Low Boost when hot

[Turbox]

Hi

I'm new to the forum and fairly new to the R5... Always wanted one and finally bought one nearly 12 months ago.

My knowledge is not great regarding car mechanics but I am trying to learn; hoping to get some advice from the kind folks on here.

Previous owners have done some work to the car; paperwork seems to suggest a t2/t25 hybrid turbo albeit this was a long time ago so could have been changed since. It has a up rated inter cooler and in car boost control, up rated air filter and that's as far as I can tell. Oh also has a dump valve.

With the boost turned up a bit it goes like stink and easily reaches the end of the standard boost gauge. The boost however seems to perform intermittently only reaching half boost sometimes and I have noticed this seems to be when the engine is hot; say just over the halfway mark on the temperature gauge. If I take it easy and let the temperature drop a bit the full boost is back with a vengeance.

Can anyone advise on what's going on, is the turbo on the way out? I don't seem to be getting any smoke.

Also when the engine is hot I seem to struggle getting into first and second gear; related?

Sorry for the long first post

[francob80]

Hi mate and welcome.

The first thing I would suggest doing if you haven't already got one is to buy and fit an AFR gauge so you can see what your fueling is like. It is impossible to tune a carb for different boost settings when using an in car boost controller. You could well be running very rich or very lean without actually knowing, running too lean at your higher boost level could mean issues with det causing hg failure, cracked liners etc etc. It is better to be safe than sorry.

Secondly, in regards to your boost issue I would suggest checking all of the boost pipes to make sure you haven't got any leaks. It might also be worth checking your actuator as could well be weak and causing issues. Also check your dump valve (most people tend to remove them these days)

Oh, i'd also think about fitting a boost gauge too so you can actually confirm what boost you are running.

I hope that helps.

[Turbox]

Thanks for your help.

Any recommendations of a good AFR gauge, are they easy to install and how do they work? Same questions for a boost gauge.

I want the car to look original so any ideas where the gauges could go; I don't want any more holes in the dash (already got the in car controller - by previous owner).

I have previously checked pipes for leaks as best I could; seems ok but hard to say for sure.

How do I check for a weak actuator?

I have a feeling it could be the dump valve; do these things "dump/leak" too early when they are faulty?? Why would the temperature effect this?

How do I remove the dump valve to test? I quite like the childish psst noises so would probably replace if the current one is faulty.

Sorry about the amount of questions .... a lot to learn. Thanks again.

[tubbyG]

As already stated an afr gauge is essential. I like many others here use the aem uego. They can be bought from efiparts. Co.uk or eBay.

They are fairly easy to install and also don't require any maintenance or recalibration like some. They only need a 12v supply and a ground to operate. A lambda sensor is needed somewhere in the exhaust downpipe. If you can't weld yourself then and local exhaust place should be able to attach the threaded bung on for you for fitment.

I use a gauge pod attached to the A-pillar mounting points for my gauges -afr/boost & oil pressure. A member on here called Johnny5 makes them. They are excellent quality and match the interior plastics very well.

If removing the dump valve you need to blank off where it was mounted and remove it's vacuum pipes also - it should be T'd into the AEI vacuum port in the scuttle area if done correctly.

[francob80]

hi there,

I have one of these for AFR gauge - http://www.efi-parts.co.uk/index.php?productID=204

and one of these for boost - http://www.aemelectronics.com/?q=pro...display-gauges

Agreed with everything Tubby says;

[francob80]

Here is a pic of my pod.

[francob80]

Not sure how heat would effect boost, perhaps worth checking ignition parts too whilst you are at it. Plugs, leads, dizzy and rotor to start.

Could also be your dodgy boost controller causing issues with boost. My advice would be to remove it and just set up for a particular boost level you are happy with and can run safely given your spec.

[Turbox]

Thanks for your replies; appreciate the advice.

Sounds like I have a bit of work to do.

I think the dump valve will have to come off at least temporarily to test if that is the causing problems. Am I right that I just remove the dump valve and thin blue pipe (see pic below)and cap off both. Any suggestions how to cap these off?

Also as suggested I think the in car boost control should be removed but how do I do this? (see pic) There is an "adjustor" with two screw heads, out of the bottom of which a red pipe goes back into the car. Can I just remove this red pipe or cap it and set the boost with the screws? How do these screws work??

Also sounds like a AFR gauge and boost gauge is wise.


]

[francob80]

You can buy blanking plugs to fill in the space left by the dump valve, they aren't much - £10 perhaps. Something like this but make sure you get the right size - http://www.ebay.co.uk/itm/like/33169...f14=122&ff19=0

You can remove the double screw valve and just replace the pipes that run to the actuator, you will then be running standard boost based on the preload of the actuator. I think from memory it's about 7/8 psi.

After you have purchased an AFR/boost gauge you could think about fitting a new bleed valve or adjusting actuator pre load to add in more boost. At least then you can monitor your fuelling/boost pressure to make sure you are safe.

[Turbox]

Thanks.

I'm going to do exactly as you suggest. I'll let you know how it goes...

[Turbox]

Quick up date.

I have removed the dump valve and that has solved the low boost problem; there is nothing obviously wrong with the DV that I can see but it was definitely causing the problem. Performance is much improved.

Need a AFR gauge and boost gauge now; they are more expensive than I'd hoped. Looks like I am looking at over £300 for the pair unless anyone know of a good quality cheaper alternative?

[francob80]

There are a few alternatives for boost and AFR gauges mate, just Google around or check on eBay. You may be able to find something second hand.

The likes of AEM/Innovate and well known brands and for the most part are good products. Stack do some good gauges too.

They are definitely worth investing in though if you are planning on messing about with boost/fuelling etc.

I've not ran a DV for years but if memory serves the diaphragms split and the springs become weak. Best to now run one, you'll still get some nice waste gate chatter.

[Trevhib]