New exhaust and now it goes in to limp

[Covo71]

Hi Guys,
About 2 weeks ago I put on a new exhaust. 3" stainless steel Genie. Was fantastic. Could really feel the difference in torque. But today driving home, went to take off at some lights and it went in to limp. Thought it might be spooling up to quick so slowed it down but it is still doing it. Boost is only at about 14 max. It is not maxing out though, under 10 nearly every time. Need some help. This is my daily drive. Don't care what I need to get if there are any solutions out there. Bit limited for shops here though. I am in Bathurst. any info greatly appreciated.
Cheers

Scott

[mudski]

I can't remember mate if you have the dawes and needle valve in your truck or not. If you do, I would open the needle valve up just a little. Maybe counter clockwise about 1/4 of a turn. If that works, then wind your dawes in a little. I reckon 14psi is a bit low.
Just re read your post. You do.

[mudski]

Is it hitting limp at your max boost or before?

[Covo71]

I have taken the needle off about half a turn. Would having the max up higher make any difference or would it still go into limp when it hits a certain point? I have also cleaned the MAF. I ran out of light so will need to have another go tomorrow.

[mudski]

I have taken the needle off about half a turn. Would having the max up higher make any difference or would it still go into limp when it hits a certain point? I have also cleaned the MAF. I ran out of light so will need to have another go tomorrow.

Limp mode is an overboost safety function. Having said that, my car no longer hits limp mode, but the ECU light comes up on the dash because of over boost. Just reading you OP again, lol, its hitting limp mode at 10 or under PSI? The MAF is getting more induction because of the bigger pipe. Two things to try. Disconnect the battery for half an hour and re try. Try another MAF. Although I don't think another MAF will fix it. But I do see the problem lies there though.
Lemme explain.
Everything was fine pre new pipe. Yes. Now its not and the only thing has changed is the pipe. When you increase the diameter size of your intake and/ or exhaust you are changing the flow rate too of air coming in, and exhaust going out. the MAF measures this flow rate. (Now I'm no expert when it comes to electronics. Hopefully someone can pick up on what my dribble is.) The MAF sends a signal via the ECU etc etc to make your motor runs at the right mixtures bla bla bla. Now that you have increase the air flow rate the MAF is not getting a correct reading and thinks its over boosting and brings on limp mode. So resetting the ECU can sometimes work. If you can get hold of another MAF, try it. If not, I have a good working one here I keep as a spare, I can send to you to try if you want.
I do believe the issue is there, somewhere. By all means, muck around and increase your boost and play around with the needle valve. I could just be that.

[Covo71]

Cheers Mudski, I will try and disconnect the battery overnight. I have a spare MAF here to swap if I need but thanks for e offer. Not sure what to do otherwise except for getting that voltage limiter for the MAF. Getting a bit technical for my liking. Hahaha.

[kevin07]

the only other thing you could from what mudski said is turn in the vnt screw on the turbo. the evin twin would be good to speak to

[mudski]

the only other thing you could from what mudski said is turn in the vnt screw on the turbo. the evin twin would be good to speak to

Thats pretty much the same as using a Needle valve which he already has. With MAF's, they are designed to original or stock spec, stock pipe, no intake mods, chips etc etc. So once you start adding a snorkel, hi flow air filter, pipe etc etc the flow rates go out of whack and the MAF just see's this as an error. Some MAF's have a wider resistance scale and can handle the change, some don't. The Maf I am using now is aftermarket, as the OEM MAF I had kept on spitting the dummy as I have changed everything in my car. Resetting the ECU usually fixes this issue but in some cases it won't. So volt modding the maf or changing the MAF housing and air box lid (which I did)to the hi flow one are the only options.

Good luck.

[threedogs]

is the EGR blocked ?
and what motor do you have a DI or a CRD?

[mudski]

is the EGR blocked ?
and what motor do you have a DI or a CRD?

Scotts EGR is blocked by memory. And he has a Di....

[Hodge]

When my car was on the dyno recently getting the chip tuned, the bloke demonstrated to me that the limp mode is not only brought on by over-boost. It is a number of different variables that when they create a certain scenario, send the car into limp mode. Even minute changes can trigger it though such as the exhaust.
He has had a car brought it, getting limp simply by car having the snorkle installed. MAF detected more air coming in, and even though boost remained the same, it caused limp mode.
He told me even though the CRD's handle boost better when it comes to limp mode boost threshold, it is very sensitive in other areas like fuel pressures etc...
They overcome this by MAF mod via voltage modifier or a diode, or in my case a chip that auto-by-passes this.

[Covo71]

Yeah that's right. EGR blocked and DI. Good memory Mudski. Had the battery unhooked all day at work today. Drove home (only 5kms) got about 500m from home and it went into limp. Starting to really get annoying. What new maf housing and hi-flow air box lid did you get? Rough $?

[Covo71]

Thanks Hodge, voltage modifier? Best place to buy from? Easy install?

[mudski]

Yeah that's right. EGR blocked and DI. Good memory Mudski. Had the battery unhooked all day at work today. Drove home (only 5kms) got about 500m from home and it went into limp. Starting to really get annoying. What new maf housing and hi-flow air box lid did you get? Rough $?

Wasn't cheap mate. From HPD it was. About $500 for the lid and housing I think. But now, I have my boost limit at 25 psi. Goes good now.

[Covo71]

Don't mind spending the money if it works. But I don't understand enough of how it works to know if it will fix what is happening. any idea of what the blokes at HPD are like and how much they know?

[mudski]

Don't bother with them about this. They will just sell you the part... Basically what the larger housing does is allow more air flow. Not so your engine can suck more in and go faster. But more air passing over the maf sensor plate, at the same rpm as pre larger housing, cools the sensor plate, lowering maf voltage more, allowing you to push the boost higher. In a nut shell...

[Covo71]

I still have the factory intercooler. I was looking at replacing. Would that help with the flow and in more air flowing over maf?

[mudski]

Larger intercoolers will have a higher flow rate than OEM. I don't know if my above post explains it really well. Its one of those things thats hard to write.
Have you tried the other MAF? I'd check the intercooler for leaks too. A tell tale sign is oil deposits on the under side of the IC.

[Covo71]

Spent hours and hours adjusting and driving etc etc etc. Going over everything again and again. Thinking it was fixed then it would go in to limp again and me wanting to hurt someone really bad. So day off today and I was checking everything again....... When I was trying to get the heat shield off when putting on new exhaust I was loosening everything. I did not tighten the clamp back up on the pipe from the turbo. I think it might have been leaking a bit. IDIOT! Now tightened up and cannot get it to go into limp now. Fingers crossed all fixed.

[threedogs]

and there you go. I make it a point never to drink and work on cars lol
hopefully thats all it is and you'll be trouble free from now

[mudski]

Spent hours and hours adjusting and driving etc etc etc. Going over everything again and again. Thinking it was fixed then it would go in to limp again and me wanting to hurt someone really bad. So day off today and I was checking everything again....... When I was trying to get the heat shield off when putting on new exhaust I was loosening everything. I did not tighten the clamp back up on the pipe from the turbo. I think it might have been leaking a bit. IDIOT! Now tightened up and cannot get it to go into limp now. Fingers crossed all fixed.

Haha! Atleast you found the issue. We hope. :smile: Sounds right though. Leaking exhaust from where it was would create less restriction, not much but obviously enough, to force limp mode due to higher flow.

[Stropp]

after all the dramas i hope you have got it mate, nothing more annoying than not being able to nut out a problem

[Covo71]

I think I may have just a couple of beers when doing that to. Maybe wait till I have finished next time. It is hammering now.

[mudski]

Hows it going? Still good?

[Covo71]

Best it has ever been. Wasn't exhaust off turbo it was the top pipe. anyway all fixed.
Cheers

[threedogs]

good to hear, good pick up on the fault to LOL

[mudski]

Best it has ever been. Wasn't exhaust off turbo it was the top pipe. anyway all fixed.
Cheers

Ahh, yes from the turbo.
Good stuff...