hitting fuel cut with t-25??

[GstRacer]

has anyone ever hit fuel cut with a stock turbo with no boost control all my freind has is an intake and turbo back 3 inch is this enough to make it fuel cut and why?? what to do about it

 

[crankbender]

has anyone ever hit fuel cut with a stock turbo with no boost control all my freind has is an intake and turbo back 3 inch is this enough to make it fuel cut and why?? what to do about it

Try a search on what causes fuel cut and your answer will come to you

The ECU induces fuel cut when it "senses" too much air flowing through the intake. This can be caused by increased boost or something as simple as an intake leak. Check for the leaks first.

Also allowing the engine to breathe better might allow the engine to actually flow enough to cause fuel cut.

 

[Nabyar]

Yeah, the 3" turbo-back might be making him boost creep and therefore hitting fuel cut.

 

[Polyol]

An intake and 3" turboback could put you over 15psi. Your friend needs a boost gauge and a MBC. I bet he is at 17lbs or more...thus fuel cut...

 

[98spydert]

I tossed on a turbo back when I was on the T-25 and just from that mod, my boost shot up to 19lbs and I was hitting fuel cut. boost controller and boost gauge will do it

 

[Larry L]

Try a search on what causes fuel cut and your answer will come to you

The ECU induces fuel cut when it "senses" too much air flowing through the intake. This can be caused by increased boost or something as simple as an intake leak. Check for the leaks first.

Also allowing the engine to breathe better might allow the engine to actually flow enough to cause fuel cut.

I agree the 3' turbo back, and intake can increase boost by 2 psi or more. Also boost leaks will cause this too...Get a boost gauge, and boos controller so you know where your boost is at...An afc can also help...2G's stock run hella rich so leaning it out to -4 across the board shouldn't hurt, and it will decrease the intake signal from your mas. But be safe and get it to a dyno to check O2's on a wide band.

 

[GstRacer]

thanks a lot everyone he needs to get a MBC then everything will be ok hopefully

 

[jim97gst]

I'm willing to bet it is more likely a leak. I have most of the breathing mods on my T25 equipped 2G; 3" turbo, intake, UICP, 1G BOV. I have no boost controller because it will take me out of ESP in autocross. And I don't really need one right now because it's doing what I want it to do. At the low end when open the throttle wide open, it will spike to about 20 psi, then quickly settle down to between 16 and 17, and then start the fall off in the upper RPMs because the t25 is not capable of maintaining the boost. I don't think it is likely, assuming everything is working ok, to run out of fuel in the low RPM range. I have DSM link and have logged everything, and everything is fine. My turbo has very little shaft play with 70K on it.

Read this towards the bottom in the last part of the engine section:

http://www.wincom.net/trog/autocross/2G_ESP.html

I don't think the part about not porting the O2 housing to get this effect is that accurate, because I have an O2 eliminator downpipe which will flow more than any ported O2 housing. I don't know, maybe I would hold the 20 psi a little longer if I had a stock O2 housing.

 

[98spydert]

Aren't you using DSMlink to disable fuel cut? That's probably why it's not a problem for you.

Edit: BTW, fuel cut isn't "running out of fuel" it's a safe gaurd built into the computer. The ECU sees a certain amount of airflow and turns the injectors off for a second.

Edit again: and no, you wouldn't hole 20psi with a stock O2 housing. Increasing back pressure after the exhaust turbine will do nothing for WOT performance.

 

[jim97gst]

I looked at the dsmlink feature list, and yes, it does eliminate fuel cut. I don't think you can turn it on and off, it's just there. HOWEVER, I had all the same exact mods less dsmlink for over a year, and I never hit fuel cut.

 

[98spydert]

Then your MAF was never seeing enough air for the ECU to disable the fuel injectors. Pretty simple

 

[jim97gst]

My point was that I have similar mods and am running pretty high boost for the T25 and I'm not getting fuel cut, while the original poster was. It didn't sound like he was going to check for leaks like crankbender suggested at the beginning. I would do that before going out and buying a boost controller.

 

[98spydert]

And at that high psi you're probably running less lbs/min than a person running 16 psi. I thought everyone was aware of the T-25s efficiency range.

 

[jim97gst]

Have you done back to back dyno runs with the T25 at different boost levels? This guy has.

http://www.newcelica.org/larryd/index.htm

Look at that! He made more and more power at higher boost levels, all the way to 1.5 bar (~23 psi).

 

[98spydert]

I wouldn't bother with a T-25 but that's just me.


I think the question is have YOU made back to back dyno runs with your T-25 on different boost levels? Or I guess you could simply log lbs/min with you dsmlink. That'd be cheaper.

 

[98spydert]

I don't get it, the last picture shows a comparison for the three turbos at max power and the T-25 is listed at 19psi at 211. None of the other three show 211 as a max anything :/

 

[jim97gst]

I don't know where you're getting 19 psi or 211 hp. The boost is measured in bar and there is no 211. At 0.9 bar he made 203 HP, 216 ft-lbs of torque. At 1.3 bar he made 215 HP and 263 ft-lbs of torque. At 1.5 bar he made 226 HP and 279 ft-lbs of torque.

No, I have not made dyno runs myself, but I have pretty much the same mods as this guy at the time of those runs. I can't change my boost anyway, because if you were reading earlier, it will take me out of the autocross class I compete in.

My car is running over 23 lbs/min on the stock sidemount and feels strong. 2 guys on this board with 400+ hp dsms have ridden in my car and said it felt strong for having a T25.

 

[98spydert]

http://www.newcelica.org/larryd/dyno/dyno-comparison.jpg Did you think I made it up?

 

[jim97gst]

You're looking at the one comparing the T25, T28, and L2R. The one relevant to this conversation is at the top that compares the T25 at 3 different boost levels.

BTW, I am not promoting trying to run the T25 at 23 psi. I know that it will kill the turbo before too long, and the intercooler will heat soak pretty quickly and your power will start to drop off. I already said earlier my T25 is settling down and running at around 16 psi as you said I should. I just get a brief spike to 20-21 psi the gives me good torque coming out of a corner which is perfect for autocross.

I'm not sure what we're arguing about. I'm just trying to understand why the poster is having a problem with their setup which is so similar to mine before i got dsmlink.

You said just a turboback caused you to go to 19 psi and get fuel cut. Was it spiking, holding, or creeping to 19 psi?

 

[Polyol]

I was running well over 16lbs with just an intake and a UICP. Had to use the MBC to turn it down. I added my cat back and my boost held at well over 17lbs after all of this. So yah a turbo back should put you well above 16lbs...and hold it (not to redline though).

 

[98spydert]

You're looking at the one comparing the T25, T28, and L2R. The one relevant to this conversation is at the top that compares the T25 at 3 different boost levels.

BTW, I am not promoting trying to run the T25 at 23 psi. I know that it will kill the turbo before too long, and the intercooler will heat soak pretty quickly and your power will start to drop off. I already said earlier my T25 is settling down and running at around 16 psi as you said I should. I just get a brief spike to 20-21 psi the gives me good torque coming out of a corner which is perfect for autocross.

I'm not sure what we're arguing about. I'm just trying to understand why the poster is having a problem with their setup which is so similar to mine before i got dsmlink.

You said just a turboback caused you to go to 19 psi and get fuel cut. Was it spiking, holding, or creeping to 19 psi?

At the bottom of this page is where the comparrison of turbos are and it's labeled Comparison of Maxed out Turbos. That's why it doesn't make since to me.

I guess I missed the part about only the spike being around 20psi.

As for mine, I had a mbc set at 15psi with no spiking. I put on the turbo back and didn't change anything else and boost shot up to 19psi and held until I got rocked by fuel cut. This was on the T-25 with basic bolt ons and stock fuel besides pump.

 

[jim97gst]

I guess I missed the part about only the spike being around 20psi.

That's cool. I guess I just got kinda lucky with how mine worked out without a boost controller. The funny thing is, when I started modding, my bone stock car with nothing more than a boost gauge was getting up to 15 psi and then doing the normal fall off at high RPM. This seems to be higher than most people, although the factory service manual states the spec is between 11 something and 14.7 psi or something like that. So again, I got a good one. Adding the 3" turboback, UICP, 1G BOV added a spike and a pound or 2 of boost.

Hey, I notice you've got an Evo III 16G on you're FWD. How do you like it? I'm thinking about getting the same.

 

[98spydert]

The evo3 16G is great. It spools just as fast as the T25 did under WOT since I've got a blow thru GM set up now. I have nothing but good things to say about this turbo; very affordible, TONS of power compaired to the t-toosmall, and having the power hold all the way to red line makes it feel like a different car. Two thumbs up

 

[Jahjahpoet]

I havent posted in awhile... anyways, in my expierience (2 months w/ t-25 at 20psi) I definately notice the power when i hit full boost... Of course it dies to 18 at around 4500rpm, than to 15psi to redline after that... I havent felt or seen any turbo damage yet. I spiked to 25-28psi (went past the 20 mark on my boost guage about another 5 marks!!) for about a second one time when I turned the boost controller the wrong way! *I'm a dumbass*.. It really didn't feel any faster than what I have it at now. And I'm sure I would have hit fuel cut if I kept on it for more than a split second...
But anyways... yea, 20psi... good stuff... I know I'm right on the brink of Fuel cut. On cold harrisburg nights here in PA, I spike to 21 psi... and if its a real good night, I hit 22psi and hit fuel cut...
But to back up my statements, I have a G-tech. I have done runs at 17psi and get about 227hp and 211tq. But I did a run last night, and I hit about 236hp and 268tq with 21psi. (good nite) a lousy hp gain, but amazing tq. It really does hit harder at 3000rpm when u hit the full boost compared to what it was at 17 psi.
In the end, I know that I'm starving on fuel and the turbo itself is a spinning oven... But I only keep on the throttle when racing around... normally I will only allow it to hit 15 psi before I let off and/or shift. And when I do hit 20psi, its usually only for a second to blow off a loud gust through the BOV. :0) I love my turbo xs...