overboost on stock turbo and open exhaust

[stl_ty]

i am having overboost on stock turbo and open exhaust. i trying to figure it but i don't know. My first guess is that the internal wastegate is possibly too small for the exhaust to flow and bypass the turbine due to having stright pipe and hollowed out cat. Anyone else having this issue? Any tips to help me out?

 

[QWERTYphoon]

Re: overboost on stock turbo and open exhaust

There is a certain amount of back pressure needed for a stock turbo. When I removed my cat and exhaust and used just a straight pipe I had over boost problems also. For the stock turbo it is best to have a Cat and exhaust.

 

[turbodig]

Re: overboost on stock turbo and open exhaust

It's a common problem.

The factory wastegate logic is programmed for a stock truck, with a cat and a full muffler in place.
Eliminate them and you'd need to alter the programming to make it right again.

You can, however, loosen the wastegate rod a couple of turns. For many, this is enough to clear the problem up.

I'd also recommend finding a local SyTy'er with a laptop or scan tool to check for knock. Any time you alter one of these things from bone stock, the risk of engine destruction from knock goes waaaaay up. Heck, even bone stock they'd knock themselves to death if everything wasn't running just right.

No-exhaust and high boost on street gas without proper monitoring to make sure everything was ok, has resulted in a lot of dead motors. Some guys don't even make it a week.

 

[stl_ty]

Re: overboost on stock turbo and open exhaust

It's a common problem.

The factory wastegate logic is programmed for a stock truck, with a cat and a full muffler in place.
Eliminate them and you'd need to alter the programming to make it right again.

You can, however, loosen the wastegate rod a couple of turns. For many, this is enough to clear the problem up.

I'd also recommend finding a local SyTy'er with a laptop or scan tool to check for knock. Any time you alter one of these things from bone stock, the risk of engine destruction from knock goes waaaaay up. Heck, even bone stock they'd knock themselves to death if everything wasn't running just right.

No-exhaust and high boost on street gas without proper monitoring to make sure everything was ok, has resulted in a lot of dead motors. Some guys don't even make it a week.

But if i loosin' the rod won't that let the wastegate flapper be open a little bit causing slower spool up?

 

[mildtowild]

Re: overboost on stock turbo and open exhaust

i put in a 3" cat and no muffler and had same problem. i adjusted the wg rod and is a lot better. still have to be carefull at full throttle.

 

[Mtn Z]

Re: overboost on stock turbo and open exhaust

I also have to deal with overboost with no muffler. I have the cat in place and did research that showed some people not having any issues with the cat in place with no muffler. Unfortunately I fell into the unlucky group that does have issues. You just have to adjust the wastegate rod and not get too greedy with the throttle. I still haven't adjusted my wastegate rod which means that haven't gone WOT in a long time.

 

[WannabaTY]

Re: overboost on stock turbo and open exhaust

What is the feeling of overboost?? The reason I ask is that I think I may have this issue also... Whenever I am at WOT the boost drops and the truck goes nowhere. I have had a 3" exhaust since I bought the truck 2 years ago but this just started to do this within the last 3 or so months..

 

[1madgumby]

Re: overboost on stock turbo and open exhaust

Wannabe Sounds like the WG. puck is getting stuck open. You need to take it off the turbo & clean the carbon build up off the puck, if that don't work might have A hole in the Vac. canaster rubbler on the turbo. just my .02

 

[ghettosled]

Re: overboost on stock turbo and open exhaust

the only way to solve your problem is either to install a cat or install a larger wastegate. If you loosen the wg rod, it will only slightly delay the boost spike b/c it is leaking as it is trying to build boost. The longer you stay in the throttle the higher the boost will go. A boost controller will not help.

As for what "overboost feels like" you will never know unless you install a good mechanical boost gauge. If it goes past your target boost level, 99% of the time it is detonating and thus pulling timing and as a result the boost will fall off if severe enough. Best to have this problem checked out before it costs you a rebuild. Datamaster would be the best $200 you ever spent, and there are plenty of guys here willing to look at your files.

 

[mildtowild]

Re: overboost on stock turbo and open exhaust

What is the feeling of overboost?? The reason I ask is that I think I may have this issue also... Whenever I am at WOT the boost drops and the truck goes nowhere. I have had a 3" exhaust since I bought the truck 2 years ago but this just started to do this within the last 3 or so months..

also have the same problem. no WOT for me either. , at least we save a bit on gas.

 

[stl_ty]

Re: overboost on stock turbo and open exhaust

the only way to solve your problem is either to install a cat or install a larger wastegate. If you loosen the wg rod, it will only slightly delay the boost spike b/c it is leaking as it is trying to build boost. The longer you stay in the throttle the higher the boost will go. A boost controller will not help.

Is there a way to bore out the stock turbos wastegate easily since the backplate of the turbo is solid?

 

[ghettosled]

Re: overboost on stock turbo and open exhaust

You have to have the wastegate hole bored out and a larger flapper installed. We don't offer that service but there are people out there that do. If I recall the price was around $250.

 

[turbodig]

Re: overboost on stock turbo and open exhaust

But if i loosin' the rod won't that let the wastegate flapper be open a little bit causing slower spool up?

You don't loosen it to the point of opening... you just reduce the spring tension.
It will slow spool slightly... I won't rate this as a fix, it's more of a workaround.

Your alternative is to keep hitting the code 31 overboost MAP limit, where it cuts fuel. Repeatedly hitting the overboost limiter will take out an engine, eventually.

The only way to really fix it is have the chip programmed to deal with the new wastegate environment, or as Mike suggested, put an external on the crossover.

 

[stl_ty]

Re: overboost on stock turbo and open exhaust

You have to have the wastegate hole bored out and a larger flapper installed. We don't offer that service but there are people out there that do. If I recall the price was around $250.

What is the size of the stock wastegate?

 

[JSM]

Re: overboost on stock turbo and open exhaust

Just boring out the stock WG to larger size works slightly. The flow is still going up against 2 90 deg. turns though once it does exit.

Reconfiguring the downpipe to remove that wall helps a ton. I manufactured a downpipe that did this but don't have any for sale currently.

For some it may be easier and more efficitive to just install an aftermarket WG as Mike suggests.

Your going to spend $250 to modify a stock WG that may or may not work, aftermarket WG is similar price.

 

[It's just a six]

Re: overboost on stock turbo and open exhaust

When I had a larger wastgate valve installed in my 8 CM housing it worked fine.

I did notice it opened earlier I think because w/the valve being larger the backpressure had a larger area to push on making it overcome the spring tension of the wastegate actuator..

I installed a heavier tensioned wastegate actuator,that worked.

When I had the larger wastegate flapper valve installed it was $100.00. but this was in the year of 2006.

 

[stl_ty]

Re: overboost on stock turbo and open exhaust

does having three inch full exhaust effect the operation too?

 

[It's just a six]

Re: overboost on stock turbo and open exhaust

does having three inch full exhaust effect the operation too?

Yep,it will cause it to overboost also.