Wednesday, March 01, 2006

Blow off valves (BOV) for Ghibli

About a year ago I installed a pair of blow off valves on the Ghibli. I have an MY92 Ghibli with a 2.0l bi-turbo engine that did not come with recirculating type blow off valves that were fitted to the later MY94 cars. Therefore, every time I changed gear, the turbos would stall as the pressure on the inlet side of the engine backed down to the compressors.

This effectively increased the spool up time when accellerating after each gear change, making the car feel momentarily sluggish. But worse than this, it was putting unnecessary wear and tear on the turbos as they were constantly being accellerated and decellerated, which effectively decreased the longevity of the turbos.

To remedy this problem, I got help from the guys at Forge motorsport in the UK. After measuring the dimensions of the aluminium intake pipes prior to the throttle body, I asked the guys at Forge if they could weld the blow off valves directly onto some new pipe sections. These were then direct replacements for the existing pipes.

The location of these valves is pretty good, since they're located close to the throttle body, which means that they bleed off pressure pretty quickly without the entire inlet system pressuring up. The control line for the two blow off valves is teed together before connecting to the back of the plenum chamber; Jorrit at Auto Forza drilled a hole, tapped it and installed a push fit connector on the back of the plenum chamber for me. The control lines are blue in the picture above, but I've since replaced them with black hoses and fed them beneath the plenum chamber so that they now look like they were fitted by Maserati.

In action, the valves work very well. The car feels more lively when driving hard and feels like it's more poised and ready to go when accelerating hard through the gears. And of course, it makes a great sound as the valves vent off into the engine bay with each gear change. It's not too loud though; since I have two valves fitted, the air is not rushing out with as much vigour as it would with just a single valve. It's still loud enough to scare a few people walking in the street though.

I'd definitely recommend anyone with a pre MY94 Ghibli with no factory fitted blow out valves fitting these valves. Posted by Picasa


Nick said...

Thanks for all the info Johnny, first mailed Forge but then saw that Biesheuvel Motorsport in Breda also could order the parts from Forge, and this was the cheaper option, despite the pound/euro currency difference. Installed it myself (wasn't that difficult), I split the existing vacuum hose (so no hole drilling was necessary, got this info from Enrico's Ghibli website) and it works perfectly! Looks great too. Thanks again for placing the info.


Jonny said...

Hi Nick!

Thanks for letting me know... I was wondering how you'd got on! Rica in Wateringen also stock Forge stuff... there's a few places in the Netherlands selling them.

Did you tee into the vacuum hose on the fuel pressure regulator? If so, it works fine, but really you should leave this hose alone since it's quite critical and you should limit the leak paths on it.

Glad it all worked out... it's a good modification. Can you send me a picture to post on the blog?

Regards... Jonny.