump and such. As I understand it, my tune should not have been affected by the new fuel pump so in theory it should run as it did before I started having issues. I've noticed after my repairs that the car is not as fast or eager to leap to speed as it was before and I don't recall what the FMU was set at before. Since I am running a FAST ECM that the FMU should be fully closed? I don't see black smoke barfing out the back when I'm nailing it, though there are no missfires or tell tale signs that I am lean either. Even though it shouldn't have been affected, the fuel pressure is a great deal higher now (hovering at 50 psi) after the switch to the hi=flow pump(I'm still running the booster pump as well). Thoughts?
-Dave

 

sorry my reply is not helping you out your tuning/fueling problem. But if you already have FAST. Why the hell you need to use the FMU. Make no sense to me. If it were me, I would take the FMU and throw it in the trash can.

Bruce

 

The shop just never took it out and said it was fine in there. If I pull it will I need to retune my FAST? from what I have been told, the FMU can be used for fine tuning with the presence of an aftermarket ECM. I guess I should hook up the computer and see what the hell is going on?
-Dave

 

Dave,
Bruce is right in that the FMU should be disabled if you are running an aftermarket ECM. The FMU should not be used to fine tune (it is more of a coarse tune if you do not have the aftermarket ECM). Additionally, with the FAST system, you should have ditched the ATI supplied booster pump (again this is a coarse tune for those who do not have an aftermarket ECM). But when eliminating the booster pump, it must be removed from the system, as it is a severe "bottleneck" in the line when it is not running.

First, the base FP setting should be somewhere in the low 40s at idle with the vacuum line disconnected and plugged. It sounds like you are running high FP at idle and are very fat at idle and part throttle.

As you are running FAST, check what the wbO2 is reading. I would expect that you will have to do some tuning as you have changed the fuel pump and now your FP has jumped. You can simply block off the vacuum line feed to the FMU and it will be similar to removing it from the car (remember it reacts to PSI to start "pinching" the return closed).

I sure would be using the tools you have available (i.e all of the tuning characteristics of FAST, as well as the wbO2). If you need help with tuning, feel free to drop me your latest program (.gst file) and several data logs and I will take a look at them. I have been around FAST and DFI for many years and am now working to learn all of the intricacies of BS3.

Aaron

 

Isn't the inline pump always running if the in-tank pump is on? And by that note, shouldn't my fuel pressure be at stock settings since I have the stock FPR on the rail?
I will try pinching off the vaccum line to the FMU and see if it helps. My car was tuned with a lower flowing fuel pump, will it need a retune with my new 255 lph pump? Thanks AKS, you got me out of my last pickle as well. Will try to hook up the FAST tonight to download those files.
-Dave

 

Dave,
The booster pump is always running when the in tank pump is running (if installed correctly). But, it still represents a restriction in the line. And if it does not serve a purpose (i.e. you have aftermarket tuning: FAST, DFI, BS3), then why have it in the system?

Pinching off the vacuum line will have no impact on idle fuel pressure. The FMU only comes into play when the motor goes above atmospheric (boosted condition). At an idle, the motor is under vacuum conditions. The fuel psi may be adjusted by adjusting the AFPR (I will assume that you have an adjustable fuel psi regulator).

I would feel certain that your idle to part throttle rich condition (due to higher base fuel psi setting) is what is causing your car to not feel as fast. Connect the computer and see hwat is going on with the O2 corrections.

Once you have that info, we will be able to steer you in the proper direction.

Aaron

 

what size injectors are you running, boost pressures? remove inline pump and run a single walbro 255 HO pump too ~500-550 RWHP, remove FMU and install 42-50 lb/hr injectors, or use some higher rated Low Z injectors if your power goals are higher then that. get an AFPR to set your base fuel pressure a little higher and run a shorter pulse width for best atomization at idle/cruise for better fuel economy and better tip in response from part throttle driveability and to be more effective while under positive intake pressures.. the higher fuel pressure can offset the pressure difference on the firing side of the injector at WOT. then take your time and tune in the new fuel curve using a wideband O2 such as the FAST add on, or the LM1, or on a dyno.. once you have your fuel curve linear and your timing tables squared away ie max timing with no knock, if you reach knock back the timing down a hair or try adding a little fuel in that area.. once you get this all finished.. your dialed in through redline, voila.. all done.. that is the reason you went FAST.. if it is not you just wasted an awful lot of money.. sell the FMU and secondary pump and try and recoup some money to purchase the corresponding correct parts for your setup. this is the real way to go.. you can get finite tuning using this method and once your there.. adding more power to the system.. ie smaller pulleys for higher boost etc.. is MUCH simpler should be linear changes once the original base tune is dialed in.

CHris

 

Okay, wow my head is spinning You guys have to remember I did not build much of this car myself. The decision to put all this stuff on my car was "sold" to me by the shop. I didn't really know what the hell I was doing, but trusted them to get me to my power goals. Let me do a little research and learn some of these terms from the archives of our little forum to get a better handle on what I should be doing before I screw the car up. Keep in mind, all of this gear worked in harmony up until about a month ago. That's when I learned my shop was a bunch of either ignorant idiots, or a bunch of scam artists and made the decision to start doing the work myself. Be patient with me, apparently I've got alot of cool gear, but truly it is in the hands of a noob. I'll get back to you when I figure out what you're talking about (I'm new, but I learn VERY fast...)
-Dave

 

on that note, I have absolutely no literature on the FAST system and to be honest it all looks like japanese to me. Anyone know where I can get an owner's manual or some kind of tutor book? Can I download the current tune from the FAST ECM itself since obviously it wasn't tuned on my computer?
I made the choice to stop modding with my checkbook alone, what have I done
-Dave

 

The programming part is probably fine. You complained fuel pressure problem. The easy way to fix this is to dump your FMU and dump your boost pump. Start with this

1) Walbro 255lph high pressure pump. GSS340M model
2) Get a BAP from Kenne Bell
3) 50s or even 72 injector
Since you have FAST, it can control the 72s and up no problem.

If you do all this, will garrantee fix your fuel pressure problem. And be more than enough for your combo before your belt start to slip. The 6 ribs drive is only good to max psi is around 8psi of boost if your are lucky. Unless your already have the 8 rib conversion done. Good luck man.

Bruce

 

Fuel Pressure Regulator is Stock. Does this mean it is failing if the fuel pressure is at 50 psi at idle?

 

Allrighty. Booster pump is out. 255 lph in tank is in. FMU is all the way open (need a tool to take off the lines, so for now it is just disabled).
Hooked up the FAST and downloaded the .gst and now I need all of you collective FAST wizards to help me figure out what the hell I'm looking at. Anyone willing to review my .gst file? Couple of oddities noted so far, especially my very rich a/f reading (around 10 most of the time). If you are interested in giving me a hand with this please give me your email so I can drop the files to you. THanks so much,
-dave

 

Dave,
I replied back to your email. You can drop the .gst file to my email, but I will definitely need the log files to be able to see what the car is doing. The .gst file only provides what your tune is currently, it does nothing to detail what your problems may be.

For logging, go into c-com with the program connected and communicating. Select Logging \ Arm Realtime Logging. When you are somewhere safe, hit the space bar and make your run. I typically try to either get 20 or 30 seconds out of a log at 10 frames / sec with the 14 sensor dash. You will also need a cruise log and a single steady mild acceleration log.

I hope this helps.
Aaron

 

E-mail with logs and .gst sent. Thanks alot aaron!
-Dave

 

Ohhh. I sent you some quick detail on the program. I need more info before I am going to be able to make an assessment.

It may be fairly simple or very complicated. It really depends on what the additional variables provide for insight.

Aaron

 

I think I may have discovered a problem. The MAP (psi) sensor as reported by the FAST computer does not agree at all with my analog boost gauge. In fact, the boost gauge will read up to 5 psi without the MAP reading anything but vacuum. IS this a symptom of a dying MAP sensor?
-Dave

 

Sounds to me like you have your program set wrong....as in your telling the ecu you have a 3bar map when you have a 1 bar map... What BAR MAp sensor do you have>>>ARe you sure thats what you have>>and does the program in the setup data screen reflect whats installed.. Usually it defaults to 1 bar...But I dont know what programs were sent to you...All I know is the resolutoin is out of sync>>>

IS it wide band o2???? If so tuning is EASY...Work on idle functions while warm... set your target idle speed for ~750...let the car warm up...The adjust your throttle blades untill the iac target is at ~20.... once that is done take and open up the ve table...let the car idle...MAke sure its warm... while idling with the ve table open in the windows software and WB02 you will see a green circle in a given cell....Look at your FAST dashboard and read the 02 COrrection figures...You want them to be no more or less that 3%...you can click each cell in the ve table and page up or page down and raise or lower the value...you will see the correction vary accordingly...then you tach up the car so its in the next cell..repeat...this will fill in the lower cells correctly...then take a drive and datalog...when you play the datalog a frame at a time with the VE table open you will see the corrections while its in each cell>>>You can use the same logic to get the corrections down>>>Since it was a datalog the changes will not undo the correction...because your not changing it live...SOOO say at idle the WB02 said it was correcting 15% richer...so you paged down 3 values to get it to 3%...use the same logic in the upper cells...then retast and log...

FWIW Im oversimplifying a lot of it...Im assuming your car is running and someone got most of the cells entered properly... Also another fun fact...If you have a power adder MAKE SURE YOU TURN CORRECTIONS OFF at WOT...you can do that in the correction menu...This is a MUST...The reason is if you leave the correction % high and allow the computer to make MAssive fueling changes at WOT a change in atmosphere could cause the computer to overcorrect and you could go waaayyy lean and kill the motor....Best to log and refine the upper level on a dyno or at the track and not let the puter make many changes...

Hope this helps ssome...any questions just ask..

FWIW I run a WB02 fast system on jy 1987 GTA 406 PT 88 turbocharged car... solid roller the whole nine yards...I spent a lot of time messing with the fast systeem and My car idles like a stocker and runs beyond belief...best of both worlds...could not be happier...never though the setup would be streetable>>>But it is..

 

Hey guys. Well currently the car is at Corvette specialty shop undergoing some testing. I have had a couple of strange intermittent problems that don't seem to jive with the tune. #1 on the list is an injector test since I'm seeming to hit a wall that feels like the rev limiter (though it is set at 6500) at around 5200 rpm. The car just won't pull anymore at that rpm and the boost will not pass 5 lbs. I'll let you all know what I find out when I cruise by the shop tommorow. Thanks to AKS for his continuing patience with my blunders as a noob computer tuner. And thanks for the advice Kenwood. I will look into the suggetions you gave me after I figure out why the car is running so poorly.

P.S. the symptoms seem to be an extremely rough idle with some kind of hesitation to cruise at about 1/4 idle. I've run out of tests that I know how to do, so I handed the car off to be tested so I can try the next thing on the list.
-DAve