Fuel cut and/or wastegate issues

[rtrdpenguin]

I'm having a few issues with my car at the moment and have been trying to figure them out for the past few weeks. I've gotten it to the point where it runs well and is drivable, but there are still some very irritating problems I'm having trouble with and I was hoping if I posted them up here maybe someone would chime in and point out my stupid mistake(s) =)

Mods: K&N intake, 3" DDP from ZW motorsports, 3" high flow cat, 3" RS-R GTII catback exhaust, Walbro fuel pump with 12V mod, J-tube delete, driftmotion spearco replica IC and hardpipes with HKS replica BOV. Everything else is stock, including the CT-26.


The most annoying one is the fact that no matter what, my car keeps boosting to ~12 psi and reaching fuel cut. Is it possible with my mods the airflow is just high enough that boost cut is triggered/the wastegate doesn't open?

It builds boost pretty quickly, as my aftermarket gauge shows, but it also feels like it has less power than before. I used to have a 4.30 diff compared to my 3.73 now though, so I think that's why it feels slower.

I've checked for boost leaks, everything is 100% tight.

I've tried using just stock boost by putting a hose from the compressor outlet to the wastegate, it hits fuel cut.

I've tried using a ball and spring MBC set at the lowest setting and various other points, it hits fuel cut.

I've tried using a HKS EVC II EBC set at the lowest setting and varius other points, it hits fuel cut.

I'm about to go out and pressurize the wastegate by hand and see if it opens. The weird thing is my car used to run perfectly with the exact same setup in my old chassis. Boosted up to 10 psi using the same MBC and held there, never overboosted and had only tiny bits of boost creep. I did put on a brand new accordian hose but that shouldn't be an issue... every hose is tight on there. The car runs very well and I can't find anything wrong, which is why this is so confusing!

I've heard of people having trouble with the stock CT-26 wastegate hitting DDPs, can someone fill me in on that? My DDP is the same one I used before and it never had problems =\ I did change the gasket but that shouldn't do anything either.


Another little issue is that my tach doens't work. It just jumps around near the range where my RPMs are. I think it might be a bad ground point somewhere, I've tapped into the IG+ diag port, straight off the ignitor, and on the ECU with a spare tach and it does this at every point. Has anyone ever experienced this?

 

[JoeSupra]

I have almost the same exact mods as u but a 57 trim and no fuel pump and no bov. Let me tell u I feel yur pain man and boy is it annoying. I got no more boost creep now thanks to a blown gasket either between the head and manifold or manifold and turbo...idk. But I read u have port the wastegate hole. People have done it wit a dremel. But idk the measurements and wat bits to use. Hopefully sum1 will chime in and give us the 411 on this. I plan on doin mine soon since my car is off the streets now.

 

[Poodles]

Replacing a torn accordian hose will make sure all the air is going through the AFM, before you where more than likely sucking air in after the AFM cheating the system.

Also, JoeSupra, if you had a leak between the manifold and the head, or manifold to turbo junction you'd see LESS boost.

 

[rtrdpenguin]

Wow, that sucks. I wish I had known earlier that my mods would bring me to fuel cut... could have saved myself some money and kept a stock exhaust or something =) Poodles, you're probably right about the accordian, the old one had a pretty big crack in it. I did only drive around for about 50 miles total on the old setup. I did a bit of reading on porting the WG and probably will try it sometime this week. I'll keep you posted in case I figure out a solution =) A lot of threads I search for never have a conclusion!

 

[IJ.]

Pen: Everything you've done is made the system flow better, more flow = boost cut at a lower boost pressure as I believe it's based on Mass flow and not outright pressure. (I'm happy to be corrected on this if I'm mistaken)

 

[Poodles]

Yep, you've made the system much more effiecent.

Get some 550's and a lexus AFM as your next upgrade...

 

[rtrdpenguin]

IJ, you're right, fuel cut is based on airflow through the AFM. That's what made me think it would be fine to upgrade basically everything involved in flowing air and leaving the turbo alone =( I didn't expect it to be able to boost such a high psi though. Never heard of it happening until now!

I suppose I'm going to have to get 550s and the lexus AFM =( I've been looking into using a lexus AFM and my stock 440s with an AFPR (after cleaning/flow testing them of course) and using some sort of piggyback to increase fuel flow though.

Has anyone on here actually ported their wastegate with success? I've seen threads on how to do it and one guy even posted pictures of the tools needed but so far I haven't heard of any MKIII owner doing it to their CT-26.

I'm going to go put my exhaust silencer in and see if that helps, that thing's got like a 1" ID hole. I used to run it silenced now that I think about it...

 

[Poodles]

That might help...

Personally, I would get the injectors and lexus. Getting yours flow tested, adding the AFPR, and getting a piggyback would all add up to about the same price of the injectors, and you'd be safer...

 

[rtrdpenguin]

Would I? My logic was that even though the 550s give a large margin of safety in fuel flow, it would still be running on the stock ECU. I know many people use 550s and the lexus AFM and everything is fine but a good tune usually helps too. Do I not need an AFPR if I go with the 550s? That would be a good amount of $$ saved...

 

[GrimJack]

Porting the wastegate hole on the DDP helps with boost spikes. I've done this, it's 5 minutes of work with a die grinder. While you are at it, do the same to the wastegate hole on the turbo, too. That takes a bit longer than 5 minutes, though.

 

[GrimJack]

Would I? My logic was that even though the 550s give a large margin of safety in fuel flow, it would still be running on the stock ECU. I know many people use 550s and the lexus AFM and everything is fine but a good tune usually helps too. Do I not need an AFPR if I go with the 550s? That would be a good amount of $$ saved...

550s with a lexus AFM is essentially a plug in upgrade. You'll run silly rich, but you're better off rich than lean!

It can be done without the AFPR, however, it's wise to go the whole route - Lexus AFM, 550s, AFPR, Walbro fuel pump, J-tube delete. Then when you get your next batch of coin to throw at the coin, spend it on fuel tuning - SAFC / MAFT / MAFT Pro.

 

[JoeSupra]

Replacing a torn accordian hose will make sure all the air is going through the AFM, before you where more than likely sucking air in after the AFM cheating the system.

Also, JoeSupra, if you had a leak between the manifold and the head, or manifold to turbo junction you'd see LESS boost.

I do see less boost. I had my car set to 10 lbs then wen I noticed the leak, I never seen 10 again. Anyone have a good link on how to port yur wastegate? pics would b nice.

 

[rtrdpenguin]

Porting the wastegate hole on the DDP helps with boost spikes. I've done this, it's 5 minutes of work with a die grinder. While you are at it, do the same to the wastegate hole on the turbo, too. That takes a bit longer than 5 minutes, though.

Thanks for the confirmation, I didn't want to go do something and mess everything up =) Porting the DDP hole isn't a bad idea either, I'm probably going to do that while I'm doing the turbo.

As for the fuel upgrades, would it be possible to do AFPR, lexus AFM, and fuel tuning device (Skipping the 550s)? One of my main objectives is to make the car run well, so I really want to have a good fuel curve. I thought 440cc injectors were good for about 400 rwhp, and I don't really intend to go up that high even. If I could tune the car to run well on the 440cc injectors there's really no reason to go up to 550cc right?


JoeSupra, there's thread about fuel cut using an avcr where someone posted pictures of his porting tools and his wastegate hole (but I don't think the pictures of the wastegate are ported). I found it by searching for "fuel cut avcr"

 

[Poodles]

The issue is that with the lexus AFM, the ECU is seeing less air.

You'll be ADDING fuel across the board with a tuning device, which is basicly adjusting the AFM signal. This effects timing and of course where your fuel cut is.

The Lexus AFM and 550 injectors are means to be installed at the same time to trick the ECU into allowing more boost. It in a sense moves all the maps down 25%

Also keep in mind you'll need a wideband O2 to even know what you're doing when tuning. The 550's are FAR cheaper in the long run...

 

[rtrdpenguin]

I see what you mean now... hmm. Now that I think about it, the lexus AFM And 550s are pretty much tricking the ECU. I'm not all that excited about doing that to my car, but if porting the wastegate doesn't help I guess I don't have much of a choice.

Poodles, your mod list looks almost exactly the same as mine, have you had any similar problems?

 

[Poodles]

Nope, but my wastegate is VERY tired...

I've had to shim it, and it used to be perfect, but now it will touch fuel cut in 4th and 5th gear after installing the 3" catback and high flow cat.

Oddly enough it's not the HARD fuel cut I had when the wastegate was shimmed a lot, so it ends up pushing through it and I can get to redline pretty easily.

You might want to check that the wastegate is able to open fully with your DDP, that's the only other thing I think it might be...

 

[rtrdpenguin]

Yeah, that's on the list of things to do when I pull the turbo for porting. Unfortunately, I just got 3 immunization shots and my left arm is quite sore =\ They only told me after the shots that I would be sore for "a few days." Now I know why fuel cut is mentioned so much though.

 

[rtrdpenguin]

AAAAhahahha!!! Ok, I went outside and bicycle pumped the wastgate (had to go to wal-mart at like 11:00 to get one...) and no movement. Hmm.... there's a hissing noise.

Turns out my wastegate vacuum line had a crack in it, but it was right at the nipple facing the turbo where I couldn't see it unless I took it off. Long story short, my EVC II now holds 8 psi like a champ. I still feel low on power compared to before but I suspect that's what happens when you change from a 4.30 to a 3.73. At least I won't be at 5k rpm at 80 mph now =)

Thanks everyone for your help, I'm so glad I don't have to spend more money for a while. Now to figure out the weird bouncing tach problem...

 

[Poodles]

Try a highway run, you'll realize you're not any slower

But the good news is, fuel cut DID IT'S JOB. It's there to protect the engine in case of wastegate failure in exactly your case.

 

[NeatOman]

550s with a lexus AFM is essentially a plug in upgrade. You'll run silly rich, but you're better off rich than lean!

It can be done without the AFPR, however, it's wise to go the whole route - Lexus AFM, 550s, AFPR, Walbro fuel pump, J-tube delete. Then when you get your next batch of coin to throw at the coin, spend it on fuel tuning - SAFC / MAFT / MAFT Pro.

I would personally not go 550's Lex AFM etc... Just mind you that this setup was first configured when there was NO MAFT pro. Just spend the money on a MAFT setup and don't waste you gas on a setup like that, literally... i don't see how you would get good tuning from that vs MAFT pro based setup. I do think you will probably save the difference in gas within a year.