So, I have had a hell of a time trying to fix a boost creep problem on my BNR Stage 4 hybrid.

I sent Bryan an exact write up of all the details of my car set-up so he could spec out the hybrid (~1 page typed) and told him I wanted-
1) ~300rwhp
2) absolutely no boost creep even on the coldest night

I killed the first turbo he sent me due to oil starvation (forgot to punch the center hole on my turbo oil supply gasket). Too many late late nights working on it It was '89+ Stage 4 w/ all options and a "O" trim wheel.

Oh well, it allowed me to break in the engine for several thousand miles w/ out a turbo on it...

Bryan rebuilt me another one and again it was a hybrid built off an '89+ turbo w/ T04B 60-1 Hi Fi compressor, T4 "O" trim exhaust wheel (clipped 15 deg this time) in a bored exhaust housing, and all the usual BNR options.

I portmatched and polished the exhaust manifold and turbo runners and polished and knife edged the compressor outlet.

The 1st time I boosted it boost crept past 20psi by 3,500rpm at which point I let off.

Bryan said the only way to fix the boost creep was to clip the wheel further. I did not want to clip and clip until all my boost response was gone.

So, I then backcut and ported the wastegates as large as the stock flapper allows for, divided the turbo exhaust from wastegates exhaust and externally vented it out the rear of the turbo. I relieved the 2 1/4" hole for the wastegates so that the flapper opened up inside and you could actually see the wastegate passages from outside of the turbo. I bored the turbine exit out larger and cut the rear scrolls aperture out to 10mm all the way around just like the front so there was less high pressure exhaust fighting agains normal exhaust exit.

It boost crept to 17psi on a warm day and had a bad exhaust leak (flappers don't seal well at all). The real boost creep was at 5,000 rpm now. I put on a downpipe and muffler for the wastegates to quiet the exhaust leak from the flapper and it boost crept past 20psi again...

So then I did this



It is a HKS GT 60mm wastegate! The v-band is welded to a stainless 314 scedule 10 90 deg mandrel bend cut down to fit between the transmission and front subframe and that is welded to a stainless backplate that bolts in place of the stock backplate. The rear of the plate is relieved for flow into the pipe bend as well.

I removed the flapper, blocked its hole, and ported the wastegates pretty much as big as the casting will support while still allowing for nice flow departure from the main turbo exhaust runners (angled instead of right angle).



That pic shows the divider, it was sandwhiched between the exhaust housing and backplate and then bored out and polished w/ the rest of the turbo exit for a smooth approach to the downpipe.





Pretty big

This pic shows how I cut the divider between the front and rear scroll's apertures to make the rear 10mm like the front. It also sets the angle of the rear scrolls aperture at a much less forward facing angle.



this shows a stock turbo exhaust side on left and T4 "O" trim clipped 15 deg on right.



and the compressors




Seems to have fixed the boost creep problem! I have a solid 1 bar now I can use that GT wastegate when I get a "real" turbo as well, but this is definitely fast enough for now.

The stock hybrid turbo does have some advantages to large aftermarket- it is cheaper, easier to intall, low and far back in the car (as is the wastegate) for better weight distribution and spools fast.

Now I have to book some dyno time!

 

looks sweet.

 

sense we're on turbo's anybody running 60-1??

 

Nice setup and pics. I'd like to know your final outcome on the dyno...Your Wastegate. Where did you get?

 

ba-BLAM, heh

I saw that turbo in person, Blue TII

although I am worrying if I will get the kind of boost creep you describe. we'll see.

 

Well I hope I don't get the same problems as you once I get the rest of my exhaust done(found out that like 80% of my exhaust is exiting one side of my stock catback, other side would have trouble blowing piece of paper away). I have a TO$B compressor housing/wheel, stage 3 turbine wheel(not sure what the exact specs are but the housing had to be heavily machined by my local turbo shop), 360 degree thrust bearing, S4 wastegate HEAVILY ported and a larger flapper door welded on. I get 7psi with my boost controller off and can get up to about 20 with it all the way up. Pretty good control if you ask me But like I said, I don't know whats going to happen once I get my exhaust done.

 

I don't know how and I don't know why, but it seems I still have boost creep.

With the tip silencer in the muffler boost stays right where I set the wastegate spring tension (.8 kg/cm2 for now), but when I take out the tip silencer it boost creeps to 1.2 kg/cm2 (~17 psi).

I wonder if the very rich AF is tickling the turbo like anti-lag. I will dyno tune it as is since 17psi is not too high, maybe boost will go down w/ less fuel.

But this is ridiculous...

Even untuned (fuel ratio guage pegged at 8:1) it is scary fast. No traction in 1st after 4,000 rpm, no traction in 2nd after 5,000 rpm and it loses it in 3rd a little at 5,000 rpm unless going dead straight. On 225 Yok A520 on 8" rim- gotta get 245 soon. I might have exceeded my 300rwhp goal?

 

Silverrotor- I got the HKS GT 60mm wastegate at overboost store I think, it was under $500.

Ryde of Die- the "Stage 3" is the largest size available for the T3 sized turbos, I believe. Turbonetics has the specs up on their site. I hope it works out, boost carefully at 1st.

 

Wow, 60mm wastegate is overkill!

Some possible problems on why it's creeping on you...
*How long are your vacuum lines to the wastegate?&nbsp Long vacuum lines increase the time for which the wastegate responds - keeps these lines are short as possible.
*Where are you taking the boost source for the wastegate line?&nbsp Run the line as close to the turbo (compressor) as possible.&nbsp Running the line closer to the engine/TB delays the wastegate response.
*Backpressure on the wastegate system?&nbsp Is the wastegate open vented?&nbsp If there is backpressure in the wastegate system, this will delay wastegate response.

Did you test the wastegate out to see if it's working right?&nbsp See if you can induce the proper pressure through the wastegate line to see if the valve is opening correctly.

Running excessively rich acts like anti-lag, but you would hear a lot of popping through the exhaust system???


-Ted

 

I'm not sure it is boost creep now...

I put the wastegate spring tension back down on the lowest setting and it held 1 Kg/cm2 w/ the exhaust tip silencer out, but it only reaches ~.8 Kg/cm2 still w/ the exhaust tip silencer in. I will repeat test when it is cooler out

Maybe just some WG wierdness caused by the very different back pressures of the two configurations? I will have to experiment more...

Wow, 60mm wastegate is overkill!

I was hoping so . It was cheaper than the HKS 50mm or the Tial 46mm I really wanted, plus the V-band set-up made it easy to fabricate the mounting arrangement. And I can use it later.

"Vacuum" line from WG to compressor housing nipple is as short as possible and 6mm silicone.

WG is open vented.

I tested WG w/ compressed air (I wasn't sure I had the nipple in the right bung as the instructions only showed hook up w/ boost controller).

No popping in my exhaust and surprisingly little flammage.

So, I was hoping to dyno tune before 7 stock, but it doesn't look like that is going to happen. Does anyone (Ted?) know of a place good w/ Haltech that can do it on short notice? I don't mind driving a good distance.

Ian

 

Ummm wow, little overboard for a hybrid, I have basically the same unit,( for sale btw). Looks good though..

 

The previous wastegate set-up was the stock WGs backcut/ported to the max, divided from the turbine flow and open air vented out a 2 1/4" hole in the turbo backplate that the flapper opened up into for maximum travel (double stock travel)- boost creep over 20 psi.

My whole set-up is overkill so the WG had to be to keep up.

 

what other modifications do u have that are giving you such huge power

 

Boost was back at 17psi today (WTF???)

I just can't believe it is boost creep...

I am going to try replacing the thickwall 6mm silicone hose from the WG to the compressor housing nipple w/ something more rigid as it could be ballooning along its ~18 inch length and not geting the full psi to the WG diaphragm?

what other modifications do u have that are giving you such huge power

I don't even want to speculate on the HP since that always leads to dissapointment at the dyno. My goal remains 300rwhp

I included my sig to show mods- it is jumbled and hard to read- sorry.

EDIT- a pic is worth a thousand (jumbled) words...

 

hows your pop off valve working? I'd assume saving you from those high *** spikes.
Any updates on the boost creep?

 

Pop off valve worked GREAT! It is possible it saved my engine as the 1st time I spooled I hit ~20psi by 3,500rpm (instantly). I put grease on its piston so I can see if it is staying shut in normal boost- it is shut at 17psi still.

I haven't gotten to the WG line upgrade as I have been working too much, I think I will just do it AN like the race cars.

I just ordered 2 Crane Hi-6 and 2LX92 coils for the 2 leading plugs as I was getting ignition break-up ~7,000rpm in the higher gears (probably from ~9:1 AF ratio :o ). Gotta be able to pull smoothly to 8,000rpm in 5th after all.

Talking to Mike at K2RD about dyno time- soonest is after 7stock . Anyone have experience w/ K2RD crew?

 

Where they gank the dyno from???


-Ted

 

Hi Ted, I know you have experience w/ them

Mike said he could set-up the time at a local San Jose dyno for the tuning. No dyno at the new location...

 

How in hell could you still be getting boost creep! That wastegate is FREAKING HUGE. Now im bummed. I pretty much have the same turbo you do and i have the boost spiking problems as well. I was going to do the same wastgate thing that you did so solve it, but now you say you are still having trouble. There has to be a good reason or simple oversight, but what it is i dont know!

 

Any updates on that boost problem??

 

Yes, the update is EVEN MORE BOOST CREEP!

I found my ~7,000rpm stumble problem was 100% duty cycle. My 720cc and 1600cc injectors are fed by a RRFPR and a Walbro. So I remapped the fuel to hit 100% duty cylce at 8,000rpm.

It revved great to 8,000rpm then, but boost creep was much worse . And I only ran it up to 3rd gear!

I am now having to rebuild the engine because that one 1st-3rd run cracked '89 rear end housing from high rpm detonation. I guess the Walbro was chocking out trying to flow enough fuel at the elevated pressures- I will upgrade to a real fuel system.

I am going to have Brian put a "P" trim exhaust wheel and rebore the post turbine exhaust housing some more. Them mod my downpipe for the larger bore (fairly easy w/ Spec 90 design.)

I will also probably add a 3 1/2" in/out Borla XR-1 muffler as a presilencer. That should cause some high rpm exhaust turbulence and cut flow a bit.

I guess my boost creep is so bad since I have such a free flowing exhaust and also a very low pressure drop IC and intake manifold.

 

Now im bummed. I pretty much have the same turbo you do and i have the boost spiking problems as well. I was going to do the same wastgate thing that you did so solve it, but now you say you are still having trouble. There has to be a good reason or simple oversight, but what it is i dont know!

Hey FATTY_FC3S, I wouln't count this mod out for fixing your boost creep problem- it tremendously helped mine out. As did the previous mod, which was just open air venting the stock WG out the backplate w/ the same divider.

The first incarnation of the BNR Stage 4 I had (stock bored WGs) boost crept to over 20psi by 3,500rpm.

Is yours that bad? What kind of boost creep are you getting?

I'm pretty sure I could have solved my boost creep problem a while ago by bolting on a smaller 3" turbo back exhaust, as when I have the tip silencer in my muffler I can't even make full boost as set by the wastegate.

 

if you plummbed the wastegate back into the exuast it would prolly work aloy better

 

Probably not.

 

if it still creeps after that youve got another problem i think. maybe, i dunno, are you getting the same readings on boost pressure off your haltech as you are off of a normal analog boost gauge? maybe your boost gauge or MAP sensor is messed up and giveing you a bogus reading?

D