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Author Topic: Boost Spiking?  (Read 5758 times)

alldsben

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    • 91 XR2 91 Miata 04 S10 89 Mustang
Boost Spiking?
« on: February 23, 2017, 11:04:15 AM »

So i have recently put on a cone filter and a boost controller. i have only done those 2 things and have not put boost over 10 psi. if i quickly go to WOT it will over shoot to 13-14psi then quickly drop down to 10. its not a huge problem for me to just be a little easier on it at first into gear but i was wondering if i could fix this in any way. within the next few days i have an intercooler and BOV to install and was wondering if anything can be done at the same time as that to solve this issue.
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WashiestSnake

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Re: Boost Spiking?
« Reply #1 on: February 23, 2017, 11:43:31 AM »

You could port the wastegate that stops boost spikes to a degree. Its not very easy to do ill put a link on it.
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1991 Mercury Capri 68,xxx Miles--Project(AWD)
1996 Lincoln Continental -- The Boat(Given to my Brother)

SHOwn

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Re: Boost Spiking?
« Reply #2 on: February 23, 2017, 01:01:10 PM »

Stock turbo and exhaust?
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R. Powell
'91 XR2, LM 16" Chrome Drifters, White Gauge Faces, Kuhmo 40's, Big Brake UG, 2.5" Mandrel Bent CATback, BMW318 Heated Seats, `94 console, '99 Dodge Neon Spoiler, '94 XR2 Sideskirts Bumpers and taillights, Fresh Basecoat-Clearcoat Cardinal Red (Jul2014), vj11/vj14 hybrid, manual boost CTL.

alldsben

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    • 91 XR2 91 Miata 04 S10 89 Mustang
Re: Boost Spiking?
« Reply #3 on: February 24, 2017, 10:21:58 AM »

Yes stock turbo and exhaust
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Rocketman

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Re: Boost Spiking?
« Reply #4 on: February 24, 2017, 09:57:59 PM »

What kind of boost controller?

You shouldn't be spiking at all with just a cone filter.
Spiking is usually an issue for those who open up their exhausts, it changes the pressure drop across the wastegate, and it can't keep up.
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1.8L Turbo All Wheel Drive Capri... the "GTXR2"


SHOwn

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Re: Boost Spiking?
« Reply #5 on: February 24, 2017, 11:04:16 PM »

I lack enough experience to comment much, but I saw your response earlier and was wondering if you are having trouble with your boost controller. Did it come with several springs? You might want to try one of the other ones if it did. Also, where are you pulling your boost line that pressurises the controller from? Could there be some gunk interfering with the boost control line? Also, are there any pinch points or kinks in the waste gate actuator line from the boost controller?
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R. Powell
'91 XR2, LM 16" Chrome Drifters, White Gauge Faces, Kuhmo 40's, Big Brake UG, 2.5" Mandrel Bent CATback, BMW318 Heated Seats, `94 console, '99 Dodge Neon Spoiler, '94 XR2 Sideskirts Bumpers and taillights, Fresh Basecoat-Clearcoat Cardinal Red (Jul2014), vj11/vj14 hybrid, manual boost CTL.

SHOwn

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Re: Boost Spiking?
« Reply #6 on: February 24, 2017, 11:08:27 PM »

Whoops, yeah, what kind of boost controller? I made my comments based on the simplest manual boost controllers, not a slave setup or electronic.
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R. Powell
'91 XR2, LM 16" Chrome Drifters, White Gauge Faces, Kuhmo 40's, Big Brake UG, 2.5" Mandrel Bent CATback, BMW318 Heated Seats, `94 console, '99 Dodge Neon Spoiler, '94 XR2 Sideskirts Bumpers and taillights, Fresh Basecoat-Clearcoat Cardinal Red (Jul2014), vj11/vj14 hybrid, manual boost CTL.

greywolf27030

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Re: Boost Spiking?
« Reply #7 on: February 25, 2017, 11:32:06 AM »

Spiking is usually an issue for those who open up their exhausts, it changes the pressure drop across the wastegate, and it can't keep up.

I apologize for a little hyjac here, but will a 2 1/4 cat back system cause a problem?

Thanks, Jack Byrd
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Jack Byrd

alldsben

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    • 91 XR2 91 Miata 04 S10 89 Mustang
Re: Boost Spiking?
« Reply #8 on: February 27, 2017, 09:20:32 AM »

im not 100% sure which boost controller it is but i can say i know its not a high quality one. i believe it is either a problem with a line somewhere in it kinked or that my boost controller needed me to use some adapters to make the hose small enough to go onto the controller itself. i now have an fmic installed but have not had any time to drive it yet beyond just to test if it leaks at all. will trouble shoot a bit more in the upcoming days
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Gaz

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Re: Boost Spiking?
« Reply #9 on: February 27, 2017, 12:58:22 PM »

Spiking is usually an issue for those who open up their exhausts, it changes the pressure drop across the wastegate, and it can't keep up.

I apologize for a little hyjac here, but will a 2 1/4 cat back system cause a problem?

Thanks, Jack Byrd

Yep.
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alldsben

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    • 91 XR2 91 Miata 04 S10 89 Mustang
Re: Boost Spiking?
« Reply #10 on: February 27, 2017, 09:37:32 PM »

I have yet to trouble shoot it but im going to try just taking out the mbc for now with my intercooler and cone filter on. But i was also wondering how bad would it spike if i went with a full 2 1/4 turbo back but still put in a cat and muffler
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Rocketman

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Re: Boost Spiking?
« Reply #11 on: February 27, 2017, 10:15:27 PM »

It's hard to say. There's a tremendous number of variables there.
Some folks with moderate setups only have issues when it's real cold out, and the turbo is running at a higher efficiency.

Do your troubleshooting - see if the problem persists.

I will recommend investing the time to port the wastegate - its extra time and effort but also insurance against out of control boost.
If you're opening everything up (intake/exhaust), it will be necessary at some point.
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1.8L Turbo All Wheel Drive Capri... the "GTXR2"


SHOwn

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Re: Boost Spiking?
« Reply #12 on: February 27, 2017, 10:33:53 PM »

Hmmm, bigger throat, bigger exhaust, seems like the delicate balance will be disrupted. i think you will probably need the waste gate ported. I went 2-1/2" cat back as my only mod for a few years and my boost would creep in cold weather. So when my turbo died I went all vj11 hybrid and ported the gate to 0.87" and said goodbye to spikes and turbo lag with the hybrid. Nice powerband even though I still have the stock intake otherwise. You don't have to go hybrid, but the bigger exhaust usually bothers the waste gate. If you are not planning to port the waste gate I would strongly suggest your exhaust stay under 2-1/2". I thought I could get away with it but it eventually got me.
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R. Powell
'91 XR2, LM 16" Chrome Drifters, White Gauge Faces, Kuhmo 40's, Big Brake UG, 2.5" Mandrel Bent CATback, BMW318 Heated Seats, `94 console, '99 Dodge Neon Spoiler, '94 XR2 Sideskirts Bumpers and taillights, Fresh Basecoat-Clearcoat Cardinal Red (Jul2014), vj11/vj14 hybrid, manual boost CTL.

greywolf27030

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Re: Boost Spiking?
« Reply #13 on: February 28, 2017, 05:01:12 PM »

Pleading ignorance here.  XR2 has a factory wastegate?

Jack Byrd
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Jack Byrd

SHOwn

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Re: Boost Spiking?
« Reply #14 on: February 28, 2017, 06:05:53 PM »

Yeah, it's not like an aftermarket one that would mount in an exhaust pipe, it's integrated in the turbo housing casting with a cast iron cover plate.


« Last Edit: February 01, 2018, 09:53:05 PM by SHOwn »
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R. Powell
'91 XR2, LM 16" Chrome Drifters, White Gauge Faces, Kuhmo 40's, Big Brake UG, 2.5" Mandrel Bent CATback, BMW318 Heated Seats, `94 console, '99 Dodge Neon Spoiler, '94 XR2 Sideskirts Bumpers and taillights, Fresh Basecoat-Clearcoat Cardinal Red (Jul2014), vj11/vj14 hybrid, manual boost CTL.
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