boost creep?

[dylan5084]

I think I may have issues with boost creep, I've hit fuel cut once, but my set up is pretty free flowing... I've not had much chance to drive her since the manifold and turbo etc have been put on due to 5th gear coming thru the box only (drove her between house moves)

I've got a big induction kit high flow exhaust manifold stage 3 fensport hybrid turbo (ct26) uprated actuator 3" down pipe and hks superdragger exhaust

I've no boost controller at the moment and am unsure if this will help?

Spool is really quick compared to old ct26 and was boosting to a bar but then creeping up, suggestions?[/code][/quote]

[shinny]

I hate boost creep! I had massive boost creep (couldn't keep the CT20b below 1.2bar) until I eventually had an external wastegate modded onto my CT20b to get control of my boost again.

Firstly I would check:
* Your vac lines have no leaks
* Your actuator is moving correctly
* You wastegate isn't hitting your downpipe (a known issue with cheaper DPs)

If all that checks out, you have various options:
* Fit an exhaust ring to restrict the exhaust (cheap but annoyingly counter productive and will probably only knock 0.1bar off your peak boost - I have spares in three sizes if you want to try tho)
* Port your wastegate (which risks encouraging cracks in the turbine housing and might not solve the issue)
* Weld up the internal gate and have an external wastegate fitted (expensive, custom work)
* Replace the entire turbo again (and if you get another with an internal wastegate then you may STILL have creep issues)
* Replace the exhaust with a 2.5" system
* Refit a cat

Long story short, if your creep is due to your system being a little too free flowing for the internal wastegate (a common problem on MR2s and GT4s with 3" straight trhough exhausts) then your options are either steps backwards or rather expensive.

[shinny]

BTW, this is what my boost creep looked like as I dragged the car up to the redline:

http://www.youtube.com/watch?v=kN33Ah1n5Ug

Clearly if you're on a rev2 ECU without an FCD, you would have hit fuel cut with those boost levels

[dylan5084]

Fit an exhaust ring to restrict the exhaust (cheap but annoyingly counter produtctive and will probably only knock 0.1bar off your peak boost - I have spares in three sizes if you want to try tho

I like the idea of an external waste gate screamer pipes are sweeeet, might be able to custom one myself - I'm a fabricator. Wouldn't mind trying the restrictor rings for short term solution tho

[shinny]

Urgh - I'm not a fan of screamer pipes, but whatever floats your boat!

PM me if you want me to buy the three rings off me at a pretty knocked down price

[alex687]

Urgh - I'm not a fan of screamer pipes, but whatever floats your boat!

PM me if you want me to buy the three rings off me at a pretty knocked down price

Where abouts do these rings go?

[shinny]

Urgh - I'm not a fan of screamer pipes, but whatever floats your boat!

PM me if you want me to buy the three rings off me at a pretty knocked down price

Where abouts do these rings go?

Bottom of the downpipe generally...

[GreddyMR2]

My exhaust is 3" with one small resonator, but there is a one 2.5" place where downpipe joins exhaust.

I was planning to do all 3" exhaust, but now I suppose I better leave it with a 2,5" "restrictor"?

[shinny]

My exhaust is 3" with one small resonator, but there is a one 2.5" place where downpipe joins exhaust.

It's probably in there for exactly this reason.

[GreddyMR2]

My exhaust is 3" with one small resonator, but there is a one 2.5" place where downpipe joins exhaust.

It's probably in there for exactly this reason.

No, the stock mid pipe was 2.5".
Now I have 3" DP and the whole exhause is 3", but I did not have a 3" flange when I was making exhaust, so I left 2.5" DP - midpipe flange temporary.

You can see it here:

[alex687]

can the added restriction of a 2.5" exhaust really make a significant difference to a 3" exhaust? What sort of difference would you be looking at? are you going to notice a difference in power? and could it really eliminate boost creep?

I have a TT hybrid CT26 turbo. It did have a non standard actuator and I was seeing boost creep to around 1.2 bar. I was hoping it was just a case of the actuator being set high and therefore swapped the actuator to a standard one and put a MBC on. On half throttle it behaves as it should and boost levels off (level depends on how MBC is set obviously) but when really thrashing it I still see it creeping up to around 1.2 bar.

My set up is very free flowing (apexi induction, berk de cat downpipe, japspeed exhaust so 3" all the way). I have been told that lack of back pressue shouldn't contribute to boost creep but have also been told a very free flowing exhaust can lead to boost creep... Can anyone explain this to me in abit more detail. Surely any effects from a change in back pressure will be felt equally by the wastegate and the turbine itself??

[andy585]

think i have the same problem

[Steve-O 2007]

I had this problem when I was a MR2 owner... I tried everything and gave up and stuck a Greddy TD05 on with External Wastegate... No more Boost creep ever after that

Due to all the free flowing mods the Stock internal wastegate doesnt seem to be able to handle the flow. You could always try porting / enlarging the wastegate but I would just weld it shut and stick a external wastegate setup on it!!

[shinny]

I would just weld it shut and stick a external wastegate setup on it!!

Which is not as simple a process as it initially sounds... I shudder to think how much that sentence has / is costing me

[alex687]

would going from 3" to 2.5" somewhere down the line have a significant effect? both on eliminating creep and reducing power...

[andy585]

do all the members here have a 3'' system with downpipe fitted mines is a cheap ebay number i wonder if my flap is fouling on the dp

anyone else have a cheap downpipe fitted ???

[alex687]

do all the members here have a 3'' system with downpipe fitted mines is a cheap ebay number i wonder if my flap is fouling on the dp

anyone else have a cheap downpipe fitted ???

I had a cheap one and thought that might be happening to mine. have since fit a nice new berk dp and hasn't made a difference.

The berk is straight through 3" and so is the japspeed backbox, not sure if it is a standard B pipe and therefore not sure what diameter it is but it looks the same as the dp so woulda thought its 3"

[GreddyMR2]

do all the members here have a 3'' system with downpipe fitted mines is a cheap ebay number i wonder if my flap is fouling on the dp

anyone else have a cheap downpipe fitted ???

I have a cheap one. No problems at all.

However, I had another one cheap, a bigger one and it made a problems with boosting. But not overboosting... As it was too big, the wastegate was opening too much and stuck open therefore creating no boost. The wastegate is supposed to hit the DP not to open too much. I even noticed it in a stock DP, there is a sign of WG hitting it.

[cvega666]

2.5 inch HKS Silent Hi-Power exhaust and a quality DP (berk) almost cured my creep problem on the CT20b (and ct26 is even worse), but to be honest nothing will get rid of it completely apart from a externally wastegated turbo.

[Tedtiler]

I've owned and tuned several starlet turbos. The ct9 and ct26 seem to have similar wastegate problems in terms of creep.

The easiest way on a starlet to stop creep is to slightly restrict the inlet flow. That is if you don't want to go down the line of taking the turbo off to modify it or go external wastegate.

Just my experience.