New to tuning, need help!

[iNukeWhales]

Hey guys, first off I'd just like to say how much I've been helped over the years by this awesome forum. I bought my 1998 Talon Tsi in 2012 and have been working it ever since with limited skills. I purchased the car modified, and have since replaced extensive OEM parts, head gasket, timing belt etc, but have never done any engine tuning.

I'm having an issue when accelerating under a hard load. First gear pulls through 1-6K fine, 2nd gear at around 5500RPM the car will backfire and bog, same if I try in 3rd gear at 4500, 4th gear at 4000, etc. The car has the 16G turbo, a 32mm external wastegate, MBC, and an Aeromotive AFPR (there are more mods but these are the ones I believe the problem lies within- yes I acknowledge I know next to nothing, but I extensively research). I believe I may be hitting fuel cut? The gauge on my AFPR jumps around during idle but I've read it could be a bad gauge, so I'm going to buy a new one before disassembling it again (diaphram was fine). When the car is driving, running, you can smell fuel walking around it, and it takes a short time cranking before it'll turn over (3-4 cranks).

I don't know if the injectors have been upgraded OR the fuel pump- should I start by checking those first?

I will upload a video to youtube of an in-cabin drive, as well as a detailed look at the engine bay. ANY AND ALL HELP IS APPRECIATED! Thanks guys.

 

[Mello]

Except for your comment about the fuel smell, this sounds a lot like an ingition problem. How recent have you check or replaced your spark plugs? What brand are the plugs. Same for the plug wires. how old & brand? I would start with the ignition if these are not new or in good shape. These are fairly easy to replace & inexpensive & would help eliminate possible problem source(s).

 

[doubleclutch]

First, that picture is way to tiny to see anything.

What boost are you running? Do you have a wideband? What does it read?

If you are running stock fuel pump and injectors with a 16g and no tuning you are most likely hitting fuel cut. For a 16g you need around 750cc injectors at least a 190 walhboro and a rewire. Before you buy any of those you will need a tuning system. Ecmlink is what i recommend.

 

[my1st2genGSX]

There is actually a thread that I started yesterday, and we are covering almost the same questions.

http://www.dsmtuners.com/posts/153654314/

its the merged turbo one.

 

[doubleclutch]

There is actually a thread that I started yesterday, and we are covering almost the same questions.

http://www.dsmtuners.com/posts/153654314/

its the merged turbo one.

Not really the same question. You have a low boost pressure problem, the OP is experiencing bogging/lack of power at high RPM

 

[my1st2genGSX]

missed that part of the message... busy day at work...

I will have to agree on the miss fire...i would check ignition/mechanical timing.

Also, try to loom your spark plug wires. That will also cause interfernce issues.

 

[c2ypt1c]

If you are running stock fuel pump and injectors with a 16g and no tuning you are most likely hitting fuel cut.

*public service announcement*
Fuel Cut is not dependent on fuel sufficiency. The ecu simply reads too much airflow and decides to cut injector firing.

Couldn't help myself

OP, I've experienced similar symptoms with old plug wires...might want to give that a shot.

 

[doubleclutch]

*public service announcement*
Fuel Cut is not dependent on fuel sufficiency. The ecu simply reads too much airflow and decides to cut injector firing.

Couldn't help myself

OP, I've experienced similar symptoms with old plug wires...might want to give that a shot.

Wrong.

Fuel cut occurs when the calculated IDC required to create the requested AFR (match the air that is measured) is higher than the ECU would like to see (i believe IDCs of over 125%). This means it is 100% related to fuel supply and injector size. Otherwise you could never flow more air then stock.

 

[iNukeWhales]

Thanks for all the replies guys. Spark plugs were done 2 years ago, I've pulled them while running and measured the distance they spark and they seem to be fine, but I'll probably end up changing them out along with the wires just in case.

Honestly I don't know what my boost is set at, I'm not sure how to dial it up/down seeing as how my MBC isn't connected. I had a wideband but a couple weeks ago someone broke in and ripped out my deck and my gauge pod so I know I've got to get a new one.

Unfortunately you can't run ECMlink on the 98-99 ECU's. You'd had to locate a 95 EPROM and link it up to that. I've got a blackbox ECU that is way better tech than the DSMlink, can do everything and faster but I don't have a ceddy mod or the software to reflash it. I'll try to post another forum for my area and see if there's any DSM'ers out here that do (RARELY see any DSM's out in Alberta).

If I pull the injectors out how can I confirm what cc they are? I'm almost positive the prev. owner told me it had a walbro 255 installed but I'll pull it to confirm.

 

[c2ypt1c]

Fuel cut occurs when the calculated IDC required to create the requested AFR (match the air that is measured) is higher than the ECU would like to see (i believe IDCs of over 125%). This means it is 100% related to fuel supply and injector size. Otherwise you could never flow more air then stock.

Where did you get this information from? The FAQ clearly states:

Despite the rumors of fuel cut being caused by too low of fuel pressure, too small of injectors, high flowing exhaust, high flowing intake, or large turbos fuel cut is not directly caused by any of these.

Fuel cut is actually caused by the ECU seeing more air entering the engine than it was originally programmed to use.

 

[Vegas Smith]

Yeah, I always thought it had to do with the stock air-metering system. Back I the day we would "hack" the mas and remove honeycombs and such to get around fuel cut.

 

[doubleclutch]

Where did you get this information from? The FAQ clearly states:

Explain then how someone can run a giant turbo with a stock MAF. it clearly is using "more air then then ECU was originally programmed to use". It isn't like you hop in DSMlink and tell it to "ignore factory warnings about airflow"

from the FAQ (with misspellings and all) "This likely cooresponds with an injector duty cycle which is unsafe or unattainable."

The MAF sees more air then it can safely or possibly add enough fuel to with the current system in order to keep you from melting stuff due to excessive lean condition and fuel cuts to prevent firing at those lean conditions. Our sensors are dumb sensors, the MAF can read as much air as you can force through it. The only reason it cares is because it knows it cant provide enough fuel to match that air.

Anyways, to the OP. You have no AFR monitoring, you have no boost monitoring, and you have no idea what parts are in your car. Pretty hard for us to help.


Edit because I can read

 

[doubleclutch]

Also from http://www.dsmtuners.com/threads/do-not-hack-maf.259563/ post #11

"But hacking the maf causes more air flow to bypass the volume flow sensor section of the maf. This will cause a lower reading thus fooling the ecu to lean out. Like an SAFC or MAFT. Leaner burn = more hp. My hacked maf causes my fuel trims to run at around 119 across the board on stock 450s and stock fuel pressure."

So you fool the MAF into thinking it is getting less air then it is, cause you car to go leaner because of unmetered air, and you make more power. The only reason you "get rid of fuel cut" is because the MAF doesn't think the engine is getting enough air to be in the "danger zone" (cue Top Gun music)

 

[c2ypt1c]

It is a well known fact that fuel cut (in this context) is based solely on airflow, this is not my opinion nor is it debatable. Instead of spreading false information and acting like an authority on the subject, I suggest you do a simple search on the ecmlink forums for 'fuel cut' and maybe, just maybe, then you will begin to understand how wrong you are.

Edit because I can read

And by the way, reading isn't worth much if you lack comprehension...just saying

 

[Vegas Smith]

Ouch.

 

[Jay 97 GSX]

Well fuel cut feels like hitting a brick wall. did u feel that?

 

[doubleclutch]

It is a well known fact that fuel cut (in this context) is based solely on airflow, this is not my opinion nor is it debatable. Instead of spreading false information and acting like an authority on the subject, I suggest you do a simple search on the ecmlink forums for 'fuel cut' and maybe, just maybe, then you will begin to understand how wrong you are.


And by the way, reading isn't worth much if you lack comprehension...just saying

Since you are so smart, go put stock injectors into you HX40 set-up. Airflow will be the same as what you are running now and i guarantee you will hit fuel cut.

How is that not injector/fuel related?

http://www.dsmtuners.com/threads/fuel-cut-what-i-need-to-to-get-my-car-at-18psi.506713/ Post #7 Solution: Bigger injectors


From your beloved FAQ

"SHOULD I GET RID OF FUEL CUT?
NO NO NO NO NO...Do not use any device to eliminate fuel cut. Fuel cut is there for a reason. If you are hitting fuel cut the ECU believes that you are moving more air than the fuel system can safely deliver. If you are having to eliminate fuel cut with some sort of defender either you have an inadequate fuel system, inadequate tuning tools, or a leak somewhere."

More fuel supply, no fuel cut.

The FAQ disagrees with itself. Either way you look at it, too much air for your fuel supply or too little fuel for your air supply, fuel cut is both air and fuel related. Instead of just parroting the FAQ you should try to understand what some of the concepts are.

 

[Vegas Smith]

It's not really a big deal either way, guys. However, I think C2 is technically correct. This is from an ECU editor website:

"Fuel cut is initiated when the calculated airflow goes over a set value, which is set at the address 559A. By increasing this to the
maximum value possible (FF) fuel cut will be pushed off."

 

[iNukeWhales]

Took the thing apart, has a Walbro 255 and 750cc injectors. Replaced all the fuel lines, filter etc and it was still hitting cut. Turns out it was the AFPR tuned way out of wack. Set it to 43.5psi and my fuel cut is gone.

 

[my1st2genGSX]

Awesome!!

Now I just gotta get mine goin!

 

[19gsx91]

You mean I got to watch that whole P*ssing match for THAT!?


Good stuff.

 

[doubleclutch]

Seems like it was fuel related....

 

[Vegas Smith]

Back in the day when it was a more common problem, people would always claim fuel cut on every problem, so it wouldn't surprise if it weren't actually fuel cut.

 

[c2ypt1c]

Seems like it was fuel related....

Fuel related, yes. Fuel cut related, most certainly not...

The issue here was just plain old bad tuning - his AFR was either too rich or too lean because of fuel pressure, causing it to bog down, sputter, etc...A wideband with a datalog would have easily identified this. For the last time, Fuel Cut had nothing to do with it.