Violent Boost Spike on TTC

Standard 6 speed JDM, double decat -thats it.

Just tried the TTC mod yesterday.

Every time i boosted, my boost gauge just blew past 1.5 and continued towards 2 bar!!! Only hit fuel-cut once in the region of 2 bar..???

Is that what is defined as boost spikes? To me it doesnt feel like spikes since it seemed constant as soon as I boosted (3500 rpm+)

Had to let off and go back to sequential where I only hit 1.1 - 1.2 if I really nail it in 4th or 5th and then hit fuel cut.

So my question is, how can it be that I hit 1.5 - 2 bar on TTC??? Is my boost gauge reading incorrect in TTC mode?

And why is the exchaust noticable louder when running TTC? Is it due to a change in the wastegate operation?

Is your wastegate opening at all? you haven't bypassed that by mistake have you?

It's normal for a "let god sort it out" parallel conversion to spike around 3500-4000rpm but "only" to about 1.5bar and then it recovers.

Fuel cut takes place according to boost pressure levels and time. If it reached ludicrous boost quickly then fuel cut will indeed lag behind a bit.

-Ian

*steps into uncharted waters*

Which boost guage are you running? Post up a picture of where it is plumbed in and let the other tech types look into it.

I had this when I first did TTC and fitting a boost controller fixed it. I wouldn't keep driving the car at 1.5 bar though however fast it is

At what RPM did you hit 1.5bar?

I had this when I first did TTC and fitting a boost controller fixed it. I wouldn't keep driving the car at 1.5 bar though however fast it is

Maybe you disturbed some pipes, as a boost controller cant lower boost

Maybe you disturbed some pipes, as a boost controller cant lower boost

I know mate. BUT - you need to tell the car when to expect the boost to come on... otherwise the wastegate stays shut until 4000rpm and you're already at 1.5bar

(thanks to IanC for this info)

I know mate. BUT - you need to tell the car when to expect the boost to come on... otherwise the wastegate stays shut until 4000rpm and you're already at 1.5bar

 

(thanks to IanC for this info)

Ahhhhhh interesting

If done correctly, and you have a restrictor ring fitted you shouldent see 1.5 bar, sounds like you have a pipe connected wrong.

If done correctly, and you have a restrictor ring fitted you shouldent see 1.5 bar, sounds like you have a pipe connected wrong.

Mine was done properly, with a restrictor ring in and still spiked badly. I wanted the mod to be permanent so I used the wire method.

I guess it varies car by car then?

I did actually see 1.5 bar on mine, but i was swapping various vacume/boost pipes around, and can't actually remember just which one it was, sorry!

as I understand it you'd still see the boost spike restrictor ring or otherwise - Ian can you verify?

Is your wastegate opening at all? you haven't bypassed that by mistake have you?

It was the 5 minute TTC mod I did (http://mkiv.supras.org.nz/articles/andy.htm)

It's normal for a "let god sort it out" parallel conversion to spike around 3500-4000rpm but "only" to about 1.5bar and then it recovers.

 

Fuel cut takes place according to boost pressure levels and time. If it reached ludicrous boost quickly then fuel cut will indeed lag behind a bit.

It did go really really fast.. Actually it went as I would guess it would do without a wastegate, but I dont even know how to disable that, and after going back to 'normal operation' everything is fine

Which boost guage are you running? Post up a picture of where it is plumbed in and let the other tech types look into it.

I don't thinkt its to boost gauge. I have attached a pic. It's generally used for professional rally with hard lines attached as standard.

I don't know if the possition on where the gauge is attached to the vacuum system can have any effect though.

But the fact remains that it works great in normale sequential operation. Fuel cut happening at 1.1 - 1.2 bar

At what RPM did you hit 1.5bar?

4000 - 4500. And it contiued towards 2 bar in 3/4th gear

If done correctly, and you have a restrictor ring fitted you shouldent see 1.5 bar, sounds like you have a pipe connected wrong.

No restrictor ring. I'm adding the first cat again soon though. BUT without any kind of restriction (ring or cat or stock exchaust) i'm only hitting 1.1 - 1.2 bar (fuel cut) at high 3rd/4th gear depening on outside temperature.

In TTC it just flew to 1.5 in second and past in 3rd..

Sounds to me like you should just stick to sequential operation then

-Ian

And get a restrictor ring fiited!

as I understand it you'd still see the boost spike restrictor ring or otherwise - Ian can you verify?

Well the stock wastegate doesn't open until 4000rpm so in higher gears you'll get both turbos online well before 4000rpm with no wastegate control. Disaster.

I'm still no fan of the 5 minute mod. You need a boost controller plumbed in correctly to handle the sub-4000rpm boost and the spike, and something to handle the fuelling. Oh if it helps, when mapping Smarty's parallel twin setup we got noticeable detonation below 4000rpm when both turbos were on song around/above 1bar, because there just wasn't enough fuel going in on the stock map. And that's at normal boost levels, imagine 1.5bar+...

-Ian

All this is also why i decided to go back after 5 minutes of driving with that mod.