tanjaz

Hi guys I'm relatively new to the forum and have had my bugeye for about 4 weeks now. It's a bugeye wrx with vf35 sti injectors, sti top mount, hks ssqv and remap from race dynamic to 327.5 bhp all done before I bought it. It also has walbro 225 fuel pump.
My query is: when giving it some beans it goes well but when you change gear and reapply the throttle it has a terrible flat spot for a second or two before it creates boost again and carries on pulling. Is this anything someone has come across or is just a really annoying traight? It is fine if not giving large so I can't see it's right.

Any help wouldbe much appreciated

Cheers jared

Infected by sti

iTrader: (6)

There will be a slight delay when changing gears but it should be nothing drastic, on my uk sti same set up as you have listed it would be back on boost if changing at speed in under a second, nothing that jumped out and made me thought something was wrong.

Check for vacuum leaks and check the hks bov as there have been copies floating about that are more trouble than it's worth. Just check it isn't sticking open for some reason.

scoobyJim2

When you say flat spot,would you say it is cutting fuel for a split second from a perhaps boost spike?

tanjaz

Thanks chaps. It's hard to say what it is. It's just absolutely nothing there. Had plenty of turbo cars and never had this before it is definitely something you notice.
Not sure what its boosting at as the crappy gauge that was in it only goes up to 20psi and it goes off that.

Cheers jared

PhilWrx100

20psi is over 1.3bar, so sounds like it's hitting the boost ok. Maybe over boosting?

scoobyJim2

14psi is 1bar (I've got 320bhp from 1.2bar) so if you're getting over 20psi which is about 1.5bar which is a lot of boost,hence why your gauge doesn't show more,I have a blitz boost gauge that I wouldnt call cheap and this only goes to 1.5 bar. there is something wrong,you are over boosting and ecu is fuel cutting when your turbo hits full boost

tanjaz

But it boosts fine all the way to the limit no tailing off it's just when off throttle change gear back on the throttle. As soon as your back on the throttle it's a second or so it's dead then boosts again almost like all the air is out of the turbo and it's got lag again if that makes sense.

Cheers Jared

scoobyJim2

Im pretty sure what you're describing is its fuel cutting. When you floor the accelerator,boost will shoot right up until wastegate controls it and boost settles. For example if a car is set at 1bar,when you floor accelerator boost will hit something like 1.2bar for a second then settle back at 1bar. I think you have a boost leak not allowing wastegate to open in time and ecu is cutting fuel untill boost settles. I doubt any decent mapper would go over 1.3bar on standard wrx internals and not forged (it will melt pistons). By the sound of it your boost is going right off the scale and ecu is cutting fuel untill it controls boost.

bustaMOVEs

iTrader: (31)

Get rid of the dv and map it again, when you change gear its probably just under the actual spool of turbo then starts spooling again.
Are you changing gear too early maybe?
And maybe the map needs fine tuning a bit more to eliminate it.
Have you got rr graph?

tanjaz

Yes got a graph with the car. Changing gear when the shift light kicks in. Will go and have a look round it in a minute see if I can see anything. Might see if I can speak to Duncan who mapped it then.
Thanks Jared

tanjaz

Bit of a development. Had a good look and listen and can't find a boost leak. What I have done is disconnect the vac pipe off the hks ssqv and blocked it off and have it a quick test. It has no flat spot with that disconnected. In fact I'm still buzzing from the drive I can't believe how much difference it makes. I assume you can't run these without some sort of dump valve on them?
Cheers Jared

scoobyJim2

Dv might be sticky then,try sorce another to try! The job of a dump valve is to release unwanted air pressure away from going back towards the turbo and stalling it when you come off the accelerator,not only can this damage turbo if no dumpvalve but it also keeps the turbo spinning keeping you on boost when coming of throttle changing gear! So yes you do need one

tanjaz

Have had a quick search on the net and couple of people have had some of the symptoms I have had which I didn't really think about before. The car pops and bangs on overrun and when changing gear although this has been mapped in apparently and you can smell the fuel out the back every now and again which I put down to it being tuned and having no cats etc. will get hold of another one and see what's what.
Thanks guys

Infected by sti

iTrader: (6)

them hks things are nothing but a bag of shìt imho, they don't even sound decent.

There are a few people running dv less on the vf35 but general consensus is to leave a standard recirc on there, especially if your not 100% sure of how many miles the turbo may have covered as you will be putting it under extra load, and if it's tired ( you may not even realise it ) then it's only gonna end 1 way.

I'm dv less on mine but I'm running a different blower

tanjaz

Sounds really strange after having the dv on it and. Ow having none. Will get a standard recirc valve I think.
Cheers jared

propofol

You could have an overfuelling problem.
I upgraded my fuel pump to a 255 lph without a remap and it did exactly what you're describing. On wide open throttle the engine is in open loop and ignores the O2 sensor. If gets too much fuel in this time the mixture will be too rich so backing off and getting back on again will lead to a rich misfire.
I changed back to the standard fuel pump and all was well again. Don't believe anyone who says changing the fuel pump will not affect fuel delivery - it does! Closed loop will compensate by using the O2 sensor. WOT is a different matter!

scoobyJim2

And therefore ecu is cutting boost...