I have a sleeved B20VTEC with a LoveFab ramhorn, BWS366ETT, 38mm TiAL gate with a 7psi spring, dump to atmosphere, full 3" exhaust with a Magnaflow muffler, and all sorts of boost control issues that seem to have cropped up suddenly.

For some reason, recently the engine won't make regular boost. For a good two years it was fine at 7lbs and would sloooowly creep to 13lbs at redline (8500) on atmospheric pressure, but recently it won't do anything except shoot straight up in boost, almost as if the wastegate is nonfunctional. I've tried pulling the boost controller and running atmospheric, I've tried replacing the gate with another TiAL, I've tried pulling fuel in case it's got a bad burn and is effectively having antilag, nothing seems to work. I can't figure out why one day it would begin behaving so completely differently. It's tuned to 20lbs but it will hit boost cut at 25, and obviously it's blowing the tires off at the track without boost control in the lower gears.

Open to ideas... not sure what else to try!

 

You're at a point where you need a larger wastegate. Trying to use a 38/40mm for something as large as that S366 will always give problems. They get worse as dense cooler air increases as the ambient temperature decreases.

Time to either let the turbo go to 25psi and tune for big top end, like it was designed for, or use a larger gate (46mm+ comes to mind) and try to retune again.

 

Did you miss where he said it was fine for 2 years?

When you say you removed the the boost controller and ran "atmoshperic", can you give more detail?

 

It would SLOWLY creep to 13psi. I don't see that as "fine". Perhaps it's the types of controller used that makes it acceptable, but as one having a 38mm mv-s, I don't see how that's OK

With that in mind, how old was the wax single gate? When was it purchased? I have an idea, but not what you think

 

Ok but there are 2 things going on here. If his normal condition is 7 psi slow creep to 13, and now its going straight to boost cut, the solution is not new WG or boost control. Its figuring out how it went from working consistently to now not working at all. The creep could be irrelevant to the issue at hand.

 

See? you're thinking what I thought you would.

I'm not saying wastegate is BAD.. I'm suggesting, wastegate may be using the older valves that TiAL used prior. (Saying 38mm could mean the older 2-bolt, newer 2 bolt, or the MV-S)
The older 38mm 2 bolts from years back could only work with regular petrol, and would stick with race fuels, unless you went to the larger gates which had their valves that were coated , and could support other fuels

You know I understand HOW to diagnose. I'm looking at MANY different factors, and simply asking questions to get more information to make a variance of deductions. Some factors are more important than others.

Yes... what is it that changed? Even the OP may not realize that if something was changed, it may be so minor to him that he didn't notice it was a significant change.

Just work with me, here.... I know what I'm asking..

 

Last time I seen this issue just "pop up" in a thread the problem ended up being a collapsed flex section in the down pipe. Might wanna check that.

 

^^ I like it. Makes sense, and it seems to be a nice low-tech approach

 

Thanks for the feedback guys... I do have a short flex section in the 3" where the cat would normally be, I'll pull the exhaust and check that. Not sure how more backpressure would result in worse wastegate performance but I'm grasping at straws here. There's no flex section off the wastegate, it dumps to atmosphere down by the oilpan.

It's definitely an *old* TiAL, purchased back in '05 or thereabouts, but I did purchase the upgraded race gas proof valve at the same time and have been running that since I went turbo. I do run pump gas with meth injection but from '08-'10 I was running C16. I'm not thinking it's the wastegate unless two TiALs are bad - like I said I did try swapping it with another gate and the behavior's the same. I did swap springs at the same time, but the spring's springy, so unless it suddenly got stiffer I don't think that's it.

When I say atmospheric, I mean the top port left open - no boost controller besides the regular wastegate spring.

The only other thing I can think of is I upgraded the grounds on the car... I'm really hoping not but at the end of the day it might just be the tune needing to be redone to add ignition back in and pull fuel out with a better burn.

 

the other thread in question had a flex section on the recirculating dump tube, which was completely collapsed so may not be your issue. Never hurts to check, might wanna make sure there is no type of restriction in tour dump pipe

 

Thanks, dump pipe is literally just a pipe, so it can't be that. I can see through it.

Been working on the bike the last few nights, I'll get to the car soon and post back.