Boost Creep Issues? Then please read on .... :) *

[HYBRID]

then the maltese come & break physics lol

1st of all very nice writeup tobs.. i just have a wee thing for u to notice, how exception is not always the rule.. now bear in mind you have colder temps in the uk, but here we have denser air which kinda does the same effect (mildly).. waiting for my greddy, im running a ct9 on my (too big for it setup lol) ie a 60mm decat, which turns into a 70mm exhaust to a 80mm inlet backbox which in turn ends up at 125mm at the tip (apexi N1 rx7 backbox) .. also im not running any air filter (unusual isnt it lol).. i have the stock actuator as i couldnt be arsed to buy an hks one & i have a turbosmart mbc FULLY OPEN & what do i get?! ..... 0.8bar at WOT, which by 5000rpms drops to 0.5bar.. y?! well simple coz the actuator is too damn weak to hold the door propperly open..

well my point is a simple one, the angle that the decats ppl buy on this site (ie how much clearnace & turning angle was used internally) could be in fact causing the door not to open enough, or cause turbulence due to the gas hitting a wall infront of it b4 being expelled into the exhaust system, ask sacha or any exhaust expert & they will tell u that exhaust turbulence can cause alot of backpressure problems

not pissin on ur fire dude u have a very nice writeup, just giving u a perspective from another side of the world

kon

 

[Sheldon]

then the maltese come & break physics lol

LOL!

 

[Toby@ToyTuning.com]

Hey Kon,

Are you saying that some decats actually prevent the wastegate from opening as there too angled, if so this isn't physics it's called buying a shit decat

Anyhow if that is happening to people then let me know and I'll add it in, although who ever is making decats like that really needs to have a re-think as that's madness, some common sense wouldn't go a miss!

The actuator spring being too weak was also mentioned but that doesn't relate to your second comment as that's about the physical design of the decat which is too steep thus pysically stopping the wastegate from fully opening

T

 

[HYBRID]

hey tobs,

iv seen it for a fact, u can tell externally about the angle & the length of the bend.. even if the wg opens fully, if it finds the decat wall to soon it will cause turbullence which in turn will cause alot of back pressure thus u get what u call "boost creep"...

yeah the actuator comment mearly means that ppl with a stock actuator more often than not will have insufficient boost problems not boost creep.. if those ppl have the "creep" issues then they prob have a decat problem...

just my 2c
kon

 

[Toby@ToyTuning.com]

Yeah that's interesting, the path should be as smooth as possible to promote the flow of gases, do you know what decats have been made like this? In effect the turbulance caused will literally cause a bottle neck and the gases won't be able to flow away from the turbo.

Will add this into the description later another possible cause for sure although it's best to buy a good decat first tome round.

Tobs

 

[HYBRID]

well im not mentioning any names lol.. its not ethical but yeah iv seen a good majority of ppl using wrong clearances porting the turbo wont help either .. think about it, its not u or me that designed the ct9.. it was IHI & im pretty sure they knew what size of actuator door & exhaust port to use.. otherwise it would have been a pretty unbalanced setup.. also, putting a decat onto a bog standard exhaust system will cause the same turbulence but further downstream.. ie same problem..

they are very minute things but if u think about it one of the 1st things ppl do is get a decat..

kon

 

[StarbowBoi]

Tobs great post, you forgot to mention boost controller???

 

[StarbowBoi]

Just reading over this post, haven't been to the forum in a long while since old forum times, looks like a wars going on in this post... haha

Im actually experimenting with this same kind of issue with an n/a car, could both of you2, u know who you are, give me some info regarding this in my techincal post please.

Much appreciated

 

[Toby@ToyTuning.com]

No no not a war we are just discussing the different factors :homer:

I just need to add in a paragraph on these poorly designed decats and EBC's.

Best Regards,

Toby

 

[EH@B]

great topic dude

 

[mg.field]

King Toby!!!!

Just want to say great write up Toby!
Gave me some good ideas.
Suffered real bad with boost creep, car would settle at about 5psi, then if you floored it, it went up to over 15!
Probably due to my relocated air filter.
I placed a restriction in the silicone hose between the filter and turbo, and it now runs great! doesnt spike at all, and hasnt really affected the pick up much either!
Time to up the boost!
Doesnt seem like everyone agrees with your write up, but its definetly helped me!!!
Cheers mate!
Good times.
Mike:homer:

 

[Toby@ToyTuning.com]

Hi Mike,

Glad to hear The key issues are there we just need to add in a few details regarding the poorly made decats and EBC's, apart from that it's all factual and relates to anyone like yourself that experiences problems.

Restricting the filter will restrict the airflow which quite simply means the w/gate will have a better chance of exhausting the waste gases. Just for the record our new Toy Tuning Hybrids have a ported w/gate, you can run filters off these and you won't get boost creep as we have already tried but more on this soon.

Anyway well done Mike a little bit of intuition and your back on track

T

 

[Daicotomy]

Nice explanation of boost creep. I'm really only passing through, but I thought I mifght also add to th topic.

Boost creep occurs because the wastegate port isn't big enough to divert exhaust gas around the turbine. Making the downpipe more free flowing tends to encourage the gas to keep in motion through the turbine, rather than doing a left turn into the bypass. Creep is basically a higher than desirable settling pressure above the preset. Marginally drilling out the port usually overcomes the problem.

Boost spike is where the pressure peaks and settles back to the preset. This is because the actuator can't react quickly enough to open the gate. It is a sympton of proportional control and is easily observed with the radiator thermostat on your engine. Proportional control can only see an error between the desired condition (setpoint) and the actual condition, then react to it, the size of the error before something tangible happens depends on the magnitude, speed and rate of change of the regulator (e.g. wastegate) .

 

[Aidan@EP-styling]

great write up toby

im just wondering does a front mount intercooler help stop boost creep?
longer piping with a large intercooler then surely the ct9 will have a slightly tougher struggle to push the air to the engine?

ive just noticed that ive a much more stable boost now since ive fitted the fmic.

 

[richglanza]

great write up toby

im just wondering does a front mount intercooler help stop boost creep?
longer piping with a large intercooler then surely the ct9 will have a slightly tougher struggle to push the air to the engine?

ive just noticed that ive a much more stable boost now since ive fitted the fmic.

is this theory correct??

 

[Timmy]

TBH no. The charge will now be cooler and therefore boost creep could be potentialy worse.
I think downpipe bore size is a good place to start. Are many people with blitz downpipes having issues? They look a smaller bore than most.

 

[Aidan@EP-styling]

is this theory correct??

anymore views on this?

 

[yan]

Ep 91

Nice lecture toby

 

[lyd]

hi .i have an ep91 and when i bouth it 5 years ago the delaer told me that is standard and have the limited slip and a gerbox razo and i saw it and i sad it is standard after same days i went to see the biologe of the starlet on the internet and i find that standard boost is 4 on the low button and 8 on high after same days i maked her a boost gage and it reads on low 6 and on high 13psi many people told me she has an fcd in it and we checked it and it dosent have fcd in it. she is stil wiht the cataletic converter. i maked her an ather boost gage to be shur and it reads the same 13psi. i have a problem to make demages or it is normal to run 13psi

 

[Sheldon]

hey mate i see your from malta eh? tajjeb qed inzidu awn mela

its not normal runing 13psi it could be that you have a factory limited slip. 90% of maltese EP's that are sold as standard once they had some mods then they remove everything and sell it as "standard" so could be you still have an actuator? btw if you could open a thread for yourself its better as i dont think it has nothing to do with boost creep. if you need any help just send me a private message.