Overboost?

[Gary Symons]

Hi Guys,

I am after a little advice,

Fitted the FCD yesterday but it hasnt solved the fuel cut problem. I have not fitted the Boost controller yet but I am still geting fuel cut, now at about 14 psi. Do I keep winding out the FCD until i dont get cut?

Why am I getting so much boost from standard? I have read that I may get a little extra with all the induction/exhaust bits fitted but surely not this much.

Help please!!! I am a bit thick still when it comes to turbos :confused:

[Paul Woods]

gary its possible your actuator isnt opening the wastegate,in fact id put money on that.... have you got a compressed air line? take the pipe that goes to the actuator from the turbo and apply a little compressed air (10-15psi would be great!) and you should be able to watch the rod coming out of the actuator move....if it doesnt move then either the actuator diaphragm is split or the wastegate is jammed shut.

Ive heard of some wastegates jamming shut on certain aftermarket downpipes,it could be this thats keeping the gate shut.

Either way something is causing your overboost....if you remove the actuator (2 bolts) from the compressor housing you should be able to manually open the wastegate yourself,if you cant you know its jammed on the decat pipe housing,hope that helps mate,do the compressed air test first tho.

[Gary Symons]

Cheers, top info as usual. Will have a look at it tomorrow.

[Gary Symons]

Many thanks Paul :clap: . Did the airline test and it looked like the actuator was sticking. So took the downpipe off and look what I found. The gate has clearly been catching on the flange, A little action with a grinding wheel should soon sort it. Hopefully back on the road tonight.

http://www.mr2mk1turbo.co.uk/files/wastegate-clash.jpg

[adamh]

is that an xs power downpipe gary?

[adamh]

is that an xs as power downpipe gary?

[Paul Woods]

back o the net! i always do the compressed air test on all decat pipe fitted engines before i start them up just to make sure the gates opening....as you say matey a little grinder action sorts it out.

[Gary Symons]

is that an xs as power downpipe gary?

yes


is that an xs as power downpipe gary?

yes again lol

[Gary Symons]

back o the net! i always do the compressed air test on all decat pipe fitted engines before i start them up just to make sure the gates opening....as you say matey a little grinder action sorts it out.

Back together now, The car is transformed. Jeez its fast now :twisted: . I have still been getting a little fuel cut though, so I have had a play with the fcd and can now get to a peak of about 13psi without any issues.

Dont think I will be upping the boost just yet.

[Gary Symons]

This car is confusing me now :doh: . Just been out on another run and watching the gauge while booting it in 3rd the gauge would jump up to 12psi, sit there for a short while then jump up to 14psi and fuel cut.

Whats going on, has anyone else had fuel cut issues on their motor while on standard unmodifed boost? Looks like its a job for next weekend as I have run out of time again.

All help gratefully recieved.

[Paul Woods]

hmmm sounds like yours is spiking for some reason gary,id be fitting a grainger to that so you can control what boost the actuator sees,that should give you a steady 12psi or whatever you want.

[Gary Symons]

hmmm sounds like yours is spiking for some reason gary,id be fitting a grainger to that so you can control what boost the actuator sees,that should give you a steady 12psi or whatever you want.

Cheers, will have another look at it next weekend. Will have to resist winding the boost up though, its pretty addictive.

Any ideas why it would be spiking?

Anyway my mate stella is calling.....

Once again, thanks for the help.

[Paul Woods]

actuator not opening the wastegate far enough perhaps? could be the wastegate flaps are still catching the decat pipe at a further opening point?

Ive personally never had this on any of xs-powers downpipes but ihave heard of it happening a few times before,and not just with xs-powers,the aussie pipes do it as well.....not sure why only some do it,i think they must all be made slightly differently on whatever jig they use to fab them up.

[Gary Symons]

After a bit of googling, i found this:

http://www.twosrus.com/new/Lower_Frames/Articles/Installation_Instructions/MBCinstructions.PDF#search=%22MR2%20TURBO%20BLEED% 20VALVE%20FITTING%20INSTRUCTIONS%22

When I fit the boost valve should I be disabling the T-VSV as it states here?

Also could a faulty/leaking T-VSV system be causing my problems?

Cheers.

[MegatronUK]

Yep, rip that T-VSV out! :)

All it does is limit your boost by 3-4psi when the engine is cold.

[Gary Symons]

Yep, rip that T-VSV out! :)

All it does is limit your boost by 3-4psi when the engine is cold.

Added to my to do list, :thumbsup:

Many thanks.

[Gary Symons]

The saga continues, today I disabled the TVSV and fitted the MBC. Already have the FCD fitted. As the instructions stated I wound the valve right out to minimise boost but it is still hittng fuel cut at about 14-15psi.

After inspection the actuator is no longer hitting the downpipe and the actuator appears to work when pressure is applied.

What do i try next? new actuator? Could the problem be elsewhere?

Ta

[Paul Woods]

gary how far does the actuator rod move when you apply 10psi to it? i have a ct26 here on the bench i can cross ref the measurement with just to check yours is opening properly.Put a mark of paint on the rod and measure how far it moves when pressure applied and get back to me bud.

If the actuator is seeing anything above 7psi the spring inside will be giving way as its loaded to 7psi,so after that it should be opening the gate.If the gate is opening the turbo cannot produce boost,simple as that.....well i say it cant,ive had an actuator rod come off the gate before so the gate was just flapping about and it would still make 6 psi but no more than that.

Its got to be an actuator or wastegate prob mate

[Gary Symons]

gary how far does the actuator rod move when you apply 10psi to it? i have a ct26 here on the bench i can cross ref the measurement with just to check yours is opening properly.Put a mark of paint on the rod and measure how far it moves when pressure applied and get back to me bud.

If the actuator is seeing anything above 7psi the spring inside will be giving way as its loaded to 7psi,so after that it should be opening the gate.If the gate is opening the turbo cannot produce boost,simple as that.....well i say it cant,ive had an actuator rod come off the gate before so the gate was just flapping about and it would still make 6 psi but no more than that.

Its got to be an actuator or wastegate prob mate

Will pop around to the car and have a measure, will also recheck the boost valve just to make sure it is fully wound out. I take it that you wind it out literally as far as possible while still still having say 10mm of thread engaged in the valve?

will report back later.

[Paul Woods]

yeah wound right out mate,but if you just plumbed the turbo straight to the actuator with no grainger that turbo should only ever make 7psi no matter what and with the t-vsv disabled.

So theres something allowing the turbo to make more pressure,so it all points to actuator or wastegate not opening or not far enough.

[Gary Symons]

right, done some tests. The gauge in the compressor is only calibrated down to multiples of 10psi so the pressures I quote may not be exact.

@ 5psi bar moves 6mm
@ 7psi bar moves 9mm
@ 10psi bar moves 13mm
@ 15psi bar moves 13mm

The wastegate doesnt appear to be sticking as winding the pressure up or down to these figures gets repeatable results.

If that sounds ok then I guess I need to remove the boost controller and see what happens then. ie the 7psi max you quote

also if it a dodgy actuator how easy are they to swap while on the car?

Thanks for your help Paul. Will get some hob-nobs in for JAE next year :hehe: .

[Paul Woods]

thanks gary i will repeat those tests on two different turbos ive got here and compare results,although it does sound like its working right....if its a dodgy actuator its a pig of a job getting the circlip off the wastegate end and putting the new one back on,skinned knuckles time,lets hope its not that.

Yep take the boost controller off,disable the t-vsv (block the actuator pipe thats going to the rear of the engine) actually now i think about it if that pipe had a leak it would mean your actuator wasnt seeing the actual turbo boost and would cause overboost conditions.....possibility there! blank it off at the actuator to eliminate that as a cause,remove boost controller so that the turbo housing is connected straight to the actuator as it is stock and 7psi should be the max you get in any gear.

Oh im upgrading to tunnocks caramel wafers these days :thumbsup:

[Gary Symons]

Oh im upgrading to tunnocks caramel wafers these days :thumbsup:

Is that milk or dark chocloate :hehe:.

Will have another look at the car on friday, one thing is for sure, if it is the actuator I am ripping the turbo off aswell and fitting something better :mrgreen: and brand new :mrgreen: .

Any suggestions? fensport ct26? twosrus ct27?

[Paul Woods]

T78 :toke:

[Gary Symons]

T78 :toke:

and only ?3000+vat for the greddy kit from fensport. think i may get 2 so i have a spare :doh:

Would love to see how it works in a mk1.5 though :twisted: . but i think it is a little out of my price range.

[GaryA]

Originally Posted by Paul Woods

Oh im upgrading to tunnocks caramel wafers these days

:drool: Now ya talking !

[Gary Symons]

Ok guys, this weeks installment (its getting to be a real PITA only being able to work on the car at weekends :banghead: ).

As suggested I removed the MBC and put the pipe back. I have noticed something interesting, as suggested the boost now goes quickly up to 7psi, but then starts climbing as before. I checked the pipes and they all look solid, ie no leaks.

Looks to me like the actuator is operating properly and then possibly starts to leak boost and close again?

Anyway think its coming off tomorrow.

[Paul Woods]

gary where does the other actuator pipe go currently? have you got that one blocked off? it usually goes to the t-vsv under the inlet manifold.

[Gary Symons]

gary where does the other actuator pipe go currently? have you got that one blocked off? it usually goes to the t-vsv under the inlet manifold.

its blocked off with a small length of pipe with a bolt in the end (held on with a jubilee clip)

[Gary Symons]

Think I am getting somewhere with this finally. Stripped the downpipe off AGAIN and fitted the airline to the actuator. Everything operates as it should initially and the gate opens however even with the pressure applied it is really easy to push the gate closed again (why didnt I try this before :blush: ). I guess the exhaust gasses are forcing the gate shut.

Looks like a fooked actuator to me.

One thing is for sure I have a little more knowledge into how these things work because of the problems. Still think I have alot to learn though!

Anyone used the 12psi uprated actuator from fensport? any good?
may still be cheaper than a standard one from mr T.

Would certanly be cheaper than fitting a new uprated turbo, but while it is bits :hmm: not sure what to do at the moment :shrug:

[Gary Symons]

A quick update:

I have done a bit more driving in the Mk1.5 the last week and noticed something interesting.

After all the messing about I have done previously I think I have finally found out the real reason for my boost problems. I cant find the other thred where i talked about this but i suspected I had a dodgy boost gauge that over-read.

The boost gauge is fine, Since I sorted out the timing (it was way off) it now peaks at a very steady 12psi. I dont understand exactly how it works but the engine timing was definately screwing things up.

So my advice to new builds, check your timing first!

Hopefully some vids coming soon :driving:

[David Sleith]

Glad you got it sorted.

[Gary Symons]

Glad you got it sorted.

My fellow road users aren't :driving: :twisted:

[adamh]

what you mean is i fettled my downpipe out for nowt lol . good to hear it smooth, is that with just an mbc?

[Gary Symons]

what you mean is i fettled my downpipe out for nowt lol / good to hear it smooth, is that with just an mbc?

Probably still needed to do that, my wastegate was definately catching.

Stock piping at the mo, if its dry tomorrow may throw the MBC back on and turn it up to 14psi and see what it does.

[adamh]

there was a tiny tiny mark on mine too, i didnt notice any overboost problems yet, so i ground to be safe. I also noticed the xs downpipe bolt holes had a bit of play on the turbo exhaust flange studs..so i biased the pipe over away from the wg flap before tightening

[MegatronUK]

Ah Gary, was it ignition timing or camshaft that you altered? Camshaft timing would definitely have an effect on boost - too long a duration on the exhaust valves and you would find your compressed charge air dissapearing down before firing!

Ignition timing would also have an affect I suppose too :)

Glad you've got it sorted mate!