Low boost R18 turbo?

[Renault17]

Hi Guys,
my r18 turbo has been pulled out of storage recently- to find that boost has dropped to around 6psi max. and it was set at 12-14psi before it was put in storage.

Through a process of elimination I have replaced the wastegate actuator- with a brand new item. I also removed the blow-off valve I had on there as it also seemed to be opening during acceleration- not just when the throttle was closed - like it should...

The pipes to and from the intercooler, turbo and carb have all been tightened using a ratchet- so there are no leaks there. The intercooler is strapped as well to prevent it blowing it's plastic end tanks apart too.

I did have a boost adjustment system- a pressure regulator from a compressor- but I removed that in case that was too blame- but it made no difference.

I have adjusted the rod on the wastegate fully- and it has taken it from 6psi to 9psi, however in the past this alone would have taken it 'off the clock' on the boost gauge, but not any more?! (the new wastegate actuator is the same rating as the original unit)

The turbo is fine- it has been checked out by professionals, and if you remove the wastegate line it will boost too infinity- showing that the turbo can still do 'it'!

I just drove a mates fuego turbo on Friday, and his had more boost in the lower gears than mine did, but mine was stronger up high.

Any thoughts on where I am losing this boost? :disappr: I want to get it running properly at normal boost levels then get it dynoed and tuned to make sure it isn't leaning out at all- or detonating... but there isn't much point when I can't get it back to even factory specs..

Cheers Ben

 

[Gus]

Few thoughts

If pulling the wastegate hose makes it "boost to infinity", I guess you can be pretty sure it's the wastegate - not BOV or a leak, right?

Are there any moving wastegate parts you didn't replace? Springs, etc?

... and are you sure it's not your boost gauge that's broken ?

 

[Renault17]

Hey Gus,

the wastegate actuator is brand new as stated- the only other thought was that the wastegate valve - in the turbo- may have cracks in it- they are prone to it- and it could be leaking boost around the wastegate 'valve' seal.
There are really no other moving parts to the wastegate that can be (easily) replaced.
Although it would have to be a pretty huge crack to leak this much boost??!

The boost gauge is reliable- I bought a new one from the shop and tested it against the old one and it's about 0.5psi difference..
Thanks, any more thoughts?

Ben

 

[Craig]

Check all of your pipes again. I had a minor split that couldnt be seen in one hose on my 5 GT Turbo.

 

[Renault17]

Hey Craig,
aside from the intake- pipe to the turbo and outlet- pipe to the intercooler were there any others that gave you grief?
Cheers Ben

 

[Craig]

Hi Ben

Sorry.. I cant remember it exactly (and I dont have the manual with me now), but is there one that somehow links to a fuel cutoff/return valve? I have a memory that there was one going down near the firewall that gave me hell trying to work out why once the car reached a certain boost itd almost die. The reason was a split hose going towards this valve. The car was continuously sending fuel back to the tank when at that level of boost it should have been forced into the carburettor.

One thing I also had was a problem in the pipe that has a restrictor in it. I think it was just blocked or the restrictor had collapsed.

 

[Renault17]

Hi Craig,
on the 18 turbo it has the ignition cutout switch- so that if you overboost it cuts the feed to the ignition. Mine is faulty- it cuts out at 6psi, and I have replaced it with a second hand one only to have it do the same thing

Which could point to it being something else- in that it didn't solve the problem-but I am buggered if I know what?!

On the fuelling side - it has a rising rate pressure regulator- I will check all the
security of these lines but I'd be surprised if they were doing anything...

What line of yours had a restrictor in it? The only one I have found is the return oil breather which enters the air stream just before the turbo- is this the one you are referring to?


Thanks for your tips, as I am keen to get the old girl going as it can/should...

Cheers Ben

ps I know of a 5 gordini for sale in NZ prepped for racing in targa if anyone is interested....

 

[Craig]

I turned off the overboost switch and put in an in-car controller.

Yes, sorry.. the restrictor was the air breather hose. Confused here . Caused all wonders of problems at one stage but not what you have.

 

[Renault17]

Hi craig,
yeah I too have added an adjustable boost feature to my machine as well. I added a blowoff valve too. I haven't found any major leaks aside from noticing blow-by? on the intercooler. Those plastic end tanks were never a good idea- despite being strapped I don't think it is 100%. I have another intercooler from another 18 turbo and I was going to get the two made into one. Other than the intercooler I can't see anything else that would make it leak though....

Cheers Ben