Dyno Results And Over Boosting Issue

[Simon-S14]

Got my 3071R on my 25 and tuned up yesterday, it makes insane power! However the first thing we encountered was the fact it overboosts like hell. cant run less then 20 psi. Ive got a split dump which has had a lot of work done to the gate area to make it as large as possible and flow well. and the wastegate on the GCG .71 rear housing (its a copy of the OP6 rear housing) has quite a large flap in it anyway. Not sure where to start looking...

Prob is ive gotta get it running less boost for the drift comp on at calder next weekend, Its making 283 rwkw on 20 psi on stock internals, oh and stock injectors its got a rising rate fuel press reg on it and even at that power there was still head room for more fuel... the AFR's are at 11.5.

suggestions?

Edit: while driving it on the street in 2nd and 3rd I see 1.2 bar on my greddy gauge, which equates to around 17psi.... dyno run was done in 4th gear and it seems to boost up a lot higher at full load in 4th

Edited December 9, 2007 by Simon-R32

[Simon-S14]

just took rear housing off the turbo and started die grinding the port larger, the flap also hits the dump flange in a tiny spot stopping it from opening right up. so going to fix all this and hope for the best

[paulr33]

what spring have u got in the gate?

its leaking like a whore

you dont make target boost 20psi until 4500rpm

[Simon-S14]

i dont think i made it clear in my first post, but the adjustable acuator is backed RIIIIIGHT off so there is NO preload on the gate at all... with the preload it was spiking to above 20psi on the dyno so we had no choice but to back it off... so yes, it feels laggy.

Ive taken housing off and started to fix things up, i want to cure the overboost first then i'll crank the preload back up to regain that midrange.

[Simon-S14]

as you can see theres a slight gain in overall size, there is a prob with the flap disk catching on the hole due to it wobbling around in its wleded rod this was like this before, i cant really get a good pic of it catching but a couple of times oive driven it and it goes hard straight away, and another few times it takes ages to wind up.. so the thing isnt always shutting 100% as it should. I reckon we'll tig the flap in the one spot on the hinge thing to hold it at the right angle so the disk never catches on anything...

Before

After

[Dale FZ1]

Post copied across from linked thread:

http://www.skylinesaustralia.com/forums/Re...20&start=20

Looking at the graph, it seems to me that boost isn't "spiking" as much as taking a leisurely ramp up to 20psi where it's holding steady over a fairly wide band at higher rpm. The initial knee is pretty much the same shape as a stocker, which points to good/easy/quick response.

That it is holding so steady at 20psi (once it gets there) makes me think it's not necessarily "creeping" either - if there was a problem with adequate venting of waste gases then you'd be more likely to see it steadily running higher and higher. It makes me think that the control of turbine speed at that level is actually quite effective.

All of which leads me to ask: what is the actuator rated at; and what (if any) additional system are you using ie. turbotech pneumatic bleed, EBC, etc? Maybe there's some change necessary in that area? Like BHDave said - sort out that mid range area and it'd be hard to knock.

BTW, top result - the peak number is about 15 - 20kW higher than I'd have expected one of these units to achieve. I'd had comments from GCG that your specs should yield somewhere near 280ish, but I wasn't convinced it could. Thanks for sharing the results.

Now all I want to see is how Gary Dawson gets on with his, and for you to sort out that boost control with further feedback of on-road and on-track experiences.

Looking here, I can see sense in checking over that wastegate valve, if it's not correctly located then that could be causing an issue. Adding a bit of extra weld on that disc:shaft union could be worthwhile.

But the thing that is jumping out at me is to ask WHY is the preload backed off so severely? If that valve is not seated correctly (read: very firm), then you are getting too much leakage at lower turbine speeds. To me that seems to be the reason why your mid range is climbing lazily - the wastegate is wasting earlier than desired.

Can you explain why the preload was backed off, and what your boost target actually is? That might put us better in the picture.

cheers

Edited December 9, 2007 by Dale FZ1

[Simon-S14]

Preload was backed off because on the dyno with the EBC off, and doing initial runs, the turbo was boosting very early past the desired target range of 1 bar, we pulled the acuator arm off the flapper and left that wide open and it still boosted up to 17 psi at 6000 rpm, took a while to get there tho.

so yes, the preload is needed, however we couldnt run any due to the fact it was going to boost even more then 20 psi and i did not want that.

[PM-R33]

Very curious to find out how you go with this as my car does the same thing, loves to climb in boost. Im hoping the tuner some how fixes it once it goes in to get tuned in January. Let me know how you go.

[Simon-S14]

the flap wasnt opening up enough either which i think may also cause issues. hopefully with some opening of the gate hole, and the dump flange to give the flap some more room i should see some decent boost control... unless someone else wants to chip in with their suggestions?

[PM-R33]

I changed dump pipes thinking it would solve the problem and it didnt. With my wastegate wired fully open it still hits huge amounts of boost just like yours. I can't explain it at all, gives me the shits. Hopefully with the electronic boost controller and a full tune on the microtech it some how fixes it.....i hope!

[Simon-S14]

nope it wont, due to the fact that you, like me, have a mechanical flow issue and not an acuator or EBC issue

what turbo do you have/

[PM-R33]

HKS GT-RS. Heaps of people run this turbo with no dramas so i dont really get it. I have tried literally everything to solve the problem and i dont get why it makes so much boost. Maybe the turbo is a freak and just loves boost

[Simon-S14]

strange, how much boost are we talking?

is it a genuine hKs GTRS or a garret equiv?

[PM-R33]

Genuine gtrs with the hks actuator. From what i've read they are ment to run around 14-15psi, mine hits around 20ish, somtimes more, its just hard to tell because at about 6000rpm it just skyrockets and i usually back off.

[Simon-S14]

fark! 20 psi is scary i know

what dump is on there currently? I believe the only decent dump for a HKS housing is one of the HKS style dumps?

[PM-R33]

Its a xforce bellmouth dump pipe all in one, previous one was a split Bos importing one. Both did exactly the same, so i dont think it is dump pipe related, or atleast if it is, i dont understand how....

The other weird thing is the way in which boost climbs. Once on boost, it climbs really quickly to 7-8psi at about 3000-3500rpm, then it climbs really slowly to 14psi at about 5500-6000rpm and then from 6000 it just climbs to around 20psi where it stops due to hitingt rev limiter. (I dont go over 6000rpm anymore, i only used to when testing what the hell was going on).

[Simon-S14]

its either one of two things then.

the gate port is too small and cant flow the gas

or

the timing is not right and the exhaust gasses are through the roof causing overboost (think anti lag and how that works)

other then that i got no suggestions lol

[PM-R33]

Yeah well that's why im thinking the microtech will help because at the moment its running a stock ECU. My tuner said its the timing affecting it so lets hope he is right.

In your case however it cant be timing related because im assuming your running aftermarket engine management of some sort, so your case is strange aswell.

[STATUS]

simon the only way we could fix this problem with JT's car was to swap rear housing or go external.... by that time he was over it so we sold the lot off and fitted the T67 (more response same power less boost). i hope you find a solution cause yeah even with the gate wired fully open it made around 18psi...... i cant believe they sell this shit over the counter.... dodgy ass mofo's

[BallSx]

it deffinately has something to do with ur wastegate actuator, i believe try changing ur actuator and see what that does, wen the gate or actuator doesnt open it keeps boosting, i dnt think it would be ur gate but u r better off getting a whole 3" dump pipe no plit, id change the actuator first to see if that works, i didnt read everything written but wen u go to put the rod on the actuator on the gate pin, u have to pull the rod out alittle to fit it, if it fits str8 on without pulling the rod out alittle u got it on wrong. also make sure u have a 1bar actuator on there not a 1.5bar. my 2c

Edited December 9, 2007 by BallSx