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- Thread starter AndyMinto
- Start date
zpuppy
Well-Known Forum User
Hi Andy ! Hard to tell from the pic but it could be 3/8 pipe ,,, best idea is to try your relief valve on it and if you find it's no good, then a thread pitch gauge set can be had for about 20 quid from RS or others like that 
It will surprise you how often you use it once you have it ! BTW,,easy to buy adapters to step up and down to what you need as well 
It will surprise you how often you use it once you have it ! BTW,,easy to buy adapters to step up and down to what you need as well 
AndyMinto
Inactive
Hi,
Well the Moroso vacuum relief valve arrived at the weekend so I took out the blanking plug only to find it is 1/2". With a plumbing compression joint and a 3/8" NPT tap I was able to make an adapter. The relief valve is now fitted and as it is adjustable I am experimenting.
It has 4 shims inside and with all 4 shims on it made no difference. When shifting from full boost of about 6psi to shut off it was pulling nearly 30" of mercury as a vacuum and pulling oil from the centre turbo bearing into the inlet manifold and out the exhaust as a nasty blue puff of smoke.
3 shims made the max vacuum equal 24" of mercury and no oil smoke!
2 shims seems to have reduced the amount of vacuum too much but has almost eliminated any turbo lag as it shifts to positive boost easily (something I had not counted on). I'll get some pictures up and let you know what I settle on after a few days of running.
Well the Moroso vacuum relief valve arrived at the weekend so I took out the blanking plug only to find it is 1/2". With a plumbing compression joint and a 3/8" NPT tap I was able to make an adapter. The relief valve is now fitted and as it is adjustable I am experimenting.
It has 4 shims inside and with all 4 shims on it made no difference. When shifting from full boost of about 6psi to shut off it was pulling nearly 30" of mercury as a vacuum and pulling oil from the centre turbo bearing into the inlet manifold and out the exhaust as a nasty blue puff of smoke.
3 shims made the max vacuum equal 24" of mercury and no oil smoke!
2 shims seems to have reduced the amount of vacuum too much but has almost eliminated any turbo lag as it shifts to positive boost easily (something I had not counted on). I'll get some pictures up and let you know what I settle on after a few days of running.
AndyMinto
Inactive
Well, I've settled on three shims and evrything seems fine. I may be imagining things but the car seems to be smoother and pull stronger. I'm now keeping an eye on the MPG and oil consumption but it is so responsive that I keep wanting to put my foot down! I'll report back in time but so far this seems like a successful mod for a Janspeed Turbo conversion.
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Mr.G
Club Member
Andy what have you done with the Janspeed Vacuum relief valve have you blocked it off? What boost pressure are you running now? Have you checked to see what your Air Fuel Ratios are on boost, you need to keep a close eye on them as you will probably require more fuel to avoid detonation.
AndyMinto
Inactive
I did not realise that the Janspeed conversion had a vacuum relief valve. I know it has a blow off valve to prevent the pressure getting too high and I have not touched this. Max boost is the same as it was +6 to 7 PSI. What I have done is to prevent the vacuum getting too high (or should that be low) and pulling oil in. I have not checked the air fuel ratio but it is not knocking at all. The air fuel ration should be controlled by the air flow meter and the Vacuum valve does not open under normal driving, this should be the same. The vacuum valve is only opening when the throttle is fully shut and the fuel flow should be minimal then.
If I need to put the blanking plug back, I can as I have not drilled or altered the manifold.
If I need to put the blanking plug back, I can as I have not drilled or altered the manifold.
AndyMinto
Inactive
Thanks, I had a Janspeed conversion in the early eighties and it had the same problem (pulling in oil, I guess from the centre turbo bearing when shutting off fully after running on full boost). That car did not have a pressure/vacuum gauge but this one does. When I saw it was pulling nearly 30" of mercury (that's not far off total vacuum) I thought I'd experiment with a vacuum relief valve. Where I've fitted the valve is right in the centre of the plenum chamber so I might have altered the vorticies and made a difference to the air flow. Also it may be more responsive as I don't have as much vacuum to fill before the engine can breath again and not having all that oil to get rid of must be a good thing and add to the engine's reponse. As I said though, I'll monitor things over the next few weeks.