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998 Turbo Not Getting Boost Till 4500Rpm


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#1 tim bennett

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Posted 10 April 2017 - 01:56 PM

Hi all after a bit of advice. I have a 998 with Renault 5 t2 turbo on a home made mirage style manifold and an escort intercooler. Turbo was rebuilt by me using an eBay rebuild kit and the whole lot has only really done test drive miles since being fitted back in the vehicle. The problem I'm having is there is no boost before 4500rpm and doesn't get full boost until 5500rpmish. I've had the turbo back off to inspect and couldn't really see anything wrong so I made up some dividers to go in the end of the manifold to direct the gas straight into the turbo but this has made no difference. I wonder if I have made the manifold too large bore, I used 1 1/2" stainless.
Sorry for the lengthy description.
Cheers Tim

#2 mini13

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Posted 10 April 2017 - 05:35 PM

Is the engine under load?

Also check for an AR number on the turbine housing, somthing like .36 or
.42

#3 Turbo Phil

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Posted 10 April 2017 - 06:33 PM

The manifold is a little on the big side, but I'd still expect boost below the rpm your getting boost.
As Joe said, are you driving it & not just revving it up stationary ?
Are you sure it's the standard Renault 5 spec & not some aftermarket hybrid etc. ?

Phil.

#4 Mervyn

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Posted 10 April 2017 - 08:07 PM

Is the wastegate free to move and closing properly

Merv

#5 tim bennett

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Posted 10 April 2017 - 08:33 PM

Yeah I have been trying it properly on the road. Waste gate is fine. I'll have another look at the numbers on the housing as I can't remember what they are off the top of my head. It did have a new turbine wheel/shaft and compressor wheel which was supplied by the company that balanced it all.
Cheers Tim

#6 coopdog

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Posted 10 April 2017 - 08:48 PM

Just so you know my t2 on a mirage manifold with my metro cam and worked head boosts with 7psi at around 3000-3500rpm

What cam are you using?

Edited by coopdog, 10 April 2017 - 08:49 PM.


#7 tim bennett

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Posted 10 April 2017 - 08:57 PM

I've got a Kent 266 in it
Tim.

#8 mini13

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Posted 11 April 2017 - 08:50 AM

hmm,

 

ok, knt 266 is probably a bit hot, I think that will be contributing, I would be looking at a Kent 500 or a standard metro cam. also do you know what the cam is timed at? if its a bit retarded that might not be helping. also 1.5 rockers will not help if they are fitted

 

also somtimes with turbines replacements are larger if stock is an issue, on the metro T3 the 0.28 AR is not available sothey use the 0.36 from the RS turbo.


Edited by mini13, 11 April 2017 - 08:50 AM.


#9 tim bennett

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Posted 11 April 2017 - 09:07 AM

The cam is timed in at the Kent recommendations I think it's something like 108 degrees but can't remember exactly as it was quite a while ago i built the engine. I'm going to see if I can get the turbo back off today and give it a closer inspection.

#10 Steve220

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Posted 12 April 2017 - 09:54 AM

What preload do you have on the actuator?

#11 tim bennett

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Posted 12 April 2017 - 08:03 PM

The actuators set to roughly 10psi. I tried it again today bypassing the intercooler/pipework and very gingerly took it up the road and it did see things improve slightly, I was starting to see boost at around 3500. Not sure if I've really proved anything by doing that though. Haven't had a chance to get the turbo off yet Friday is looking like the best bet.

#12 Steve220

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Posted 14 April 2017 - 07:46 PM

The actuators set to roughly 10psi. I tried it again today bypassing the intercooler/pipework and very gingerly took it up the road and it did see things improve slightly, I was starting to see boost at around 3500. Not sure if I've really proved anything by doing that though. Haven't had a chance to get the turbo off yet Friday is looking like the best bet.


Set to, designed for, preloaded to - all different. What if there isn't enough preload on the spring then it will begin to open early but still hold your ideal boost by the turbo working much harder that it should. May not be the issue, but start basic and work backwards.

#13 tim bennett

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Posted 15 April 2017 - 02:11 PM

Played around with the actuator a little today and it has seemed to make a bit of a difference. Sorry if this seems like a stupid question but what would be the correct way to set the preload on the actuator?
Thanks for all the advice guys, it's really appreciated.

#14 mini13

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Posted 15 April 2017 - 02:52 PM

Half a hole of tension?

#15 Steve220

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Posted 15 April 2017 - 03:04 PM

Half a hole of tension?


Spot on chap!




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